Bump version numbers for 1.1.5 release.

Always unpack and include latest Tor binaries

See merge request briar/briar!987

.idea/codeStyles/Project.xml

@@ -36,6 +36,9 @@
       <option name="JD_ALIGN_PARAM_COMMENTS" value="false" />
       <option name="JD_ALIGN_EXCEPTION_COMMENTS" value="false" />
     </JavaCodeStyleSettings>
+    <JetCodeStyleSettings>
+      <option name="CODE_STYLE_DEFAULTS" value="KOTLIN_OFFICIAL" />
+    </JetCodeStyleSettings>
     <Objective-C-extensions>
       <file>
         <option name="com.jetbrains.cidr.lang.util.OCDeclarationKind" value="Import" />
@@ -257,5 +260,11 @@
         </rules>
       </arrangement>
     </codeStyleSettings>
+    <codeStyleSettings language="kotlin">
+      <option name="CODE_STYLE_DEFAULTS" value="KOTLIN_OFFICIAL" />
+      <option name="PARAMETER_ANNOTATION_WRAP" value="1" />
+      <option name="VARIABLE_ANNOTATION_WRAP" value="1" />
+      <option name="ENUM_CONSTANTS_WRAP" value="1" />
+    </codeStyleSettings>
   </code_scheme>
 </component>

.idea/runConfigurations/All_in_briar_headless.xml

@@ -0,0 +1,20 @@
+<component name="ProjectRunConfigurationManager">
+  <configuration default="false" name="All in briar-headless" type="AndroidJUnit" factoryName="Android JUnit" nameIsGenerated="true">
+    <module name="briar-headless" />
+    <option name="ALTERNATIVE_JRE_PATH_ENABLED" value="false" />
+    <option name="ALTERNATIVE_JRE_PATH" />
+    <option name="PACKAGE_NAME" value="org.briarproject.briar.headless" />
+    <option name="MAIN_CLASS_NAME" value="" />
+    <option name="METHOD_NAME" value="" />
+    <option name="TEST_OBJECT" value="package" />
+    <option name="VM_PARAMETERS" value="" />
+    <option name="PARAMETERS" value="" />
+    <option name="WORKING_DIRECTORY" value="file://$PROJECT_DIR$/briar-headless" />
+    <option name="PASS_PARENT_ENVS" value="true" />
+    <option name="TEST_SEARCH_SCOPE">
+      <value defaultName="singleModule" />
+    </option>
+    <patterns />
+    <method />
+  </configuration>
+</component>

.idea/runConfigurations/All_tests.xml

@@ -24,6 +24,7 @@
       <option name="RunConfigurationTask" enabled="true" run_configuration_name="All tests in bramble-android" run_configuration_type="AndroidJUnit" />
       <option name="RunConfigurationTask" enabled="true" run_configuration_name="All tests in bramble-java" run_configuration_type="AndroidJUnit" />
       <option name="RunConfigurationTask" enabled="true" run_configuration_name="All tests in briar-core" run_configuration_type="AndroidJUnit" />
+      <option name="RunConfigurationTask" enabled="true" run_configuration_name="All in briar-headless" run_configuration_type="AndroidJUnit" />
     </method>
   </configuration>
-</component>
+</component>

.idea/runConfigurations/All_tests_in_bramble_android.xml

@@ -1,6 +1,5 @@
 <component name="ProjectRunConfigurationManager">
   <configuration default="false" name="All tests in bramble-android" type="AndroidJUnit" factoryName="Android JUnit">
-    <extension name="coverage" enabled="false" merge="false" sample_coverage="true" runner="idea" />
     <module name="bramble-android" />
     <option name="ALTERNATIVE_JRE_PATH_ENABLED" value="false" />
     <option name="ALTERNATIVE_JRE_PATH" />
@@ -11,12 +10,10 @@
     <option name="VM_PARAMETERS" value="-ea" />
     <option name="PARAMETERS" value="" />
     <option name="WORKING_DIRECTORY" value="file://$PROJECT_DIR$/bramble-android" />
-    <option name="ENV_VARIABLES" />
     <option name="PASS_PARENT_ENVS" value="true" />
     <option name="TEST_SEARCH_SCOPE">
       <value defaultName="singleModule" />
     </option>
-    <envs />
     <patterns />
     <method />
   </configuration>

.idea/runConfigurations/All_tests_in_bramble_api.xml

@@ -1,6 +1,5 @@
 <component name="ProjectRunConfigurationManager">
   <configuration default="false" name="All tests in bramble-api" type="AndroidJUnit" factoryName="Android JUnit">
-    <extension name="coverage" enabled="false" merge="false" sample_coverage="true" runner="idea" />
     <module name="bramble-api" />
     <option name="ALTERNATIVE_JRE_PATH_ENABLED" value="false" />
     <option name="ALTERNATIVE_JRE_PATH" />
@@ -11,12 +10,10 @@
     <option name="VM_PARAMETERS" value="-ea" />
     <option name="PARAMETERS" value="" />
     <option name="WORKING_DIRECTORY" value="file://$PROJECT_DIR$/bramble-api" />
-    <option name="ENV_VARIABLES" />
     <option name="PASS_PARENT_ENVS" value="true" />
     <option name="TEST_SEARCH_SCOPE">
       <value defaultName="singleModule" />
     </option>
-    <envs />
     <patterns />
     <method />
   </configuration>

.idea/runConfigurations/All_tests_in_bramble_core.xml

@@ -1,6 +1,5 @@
 <component name="ProjectRunConfigurationManager">
   <configuration default="false" name="All tests in bramble-core" type="AndroidJUnit" factoryName="Android JUnit">
-    <extension name="coverage" enabled="false" merge="false" sample_coverage="true" runner="idea" />
     <module name="bramble-core" />
     <option name="ALTERNATIVE_JRE_PATH_ENABLED" value="false" />
     <option name="ALTERNATIVE_JRE_PATH" />
@@ -11,12 +10,10 @@
     <option name="VM_PARAMETERS" value="-ea" />
     <option name="PARAMETERS" value="" />
     <option name="WORKING_DIRECTORY" value="file://$PROJECT_DIR$/bramble-core" />
-    <option name="ENV_VARIABLES" />
     <option name="PASS_PARENT_ENVS" value="true" />
     <option name="TEST_SEARCH_SCOPE">
       <value defaultName="singleModule" />
     </option>
-    <envs />
     <patterns />
     <method />
   </configuration>

.idea/runConfigurations/All_tests_in_bramble_java.xml

@@ -1,6 +1,5 @@
 <component name="ProjectRunConfigurationManager">
   <configuration default="false" name="All tests in bramble-java" type="AndroidJUnit" factoryName="Android JUnit">
-    <extension name="coverage" enabled="false" merge="false" sample_coverage="true" runner="idea" />
     <module name="bramble-java" />
     <option name="ALTERNATIVE_JRE_PATH_ENABLED" value="false" />
     <option name="ALTERNATIVE_JRE_PATH" />
@@ -11,12 +10,10 @@
     <option name="VM_PARAMETERS" value="-ea -Djava.library.path=libs" />
     <option name="PARAMETERS" value="" />
     <option name="WORKING_DIRECTORY" value="file://$PROJECT_DIR$/bramble-java" />
-    <option name="ENV_VARIABLES" />
     <option name="PASS_PARENT_ENVS" value="true" />
     <option name="TEST_SEARCH_SCOPE">
       <value defaultName="singleModule" />
     </option>
-    <envs />
     <patterns />
     <method />
   </configuration>

.idea/runConfigurations/All_tests_in_briar_android.xml

@@ -1,6 +1,5 @@
 <component name="ProjectRunConfigurationManager">
   <configuration default="false" name="All tests in briar-android" type="AndroidJUnit" factoryName="Android JUnit">
-    <extension name="coverage" enabled="false" merge="false" sample_coverage="true" runner="idea" />
     <module name="briar-android" />
     <option name="ALTERNATIVE_JRE_PATH_ENABLED" value="false" />
     <option name="ALTERNATIVE_JRE_PATH" />
@@ -11,12 +10,10 @@
     <option name="VM_PARAMETERS" value="-ea" />
     <option name="PARAMETERS" value="" />
     <option name="WORKING_DIRECTORY" value="file://$PROJECT_DIR$/briar-android" />
-    <option name="ENV_VARIABLES" />
     <option name="PASS_PARENT_ENVS" value="true" />
     <option name="TEST_SEARCH_SCOPE">
       <value defaultName="singleModule" />
     </option>
-    <envs />
     <patterns />
     <method />
   </configuration>

.idea/runConfigurations/All_tests_in_briar_core.xml

@@ -1,6 +1,5 @@
 <component name="ProjectRunConfigurationManager">
   <configuration default="false" name="All tests in briar-core" type="AndroidJUnit" factoryName="Android JUnit">
-    <extension name="coverage" enabled="false" merge="false" sample_coverage="true" runner="idea" />
     <module name="briar-core" />
     <option name="ALTERNATIVE_JRE_PATH_ENABLED" value="false" />
     <option name="ALTERNATIVE_JRE_PATH" />
@@ -11,12 +10,10 @@
     <option name="VM_PARAMETERS" value="-ea" />
     <option name="PARAMETERS" value="" />
     <option name="WORKING_DIRECTORY" value="file://$PROJECT_DIR$/briar-core" />
-    <option name="ENV_VARIABLES" />
     <option name="PASS_PARENT_ENVS" value="true" />
     <option name="TEST_SEARCH_SCOPE">
       <value defaultName="singleModule" />
     </option>
-    <envs />
     <patterns />
     <method />
   </configuration>

.idea/runConfigurations/H2_Performance_Test.xml

@@ -1,6 +1,5 @@
 <component name="ProjectRunConfigurationManager">
   <configuration default="false" name="H2 Performance Test" type="AndroidJUnit" factoryName="Android JUnit">
-    <extension name="coverage" enabled="false" merge="false" sample_coverage="true" runner="idea" />
     <module name="bramble-core" />
     <option name="ALTERNATIVE_JRE_PATH_ENABLED" value="false" />
     <option name="ALTERNATIVE_JRE_PATH" />
@@ -11,12 +10,10 @@
     <option name="VM_PARAMETERS" value="-ea" />
     <option name="PARAMETERS" value="" />
     <option name="WORKING_DIRECTORY" value="" />
-    <option name="ENV_VARIABLES" />
     <option name="PASS_PARENT_ENVS" value="true" />
     <option name="TEST_SEARCH_SCOPE">
       <value defaultName="singleModule" />
     </option>
-    <envs />
     <patterns />
     <method />
   </configuration>

.idea/runConfigurations/HyperSQL_Performance_Test.xml

@@ -1,6 +1,5 @@
 <component name="ProjectRunConfigurationManager">
   <configuration default="false" name="HyperSQL Performance Test" type="AndroidJUnit" factoryName="Android JUnit">
-    <extension name="coverage" enabled="false" merge="false" sample_coverage="true" runner="idea" />
     <module name="bramble-core" />
     <option name="ALTERNATIVE_JRE_PATH_ENABLED" value="false" />
     <option name="ALTERNATIVE_JRE_PATH" />
@@ -11,12 +10,10 @@
     <option name="VM_PARAMETERS" value="-ea" />
     <option name="PARAMETERS" value="" />
     <option name="WORKING_DIRECTORY" value="" />
-    <option name="ENV_VARIABLES" />
     <option name="PASS_PARENT_ENVS" value="true" />
     <option name="TEST_SEARCH_SCOPE">
       <value defaultName="singleModule" />
     </option>
-    <envs />
     <patterns />
     <method />
   </configuration>

.idea/runConfigurations/briar_headless.xml

@@ -0,0 +1,17 @@
+<component name="ProjectRunConfigurationManager">
+  <configuration default="false" name="briar-headless" type="JetRunConfigurationType" factoryName="Kotlin" singleton="true">
+    <extension name="coverage" enabled="false" merge="false" sample_coverage="true" runner="idea" />
+    <option name="VM_PARAMETERS" value="" />
+    <option name="PROGRAM_PARAMETERS" value="-v" />
+    <option name="ALTERNATIVE_JRE_PATH_ENABLED" value="false" />
+    <option name="ALTERNATIVE_JRE_PATH" />
+    <option name="PASS_PARENT_ENVS" value="true" />
+    <option name="MAIN_CLASS_NAME" value="org.briarproject.briar.headless.MainKt" />
+    <option name="WORKING_DIRECTORY" value="" />
+    <module name="briar-headless" />
+    <envs />
+    <method>
+      <option name="Gradle.BeforeRunTask" enabled="true" tasks="jar" externalProjectPath="$PROJECT_DIR$/briar-headless" vmOptions="" scriptParameters="" />
+    </method>
+  </configuration>
+</component>

bramble-android/build.gradle

@@ -1,16 +1,18 @@
+import com.android.build.gradle.tasks.MergeResources
+
 apply plugin: 'com.android.library'
 apply plugin: 'witness'
 apply from: 'witness.gradle'
 
 android {
-	compileSdkVersion 27
-	buildToolsVersion '27.0.3'
+	compileSdkVersion 28
+	buildToolsVersion '28.0.3'
 
 	defaultConfig {
 		minSdkVersion 14
 		targetSdkVersion 26
-		versionCode 10101
-		versionName "1.1.1"
+		versionCode 10105
+		versionName "1.1.5"
 		consumerProguardFiles 'proguard-rules.txt'
 
 		testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
@@ -28,9 +30,10 @@ configurations {
 
 dependencies {
 	implementation project(path: ':bramble-core', configuration: 'default')
-	tor 'org.briarproject:tor-android:0.2.9.16@zip'
+	tor 'org.briarproject:tor-android:0.3.4.8@zip'
+	tor 'org.briarproject:obfs4proxy-android:0.0.7@zip'
 
-	annotationProcessor 'com.google.dagger:dagger-compiler:2.0.2'
+	annotationProcessor 'com.google.dagger:dagger-compiler:2.19'
 
 	compileOnly 'javax.annotation:jsr250-api:1.0'
 
@@ -39,13 +42,29 @@ dependencies {
 	testImplementation "org.jmock:jmock:2.8.2"
 	testImplementation "org.jmock:jmock-junit4:2.8.2"
 	testImplementation "org.jmock:jmock-legacy:2.8.2"
-	testImplementation "org.hamcrest:hamcrest-library:1.3"
-	testImplementation "org.hamcrest:hamcrest-core:1.3"
 }
 
-project.afterEvaluate {
-	copy {
-		from configurations.tor.collect { zipTree(it) }
-		into 'src/main/res/raw'
+def torBinariesDir = 'src/main/res/raw'
+
+task cleanTorBinaries {
+	doLast {
+		delete fileTree(torBinariesDir) { include '*.zip' }
 	}
 }
+
+clean.dependsOn cleanTorBinaries
+
+task unpackTorBinaries {
+	doLast {
+		copy {
+			from configurations.tor.collect { zipTree(it) }
+			into torBinariesDir
+		}
+	}
+	dependsOn cleanTorBinaries
+}
+
+tasks.withType(MergeResources) {
+	inputs.dir torBinariesDir
+	dependsOn unpackTorBinaries
+}

bramble-android/src/main/java/org/briarproject/bramble/BrambleAndroidModule.java

@@ -1,5 +1,6 @@
 package org.briarproject.bramble;
 
+import org.briarproject.bramble.battery.AndroidBatteryModule;
 import org.briarproject.bramble.network.AndroidNetworkModule;
 import org.briarproject.bramble.plugin.tor.CircumventionModule;
 import org.briarproject.bramble.system.AndroidSystemModule;
@@ -7,6 +8,7 @@ import org.briarproject.bramble.system.AndroidSystemModule;
 import dagger.Module;
 
 @Module(includes = {
+		AndroidBatteryModule.class,
 		AndroidNetworkModule.class,
 		AndroidSystemModule.class,
 		CircumventionModule.class

bramble-android/src/main/java/org/briarproject/bramble/battery/AndroidBatteryManager.java

@@ -0,0 +1,84 @@
+package org.briarproject.bramble.battery;
+
+import android.app.Application;
+import android.content.BroadcastReceiver;
+import android.content.Context;
+import android.content.Intent;
+import android.content.IntentFilter;
+
+import org.briarproject.bramble.api.battery.BatteryManager;
+import org.briarproject.bramble.api.battery.event.BatteryEvent;
+import org.briarproject.bramble.api.event.EventBus;
+import org.briarproject.bramble.api.lifecycle.Service;
+
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.logging.Logger;
+
+import javax.inject.Inject;
+
+import static android.content.Intent.ACTION_BATTERY_CHANGED;
+import static android.content.Intent.ACTION_POWER_CONNECTED;
+import static android.content.Intent.ACTION_POWER_DISCONNECTED;
+import static android.os.BatteryManager.BATTERY_STATUS_CHARGING;
+import static android.os.BatteryManager.BATTERY_STATUS_FULL;
+import static android.os.BatteryManager.EXTRA_STATUS;
+import static java.util.logging.Level.INFO;
+import static java.util.logging.Logger.getLogger;
+
+class AndroidBatteryManager implements BatteryManager, Service {
+
+	private static final Logger LOG =
+			getLogger(AndroidBatteryManager.class.getName());
+
+	private final Context appContext;
+	private final EventBus eventBus;
+	private final AtomicBoolean used = new AtomicBoolean(false);
+
+	private volatile BroadcastReceiver batteryReceiver = null;
+
+	@Inject
+	AndroidBatteryManager(Application app, EventBus eventBus) {
+		this.appContext = app.getApplicationContext();
+		this.eventBus = eventBus;
+	}
+
+	@Override
+	public boolean isCharging() {
+		// Get the sticky intent for ACTION_BATTERY_CHANGED
+		IntentFilter filter = new IntentFilter(ACTION_BATTERY_CHANGED);
+		Intent i = appContext.registerReceiver(null, filter);
+		if (i == null) return false;
+		int status = i.getIntExtra(EXTRA_STATUS, -1);
+		return status == BATTERY_STATUS_CHARGING ||
+				status == BATTERY_STATUS_FULL;
+	}
+
+	@Override
+	public void startService() {
+		if (used.getAndSet(true)) throw new IllegalStateException();
+		batteryReceiver = new BatteryReceiver();
+		IntentFilter filter = new IntentFilter();
+		filter.addAction(ACTION_POWER_CONNECTED);
+		filter.addAction(ACTION_POWER_DISCONNECTED);
+		appContext.registerReceiver(batteryReceiver, filter);
+	}
+
+	@Override
+	public void stopService() {
+		if (batteryReceiver != null)
+			appContext.unregisterReceiver(batteryReceiver);
+	}
+
+	private class BatteryReceiver extends BroadcastReceiver {
+
+		@Override
+		public void onReceive(Context ctx, Intent i) {
+			String action = i.getAction();
+			if (LOG.isLoggable(INFO)) LOG.info("Received broadcast " + action);
+			if (ACTION_POWER_CONNECTED.equals(action))
+				eventBus.broadcast(new BatteryEvent(true));
+			else if (ACTION_POWER_DISCONNECTED.equals(action))
+				eventBus.broadcast(new BatteryEvent(false));
+		}
+	}
+}

bramble-android/src/main/java/org/briarproject/bramble/battery/AndroidBatteryModule.java

@@ -0,0 +1,21 @@
+package org.briarproject.bramble.battery;
+
+import org.briarproject.bramble.api.battery.BatteryManager;
+import org.briarproject.bramble.api.lifecycle.LifecycleManager;
+
+import javax.inject.Singleton;
+
+import dagger.Module;
+import dagger.Provides;
+
+@Module
+public class AndroidBatteryModule {
+
+	@Provides
+	@Singleton
+	BatteryManager provideBatteryManager(LifecycleManager lifecycleManager,
+			AndroidBatteryManager batteryManager) {
+		lifecycleManager.registerService(batteryManager);
+		return batteryManager;
+	}
+}

bramble-android/src/main/java/org/briarproject/bramble/plugin/bluetooth/AndroidBluetoothPlugin.java

@@ -16,18 +16,27 @@ import org.briarproject.bramble.api.plugin.PluginException;
 import org.briarproject.bramble.api.plugin.duplex.DuplexPluginCallback;
 import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
 import org.briarproject.bramble.api.system.AndroidExecutor;
+import org.briarproject.bramble.api.system.Clock;
 import org.briarproject.bramble.util.AndroidUtils;
 
 import java.io.Closeable;
 import java.io.IOException;
 import java.security.SecureRandom;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.List;
 import java.util.UUID;
+import java.util.concurrent.BlockingQueue;
 import java.util.concurrent.ExecutionException;
 import java.util.concurrent.Executor;
+import java.util.concurrent.LinkedBlockingQueue;
 import java.util.logging.Logger;
 
 import javax.annotation.Nullable;
 
+import static android.bluetooth.BluetoothAdapter.ACTION_DISCOVERY_FINISHED;
+import static android.bluetooth.BluetoothAdapter.ACTION_DISCOVERY_STARTED;
 import static android.bluetooth.BluetoothAdapter.ACTION_SCAN_MODE_CHANGED;
 import static android.bluetooth.BluetoothAdapter.ACTION_STATE_CHANGED;
 import static android.bluetooth.BluetoothAdapter.EXTRA_SCAN_MODE;
@@ -37,8 +46,13 @@ import static android.bluetooth.BluetoothAdapter.SCAN_MODE_CONNECTABLE_DISCOVERA
 import static android.bluetooth.BluetoothAdapter.SCAN_MODE_NONE;
 import static android.bluetooth.BluetoothAdapter.STATE_OFF;
 import static android.bluetooth.BluetoothAdapter.STATE_ON;
+import static android.bluetooth.BluetoothDevice.ACTION_FOUND;
+import static android.bluetooth.BluetoothDevice.EXTRA_DEVICE;
+import static java.util.concurrent.TimeUnit.MILLISECONDS;
+import static java.util.logging.Level.INFO;
 import static java.util.logging.Level.WARNING;
 import static org.briarproject.bramble.util.LogUtils.logException;
+import static org.briarproject.bramble.util.PrivacyUtils.scrubMacAddress;
 
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
@@ -47,8 +61,11 @@ class AndroidBluetoothPlugin extends BluetoothPlugin<BluetoothServerSocket> {
 	private static final Logger LOG =
 			Logger.getLogger(AndroidBluetoothPlugin.class.getName());
 
+	private static final int MAX_DISCOVERY_MS = 10_000;
+
 	private final AndroidExecutor androidExecutor;
 	private final Context appContext;
+	private final Clock clock;
 
 	private volatile boolean wasEnabledByUs = false;
 	private volatile BluetoothStateReceiver receiver = null;
@@ -58,12 +75,13 @@ class AndroidBluetoothPlugin extends BluetoothPlugin<BluetoothServerSocket> {
 
 	AndroidBluetoothPlugin(BluetoothConnectionLimiter connectionLimiter,
 			Executor ioExecutor, AndroidExecutor androidExecutor,
-			Context appContext, SecureRandom secureRandom, Backoff backoff,
-			DuplexPluginCallback callback, int maxLatency) {
+			Context appContext, SecureRandom secureRandom, Clock clock,
+			Backoff backoff, DuplexPluginCallback callback, int maxLatency) {
 		super(connectionLimiter, ioExecutor, secureRandom, backoff, callback,
 				maxLatency);
 		this.androidExecutor = androidExecutor;
 		this.appContext = appContext;
+		this.clock = clock;
 	}
 
 	@Override
@@ -182,6 +200,74 @@ class AndroidBluetoothPlugin extends BluetoothPlugin<BluetoothServerSocket> {
 		}
 	}
 
+	@Override
+	@Nullable
+	DuplexTransportConnection discoverAndConnect(String uuid) {
+		if (adapter == null) return null;
+		for (String address : discoverDevices()) {
+			try {
+				if (LOG.isLoggable(INFO))
+					LOG.info("Connecting to " + scrubMacAddress(address));
+				return connectTo(address, uuid);
+			} catch (IOException e) {
+				if (LOG.isLoggable(INFO)) {
+					LOG.info("Could not connect to "
+							+ scrubMacAddress(address));
+				}
+			}
+		}
+		LOG.info("Could not connect to any devices");
+		return null;
+	}
+
+	private Collection<String> discoverDevices() {
+		List<String> addresses = new ArrayList<>();
+		BlockingQueue<Intent> intents = new LinkedBlockingQueue<>();
+		DiscoveryReceiver receiver = new DiscoveryReceiver(intents);
+		IntentFilter filter = new IntentFilter();
+		filter.addAction(ACTION_DISCOVERY_STARTED);
+		filter.addAction(ACTION_DISCOVERY_FINISHED);
+		filter.addAction(ACTION_FOUND);
+		appContext.registerReceiver(receiver, filter);
+		try {
+			if (adapter.startDiscovery()) {
+				long now = clock.currentTimeMillis();
+				long end = now + MAX_DISCOVERY_MS;
+				while (now < end) {
+					Intent i = intents.poll(end - now, MILLISECONDS);
+					if (i == null) break;
+					String action = i.getAction();
+					if (ACTION_DISCOVERY_STARTED.equals(action)) {
+						LOG.info("Discovery started");
+					} else if (ACTION_DISCOVERY_FINISHED.equals(action)) {
+						LOG.info("Discovery finished");
+						break;
+					} else if (ACTION_FOUND.equals(action)) {
+						BluetoothDevice d = i.getParcelableExtra(EXTRA_DEVICE);
+						String address = d.getAddress();
+						if (LOG.isLoggable(INFO))
+							LOG.info("Discovered " + scrubMacAddress(address));
+						if (!addresses.contains(address))
+							addresses.add(address);
+					}
+					now = clock.currentTimeMillis();
+				}
+			} else {
+				LOG.info("Could not start discovery");
+			}
+		} catch (InterruptedException e) {
+			LOG.info("Interrupted while discovering devices");
+			Thread.currentThread().interrupt();
+		} finally {
+			LOG.info("Cancelling discovery");
+			adapter.cancelDiscovery();
+			appContext.unregisterReceiver(receiver);
+		}
+		// Shuffle the addresses so we don't always try the same one first
+		Collections.shuffle(addresses);
+		return addresses;
+	}
+
 	private void tryToClose(@Nullable Closeable c) {
 		try {
 			if (c != null) c.close();
@@ -207,4 +293,18 @@ class AndroidBluetoothPlugin extends BluetoothPlugin<BluetoothServerSocket> {
 			}
 		}
 	}
+
+	private static class DiscoveryReceiver extends BroadcastReceiver {
+
+		private final BlockingQueue<Intent> intents;
+
+		private DiscoveryReceiver(BlockingQueue<Intent> intents) {
+			this.intents = intents;
+		}
+
+		@Override
+		public void onReceive(Context ctx, Intent intent) {
+			intents.add(intent);
+		}
+	}
 }

bramble-android/src/main/java/org/briarproject/bramble/plugin/bluetooth/AndroidBluetoothPluginFactory.java

@@ -11,6 +11,7 @@ import org.briarproject.bramble.api.plugin.duplex.DuplexPlugin;
 import org.briarproject.bramble.api.plugin.duplex.DuplexPluginCallback;
 import org.briarproject.bramble.api.plugin.duplex.DuplexPluginFactory;
 import org.briarproject.bramble.api.system.AndroidExecutor;
+import org.briarproject.bramble.api.system.Clock;
 
 import java.security.SecureRandom;
 import java.util.concurrent.Executor;
@@ -33,17 +34,19 @@ public class AndroidBluetoothPluginFactory implements DuplexPluginFactory {
 	private final Context appContext;
 	private final SecureRandom secureRandom;
 	private final EventBus eventBus;
+	private final Clock clock;
 	private final BackoffFactory backoffFactory;
 
 	public AndroidBluetoothPluginFactory(Executor ioExecutor,
 			AndroidExecutor androidExecutor, Context appContext,
-			SecureRandom secureRandom, EventBus eventBus,
+			SecureRandom secureRandom, EventBus eventBus, Clock clock,
 			BackoffFactory backoffFactory) {
 		this.ioExecutor = ioExecutor;
 		this.androidExecutor = androidExecutor;
 		this.appContext = appContext;
 		this.secureRandom = secureRandom;
 		this.eventBus = eventBus;
+		this.clock = clock;
 		this.backoffFactory = backoffFactory;
 	}
 
@@ -65,7 +68,7 @@ public class AndroidBluetoothPluginFactory implements DuplexPluginFactory {
 				MAX_POLLING_INTERVAL, BACKOFF_BASE);
 		AndroidBluetoothPlugin plugin = new AndroidBluetoothPlugin(
 				connectionLimiter, ioExecutor, androidExecutor, appContext,
-				secureRandom, backoff, callback, MAX_LATENCY);
+				secureRandom, clock, backoff, callback, MAX_LATENCY);
 		eventBus.addListener(plugin);
 		return plugin;
 	}

bramble-android/src/main/java/org/briarproject/bramble/plugin/tor/AndroidTorPlugin.java

@@ -6,6 +6,7 @@ import android.content.pm.PackageManager;
 import android.content.pm.PackageManager.NameNotFoundException;
 import android.os.PowerManager;
 
+import org.briarproject.bramble.api.battery.BatteryManager;
 import org.briarproject.bramble.api.network.NetworkManager;
 import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
 import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
@@ -41,17 +42,18 @@ class AndroidTorPlugin extends TorPlugin {
 			Context appContext, NetworkManager networkManager,
 			LocationUtils locationUtils, SocketFactory torSocketFactory,
 			Clock clock, ResourceProvider resourceProvider,
-			CircumventionProvider circumventionProvider, Backoff backoff,
+			CircumventionProvider circumventionProvider,
+			BatteryManager batteryManager, Backoff backoff,
 			DuplexPluginCallback callback, String architecture, int maxLatency,
 			int maxIdleTime) {
 		super(ioExecutor, networkManager, locationUtils, torSocketFactory,
-				clock, resourceProvider, circumventionProvider, backoff,
-				callback, architecture, maxLatency, maxIdleTime,
+				clock, resourceProvider, circumventionProvider, batteryManager,
+				backoff, callback, architecture, maxLatency, maxIdleTime,
 				appContext.getDir("tor", MODE_PRIVATE));
 		this.appContext = appContext;
 		PowerManager pm = (PowerManager)
 				appContext.getSystemService(POWER_SERVICE);
-		assert pm != null;
+		if (pm == null) throw new AssertionError();
 		wakeLock = new RenewableWakeLock(pm, scheduler, PARTIAL_WAKE_LOCK,
 				WAKE_LOCK_TAG, 1, MINUTES);
 	}

bramble-android/src/main/java/org/briarproject/bramble/plugin/tor/AndroidTorPluginFactory.java

@@ -3,6 +3,7 @@ package org.briarproject.bramble.plugin.tor;
 import android.content.Context;
 import android.os.Build;
 
+import org.briarproject.bramble.api.battery.BatteryManager;
 import org.briarproject.bramble.api.event.EventBus;
 import org.briarproject.bramble.api.network.NetworkManager;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
@@ -48,6 +49,7 @@ public class AndroidTorPluginFactory implements DuplexPluginFactory {
 	private final BackoffFactory backoffFactory;
 	private final ResourceProvider resourceProvider;
 	private final CircumventionProvider circumventionProvider;
+	private final BatteryManager batteryManager;
 	private final Clock clock;
 
 	public AndroidTorPluginFactory(Executor ioExecutor,
@@ -55,7 +57,8 @@ public class AndroidTorPluginFactory implements DuplexPluginFactory {
 			NetworkManager networkManager, LocationUtils locationUtils,
 			EventBus eventBus, SocketFactory torSocketFactory,
 			BackoffFactory backoffFactory, ResourceProvider resourceProvider,
-			CircumventionProvider circumventionProvider, Clock clock) {
+			CircumventionProvider circumventionProvider,
+			BatteryManager batteryManager, Clock clock) {
 		this.ioExecutor = ioExecutor;
 		this.scheduler = scheduler;
 		this.appContext = appContext;
@@ -66,6 +69,7 @@ public class AndroidTorPluginFactory implements DuplexPluginFactory {
 		this.backoffFactory = backoffFactory;
 		this.resourceProvider = resourceProvider;
 		this.circumventionProvider = circumventionProvider;
+		this.batteryManager = batteryManager;
 		this.clock = clock;
 	}
 
@@ -104,8 +108,8 @@ public class AndroidTorPluginFactory implements DuplexPluginFactory {
 				MAX_POLLING_INTERVAL, BACKOFF_BASE);
 		AndroidTorPlugin plugin = new AndroidTorPlugin(ioExecutor, scheduler,
 				appContext, networkManager, locationUtils, torSocketFactory,
-				clock, resourceProvider, circumventionProvider, backoff,
-				callback, architecture, MAX_LATENCY, MAX_IDLE_TIME);
+				clock, resourceProvider, circumventionProvider, batteryManager,
+				backoff, callback, architecture, MAX_LATENCY, MAX_IDLE_TIME);
 		eventBus.addListener(plugin);
 		return plugin;
 	}

bramble-android/src/main/java/org/briarproject/bramble/util/AndroidUtils.java

@@ -11,15 +11,12 @@ import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
 import java.util.List;
-import java.util.logging.Logger;
 
 import static android.content.Context.MODE_PRIVATE;
+import static android.os.Build.VERSION.SDK_INT;
 
 public class AndroidUtils {
 
-	private static final Logger LOG =
-			Logger.getLogger(AndroidUtils.class.getName());
-
 	// Fake Bluetooth address returned by BluetoothAdapter on API 23 and later
 	private static final String FAKE_BLUETOOTH_ADDRESS = "02:00:00:00:00:00";
 
@@ -28,7 +25,7 @@ public class AndroidUtils {
 	@SuppressWarnings("deprecation")
 	public static Collection<String> getSupportedArchitectures() {
 		List<String> abis = new ArrayList<>();
-		if (Build.VERSION.SDK_INT >= 21) {
+		if (SDK_INT >= 21) {
 			abis.addAll(Arrays.asList(Build.SUPPORTED_ABIS));
 		} else {
 			abis.add(Build.CPU_ABI);

bramble-android/witness.gradle

@@ -1,50 +1,57 @@
 dependencyVerification {
     verify = [
         'cglib:cglib:3.2.0:cglib-3.2.0.jar:adb13bab79712ad6bdf1bd59f2a3918018a8016e722e8a357065afb9e6690861',
-        'com.android.tools.analytics-library:protos:26.1.3:protos-26.1.3.jar:818c9f256f141d9dafec03a1aa2b94d240b2c140acfd7ee31a8b3e6c2b9479e3',
-        'com.android.tools.analytics-library:shared:26.1.3:shared-26.1.3.jar:7110706c7ada96c8b6f5ca80c478291bc7899d46277de2c48527e045442401a3',
-        'com.android.tools.analytics-library:tracker:26.1.3:tracker-26.1.3.jar:4155424bf2ce4872da83332579a1707252bc66cbd77c5144fdc4483d0f2e1418',
-        'com.android.tools.build:apksig:3.1.3:apksig-3.1.3.jar:7e1f8e675a6e768e5b56405e41d6c3cc05befe62e601b04177de1029902c9c89',
-        'com.android.tools.build:builder-model:3.1.3:builder-model-3.1.3.jar:06ad1c422d679fc698451479cb40ba863849d67bfd1de23f6d2c16d78b024b0b',
-        'com.android.tools.build:builder-test-api:3.1.3:builder-test-api-3.1.3.jar:4d989f780436794f0f8b2f50e9e079b786571eac90f26c208ab2ae6d4012f389',
-        'com.android.tools.build:builder:3.1.3:builder-3.1.3.jar:8a1092012c89d0ec1ee2eff09c5708c71ef4482a6862df8d3a44a67fccace01c',
-        'com.android.tools.build:gradle-api:3.1.3:gradle-api-3.1.3.jar:01e4df521456aef66514336f1d492346730dd1fb8f6433a89f62da834941ed72',
-        'com.android.tools.build:manifest-merger:26.1.3:manifest-merger-26.1.3.jar:1e4fc7e932adb4607082409800e5e6fccb42e6c5360ae5990094bf522f3ada55',
-        'com.android.tools.ddms:ddmlib:26.1.3:ddmlib-26.1.3.jar:c54931cd68df5d1ea2923b3b320eae47cd2307a5a916bb8674c0acf93cd1d3cd',
-        'com.android.tools.external.com-intellij:intellij-core:26.1.3:intellij-core-26.1.3.jar:af67f5535fef2e1a28b1007a4acb8c5deb6a1e33b8afe7b11d012c9e778ebcec',
-        'com.android.tools.external.com-intellij:kotlin-compiler:26.1.3:kotlin-compiler-26.1.3.jar:c746d2859dc11cc05c84b692b3498d3a621e0929511f8440ee009c6557838fd4',
-        'com.android.tools.external.org-jetbrains:uast:26.1.3:uast-26.1.3.jar:3f3f6651d0c7685a77ecb22e9c82d6b49fdf24322c17360768dc530678f43265',
-        'com.android.tools.layoutlib:layoutlib-api:26.1.3:layoutlib-api-26.1.3.jar:10bc73ce706c45629872d6a999dbe12116df64e24f47ff93b7b13121ff57b4b0',
-        'com.android.tools.lint:lint-api:26.1.3:lint-api-26.1.3.jar:6f97323f9af8deda86278717885b5c927f3766757db89709f52d11d42b6fb751',
-        'com.android.tools.lint:lint-checks:26.1.3:lint-checks-26.1.3.jar:73c3d53784c9ce3e6d5968506581918e0179645d20809927ca4a001dd766b001',
-        'com.android.tools.lint:lint-gradle-api:26.1.3:lint-gradle-api-26.1.3.jar:7ca3c4866ec21dc21d53a9d86f752b77ace6f6c610a0c9dc877313856c733d9d',
-        'com.android.tools.lint:lint-gradle:26.1.3:lint-gradle-26.1.3.jar:db0c354b8f4b6f6637e31f91c564785a59ff896325331fcbc3de7458e0b6c067',
-        'com.android.tools.lint:lint-kotlin:26.1.3:lint-kotlin-26.1.3.jar:94e2b0f4565a241561cfb8fc1222bb3f132a3b98d2a90421dbb72ee8358e7d68',
-        'com.android.tools.lint:lint:26.1.3:lint-26.1.3.jar:8d5f32c989c6d191d712e90ad3ca2d1c409313599551d04d834caa44d26c78df',
-        'com.android.tools:annotations:26.1.3:annotations-26.1.3.jar:c950430b24ac5d58fc97e7283b8f0115f99587e76e08b4e1e2aaa780f2d77323',
-        'com.android.tools:common:26.1.3:common-26.1.3.jar:7c31a90581a148ab219f615a59667f0dded7fa39b248529784474da3c2274ef2',
-        'com.android.tools:dvlib:26.1.3:dvlib-26.1.3.jar:0cae87906f53d3f1088366a916ed180a7312b6d9919b90797f238875c8492855',
-        'com.android.tools:repository:26.1.3:repository-26.1.3.jar:52d4539cc68db91b261e2a33b2c8206b26e05539078758dc28cfb3854adb4f59',
-        'com.android.tools:sdk-common:26.1.3:sdk-common-26.1.3.jar:1948603ca9ff22c7ebb3178000bffa3a9dd2ca1cc5cb0c793cae08468b8fcfc1',
-        'com.android.tools:sdklib:26.1.3:sdklib-26.1.3.jar:4adcfaad9514607098d2c51503c39811112d3050f4d1e744c01c7f08f591032b',
+        'com.android.tools.analytics-library:protos:26.2.1:protos-26.2.1.jar:2f371f5b1f551e85ab08be4d6a2873471b3d44afd1ebf6aa3298f3b796bf691f',
+        'com.android.tools.analytics-library:shared:26.2.1:shared-26.2.1.jar:4c1e4e705fa4d45f23aaea230557f6508155012d9c296337787c1d7b26a97f5a',
+        'com.android.tools.analytics-library:tracker:26.2.1:tracker-26.2.1.jar:4a624ecc976539f755ddb0bb8dfc2dd3d08326cfec59a098dbd70f701ca7fb75',
+        'com.android.tools.build:aapt2:3.2.1-4818971:aapt2-3.2.1-4818971-linux.jar:f431b6f96c91a2c155144b091a9c97d9805c589fe8efc9c930b6cd346cb60a1e',
+        'com.android.tools.build:apksig:3.2.1:apksig-3.2.1.jar:2b46f2feffea66037aab29e4261b2433c190194a6ef97b958511eb157f2ccba5',
+        'com.android.tools.build:apkzlib:3.2.1:apkzlib-3.2.1.jar:c39ad0313905932431fe81c8899c2cf39a4d92ad6c4edcaa4b25432f461452aa',
+        'com.android.tools.build:builder-model:3.2.1:builder-model-3.2.1.jar:a9f68e6abcec122f9cb5ad352d3f05a3eb03acbcdca95e4d25c16310c2c965ff',
+        'com.android.tools.build:builder-test-api:3.2.1:builder-test-api-3.2.1.jar:533ac6c2b5884bb54967a33791f2628dfdfac7981af39417a333b43d4379b6be',
+        'com.android.tools.build:builder:3.2.1:builder-3.2.1.jar:aedcbfd115dbe91d09b4113e66ef50589b558d0aa3b2f133b1d867c9b87fae83',
+        'com.android.tools.build:gradle-api:3.2.1:gradle-api-3.2.1.jar:57cf0ac5ac1dca8afdb3f62b94265e776e7dcfa641cc3844fb53a05193de208d',
+        'com.android.tools.build:manifest-merger:26.2.1:manifest-merger-26.2.1.jar:8830573263361035d38cfdcb51e2db94029c93865b21334f5fbf8a27984281a6',
+        'com.android.tools.ddms:ddmlib:26.2.1:ddmlib-26.2.1.jar:a4bf0a29a19980bf27269465cc782064656750b77c26728f82f9e148b705218b',
+        'com.android.tools.external.com-intellij:intellij-core:26.2.1:intellij-core-26.2.1.jar:4925ad1892c2687cb1a63427d440ef519c8c59215fefe0dc5d541d5d411fcafe',
+        'com.android.tools.external.com-intellij:kotlin-compiler:26.2.1:kotlin-compiler-26.2.1.jar:daa064fd708f340ee25fb9823c4c74104ac77f1370b76d907eb9ae6daec0a2ae',
+        'com.android.tools.external.org-jetbrains:uast:26.2.1:uast-26.2.1.jar:f10f7258d2ab9189562cc0f9ad838c0378fdba439229173390a99de02ebac75b',
+        'com.android.tools.layoutlib:layoutlib-api:26.2.1:layoutlib-api-26.2.1.jar:ddbf4fca123733fa011595b1cc1f4ac2937ed327b60990711fafc33c775c2ade',
+        'com.android.tools.lint:lint-api:26.2.1:lint-api-26.2.1.jar:3b57e739de567b98bc9ab56c2c0ee66fc026b4adf5843e8f9804ca0666a6f66e',
+        'com.android.tools.lint:lint-checks:26.2.1:lint-checks-26.2.1.jar:c86f4cc9aaee722ee4ad70062f7b5af91e9b041914af27adc09f545ab0fb3bc6',
+        'com.android.tools.lint:lint-gradle-api:26.2.1:lint-gradle-api-26.2.1.jar:2283e7af32e301565f2a797e531f0fc8c648077d457afb3ffdddbee638976c2f',
+        'com.android.tools.lint:lint-gradle:26.2.1:lint-gradle-26.2.1.jar:8fd90b2f3ec788cbb9801c07ab3e1ea2255aa31a6093157d7ea0ff13d0315ecb',
+        'com.android.tools.lint:lint-kotlin:26.2.1:lint-kotlin-26.2.1.jar:7a6a5d2b18f69cf1b900d857c2632b4c683713c533295933b8b759f8cab4a877',
+        'com.android.tools.lint:lint:26.2.1:lint-26.2.1.jar:7848b82ae988b90dee259ae7c7e86e05cbf52db6cd21c8bbd38ce7df08f3f8c5',
+        'com.android.tools:annotations:26.2.1:annotations-26.2.1.jar:7391c6a1e080174b96e64ceb078dadd31ce4d8a2d2fee0ec65be202126f90f24',
+        'com.android.tools:common:26.2.1:common-26.2.1.jar:a50aab2d6411ff68f4004a87c7e93d87d8e980a0ec3b352246549897ea2d78e5',
+        'com.android.tools:dvlib:26.2.1:dvlib-26.2.1.jar:72a83bf2839b1df9b1fbf67ba45d1bfb9f966cd774da4320c762b2be8f1688aa',
+        'com.android.tools:repository:26.2.1:repository-26.2.1.jar:fa74dae09103faef703df38550ad8fa244c5b6d1bf90d6198be932292b3d9cc1',
+        'com.android.tools:sdk-common:26.2.1:sdk-common-26.2.1.jar:759d4b292ca69a35cf961fca377b54158fc6c88108978006999442e80a011cf4',
+        'com.android.tools:sdklib:26.2.1:sdklib-26.2.1.jar:248df7ad5eac4aeb6f96c394c76760de4b7b89ac056e54d0c21a739368b91b45',
         'com.google.code.findbugs:jsr305:1.3.9:jsr305-1.3.9.jar:905721a0eea90a81534abb7ee6ef4ea2e5e645fa1def0a5cd88402df1b46c9ed',
-        'com.google.code.gson:gson:2.7:gson-2.7.jar:2d43eb5ea9e133d2ee2405cc14f5ee08951b8361302fdd93494a3a997b508d32',
-        'com.google.dagger:dagger-compiler:2.0.2:dagger-compiler-2.0.2.jar:b74bc9de063dd4c6400b232231f2ef5056145b8fbecbf5382012007dd1c071b3',
-        'com.google.dagger:dagger-producers:2.0-beta:dagger-producers-2.0-beta.jar:99ec15e8a0507ba569e7655bc1165ee5e5ca5aa914b3c8f7e2c2458f724edd6b',
-        'com.google.dagger:dagger:2.0.2:dagger-2.0.2.jar:84c0282ed8be73a29e0475d639da030b55dee72369e58dd35ae7d4fe6243dcf9',
+        'com.google.code.gson:gson:2.8.0:gson-2.8.0.jar:c6221763bd79c4f1c3dc7f750b5f29a0bb38b367b81314c4f71896e340c40825',
+        'com.google.dagger:dagger-compiler:2.19:dagger-compiler-2.19.jar:27a4b202a2de908182edb261f8c0a264e08e5e4733d7514bc7fbf0d31da5c0fc',
+        'com.google.dagger:dagger-producers:2.19:dagger-producers-2.19.jar:a17663abe0fc38b676026950907d4c5f5e2bf338375415861eaff6e3bdb0b768',
+        'com.google.dagger:dagger-spi:2.19:dagger-spi-2.19.jar:e7a6379d82c841f6aac2866948ad1eed716528707814602842a8d844ce04e2e1',
+        'com.google.dagger:dagger:2.19:dagger-2.19.jar:514b6f1e0727c6572e1d65cb27e4ae668b7aeaeb93a29515182965265b609939',
         'com.google.errorprone:error_prone_annotations:2.0.18:error_prone_annotations-2.0.18.jar:cb4cfad870bf563a07199f3ebea5763f0dec440fcda0b318640b1feaa788656b',
-        'com.google.guava:guava:18.0:guava-18.0.jar:d664fbfc03d2e5ce9cab2a44fb01f1d0bf9dfebeccc1a473b1f9ea31f79f6f99',
-        'com.google.guava:guava:22.0:guava-22.0.jar:1158e94c7de4da480873f0b4ab4a1da14c0d23d4b1902cc94a58a6f0f9ab579e',
+        'com.google.errorprone:error_prone_annotations:2.1.3:error_prone_annotations-2.1.3.jar:03d0329547c13da9e17c634d1049ea2ead093925e290567e1a364fd6b1fc7ff8',
+        'com.google.errorprone:javac-shaded:9-dev-r4023-3:javac-shaded-9-dev-r4023-3.jar:65bfccf60986c47fbc17c9ebab0be626afc41741e0a6ec7109e0768817a36f30',
+        'com.google.googlejavaformat:google-java-format:1.5:google-java-format-1.5.jar:aa19ad7850fb85178aa22f2fddb163b84d6ce4d0035872f30d4408195ca1144e',
+        'com.google.guava:guava:23.0:guava-23.0.jar:7baa80df284117e5b945b19b98d367a85ea7b7801bd358ff657946c3bd1b6596',
+        'com.google.guava:guava:25.0-jre:guava-25.0-jre.jar:3fd4341776428c7e0e5c18a7c10de129475b69ab9d30aeafbb5c277bb6074fa9',
         'com.google.j2objc:j2objc-annotations:1.1:j2objc-annotations-1.1.jar:40ceb7157feb263949e0f503fe5f71689333a621021aa20ce0d0acee3badaa0f',
         'com.google.jimfs:jimfs:1.1:jimfs-1.1.jar:c4828e28d7c0a930af9387510b3bada7daa5c04d7c25a75c7b8b081f1c257ddd',
         'com.google.protobuf:protobuf-java:3.4.0:protobuf-java-3.4.0.jar:dce7e66b32456a1b1198da0caff3a8acb71548658391e798c79369241e6490a4',
         'com.googlecode.json-simple:json-simple:1.1:json-simple-1.1.jar:2d9484f4c649f708f47f9a479465fc729770ee65617dca3011836602264f6439',
+        'com.squareup:javapoet:1.11.1:javapoet-1.11.1.jar:9cbf2107be499ec6e95afd36b58e3ca122a24166cdd375732e51267d64058e90',
         'com.squareup:javawriter:2.5.0:javawriter-2.5.0.jar:fcfb09fb0ea0aa97d3cfe7ea792398081348e468f126b3603cb3803f240197f0',
         'com.sun.activation:javax.activation:1.2.0:javax.activation-1.2.0.jar:993302b16cd7056f21e779cc577d175a810bb4900ef73cd8fbf2b50f928ba9ce',
         'com.sun.istack:istack-commons-runtime:2.21:istack-commons-runtime-2.21.jar:c33e67a0807095f02a0e2da139412dd7c4f9cc1a4c054b3e434f96831ba950f4',
         'com.sun.xml.fastinfoset:FastInfoset:1.2.13:FastInfoset-1.2.13.jar:27a77db909f3c2833c0b1a37c55af1db06045118ad2eed96ce567b6632bce038',
-        'commons-codec:commons-codec:1.6:commons-codec-1.6.jar:54b34e941b8e1414bd3e40d736efd3481772dc26db3296f6aa45cec9f6203d86',
-        'commons-logging:commons-logging:1.1.1:commons-logging-1.1.1.jar:ce6f913cad1f0db3aad70186d65c5bc7ffcc9a99e3fe8e0b137312819f7c362f',
+        'commons-codec:commons-codec:1.9:commons-codec-1.9.jar:ad19d2601c3abf0b946b5c3a4113e226a8c1e3305e395b90013b78dd94a723ce',
+        'commons-logging:commons-logging:1.2:commons-logging-1.2.jar:daddea1ea0be0f56978ab3006b8ac92834afeefbd9b7e4e6316fca57df0fa636',
         'it.unimi.dsi:fastutil:7.2.0:fastutil-7.2.0.jar:74fa208043740642f7e6eb09faba15965218ad2f50ce3020efb100136e4b591c',
         'javax.annotation:jsr250-api:1.0:jsr250-api-1.0.jar:a1a922d0d9b6d183ed3800dfac01d1e1eb159f0e8c6f94736931c1def54a941f',
         'javax.inject:javax.inject:1:javax.inject-1.jar:91c77044a50c481636c32d916fd89c9118a72195390452c81065080f957de7ff',
@@ -55,13 +62,15 @@ dependencyVerification {
         'org.apache.ant:ant-launcher:1.9.4:ant-launcher-1.9.4.jar:7bccea20b41801ca17bcbc909a78c835d0f443f12d639c77bd6ae3d05861608d',
         'org.apache.ant:ant:1.9.4:ant-1.9.4.jar:649ae0730251de07b8913f49286d46bba7b92d47c5f332610aa426c4f02161d8',
         'org.apache.commons:commons-compress:1.12:commons-compress-1.12.jar:2c1542faf343185b7cab9c3d55c8ae5471d6d095d3887a4adefdbdf2984dc0b6',
-        'org.apache.httpcomponents:httpclient:4.2.6:httpclient-4.2.6.jar:362e9324ee7c697e21279e20077b52737ddef3f1b2c1a7abe5ad34b465145550',
-        'org.apache.httpcomponents:httpcore:4.2.5:httpcore-4.2.5.jar:e5e82da4cc66c8d917bbf743e3c0752efe8522735e7fc9dbddb65bccea81cfe9',
-        'org.apache.httpcomponents:httpmime:4.1:httpmime-4.1.jar:31629566148e8a47688ae43b420abc3ecd783ed15b33bebc00824bf24c9b15aa',
+        'org.apache.httpcomponents:httpclient:4.5.2:httpclient-4.5.2.jar:0dffc621400d6c632f55787d996b8aeca36b30746a716e079a985f24d8074057',
+        'org.apache.httpcomponents:httpcore:4.4.5:httpcore-4.4.5.jar:64d5453874cab7e40a7065cb01a9a9ca1053845a9786b478878b679e0580cec3',
+        'org.apache.httpcomponents:httpmime:4.5.2:httpmime-4.5.2.jar:231a3f7e4962053db2be8461d5422e68fc458a3a7dd7d8ada803a348e21f8f07',
         'org.beanshell:bsh:1.3.0:bsh-1.3.0.jar:9b04edc75d19db54f1b4e8b5355e9364384c6cf71eb0a1b9724c159d779879f8',
         'org.bouncycastle:bcpkix-jdk15on:1.56:bcpkix-jdk15on-1.56.jar:7043dee4e9e7175e93e0b36f45b1ec1ecb893c5f755667e8b916eb8dd201c6ca',
         'org.bouncycastle:bcprov-jdk15on:1.56:bcprov-jdk15on-1.56.jar:963e1ee14f808ffb99897d848ddcdb28fa91ddda867eb18d303e82728f878349',
-        'org.briarproject:tor-android:0.2.9.16:tor-android-0.2.9.16.zip:515e33dda6a30853c885a2de2c79ae1ab9ad8b6db44f5db8890333ec2e24f4ae',
+        'org.briarproject:obfs4proxy-android:0.0.7:obfs4proxy-android-0.0.7.zip:abdfb5d889d848de9bf214f9276abbf454808a505b870819eccc9a9e985bf617',
+        'org.briarproject:tor-android:0.3.4.8:tor-android-0.3.4.8.zip:989a0352d9d8d8172cd6c2137654e165e5d2beb10ed1211bab3814e224ad1926',
+        'org.checkerframework:checker-compat-qual:2.5.3:checker-compat-qual-2.5.3.jar:d76b9afea61c7c082908023f0cbc1427fab9abd2df915c8b8a3e7a509bccbc6d',
         'org.codehaus.groovy:groovy-all:2.4.12:groovy-all-2.4.12.jar:6a56af4bd48903d56bec62821876cadefafd007360cc6bd0d8f7aa8d72b38be4',
         'org.codehaus.mojo:animal-sniffer-annotations:1.14:animal-sniffer-annotations-1.14.jar:2068320bd6bad744c3673ab048f67e30bef8f518996fa380033556600669905d',
         'org.glassfish.jaxb:jaxb-core:2.2.11:jaxb-core-2.2.11.jar:37bcaee8ebb04362c8352a5bf6221b86967ecdab5164c696b10b9a2bb587b2aa',
@@ -70,9 +79,10 @@ dependencyVerification {
         'org.hamcrest:hamcrest-core:1.3:hamcrest-core-1.3.jar:66fdef91e9739348df7a096aa384a5685f4e875584cce89386a7a47251c4d8e9',
         'org.hamcrest:hamcrest-library:1.3:hamcrest-library-1.3.jar:711d64522f9ec410983bd310934296da134be4254a125080a0416ec178dfad1c',
         'org.jetbrains.kotlin:kotlin-reflect:1.2.0:kotlin-reflect-1.2.0.jar:4f48a872bad6e4d9c053f4ad610d11e4012ad7e58dc19a03dd5eb811f36069dd',
-        'org.jetbrains.kotlin:kotlin-stdlib-jre7:1.2.0:kotlin-stdlib-jre7-1.2.0.jar:c7a20fb951d437797afe8980aff6c1e5a03f310c661ba58ba1d4fa90cb0f2926',
-        'org.jetbrains.kotlin:kotlin-stdlib-jre8:1.2.0:kotlin-stdlib-jre8-1.2.0.jar:633524eee6ef1941f7cb1dab7ee3927b0a221ceee9047aeb5515f4cbb990c82a',
-        'org.jetbrains.kotlin:kotlin-stdlib:1.2.0:kotlin-stdlib-1.2.0.jar:05cfd9f5ac0b41910703a8925f7211a495909b27a2ffdd1c5106f1689aeafcd4',
+        'org.jetbrains.kotlin:kotlin-stdlib-common:1.2.71:kotlin-stdlib-common-1.2.71.jar:63999687ff2fce8a592dd180ffbbf8f1d21c26b4044c55cdc74ff3cf3b3cf328',
+        'org.jetbrains.kotlin:kotlin-stdlib-jdk7:1.2.71:kotlin-stdlib-jdk7-1.2.71.jar:b136bd61b240e07d4d92ce00d3bd1dbf584400a7bf5f220c2f3cd22446858082',
+        'org.jetbrains.kotlin:kotlin-stdlib-jdk8:1.2.71:kotlin-stdlib-jdk8-1.2.71.jar:ac3c8abf47790b64b4f7e2509a53f0c145e061ac1612a597520535d199946ea9',
+        'org.jetbrains.kotlin:kotlin-stdlib:1.2.71:kotlin-stdlib-1.2.71.jar:4c895c270b87f5fec2a2796e1d89c15407ee821de961527c28588bb46afbc68b',
         'org.jetbrains.trove4j:trove4j:20160824:trove4j-20160824.jar:1917871c8deb468307a584680c87a44572f5a8b0b98c6d397fc0f5f86596dbe7',
         'org.jetbrains:annotations:13.0:annotations-13.0.jar:ace2a10dc8e2d5fd34925ecac03e4988b2c0f851650c94b8cef49ba1bd111478',
         'org.jmock:jmock-junit4:2.8.2:jmock-junit4-2.8.2.jar:f7ee4df4f7bd7b7f1cafad3b99eb74d579f109d5992ff625347352edb55e674c',
@@ -81,11 +91,11 @@ dependencyVerification {
         'org.jmock:jmock:2.8.2:jmock-2.8.2.jar:6c73cb4a2e6dbfb61fd99c9a768539c170ab6568e57846bd60dbf19596b65b16',
         'org.jvnet.staxex:stax-ex:1.7.7:stax-ex-1.7.7.jar:a31ff7d77163c0deb09e7fee59ad35ae44c2cee2cc8552a116ccd1583d813fb4',
         'org.objenesis:objenesis:2.1:objenesis-2.1.jar:c74330cc6b806c804fd37e74487b4fe5d7c2750c5e15fbc6efa13bdee1bdef80',
-        'org.ow2.asm:asm-analysis:5.1:asm-analysis-5.1.jar:a34658f5c5de4b573eef21131cc32cc25f7b66407944f312b28ec2e56abb1fa9',
-        'org.ow2.asm:asm-commons:5.1:asm-commons-5.1.jar:97b3786e1f55e74bddf8ad102bf50e33bbcbc1f6b7fd7b36f0bbbb25cd4981be',
-        'org.ow2.asm:asm-tree:5.1:asm-tree-5.1.jar:c0de2bbc4cb8297419659813ecd4ed1d077ed1dd5c1f5544cc5143e493e84c10',
-        'org.ow2.asm:asm-util:5.1:asm-util-5.1.jar:ee032c39ae5e3cd099148fbba9a2124f9ed613e5cb93e03ee0fa8808ce364040',
+        'org.ow2.asm:asm-analysis:6.0:asm-analysis-6.0.jar:2f1a6387219c3a6cc4856481f221b03bd9f2408a326d416af09af5d6f608c1f4',
+        'org.ow2.asm:asm-commons:6.0:asm-commons-6.0.jar:f1bce5c648a96a017bdcd01fe5d59af9845297fd7b79b81c015a6fbbd9719abf',
+        'org.ow2.asm:asm-tree:6.0:asm-tree-6.0.jar:887998fb69727c8759e4d253f856822801e33f9fd4caa566b3ac58ee92106215',
+        'org.ow2.asm:asm-util:6.0:asm-util-6.0.jar:356afebdb0f870175262e5188f8709a3b17aa2a5a6a4b0340b04d4b449bca5f6',
         'org.ow2.asm:asm:5.0.4:asm-5.0.4.jar:896618ed8ae62702521a78bc7be42b7c491a08e6920a15f89a3ecdec31e9a220',
-        'org.ow2.asm:asm:5.1:asm-5.1.jar:d2da399a9967c69f0a21739256fa79d284222c223082cacadc17372244764b54',
+        'org.ow2.asm:asm:6.0:asm-6.0.jar:dd8971c74a4e697899a8e95caae4ea8760ea6c486dc6b97b1795e75760420461',
     ]
 }

bramble-api/build.gradle

@@ -7,15 +7,13 @@ apply plugin: 'witness'
 apply from: 'witness.gradle'
 
 dependencies {
-	implementation "com.google.dagger:dagger:2.0.2"
+	implementation "com.google.dagger:dagger:2.19"
 	implementation 'com.google.code.findbugs:jsr305:3.0.2'
 
 	testImplementation 'junit:junit:4.12'
 	testImplementation "org.jmock:jmock:2.8.2"
 	testImplementation "org.jmock:jmock-junit4:2.8.2"
 	testImplementation "org.jmock:jmock-legacy:2.8.2"
-	testImplementation "org.hamcrest:hamcrest-library:1.3"
-	testImplementation "org.hamcrest:hamcrest-core:1.3"
 
 	signature 'org.codehaus.mojo.signature:java16:1.1@signature'
 }

bramble-api/src/main/java/org/briarproject/bramble/api/Pair.java

@@ -0,0 +1,26 @@
+package org.briarproject.bramble.api;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+
+import javax.annotation.concurrent.Immutable;
+
+@Immutable
+@NotNullByDefault
+public class Pair<A, B> {
+
+	private final A first;
+	private final B second;
+
+	public Pair(A first, B second) {
+		this.first = first;
+		this.second = second;
+	}
+
+	public A getFirst() {
+		return first;
+	}
+
+	public B getSecond() {
+		return second;
+	}
+}

bramble-api/src/main/java/org/briarproject/bramble/api/StringMap.java

@@ -38,4 +38,18 @@ public abstract class StringMap extends Hashtable<String, String> {
 	public void putInt(String key, int value) {
 		put(key, String.valueOf(value));
 	}
+
+	public long getLong(String key, long defaultValue) {
+		String s = get(key);
+		if (s == null) return defaultValue;
+		try {
+			return Long.valueOf(s);
+		} catch (NumberFormatException e) {
+			return defaultValue;
+		}
+	}
+
+	public void putLong(String key, long value) {
+		put(key, String.valueOf(value));
+	}
 }

bramble-api/src/main/java/org/briarproject/bramble/api/battery/BatteryManager.java

@@ -0,0 +1,6 @@
+package org.briarproject.bramble.api.battery;
+
+public interface BatteryManager {
+
+	boolean isCharging();
+}

bramble-api/src/main/java/org/briarproject/bramble/api/battery/event/BatteryEvent.java

@@ -0,0 +1,19 @@
+package org.briarproject.bramble.api.battery.event;
+
+import org.briarproject.bramble.api.event.Event;
+
+/**
+ * An event that is broadcast when the device starts or stops charging.
+ */
+public class BatteryEvent extends Event {
+
+	private final boolean charging;
+
+	public BatteryEvent(boolean charging) {
+		this.charging = charging;
+	}
+
+	public boolean isCharging() {
+		return charging;
+	}
+}

bramble-api/src/main/java/org/briarproject/bramble/api/client/BdfMessageValidator.java

@@ -48,12 +48,8 @@ public abstract class BdfMessageValidator implements MessageValidator {
 			throw new InvalidMessageException(
 					"Timestamp is too far in the future");
 		}
-		byte[] body = m.getBody();
-		if (body.length == 0) {
-			throw new InvalidMessageException("Message is too short");
-		}
 		try {
-			BdfList bodyList = clientHelper.toList(body);
+			BdfList bodyList = clientHelper.toList(m.getBody());
 			BdfMessageContext result = validateMessage(m, g, bodyList);
 			Metadata meta = metadataEncoder.encode(result.getDictionary());
 			return new MessageContext(meta, result.getDependencies());

bramble-api/src/main/java/org/briarproject/bramble/api/contact/Contact.java

@@ -4,8 +4,12 @@ import org.briarproject.bramble.api.identity.Author;
 import org.briarproject.bramble.api.identity.AuthorId;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 
+import javax.annotation.Nullable;
 import javax.annotation.concurrent.Immutable;
 
+import static org.briarproject.bramble.api.identity.AuthorConstants.MAX_AUTHOR_NAME_LENGTH;
+import static org.briarproject.bramble.util.StringUtils.toUtf8;
+
 @Immutable
 @NotNullByDefault
 public class Contact {
@@ -13,13 +17,21 @@ public class Contact {
 	private final ContactId id;
 	private final Author author;
 	private final AuthorId localAuthorId;
+	@Nullable
+	private final String alias;
 	private final boolean verified, active;
 
 	public Contact(ContactId id, Author author, AuthorId localAuthorId,
-			boolean verified, boolean active) {
+			@Nullable String alias, boolean verified, boolean active) {
+		if (alias != null) {
+			int aliasLength = toUtf8(alias).length;
+			if (aliasLength == 0 || aliasLength > MAX_AUTHOR_NAME_LENGTH)
+				throw new IllegalArgumentException();
+		}
 		this.id = id;
 		this.author = author;
 		this.localAuthorId = localAuthorId;
+		this.alias = alias;
 		this.verified = verified;
 		this.active = active;
 	}
@@ -36,6 +48,11 @@ public class Contact {
 		return localAuthorId;
 	}
 
+	@Nullable
+	public String getAlias() {
+		return alias;
+	}
+
 	public boolean isVerified() {
 		return verified;
 	}

bramble-api/src/main/java/org/briarproject/bramble/api/contact/ContactManager.java

@@ -5,11 +5,14 @@ import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.db.Transaction;
 import org.briarproject.bramble.api.identity.Author;
 import org.briarproject.bramble.api.identity.AuthorId;
+import org.briarproject.bramble.api.identity.AuthorInfo;
 import org.briarproject.bramble.api.lifecycle.LifecycleManager;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 
 import java.util.Collection;
 
+import javax.annotation.Nullable;
+
 @NotNullByDefault
 public interface ContactManager {
 
@@ -93,6 +96,18 @@ public interface ContactManager {
 	void setContactActive(Transaction txn, ContactId c, boolean active)
 			throws DbException;
 
+	/**
+	 * Sets an alias name for the contact or unsets it if alias is null.
+	 */
+	void setContactAlias(Transaction txn, ContactId c, @Nullable String alias)
+			throws DbException;
+
+	/**
+	 * Sets an alias name for the contact or unsets it if alias is null.
+	 */
+	void setContactAlias(ContactId c, @Nullable String alias)
+			throws DbException;
+
 	/**
 	 * Return true if a contact with this name and public key already exists
 	 */
@@ -105,6 +120,16 @@ public interface ContactManager {
 	boolean contactExists(AuthorId remoteAuthorId, AuthorId localAuthorId)
 			throws DbException;
 
+	/**
+	 * Returns the {@link AuthorInfo} for the given author.
+	 */
+	AuthorInfo getAuthorInfo(AuthorId a) throws DbException;
+
+	/**
+	 * Returns the {@link AuthorInfo} for the given author.
+	 */
+	AuthorInfo getAuthorInfo(Transaction txn, AuthorId a) throws DbException;
+
 	interface ContactHook {
 
 		void addingContact(Transaction txn, Contact c) throws DbException;

bramble-api/src/main/java/org/briarproject/bramble/api/data/BdfStringUtils.java

@@ -0,0 +1,71 @@
+package org.briarproject.bramble.api.data;
+
+import org.briarproject.bramble.api.Bytes;
+import org.briarproject.bramble.api.FormatException;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+
+import java.util.List;
+import java.util.Map;
+import java.util.Map.Entry;
+
+import javax.annotation.Nullable;
+
+import static org.briarproject.bramble.api.data.BdfDictionary.NULL_VALUE;
+import static org.briarproject.bramble.util.StringUtils.toHexString;
+
+@NotNullByDefault
+public class BdfStringUtils {
+
+	public static String toString(@Nullable Object o) throws FormatException {
+		return toString(o, 0);
+	}
+
+	private static String toString(@Nullable Object o, int indent)
+			throws FormatException {
+		if (o == null || o == NULL_VALUE) return "null";
+		if (o instanceof Boolean) return o.toString();
+		if (o instanceof Number) return o.toString();
+		if (o instanceof String) return "\"" + o + "\"";
+		if (o instanceof Bytes)
+			return "x" + toHexString(((Bytes) o).getBytes());
+		if (o instanceof byte[])
+			return "x" + toHexString((byte[]) o);
+		if (o instanceof List) {
+			List<?> list = (List) o;
+			StringBuilder sb = new StringBuilder();
+			sb.append("[\n");
+			int i = 0, size = list.size();
+			for (Object e : list) {
+				indent(sb, indent + 1);
+				sb.append(toString(e, indent + 1));
+				if (i++ < size - 1) sb.append(',');
+				sb.append('\n');
+			}
+			indent(sb, indent);
+			sb.append(']');
+			return sb.toString();
+		}
+		if (o instanceof Map) {
+			Map<?, ?> map = (Map) o;
+			StringBuilder sb = new StringBuilder();
+			sb.append("{\n");
+			int i = 0, size = map.size();
+			for (Entry e : map.entrySet()) {
+				indent(sb, indent + 1);
+				sb.append(toString(e.getKey(), indent + 1));
+				sb.append(": ");
+				sb.append(toString(e.getValue(), indent + 1));
+				if (i++ < size - 1) sb.append(',');
+				sb.append('\n');
+			}
+			indent(sb, indent);
+			sb.append('}');
+			return sb.toString();
+		}
+		throw new FormatException();
+	}
+
+	private static void indent(StringBuilder sb, int indent) {
+		for (int i = 0; i < indent; i++) sb.append('\t');
+	}
+}

bramble-api/src/main/java/org/briarproject/bramble/api/db/DatabaseComponent.java

@@ -76,6 +76,27 @@ public interface DatabaseComponent {
 	 */
 	void endTransaction(Transaction txn);
 
+	/**
+	 * Runs the given task within a transaction.
+	 */
+	<E extends Exception> void transaction(boolean readOnly,
+			DbRunnable<E> task) throws DbException, E;
+
+	/**
+	 * Runs the given task within a transaction and returns the result of the
+	 * task.
+	 */
+	<R, E extends Exception> R transactionWithResult(boolean readOnly,
+			DbCallable<R, E> task) throws DbException, E;
+
+	/**
+	 * Runs the given task within a transaction and returns the result of the
+	 * task, which may be null.
+	 */
+	@Nullable
+	<R, E extends Exception> R transactionWithNullableResult(boolean readOnly,
+			NullableDbCallable<R, E> task) throws DbException, E;
+
 	/**
 	 * Stores a contact associated with the given local and remote pseudonyms,
 	 * and returns an ID for the contact.
@@ -502,6 +523,12 @@ public interface DatabaseComponent {
 	void setContactActive(Transaction txn, ContactId c, boolean active)
 			throws DbException;
 
+	/**
+	 * Sets an alias name for the contact or unsets it if alias is null.
+	 */
+	void setContactAlias(Transaction txn, ContactId c, @Nullable String alias)
+			throws DbException;
+
 	/**
 	 * Sets the given group's visibility to the given contact.
 	 */

bramble-api/src/main/java/org/briarproject/bramble/api/db/DbCallable.java

@@ -0,0 +1,9 @@
+package org.briarproject.bramble.api.db;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+
+@NotNullByDefault
+public interface DbCallable<R, E extends Exception> {
+
+	R call(Transaction txn) throws DbException, E;
+}

bramble-api/src/main/java/org/briarproject/bramble/api/db/DbRunnable.java

@@ -0,0 +1,9 @@
+package org.briarproject.bramble.api.db;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+
+@NotNullByDefault
+public interface DbRunnable<E extends Exception> {
+
+	void run(Transaction txn) throws DbException, E;
+}

bramble-api/src/main/java/org/briarproject/bramble/api/db/MigrationListener.java

@@ -6,6 +6,10 @@ public interface MigrationListener {
 	 * This is called when a migration is started while opening the database.
 	 * It will be called once for each migration being applied.
 	 */
-	void onMigrationRun();
+	void onDatabaseMigration();
 
+	/**
+	 * This is called when compaction is started while opening the database.
+	 */
+	void onDatabaseCompaction();
 }

bramble-api/src/main/java/org/briarproject/bramble/api/db/NullableDbCallable.java

@@ -0,0 +1,12 @@
+package org.briarproject.bramble.api.db;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+
+import javax.annotation.Nullable;
+
+@NotNullByDefault
+public interface NullableDbCallable<R, E extends Exception> {
+
+	@Nullable
+	R call(Transaction txn) throws DbException, E;
+}

bramble-api/src/main/java/org/briarproject/bramble/api/identity/Author.java

@@ -16,10 +16,6 @@ import static org.briarproject.bramble.api.identity.AuthorConstants.MAX_PUBLIC_K
 @NotNullByDefault
 public class Author implements Nameable {
 
-	public enum Status {
-		NONE, ANONYMOUS, UNKNOWN, UNVERIFIED, VERIFIED, OURSELVES
-	}
-
 	/**
 	 * The current version of the author structure.
 	 */

bramble-api/src/main/java/org/briarproject/bramble/api/identity/AuthorInfo.java

@@ -0,0 +1,56 @@
+package org.briarproject.bramble.api.identity;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+
+import javax.annotation.Nullable;
+import javax.annotation.concurrent.Immutable;
+
+@Immutable
+@NotNullByDefault
+public class AuthorInfo {
+
+	public enum Status {
+		NONE, ANONYMOUS, UNKNOWN, UNVERIFIED, VERIFIED, OURSELVES;
+
+		public boolean isContact() {
+			return this == UNVERIFIED || this == VERIFIED;
+		}
+	}
+
+	private final Status status;
+	@Nullable
+	private final String alias;
+
+	public AuthorInfo(Status status, @Nullable String alias) {
+		this.status = status;
+		this.alias = alias;
+	}
+
+	public AuthorInfo(Status status) {
+		this(status, null);
+	}
+
+	public Status getStatus() {
+		return status;
+	}
+
+	@Nullable
+	public String getAlias() {
+		return alias;
+	}
+
+	@Override
+	public int hashCode() {
+		int hashCode = status.ordinal();
+		if (alias != null) hashCode += alias.hashCode();
+		return hashCode;
+	}
+
+	@Override
+	public boolean equals(Object o) {
+		if (!(o instanceof AuthorInfo)) return false;
+		AuthorInfo info = (AuthorInfo) o;
+		return status == info.status &&
+				(alias == null ? info.alias == null : alias.equals(info.alias));
+	}
+}

bramble-api/src/main/java/org/briarproject/bramble/api/identity/IdentityManager.java

@@ -3,7 +3,6 @@ package org.briarproject.bramble.api.identity;
 import org.briarproject.bramble.api.crypto.CryptoExecutor;
 import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.db.Transaction;
-import org.briarproject.bramble.api.identity.Author.Status;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 
 @NotNullByDefault
@@ -37,14 +36,4 @@ public interface IdentityManager {
 	 */
 	LocalAuthor getLocalAuthor(Transaction txn) throws DbException;
 
-	/**
-	 * Returns the {@link Status} of the given author.
-	 */
-	Status getAuthorStatus(AuthorId a) throws DbException;
-
-	/**
-	 * Returns the {@link Status} of the given author.
-	 */
-	Status getAuthorStatus(Transaction txn, AuthorId a) throws DbException;
-
 }

bramble-api/src/main/java/org/briarproject/bramble/api/keyagreement/KeyAgreementConstants.java

@@ -21,7 +21,7 @@ public interface KeyAgreementConstants {
 	/**
 	 * The connection timeout in milliseconds.
 	 */
-	long CONNECTION_TIMEOUT = 20 * 1000;
+	long CONNECTION_TIMEOUT = 60_000;
 
 	/**
 	 * The transport identifier for Bluetooth.

bramble-api/src/main/java/org/briarproject/bramble/api/lifecycle/LifecycleManager.java

@@ -34,7 +34,8 @@ public interface LifecycleManager {
 	 */
 	enum LifecycleState {
 
-		STARTING, MIGRATING_DATABASE, STARTING_SERVICES, RUNNING, STOPPING;
+		STARTING, MIGRATING_DATABASE, COMPACTING_DATABASE, STARTING_SERVICES,
+		RUNNING, STOPPING;
 
 		public boolean isAfter(LifecycleState state) {
 			return ordinal() > state.ordinal();

bramble-api/src/main/java/org/briarproject/bramble/api/plugin/TorConstants.java

@@ -4,7 +4,8 @@ public interface TorConstants {
 
 	TransportId ID = new TransportId("org.briarproject.bramble.tor");
 
-	String PROP_ONION = "onion";
+	String PROP_ONION_V2 = "onion";
+	String PROP_ONION_V3 = "onion3";
 
 	int SOCKS_PORT = 59050;
 	int CONTROL_PORT = 59051;

bramble-api/src/main/java/org/briarproject/bramble/api/sync/Message.java

@@ -16,6 +16,7 @@ public class Message {
 	private final byte[] body;
 
 	public Message(MessageId id, GroupId groupId, long timestamp, byte[] body) {
+		if (body.length == 0) throw new IllegalArgumentException();
 		if (body.length > MAX_MESSAGE_BODY_LENGTH)
 			throw new IllegalArgumentException();
 		this.id = id;

bramble-api/src/main/java/org/briarproject/bramble/util/StringUtils.java

@@ -47,7 +47,7 @@ public class StringUtils {
 		try {
 			return s.getBytes("UTF-8");
 		} catch (UnsupportedEncodingException e) {
-			throw new RuntimeException(e);
+			throw new AssertionError(e);
 		}
 	}
 
@@ -63,7 +63,7 @@ public class StringUtils {
 		try {
 			return decoder.decode(buffer).toString();
 		} catch (CharacterCodingException e) {
-			throw new RuntimeException(e);
+			throw new AssertionError(e);
 		}
 	}
 

bramble-api/src/test/java/org/briarproject/bramble/api/identity/AuthorInfoTest.java

@@ -0,0 +1,42 @@
+package org.briarproject.bramble.api.identity;
+
+import org.briarproject.bramble.test.BrambleTestCase;
+import org.junit.Test;
+
+import static org.briarproject.bramble.api.identity.AuthorInfo.Status.NONE;
+import static org.briarproject.bramble.api.identity.AuthorInfo.Status.VERIFIED;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotEquals;
+
+public class AuthorInfoTest extends BrambleTestCase {
+
+	@Test
+	public void testEquals() {
+		assertEquals(
+				new AuthorInfo(NONE),
+				new AuthorInfo(NONE, null)
+		);
+		assertEquals(
+				new AuthorInfo(NONE, "test"),
+				new AuthorInfo(NONE, "test")
+		);
+
+		assertNotEquals(
+				new AuthorInfo(NONE),
+				new AuthorInfo(VERIFIED)
+		);
+		assertNotEquals(
+				new AuthorInfo(NONE, "test"),
+				new AuthorInfo(NONE)
+		);
+		assertNotEquals(
+				new AuthorInfo(NONE),
+				new AuthorInfo(NONE, "test")
+		);
+		assertNotEquals(
+				new AuthorInfo(NONE, "a"),
+				new AuthorInfo(NONE, "b")
+		);
+	}
+
+}

bramble-api/src/test/java/org/briarproject/bramble/test/SettableClock.java

@@ -0,0 +1,24 @@
+package org.briarproject.bramble.test;
+
+import org.briarproject.bramble.api.system.Clock;
+
+import java.util.concurrent.atomic.AtomicLong;
+
+public class SettableClock implements Clock {
+
+	private final AtomicLong time;
+
+	public SettableClock(AtomicLong time) {
+		this.time = time;
+	}
+
+	@Override
+	public long currentTimeMillis() {
+		return time.get();
+	}
+
+	@Override
+	public void sleep(long milliseconds) throws InterruptedException {
+		Thread.sleep(milliseconds);
+	}
+}

bramble-api/witness.gradle

@@ -2,7 +2,7 @@ dependencyVerification {
     verify = [
         'cglib:cglib:3.2.0:cglib-3.2.0.jar:adb13bab79712ad6bdf1bd59f2a3918018a8016e722e8a357065afb9e6690861',
         'com.google.code.findbugs:jsr305:3.0.2:jsr305-3.0.2.jar:766ad2a0783f2687962c8ad74ceecc38a28b9f72a2d085ee438b7813e928d0c7',
-        'com.google.dagger:dagger:2.0.2:dagger-2.0.2.jar:84c0282ed8be73a29e0475d639da030b55dee72369e58dd35ae7d4fe6243dcf9',
+        'com.google.dagger:dagger:2.19:dagger-2.19.jar:514b6f1e0727c6572e1d65cb27e4ae668b7aeaeb93a29515182965265b609939',
         'javax.inject:javax.inject:1:javax.inject-1.jar:91c77044a50c481636c32d916fd89c9118a72195390452c81065080f957de7ff',
         'junit:junit:4.12:junit-4.12.jar:59721f0805e223d84b90677887d9ff567dc534d7c502ca903c0c2b17f05c116a',
         'org.apache.ant:ant-launcher:1.9.4:ant-launcher-1.9.4.jar:7bccea20b41801ca17bcbc909a78c835d0f443f12d639c77bd6ae3d05861608d',

bramble-core/build.gradle

@@ -3,10 +3,10 @@ sourceCompatibility = 1.8
 targetCompatibility = 1.8
 
 apply plugin: 'ru.vyarus.animalsniffer'
-apply plugin: 'net.ltgt.apt'
 apply plugin: 'idea'
 apply plugin: 'witness'
 apply from: 'witness.gradle'
+apply from: '../dagger.gradle'
 
 dependencies {
 	implementation project(path: ':bramble-api', configuration: 'default')
@@ -14,10 +14,10 @@ dependencies {
 	implementation 'com.h2database:h2:1.4.192' // The last version that supports Java 1.6
 	implementation 'org.bitlet:weupnp:0.1.4'
 	implementation 'net.i2p.crypto:eddsa:0.2.0'
-	implementation 'org.whispersystems:curve25519-java:0.4.1'
+	implementation 'org.whispersystems:curve25519-java:0.5.0'
 	implementation 'org.briarproject:jtorctl:0.3'
 
-	apt 'com.google.dagger:dagger-compiler:2.0.2'
+	annotationProcessor 'com.google.dagger:dagger-compiler:2.19'
 
 	testImplementation project(path: ':bramble-api', configuration: 'testOutput')
 	testImplementation 'org.hsqldb:hsqldb:2.3.5' // The last version that supports Java 1.6
@@ -25,10 +25,8 @@ dependencies {
 	testImplementation "org.jmock:jmock:2.8.2"
 	testImplementation "org.jmock:jmock-junit4:2.8.2"
 	testImplementation "org.jmock:jmock-legacy:2.8.2"
-	testImplementation "org.hamcrest:hamcrest-library:1.3"
-	testImplementation "org.hamcrest:hamcrest-core:1.3"
 
-	testApt 'com.google.dagger:dagger-compiler:2.0.2'
+	testAnnotationProcessor 'com.google.dagger:dagger-compiler:2.19'
 
 	signature 'org.codehaus.mojo.signature:java16:1.1@signature'
 }

bramble-core/src/main/java/org/briarproject/bramble/account/AccountManagerImpl.java

@@ -159,7 +159,8 @@ class AccountManagerImpl implements AccountManager {
 	@Override
 	public boolean createAccount(String name, String password) {
 		synchronized (stateChangeLock) {
-			// TODO don't allow creating another account if one already exists
+			if (hasDatabaseKey())
+				throw new AssertionError("Already have a database key");
 			LocalAuthor localAuthor = identityManager.createLocalAuthor(name);
 			identityManager.registerLocalAuthor(localAuthor);
 			SecretKey key = crypto.generateSecretKey();
@@ -182,6 +183,7 @@ class AccountManagerImpl implements AccountManager {
 			LOG.info("Deleting account");
 			IoUtils.deleteFileOrDir(databaseConfig.getDatabaseKeyDirectory());
 			IoUtils.deleteFileOrDir(databaseConfig.getDatabaseDirectory());
+			databaseKey = null;
 		}
 	}
 

bramble-core/src/main/java/org/briarproject/bramble/battery/DefaultBatteryManagerModule.java

@@ -0,0 +1,19 @@
+package org.briarproject.bramble.battery;
+
+import org.briarproject.bramble.api.battery.BatteryManager;
+
+import dagger.Module;
+import dagger.Provides;
+
+/**
+ * Provides a default implementation of {@link BatteryManager} for systems
+ * without batteries.
+ */
+@Module
+public class DefaultBatteryManagerModule {
+
+	@Provides
+	BatteryManager provideBatteryManager() {
+		return () -> false;
+	}
+}

bramble-core/src/main/java/org/briarproject/bramble/client/ClientHelperImpl.java

@@ -82,13 +82,7 @@ class ClientHelperImpl implements ClientHelper {
 	@Override
 	public void addLocalMessage(Message m, BdfDictionary metadata,
 			boolean shared) throws DbException, FormatException {
-		Transaction txn = db.startTransaction(false);
-		try {
-			addLocalMessage(txn, m, metadata, shared);
-			db.commitTransaction(txn);
-		} finally {
-			db.endTransaction(txn);
-		}
+		db.transaction(false, txn -> addLocalMessage(txn, m, metadata, shared));
 	}
 
 	@Override
@@ -113,15 +107,7 @@ class ClientHelperImpl implements ClientHelper {
 
 	@Override
 	public Message getMessage(MessageId m) throws DbException {
-		Message message;
-		Transaction txn = db.startTransaction(true);
-		try {
-			message = getMessage(txn, m);
-			db.commitTransaction(txn);
-		} finally {
-			db.endTransaction(txn);
-		}
-		return message;
+		return db.transactionWithResult(true, txn -> getMessage(txn, m));
 	}
 
 	@Override
@@ -132,15 +118,7 @@ class ClientHelperImpl implements ClientHelper {
 	@Override
 	public BdfList getMessageAsList(MessageId m) throws DbException,
 			FormatException {
-		BdfList list;
-		Transaction txn = db.startTransaction(true);
-		try {
-			list = getMessageAsList(txn, m);
-			db.commitTransaction(txn);
-		} finally {
-			db.endTransaction(txn);
-		}
-		return list;
+		return db.transactionWithResult(true, txn -> getMessageAsList(txn, m));
 	}
 
 	@Override
@@ -152,15 +130,8 @@ class ClientHelperImpl implements ClientHelper {
 	@Override
 	public BdfDictionary getGroupMetadataAsDictionary(GroupId g)
 			throws DbException, FormatException {
-		BdfDictionary dictionary;
-		Transaction txn = db.startTransaction(true);
-		try {
-			dictionary = getGroupMetadataAsDictionary(txn, g);
-			db.commitTransaction(txn);
-		} finally {
-			db.endTransaction(txn);
-		}
-		return dictionary;
+		return db.transactionWithResult(true, txn ->
+				getGroupMetadataAsDictionary(txn, g));
 	}
 
 	@Override
@@ -173,15 +144,8 @@ class ClientHelperImpl implements ClientHelper {
 	@Override
 	public BdfDictionary getMessageMetadataAsDictionary(MessageId m)
 			throws DbException, FormatException {
-		BdfDictionary dictionary;
-		Transaction txn = db.startTransaction(true);
-		try {
-			dictionary = getMessageMetadataAsDictionary(txn, m);
-			db.commitTransaction(txn);
-		} finally {
-			db.endTransaction(txn);
-		}
-		return dictionary;
+		return db.transactionWithResult(true, txn ->
+				getMessageMetadataAsDictionary(txn, m));
 	}
 
 	@Override
@@ -194,15 +158,8 @@ class ClientHelperImpl implements ClientHelper {
 	@Override
 	public Map<MessageId, BdfDictionary> getMessageMetadataAsDictionary(
 			GroupId g) throws DbException, FormatException {
-		Map<MessageId, BdfDictionary> map;
-		Transaction txn = db.startTransaction(true);
-		try {
-			map = getMessageMetadataAsDictionary(txn, g);
-			db.commitTransaction(txn);
-		} finally {
-			db.endTransaction(txn);
-		}
-		return map;
+		return db.transactionWithResult(true, txn ->
+				getMessageMetadataAsDictionary(txn, g));
 	}
 
 	@Override
@@ -219,15 +176,8 @@ class ClientHelperImpl implements ClientHelper {
 	public Map<MessageId, BdfDictionary> getMessageMetadataAsDictionary(
 			GroupId g, BdfDictionary query) throws DbException,
 			FormatException {
-		Map<MessageId, BdfDictionary> map;
-		Transaction txn = db.startTransaction(true);
-		try {
-			map = getMessageMetadataAsDictionary(txn, g, query);
-			db.commitTransaction(txn);
-		} finally {
-			db.endTransaction(txn);
-		}
-		return map;
+		return db.transactionWithResult(true, txn ->
+				getMessageMetadataAsDictionary(txn, g, query));
 	}
 
 	@Override
@@ -245,13 +195,7 @@ class ClientHelperImpl implements ClientHelper {
 	@Override
 	public void mergeGroupMetadata(GroupId g, BdfDictionary metadata)
 			throws DbException, FormatException {
-		Transaction txn = db.startTransaction(false);
-		try {
-			mergeGroupMetadata(txn, g, metadata);
-			db.commitTransaction(txn);
-		} finally {
-			db.endTransaction(txn);
-		}
+		db.transaction(false, txn -> mergeGroupMetadata(txn, g, metadata));
 	}
 
 	@Override
@@ -263,13 +207,7 @@ class ClientHelperImpl implements ClientHelper {
 	@Override
 	public void mergeMessageMetadata(MessageId m, BdfDictionary metadata)
 			throws DbException, FormatException {
-		Transaction txn = db.startTransaction(false);
-		try {
-			mergeMessageMetadata(txn, m, metadata);
-			db.commitTransaction(txn);
-		} finally {
-			db.endTransaction(txn);
-		}
+		db.transaction(false, txn -> mergeMessageMetadata(txn, m, metadata));
 	}
 
 	@Override

bramble-core/src/main/java/org/briarproject/bramble/contact/ContactExchangeTaskImpl.java

@@ -13,7 +13,6 @@ import org.briarproject.bramble.api.data.BdfList;
 import org.briarproject.bramble.api.db.ContactExistsException;
 import org.briarproject.bramble.api.db.DatabaseComponent;
 import org.briarproject.bramble.api.db.DbException;
-import org.briarproject.bramble.api.db.Transaction;
 import org.briarproject.bramble.api.identity.Author;
 import org.briarproject.bramble.api.identity.LocalAuthor;
 import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
@@ -158,7 +157,8 @@ class ContactExchangeTaskImpl extends Thread implements ContactExchangeTask {
 				streamWriterFactory.createContactExchangeStreamWriter(out,
 						alice ? aliceHeaderKey : bobHeaderKey);
 		RecordWriter recordWriter =
-				recordWriterFactory.createRecordWriter(streamWriter.getOutputStream());
+				recordWriterFactory
+						.createRecordWriter(streamWriter.getOutputStream());
 
 		// Derive the nonces to be signed
 		byte[] aliceNonce = crypto.mac(ALICE_NONCE_LABEL, masterSecret,
@@ -287,19 +287,14 @@ class ContactExchangeTaskImpl extends Thread implements ContactExchangeTask {
 	private ContactId addContact(Author remoteAuthor, long timestamp,
 			Map<TransportId, TransportProperties> remoteProperties)
 			throws DbException {
-		ContactId contactId;
-		Transaction txn = db.startTransaction(false);
-		try {
-			contactId = contactManager.addContact(txn, remoteAuthor,
+		return db.transactionWithResult(false, txn -> {
+			ContactId contactId = contactManager.addContact(txn, remoteAuthor,
 					localAuthor.getId(), masterSecret, timestamp, alice,
 					true, true);
 			transportPropertyManager.addRemoteProperties(txn, contactId,
 					remoteProperties);
-			db.commitTransaction(txn);
-		} finally {
-			db.endTransaction(txn);
-		}
-		return contactId;
+			return contactId;
+		});
 	}
 
 	private void tryToClose(DuplexTransportConnection conn) {

bramble-core/src/main/java/org/briarproject/bramble/contact/ContactManagerImpl.java

@@ -10,6 +10,9 @@ import org.briarproject.bramble.api.db.NoSuchContactException;
 import org.briarproject.bramble.api.db.Transaction;
 import org.briarproject.bramble.api.identity.Author;
 import org.briarproject.bramble.api.identity.AuthorId;
+import org.briarproject.bramble.api.identity.AuthorInfo;
+import org.briarproject.bramble.api.identity.IdentityManager;
+import org.briarproject.bramble.api.identity.LocalAuthor;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.transport.KeyManager;
 
@@ -18,21 +21,32 @@ import java.util.Collection;
 import java.util.List;
 import java.util.concurrent.CopyOnWriteArrayList;
 
+import javax.annotation.Nullable;
 import javax.annotation.concurrent.ThreadSafe;
 import javax.inject.Inject;
 
+import static org.briarproject.bramble.api.identity.AuthorConstants.MAX_AUTHOR_NAME_LENGTH;
+import static org.briarproject.bramble.api.identity.AuthorInfo.Status.OURSELVES;
+import static org.briarproject.bramble.api.identity.AuthorInfo.Status.UNKNOWN;
+import static org.briarproject.bramble.api.identity.AuthorInfo.Status.UNVERIFIED;
+import static org.briarproject.bramble.api.identity.AuthorInfo.Status.VERIFIED;
+import static org.briarproject.bramble.util.StringUtils.toUtf8;
+
 @ThreadSafe
 @NotNullByDefault
 class ContactManagerImpl implements ContactManager {
 
 	private final DatabaseComponent db;
 	private final KeyManager keyManager;
+	private final IdentityManager identityManager;
 	private final List<ContactHook> hooks;
 
 	@Inject
-	ContactManagerImpl(DatabaseComponent db, KeyManager keyManager) {
+	ContactManagerImpl(DatabaseComponent db, KeyManager keyManager,
+			IdentityManager identityManager) {
 		this.db = db;
 		this.keyManager = keyManager;
+		this.identityManager = identityManager;
 		hooks = new CopyOnWriteArrayList<>();
 	}
 
@@ -65,42 +79,21 @@ class ContactManagerImpl implements ContactManager {
 	public ContactId addContact(Author remote, AuthorId local, SecretKey master,
 			long timestamp, boolean alice, boolean verified, boolean active)
 			throws DbException {
-		ContactId c;
-		Transaction txn = db.startTransaction(false);
-		try {
-			c = addContact(txn, remote, local, master, timestamp, alice,
-					verified, active);
-			db.commitTransaction(txn);
-		} finally {
-			db.endTransaction(txn);
-		}
-		return c;
+		return db.transactionWithResult(false, txn ->
+				addContact(txn, remote, local, master, timestamp, alice,
+						verified, active));
 	}
 
 	@Override
 	public Contact getContact(ContactId c) throws DbException {
-		Contact contact;
-		Transaction txn = db.startTransaction(true);
-		try {
-			contact = db.getContact(txn, c);
-			db.commitTransaction(txn);
-		} finally {
-			db.endTransaction(txn);
-		}
-		return contact;
+		return db.transactionWithResult(true, txn -> db.getContact(txn, c));
 	}
 
 	@Override
 	public Contact getContact(AuthorId remoteAuthorId, AuthorId localAuthorId)
 			throws DbException {
-		Transaction txn = db.startTransaction(true);
-		try {
-			Contact c = getContact(txn, remoteAuthorId, localAuthorId);
-			db.commitTransaction(txn);
-			return c;
-		} finally {
-			db.endTransaction(txn);
-		}
+		return db.transactionWithResult(true, txn ->
+				getContact(txn, remoteAuthorId, localAuthorId));
 	}
 
 	@Override
@@ -118,14 +111,8 @@ class ContactManagerImpl implements ContactManager {
 
 	@Override
 	public Collection<Contact> getActiveContacts() throws DbException {
-		Collection<Contact> contacts;
-		Transaction txn = db.startTransaction(true);
-		try {
-			contacts = db.getContacts(txn);
-			db.commitTransaction(txn);
-		} finally {
-			db.endTransaction(txn);
-		}
+		Collection<Contact> contacts =
+				db.transactionWithResult(true, db::getContacts);
 		List<Contact> active = new ArrayList<>(contacts.size());
 		for (Contact c : contacts) if (c.isActive()) active.add(c);
 		return active;
@@ -133,13 +120,7 @@ class ContactManagerImpl implements ContactManager {
 
 	@Override
 	public void removeContact(ContactId c) throws DbException {
-		Transaction txn = db.startTransaction(false);
-		try {
-			removeContact(txn, c);
-			db.commitTransaction(txn);
-		} finally {
-			db.endTransaction(txn);
-		}
+		db.transaction(false, txn -> removeContact(txn, c));
 	}
 
 	@Override
@@ -148,6 +129,23 @@ class ContactManagerImpl implements ContactManager {
 		db.setContactActive(txn, c, active);
 	}
 
+	@Override
+	public void setContactAlias(Transaction txn, ContactId c,
+			@Nullable String alias) throws DbException {
+		if (alias != null) {
+			int aliasLength = toUtf8(alias).length;
+			if (aliasLength == 0 || aliasLength > MAX_AUTHOR_NAME_LENGTH)
+				throw new IllegalArgumentException();
+		}
+		db.setContactAlias(txn, c, alias);
+	}
+
+	@Override
+	public void setContactAlias(ContactId c, @Nullable String alias)
+			throws DbException {
+		db.transaction(false, txn -> setContactAlias(txn, c, alias));
+	}
+
 	@Override
 	public boolean contactExists(Transaction txn, AuthorId remoteAuthorId,
 			AuthorId localAuthorId) throws DbException {
@@ -157,15 +155,8 @@ class ContactManagerImpl implements ContactManager {
 	@Override
 	public boolean contactExists(AuthorId remoteAuthorId,
 			AuthorId localAuthorId) throws DbException {
-		boolean exists;
-		Transaction txn = db.startTransaction(true);
-		try {
-			exists = contactExists(txn, remoteAuthorId, localAuthorId);
-			db.commitTransaction(txn);
-		} finally {
-			db.endTransaction(txn);
-		}
-		return exists;
+		return db.transactionWithResult(true, txn ->
+				contactExists(txn, remoteAuthorId, localAuthorId));
 	}
 
 	@Override
@@ -176,4 +167,23 @@ class ContactManagerImpl implements ContactManager {
 		db.removeContact(txn, c);
 	}
 
+	@Override
+	public AuthorInfo getAuthorInfo(AuthorId a) throws DbException {
+		return db.transactionWithResult(true, txn -> getAuthorInfo(txn, a));
+	}
+
+	@Override
+	public AuthorInfo getAuthorInfo(Transaction txn, AuthorId authorId)
+			throws DbException {
+		LocalAuthor localAuthor = identityManager.getLocalAuthor(txn);
+		if (localAuthor.getId().equals(authorId))
+			return new AuthorInfo(OURSELVES);
+		Collection<Contact> contacts = db.getContactsByAuthorId(txn, authorId);
+		if (contacts.isEmpty()) return new AuthorInfo(UNKNOWN);
+		if (contacts.size() > 1) throw new AssertionError();
+		Contact c = contacts.iterator().next();
+		if (c.isVerified()) return new AuthorInfo(VERIFIED, c.getAlias());
+		else return new AuthorInfo(UNVERIFIED, c.getAlias());
+	}
+
 }

bramble-core/src/main/java/org/briarproject/bramble/data/BdfReaderImpl.java

@@ -29,6 +29,7 @@ import static org.briarproject.bramble.data.Types.STRING_16;
 import static org.briarproject.bramble.data.Types.STRING_32;
 import static org.briarproject.bramble.data.Types.STRING_8;
 import static org.briarproject.bramble.data.Types.TRUE;
+import static org.briarproject.bramble.util.StringUtils.fromUtf8;
 
 @NotThreadSafe
 @NotNullByDefault
@@ -253,7 +254,7 @@ class BdfReaderImpl implements BdfReader {
 		if (length < 0 || length > maxBufferSize) throw new FormatException();
 		if (length == 0) return "";
 		readIntoBuffer(length);
-		return new String(buf, 0, length, "UTF-8");
+		return fromUtf8(buf, 0, length);
 	}
 
 	private int readStringLength() throws IOException {

bramble-core/src/main/java/org/briarproject/bramble/db/Database.java

@@ -616,6 +616,12 @@ interface Database<T> {
 	void setContactActive(T txn, ContactId c, boolean active)
 			throws DbException;
 
+	/**
+	 * Sets an alias name for a contact.
+	 */
+	void setContactAlias(T txn, ContactId c, @Nullable String alias)
+			throws DbException;
+
 	/**
 	 * Sets the given group's visibility to the given contact to either
 	 * {@link Visibility VISIBLE} or {@link Visibility SHARED}.

bramble-core/src/main/java/org/briarproject/bramble/db/DatabaseComponentImpl.java

@@ -9,7 +9,9 @@ import org.briarproject.bramble.api.contact.event.ContactVerifiedEvent;
 import org.briarproject.bramble.api.crypto.SecretKey;
 import org.briarproject.bramble.api.db.ContactExistsException;
 import org.briarproject.bramble.api.db.DatabaseComponent;
+import org.briarproject.bramble.api.db.DbCallable;
 import org.briarproject.bramble.api.db.DbException;
+import org.briarproject.bramble.api.db.DbRunnable;
 import org.briarproject.bramble.api.db.Metadata;
 import org.briarproject.bramble.api.db.MigrationListener;
 import org.briarproject.bramble.api.db.NoSuchContactException;
@@ -17,6 +19,7 @@ import org.briarproject.bramble.api.db.NoSuchGroupException;
 import org.briarproject.bramble.api.db.NoSuchLocalAuthorException;
 import org.briarproject.bramble.api.db.NoSuchMessageException;
 import org.briarproject.bramble.api.db.NoSuchTransportException;
+import org.briarproject.bramble.api.db.NullableDbCallable;
 import org.briarproject.bramble.api.db.Transaction;
 import org.briarproject.bramble.api.event.Event;
 import org.briarproject.bramble.api.event.EventBus;
@@ -166,6 +169,45 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 			for (Event e : transaction.getEvents()) eventBus.broadcast(e);
 	}
 
+	@Override
+	public <E extends Exception> void transaction(boolean readOnly,
+			DbRunnable<E> task) throws DbException, E {
+		Transaction txn = startTransaction(readOnly);
+		try {
+			task.run(txn);
+			commitTransaction(txn);
+		} finally {
+			endTransaction(txn);
+		}
+	}
+
+	@Override
+	public <R, E extends Exception> R transactionWithResult(boolean readOnly,
+			DbCallable<R, E> task) throws DbException, E {
+		Transaction txn = startTransaction(readOnly);
+		try {
+			R result = task.call(txn);
+			commitTransaction(txn);
+			return result;
+		} finally {
+			endTransaction(txn);
+		}
+	}
+
+	@Override
+	public <R, E extends Exception> R transactionWithNullableResult(
+			boolean readOnly, NullableDbCallable<R, E> task)
+			throws DbException, E {
+		Transaction txn = startTransaction(readOnly);
+		try {
+			R result = task.call(txn);
+			commitTransaction(txn);
+			return result;
+		} finally {
+			endTransaction(txn);
+		}
+	}
+
 	private T unbox(Transaction transaction) {
 		if (transaction.isCommitted()) throw new IllegalStateException();
 		return txnClass.cast(transaction.unbox());
@@ -832,6 +874,16 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 		transaction.attach(new ContactStatusChangedEvent(c, active));
 	}
 
+	@Override
+	public void setContactAlias(Transaction transaction, ContactId c,
+			@Nullable String alias) throws DbException {
+		if (transaction.isReadOnly()) throw new IllegalArgumentException();
+		T txn = unbox(transaction);
+		if (!db.containsContact(txn, c))
+			throw new NoSuchContactException();
+		db.setContactAlias(txn, c, alias);
+	}
+
 	@Override
 	public void setGroupVisibility(Transaction transaction, ContactId c,
 			GroupId g, Visibility v) throws DbException {

bramble-core/src/main/java/org/briarproject/bramble/db/DatabaseConstants.java

@@ -2,6 +2,8 @@ package org.briarproject.bramble.db;
 
 import org.briarproject.bramble.api.settings.Settings;
 
+import static java.util.concurrent.TimeUnit.DAYS;
+
 interface DatabaseConstants {
 
 	/**
@@ -23,4 +25,16 @@ interface DatabaseConstants {
 	 */
 	String SCHEMA_VERSION_KEY = "schemaVersion";
 
+	/**
+	 * The {@link Settings} key under which the time of the last database
+	 * compaction is stored.
+	 */
+	String LAST_COMPACTED_KEY = "lastCompacted";
+
+	/**
+	 * The maximum time between database compactions in milliseconds. When the
+	 * database is opened it will be compacted if more than this amount of time
+	 * has passed since the last compaction.
+	 */
+	long MAX_COMPACTION_INTERVAL_MS = DAYS.toMillis(30);
 }

bramble-core/src/main/java/org/briarproject/bramble/db/DatabaseTypes.java

@@ -0,0 +1,34 @@
+package org.briarproject.bramble.db;
+
+class DatabaseTypes {
+
+	private final String hashType, secretType, binaryType;
+	private final String counterType, stringType;
+
+	public DatabaseTypes(String hashType, String secretType, String binaryType,
+			String counterType, String stringType) {
+		this.hashType = hashType;
+		this.secretType = secretType;
+		this.binaryType = binaryType;
+		this.counterType = counterType;
+		this.stringType = stringType;
+	}
+
+	/**
+	 * Replaces database type placeholders in a statement with the actual types.
+	 * These placeholders are currently supported:
+	 * <li> _HASH
+	 * <li> _SECRET
+	 * <li> _BINARY
+	 * <li> _COUNTER
+	 * <li> _STRING
+	 */
+	String replaceTypes(String s) {
+		s = s.replaceAll("_HASH", hashType);
+		s = s.replaceAll("_SECRET", secretType);
+		s = s.replaceAll("_BINARY", binaryType);
+		s = s.replaceAll("_COUNTER", counterType);
+		s = s.replaceAll("_STRING", stringType);
+		return s;
+	}
+}

bramble-core/src/main/java/org/briarproject/bramble/db/H2Database.java

@@ -13,6 +13,7 @@ import java.io.File;
 import java.sql.Connection;
 import java.sql.DriverManager;
 import java.sql.SQLException;
+import java.sql.Statement;
 import java.util.Properties;
 
 import javax.annotation.Nullable;
@@ -29,6 +30,8 @@ class H2Database extends JdbcDatabase {
 	private static final String BINARY_TYPE = "BINARY";
 	private static final String COUNTER_TYPE = "INT NOT NULL AUTO_INCREMENT";
 	private static final String STRING_TYPE = "VARCHAR";
+	private static final DatabaseTypes dbTypes = new DatabaseTypes(HASH_TYPE,
+			SECRET_TYPE, BINARY_TYPE, COUNTER_TYPE, STRING_TYPE);
 
 	private final DatabaseConfig config;
 	private final String url;
@@ -39,8 +42,7 @@ class H2Database extends JdbcDatabase {
 	@Inject
 	H2Database(DatabaseConfig config, MessageFactory messageFactory,
 			Clock clock) {
-		super(HASH_TYPE, SECRET_TYPE, BINARY_TYPE, COUNTER_TYPE, STRING_TYPE,
-				messageFactory, clock);
+		super(dbTypes, messageFactory, clock);
 		this.config = config;
 		File dir = config.getDatabaseDirectory();
 		String path = new File(dir, "db").getAbsolutePath();
@@ -106,4 +108,22 @@ class H2Database extends JdbcDatabase {
 	String getUrl() {
 		return url;
 	}
+
+	@Override
+	protected void compactAndClose() throws DbException {
+		Connection c = null;
+		Statement s = null;
+		try {
+			c = createConnection();
+			closeAllConnections();
+			s = c.createStatement();
+			s.execute("SHUTDOWN COMPACT");
+			s.close();
+			c.close();
+		} catch (SQLException e) {
+			tryToClose(s);
+			tryToClose(c);
+			throw new DbException(e);
+		}
+	}
 }

bramble-core/src/main/java/org/briarproject/bramble/db/HyperSqlDatabase.java

@@ -30,6 +30,8 @@ class HyperSqlDatabase extends JdbcDatabase {
 	private static final String COUNTER_TYPE =
 			"INTEGER NOT NULL GENERATED ALWAYS AS IDENTITY(START WITH 1)";
 	private static final String STRING_TYPE = "VARCHAR";
+	private static final DatabaseTypes dbTypes = new DatabaseTypes(HASH_TYPE,
+			SECRET_TYPE, BINARY_TYPE, COUNTER_TYPE, STRING_TYPE);
 
 	private final DatabaseConfig config;
 	private final String url;
@@ -40,8 +42,7 @@ class HyperSqlDatabase extends JdbcDatabase {
 	@Inject
 	HyperSqlDatabase(DatabaseConfig config, MessageFactory messageFactory,
 			Clock clock) {
-		super(HASH_TYPE, SECRET_TYPE, BINARY_TYPE, COUNTER_TYPE, STRING_TYPE,
-				messageFactory, clock);
+		super(dbTypes, messageFactory, clock);
 		this.config = config;
 		File dir = config.getDatabaseDirectory();
 		String path = new File(dir, "db").getAbsolutePath();
@@ -61,20 +62,24 @@ class HyperSqlDatabase extends JdbcDatabase {
 
 	@Override
 	public void close() throws DbException {
+		Connection c = null;
+		Statement s = null;
 		try {
 			super.closeAllConnections();
-			Connection c = createConnection();
-			Statement s = c.createStatement();
+			c = createConnection();
+			s = c.createStatement();
 			s.executeQuery("SHUTDOWN");
 			s.close();
 			c.close();
 		} catch (SQLException e) {
+			tryToClose(s);
+			tryToClose(c);
 			throw new DbException(e);
 		}
 	}
 
 	@Override
-	public long getFreeSpace() throws DbException {
+	public long getFreeSpace() {
 		File dir = config.getDatabaseDirectory();
 		long maxSize = config.getMaxSize();
 		long free = dir.getFreeSpace();
@@ -104,4 +109,22 @@ class HyperSqlDatabase extends JdbcDatabase {
 		String hex = StringUtils.toHexString(key.getBytes());
 		return DriverManager.getConnection(url + ";crypt_key=" + hex);
 	}
+
+	@Override
+	protected void compactAndClose() throws DbException {
+		Connection c = null;
+		Statement s = null;
+		try {
+			super.closeAllConnections();
+			c = createConnection();
+			s = c.createStatement();
+			s.executeQuery("SHUTDOWN COMPACT");
+			s.close();
+			c.close();
+		} catch (SQLException e) {
+			tryToClose(s);
+			tryToClose(c);
+			throw new DbException(e);
+		}
+	}
 }

bramble-core/src/main/java/org/briarproject/bramble/db/JdbcDatabase.java

@@ -56,6 +56,7 @@ import java.util.logging.Logger;
 import javax.annotation.Nullable;
 
 import static java.sql.Types.INTEGER;
+import static java.sql.Types.VARCHAR;
 import static java.util.logging.Level.INFO;
 import static java.util.logging.Level.WARNING;
 import static org.briarproject.bramble.api.db.Metadata.REMOVE;
@@ -67,9 +68,13 @@ import static org.briarproject.bramble.api.sync.ValidationManager.State.DELIVERE
 import static org.briarproject.bramble.api.sync.ValidationManager.State.PENDING;
 import static org.briarproject.bramble.api.sync.ValidationManager.State.UNKNOWN;
 import static org.briarproject.bramble.db.DatabaseConstants.DB_SETTINGS_NAMESPACE;
+import static org.briarproject.bramble.db.DatabaseConstants.LAST_COMPACTED_KEY;
+import static org.briarproject.bramble.db.DatabaseConstants.MAX_COMPACTION_INTERVAL_MS;
 import static org.briarproject.bramble.db.DatabaseConstants.SCHEMA_VERSION_KEY;
 import static org.briarproject.bramble.db.ExponentialBackoff.calculateExpiry;
+import static org.briarproject.bramble.util.LogUtils.logDuration;
 import static org.briarproject.bramble.util.LogUtils.logException;
+import static org.briarproject.bramble.util.LogUtils.now;
 
 /**
  * A generic database implementation that can be used with any JDBC-compatible
@@ -79,7 +84,7 @@ import static org.briarproject.bramble.util.LogUtils.logException;
 abstract class JdbcDatabase implements Database<Connection> {
 
 	// Package access for testing
-	static final int CODE_SCHEMA_VERSION = 40;
+	static final int CODE_SCHEMA_VERSION = 41;
 
 	// Rotation period offsets for incoming transport keys
 	private static final int OFFSET_PREV = -1;
@@ -109,6 +114,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 					+ " authorId _HASH NOT NULL,"
 					+ " formatVersion INT NOT NULL,"
 					+ " name _STRING NOT NULL,"
+					+ " alias _STRING," // Null if no alias exists
 					+ " publicKey _BINARY NOT NULL,"
 					+ " localAuthorId _HASH NOT NULL,"
 					+ " verified BOOLEAN NOT NULL,"
@@ -306,10 +312,9 @@ abstract class JdbcDatabase implements Database<Connection> {
 			Logger.getLogger(JdbcDatabase.class.getName());
 
 	// Different database libraries use different names for certain types
-	private final String hashType, secretType, binaryType;
-	private final String counterType, stringType;
 	private final MessageFactory messageFactory;
 	private final Clock clock;
+	private final DatabaseTypes dbTypes;
 
 	// Locking: connectionsLock
 	private final LinkedList<Connection> connections = new LinkedList<>();
@@ -317,20 +322,16 @@ abstract class JdbcDatabase implements Database<Connection> {
 	private int openConnections = 0; // Locking: connectionsLock
 	private boolean closed = false; // Locking: connectionsLock
 
-	@Nullable
 	protected abstract Connection createConnection() throws SQLException;
 
+	protected abstract void compactAndClose() throws DbException;
+
 	private final Lock connectionsLock = new ReentrantLock();
 	private final Condition connectionsChanged = connectionsLock.newCondition();
 
-	JdbcDatabase(String hashType, String secretType, String binaryType,
-			String counterType, String stringType,
-			MessageFactory messageFactory, Clock clock) {
-		this.hashType = hashType;
-		this.secretType = secretType;
-		this.binaryType = binaryType;
-		this.counterType = counterType;
-		this.stringType = stringType;
+	JdbcDatabase(DatabaseTypes databaseTypes, MessageFactory messageFactory,
+			Clock clock) {
+		this.dbTypes = databaseTypes;
 		this.messageFactory = messageFactory;
 		this.clock = clock;
 	}
@@ -344,13 +345,16 @@ abstract class JdbcDatabase implements Database<Connection> {
 			throw new DbException(e);
 		}
 		// Open the database and create the tables and indexes if necessary
+		boolean compact;
 		Connection txn = startTransaction();
 		try {
 			if (reopen) {
-				checkSchemaVersion(txn, listener);
+				Settings s = getSettings(txn, DB_SETTINGS_NAMESPACE);
+				compact = migrateSchema(txn, s, listener) || isCompactionDue(s);
 			} else {
 				createTables(txn);
-				storeSchemaVersion(txn, CODE_SCHEMA_VERSION);
+				initialiseSettings(txn);
+				compact = false;
 			}
 			createIndexes(txn);
 			commitTransaction(txn);
@@ -358,6 +362,25 @@ abstract class JdbcDatabase implements Database<Connection> {
 			abortTransaction(txn);
 			throw e;
 		}
+		// Compact the database if necessary
+		if (compact) {
+			if (listener != null) listener.onDatabaseCompaction();
+			long start = now();
+			compactAndClose();
+			logDuration(LOG, "Compacting database", start);
+			// Allow the next transaction to reopen the DB
+			synchronized (connectionsLock) {
+				closed = false;
+			}
+			txn = startTransaction();
+			try {
+				storeLastCompacted(txn);
+				commitTransaction(txn);
+			} catch (DbException e) {
+				abortTransaction(txn);
+				throw e;
+			}
+		}
 	}
 
 	/**
@@ -365,17 +388,18 @@ abstract class JdbcDatabase implements Database<Connection> {
 	 * version used by the current code and applies any suitable migrations to
 	 * the data if necessary.
 	 *
+	 * @return true if any migrations were applied, false if the schema was
+	 * already current
 	 * @throws DataTooNewException if the data uses a newer schema than the
 	 * current code
 	 * @throws DataTooOldException if the data uses an older schema than the
 	 * current code and cannot be migrated
 	 */
-	private void checkSchemaVersion(Connection txn,
+	private boolean migrateSchema(Connection txn, Settings s,
 			@Nullable MigrationListener listener) throws DbException {
-		Settings s = getSettings(txn, DB_SETTINGS_NAMESPACE);
 		int dataSchemaVersion = s.getInt(SCHEMA_VERSION_KEY, -1);
 		if (dataSchemaVersion == -1) throw new DbException();
-		if (dataSchemaVersion == CODE_SCHEMA_VERSION) return;
+		if (dataSchemaVersion == CODE_SCHEMA_VERSION) return false;
 		if (CODE_SCHEMA_VERSION < dataSchemaVersion)
 			throw new DataTooNewException();
 		// Apply any suitable migrations in order
@@ -384,7 +408,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 			if (start == dataSchemaVersion) {
 				if (LOG.isLoggable(INFO))
 					LOG.info("Migrating from schema " + start + " to " + end);
-				if (listener != null) listener.onMigrationRun();
+				if (listener != null) listener.onDatabaseMigration();
 				// Apply the migration
 				m.migrate(txn);
 				// Store the new schema version
@@ -394,11 +418,24 @@ abstract class JdbcDatabase implements Database<Connection> {
 		}
 		if (dataSchemaVersion != CODE_SCHEMA_VERSION)
 			throw new DataTooOldException();
+		return true;
 	}
 
 	// Package access for testing
 	List<Migration<Connection>> getMigrations() {
-		return Arrays.asList(new Migration38_39(), new Migration39_40());
+		return Arrays.asList(
+				new Migration38_39(),
+				new Migration39_40(),
+				new Migration40_41(dbTypes)
+		);
+	}
+
+	private boolean isCompactionDue(Settings s) {
+		long lastCompacted = s.getLong(LAST_COMPACTED_KEY, 0);
+		long elapsed = clock.currentTimeMillis() - lastCompacted;
+		if (LOG.isLoggable(INFO))
+			LOG.info(elapsed + " ms since last compaction");
+		return elapsed > MAX_COMPACTION_INTERVAL_MS;
 	}
 
 	private void storeSchemaVersion(Connection txn, int version)
@@ -408,6 +445,19 @@ abstract class JdbcDatabase implements Database<Connection> {
 		mergeSettings(txn, s, DB_SETTINGS_NAMESPACE);
 	}
 
+	private void storeLastCompacted(Connection txn) throws DbException {
+		Settings s = new Settings();
+		s.putLong(LAST_COMPACTED_KEY, clock.currentTimeMillis());
+		mergeSettings(txn, s, DB_SETTINGS_NAMESPACE);
+	}
+
+	private void initialiseSettings(Connection txn) throws DbException {
+		Settings s = new Settings();
+		s.putInt(SCHEMA_VERSION_KEY, CODE_SCHEMA_VERSION);
+		s.putLong(LAST_COMPACTED_KEY, clock.currentTimeMillis());
+		mergeSettings(txn, s, DB_SETTINGS_NAMESPACE);
+	}
+
 	private void tryToClose(@Nullable ResultSet rs) {
 		try {
 			if (rs != null) rs.close();
@@ -416,7 +466,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 		}
 	}
 
-	private void tryToClose(@Nullable Statement s) {
+	protected void tryToClose(@Nullable Statement s) {
 		try {
 			if (s != null) s.close();
 		} catch (SQLException e) {
@@ -424,24 +474,32 @@ abstract class JdbcDatabase implements Database<Connection> {
 		}
 	}
 
+	protected void tryToClose(@Nullable Connection c) {
+		try {
+			if (c != null) c.close();
+		} catch (SQLException e) {
+			logException(LOG, WARNING, e);
+		}
+	}
+
 	private void createTables(Connection txn) throws DbException {
 		Statement s = null;
 		try {
 			s = txn.createStatement();
-			s.executeUpdate(insertTypeNames(CREATE_SETTINGS));
-			s.executeUpdate(insertTypeNames(CREATE_LOCAL_AUTHORS));
-			s.executeUpdate(insertTypeNames(CREATE_CONTACTS));
-			s.executeUpdate(insertTypeNames(CREATE_GROUPS));
-			s.executeUpdate(insertTypeNames(CREATE_GROUP_METADATA));
-			s.executeUpdate(insertTypeNames(CREATE_GROUP_VISIBILITIES));
-			s.executeUpdate(insertTypeNames(CREATE_MESSAGES));
-			s.executeUpdate(insertTypeNames(CREATE_MESSAGE_METADATA));
-			s.executeUpdate(insertTypeNames(CREATE_MESSAGE_DEPENDENCIES));
-			s.executeUpdate(insertTypeNames(CREATE_OFFERS));
-			s.executeUpdate(insertTypeNames(CREATE_STATUSES));
-			s.executeUpdate(insertTypeNames(CREATE_TRANSPORTS));
-			s.executeUpdate(insertTypeNames(CREATE_OUTGOING_KEYS));
-			s.executeUpdate(insertTypeNames(CREATE_INCOMING_KEYS));
+			s.executeUpdate(dbTypes.replaceTypes(CREATE_SETTINGS));
+			s.executeUpdate(dbTypes.replaceTypes(CREATE_LOCAL_AUTHORS));
+			s.executeUpdate(dbTypes.replaceTypes(CREATE_CONTACTS));
+			s.executeUpdate(dbTypes.replaceTypes(CREATE_GROUPS));
+			s.executeUpdate(dbTypes.replaceTypes(CREATE_GROUP_METADATA));
+			s.executeUpdate(dbTypes.replaceTypes(CREATE_GROUP_VISIBILITIES));
+			s.executeUpdate(dbTypes.replaceTypes(CREATE_MESSAGES));
+			s.executeUpdate(dbTypes.replaceTypes(CREATE_MESSAGE_METADATA));
+			s.executeUpdate(dbTypes.replaceTypes(CREATE_MESSAGE_DEPENDENCIES));
+			s.executeUpdate(dbTypes.replaceTypes(CREATE_OFFERS));
+			s.executeUpdate(dbTypes.replaceTypes(CREATE_STATUSES));
+			s.executeUpdate(dbTypes.replaceTypes(CREATE_TRANSPORTS));
+			s.executeUpdate(dbTypes.replaceTypes(CREATE_OUTGOING_KEYS));
+			s.executeUpdate(dbTypes.replaceTypes(CREATE_INCOMING_KEYS));
 			s.close();
 		} catch (SQLException e) {
 			tryToClose(s);
@@ -466,15 +524,6 @@ abstract class JdbcDatabase implements Database<Connection> {
 		}
 	}
 
-	private String insertTypeNames(String s) {
-		s = s.replaceAll("_HASH", hashType);
-		s = s.replaceAll("_SECRET", secretType);
-		s = s.replaceAll("_BINARY", binaryType);
-		s = s.replaceAll("_COUNTER", counterType);
-		s = s.replaceAll("_STRING", stringType);
-		return s;
-	}
-
 	@Override
 	public Connection startTransaction() throws DbException {
 		Connection txn;
@@ -489,7 +538,6 @@ abstract class JdbcDatabase implements Database<Connection> {
 			if (txn == null) {
 				// Open a new connection
 				txn = createConnection();
-				if (txn == null) throw new DbException();
 				txn.setAutoCommit(false);
 				connectionsLock.lock();
 				try {
@@ -1201,8 +1249,8 @@ abstract class JdbcDatabase implements Database<Connection> {
 		PreparedStatement ps = null;
 		ResultSet rs = null;
 		try {
-			String sql = "SELECT authorId, formatVersion, name, publicKey,"
-					+ " localAuthorId, verified, active"
+			String sql = "SELECT authorId, formatVersion, name, alias,"
+					+ " publicKey, localAuthorId, verified, active"
 					+ " FROM contacts"
 					+ " WHERE contactId = ?";
 			ps = txn.prepareStatement(sql);
@@ -1212,15 +1260,17 @@ abstract class JdbcDatabase implements Database<Connection> {
 			AuthorId authorId = new AuthorId(rs.getBytes(1));
 			int formatVersion = rs.getInt(2);
 			String name = rs.getString(3);
-			byte[] publicKey = rs.getBytes(4);
-			AuthorId localAuthorId = new AuthorId(rs.getBytes(5));
-			boolean verified = rs.getBoolean(6);
-			boolean active = rs.getBoolean(7);
+			String alias = rs.getString(4);
+			byte[] publicKey = rs.getBytes(5);
+			AuthorId localAuthorId = new AuthorId(rs.getBytes(6));
+			boolean verified = rs.getBoolean(7);
+			boolean active = rs.getBoolean(8);
 			rs.close();
 			ps.close();
 			Author author =
 					new Author(authorId, formatVersion, name, publicKey);
-			return new Contact(c, author, localAuthorId, verified, active);
+			return new Contact(c, author, localAuthorId, alias, verified,
+					active);
 		} catch (SQLException e) {
 			tryToClose(rs);
 			tryToClose(ps);
@@ -1235,7 +1285,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 		ResultSet rs = null;
 		try {
 			String sql = "SELECT contactId, authorId, formatVersion, name,"
-					+ " publicKey, localAuthorId, verified, active"
+					+ " alias, publicKey, localAuthorId, verified, active"
 					+ " FROM contacts";
 			ps = txn.prepareStatement(sql);
 			rs = ps.executeQuery();
@@ -1245,14 +1295,15 @@ abstract class JdbcDatabase implements Database<Connection> {
 				AuthorId authorId = new AuthorId(rs.getBytes(2));
 				int formatVersion = rs.getInt(3);
 				String name = rs.getString(4);
-				byte[] publicKey = rs.getBytes(5);
+				String alias = rs.getString(5);
+				byte[] publicKey = rs.getBytes(6);
 				Author author =
 						new Author(authorId, formatVersion, name, publicKey);
-				AuthorId localAuthorId = new AuthorId(rs.getBytes(6));
-				boolean verified = rs.getBoolean(7);
-				boolean active = rs.getBoolean(8);
+				AuthorId localAuthorId = new AuthorId(rs.getBytes(7));
+				boolean verified = rs.getBoolean(8);
+				boolean active = rs.getBoolean(9);
 				contacts.add(new Contact(contactId, author, localAuthorId,
-						verified, active));
+						alias, verified, active));
 			}
 			rs.close();
 			ps.close();
@@ -1293,8 +1344,8 @@ abstract class JdbcDatabase implements Database<Connection> {
 		PreparedStatement ps = null;
 		ResultSet rs = null;
 		try {
-			String sql = "SELECT contactId, formatVersion, name, publicKey,"
-					+ " localAuthorId, verified, active"
+			String sql = "SELECT contactId, formatVersion, name, alias,"
+					+ " publicKey, localAuthorId, verified, active"
 					+ " FROM contacts"
 					+ " WHERE authorId = ?";
 			ps = txn.prepareStatement(sql);
@@ -1305,14 +1356,15 @@ abstract class JdbcDatabase implements Database<Connection> {
 				ContactId c = new ContactId(rs.getInt(1));
 				int formatVersion = rs.getInt(2);
 				String name = rs.getString(3);
-				byte[] publicKey = rs.getBytes(4);
-				AuthorId localAuthorId = new AuthorId(rs.getBytes(5));
-				boolean verified = rs.getBoolean(6);
-				boolean active = rs.getBoolean(7);
+				String alias = rs.getString(4);
+				byte[] publicKey = rs.getBytes(5);
+				AuthorId localAuthorId = new AuthorId(rs.getBytes(6));
+				boolean verified = rs.getBoolean(7);
+				boolean active = rs.getBoolean(8);
 				Author author =
 						new Author(remote, formatVersion, name, publicKey);
-				contacts.add(new Contact(c, author, localAuthorId, verified,
-						active));
+				contacts.add(new Contact(c, author, localAuthorId, alias,
+						verified, active));
 			}
 			rs.close();
 			ps.close();
@@ -1508,7 +1560,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 			rs.close();
 			ps.close();
 			if (raw == null) throw new MessageDeletedException();
-			if (raw.length < MESSAGE_HEADER_LENGTH) throw new AssertionError();
+			if (raw.length <= MESSAGE_HEADER_LENGTH) throw new AssertionError();
 			byte[] body = new byte[raw.length - MESSAGE_HEADER_LENGTH];
 			System.arraycopy(raw, MESSAGE_HEADER_LENGTH, body, 0, body.length);
 			return new Message(m, g, timestamp, body);
@@ -2737,6 +2789,25 @@ abstract class JdbcDatabase implements Database<Connection> {
 		}
 	}
 
+	@Override
+	public void setContactAlias(Connection txn, ContactId c,
+			@Nullable String alias) throws DbException {
+		PreparedStatement ps = null;
+		try {
+			String sql = "UPDATE contacts SET alias = ? WHERE contactId = ?";
+			ps = txn.prepareStatement(sql);
+			if (alias == null) ps.setNull(1, VARCHAR);
+			else ps.setString(1, alias);
+			ps.setInt(2, c.getInt());
+			int affected = ps.executeUpdate();
+			if (affected < 0 || affected > 1) throw new DbStateException();
+			ps.close();
+		} catch (SQLException e) {
+			tryToClose(ps);
+			throw new DbException(e);
+		}
+	}
+
 	@Override
 	public void setGroupVisibility(Connection txn, ContactId c, GroupId g,
 			boolean shared) throws DbException {

bramble-core/src/main/java/org/briarproject/bramble/db/Migration40_41.java

@@ -0,0 +1,56 @@
+package org.briarproject.bramble.db;
+
+import org.briarproject.bramble.api.db.DbException;
+
+import java.sql.Connection;
+import java.sql.SQLException;
+import java.sql.Statement;
+import java.util.logging.Logger;
+
+import javax.annotation.Nullable;
+
+import static java.util.logging.Level.WARNING;
+import static java.util.logging.Logger.getLogger;
+import static org.briarproject.bramble.util.LogUtils.logException;
+
+class Migration40_41 implements Migration<Connection> {
+
+	private static final Logger LOG = getLogger(Migration40_41.class.getName());
+
+	private final DatabaseTypes dbTypes;
+
+	public Migration40_41(DatabaseTypes databaseTypes) {
+		this.dbTypes = databaseTypes;
+	}
+
+	@Override
+	public int getStartVersion() {
+		return 40;
+	}
+
+	@Override
+	public int getEndVersion() {
+		return 41;
+	}
+
+	@Override
+	public void migrate(Connection txn) throws DbException {
+		Statement s = null;
+		try {
+			s = txn.createStatement();
+			s.execute("ALTER TABLE contacts"
+					+ dbTypes.replaceTypes(" ADD alias _STRING"));
+		} catch (SQLException e) {
+			tryToClose(s);
+			throw new DbException(e);
+		}
+	}
+
+	private void tryToClose(@Nullable Statement s) {
+		try {
+			if (s != null) s.close();
+		} catch (SQLException e) {
+			logException(LOG, WARNING, e);
+		}
+	}
+}

bramble-core/src/main/java/org/briarproject/bramble/identity/IdentityManagerImpl.java

@@ -1,29 +1,21 @@
 package org.briarproject.bramble.identity;
 
-import org.briarproject.bramble.api.contact.Contact;
 import org.briarproject.bramble.api.crypto.CryptoComponent;
 import org.briarproject.bramble.api.crypto.KeyPair;
 import org.briarproject.bramble.api.db.DatabaseComponent;
 import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.db.Transaction;
-import org.briarproject.bramble.api.identity.Author.Status;
 import org.briarproject.bramble.api.identity.AuthorFactory;
-import org.briarproject.bramble.api.identity.AuthorId;
 import org.briarproject.bramble.api.identity.IdentityManager;
 import org.briarproject.bramble.api.identity.LocalAuthor;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 
-import java.util.Collection;
 import java.util.logging.Logger;
 
 import javax.annotation.Nullable;
 import javax.annotation.concurrent.ThreadSafe;
 import javax.inject.Inject;
 
-import static org.briarproject.bramble.api.identity.Author.Status.OURSELVES;
-import static org.briarproject.bramble.api.identity.Author.Status.UNKNOWN;
-import static org.briarproject.bramble.api.identity.Author.Status.UNVERIFIED;
-import static org.briarproject.bramble.api.identity.Author.Status.VERIFIED;
 import static org.briarproject.bramble.util.LogUtils.logDuration;
 import static org.briarproject.bramble.util.LogUtils.now;
 
@@ -75,27 +67,16 @@ class IdentityManagerImpl implements IdentityManager {
 			LOG.info("No local author to store");
 			return;
 		}
-		Transaction txn = db.startTransaction(false);
-		try {
-			db.addLocalAuthor(txn, cached);
-			db.commitTransaction(txn);
-			LOG.info("Local author stored");
-		} finally {
-			db.endTransaction(txn);
-		}
+		db.transaction(false, txn -> db.addLocalAuthor(txn, cached));
+		LOG.info("Local author stored");
 	}
 
 	@Override
 	public LocalAuthor getLocalAuthor() throws DbException {
 		if (cachedAuthor == null) {
-			Transaction txn = db.startTransaction(true);
-			try {
-				cachedAuthor = loadLocalAuthor(txn);
-				LOG.info("Local author loaded");
-				db.commitTransaction(txn);
-			} finally {
-				db.endTransaction(txn);
-			}
+			cachedAuthor =
+					db.transactionWithResult(true, this::loadLocalAuthor);
+			LOG.info("Local author loaded");
 		}
 		LocalAuthor cached = cachedAuthor;
 		if (cached == null) throw new AssertionError();
@@ -118,26 +99,4 @@ class IdentityManagerImpl implements IdentityManager {
 		return db.getLocalAuthors(txn).iterator().next();
 	}
 
-	@Override
-	public Status getAuthorStatus(AuthorId authorId) throws DbException {
-		Transaction txn = db.startTransaction(true);
-		try {
-			return getAuthorStatus(txn, authorId);
-		} finally {
-			db.endTransaction(txn);
-		}
-	}
-
-	@Override
-	public Status getAuthorStatus(Transaction txn, AuthorId authorId)
-			throws DbException {
-		if (getLocalAuthor(txn).getId().equals(authorId)) return OURSELVES;
-		Collection<Contact> contacts = db.getContactsByAuthorId(txn, authorId);
-		if (contacts.isEmpty()) return UNKNOWN;
-		for (Contact c : contacts) {
-			if (c.isVerified()) return VERIFIED;
-		}
-		return UNVERIFIED;
-	}
-
 }

bramble-core/src/main/java/org/briarproject/bramble/lifecycle/LifecycleManagerImpl.java

@@ -6,7 +6,6 @@ import org.briarproject.bramble.api.db.DataTooOldException;
 import org.briarproject.bramble.api.db.DatabaseComponent;
 import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.db.MigrationListener;
-import org.briarproject.bramble.api.db.Transaction;
 import org.briarproject.bramble.api.event.EventBus;
 import org.briarproject.bramble.api.identity.IdentityManager;
 import org.briarproject.bramble.api.lifecycle.LifecycleManager;
@@ -29,6 +28,7 @@ import javax.inject.Inject;
 import static java.util.logging.Level.FINE;
 import static java.util.logging.Level.INFO;
 import static java.util.logging.Level.WARNING;
+import static org.briarproject.bramble.api.lifecycle.LifecycleManager.LifecycleState.COMPACTING_DATABASE;
 import static org.briarproject.bramble.api.lifecycle.LifecycleManager.LifecycleState.MIGRATING_DATABASE;
 import static org.briarproject.bramble.api.lifecycle.LifecycleManager.LifecycleState.RUNNING;
 import static org.briarproject.bramble.api.lifecycle.LifecycleManager.LifecycleState.STARTING;
@@ -114,20 +114,16 @@ class LifecycleManagerImpl implements LifecycleManager, MigrationListener {
 			dbLatch.countDown();
 			eventBus.broadcast(new LifecycleEvent(STARTING_SERVICES));
 
-			Transaction txn = db.startTransaction(false);
-			try {
+			db.transaction(false, txn -> {
 				for (Client c : clients) {
-					start = now();
+					long start1 = now();
 					c.createLocalState(txn);
 					if (LOG.isLoggable(FINE)) {
 						logDuration(LOG, "Starting client "
-								+ c.getClass().getSimpleName(), start);
+								+ c.getClass().getSimpleName(), start1);
 					}
 				}
-				db.commitTransaction(txn);
-			} finally {
-				db.endTransaction(txn);
-			}
+			});
 			for (Service s : services) {
 				start = now();
 				s.startService();
@@ -159,11 +155,17 @@ class LifecycleManagerImpl implements LifecycleManager, MigrationListener {
 	}
 
 	@Override
-	public void onMigrationRun() {
+	public void onDatabaseMigration() {
 		state = MIGRATING_DATABASE;
 		eventBus.broadcast(new LifecycleEvent(MIGRATING_DATABASE));
 	}
 
+	@Override
+	public void onDatabaseCompaction() {
+		state = COMPACTING_DATABASE;
+		eventBus.broadcast(new LifecycleEvent(COMPACTING_DATABASE));
+	}
+
 	@Override
 	public void stopServices() {
 		try {

bramble-core/src/main/java/org/briarproject/bramble/plugin/bluetooth/BluetoothPlugin.java

@@ -23,7 +23,6 @@ import org.briarproject.bramble.api.plugin.event.EnableBluetoothEvent;
 import org.briarproject.bramble.api.properties.TransportProperties;
 import org.briarproject.bramble.api.settings.Settings;
 import org.briarproject.bramble.api.settings.event.SettingsUpdatedEvent;
-import org.briarproject.bramble.util.StringUtils;
 
 import java.io.IOException;
 import java.security.SecureRandom;
@@ -46,6 +45,9 @@ import static org.briarproject.bramble.api.plugin.BluetoothConstants.PROP_UUID;
 import static org.briarproject.bramble.api.plugin.BluetoothConstants.UUID_BYTES;
 import static org.briarproject.bramble.util.LogUtils.logException;
 import static org.briarproject.bramble.util.PrivacyUtils.scrubMacAddress;
+import static org.briarproject.bramble.util.StringUtils.isNullOrEmpty;
+import static org.briarproject.bramble.util.StringUtils.macToBytes;
+import static org.briarproject.bramble.util.StringUtils.macToString;
 
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
@@ -96,6 +98,9 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 	abstract DuplexTransportConnection connectTo(String address, String uuid)
 			throws IOException;
 
+	@Nullable
+	abstract DuplexTransportConnection discoverAndConnect(String uuid);
+
 	BluetoothPlugin(BluetoothConnectionLimiter connectionLimiter,
 			Executor ioExecutor, SecureRandom secureRandom,
 			Backoff backoff, DuplexPluginCallback callback, int maxLatency) {
@@ -193,7 +198,7 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 			address = getBluetoothAddress();
 			if (LOG.isLoggable(INFO))
 				LOG.info("Local address " + scrubMacAddress(address));
-			if (!StringUtils.isNullOrEmpty(address)) {
+			if (!isNullOrEmpty(address)) {
 				p.put(PROP_ADDRESS, address);
 				changed = true;
 			}
@@ -256,9 +261,9 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 		// Try to connect to known devices in parallel
 		for (Entry<ContactId, TransportProperties> e : contacts.entrySet()) {
 			String address = e.getValue().get(PROP_ADDRESS);
-			if (StringUtils.isNullOrEmpty(address)) continue;
+			if (isNullOrEmpty(address)) continue;
 			String uuid = e.getValue().get(PROP_UUID);
-			if (StringUtils.isNullOrEmpty(uuid)) continue;
+			if (isNullOrEmpty(uuid)) continue;
 			ContactId c = e.getKey();
 			ioExecutor.execute(() -> {
 				if (!isRunning() || !shouldAllowContactConnections()) return;
@@ -309,9 +314,9 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 		if (!isRunning() || !shouldAllowContactConnections()) return null;
 		if (!connectionLimiter.canOpenContactConnection()) return null;
 		String address = p.get(PROP_ADDRESS);
-		if (StringUtils.isNullOrEmpty(address)) return null;
+		if (isNullOrEmpty(address)) return null;
 		String uuid = p.get(PROP_UUID);
-		if (StringUtils.isNullOrEmpty(uuid)) return null;
+		if (isNullOrEmpty(uuid)) return null;
 		DuplexTransportConnection conn = connect(address, uuid);
 		if (conn == null) return null;
 		// TODO: Why don't we reset the backoff here?
@@ -326,9 +331,6 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 	@Override
 	public KeyAgreementListener createKeyAgreementListener(byte[] commitment) {
 		if (!isRunning()) return null;
-		// There's no point listening if we can't discover our own address
-		String address = getBluetoothAddress();
-		if (address == null) return null;
 		// No truncation necessary because COMMIT_LENGTH = 16
 		String uuid = UUID.nameUUIDFromBytes(commitment).toString();
 		if (LOG.isLoggable(INFO)) LOG.info("Key agreement UUID " + uuid);
@@ -346,7 +348,8 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 		}
 		BdfList descriptor = new BdfList();
 		descriptor.add(TRANSPORT_ID_BLUETOOTH);
-		descriptor.add(StringUtils.macToBytes(address));
+		String address = getBluetoothAddress();
+		if (address != null) descriptor.add(macToBytes(address));
 		return new BluetoothKeyAgreementListener(descriptor, ss);
 	}
 
@@ -354,18 +357,25 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 	public DuplexTransportConnection createKeyAgreementConnection(
 			byte[] commitment, BdfList descriptor) {
 		if (!isRunning()) return null;
-		String address;
-		try {
-			address = parseAddress(descriptor);
-		} catch (FormatException e) {
-			LOG.info("Invalid address in key agreement descriptor");
-			return null;
-		}
 		// No truncation necessary because COMMIT_LENGTH = 16
 		String uuid = UUID.nameUUIDFromBytes(commitment).toString();
-		if (LOG.isLoggable(INFO))
-			LOG.info("Connecting to key agreement UUID " + uuid);
-		DuplexTransportConnection conn = connect(address, uuid);
+		DuplexTransportConnection conn;
+		if (descriptor.size() == 1) {
+			if (LOG.isLoggable(INFO))
+				LOG.info("Discovering address for key agreement UUID " + uuid);
+			conn = discoverAndConnect(uuid);
+		} else {
+			String address;
+			try {
+				address = parseAddress(descriptor);
+			} catch (FormatException e) {
+				LOG.info("Invalid address in key agreement descriptor");
+				return null;
+			}
+			if (LOG.isLoggable(INFO))
+				LOG.info("Connecting to key agreement UUID " + uuid);
+			conn = connect(address, uuid);
+		}
 		if (conn != null) connectionLimiter.keyAgreementConnectionOpened(conn);
 		return conn;
 	}
@@ -373,7 +383,7 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 	private String parseAddress(BdfList descriptor) throws FormatException {
 		byte[] mac = descriptor.getRaw(1);
 		if (mac.length != 6) throw new FormatException();
-		return StringUtils.macToString(mac);
+		return macToString(mac);
 	}
 
 	@Override

bramble-core/src/main/java/org/briarproject/bramble/plugin/tor/TorPlugin.java

@@ -4,6 +4,8 @@ import net.freehaven.tor.control.EventHandler;
 import net.freehaven.tor.control.TorControlConnection;
 
 import org.briarproject.bramble.PoliteExecutor;
+import org.briarproject.bramble.api.battery.BatteryManager;
+import org.briarproject.bramble.api.battery.event.BatteryEvent;
 import org.briarproject.bramble.api.contact.ContactId;
 import org.briarproject.bramble.api.data.BdfList;
 import org.briarproject.bramble.api.event.Event;
@@ -28,7 +30,6 @@ import org.briarproject.bramble.api.system.Clock;
 import org.briarproject.bramble.api.system.LocationUtils;
 import org.briarproject.bramble.api.system.ResourceProvider;
 import org.briarproject.bramble.util.IoUtils;
-import org.briarproject.bramble.util.StringUtils;
 
 import java.io.Closeable;
 import java.io.EOFException;
@@ -70,9 +71,11 @@ import static org.briarproject.bramble.api.plugin.TorConstants.PREF_TOR_NETWORK_
 import static org.briarproject.bramble.api.plugin.TorConstants.PREF_TOR_NETWORK_NEVER;
 import static org.briarproject.bramble.api.plugin.TorConstants.PREF_TOR_NETWORK_WITH_BRIDGES;
 import static org.briarproject.bramble.api.plugin.TorConstants.PREF_TOR_PORT;
-import static org.briarproject.bramble.api.plugin.TorConstants.PROP_ONION;
+import static org.briarproject.bramble.api.plugin.TorConstants.PROP_ONION_V2;
+import static org.briarproject.bramble.api.plugin.TorConstants.PROP_ONION_V3;
 import static org.briarproject.bramble.util.LogUtils.logException;
 import static org.briarproject.bramble.util.PrivacyUtils.scrubOnion;
+import static org.briarproject.bramble.util.StringUtils.isNullOrEmpty;
 
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
@@ -87,20 +90,22 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 	private static final String OWNER = "__OwningControllerProcess";
 	private static final int COOKIE_TIMEOUT_MS = 3000;
 	private static final int COOKIE_POLLING_INTERVAL_MS = 200;
-	private static final Pattern ONION = Pattern.compile("[a-z2-7]{16}");
+	private static final Pattern ONION_V2 = Pattern.compile("[a-z2-7]{16}");
+	private static final Pattern ONION_V3 = Pattern.compile("[a-z2-7]{56}");
 
 	private final Executor ioExecutor, connectionStatusExecutor;
 	private final NetworkManager networkManager;
 	private final LocationUtils locationUtils;
 	private final SocketFactory torSocketFactory;
 	private final Clock clock;
+	private final BatteryManager batteryManager;
 	private final Backoff backoff;
 	private final DuplexPluginCallback callback;
 	private final String architecture;
 	private final CircumventionProvider circumventionProvider;
 	private final ResourceProvider resourceProvider;
 	private final int maxLatency, maxIdleTime, socketTimeout;
-	private final File torDirectory, torFile, geoIpFile, configFile;
+	private final File torDirectory, torFile, geoIpFile, obfs4File, configFile;
 	private final File doneFile, cookieFile;
 	private final ConnectionStatus connectionStatus;
 	private final AtomicBoolean used = new AtomicBoolean(false);
@@ -119,7 +124,8 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 	TorPlugin(Executor ioExecutor, NetworkManager networkManager,
 			LocationUtils locationUtils, SocketFactory torSocketFactory,
 			Clock clock, ResourceProvider resourceProvider,
-			CircumventionProvider circumventionProvider, Backoff backoff,
+			CircumventionProvider circumventionProvider,
+			BatteryManager batteryManager, Backoff backoff,
 			DuplexPluginCallback callback, String architecture, int maxLatency,
 			int maxIdleTime, File torDirectory) {
 		this.ioExecutor = ioExecutor;
@@ -129,6 +135,7 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 		this.clock = clock;
 		this.resourceProvider = resourceProvider;
 		this.circumventionProvider = circumventionProvider;
+		this.batteryManager = batteryManager;
 		this.backoff = backoff;
 		this.callback = callback;
 		this.architecture = architecture;
@@ -140,6 +147,7 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 		this.torDirectory = torDirectory;
 		torFile = new File(torDirectory, "tor");
 		geoIpFile = new File(torDirectory, "geoip");
+		obfs4File = new File(torDirectory, "obfs4proxy");
 		configFile = new File(torDirectory, "torrc");
 		doneFile = new File(torDirectory, "done");
 		cookieFile = new File(torDirectory, ".tor/control_auth_cookie");
@@ -258,7 +266,8 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 			throw new PluginException(e);
 		}
 		// Check whether we're online
-		updateConnectionStatus(networkManager.getNetworkStatus());
+		updateConnectionStatus(networkManager.getNetworkStatus(),
+				batteryManager.isCharging());
 		// Bind a server socket to receive incoming hidden service connections
 		bind();
 	}
@@ -282,6 +291,12 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 			in = getGeoIpInputStream();
 			out = new FileOutputStream(geoIpFile);
 			IoUtils.copyAndClose(in, out);
+			// Unzip the Obfs4 proxy to the filesystem
+			in = getObfs4InputStream();
+			out = new FileOutputStream(obfs4File);
+			IoUtils.copyAndClose(in, out);
+			// Make the Obfs4 proxy executable
+			if (!obfs4File.setExecutable(true, true)) throw new IOException();
 			// Copy the config file to the filesystem
 			in = getConfigInputStream();
 			out = new FileOutputStream(configFile);
@@ -312,6 +327,16 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 		return zin;
 	}
 
+	private InputStream getObfs4InputStream() throws IOException {
+		if (LOG.isLoggable(INFO))
+			LOG.info("Installing obfs4proxy binary for " + architecture);
+		InputStream in = resourceProvider
+				.getResourceInputStream("obfs4proxy_" + architecture, ".zip");
+		ZipInputStream zin = new ZipInputStream(in);
+		if (zin.getNextEntry() == null) throw new IOException();
+		return zin;
+	}
+
 	private InputStream getConfigInputStream() {
 		return getClass().getClassLoader().getResourceAsStream("torrc");
 	}
@@ -362,7 +387,7 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 			// If there's already a port number stored in config, reuse it
 			String portString = settings.get(PREF_TOR_PORT);
 			int port;
-			if (StringUtils.isNullOrEmpty(portString)) port = 0;
+			if (isNullOrEmpty(portString)) port = 0;
 			else port = Integer.parseInt(portString);
 			// Bind a server socket to receive connections from Tor
 			ServerSocket ss = null;
@@ -427,11 +452,11 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 			return;
 		}
 		// Publish the hidden service's onion hostname in transport properties
-		String hostname = response.get(HS_ADDRESS);
+		String onion2 = response.get(HS_ADDRESS);
 		if (LOG.isLoggable(INFO))
-			LOG.info("Hidden service " + scrubOnion(hostname));
+			LOG.info("Hidden service " + scrubOnion(onion2));
 		TransportProperties p = new TransportProperties();
-		p.put(PROP_ONION, hostname);
+		p.put(PROP_ONION_V2, onion2);
 		callback.mergeLocalProperties(p);
 		if (privKey == null) {
 			// Save the hidden service's private key for next time
@@ -470,6 +495,8 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 		if (enable) {
 			Collection<String> conf = new ArrayList<>();
 			conf.add("UseBridges 1");
+			conf.add("ClientTransportPlugin obfs4 exec " +
+					obfs4File.getAbsolutePath());
 			conf.addAll(circumventionProvider.getBridges());
 			controlConnection.setConf(conf);
 		} else {
@@ -530,26 +557,41 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 	@Override
 	public DuplexTransportConnection createConnection(TransportProperties p) {
 		if (!isRunning()) return null;
-		String onion = p.get(PROP_ONION);
-		if (StringUtils.isNullOrEmpty(onion)) return null;
-		if (!ONION.matcher(onion).matches()) {
-			// not scrubbing this address, so we are able to find the problem
-			if (LOG.isLoggable(INFO)) LOG.info("Invalid hostname: " + onion);
-			return null;
+		String bestOnion = null;
+		String onion2 = p.get(PROP_ONION_V2);
+		String onion3 = p.get(PROP_ONION_V3);
+		if (!isNullOrEmpty(onion2)) {
+			if (ONION_V2.matcher(onion2).matches()) {
+				bestOnion = onion2;
+			} else {
+				// Don't scrub the address so we can find the problem
+				if (LOG.isLoggable(INFO))
+					LOG.info("Invalid v2 hostname: " + onion2);
+			}
 		}
+		if (!isNullOrEmpty(onion3)) {
+			if (ONION_V3.matcher(onion3).matches()) {
+				bestOnion = onion3;
+			} else {
+				// Don't scrub the address so we can find the problem
+				if (LOG.isLoggable(INFO))
+					LOG.info("Invalid v3 hostname: " + onion3);
+			}
+		}
+		if (bestOnion == null) return null;
 		Socket s = null;
 		try {
 			if (LOG.isLoggable(INFO))
-				LOG.info("Connecting to " + scrubOnion(onion));
-			s = torSocketFactory.createSocket(onion + ".onion", 80);
+				LOG.info("Connecting to " + scrubOnion(bestOnion));
+			s = torSocketFactory.createSocket(bestOnion + ".onion", 80);
 			s.setSoTimeout(socketTimeout);
 			if (LOG.isLoggable(INFO))
-				LOG.info("Connected to " + scrubOnion(onion));
+				LOG.info("Connected to " + scrubOnion(bestOnion));
 			return new TorTransportConnection(this, s);
 		} catch (IOException e) {
 			if (LOG.isLoggable(INFO)) {
-				LOG.info("Could not connect to " + scrubOnion(onion) + ": " +
-						e.toString());
+				LOG.info("Could not connect to " + scrubOnion(bestOnion)
+						+ ": " + e.toString());
 			}
 			tryToClose(s);
 			return null;
@@ -592,7 +634,8 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 			LOG.info("OR connection " + status + " " + orName);
 		if (status.equals("CLOSED") || status.equals("FAILED")) {
 			// Check whether we've lost connectivity
-			updateConnectionStatus(networkManager.getNetworkStatus());
+			updateConnectionStatus(networkManager.getNetworkStatus(),
+					batteryManager.isCharging());
 		}
 	}
 
@@ -627,14 +670,33 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 			if (s.getNamespace().equals(ID.getString())) {
 				LOG.info("Tor settings updated");
 				settings = s.getSettings();
-				updateConnectionStatus(networkManager.getNetworkStatus());
+				// Works around a bug introduced in Tor 0.3.4.8. Could be
+				// replaced with callback.transportDisabled() when fixed.
+				disableNetwork();
+				updateConnectionStatus(networkManager.getNetworkStatus(),
+						batteryManager.isCharging());
 			}
 		} else if (e instanceof NetworkStatusEvent) {
-			updateConnectionStatus(((NetworkStatusEvent) e).getStatus());
+			updateConnectionStatus(((NetworkStatusEvent) e).getStatus(),
+					batteryManager.isCharging());
+		} else if (e instanceof BatteryEvent) {
+			updateConnectionStatus(networkManager.getNetworkStatus(),
+					((BatteryEvent) e).isCharging());
 		}
 	}
 
-	private void updateConnectionStatus(NetworkStatus status) {
+	private void disableNetwork() {
+		connectionStatusExecutor.execute(() -> {
+			try {
+				enableNetwork(false);
+			} catch (IOException ex) {
+				logException(LOG, WARNING, ex);
+			}
+		});
+	}
+
+	private void updateConnectionStatus(NetworkStatus status,
+			boolean charging) {
 		connectionStatusExecutor.execute(() -> {
 			if (!running) return;
 			boolean online = status.isConnected();
@@ -652,6 +714,7 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 				LOG.info("Online: " + online + ", wifi: " + wifi);
 				if ("".equals(country)) LOG.info("Country code unknown");
 				else LOG.info("Country code: " + country);
+				LOG.info("Charging: " + charging);
 			}
 
 			try {
@@ -675,12 +738,24 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 					enableBridges(false);
 					enableNetwork(true);
 				}
+				if (online && wifi && charging) {
+					LOG.info("Enabling connection padding");
+					enableConnectionPadding(true);
+				} else {
+					LOG.info("Disabling connection padding");
+					enableConnectionPadding(false);
+				}
 			} catch (IOException e) {
 				logException(LOG, WARNING, e);
 			}
 		});
 	}
 
+	private void enableConnectionPadding(boolean enable) throws IOException {
+		if (!running) return;
+		controlConnection.setConf("ConnectionPadding", enable ? "1" : "0");
+	}
+
 	// TODO remove when sufficient time has passed. Added 2018-08-15
 	private void migrateSettings() {
 		Settings sOld = callback.getSettings();

bramble-core/src/main/java/org/briarproject/bramble/properties/TransportPropertyManagerImpl.java

@@ -142,15 +142,7 @@ class TransportPropertyManagerImpl implements TransportPropertyManager,
 	@Override
 	public Map<TransportId, TransportProperties> getLocalProperties()
 			throws DbException {
-		Map<TransportId, TransportProperties> local;
-		Transaction txn = db.startTransaction(true);
-		try {
-			local = getLocalProperties(txn);
-			db.commitTransaction(txn);
-		} finally {
-			db.endTransaction(txn);
-		}
-		return local;
+		return db.transactionWithResult(true, this::getLocalProperties);
 	}
 
 	@Override
@@ -176,9 +168,8 @@ class TransportPropertyManagerImpl implements TransportPropertyManager,
 	public TransportProperties getLocalProperties(TransportId t)
 			throws DbException {
 		try {
-			TransportProperties p = null;
-			Transaction txn = db.startTransaction(true);
-			try {
+			return db.transactionWithResult(true, txn -> {
+				TransportProperties p = null;
 				// Find the latest local update
 				LatestUpdate latest = findLatest(txn, localGroup.getId(), t,
 						true);
@@ -188,11 +179,8 @@ class TransportPropertyManagerImpl implements TransportPropertyManager,
 							latest.messageId);
 					p = parseProperties(message);
 				}
-				db.commitTransaction(txn);
-			} finally {
-				db.endTransaction(txn);
-			}
-			return p == null ? new TransportProperties() : p;
+				return p == null ? new TransportProperties() : p;
+			});
 		} catch (FormatException e) {
 			throw new DbException(e);
 		}
@@ -201,16 +189,12 @@ class TransportPropertyManagerImpl implements TransportPropertyManager,
 	@Override
 	public Map<ContactId, TransportProperties> getRemoteProperties(
 			TransportId t) throws DbException {
-		Map<ContactId, TransportProperties> remote = new HashMap<>();
-		Transaction txn = db.startTransaction(true);
-		try {
+		return db.transactionWithResult(true, txn -> {
+			Map<ContactId, TransportProperties> remote = new HashMap<>();
 			for (Contact c : db.getContacts(txn))
 				remote.put(c.getId(), getRemoteProperties(txn, c, t));
-			db.commitTransaction(txn);
-		} finally {
-			db.endTransaction(txn);
-		}
-		return remote;
+			return remote;
+		});
 	}
 
 	private TransportProperties getRemoteProperties(Transaction txn, Contact c,
@@ -234,23 +218,15 @@ class TransportPropertyManagerImpl implements TransportPropertyManager,
 	@Override
 	public TransportProperties getRemoteProperties(ContactId c, TransportId t)
 			throws DbException {
-		TransportProperties p;
-		Transaction txn = db.startTransaction(true);
-		try {
-			p = getRemoteProperties(txn, db.getContact(txn, c), t);
-			db.commitTransaction(txn);
-		} finally {
-			db.endTransaction(txn);
-		}
-		return p;
+		return db.transactionWithResult(true, txn ->
+				getRemoteProperties(txn, db.getContact(txn, c), t));
 	}
 
 	@Override
 	public void mergeLocalProperties(TransportId t, TransportProperties p)
 			throws DbException {
 		try {
-			Transaction txn = db.startTransaction(false);
-			try {
+			db.transaction(false, txn -> {
 				// Merge the new properties with any existing properties
 				TransportProperties merged;
 				boolean changed;
@@ -287,10 +263,7 @@ class TransportPropertyManagerImpl implements TransportPropertyManager,
 							db.removeMessage(txn, latest.messageId);
 					}
 				}
-				db.commitTransaction(txn);
-			} finally {
-				db.endTransaction(txn);
-			}
+			});
 		} catch (FormatException e) {
 			throw new DbException(e);
 		}

bramble-core/src/main/java/org/briarproject/bramble/settings/SettingsManagerImpl.java

@@ -23,15 +23,8 @@ class SettingsManagerImpl implements SettingsManager {
 
 	@Override
 	public Settings getSettings(String namespace) throws DbException {
-		Settings s;
-		Transaction txn = db.startTransaction(true);
-		try {
-			s = db.getSettings(txn, namespace);
-			db.commitTransaction(txn);
-		} finally {
-			db.endTransaction(txn);
-		}
-		return s;
+		return db.transactionWithResult(true, txn ->
+				db.getSettings(txn, namespace));
 	}
 
 	@Override
@@ -42,12 +35,6 @@ class SettingsManagerImpl implements SettingsManager {
 
 	@Override
 	public void mergeSettings(Settings s, String namespace) throws DbException {
-		Transaction txn = db.startTransaction(false);
-		try {
-			db.mergeSettings(txn, s, namespace);
-			db.commitTransaction(txn);
-		} finally {
-			db.endTransaction(txn);
-		}
+		db.transaction(false, txn -> db.mergeSettings(txn, s, namespace));
 	}
 }

bramble-core/src/main/java/org/briarproject/bramble/sync/DuplexOutgoingSession.java

@@ -5,7 +5,6 @@ import org.briarproject.bramble.api.contact.event.ContactRemovedEvent;
 import org.briarproject.bramble.api.db.DatabaseComponent;
 import org.briarproject.bramble.api.db.DatabaseExecutor;
 import org.briarproject.bramble.api.db.DbException;
-import org.briarproject.bramble.api.db.Transaction;
 import org.briarproject.bramble.api.event.Event;
 import org.briarproject.bramble.api.event.EventBus;
 import org.briarproject.bramble.api.event.EventListener;
@@ -230,14 +229,8 @@ class DuplexOutgoingSession implements SyncSession, EventListener {
 			if (interrupted) return;
 			if (!generateAckQueued.getAndSet(false)) throw new AssertionError();
 			try {
-				Ack a;
-				Transaction txn = db.startTransaction(false);
-				try {
-					a = db.generateAck(txn, contactId, MAX_MESSAGE_IDS);
-					db.commitTransaction(txn);
-				} finally {
-					db.endTransaction(txn);
-				}
+				Ack a = db.transactionWithNullableResult(false, txn ->
+						db.generateAck(txn, contactId, MAX_MESSAGE_IDS));
 				if (LOG.isLoggable(INFO))
 					LOG.info("Generated ack: " + (a != null));
 				if (a != null) writerTasks.add(new WriteAck(a));
@@ -275,16 +268,15 @@ class DuplexOutgoingSession implements SyncSession, EventListener {
 			if (!generateBatchQueued.getAndSet(false))
 				throw new AssertionError();
 			try {
-				Collection<Message> b;
-				Transaction txn = db.startTransaction(false);
-				try {
-					b = db.generateRequestedBatch(txn, contactId,
-							MAX_RECORD_PAYLOAD_BYTES, maxLatency);
-					setNextSendTime(db.getNextSendTime(txn, contactId));
-					db.commitTransaction(txn);
-				} finally {
-					db.endTransaction(txn);
-				}
+				Collection<Message> b =
+						db.transactionWithNullableResult(false, txn -> {
+							Collection<Message> batch =
+									db.generateRequestedBatch(txn, contactId,
+											MAX_RECORD_PAYLOAD_BYTES,
+											maxLatency);
+							setNextSendTime(db.getNextSendTime(txn, contactId));
+							return batch;
+						});
 				if (LOG.isLoggable(INFO))
 					LOG.info("Generated batch: " + (b != null));
 				if (b != null) writerTasks.add(new WriteBatch(b));
@@ -322,16 +314,12 @@ class DuplexOutgoingSession implements SyncSession, EventListener {
 			if (!generateOfferQueued.getAndSet(false))
 				throw new AssertionError();
 			try {
-				Offer o;
-				Transaction txn = db.startTransaction(false);
-				try {
-					o = db.generateOffer(txn, contactId, MAX_MESSAGE_IDS,
-							maxLatency);
+				Offer o = db.transactionWithNullableResult(false, txn -> {
+					Offer offer = db.generateOffer(txn, contactId,
+							MAX_MESSAGE_IDS, maxLatency);
 					setNextSendTime(db.getNextSendTime(txn, contactId));
-					db.commitTransaction(txn);
-				} finally {
-					db.endTransaction(txn);
-				}
+					return offer;
+				});
 				if (LOG.isLoggable(INFO))
 					LOG.info("Generated offer: " + (o != null));
 				if (o != null) writerTasks.add(new WriteOffer(o));
@@ -369,14 +357,8 @@ class DuplexOutgoingSession implements SyncSession, EventListener {
 			if (!generateRequestQueued.getAndSet(false))
 				throw new AssertionError();
 			try {
-				Request r;
-				Transaction txn = db.startTransaction(false);
-				try {
-					r = db.generateRequest(txn, contactId, MAX_MESSAGE_IDS);
-					db.commitTransaction(txn);
-				} finally {
-					db.endTransaction(txn);
-				}
+				Request r = db.transactionWithNullableResult(false, txn ->
+						db.generateRequest(txn, contactId, MAX_MESSAGE_IDS));
 				if (LOG.isLoggable(INFO))
 					LOG.info("Generated request: " + (r != null));
 				if (r != null) writerTasks.add(new WriteRequest(r));

bramble-core/src/main/java/org/briarproject/bramble/sync/IncomingSession.java

@@ -6,7 +6,6 @@ import org.briarproject.bramble.api.contact.event.ContactRemovedEvent;
 import org.briarproject.bramble.api.db.DatabaseComponent;
 import org.briarproject.bramble.api.db.DatabaseExecutor;
 import org.briarproject.bramble.api.db.DbException;
-import org.briarproject.bramble.api.db.Transaction;
 import org.briarproject.bramble.api.event.Event;
 import org.briarproject.bramble.api.event.EventBus;
 import org.briarproject.bramble.api.event.EventListener;
@@ -120,13 +119,8 @@ class IncomingSession implements SyncSession, EventListener {
 		@Override
 		public void run() {
 			try {
-				Transaction txn = db.startTransaction(false);
-				try {
-					db.receiveAck(txn, contactId, ack);
-					db.commitTransaction(txn);
-				} finally {
-					db.endTransaction(txn);
-				}
+				db.transaction(false, txn ->
+						db.receiveAck(txn, contactId, ack));
 			} catch (DbException e) {
 				logException(LOG, WARNING, e);
 				interrupt();
@@ -146,13 +140,8 @@ class IncomingSession implements SyncSession, EventListener {
 		@Override
 		public void run() {
 			try {
-				Transaction txn = db.startTransaction(false);
-				try {
-					db.receiveMessage(txn, contactId, message);
-					db.commitTransaction(txn);
-				} finally {
-					db.endTransaction(txn);
-				}
+				db.transaction(false, txn ->
+						db.receiveMessage(txn, contactId, message));
 			} catch (DbException e) {
 				logException(LOG, WARNING, e);
 				interrupt();
@@ -172,13 +161,8 @@ class IncomingSession implements SyncSession, EventListener {
 		@Override
 		public void run() {
 			try {
-				Transaction txn = db.startTransaction(false);
-				try {
-					db.receiveOffer(txn, contactId, offer);
-					db.commitTransaction(txn);
-				} finally {
-					db.endTransaction(txn);
-				}
+				db.transaction(false, txn ->
+						db.receiveOffer(txn, contactId, offer));
 			} catch (DbException e) {
 				logException(LOG, WARNING, e);
 				interrupt();
@@ -198,13 +182,8 @@ class IncomingSession implements SyncSession, EventListener {
 		@Override
 		public void run() {
 			try {
-				Transaction txn = db.startTransaction(false);
-				try {
-					db.receiveRequest(txn, contactId, request);
-					db.commitTransaction(txn);
-				} finally {
-					db.endTransaction(txn);
-				}
+				db.transaction(false, txn ->
+						db.receiveRequest(txn, contactId, request));
 			} catch (DbException e) {
 				logException(LOG, WARNING, e);
 				interrupt();

bramble-core/src/main/java/org/briarproject/bramble/sync/MessageFactoryImpl.java

@@ -36,6 +36,7 @@ class MessageFactoryImpl implements MessageFactory {
 
 	@Override
 	public Message createMessage(GroupId g, long timestamp, byte[] body) {
+		if (body.length == 0) throw new IllegalArgumentException();
 		if (body.length > MAX_MESSAGE_BODY_LENGTH)
 			throw new IllegalArgumentException();
 		MessageId id = getMessageId(g, timestamp, body);
@@ -54,7 +55,7 @@ class MessageFactoryImpl implements MessageFactory {
 
 	@Override
 	public Message createMessage(byte[] raw) {
-		if (raw.length < MESSAGE_HEADER_LENGTH)
+		if (raw.length <= MESSAGE_HEADER_LENGTH)
 			throw new IllegalArgumentException();
 		if (raw.length > MAX_MESSAGE_LENGTH)
 			throw new IllegalArgumentException();

bramble-core/src/main/java/org/briarproject/bramble/sync/SimplexOutgoingSession.java

@@ -5,7 +5,6 @@ import org.briarproject.bramble.api.contact.event.ContactRemovedEvent;
 import org.briarproject.bramble.api.db.DatabaseComponent;
 import org.briarproject.bramble.api.db.DatabaseExecutor;
 import org.briarproject.bramble.api.db.DbException;
-import org.briarproject.bramble.api.db.Transaction;
 import org.briarproject.bramble.api.event.Event;
 import org.briarproject.bramble.api.event.EventBus;
 import org.briarproject.bramble.api.event.EventListener;
@@ -47,7 +46,8 @@ class SimplexOutgoingSession implements SyncSession, EventListener {
 	private static final Logger LOG =
 			Logger.getLogger(SimplexOutgoingSession.class.getName());
 
-	private static final ThrowingRunnable<IOException> CLOSE = () -> {};
+	private static final ThrowingRunnable<IOException> CLOSE = () -> {
+	};
 
 	private final DatabaseComponent db;
 	private final Executor dbExecutor;
@@ -128,14 +128,8 @@ class SimplexOutgoingSession implements SyncSession, EventListener {
 		public void run() {
 			if (interrupted) return;
 			try {
-				Ack a;
-				Transaction txn = db.startTransaction(false);
-				try {
-					a = db.generateAck(txn, contactId, MAX_MESSAGE_IDS);
-					db.commitTransaction(txn);
-				} finally {
-					db.endTransaction(txn);
-				}
+				Ack a = db.transactionWithNullableResult(false, txn ->
+						db.generateAck(txn, contactId, MAX_MESSAGE_IDS));
 				if (LOG.isLoggable(INFO))
 					LOG.info("Generated ack: " + (a != null));
 				if (a == null) decrementOutstandingQueries();
@@ -172,15 +166,10 @@ class SimplexOutgoingSession implements SyncSession, EventListener {
 		public void run() {
 			if (interrupted) return;
 			try {
-				Collection<Message> b;
-				Transaction txn = db.startTransaction(false);
-				try {
-					b = db.generateBatch(txn, contactId,
-							MAX_RECORD_PAYLOAD_BYTES, maxLatency);
-					db.commitTransaction(txn);
-				} finally {
-					db.endTransaction(txn);
-				}
+				Collection<Message> b =
+						db.transactionWithNullableResult(false, txn ->
+								db.generateBatch(txn, contactId,
+										MAX_RECORD_PAYLOAD_BYTES, maxLatency));
 				if (LOG.isLoggable(INFO))
 					LOG.info("Generated batch: " + (b != null));
 				if (b == null) decrementOutstandingQueries();

bramble-core/src/main/java/org/briarproject/bramble/sync/SyncRecordReaderImpl.java

@@ -124,7 +124,8 @@ class SyncRecordReaderImpl implements SyncRecordReader {
 		if (!hasMessage()) throw new FormatException();
 		if (nextRecord == null) throw new AssertionError();
 		byte[] payload = nextRecord.getPayload();
-		if (payload.length < MESSAGE_HEADER_LENGTH) throw new FormatException();
+		if (payload.length <= MESSAGE_HEADER_LENGTH)
+			throw new FormatException();
 		// Validate timestamp
 		long timestamp = ByteUtils.readUint64(payload, UniqueId.LENGTH);
 		if (timestamp < 0) throw new FormatException();

bramble-core/src/main/java/org/briarproject/bramble/sync/ValidationManagerImpl.java

@@ -1,5 +1,6 @@
 package org.briarproject.bramble.sync;
 
+import org.briarproject.bramble.api.Pair;
 import org.briarproject.bramble.api.db.DatabaseComponent;
 import org.briarproject.bramble.api.db.DatabaseExecutor;
 import org.briarproject.bramble.api.db.DbException;
@@ -97,14 +98,8 @@ class ValidationManagerImpl implements ValidationManager, Service,
 	@DatabaseExecutor
 	private void validateOutstandingMessages() {
 		try {
-			Queue<MessageId> unvalidated = new LinkedList<>();
-			Transaction txn = db.startTransaction(true);
-			try {
-				unvalidated.addAll(db.getMessagesToValidate(txn));
-				db.commitTransaction(txn);
-			} finally {
-				db.endTransaction(txn);
-			}
+			Queue<MessageId> unvalidated = new LinkedList<>(
+					db.transactionWithResult(true, db::getMessagesToValidate));
 			validateNextMessageAsync(unvalidated);
 		} catch (DbException e) {
 			logException(LOG, WARNING, e);
@@ -119,18 +114,14 @@ class ValidationManagerImpl implements ValidationManager, Service,
 	@DatabaseExecutor
 	private void validateNextMessage(Queue<MessageId> unvalidated) {
 		try {
-			Message m;
-			Group g;
-			Transaction txn = db.startTransaction(true);
-			try {
+			Pair<Message, Group> mg = db.transactionWithResult(true, txn -> {
 				MessageId id = unvalidated.poll();
-				m = db.getMessage(txn, id);
-				g = db.getGroup(txn, m.getGroupId());
-				db.commitTransaction(txn);
-			} finally {
-				db.endTransaction(txn);
-			}
-			validateMessageAsync(m, g);
+				if (id == null) throw new AssertionError();
+				Message m = db.getMessage(txn, id);
+				Group g = db.getGroup(txn, m.getGroupId());
+				return new Pair<>(m, g);
+			});
+			validateMessageAsync(mg.getFirst(), mg.getSecond());
 			validateNextMessageAsync(unvalidated);
 		} catch (NoSuchMessageException e) {
 			LOG.info("Message removed before validation");
@@ -150,14 +141,8 @@ class ValidationManagerImpl implements ValidationManager, Service,
 	@DatabaseExecutor
 	private void deliverOutstandingMessages() {
 		try {
-			Queue<MessageId> pending = new LinkedList<>();
-			Transaction txn = db.startTransaction(true);
-			try {
-				pending.addAll(db.getPendingMessages(txn));
-				db.commitTransaction(txn);
-			} finally {
-				db.endTransaction(txn);
-			}
+			Queue<MessageId> pending = new LinkedList<>(
+					db.transactionWithResult(true, db::getPendingMessages));
 			deliverNextPendingMessageAsync(pending);
 		} catch (DbException e) {
 			logException(LOG, WARNING, e);
@@ -172,12 +157,12 @@ class ValidationManagerImpl implements ValidationManager, Service,
 	@DatabaseExecutor
 	private void deliverNextPendingMessage(Queue<MessageId> pending) {
 		try {
-			boolean anyInvalid = false, allDelivered = true;
-			Queue<MessageId> toShare = null;
-			Queue<MessageId> invalidate = null;
-			Transaction txn = db.startTransaction(false);
-			try {
+			Queue<MessageId> toShare = new LinkedList<>();
+			Queue<MessageId> invalidate = new LinkedList<>();
+			db.transaction(false, txn -> {
+				boolean anyInvalid = false, allDelivered = true;
 				MessageId id = pending.poll();
+				if (id == null) throw new AssertionError();
 				// Check if message is still pending
 				if (db.getMessageState(txn, id) == PENDING) {
 					// Check if dependencies are valid and delivered
@@ -189,7 +174,7 @@ class ValidationManagerImpl implements ValidationManager, Service,
 					}
 					if (anyInvalid) {
 						invalidateMessage(txn, id);
-						invalidate = getDependentsToInvalidate(txn, id);
+						addDependentsToInvalidate(txn, id, invalidate);
 					} else if (allDelivered) {
 						Message m = db.getMessage(txn, id);
 						Group g = db.getGroup(txn, m.getGroupId());
@@ -200,22 +185,19 @@ class ValidationManagerImpl implements ValidationManager, Service,
 						DeliveryResult result =
 								deliverMessage(txn, m, c, majorVersion, meta);
 						if (result.valid) {
-							pending.addAll(getPendingDependents(txn, id));
+							addPendingDependents(txn, id, pending);
 							if (result.share) {
 								db.setMessageShared(txn, id);
-								toShare = new LinkedList<>(states.keySet());
+								toShare.addAll(states.keySet());
 							}
 						} else {
-							invalidate = getDependentsToInvalidate(txn, id);
+							addDependentsToInvalidate(txn, id, invalidate);
 						}
 					}
 				}
-				db.commitTransaction(txn);
-			} finally {
-				db.endTransaction(txn);
-			}
-			if (invalidate != null) invalidateNextMessageAsync(invalidate);
-			if (toShare != null) shareNextMessageAsync(toShare);
+			});
+			if (!invalidate.isEmpty()) invalidateNextMessageAsync(invalidate);
+			if (!toShare.isEmpty()) shareNextMessageAsync(toShare);
 			deliverNextPendingMessageAsync(pending);
 		} catch (NoSuchMessageException e) {
 			LOG.info("Message removed before delivery");
@@ -264,12 +246,11 @@ class ValidationManagerImpl implements ValidationManager, Service,
 			MessageContext context) {
 		try {
 			MessageId id = m.getId();
-			boolean anyInvalid = false, allDelivered = true;
-			Queue<MessageId> invalidate = null;
-			Queue<MessageId> pending = null;
-			Queue<MessageId> toShare = null;
-			Transaction txn = db.startTransaction(false);
-			try {
+			Queue<MessageId> invalidate = new LinkedList<>();
+			Queue<MessageId> pending = new LinkedList<>();
+			Queue<MessageId> toShare = new LinkedList<>();
+			db.transaction(false, txn -> {
+				boolean anyInvalid = false, allDelivered = true;
 				// Check if message has any dependencies
 				Collection<MessageId> dependencies = context.getDependencies();
 				if (!dependencies.isEmpty()) {
@@ -285,7 +266,7 @@ class ValidationManagerImpl implements ValidationManager, Service,
 				if (anyInvalid) {
 					if (db.getMessageState(txn, id) != INVALID) {
 						invalidateMessage(txn, id);
-						invalidate = getDependentsToInvalidate(txn, id);
+						addDependentsToInvalidate(txn, id, invalidate);
 					}
 				} else {
 					Metadata meta = context.getMetadata();
@@ -294,25 +275,22 @@ class ValidationManagerImpl implements ValidationManager, Service,
 						DeliveryResult result =
 								deliverMessage(txn, m, c, majorVersion, meta);
 						if (result.valid) {
-							pending = getPendingDependents(txn, id);
+							addPendingDependents(txn, id, pending);
 							if (result.share) {
 								db.setMessageShared(txn, id);
-								toShare = new LinkedList<>(dependencies);
+								toShare.addAll(dependencies);
 							}
 						} else {
-							invalidate = getDependentsToInvalidate(txn, id);
+							addDependentsToInvalidate(txn, id, invalidate);
 						}
 					} else {
 						db.setMessageState(txn, id, PENDING);
 					}
 				}
-				db.commitTransaction(txn);
-			} finally {
-				db.endTransaction(txn);
-			}
-			if (invalidate != null) invalidateNextMessageAsync(invalidate);
-			if (pending != null) deliverNextPendingMessageAsync(pending);
-			if (toShare != null) shareNextMessageAsync(toShare);
+			});
+			if (!invalidate.isEmpty()) invalidateNextMessageAsync(invalidate);
+			if (!pending.isEmpty()) deliverNextPendingMessageAsync(pending);
+			if (!toShare.isEmpty()) shareNextMessageAsync(toShare);
 		} catch (NoSuchMessageException e) {
 			LOG.info("Message removed during validation");
 		} catch (NoSuchGroupException e) {
@@ -342,14 +320,12 @@ class ValidationManagerImpl implements ValidationManager, Service,
 	}
 
 	@DatabaseExecutor
-	private Queue<MessageId> getPendingDependents(Transaction txn, MessageId m)
-			throws DbException {
-		Queue<MessageId> pending = new LinkedList<>();
+	private void addPendingDependents(Transaction txn, MessageId m,
+			Queue<MessageId> pending) throws DbException {
 		Map<MessageId, State> states = db.getMessageDependents(txn, m);
 		for (Entry<MessageId, State> e : states.entrySet()) {
 			if (e.getValue() == PENDING) pending.add(e.getKey());
 		}
-		return pending;
 	}
 
 	private void shareOutstandingMessagesAsync() {
@@ -359,14 +335,8 @@ class ValidationManagerImpl implements ValidationManager, Service,
 	@DatabaseExecutor
 	private void shareOutstandingMessages() {
 		try {
-			Queue<MessageId> toShare = new LinkedList<>();
-			Transaction txn = db.startTransaction(true);
-			try {
-				toShare.addAll(db.getMessagesToShare(txn));
-				db.commitTransaction(txn);
-			} finally {
-				db.endTransaction(txn);
-			}
+			Queue<MessageId> toShare = new LinkedList<>(
+					db.transactionWithResult(true, db::getMessagesToShare));
 			shareNextMessageAsync(toShare);
 		} catch (DbException e) {
 			logException(LOG, WARNING, e);
@@ -387,15 +357,12 @@ class ValidationManagerImpl implements ValidationManager, Service,
 	@DatabaseExecutor
 	private void shareNextMessage(Queue<MessageId> toShare) {
 		try {
-			Transaction txn = db.startTransaction(false);
-			try {
+			db.transaction(false, txn -> {
 				MessageId id = toShare.poll();
+				if (id == null) throw new AssertionError();
 				db.setMessageShared(txn, id);
 				toShare.addAll(db.getMessageDependencies(txn, id).keySet());
-				db.commitTransaction(txn);
-			} finally {
-				db.endTransaction(txn);
-			}
+			});
 			shareNextMessageAsync(toShare);
 		} catch (NoSuchMessageException e) {
 			LOG.info("Message removed before sharing");
@@ -416,17 +383,14 @@ class ValidationManagerImpl implements ValidationManager, Service,
 	@DatabaseExecutor
 	private void invalidateNextMessage(Queue<MessageId> invalidate) {
 		try {
-			Transaction txn = db.startTransaction(false);
-			try {
+			db.transaction(false, txn -> {
 				MessageId id = invalidate.poll();
+				if (id == null) throw new AssertionError();
 				if (db.getMessageState(txn, id) != INVALID) {
 					invalidateMessage(txn, id);
-					invalidate.addAll(getDependentsToInvalidate(txn, id));
+					addDependentsToInvalidate(txn, id, invalidate);
 				}
-				db.commitTransaction(txn);
-			} finally {
-				db.endTransaction(txn);
-			}
+			});
 			invalidateNextMessageAsync(invalidate);
 		} catch (NoSuchMessageException e) {
 			LOG.info("Message removed before invalidation");
@@ -445,14 +409,12 @@ class ValidationManagerImpl implements ValidationManager, Service,
 	}
 
 	@DatabaseExecutor
-	private Queue<MessageId> getDependentsToInvalidate(Transaction txn,
-			MessageId m) throws DbException {
-		Queue<MessageId> invalidate = new LinkedList<>();
+	private void addDependentsToInvalidate(Transaction txn,
+			MessageId m, Queue<MessageId> invalidate) throws DbException {
 		Map<MessageId, State> states = db.getMessageDependents(txn, m);
 		for (Entry<MessageId, State> e : states.entrySet()) {
 			if (e.getValue() != INVALID) invalidate.add(e.getKey());
 		}
-		return invalidate;
 	}
 
 	@Override
@@ -472,14 +434,8 @@ class ValidationManagerImpl implements ValidationManager, Service,
 	@DatabaseExecutor
 	private void loadGroupAndValidate(Message m) {
 		try {
-			Group g;
-			Transaction txn = db.startTransaction(true);
-			try {
-				g = db.getGroup(txn, m.getGroupId());
-				db.commitTransaction(txn);
-			} finally {
-				db.endTransaction(txn);
-			}
+			Group g = db.transactionWithResult(true, txn ->
+					db.getGroup(txn, m.getGroupId()));
 			validateMessageAsync(m, g);
 		} catch (NoSuchGroupException e) {
 			LOG.info("Group removed before validation");

bramble-core/src/main/java/org/briarproject/bramble/transport/KeyManagerImpl.java

@@ -72,8 +72,7 @@ class KeyManagerImpl implements KeyManager, Service, EventListener {
 		for (DuplexPluginFactory f : pluginConfig.getDuplexFactories())
 			transports.put(f.getId(), f.getMaxLatency());
 		try {
-			Transaction txn = db.startTransaction(false);
-			try {
+			db.transaction(false, txn -> {
 				for (Contact c : db.getContacts(txn))
 					if (c.isActive()) activeContacts.put(c.getId(), true);
 				for (Entry<TransportId, Integer> e : transports.entrySet())
@@ -85,10 +84,7 @@ class KeyManagerImpl implements KeyManager, Service, EventListener {
 					managers.put(e.getKey(), m);
 					m.start(txn);
 				}
-				db.commitTransaction(txn);
-			} finally {
-				db.endTransaction(txn);
-			}
+			});
 		} catch (DbException e) {
 			throw new ServiceException(e);
 		}
@@ -141,15 +137,8 @@ class KeyManagerImpl implements KeyManager, Service, EventListener {
 			if (LOG.isLoggable(INFO)) LOG.info("No key manager for " + t);
 			return null;
 		}
-		StreamContext ctx;
-		Transaction txn = db.startTransaction(false);
-		try {
-			ctx = m.getStreamContext(txn, c);
-			db.commitTransaction(txn);
-		} finally {
-			db.endTransaction(txn);
-		}
-		return ctx;
+		return db.transactionWithNullableResult(false, txn ->
+				m.getStreamContext(txn, c));
 	}
 
 	@Override
@@ -160,15 +149,8 @@ class KeyManagerImpl implements KeyManager, Service, EventListener {
 			if (LOG.isLoggable(INFO)) LOG.info("No key manager for " + t);
 			return null;
 		}
-		StreamContext ctx;
-		Transaction txn = db.startTransaction(false);
-		try {
-			ctx = m.getStreamContext(txn, tag);
-			db.commitTransaction(txn);
-		} finally {
-			db.endTransaction(txn);
-		}
-		return ctx;
+		return db.transactionWithNullableResult(false, txn ->
+				m.getStreamContext(txn, tag));
 	}
 
 	@Override

bramble-core/src/main/java/org/briarproject/bramble/transport/TransportKeyManagerImpl.java

@@ -162,13 +162,7 @@ class TransportKeyManagerImpl implements TransportKeyManager {
 	private void rotateKeys() {
 		dbExecutor.execute(() -> {
 			try {
-				Transaction txn = db.startTransaction(false);
-				try {
-					rotateKeys(txn);
-					db.commitTransaction(txn);
-				} finally {
-					db.endTransaction(txn);
-				}
+				db.transaction(false, this::rotateKeys);
 			} catch (DbException e) {
 				logException(LOG, WARNING, e);
 			}

bramble-core/src/main/java/org/briarproject/bramble/versioning/ClientVersioningManagerImpl.java

@@ -123,16 +123,12 @@ class ClientVersioningManagerImpl implements ClientVersioningManager, Client,
 		List<ClientVersion> versions = new ArrayList<>(clients);
 		Collections.sort(versions);
 		try {
-			Transaction txn = db.startTransaction(false);
-			try {
+			db.transaction(false, txn -> {
 				if (updateClientVersions(txn, versions)) {
 					for (Contact c : db.getContacts(txn))
 						clientVersionsUpdated(txn, c, versions);
 				}
-				db.commitTransaction(txn);
-			} finally {
-				db.endTransaction(txn);
-			}
+			});
 		} catch (DbException e) {
 			throw new ServiceException(e);
 		}

bramble-core/src/main/resources/bridges

@@ -1,8 +1,4 @@
-Bridge 131.252.210.150:8081 0E858AC201BF0F3FA3C462F64844CBFFC7297A42
-Bridge 67.205.189.122:8443 12D64D5D44E20169585E7378580C0D33A872AD98
-Bridge 45.32.148.146:8443 0CE016FB2462D8BF179AE71F7D702D09DEAC3F1D
-Bridge 148.251.90.59:7510 019F727CA6DCA6CA5C90B55E477B7D87981E75BC
-Bridge 45.55.1.74:8443 6F18FEFBB0CAECD5ABA755312FCCB34FC11A7AB8
-Bridge 85.229.131.78:444 50E433CCC5FEC11CC34CB4D92033561E065EA106
-Bridge 178.62.62.193:8443 391B1F9B6A28A1C5FAE1872283985F975E5DB029
-Bridge 45.76.29.92:8443 ECF1DD51A46FDEF2C50CED992EEEAE8DED18DA0C
+Bridge obfs4 78.46.188.239:37356 5A2D2F4158D0453E00C7C176978D3F41D69C45DB cert=3c0SwxpOisbohNxEc4tb875RVW8eOu1opRTVXJhafaKA/PNNtI7ElQIVOVZg1AdL5bxGCw iat-mode=0
+Bridge obfs4 52.15.78.72:9443 02069A3C5362476936B62BA6F5ACC41ABD573A9B cert=ijYG/OKc7kqu2YzKNFfeXN7/BG2BOgfEP2KyYEiGDQthnHbsOiTWHeIG0WJVW+BckzDgKw iat-mode=0
+Bridge obfs4 13.58.29.242:9443 0C58939A77DA6B6B29D4B5236A75865659607AE0 cert=OylWIEHb/ezpq1zWxW0sgKRn+9ARH2eOcQOZ8/Gew+4l+oKOhQ2jUX/Y+FSl61JorXZUWA iat-mode=0
+Bridge obfs4 45.33.37.112:9443 60A609BB4ABE8D46E634AE81ED29ADAB7776B399 cert=t5v19WmNv5Sc2YPNr8RQids365W7MY8zJwQVkOxBjUMFomMWARDzsbYpcWLLcw0J9Gm+BQ iat-mode=0

bramble-core/src/test/java/org/briarproject/bramble/client/BdfMessageValidatorTest.java

@@ -79,18 +79,6 @@ public class BdfMessageValidatorTest extends ValidatorTestCase {
 		assertSame(meta, messageContext.getMetadata());
 	}
 
-	@Test(expected = InvalidMessageException.class)
-	public void testRejectsTooShortMessage() throws Exception {
-		Message invalidMessage = getMessage(groupId, 0);
-
-		context.checking(new Expectations() {{
-			oneOf(clock).currentTimeMillis();
-			will(returnValue(timestamp));
-		}});
-
-		failIfSubclassIsCalled.validateMessage(invalidMessage, group);
-	}
-
 	@Test
 	public void testAcceptsMinLengthMessage() throws Exception {
 		Message shortMessage = getMessage(groupId, 1);

bramble-core/src/test/java/org/briarproject/bramble/client/ClientHelperImplTest.java

@@ -22,6 +22,7 @@ import org.briarproject.bramble.api.sync.Message;
 import org.briarproject.bramble.api.sync.MessageFactory;
 import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.bramble.test.BrambleTestCase;
+import org.briarproject.bramble.test.DbExpectations;
 import org.briarproject.bramble.util.StringUtils;
 import org.jmock.Expectations;
 import org.jmock.Mockery;
@@ -85,14 +86,11 @@ public class ClientHelperImplTest extends BrambleTestCase {
 		boolean shared = new Random().nextBoolean();
 		Transaction txn = new Transaction(null, false);
 
-		context.checking(new Expectations() {{
-			oneOf(db).startTransaction(false);
-			will(returnValue(txn));
+		context.checking(new DbExpectations() {{
+			oneOf(db).transaction(with(false), withDbRunnable(txn));
 			oneOf(metadataEncoder).encode(dictionary);
 			will(returnValue(metadata));
 			oneOf(db).addLocalMessage(txn, message, metadata, shared);
-			oneOf(db).commitTransaction(txn);
-			oneOf(db).endTransaction(txn);
 		}});
 
 		clientHelper.addLocalMessage(message, dictionary, shared);
@@ -116,13 +114,10 @@ public class ClientHelperImplTest extends BrambleTestCase {
 		Transaction txn = new Transaction(null, true);
 
 		expectToList(true);
-		context.checking(new Expectations() {{
-			oneOf(db).startTransaction(true);
-			will(returnValue(txn));
+		context.checking(new DbExpectations() {{
+			oneOf(db).transactionWithResult(with(true), withDbCallable(txn));
 			oneOf(db).getMessage(txn, messageId);
 			will(returnValue(message));
-			oneOf(db).commitTransaction(txn);
-			oneOf(db).endTransaction(txn);
 		}});
 
 		clientHelper.getMessageAsList(messageId);
@@ -133,15 +128,12 @@ public class ClientHelperImplTest extends BrambleTestCase {
 	public void testGetGroupMetadataAsDictionary() throws Exception {
 		Transaction txn = new Transaction(null, true);
 
-		context.checking(new Expectations() {{
-			oneOf(db).startTransaction(true);
-			will(returnValue(txn));
+		context.checking(new DbExpectations() {{
+			oneOf(db).transactionWithResult(with(true), withDbCallable(txn));
 			oneOf(db).getGroupMetadata(txn, groupId);
 			will(returnValue(metadata));
 			oneOf(metadataParser).parse(metadata);
 			will(returnValue(dictionary));
-			oneOf(db).commitTransaction(txn);
-			oneOf(db).endTransaction(txn);
 		}});
 
 		assertEquals(dictionary,
@@ -153,15 +145,12 @@ public class ClientHelperImplTest extends BrambleTestCase {
 	public void testGetMessageMetadataAsDictionary() throws Exception {
 		Transaction txn = new Transaction(null, true);
 
-		context.checking(new Expectations() {{
-			oneOf(db).startTransaction(true);
-			will(returnValue(txn));
+		context.checking(new DbExpectations() {{
+			oneOf(db).transactionWithResult(with(true), withDbCallable(txn));
 			oneOf(db).getMessageMetadata(txn, messageId);
 			will(returnValue(metadata));
 			oneOf(metadataParser).parse(metadata);
 			will(returnValue(dictionary));
-			oneOf(db).commitTransaction(txn);
-			oneOf(db).endTransaction(txn);
 		}});
 
 		assertEquals(dictionary,
@@ -175,15 +164,12 @@ public class ClientHelperImplTest extends BrambleTestCase {
 		map.put(messageId, dictionary);
 		Transaction txn = new Transaction(null, true);
 
-		context.checking(new Expectations() {{
-			oneOf(db).startTransaction(true);
-			will(returnValue(txn));
+		context.checking(new DbExpectations() {{
+			oneOf(db).transactionWithResult(with(true), withDbCallable(txn));
 			oneOf(db).getMessageMetadata(txn, groupId);
 			will(returnValue(Collections.singletonMap(messageId, metadata)));
 			oneOf(metadataParser).parse(metadata);
 			will(returnValue(dictionary));
-			oneOf(db).commitTransaction(txn);
-			oneOf(db).endTransaction(txn);
 		}});
 
 		assertEquals(map, clientHelper.getMessageMetadataAsDictionary(groupId));
@@ -200,17 +186,14 @@ public class ClientHelperImplTest extends BrambleTestCase {
 		queryMetadata.put("query", getRandomBytes(42));
 		Transaction txn = new Transaction(null, true);
 
-		context.checking(new Expectations() {{
-			oneOf(db).startTransaction(true);
-			will(returnValue(txn));
+		context.checking(new DbExpectations() {{
+			oneOf(db).transactionWithResult(with(true), withDbCallable(txn));
 			oneOf(metadataEncoder).encode(query);
 			will(returnValue(queryMetadata));
 			oneOf(db).getMessageMetadata(txn, groupId, queryMetadata);
 			will(returnValue(Collections.singletonMap(messageId, metadata)));
 			oneOf(metadataParser).parse(metadata);
 			will(returnValue(dictionary));
-			oneOf(db).commitTransaction(txn);
-			oneOf(db).endTransaction(txn);
 		}});
 
 		assertEquals(map,
@@ -222,14 +205,11 @@ public class ClientHelperImplTest extends BrambleTestCase {
 	public void testMergeGroupMetadata() throws Exception {
 		Transaction txn = new Transaction(null, false);
 
-		context.checking(new Expectations() {{
-			oneOf(db).startTransaction(false);
-			will(returnValue(txn));
+		context.checking(new DbExpectations() {{
+			oneOf(db).transaction(with(false), withDbRunnable(txn));
 			oneOf(metadataEncoder).encode(dictionary);
 			will(returnValue(metadata));
 			oneOf(db).mergeGroupMetadata(txn, groupId, metadata);
-			oneOf(db).commitTransaction(txn);
-			oneOf(db).endTransaction(txn);
 		}});
 
 		clientHelper.mergeGroupMetadata(groupId, dictionary);
@@ -240,14 +220,11 @@ public class ClientHelperImplTest extends BrambleTestCase {
 	public void testMergeMessageMetadata() throws Exception {
 		Transaction txn = new Transaction(null, false);
 
-		context.checking(new Expectations() {{
-			oneOf(db).startTransaction(false);
-			will(returnValue(txn));
+		context.checking(new DbExpectations() {{
+			oneOf(db).transaction(with(false), withDbRunnable(txn));
 			oneOf(metadataEncoder).encode(dictionary);
 			will(returnValue(metadata));
 			oneOf(db).mergeMessageMetadata(txn, messageId, metadata);
-			oneOf(db).commitTransaction(txn);
-			oneOf(db).endTransaction(txn);
 		}});
 
 		clientHelper.mergeMessageMetadata(messageId, dictionary);

bramble-core/src/test/java/org/briarproject/bramble/contact/ContactManagerImplTest.java

@@ -5,12 +5,17 @@ import org.briarproject.bramble.api.contact.ContactId;
 import org.briarproject.bramble.api.contact.ContactManager;
 import org.briarproject.bramble.api.crypto.SecretKey;
 import org.briarproject.bramble.api.db.DatabaseComponent;
+import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.db.NoSuchContactException;
 import org.briarproject.bramble.api.db.Transaction;
 import org.briarproject.bramble.api.identity.Author;
 import org.briarproject.bramble.api.identity.AuthorId;
+import org.briarproject.bramble.api.identity.AuthorInfo;
+import org.briarproject.bramble.api.identity.IdentityManager;
+import org.briarproject.bramble.api.identity.LocalAuthor;
 import org.briarproject.bramble.api.transport.KeyManager;
 import org.briarproject.bramble.test.BrambleMockTestCase;
+import org.briarproject.bramble.test.DbExpectations;
 import org.jmock.Expectations;
 import org.jmock.Mockery;
 import org.junit.Test;
@@ -20,10 +25,20 @@ import java.util.Collection;
 import java.util.Collections;
 import java.util.Random;
 
+import static java.util.Collections.emptyList;
+import static java.util.Collections.singletonList;
+import static org.briarproject.bramble.api.identity.AuthorConstants.MAX_AUTHOR_NAME_LENGTH;
+import static org.briarproject.bramble.api.identity.AuthorInfo.Status.OURSELVES;
+import static org.briarproject.bramble.api.identity.AuthorInfo.Status.UNKNOWN;
+import static org.briarproject.bramble.api.identity.AuthorInfo.Status.UNVERIFIED;
+import static org.briarproject.bramble.api.identity.AuthorInfo.Status.VERIFIED;
 import static org.briarproject.bramble.test.TestUtils.getAuthor;
+import static org.briarproject.bramble.test.TestUtils.getLocalAuthor;
 import static org.briarproject.bramble.test.TestUtils.getRandomId;
 import static org.briarproject.bramble.test.TestUtils.getSecretKey;
+import static org.briarproject.bramble.util.StringUtils.getRandomString;
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNull;
 import static org.junit.Assert.assertTrue;
 
 public class ContactManagerImplTest extends BrambleMockTestCase {
@@ -31,16 +46,20 @@ public class ContactManagerImplTest extends BrambleMockTestCase {
 	private final Mockery context = new Mockery();
 	private final DatabaseComponent db = context.mock(DatabaseComponent.class);
 	private final KeyManager keyManager = context.mock(KeyManager.class);
+	private final IdentityManager identityManager =
+			context.mock(IdentityManager.class);
 	private final ContactManager contactManager;
 	private final ContactId contactId = new ContactId(42);
 	private final Author remote = getAuthor();
 	private final AuthorId local = new AuthorId(getRandomId());
+	private final LocalAuthor localAuthor = getLocalAuthor();
+	private final String alias = getRandomString(MAX_AUTHOR_NAME_LENGTH);
 	private final boolean verified = false, active = true;
 	private final Contact contact =
-			new Contact(contactId, remote, local, verified, active);
+			new Contact(contactId, remote, local, alias, verified, active);
 
 	public ContactManagerImplTest() {
-		contactManager = new ContactManagerImpl(db, keyManager);
+		contactManager = new ContactManagerImpl(db, keyManager, identityManager);
 	}
 
 	@Test
@@ -50,17 +69,14 @@ public class ContactManagerImplTest extends BrambleMockTestCase {
 		boolean alice = new Random().nextBoolean();
 		Transaction txn = new Transaction(null, false);
 
-		context.checking(new Expectations() {{
-			oneOf(db).startTransaction(false);
-			will(returnValue(txn));
+		context.checking(new DbExpectations() {{
+			oneOf(db).transactionWithResult(with(false), withDbCallable(txn));
 			oneOf(db).addContact(txn, remote, local, verified, active);
 			will(returnValue(contactId));
 			oneOf(keyManager).addContact(txn, contactId, master, timestamp,
 					alice, active);
 			oneOf(db).getContact(txn, contactId);
 			will(returnValue(contact));
-			oneOf(db).commitTransaction(txn);
-			oneOf(db).endTransaction(txn);
 		}});
 
 		assertEquals(contactId, contactManager.addContact(remote, local,
@@ -70,13 +86,10 @@ public class ContactManagerImplTest extends BrambleMockTestCase {
 	@Test
 	public void testGetContact() throws Exception {
 		Transaction txn = new Transaction(null, true);
-		context.checking(new Expectations() {{
-			oneOf(db).startTransaction(true);
-			will(returnValue(txn));
+		context.checking(new DbExpectations() {{
+			oneOf(db).transactionWithResult(with(true), withDbCallable(txn));
 			oneOf(db).getContact(txn, contactId);
 			will(returnValue(contact));
-			oneOf(db).commitTransaction(txn);
-			oneOf(db).endTransaction(txn);
 		}});
 
 		assertEquals(contact, contactManager.getContact(contactId));
@@ -86,13 +99,10 @@ public class ContactManagerImplTest extends BrambleMockTestCase {
 	public void testGetContactByAuthor() throws Exception {
 		Transaction txn = new Transaction(null, true);
 		Collection<Contact> contacts = Collections.singleton(contact);
-		context.checking(new Expectations() {{
-			oneOf(db).startTransaction(true);
-			will(returnValue(txn));
+		context.checking(new DbExpectations() {{
+			oneOf(db).transactionWithResult(with(true), withDbCallable(txn));
 			oneOf(db).getContactsByAuthorId(txn, remote.getId());
 			will(returnValue(contacts));
-			oneOf(db).commitTransaction(txn);
-			oneOf(db).endTransaction(txn);
 		}});
 
 		assertEquals(contact, contactManager.getContact(remote.getId(), local));
@@ -101,12 +111,10 @@ public class ContactManagerImplTest extends BrambleMockTestCase {
 	@Test(expected = NoSuchContactException.class)
 	public void testGetContactByUnknownAuthor() throws Exception {
 		Transaction txn = new Transaction(null, true);
-		context.checking(new Expectations() {{
-			oneOf(db).startTransaction(true);
-			will(returnValue(txn));
+		context.checking(new DbExpectations() {{
+			oneOf(db).transactionWithResult(with(true), withDbCallable(txn));
 			oneOf(db).getContactsByAuthorId(txn, remote.getId());
-			will(returnValue(Collections.emptyList()));
-			oneOf(db).endTransaction(txn);
+			will(returnValue(emptyList()));
 		}});
 
 		contactManager.getContact(remote.getId(), local);
@@ -116,30 +124,26 @@ public class ContactManagerImplTest extends BrambleMockTestCase {
 	public void testGetContactByUnknownLocalAuthor() throws Exception {
 		Transaction txn = new Transaction(null, true);
 		Collection<Contact> contacts = Collections.singleton(contact);
-		context.checking(new Expectations() {{
-			oneOf(db).startTransaction(true);
-			will(returnValue(txn));
+		context.checking(new DbExpectations() {{
+			oneOf(db).transactionWithResult(with(true), withDbCallable(txn));
 			oneOf(db).getContactsByAuthorId(txn, remote.getId());
 			will(returnValue(contacts));
-			oneOf(db).endTransaction(txn);
 		}});
 
 		contactManager.getContact(remote.getId(), new AuthorId(getRandomId()));
 	}
 
 	@Test
-	public void testActiveContacts() throws Exception {
+	public void testGetActiveContacts() throws Exception {
 		Collection<Contact> activeContacts = Collections.singletonList(contact);
 		Collection<Contact> contacts = new ArrayList<>(activeContacts);
-		contacts.add(new Contact(new ContactId(3), remote, local, true, false));
+		contacts.add(new Contact(new ContactId(3), remote, local, alias, true,
+				false));
 		Transaction txn = new Transaction(null, true);
-		context.checking(new Expectations() {{
-			oneOf(db).startTransaction(true);
-			will(returnValue(txn));
+		context.checking(new DbExpectations() {{
+			oneOf(db).transactionWithResult(with(true), withDbCallable(txn));
 			oneOf(db).getContacts(txn);
 			will(returnValue(contacts));
-			oneOf(db).commitTransaction(txn);
-			oneOf(db).endTransaction(txn);
 		}});
 
 		assertEquals(activeContacts, contactManager.getActiveContacts());
@@ -148,14 +152,11 @@ public class ContactManagerImplTest extends BrambleMockTestCase {
 	@Test
 	public void testRemoveContact() throws Exception {
 		Transaction txn = new Transaction(null, false);
-		context.checking(new Expectations() {{
-			oneOf(db).startTransaction(false);
-			will(returnValue(txn));
+		context.checking(new DbExpectations() {{
+			oneOf(db).transaction(with(false), withDbRunnable(txn));
 			oneOf(db).getContact(txn, contactId);
 			will(returnValue(contact));
 			oneOf(db).removeContact(txn, contactId);
-			oneOf(db).commitTransaction(txn);
-			oneOf(db).endTransaction(txn);
 		}});
 
 		contactManager.removeContact(contactId);
@@ -171,19 +172,108 @@ public class ContactManagerImplTest extends BrambleMockTestCase {
 		contactManager.setContactActive(txn, contactId, active);
 	}
 
+	@Test
+	public void testSetContactAlias() throws Exception {
+		Transaction txn = new Transaction(null, false);
+		context.checking(new DbExpectations() {{
+			oneOf(db).transaction(with(false), withDbRunnable(txn));
+			oneOf(db).setContactAlias(txn, contactId, alias);
+		}});
+
+		contactManager.setContactAlias(contactId, alias);
+	}
+
+	@Test(expected = IllegalArgumentException.class)
+	public void testSetContactAliasTooLong() throws Exception {
+		Transaction txn = new Transaction(null, false);
+		contactManager.setContactAlias(txn, contactId,
+				getRandomString(MAX_AUTHOR_NAME_LENGTH + 1));
+	}
+
 	@Test
 	public void testContactExists() throws Exception {
 		Transaction txn = new Transaction(null, true);
-		context.checking(new Expectations() {{
-			oneOf(db).startTransaction(true);
-			will(returnValue(txn));
+		context.checking(new DbExpectations() {{
+			oneOf(db).transactionWithResult(with(true), withDbCallable(txn));
 			oneOf(db).containsContact(txn, remote.getId(), local);
 			will(returnValue(true));
-			oneOf(db).commitTransaction(txn);
-			oneOf(db).endTransaction(txn);
 		}});
 
 		assertTrue(contactManager.contactExists(remote.getId(), local));
 	}
 
+	@Test
+	public void testGetAuthorInfo() throws Exception {
+		Transaction txn = new Transaction(null, true);
+		Collection<Contact> contacts = singletonList(
+				new Contact(new ContactId(1), remote, localAuthor.getId(),
+						alias, false, true));
+
+		context.checking(new DbExpectations() {{
+			oneOf(db).transactionWithResult(with(true), withDbCallable(txn));
+			oneOf(identityManager).getLocalAuthor(txn);
+			will(returnValue(localAuthor));
+			oneOf(db).getContactsByAuthorId(txn, remote.getId());
+			will(returnValue(contacts));
+		}});
+		AuthorInfo authorInfo =
+				contactManager.getAuthorInfo(txn, remote.getId());
+		assertEquals(UNVERIFIED, authorInfo.getStatus());
+		assertEquals(alias, contact.getAlias());
+	}
+
+	@Test
+	public void testGetAuthorInfoTransaction() throws DbException {
+		Transaction txn = new Transaction(null, true);
+
+		// check unknown author
+		context.checking(new Expectations() {{
+			oneOf(identityManager).getLocalAuthor(txn);
+			will(returnValue(localAuthor));
+			oneOf(db).getContactsByAuthorId(txn, remote.getId());
+			will(returnValue(emptyList()));
+		}});
+		AuthorInfo authorInfo =
+				contactManager.getAuthorInfo(txn, remote.getId());
+		assertEquals(UNKNOWN, authorInfo.getStatus());
+		assertNull(authorInfo.getAlias());
+
+		// check unverified contact
+		Collection<Contact> contacts = singletonList(
+				new Contact(new ContactId(1), remote, localAuthor.getId(),
+						alias, false, true));
+		checkAuthorInfoContext(txn, remote.getId(), contacts);
+		authorInfo = contactManager.getAuthorInfo(txn, remote.getId());
+		assertEquals(UNVERIFIED, authorInfo.getStatus());
+		assertEquals(alias, contact.getAlias());
+
+		// check verified contact
+		contacts = singletonList(new Contact(new ContactId(1), remote,
+				localAuthor.getId(), alias, true, true));
+		checkAuthorInfoContext(txn, remote.getId(), contacts);
+		authorInfo = contactManager.getAuthorInfo(txn, remote.getId());
+		assertEquals(VERIFIED, authorInfo.getStatus());
+		assertEquals(alias, contact.getAlias());
+
+		// check ourselves
+		context.checking(new Expectations() {{
+			oneOf(identityManager).getLocalAuthor(txn);
+			will(returnValue(localAuthor));
+			never(db).getContactsByAuthorId(txn, remote.getId());
+		}});
+		authorInfo = contactManager.getAuthorInfo(txn, localAuthor.getId());
+		assertEquals(OURSELVES, authorInfo.getStatus());
+		assertNull(authorInfo.getAlias());
+	}
+
+	private void checkAuthorInfoContext(Transaction txn, AuthorId authorId,
+			Collection<Contact> contacts) throws DbException {
+		context.checking(new Expectations() {{
+			oneOf(identityManager).getLocalAuthor(txn);
+			will(returnValue(localAuthor));
+			oneOf(db).getContactsByAuthorId(txn, authorId);
+			will(returnValue(contacts));
+		}});
+	}
+
 }

bramble-core/src/test/java/org/briarproject/bramble/data/BdfReaderImplFuzzingTest.java

@@ -0,0 +1,41 @@
+package org.briarproject.bramble.data;
+
+import org.briarproject.bramble.test.BrambleTestCase;
+import org.junit.Before;
+import org.junit.Test;
+
+import java.io.ByteArrayInputStream;
+import java.util.Random;
+
+import static org.briarproject.bramble.api.data.BdfReader.DEFAULT_MAX_BUFFER_SIZE;
+import static org.briarproject.bramble.api.data.BdfReader.DEFAULT_NESTED_LIMIT;
+import static org.briarproject.bramble.test.TestUtils.isOptionalTestEnabled;
+import static org.junit.Assert.assertTrue;
+import static org.junit.Assume.assumeTrue;
+
+public class BdfReaderImplFuzzingTest extends BrambleTestCase {
+
+	@Before
+	public void setUp() {
+		assumeTrue(isOptionalTestEnabled(BdfReaderImplFuzzingTest.class));
+	}
+
+	@Test
+	public void testStringFuzzing() throws Exception {
+		Random random = new Random();
+		byte[] buf = new byte[22];
+		ByteArrayInputStream in = new ByteArrayInputStream(buf);
+		for (int i = 0; i < 100_000_000; i++) {
+			random.nextBytes(buf);
+			buf[0] = 0x41; // String with 1-byte length
+			buf[1] = 0x14; // Length 20 bytes
+			in.reset();
+			BdfReaderImpl r = new BdfReaderImpl(in, DEFAULT_NESTED_LIMIT,
+					DEFAULT_MAX_BUFFER_SIZE);
+			int length = r.readString().length();
+			assertTrue(length >= 0);
+			assertTrue(length <= 20);
+			assertTrue(r.eof());
+		}
+	}
+}

bramble-core/src/test/java/org/briarproject/bramble/db/JdbcDatabaseTest.java

@@ -26,11 +26,10 @@ import org.briarproject.bramble.api.transport.KeySetId;
 import org.briarproject.bramble.api.transport.OutgoingKeys;
 import org.briarproject.bramble.api.transport.TransportKeys;
 import org.briarproject.bramble.system.SystemClock;
-import org.briarproject.bramble.test.ArrayClock;
 import org.briarproject.bramble.test.BrambleTestCase;
+import org.briarproject.bramble.test.SettableClock;
 import org.briarproject.bramble.test.TestDatabaseConfig;
 import org.briarproject.bramble.test.TestMessageFactory;
-import org.briarproject.bramble.test.TestUtils;
 import org.junit.After;
 import org.junit.Before;
 import org.junit.Test;
@@ -46,6 +45,7 @@ import java.util.Map.Entry;
 import java.util.Random;
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.atomic.AtomicLong;
 
 import static java.util.Collections.emptyList;
 import static java.util.Collections.emptyMap;
@@ -53,6 +53,7 @@ import static java.util.Collections.singletonList;
 import static java.util.Collections.singletonMap;
 import static java.util.concurrent.TimeUnit.SECONDS;
 import static org.briarproject.bramble.api.db.Metadata.REMOVE;
+import static org.briarproject.bramble.api.identity.AuthorConstants.MAX_AUTHOR_NAME_LENGTH;
 import static org.briarproject.bramble.api.sync.Group.Visibility.INVISIBLE;
 import static org.briarproject.bramble.api.sync.Group.Visibility.SHARED;
 import static org.briarproject.bramble.api.sync.Group.Visibility.VISIBLE;
@@ -61,6 +62,9 @@ import static org.briarproject.bramble.api.sync.ValidationManager.State.DELIVERE
 import static org.briarproject.bramble.api.sync.ValidationManager.State.INVALID;
 import static org.briarproject.bramble.api.sync.ValidationManager.State.PENDING;
 import static org.briarproject.bramble.api.sync.ValidationManager.State.UNKNOWN;
+import static org.briarproject.bramble.db.DatabaseConstants.DB_SETTINGS_NAMESPACE;
+import static org.briarproject.bramble.db.DatabaseConstants.LAST_COMPACTED_KEY;
+import static org.briarproject.bramble.db.DatabaseConstants.MAX_COMPACTION_INTERVAL_MS;
 import static org.briarproject.bramble.test.TestUtils.deleteTestDirectory;
 import static org.briarproject.bramble.test.TestUtils.getAuthor;
 import static org.briarproject.bramble.test.TestUtils.getClientId;
@@ -71,6 +75,7 @@ import static org.briarproject.bramble.test.TestUtils.getRandomId;
 import static org.briarproject.bramble.test.TestUtils.getSecretKey;
 import static org.briarproject.bramble.test.TestUtils.getTestDirectory;
 import static org.briarproject.bramble.test.TestUtils.getTransportId;
+import static org.briarproject.bramble.util.StringUtils.getRandomString;
 import static org.junit.Assert.assertArrayEquals;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
@@ -1710,6 +1715,39 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 		db.close();
 	}
 
+	@Test
+	public void testSetContactAlias() throws Exception {
+		Database<Connection> db = open(false);
+		Connection txn = db.startTransaction();
+
+		// Add a contact
+		db.addLocalAuthor(txn, localAuthor);
+		assertEquals(contactId, db.addContact(txn, author, localAuthor.getId(),
+				true, true));
+
+		// The contact should have no alias
+		Contact contact = db.getContact(txn, contactId);
+		assertNull(contact.getAlias());
+
+		// Set a contact alias
+		String alias = getRandomString(MAX_AUTHOR_NAME_LENGTH);
+		db.setContactAlias(txn, contactId, alias);
+
+		// The contact should have an alias
+		contact = db.getContact(txn, contactId);
+		assertEquals(alias, contact.getAlias());
+
+		// Set the contact alias null
+		db.setContactAlias(txn, contactId, null);
+
+		// The contact should have no alias
+		contact = db.getContact(txn, contactId);
+		assertNull(contact.getAlias());
+
+		db.commitTransaction(txn);
+		db.close();
+	}
+
 	@Test
 	public void testSetMessageState() throws Exception {
 		Database<Connection> db = open(false);
@@ -1818,10 +1856,9 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 	@Test
 	public void testMessageRetransmission() throws Exception {
 		long now = System.currentTimeMillis();
-		long steps[] = {now, now, now + MAX_LATENCY * 2 - 1,
-				now + MAX_LATENCY * 2};
+		AtomicLong time = new AtomicLong(now);
 		Database<Connection> db =
-				open(false, new TestMessageFactory(), new ArrayClock(steps));
+				open(false, new TestMessageFactory(), new SettableClock(time));
 		Connection txn = db.startTransaction();
 
 		// Add a contact, a shared group and a shared message
@@ -1847,11 +1884,13 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 
 		// Time: now + MAX_LATENCY * 2 - 1
 		// The message should not yet be sendable
+		time.set(now + MAX_LATENCY * 2 - 1);
 		ids = db.getMessagesToSend(txn, contactId, ONE_MEGABYTE, MAX_LATENCY);
 		assertTrue(ids.isEmpty());
 
 		// Time: now + MAX_LATENCY * 2
 		// The message should have expired and should now be sendable
+		time.set(now + MAX_LATENCY * 2);
 		ids = db.getMessagesToSend(txn, contactId, ONE_MEGABYTE, MAX_LATENCY);
 		assertEquals(singletonList(messageId), ids);
 
@@ -1859,13 +1898,12 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 		db.close();
 	}
 
-
 	@Test
 	public void testFasterMessageRetransmission() throws Exception {
 		long now = System.currentTimeMillis();
-		long steps[] = {now, now, now, now, now + 1};
+		AtomicLong time = new AtomicLong(now);
 		Database<Connection> db =
-				open(false, new TestMessageFactory(), new ArrayClock(steps));
+				open(false, new TestMessageFactory(), new SettableClock(time));
 		Connection txn = db.startTransaction();
 
 		// Add a contact, a shared group and a shared message
@@ -1903,6 +1941,7 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 		// Time: now + 1
 		// The message should no longer be sendable via the faster transport,
 		// as the ETA is now equal
+		time.set(now + 1);
 		ids = db.getMessagesToSend(txn, contactId, ONE_MEGABYTE,
 				MAX_LATENCY - 1);
 		assertTrue(ids.isEmpty());
@@ -1911,6 +1950,45 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 		db.close();
 	}
 
+	@Test
+	public void testCompactionTime() throws Exception {
+		MessageFactory messageFactory = new TestMessageFactory();
+		long now = System.currentTimeMillis();
+		AtomicLong time = new AtomicLong(now);
+		Clock clock = new SettableClock(time);
+
+		// Time: now
+		// The last compaction time should be initialised to the current time
+		Database<Connection> db = open(false, messageFactory, clock);
+		Connection txn = db.startTransaction();
+		Settings s = db.getSettings(txn, DB_SETTINGS_NAMESPACE);
+		assertEquals(now, s.getLong(LAST_COMPACTED_KEY, 0));
+		db.commitTransaction(txn);
+		db.close();
+
+		// Time: now + MAX_COMPACTION_INTERVAL_MS
+		// The DB should not be compacted, so the last compaction time should
+		// not be updated
+		time.set(now + MAX_COMPACTION_INTERVAL_MS);
+		db = open(true, messageFactory, clock);
+		txn = db.startTransaction();
+		s = db.getSettings(txn, DB_SETTINGS_NAMESPACE);
+		assertEquals(now, s.getLong(LAST_COMPACTED_KEY, 0));
+		db.commitTransaction(txn);
+		db.close();
+
+		// Time: now + MAX_COMPACTION_INTERVAL_MS + 1
+		// The DB should be compacted, so the last compaction time should be
+		// updated
+		time.set(now + MAX_COMPACTION_INTERVAL_MS + 1);
+		db = open(true, messageFactory, clock);
+		txn = db.startTransaction();
+		s = db.getSettings(txn, DB_SETTINGS_NAMESPACE);
+		assertEquals(now + MAX_COMPACTION_INTERVAL_MS + 1,
+				s.getLong(LAST_COMPACTED_KEY, 0));
+		db.commitTransaction(txn);
+		db.close();
+	}
 
 	private Database<Connection> open(boolean resume) throws Exception {
 		return open(resume, new TestMessageFactory(), new SystemClock());
@@ -1921,7 +1999,7 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 		Database<Connection> db =
 				createDatabase(new TestDatabaseConfig(testDir, MAX_SIZE),
 						messageFactory, clock);
-		if (!resume) TestUtils.deleteTestDirectory(testDir);
+		if (!resume) deleteTestDirectory(testDir);
 		db.open(key, null);
 		return db;
 	}

bramble-core/src/test/java/org/briarproject/bramble/identity/IdentityManagerImplTest.java

@@ -1,7 +1,5 @@
 package org.briarproject.bramble.identity;
 
-import org.briarproject.bramble.api.contact.Contact;
-import org.briarproject.bramble.api.contact.ContactId;
 import org.briarproject.bramble.api.crypto.CryptoComponent;
 import org.briarproject.bramble.api.crypto.KeyPair;
 import org.briarproject.bramble.api.crypto.PrivateKey;
@@ -9,25 +7,18 @@ import org.briarproject.bramble.api.crypto.PublicKey;
 import org.briarproject.bramble.api.db.DatabaseComponent;
 import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.db.Transaction;
-import org.briarproject.bramble.api.identity.Author;
 import org.briarproject.bramble.api.identity.AuthorFactory;
-import org.briarproject.bramble.api.identity.AuthorId;
 import org.briarproject.bramble.api.identity.IdentityManager;
 import org.briarproject.bramble.api.identity.LocalAuthor;
 import org.briarproject.bramble.test.BrambleMockTestCase;
+import org.briarproject.bramble.test.DbExpectations;
 import org.jmock.Expectations;
 import org.junit.Before;
 import org.junit.Test;
 
-import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Collections;
 
-import static org.briarproject.bramble.api.identity.Author.Status.OURSELVES;
-import static org.briarproject.bramble.api.identity.Author.Status.UNKNOWN;
-import static org.briarproject.bramble.api.identity.Author.Status.UNVERIFIED;
-import static org.briarproject.bramble.api.identity.Author.Status.VERIFIED;
-import static org.briarproject.bramble.test.TestUtils.getAuthor;
 import static org.briarproject.bramble.test.TestUtils.getLocalAuthor;
 import static org.junit.Assert.assertEquals;
 
@@ -74,13 +65,10 @@ public class IdentityManagerImplTest extends BrambleMockTestCase {
 	}
 
 	@Test
-	public void testRegisterAndStoreLocalAuthor() throws DbException {
-		context.checking(new Expectations() {{
-			oneOf(db).startTransaction(false);
-			will(returnValue(txn));
+	public void testRegisterAndStoreLocalAuthor() throws Exception {
+		context.checking(new DbExpectations() {{
+			oneOf(db).transaction(with(false), withDbRunnable(txn));
 			oneOf(db).addLocalAuthor(txn, localAuthor);
-			oneOf(db).commitTransaction(txn);
-			oneOf(db).endTransaction(txn);
 		}});
 
 		identityManager.registerLocalAuthor(localAuthor);
@@ -89,14 +77,11 @@ public class IdentityManagerImplTest extends BrambleMockTestCase {
 	}
 
 	@Test
-	public void testGetLocalAuthor() throws DbException {
-		context.checking(new Expectations() {{
-			oneOf(db).startTransaction(true);
-			will(returnValue(txn));
+	public void testGetLocalAuthor() throws Exception {
+		context.checking(new DbExpectations() {{
+			oneOf(db).transactionWithResult(with(true), withDbCallable(txn));
 			oneOf(db).getLocalAuthors(txn);
 			will(returnValue(localAuthors));
-			oneOf(db).commitTransaction(txn);
-			oneOf(db).endTransaction(txn);
 		}});
 		assertEquals(localAuthor, identityManager.getLocalAuthor());
 	}
@@ -107,60 +92,4 @@ public class IdentityManagerImplTest extends BrambleMockTestCase {
 		assertEquals(localAuthor, identityManager.getLocalAuthor());
 	}
 
-	@Test
-	public void testGetAuthorStatus() throws DbException {
-		Author author = getAuthor();
-		AuthorId authorId = author.getId();
-		Collection<Contact> contacts = new ArrayList<>();
-
-		context.checking(new Expectations() {{
-			oneOf(db).startTransaction(true);
-			will(returnValue(txn));
-			oneOf(db).getLocalAuthors(txn);
-			will(returnValue(localAuthors));
-			oneOf(db).getContactsByAuthorId(txn, authorId);
-			will(returnValue(contacts));
-			oneOf(db).endTransaction(txn);
-		}});
-		assertEquals(UNKNOWN, identityManager.getAuthorStatus(authorId));
-
-		// add one unverified contact
-		Contact contact = new Contact(new ContactId(1), author,
-				localAuthor.getId(), false, true);
-		contacts.add(contact);
-
-		checkAuthorStatusContext(authorId, contacts);
-		assertEquals(UNVERIFIED, identityManager.getAuthorStatus(authorId));
-
-		// add one verified contact
-		Contact contact2 = new Contact(new ContactId(1), author,
-				localAuthor.getId(), true, true);
-		contacts.add(contact2);
-
-		checkAuthorStatusContext(authorId, contacts);
-		assertEquals(VERIFIED, identityManager.getAuthorStatus(authorId));
-
-		context.checking(new Expectations() {{
-			oneOf(db).startTransaction(true);
-			will(returnValue(txn));
-			never(db).getLocalAuthors(txn);
-			never(db).getContactsByAuthorId(txn, authorId);
-			oneOf(db).endTransaction(txn);
-		}});
-		assertEquals(OURSELVES,
-				identityManager.getAuthorStatus(localAuthor.getId()));
-	}
-
-	private void checkAuthorStatusContext(AuthorId authorId,
-			Collection<Contact> contacts) throws DbException {
-		context.checking(new Expectations() {{
-			oneOf(db).startTransaction(true);
-			will(returnValue(txn));
-			never(db).getLocalAuthors(txn);
-			oneOf(db).getContactsByAuthorId(txn, authorId);
-			will(returnValue(contacts));
-			oneOf(db).endTransaction(txn);
-		}});
-	}
-
 }

bramble-core/src/test/java/org/briarproject/bramble/properties/TransportPropertyManagerImplTest.java

@@ -21,16 +21,18 @@ import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.bramble.api.system.Clock;
 import org.briarproject.bramble.api.versioning.ClientVersioningManager;
 import org.briarproject.bramble.test.BrambleMockTestCase;
+import org.briarproject.bramble.test.DbExpectations;
 import org.jmock.Expectations;
 import org.junit.Test;
 
-import java.util.Arrays;
 import java.util.Collections;
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
 
+import static java.util.Arrays.asList;
 import static java.util.Collections.singletonList;
+import static java.util.Collections.singletonMap;
 import static org.briarproject.bramble.api.properties.TransportPropertyManager.CLIENT_ID;
 import static org.briarproject.bramble.api.properties.TransportPropertyManager.MAJOR_VERSION;
 import static org.briarproject.bramble.api.sync.Group.Visibility.SHARED;
@@ -39,6 +41,7 @@ import static org.briarproject.bramble.test.TestUtils.getGroup;
 import static org.briarproject.bramble.test.TestUtils.getLocalAuthor;
 import static org.briarproject.bramble.test.TestUtils.getMessage;
 import static org.briarproject.bramble.test.TestUtils.getRandomId;
+import static org.briarproject.bramble.util.StringUtils.getRandomString;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 
@@ -350,14 +353,11 @@ public class TransportPropertyManagerImplTest extends BrambleMockTestCase {
 				new BdfEntry("local", true)
 		));
 
-		context.checking(new Expectations() {{
-			oneOf(db).startTransaction(true);
-			will(returnValue(txn));
+		context.checking(new DbExpectations() {{
+			oneOf(db).transactionWithResult(with(true), withDbCallable(txn));
 			oneOf(clientHelper).getMessageMetadataAsDictionary(txn,
 					localGroup.getId());
 			will(returnValue(messageMetadata));
-			oneOf(db).commitTransaction(txn);
-			oneOf(db).endTransaction(txn);
 		}});
 
 		TransportPropertyManagerImpl t = createInstance();
@@ -385,9 +385,8 @@ public class TransportPropertyManagerImplTest extends BrambleMockTestCase {
 		));
 		BdfList fooUpdate = BdfList.of("foo", 1, fooPropertiesDict);
 
-		context.checking(new Expectations() {{
-			oneOf(db).startTransaction(true);
-			will(returnValue(txn));
+		context.checking(new DbExpectations() {{
+			oneOf(db).transactionWithResult(with(true), withDbCallable(txn));
 			oneOf(clientHelper).getMessageMetadataAsDictionary(txn,
 					localGroup.getId());
 			will(returnValue(messageMetadata));
@@ -396,8 +395,6 @@ public class TransportPropertyManagerImplTest extends BrambleMockTestCase {
 			oneOf(clientHelper).parseAndValidateTransportProperties(
 					fooPropertiesDict);
 			will(returnValue(fooProperties));
-			oneOf(db).commitTransaction(txn);
-			oneOf(db).endTransaction(txn);
 		}});
 
 		TransportPropertyManagerImpl t = createInstance();
@@ -412,8 +409,7 @@ public class TransportPropertyManagerImplTest extends BrambleMockTestCase {
 		Contact contact1 = getContact(false);
 		Contact contact2 = getContact(true);
 		Contact contact3 = getContact(true);
-		List<Contact> contacts =
-				Arrays.asList(contact1, contact2, contact3);
+		List<Contact> contacts = asList(contact1, contact2, contact3);
 		Group contactGroup2 = getGroup(CLIENT_ID, MAJOR_VERSION);
 		Group contactGroup3 = getGroup(CLIENT_ID, MAJOR_VERSION);
 		Map<MessageId, BdfDictionary> messageMetadata3 =
@@ -441,9 +437,8 @@ public class TransportPropertyManagerImplTest extends BrambleMockTestCase {
 		));
 		BdfList fooUpdate = BdfList.of("foo", 1, fooPropertiesDict);
 
-		context.checking(new Expectations() {{
-			oneOf(db).startTransaction(true);
-			will(returnValue(txn));
+		context.checking(new DbExpectations() {{
+			oneOf(db).transactionWithResult(with(true), withDbCallable(txn));
 			oneOf(db).getContacts(txn);
 			will(returnValue(contacts));
 			// First contact: skipped because not active
@@ -466,8 +461,6 @@ public class TransportPropertyManagerImplTest extends BrambleMockTestCase {
 			oneOf(clientHelper).parseAndValidateTransportProperties(
 					fooPropertiesDict);
 			will(returnValue(fooProperties));
-			oneOf(db).commitTransaction(txn);
-			oneOf(db).endTransaction(txn);
 		}});
 
 		TransportPropertyManagerImpl t = createInstance();
@@ -484,17 +477,16 @@ public class TransportPropertyManagerImplTest extends BrambleMockTestCase {
 			throws Exception {
 		Transaction txn = new Transaction(null, false);
 		MessageId updateId = new MessageId(getRandomId());
-		Map<MessageId, BdfDictionary> messageMetadata =
-				Collections.singletonMap(updateId, BdfDictionary.of(
+		Map<MessageId, BdfDictionary> messageMetadata = singletonMap(updateId,
+				BdfDictionary.of(
 						new BdfEntry("transportId", "foo"),
 						new BdfEntry("version", 1),
 						new BdfEntry("local", true)
 				));
 		BdfList update = BdfList.of("foo", 1, fooPropertiesDict);
 
-		context.checking(new Expectations() {{
-			oneOf(db).startTransaction(false);
-			will(returnValue(txn));
+		context.checking(new DbExpectations() {{
+			oneOf(db).transaction(with(false), withDbRunnable(txn));
 			// Merge the new properties with the existing properties
 			oneOf(clientHelper).getMessageMetadataAsDictionary(txn,
 					localGroup.getId());
@@ -505,8 +497,6 @@ public class TransportPropertyManagerImplTest extends BrambleMockTestCase {
 					fooPropertiesDict);
 			will(returnValue(fooProperties));
 			// Properties are unchanged so we're done
-			oneOf(db).commitTransaction(txn);
-			oneOf(db).endTransaction(txn);
 		}});
 
 		TransportPropertyManagerImpl t = createInstance();
@@ -519,9 +509,8 @@ public class TransportPropertyManagerImplTest extends BrambleMockTestCase {
 		Contact contact = getContact(true);
 		Group contactGroup = getGroup(CLIENT_ID, MAJOR_VERSION);
 
-		context.checking(new Expectations() {{
-			oneOf(db).startTransaction(false);
-			will(returnValue(txn));
+		context.checking(new DbExpectations() {{
+			oneOf(db).transaction(with(false), withDbRunnable(txn));
 			// There are no existing properties to merge with
 			oneOf(clientHelper).getMessageMetadataAsDictionary(txn,
 					localGroup.getId());
@@ -540,8 +529,6 @@ public class TransportPropertyManagerImplTest extends BrambleMockTestCase {
 			will(returnValue(Collections.emptyMap()));
 			expectStoreMessage(txn, contactGroup.getId(), "foo",
 					fooPropertiesDict, 1, true, true);
-			oneOf(db).commitTransaction(txn);
-			oneOf(db).endTransaction(txn);
 		}});
 
 		TransportPropertyManagerImpl t = createInstance();
@@ -560,10 +547,10 @@ public class TransportPropertyManagerImplTest extends BrambleMockTestCase {
 		);
 		MessageId localGroupUpdateId = new MessageId(getRandomId());
 		Map<MessageId, BdfDictionary> localGroupMessageMetadata =
-				Collections.singletonMap(localGroupUpdateId, oldMetadata);
+				singletonMap(localGroupUpdateId, oldMetadata);
 		MessageId contactGroupUpdateId = new MessageId(getRandomId());
 		Map<MessageId, BdfDictionary> contactGroupMessageMetadata =
-				Collections.singletonMap(contactGroupUpdateId, oldMetadata);
+				singletonMap(contactGroupUpdateId, oldMetadata);
 		TransportProperties oldProperties = new TransportProperties();
 		oldProperties.put("fooKey1", "oldFooValue1");
 		BdfDictionary oldPropertiesDict = BdfDictionary.of(
@@ -571,9 +558,8 @@ public class TransportPropertyManagerImplTest extends BrambleMockTestCase {
 		);
 		BdfList oldUpdate = BdfList.of("foo", 1, oldPropertiesDict);
 
-		context.checking(new Expectations() {{
-			oneOf(db).startTransaction(false);
-			will(returnValue(txn));
+		context.checking(new DbExpectations() {{
+			oneOf(db).transaction(with(false), withDbRunnable(txn));
 			// Merge the new properties with the existing properties
 			oneOf(clientHelper).getMessageMetadataAsDictionary(txn,
 					localGroup.getId());
@@ -601,8 +587,6 @@ public class TransportPropertyManagerImplTest extends BrambleMockTestCase {
 					fooPropertiesDict, 2, true, true);
 			// Delete the previous update
 			oneOf(db).removeMessage(txn, contactGroupUpdateId);
-			oneOf(db).commitTransaction(txn);
-			oneOf(db).endTransaction(txn);
 		}});
 
 		TransportPropertyManagerImpl t = createInstance();
@@ -612,7 +596,7 @@ public class TransportPropertyManagerImplTest extends BrambleMockTestCase {
 	private Contact getContact(boolean active) {
 		ContactId c = new ContactId(nextContactId++);
 		return new Contact(c, getAuthor(), localAuthor.getId(),
-				true, active);
+				getRandomString(5), true, active);
 	}
 
 	private void expectGetLocalProperties(Transaction txn) throws Exception {

bramble-core/src/test/java/org/briarproject/bramble/sync/SimplexOutgoingSessionTest.java

@@ -11,8 +11,8 @@ import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.bramble.api.sync.SyncRecordWriter;
 import org.briarproject.bramble.api.transport.StreamWriter;
 import org.briarproject.bramble.test.BrambleMockTestCase;
+import org.briarproject.bramble.test.DbExpectations;
 import org.briarproject.bramble.test.ImmediateExecutor;
-import org.jmock.Expectations;
 import org.junit.Test;
 
 import java.util.concurrent.Executor;
@@ -45,24 +45,20 @@ public class SimplexOutgoingSessionTest extends BrambleMockTestCase {
 		Transaction noAckTxn = new Transaction(null, false);
 		Transaction noMsgTxn = new Transaction(null, false);
 
-		context.checking(new Expectations() {{
+		context.checking(new DbExpectations() {{
 			// Add listener
 			oneOf(eventBus).addListener(session);
 			// No acks to send
-			oneOf(db).startTransaction(false);
-			will(returnValue(noAckTxn));
+			oneOf(db).transactionWithNullableResult(with(false),
+					withNullableDbCallable(noAckTxn));
 			oneOf(db).generateAck(noAckTxn, contactId, MAX_MESSAGE_IDS);
 			will(returnValue(null));
-			oneOf(db).commitTransaction(noAckTxn);
-			oneOf(db).endTransaction(noAckTxn);
 			// No messages to send
-			oneOf(db).startTransaction(false);
-			will(returnValue(noMsgTxn));
+			oneOf(db).transactionWithNullableResult(with(false),
+					withNullableDbCallable(noMsgTxn));
 			oneOf(db).generateBatch(with(noMsgTxn), with(contactId),
 					with(any(int.class)), with(MAX_LATENCY));
 			will(returnValue(null));
-			oneOf(db).commitTransaction(noMsgTxn);
-			oneOf(db).endTransaction(noMsgTxn);
 			// Send the end of stream marker
 			oneOf(streamWriter).sendEndOfStream();
 			// Remove listener
@@ -83,41 +79,33 @@ public class SimplexOutgoingSessionTest extends BrambleMockTestCase {
 		Transaction msgTxn = new Transaction(null, false);
 		Transaction noMsgTxn = new Transaction(null, false);
 
-		context.checking(new Expectations() {{
+		context.checking(new DbExpectations() {{
 			// Add listener
 			oneOf(eventBus).addListener(session);
 			// One ack to send
-			oneOf(db).startTransaction(false);
-			will(returnValue(ackTxn));
+			oneOf(db).transactionWithNullableResult(with(false),
+					withNullableDbCallable(ackTxn));
 			oneOf(db).generateAck(ackTxn, contactId, MAX_MESSAGE_IDS);
 			will(returnValue(ack));
-			oneOf(db).commitTransaction(ackTxn);
-			oneOf(db).endTransaction(ackTxn);
 			oneOf(recordWriter).writeAck(ack);
 			// One message to send
-			oneOf(db).startTransaction(false);
-			will(returnValue(msgTxn));
+			oneOf(db).transactionWithNullableResult(with(false),
+					withNullableDbCallable(msgTxn));
 			oneOf(db).generateBatch(with(msgTxn), with(contactId),
 					with(any(int.class)), with(MAX_LATENCY));
 			will(returnValue(singletonList(message)));
-			oneOf(db).commitTransaction(msgTxn);
-			oneOf(db).endTransaction(msgTxn);
 			oneOf(recordWriter).writeMessage(message);
 			// No more acks
-			oneOf(db).startTransaction(false);
-			will(returnValue(noAckTxn));
+			oneOf(db).transactionWithNullableResult(with(false),
+					withNullableDbCallable(noAckTxn));
 			oneOf(db).generateAck(noAckTxn, contactId, MAX_MESSAGE_IDS);
 			will(returnValue(null));
-			oneOf(db).commitTransaction(noAckTxn);
-			oneOf(db).endTransaction(noAckTxn);
 			// No more messages
-			oneOf(db).startTransaction(false);
-			will(returnValue(noMsgTxn));
+			oneOf(db).transactionWithNullableResult(with(false),
+					withNullableDbCallable(noMsgTxn));
 			oneOf(db).generateBatch(with(noMsgTxn), with(contactId),
 					with(any(int.class)), with(MAX_LATENCY));
 			will(returnValue(null));
-			oneOf(db).commitTransaction(noMsgTxn);
-			oneOf(db).endTransaction(noMsgTxn);
 			// Send the end of stream marker
 			oneOf(streamWriter).sendEndOfStream();
 			// Remove listener

bramble-core/src/test/java/org/briarproject/bramble/sync/ValidationManagerImplTest.java

@@ -18,16 +18,16 @@ import org.briarproject.bramble.api.sync.ValidationManager.MessageValidator;
 import org.briarproject.bramble.api.sync.ValidationManager.State;
 import org.briarproject.bramble.api.sync.event.MessageAddedEvent;
 import org.briarproject.bramble.test.BrambleMockTestCase;
+import org.briarproject.bramble.test.DbExpectations;
 import org.briarproject.bramble.test.ImmediateExecutor;
-import org.jmock.Expectations;
 import org.junit.Before;
 import org.junit.Test;
 
-import java.util.Arrays;
 import java.util.LinkedHashMap;
 import java.util.Map;
 import java.util.concurrent.Executor;
 
+import static java.util.Arrays.asList;
 import static java.util.Collections.emptyList;
 import static java.util.Collections.emptyMap;
 import static java.util.Collections.singletonList;
@@ -83,28 +83,19 @@ public class ValidationManagerImplTest extends BrambleMockTestCase {
 		Transaction txn1 = new Transaction(null, true);
 		Transaction txn2 = new Transaction(null, true);
 
-		context.checking(new Expectations() {{
+		context.checking(new DbExpectations() {{
 			// validateOutstandingMessages()
-			oneOf(db).startTransaction(true);
-			will(returnValue(txn));
+			oneOf(db).transactionWithResult(with(true), withDbCallable(txn));
 			oneOf(db).getMessagesToValidate(txn);
 			will(returnValue(emptyList()));
-			oneOf(db).commitTransaction(txn);
-			oneOf(db).endTransaction(txn);
 			// deliverOutstandingMessages()
-			oneOf(db).startTransaction(true);
-			will(returnValue(txn1));
+			oneOf(db).transactionWithResult(with(true), withDbCallable(txn1));
 			oneOf(db).getPendingMessages(txn1);
 			will(returnValue(emptyList()));
-			oneOf(db).commitTransaction(txn1);
-			oneOf(db).endTransaction(txn1);
 			// shareOutstandingMessages()
-			oneOf(db).startTransaction(true);
-			will(returnValue(txn2));
+			oneOf(db).transactionWithResult(with(true), withDbCallable(txn2));
 			oneOf(db).getMessagesToShare(txn2);
 			will(returnValue(emptyList()));
-			oneOf(db).commitTransaction(txn2);
-			oneOf(db).endTransaction(txn2);
 		}});
 
 		vm.startService();
@@ -121,29 +112,22 @@ public class ValidationManagerImplTest extends BrambleMockTestCase {
 		Transaction txn5 = new Transaction(null, true);
 		Transaction txn6 = new Transaction(null, true);
 
-		context.checking(new Expectations() {{
+		context.checking(new DbExpectations() {{
 			// Get messages to validate
-			oneOf(db).startTransaction(true);
-			will(returnValue(txn));
+			oneOf(db).transactionWithResult(with(true), withDbCallable(txn));
 			oneOf(db).getMessagesToValidate(txn);
-			will(returnValue(Arrays.asList(messageId, messageId1)));
-			oneOf(db).commitTransaction(txn);
-			oneOf(db).endTransaction(txn);
+			will(returnValue(asList(messageId, messageId1)));
 			// Load the first raw message and group
-			oneOf(db).startTransaction(true);
-			will(returnValue(txn1));
+			oneOf(db).transactionWithResult(with(true), withDbCallable(txn1));
 			oneOf(db).getMessage(txn1, messageId);
 			will(returnValue(message));
 			oneOf(db).getGroup(txn1, groupId);
 			will(returnValue(group));
-			oneOf(db).commitTransaction(txn1);
-			oneOf(db).endTransaction(txn1);
 			// Validate the first message: valid
 			oneOf(validator).validateMessage(message, group);
 			will(returnValue(validResult));
 			// Store the validation result for the first message
-			oneOf(db).startTransaction(false);
-			will(returnValue(txn2));
+			oneOf(db).transaction(with(false), withDbRunnable(txn2));
 			oneOf(db).mergeMessageMetadata(txn2, messageId, metadata);
 			// Deliver the first message
 			oneOf(hook).incomingMessage(txn2, message, metadata);
@@ -152,23 +136,17 @@ public class ValidationManagerImplTest extends BrambleMockTestCase {
 			// Get any pending dependents
 			oneOf(db).getMessageDependents(txn2, messageId);
 			will(returnValue(emptyMap()));
-			oneOf(db).commitTransaction(txn2);
-			oneOf(db).endTransaction(txn2);
 			// Load the second raw message and group
-			oneOf(db).startTransaction(true);
-			will(returnValue(txn3));
+			oneOf(db).transactionWithResult(with(true), withDbCallable(txn3));
 			oneOf(db).getMessage(txn3, messageId1);
 			will(returnValue(message1));
 			oneOf(db).getGroup(txn3, groupId);
 			will(returnValue(group));
-			oneOf(db).commitTransaction(txn3);
-			oneOf(db).endTransaction(txn3);
 			// Validate the second message: invalid
 			oneOf(validator).validateMessage(message1, group);
 			will(throwException(new InvalidMessageException()));
 			// Store the validation result for the second message
-			oneOf(db).startTransaction(false);
-			will(returnValue(txn4));
+			oneOf(db).transaction(with(false), withDbRunnable(txn4));
 			oneOf(db).getMessageState(txn4, messageId1);
 			will(returnValue(UNKNOWN));
 			oneOf(db).setMessageState(txn4, messageId1, INVALID);
@@ -177,22 +155,14 @@ public class ValidationManagerImplTest extends BrambleMockTestCase {
 			// Recursively invalidate any dependents
 			oneOf(db).getMessageDependents(txn4, messageId1);
 			will(returnValue(emptyMap()));
-			oneOf(db).commitTransaction(txn4);
-			oneOf(db).endTransaction(txn4);
 			// Get pending messages to deliver
-			oneOf(db).startTransaction(true);
-			will(returnValue(txn5));
+			oneOf(db).transactionWithResult(with(true), withDbCallable(txn5));
 			oneOf(db).getPendingMessages(txn5);
 			will(returnValue(emptyList()));
-			oneOf(db).commitTransaction(txn5);
-			oneOf(db).endTransaction(txn5);
 			// Get messages to share
-			oneOf(db).startTransaction(true);
-			will(returnValue(txn6));
+			oneOf(db).transactionWithResult(with(true), withDbCallable(txn6));
 			oneOf(db).getMessagesToShare(txn6);
 			will(returnValue(emptyList()));
-			oneOf(db).commitTransaction(txn6);
-			oneOf(db).endTransaction(txn6);
 		}});
 
 		vm.startService();
@@ -206,24 +176,17 @@ public class ValidationManagerImplTest extends BrambleMockTestCase {
 		Transaction txn3 = new Transaction(null, false);
 		Transaction txn4 = new Transaction(null, true);
 
-		context.checking(new Expectations() {{
+		context.checking(new DbExpectations() {{
 			// Get messages to validate
-			oneOf(db).startTransaction(true);
-			will(returnValue(txn));
+			oneOf(db).transactionWithResult(with(true), withDbCallable(txn));
 			oneOf(db).getMessagesToValidate(txn);
 			will(returnValue(emptyList()));
-			oneOf(db).commitTransaction(txn);
-			oneOf(db).endTransaction(txn);
 			// Get pending messages to deliver
-			oneOf(db).startTransaction(true);
-			will(returnValue(txn1));
+			oneOf(db).transactionWithResult(with(true), withDbCallable(txn1));
 			oneOf(db).getPendingMessages(txn1);
 			will(returnValue(singletonList(messageId)));
-			oneOf(db).commitTransaction(txn1);
-			oneOf(db).endTransaction(txn1);
 			// Check whether the message is ready to deliver
-			oneOf(db).startTransaction(false);
-			will(returnValue(txn2));
+			oneOf(db).transaction(with(false), withDbRunnable(txn2));
 			oneOf(db).getMessageState(txn2, messageId);
 			will(returnValue(PENDING));
 			oneOf(db).getMessageDependencies(txn2, messageId);
@@ -242,11 +205,8 @@ public class ValidationManagerImplTest extends BrambleMockTestCase {
 			// Get any pending dependents
 			oneOf(db).getMessageDependents(txn2, messageId);
 			will(returnValue(singletonMap(messageId2, PENDING)));
-			oneOf(db).commitTransaction(txn2);
-			oneOf(db).endTransaction(txn2);
 			// Check whether the dependent is ready to deliver
-			oneOf(db).startTransaction(false);
-			will(returnValue(txn3));
+			oneOf(db).transaction(with(false), withDbRunnable(txn3));
 			oneOf(db).getMessageState(txn3, messageId2);
 			will(returnValue(PENDING));
 			oneOf(db).getMessageDependencies(txn3, messageId2);
@@ -265,16 +225,11 @@ public class ValidationManagerImplTest extends BrambleMockTestCase {
 			// Get any pending dependents
 			oneOf(db).getMessageDependents(txn3, messageId2);
 			will(returnValue(emptyMap()));
-			oneOf(db).commitTransaction(txn3);
-			oneOf(db).endTransaction(txn3);
 
 			// Get messages to share
-			oneOf(db).startTransaction(true);
-			will(returnValue(txn4));
+			oneOf(db).transactionWithResult(with(true), withDbCallable(txn4));
 			oneOf(db).getMessagesToShare(txn4);
 			will(returnValue(emptyList()));
-			oneOf(db).commitTransaction(txn4);
-			oneOf(db).endTransaction(txn4);
 		}});
 
 		vm.startService();
@@ -288,45 +243,30 @@ public class ValidationManagerImplTest extends BrambleMockTestCase {
 		Transaction txn3 = new Transaction(null, false);
 		Transaction txn4 = new Transaction(null, false);
 
-		context.checking(new Expectations() {{
+		context.checking(new DbExpectations() {{
 			// No messages to validate
-			oneOf(db).startTransaction(true);
-			will(returnValue(txn));
+			oneOf(db).transactionWithResult(with(true), withDbCallable(txn));
 			oneOf(db).getMessagesToValidate(txn);
 			will(returnValue(emptyList()));
-			oneOf(db).commitTransaction(txn);
-			oneOf(db).endTransaction(txn);
 			// No pending messages to deliver
-			oneOf(db).startTransaction(true);
-			will(returnValue(txn1));
+			oneOf(db).transactionWithResult(with(true), withDbCallable(txn1));
 			oneOf(db).getPendingMessages(txn1);
 			will(returnValue(emptyList()));
-			oneOf(db).commitTransaction(txn1);
-			oneOf(db).endTransaction(txn1);
 
 			// Get messages to share
-			oneOf(db).startTransaction(true);
-			will(returnValue(txn2));
+			oneOf(db).transactionWithResult(with(true), withDbCallable(txn2));
 			oneOf(db).getMessagesToShare(txn2);
 			will(returnValue(singletonList(messageId)));
-			oneOf(db).commitTransaction(txn2);
-			oneOf(db).endTransaction(txn2);
 			// Share message and get dependencies
-			oneOf(db).startTransaction(false);
-			will(returnValue(txn3));
+			oneOf(db).transaction(with(false), withDbRunnable(txn3));
 			oneOf(db).setMessageShared(txn3, messageId);
 			oneOf(db).getMessageDependencies(txn3, messageId);
 			will(returnValue(singletonMap(messageId2, DELIVERED)));
-			oneOf(db).commitTransaction(txn3);
-			oneOf(db).endTransaction(txn3);
 			// Share dependency
-			oneOf(db).startTransaction(false);
-			will(returnValue(txn4));
+			oneOf(db).transaction(with(false), withDbRunnable(txn4));
 			oneOf(db).setMessageShared(txn4, messageId2);
 			oneOf(db).getMessageDependencies(txn4, messageId2);
 			will(returnValue(emptyMap()));
-			oneOf(db).commitTransaction(txn4);
-			oneOf(db).endTransaction(txn4);
 		}});
 
 		vm.startService();
@@ -338,20 +278,16 @@ public class ValidationManagerImplTest extends BrambleMockTestCase {
 		Transaction txn1 = new Transaction(null, false);
 		Transaction txn2 = new Transaction(null, false);
 
-		context.checking(new Expectations() {{
+		context.checking(new DbExpectations() {{
 			// Load the group
-			oneOf(db).startTransaction(true);
-			will(returnValue(txn));
+			oneOf(db).transactionWithResult(with(true), withDbCallable(txn));
 			oneOf(db).getGroup(txn, groupId);
 			will(returnValue(group));
-			oneOf(db).commitTransaction(txn);
-			oneOf(db).endTransaction(txn);
 			// Validate the message: valid
 			oneOf(validator).validateMessage(message, group);
 			will(returnValue(validResultWithDependencies));
 			// Store the validation result
-			oneOf(db).startTransaction(false);
-			will(returnValue(txn1));
+			oneOf(db).transaction(with(false), withDbRunnable(txn1));
 			oneOf(db).addMessageDependencies(txn1, message,
 					validResultWithDependencies.getDependencies());
 			oneOf(db).getMessageDependencies(txn1, messageId);
@@ -366,16 +302,11 @@ public class ValidationManagerImplTest extends BrambleMockTestCase {
 			will(returnValue(emptyMap()));
 			// Share message
 			oneOf(db).setMessageShared(txn1, messageId);
-			oneOf(db).commitTransaction(txn1);
-			oneOf(db).endTransaction(txn1);
 			// Share dependencies
-			oneOf(db).startTransaction(false);
-			will(returnValue(txn2));
+			oneOf(db).transaction(with(false), withDbRunnable(txn2));
 			oneOf(db).setMessageShared(txn2, messageId1);
 			oneOf(db).getMessageDependencies(txn2, messageId1);
 			will(returnValue(emptyMap()));
-			oneOf(db).commitTransaction(txn2);
-			oneOf(db).endTransaction(txn2);
 		}});
 
 		vm.eventOccurred(new MessageAddedEvent(message, contactId));
@@ -391,36 +322,26 @@ public class ValidationManagerImplTest extends BrambleMockTestCase {
 		Transaction txn4 = new Transaction(null, true);
 		Transaction txn5 = new Transaction(null, true);
 
-		context.checking(new Expectations() {{
+		context.checking(new DbExpectations() {{
 			// Get messages to validate
-			oneOf(db).startTransaction(true);
-			will(returnValue(txn));
+			oneOf(db).transactionWithResult(with(true), withDbCallable(txn));
 			oneOf(db).getMessagesToValidate(txn);
-			will(returnValue(Arrays.asList(messageId, messageId1)));
-			oneOf(db).commitTransaction(txn);
-			oneOf(db).endTransaction(txn);
+			will(returnValue(asList(messageId, messageId1)));
 			// Load the first raw message - *gasp* it's gone!
-			oneOf(db).startTransaction(true);
-			will(returnValue(txn1));
+			oneOf(db).transactionWithResult(with(true), withDbCallable(txn1));
 			oneOf(db).getMessage(txn1, messageId);
 			will(throwException(new NoSuchMessageException()));
-			never(db).commitTransaction(txn1);
-			oneOf(db).endTransaction(txn1);
 			// Load the second raw message and group
-			oneOf(db).startTransaction(true);
-			will(returnValue(txn2));
+			oneOf(db).transactionWithResult(with(true), withDbCallable(txn2));
 			oneOf(db).getMessage(txn2, messageId1);
 			will(returnValue(message1));
 			oneOf(db).getGroup(txn2, groupId);
 			will(returnValue(group));
-			oneOf(db).commitTransaction(txn2);
-			oneOf(db).endTransaction(txn2);
 			// Validate the second message: invalid
 			oneOf(validator).validateMessage(message1, group);
 			will(throwException(new InvalidMessageException()));
 			// Invalidate the second message
-			oneOf(db).startTransaction(false);
-			will(returnValue(txn3));
+			oneOf(db).transaction(with(false), withDbRunnable(txn3));
 			oneOf(db).getMessageState(txn3, messageId1);
 			will(returnValue(UNKNOWN));
 			oneOf(db).setMessageState(txn3, messageId1, INVALID);
@@ -429,22 +350,14 @@ public class ValidationManagerImplTest extends BrambleMockTestCase {
 			// Recursively invalidate dependents
 			oneOf(db).getMessageDependents(txn3, messageId1);
 			will(returnValue(emptyMap()));
-			oneOf(db).commitTransaction(txn3);
-			oneOf(db).endTransaction(txn3);
 			// Get pending messages to deliver
-			oneOf(db).startTransaction(true);
-			will(returnValue(txn4));
+			oneOf(db).transactionWithResult(with(true), withDbCallable(txn4));
 			oneOf(db).getPendingMessages(txn4);
 			will(returnValue(emptyList()));
-			oneOf(db).commitTransaction(txn4);
-			oneOf(db).endTransaction(txn4);
 			// Get messages to share
-			oneOf(db).startTransaction(true);
-			will(returnValue(txn5));
+			oneOf(db).transactionWithResult(with(true), withDbCallable(txn5));
 			oneOf(db).getMessagesToShare(txn5);
 			will(returnValue(emptyList()));
-			oneOf(db).commitTransaction(txn5);
-			oneOf(db).endTransaction(txn5);
 		}});
 
 		vm.startService();
@@ -460,39 +373,29 @@ public class ValidationManagerImplTest extends BrambleMockTestCase {
 		Transaction txn4 = new Transaction(null, true);
 		Transaction txn5 = new Transaction(null, true);
 
-		context.checking(new Expectations() {{
+		context.checking(new DbExpectations() {{
 			// Get messages to validate
-			oneOf(db).startTransaction(true);
-			will(returnValue(txn));
+			oneOf(db).transactionWithResult(with(true), withDbCallable(txn));
 			oneOf(db).getMessagesToValidate(txn);
-			will(returnValue(Arrays.asList(messageId, messageId1)));
-			oneOf(db).commitTransaction(txn);
-			oneOf(db).endTransaction(txn);
+			will(returnValue(asList(messageId, messageId1)));
 			// Load the first raw message
-			oneOf(db).startTransaction(true);
-			will(returnValue(txn1));
+			oneOf(db).transactionWithResult(with(true), withDbCallable(txn1));
 			oneOf(db).getMessage(txn1, messageId);
 			will(returnValue(message));
 			// Load the group - *gasp* it's gone!
 			oneOf(db).getGroup(txn1, groupId);
 			will(throwException(new NoSuchGroupException()));
-			never(db).commitTransaction(txn1);
-			oneOf(db).endTransaction(txn1);
 			// Load the second raw message and group
-			oneOf(db).startTransaction(true);
-			will(returnValue(txn2));
+			oneOf(db).transactionWithResult(with(true), withDbCallable(txn2));
 			oneOf(db).getMessage(txn2, messageId1);
 			will(returnValue(message1));
 			oneOf(db).getGroup(txn2, groupId);
 			will(returnValue(group));
-			oneOf(db).commitTransaction(txn2);
-			oneOf(db).endTransaction(txn2);
 			// Validate the second message: invalid
 			oneOf(validator).validateMessage(message1, group);
 			will(throwException(new InvalidMessageException()));
 			// Store the validation result for the second message
-			oneOf(db).startTransaction(false);
-			will(returnValue(txn3));
+			oneOf(db).transaction(with(false), withDbRunnable(txn3));
 			oneOf(db).getMessageState(txn3, messageId1);
 			will(returnValue(UNKNOWN));
 			oneOf(db).setMessageState(txn3, messageId1, INVALID);
@@ -501,22 +404,14 @@ public class ValidationManagerImplTest extends BrambleMockTestCase {
 			// Recursively invalidate dependents
 			oneOf(db).getMessageDependents(txn3, messageId1);
 			will(returnValue(emptyMap()));
-			oneOf(db).commitTransaction(txn3);
-			oneOf(db).endTransaction(txn3);
 			// Get pending messages to deliver
-			oneOf(db).startTransaction(true);
-			will(returnValue(txn4));
+			oneOf(db).transactionWithResult(with(true), withDbCallable(txn4));
 			oneOf(db).getPendingMessages(txn4);
 			will(returnValue(emptyList()));
-			oneOf(db).commitTransaction(txn4);
-			oneOf(db).endTransaction(txn4);
 			// Get messages to share
-			oneOf(db).startTransaction(true);
-			will(returnValue(txn5));
+			oneOf(db).transactionWithResult(with(true), withDbCallable(txn5));
 			oneOf(db).getMessagesToShare(txn5);
 			will(returnValue(emptyList()));
-			oneOf(db).commitTransaction(txn5);
-			oneOf(db).endTransaction(txn5);
 		}});
 
 		vm.startService();
@@ -527,20 +422,16 @@ public class ValidationManagerImplTest extends BrambleMockTestCase {
 		Transaction txn = new Transaction(null, true);
 		Transaction txn1 = new Transaction(null, false);
 
-		context.checking(new Expectations() {{
+		context.checking(new DbExpectations() {{
 			// Load the group
-			oneOf(db).startTransaction(true);
-			will(returnValue(txn));
+			oneOf(db).transactionWithResult(with(true), withDbCallable(txn));
 			oneOf(db).getGroup(txn, groupId);
 			will(returnValue(group));
-			oneOf(db).commitTransaction(txn);
-			oneOf(db).endTransaction(txn);
 			// Validate the message: valid
 			oneOf(validator).validateMessage(message, group);
 			will(returnValue(validResult));
 			// Store the validation result
-			oneOf(db).startTransaction(false);
-			will(returnValue(txn1));
+			oneOf(db).transaction(with(false), withDbRunnable(txn1));
 			oneOf(db).mergeMessageMetadata(txn1, messageId, metadata);
 			// Deliver the message
 			oneOf(hook).incomingMessage(txn1, message, metadata);
@@ -549,8 +440,6 @@ public class ValidationManagerImplTest extends BrambleMockTestCase {
 			// Get any pending dependents
 			oneOf(db).getMessageDependents(txn1, messageId);
 			will(returnValue(emptyMap()));
-			oneOf(db).commitTransaction(txn1);
-			oneOf(db).endTransaction(txn1);
 		}});
 
 		vm.eventOccurred(new MessageAddedEvent(message, contactId));
@@ -567,28 +456,22 @@ public class ValidationManagerImplTest extends BrambleMockTestCase {
 		Transaction txn = new Transaction(null, true);
 		Transaction txn1 = new Transaction(null, false);
 
-		context.checking(new Expectations() {{
+		context.checking(new DbExpectations() {{
 			// Load the group
-			oneOf(db).startTransaction(true);
-			will(returnValue(txn));
+			oneOf(db).transactionWithResult(with(true), withDbCallable(txn));
 			oneOf(db).getGroup(txn, groupId);
 			will(returnValue(group));
-			oneOf(db).commitTransaction(txn);
-			oneOf(db).endTransaction(txn);
 			// Validate the message: valid
 			oneOf(validator).validateMessage(message, group);
 			will(returnValue(validResultWithDependencies));
 			// Store the validation result
-			oneOf(db).startTransaction(false);
-			will(returnValue(txn1));
+			oneOf(db).transaction(with(false), withDbRunnable(txn1));
 			oneOf(db).addMessageDependencies(txn1, message,
 					validResultWithDependencies.getDependencies());
 			oneOf(db).getMessageDependencies(txn1, messageId);
 			will(returnValue(singletonMap(messageId1, UNKNOWN)));
 			oneOf(db).mergeMessageMetadata(txn1, messageId, metadata);
 			oneOf(db).setMessageState(txn1, messageId, PENDING);
-			oneOf(db).commitTransaction(txn1);
-			oneOf(db).endTransaction(txn1);
 		}});
 
 		vm.eventOccurred(new MessageAddedEvent(message, contactId));
@@ -600,20 +483,16 @@ public class ValidationManagerImplTest extends BrambleMockTestCase {
 		Transaction txn = new Transaction(null, true);
 		Transaction txn1 = new Transaction(null, false);
 
-		context.checking(new Expectations() {{
+		context.checking(new DbExpectations() {{
 			// Load the group
-			oneOf(db).startTransaction(true);
-			will(returnValue(txn));
+			oneOf(db).transactionWithResult(with(true), withDbCallable(txn));
 			oneOf(db).getGroup(txn, groupId);
 			will(returnValue(group));
-			oneOf(db).commitTransaction(txn);
-			oneOf(db).endTransaction(txn);
 			// Validate the message: valid
 			oneOf(validator).validateMessage(message, group);
 			will(returnValue(validResultWithDependencies));
 			// Store the validation result
-			oneOf(db).startTransaction(false);
-			will(returnValue(txn1));
+			oneOf(db).transaction(with(false), withDbRunnable(txn1));
 			oneOf(db).addMessageDependencies(txn1, message,
 					validResultWithDependencies.getDependencies());
 			oneOf(db).getMessageDependencies(txn1, messageId);
@@ -626,8 +505,6 @@ public class ValidationManagerImplTest extends BrambleMockTestCase {
 			// Get any pending dependents
 			oneOf(db).getMessageDependents(txn1, messageId);
 			will(returnValue(emptyMap()));
-			oneOf(db).commitTransaction(txn1);
-			oneOf(db).endTransaction(txn1);
 		}});
 
 		vm.eventOccurred(new MessageAddedEvent(message, contactId));
@@ -640,20 +517,16 @@ public class ValidationManagerImplTest extends BrambleMockTestCase {
 		Transaction txn1 = new Transaction(null, false);
 		Transaction txn2 = new Transaction(null, false);
 
-		context.checking(new Expectations() {{
+		context.checking(new DbExpectations() {{
 			// Load the group
-			oneOf(db).startTransaction(true);
-			will(returnValue(txn));
+			oneOf(db).transactionWithResult(with(true), withDbCallable(txn));
 			oneOf(db).getGroup(txn, groupId);
 			will(returnValue(group));
-			oneOf(db).commitTransaction(txn);
-			oneOf(db).endTransaction(txn);
 			// Validate the message: valid
 			oneOf(validator).validateMessage(message, group);
 			will(returnValue(validResultWithDependencies));
 			// Store the validation result
-			oneOf(db).startTransaction(false);
-			will(returnValue(txn1));
+			oneOf(db).transaction(with(false), withDbRunnable(txn1));
 			oneOf(db).addMessageDependencies(txn1, message,
 					validResultWithDependencies.getDependencies());
 			// Check for invalid dependencies
@@ -668,11 +541,8 @@ public class ValidationManagerImplTest extends BrambleMockTestCase {
 			// Recursively invalidate dependents
 			oneOf(db).getMessageDependents(txn1, messageId);
 			will(returnValue(singletonMap(messageId2, UNKNOWN)));
-			oneOf(db).commitTransaction(txn1);
-			oneOf(db).endTransaction(txn1);
 			// Invalidate dependent in a new transaction
-			oneOf(db).startTransaction(false);
-			will(returnValue(txn2));
+			oneOf(db).transaction(with(false), withDbRunnable(txn2));
 			oneOf(db).getMessageState(txn2, messageId2);
 			will(returnValue(UNKNOWN));
 			oneOf(db).setMessageState(txn2, messageId2, INVALID);
@@ -680,8 +550,6 @@ public class ValidationManagerImplTest extends BrambleMockTestCase {
 			oneOf(db).deleteMessageMetadata(txn2, messageId2);
 			oneOf(db).getMessageDependents(txn2, messageId2);
 			will(returnValue(emptyMap()));
-			oneOf(db).commitTransaction(txn2);
-			oneOf(db).endTransaction(txn2);
 		}});
 
 		vm.eventOccurred(new MessageAddedEvent(message, contactId));
@@ -702,20 +570,16 @@ public class ValidationManagerImplTest extends BrambleMockTestCase {
 		Transaction txn5 = new Transaction(null, false);
 		Transaction txn6 = new Transaction(null, false);
 
-		context.checking(new Expectations() {{
+		context.checking(new DbExpectations() {{
 			// Load the group
-			oneOf(db).startTransaction(true);
-			will(returnValue(txn));
+			oneOf(db).transactionWithResult(with(true), withDbCallable(txn));
 			oneOf(db).getGroup(txn, groupId);
 			will(returnValue(group));
-			oneOf(db).commitTransaction(txn);
-			oneOf(db).endTransaction(txn);
 			// Validate the message: invalid
 			oneOf(validator).validateMessage(message, group);
 			will(throwException(new InvalidMessageException()));
 			// Invalidate the message
-			oneOf(db).startTransaction(false);
-			will(returnValue(txn1));
+			oneOf(db).transaction(with(false), withDbRunnable(txn1));
 			oneOf(db).getMessageState(txn1, messageId);
 			will(returnValue(UNKNOWN));
 			oneOf(db).setMessageState(txn1, messageId, INVALID);
@@ -724,11 +588,8 @@ public class ValidationManagerImplTest extends BrambleMockTestCase {
 			// The message has two dependents: 1 and 2
 			oneOf(db).getMessageDependents(txn1, messageId);
 			will(returnValue(twoDependents));
-			oneOf(db).commitTransaction(txn1);
-			oneOf(db).endTransaction(txn1);
 			// Invalidate message 1
-			oneOf(db).startTransaction(false);
-			will(returnValue(txn2));
+			oneOf(db).transaction(with(false), withDbRunnable(txn2));
 			oneOf(db).getMessageState(txn2, messageId1);
 			will(returnValue(PENDING));
 			oneOf(db).setMessageState(txn2, messageId1, INVALID);
@@ -737,11 +598,8 @@ public class ValidationManagerImplTest extends BrambleMockTestCase {
 			// Message 1 has one dependent: 3
 			oneOf(db).getMessageDependents(txn2, messageId1);
 			will(returnValue(singletonMap(messageId3, PENDING)));
-			oneOf(db).commitTransaction(txn2);
-			oneOf(db).endTransaction(txn2);
 			// Invalidate message 2
-			oneOf(db).startTransaction(false);
-			will(returnValue(txn3));
+			oneOf(db).transaction(with(false), withDbRunnable(txn3));
 			oneOf(db).getMessageState(txn3, messageId2);
 			will(returnValue(PENDING));
 			oneOf(db).setMessageState(txn3, messageId2, INVALID);
@@ -750,11 +608,8 @@ public class ValidationManagerImplTest extends BrambleMockTestCase {
 			// Message 2 has one dependent: 3 (same dependent as 1)
 			oneOf(db).getMessageDependents(txn3, messageId2);
 			will(returnValue(singletonMap(messageId3, PENDING)));
-			oneOf(db).commitTransaction(txn3);
-			oneOf(db).endTransaction(txn3);
 			// Invalidate message 3 (via 1)
-			oneOf(db).startTransaction(false);
-			will(returnValue(txn4));
+			oneOf(db).transaction(with(false), withDbRunnable(txn4));
 			oneOf(db).getMessageState(txn4, messageId3);
 			will(returnValue(PENDING));
 			oneOf(db).setMessageState(txn4, messageId3, INVALID);
@@ -763,18 +618,12 @@ public class ValidationManagerImplTest extends BrambleMockTestCase {
 			// Message 3 has one dependent: 4
 			oneOf(db).getMessageDependents(txn4, messageId3);
 			will(returnValue(singletonMap(messageId4, PENDING)));
-			oneOf(db).commitTransaction(txn4);
-			oneOf(db).endTransaction(txn4);
 			// Invalidate message 3 (again, via 2)
-			oneOf(db).startTransaction(false);
-			will(returnValue(txn5));
+			oneOf(db).transaction(with(false), withDbRunnable(txn5));
 			oneOf(db).getMessageState(txn5, messageId3);
 			will(returnValue(INVALID)); // Already invalidated
-			oneOf(db).commitTransaction(txn5);
-			oneOf(db).endTransaction(txn5);
 			// Invalidate message 4 (via 1 and 3)
-			oneOf(db).startTransaction(false);
-			will(returnValue(txn6));
+			oneOf(db).transaction(with(false), withDbRunnable(txn6));
 			oneOf(db).getMessageState(txn6, messageId4);
 			will(returnValue(PENDING));
 			oneOf(db).setMessageState(txn6, messageId4, INVALID);
@@ -783,8 +632,6 @@ public class ValidationManagerImplTest extends BrambleMockTestCase {
 			// Message 4 has no dependents
 			oneOf(db).getMessageDependents(txn6, messageId4);
 			will(returnValue(emptyMap()));
-			oneOf(db).commitTransaction(txn6);
-			oneOf(db).endTransaction(txn6);
 		}});
 
 		vm.eventOccurred(new MessageAddedEvent(message, contactId));
@@ -810,20 +657,16 @@ public class ValidationManagerImplTest extends BrambleMockTestCase {
 		Transaction txn5 = new Transaction(null, false);
 		Transaction txn6 = new Transaction(null, false);
 
-		context.checking(new Expectations() {{
+		context.checking(new DbExpectations() {{
 			// Load the group
-			oneOf(db).startTransaction(true);
-			will(returnValue(txn));
+			oneOf(db).transactionWithResult(with(true), withDbCallable(txn));
 			oneOf(db).getGroup(txn, groupId);
 			will(returnValue(group));
-			oneOf(db).commitTransaction(txn);
-			oneOf(db).endTransaction(txn);
 			// Validate the message: valid
 			oneOf(validator).validateMessage(message, group);
 			will(returnValue(validResult));
 			// Store the validation result
-			oneOf(db).startTransaction(false);
-			will(returnValue(txn1));
+			oneOf(db).transaction(with(false), withDbRunnable(txn1));
 			oneOf(db).mergeMessageMetadata(txn1, messageId, metadata);
 			// Deliver the message
 			oneOf(hook).incomingMessage(txn1, message, metadata);
@@ -832,11 +675,8 @@ public class ValidationManagerImplTest extends BrambleMockTestCase {
 			// The message has two pending dependents: 1 and 2
 			oneOf(db).getMessageDependents(txn1, messageId);
 			will(returnValue(twoDependents));
-			oneOf(db).commitTransaction(txn1);
-			oneOf(db).endTransaction(txn1);
 			// Check whether message 1 is ready to be delivered
-			oneOf(db).startTransaction(false);
-			will(returnValue(txn2));
+			oneOf(db).transaction(with(false), withDbRunnable(txn2));
 			oneOf(db).getMessageState(txn2, messageId1);
 			will(returnValue(PENDING));
 			oneOf(db).getMessageDependencies(txn2, messageId1);
@@ -855,11 +695,8 @@ public class ValidationManagerImplTest extends BrambleMockTestCase {
 			// Message 1 has one pending dependent: 3
 			oneOf(db).getMessageDependents(txn2, messageId1);
 			will(returnValue(singletonMap(messageId3, PENDING)));
-			oneOf(db).commitTransaction(txn2);
-			oneOf(db).endTransaction(txn2);
 			// Check whether message 2 is ready to be delivered
-			oneOf(db).startTransaction(false);
-			will(returnValue(txn3));
+			oneOf(db).transaction(with(false), withDbRunnable(txn3));
 			oneOf(db).getMessageState(txn3, messageId2);
 			will(returnValue(PENDING));
 			oneOf(db).getMessageDependencies(txn3, messageId2);
@@ -878,11 +715,8 @@ public class ValidationManagerImplTest extends BrambleMockTestCase {
 			// Message 2 has one pending dependent: 3 (same dependent as 1)
 			oneOf(db).getMessageDependents(txn3, messageId2);
 			will(returnValue(singletonMap(messageId3, PENDING)));
-			oneOf(db).commitTransaction(txn3);
-			oneOf(db).endTransaction(txn3);
 			// Check whether message 3 is ready to be delivered (via 1)
-			oneOf(db).startTransaction(false);
-			will(returnValue(txn4));
+			oneOf(db).transaction(with(false), withDbRunnable(txn4));
 			oneOf(db).getMessageState(txn4, messageId3);
 			will(returnValue(PENDING));
 			oneOf(db).getMessageDependencies(txn4, messageId3);
@@ -900,18 +734,12 @@ public class ValidationManagerImplTest extends BrambleMockTestCase {
 			// Message 3 has one pending dependent: 4
 			oneOf(db).getMessageDependents(txn4, messageId3);
 			will(returnValue(singletonMap(messageId4, PENDING)));
-			oneOf(db).commitTransaction(txn4);
-			oneOf(db).endTransaction(txn4);
 			// Check whether message 3 is ready to be delivered (again, via 2)
-			oneOf(db).startTransaction(false);
-			will(returnValue(txn5));
+			oneOf(db).transaction(with(false), withDbRunnable(txn5));
 			oneOf(db).getMessageState(txn5, messageId3);
 			will(returnValue(DELIVERED)); // Already delivered
-			oneOf(db).commitTransaction(txn5);
-			oneOf(db).endTransaction(txn5);
 			// Check whether message 4 is ready to be delivered (via 1 and 3)
-			oneOf(db).startTransaction(false);
-			will(returnValue(txn6));
+			oneOf(db).transaction(with(false), withDbRunnable(txn6));
 			oneOf(db).getMessageState(txn6, messageId4);
 			will(returnValue(PENDING));
 			oneOf(db).getMessageDependencies(txn6, messageId4);
@@ -930,8 +758,6 @@ public class ValidationManagerImplTest extends BrambleMockTestCase {
 			// Message 4 has no pending dependents
 			oneOf(db).getMessageDependents(txn6, messageId4);
 			will(returnValue(emptyMap()));
-			oneOf(db).commitTransaction(txn6);
-			oneOf(db).endTransaction(txn6);
 		}});
 
 		vm.eventOccurred(new MessageAddedEvent(message, contactId));
@@ -946,20 +772,16 @@ public class ValidationManagerImplTest extends BrambleMockTestCase {
 		Transaction txn1 = new Transaction(null, false);
 		Transaction txn2 = new Transaction(null, false);
 
-		context.checking(new Expectations() {{
+		context.checking(new DbExpectations() {{
 			// Load the group
-			oneOf(db).startTransaction(true);
-			will(returnValue(txn));
+			oneOf(db).transactionWithResult(with(true), withDbCallable(txn));
 			oneOf(db).getGroup(txn, groupId);
 			will(returnValue(group));
-			oneOf(db).commitTransaction(txn);
-			oneOf(db).endTransaction(txn);
 			// Validate the message: valid
 			oneOf(validator).validateMessage(message, group);
 			will(returnValue(validResult));
 			// Store the validation result
-			oneOf(db).startTransaction(false);
-			will(returnValue(txn1));
+			oneOf(db).transaction(with(false), withDbRunnable(txn1));
 			oneOf(db).mergeMessageMetadata(txn1, messageId, metadata);
 			// Deliver the message
 			oneOf(hook).incomingMessage(txn1, message, metadata);
@@ -968,17 +790,12 @@ public class ValidationManagerImplTest extends BrambleMockTestCase {
 			// Get any pending dependents
 			oneOf(db).getMessageDependents(txn1, messageId);
 			will(returnValue(singletonMap(messageId1, PENDING)));
-			oneOf(db).commitTransaction(txn1);
-			oneOf(db).endTransaction(txn1);
 			// Check whether the pending dependent is ready to be delivered
-			oneOf(db).startTransaction(false);
-			will(returnValue(txn2));
+			oneOf(db).transaction(with(false), withDbRunnable(txn2));
 			oneOf(db).getMessageState(txn2, messageId1);
 			will(returnValue(PENDING));
 			oneOf(db).getMessageDependencies(txn2, messageId1);
 			will(returnValue(twoDependencies));
-			oneOf(db).commitTransaction(txn2);
-			oneOf(db).endTransaction(txn2);
 		}});
 
 		vm.eventOccurred(new MessageAddedEvent(message, contactId));

bramble-core/src/test/java/org/briarproject/bramble/test/DbExpectations.java

@@ -0,0 +1,33 @@
+package org.briarproject.bramble.test;
+
+import org.briarproject.bramble.api.db.DbCallable;
+import org.briarproject.bramble.api.db.DbRunnable;
+import org.briarproject.bramble.api.db.NullableDbCallable;
+import org.briarproject.bramble.api.db.Transaction;
+import org.jmock.Expectations;
+
+public class DbExpectations extends Expectations {
+
+	protected <E extends Exception> DbRunnable<E> withDbRunnable(
+			Transaction txn) {
+		addParameterMatcher(any(DbRunnable.class));
+		currentBuilder().setAction(new RunTransactionAction(txn));
+		return null;
+	}
+
+	protected <R, E extends Exception> DbCallable<R, E> withDbCallable(
+			Transaction txn) {
+		addParameterMatcher(any(DbCallable.class));
+		currentBuilder().setAction(new RunTransactionWithResultAction(txn));
+		return null;
+	}
+
+	protected <R, E extends Exception> NullableDbCallable<R, E> withNullableDbCallable(
+			Transaction txn) {
+		addParameterMatcher(any(NullableDbCallable.class));
+		currentBuilder().setAction(
+				new RunTransactionWithNullableResultAction(txn));
+		return null;
+	}
+
+}

bramble-core/src/test/java/org/briarproject/bramble/test/RunTransactionAction.java

@@ -0,0 +1,30 @@
+package org.briarproject.bramble.test;
+
+import org.briarproject.bramble.api.db.DbRunnable;
+import org.briarproject.bramble.api.db.Transaction;
+import org.hamcrest.Description;
+import org.jmock.api.Action;
+import org.jmock.api.Invocation;
+
+public class RunTransactionAction implements Action {
+
+	private final Transaction txn;
+
+	@SuppressWarnings("WeakerAccess")
+	public RunTransactionAction(Transaction txn) {
+		this.txn = txn;
+	}
+
+	@Override
+	public Object invoke(Invocation invocation) throws Throwable {
+		DbRunnable task = (DbRunnable) invocation.getParameter(1);
+		task.run(txn);
+		return null;
+	}
+
+	@Override
+	public void describeTo(Description description) {
+		description.appendText("runs a task inside a database transaction");
+	}
+
+}

bramble-core/src/test/java/org/briarproject/bramble/test/RunTransactionWithNullableResultAction.java

@@ -0,0 +1,28 @@
+package org.briarproject.bramble.test;
+
+import org.briarproject.bramble.api.db.NullableDbCallable;
+import org.briarproject.bramble.api.db.Transaction;
+import org.hamcrest.Description;
+import org.jmock.api.Action;
+import org.jmock.api.Invocation;
+
+public class RunTransactionWithNullableResultAction implements Action {
+
+	private final Transaction txn;
+
+	public RunTransactionWithNullableResultAction(Transaction txn) {
+		this.txn = txn;
+	}
+
+	@Override
+	public Object invoke(Invocation invocation) throws Throwable {
+		NullableDbCallable task =
+				(NullableDbCallable) invocation.getParameter(1);
+		return task.call(txn);
+	}
+
+	@Override
+	public void describeTo(Description description) {
+		description.appendText("runs a task inside a database transaction");
+	}
+}

bramble-core/src/test/java/org/briarproject/bramble/test/RunTransactionWithResultAction.java

@@ -0,0 +1,27 @@
+package org.briarproject.bramble.test;
+
+import org.briarproject.bramble.api.db.DbCallable;
+import org.briarproject.bramble.api.db.Transaction;
+import org.hamcrest.Description;
+import org.jmock.api.Action;
+import org.jmock.api.Invocation;
+
+public class RunTransactionWithResultAction implements Action {
+
+	private final Transaction txn;
+
+	public RunTransactionWithResultAction(Transaction txn) {
+		this.txn = txn;
+	}
+
+	@Override
+	public Object invoke(Invocation invocation) throws Throwable {
+		DbCallable task = (DbCallable) invocation.getParameter(1);
+		return task.call(txn);
+	}
+
+	@Override
+	public void describeTo(Description description) {
+		description.appendText("runs a task inside a database transaction");
+	}
+}

bramble-core/src/test/java/org/briarproject/bramble/transport/KeyManagerImplTest.java

@@ -15,6 +15,7 @@ import org.briarproject.bramble.api.plugin.simplex.SimplexPluginFactory;
 import org.briarproject.bramble.api.transport.KeySetId;
 import org.briarproject.bramble.api.transport.StreamContext;
 import org.briarproject.bramble.test.BrambleMockTestCase;
+import org.briarproject.bramble.test.DbExpectations;
 import org.jmock.Expectations;
 import org.jmock.lib.concurrent.DeterministicExecutor;
 import org.junit.Before;
@@ -33,7 +34,9 @@ import static org.briarproject.bramble.test.TestUtils.getRandomBytes;
 import static org.briarproject.bramble.test.TestUtils.getRandomId;
 import static org.briarproject.bramble.test.TestUtils.getSecretKey;
 import static org.briarproject.bramble.test.TestUtils.getTransportId;
+import static org.briarproject.bramble.util.StringUtils.getRandomString;
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNull;
 
 public class KeyManagerImplTest extends BrambleMockTestCase {
 
@@ -66,17 +69,17 @@ public class KeyManagerImplTest extends BrambleMockTestCase {
 		Author remoteAuthor = getAuthor();
 		AuthorId localAuthorId = new AuthorId(getRandomId());
 		Collection<Contact> contacts = new ArrayList<>();
-		contacts.add(new Contact(contactId, remoteAuthor, localAuthorId, true,
-				true));
+		contacts.add(new Contact(contactId, remoteAuthor, localAuthorId,
+				getRandomString(5), true, true));
 		contacts.add(new Contact(inactiveContactId, remoteAuthor, localAuthorId,
-				true, false));
+				getRandomString(5), true, false));
 		SimplexPluginFactory pluginFactory =
 				context.mock(SimplexPluginFactory.class);
 		Collection<SimplexPluginFactory> factories =
 				singletonList(pluginFactory);
 		int maxLatency = 1337;
 
-		context.checking(new Expectations() {{
+		context.checking(new DbExpectations() {{
 			oneOf(pluginConfig).getSimplexFactories();
 			will(returnValue(factories));
 			oneOf(pluginFactory).getId();
@@ -88,13 +91,10 @@ public class KeyManagerImplTest extends BrambleMockTestCase {
 					.createTransportKeyManager(transportId, maxLatency);
 			will(returnValue(transportKeyManager));
 			oneOf(pluginConfig).getDuplexFactories();
-			oneOf(db).startTransaction(false);
-			will(returnValue(txn));
+			oneOf(db).transaction(with(false), withDbRunnable(txn));
 			oneOf(db).getContacts(txn);
 			will(returnValue(contacts));
 			oneOf(transportKeyManager).start(txn);
-			oneOf(db).commitTransaction(txn);
-			oneOf(db).endTransaction(txn);
 		}});
 
 		keyManager.startService();
@@ -120,25 +120,21 @@ public class KeyManagerImplTest extends BrambleMockTestCase {
 
 	@Test
 	public void testGetStreamContextForInactiveContact() throws Exception {
-		assertEquals(null,
-				keyManager.getStreamContext(inactiveContactId, transportId));
+		assertNull(keyManager.getStreamContext(inactiveContactId, transportId));
 	}
 
 	@Test
 	public void testGetStreamContextForUnknownTransport() throws Exception {
-		assertEquals(null,
-				keyManager.getStreamContext(contactId, unknownTransportId));
+		assertNull(keyManager.getStreamContext(contactId, unknownTransportId));
 	}
 
 	@Test
 	public void testGetStreamContextForContact() throws Exception {
-		context.checking(new Expectations() {{
-			oneOf(db).startTransaction(false);
-			will(returnValue(txn));
+		context.checking(new DbExpectations() {{
+			oneOf(db).transactionWithNullableResult(with(false),
+					withNullableDbCallable(txn));
 			oneOf(transportKeyManager).getStreamContext(txn, contactId);
 			will(returnValue(streamContext));
-			oneOf(db).commitTransaction(txn);
-			oneOf(db).endTransaction(txn);
 		}});
 
 		assertEquals(streamContext,
@@ -148,19 +144,16 @@ public class KeyManagerImplTest extends BrambleMockTestCase {
 	@Test
 	public void testGetStreamContextForTagAndUnknownTransport()
 			throws Exception {
-		assertEquals(null,
-				keyManager.getStreamContext(unknownTransportId, tag));
+		assertNull(keyManager.getStreamContext(unknownTransportId, tag));
 	}
 
 	@Test
 	public void testGetStreamContextForTag() throws Exception {
-		context.checking(new Expectations() {{
-			oneOf(db).startTransaction(false);
-			will(returnValue(txn));
+		context.checking(new DbExpectations() {{
+			oneOf(db).transactionWithNullableResult(with(false),
+					withNullableDbCallable(txn));
 			oneOf(transportKeyManager).getStreamContext(txn, tag);
 			will(returnValue(streamContext));
-			oneOf(db).commitTransaction(txn);
-			oneOf(db).endTransaction(txn);
 		}});
 
 		assertEquals(streamContext,
@@ -177,7 +170,7 @@ public class KeyManagerImplTest extends BrambleMockTestCase {
 
 		keyManager.eventOccurred(event);
 		executor.runUntilIdle();
-		assertEquals(null, keyManager.getStreamContext(contactId, transportId));
+		assertNull(keyManager.getStreamContext(contactId, transportId));
 	}
 
 	@Test
@@ -185,13 +178,11 @@ public class KeyManagerImplTest extends BrambleMockTestCase {
 		ContactStatusChangedEvent event =
 				new ContactStatusChangedEvent(inactiveContactId, true);
 
-		context.checking(new Expectations() {{
-			oneOf(db).startTransaction(false);
-			will(returnValue(txn));
+		context.checking(new DbExpectations() {{
+			oneOf(db).transactionWithNullableResult(with(false),
+					withNullableDbCallable(txn));
 			oneOf(transportKeyManager).getStreamContext(txn, inactiveContactId);
 			will(returnValue(streamContext));
-			oneOf(db).commitTransaction(txn);
-			oneOf(db).endTransaction(txn);
 		}});
 
 		keyManager.eventOccurred(event);

bramble-core/src/test/java/org/briarproject/bramble/transport/TransportKeyManagerImplTest.java

@@ -14,6 +14,7 @@ import org.briarproject.bramble.api.transport.OutgoingKeys;
 import org.briarproject.bramble.api.transport.StreamContext;
 import org.briarproject.bramble.api.transport.TransportKeys;
 import org.briarproject.bramble.test.BrambleMockTestCase;
+import org.briarproject.bramble.test.DbExpectations;
 import org.briarproject.bramble.test.RunAction;
 import org.briarproject.bramble.test.TestUtils;
 import org.hamcrest.Description;
@@ -318,7 +319,7 @@ public class TransportKeyManagerImplTest extends BrambleMockTestCase {
 		Transaction txn = new Transaction(null, false);
 		Transaction txn1 = new Transaction(null, false);
 
-		context.checking(new Expectations() {{
+		context.checking(new DbExpectations() {{
 			// Get the current time (the start of rotation period 1000)
 			oneOf(clock).currentTimeMillis();
 			will(returnValue(rotationPeriodLength * 1000));
@@ -342,8 +343,7 @@ public class TransportKeyManagerImplTest extends BrambleMockTestCase {
 			oneOf(dbExecutor).execute(with(any(Runnable.class)));
 			will(new RunAction());
 			// Start a transaction for key rotation
-			oneOf(db).startTransaction(false);
-			will(returnValue(txn1));
+			oneOf(db).transaction(with(false), withDbRunnable(txn1));
 			// Get the current time (the start of rotation period 1001)
 			oneOf(clock).currentTimeMillis();
 			will(returnValue(rotationPeriodLength * 1001));
@@ -364,9 +364,6 @@ public class TransportKeyManagerImplTest extends BrambleMockTestCase {
 			// Schedule key rotation at the start of the next rotation period
 			oneOf(scheduler).schedule(with(any(Runnable.class)),
 					with(rotationPeriodLength), with(MILLISECONDS));
-			// Commit the key rotation transaction
-			oneOf(db).commitTransaction(txn1);
-			oneOf(db).endTransaction(txn1);
 		}});
 
 		TransportKeyManager transportKeyManager = new TransportKeyManagerImpl(
@@ -539,7 +536,7 @@ public class TransportKeyManagerImplTest extends BrambleMockTestCase {
 		}
 
 		@Override
-		public Object invoke(Invocation invocation) throws Throwable {
+		public Object invoke(Invocation invocation) {
 			byte[] tag = (byte[]) invocation.getParameter(0);
 			random.nextBytes(tag);
 			if (tags != null) tags.add(tag);

bramble-core/src/test/java/org/briarproject/bramble/versioning/ClientVersioningManagerImplTest.java

@@ -18,6 +18,7 @@ import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.bramble.api.system.Clock;
 import org.briarproject.bramble.api.versioning.ClientVersioningManager.ClientVersioningHook;
 import org.briarproject.bramble.test.BrambleMockTestCase;
+import org.briarproject.bramble.test.DbExpectations;
 import org.jmock.Expectations;
 import org.junit.Test;
 
@@ -38,6 +39,7 @@ import static org.briarproject.bramble.test.TestUtils.getGroup;
 import static org.briarproject.bramble.test.TestUtils.getLocalAuthor;
 import static org.briarproject.bramble.test.TestUtils.getMessage;
 import static org.briarproject.bramble.test.TestUtils.getRandomId;
+import static org.briarproject.bramble.util.StringUtils.getRandomString;
 import static org.briarproject.bramble.versioning.ClientVersioningConstants.GROUP_KEY_CONTACT_ID;
 import static org.briarproject.bramble.versioning.ClientVersioningConstants.MSG_KEY_LOCAL;
 import static org.briarproject.bramble.versioning.ClientVersioningConstants.MSG_KEY_UPDATE_VERSION;
@@ -56,12 +58,13 @@ public class ClientVersioningManagerImplTest extends BrambleMockTestCase {
 	private final Group localGroup = getGroup(CLIENT_ID, MAJOR_VERSION);
 	private final Group contactGroup = getGroup(CLIENT_ID, MAJOR_VERSION);
 	private final Contact contact = new Contact(new ContactId(123),
-			getAuthor(), getLocalAuthor().getId(), true, true);
+			getAuthor(), getLocalAuthor().getId(), getRandomString(5), true,
+			true);
 	private final ClientId clientId = getClientId();
 	private final long now = System.currentTimeMillis();
 	private final Transaction txn = new Transaction(null, false);
 
-	private ClientVersioningManagerImpl createInstance() throws Exception {
+	private ClientVersioningManagerImpl createInstance() {
 		context.checking(new Expectations() {{
 			oneOf(contactGroupFactory).createLocalGroup(CLIENT_ID,
 					MAJOR_VERSION);
@@ -160,9 +163,8 @@ public class ClientVersioningManagerImplTest extends BrambleMockTestCase {
 		BdfList localUpdateBody = BdfList.of(BdfList.of(
 				BdfList.of(clientId.getString(), 123, 234, false)), 1L);
 
-		context.checking(new Expectations() {{
-			oneOf(db).startTransaction(false);
-			will(returnValue(txn));
+		context.checking(new DbExpectations() {{
+			oneOf(db).transaction(with(false), withDbRunnable(txn));
 			// No client versions have been stored yet
 			oneOf(db).getMessageIds(txn, localGroup.getId());
 			will(returnValue(emptyList()));
@@ -188,8 +190,6 @@ public class ClientVersioningManagerImplTest extends BrambleMockTestCase {
 			oneOf(clientHelper).getMessageAsList(txn, localUpdateId);
 			will(returnValue(localUpdateBody));
 			// Latest local update is up-to-date, no visibilities have changed
-			oneOf(db).commitTransaction(txn);
-			oneOf(db).endTransaction(txn);
 		}});
 
 		ClientVersioningManagerImpl c = createInstance();
@@ -204,17 +204,14 @@ public class ClientVersioningManagerImplTest extends BrambleMockTestCase {
 		BdfList localVersionsBody =
 				BdfList.of(BdfList.of(clientId.getString(), 123, 234));
 
-		context.checking(new Expectations() {{
-			oneOf(db).startTransaction(false);
-			will(returnValue(txn));
+		context.checking(new DbExpectations() {{
+			oneOf(db).transaction(with(false), withDbRunnable(txn));
 			// Load the old client versions
 			oneOf(db).getMessageIds(txn, localGroup.getId());
 			will(returnValue(singletonList(localVersionsId)));
 			oneOf(clientHelper).getMessageAsList(txn, localVersionsId);
 			will(returnValue(localVersionsBody));
 			// Client versions are up-to-date
-			oneOf(db).commitTransaction(txn);
-			oneOf(db).endTransaction(txn);
 		}});
 
 		ClientVersioningManagerImpl c = createInstance();
@@ -249,9 +246,8 @@ public class ClientVersioningManagerImplTest extends BrambleMockTestCase {
 				new BdfEntry(MSG_KEY_UPDATE_VERSION, 2L),
 				new BdfEntry(MSG_KEY_LOCAL, true));
 
-		context.checking(new Expectations() {{
-			oneOf(db).startTransaction(false);
-			will(returnValue(txn));
+		context.checking(new DbExpectations() {{
+			oneOf(db).transaction(with(false), withDbRunnable(txn));
 			// Load the old client versions
 			oneOf(db).getMessageIds(txn, localGroup.getId());
 			will(returnValue(singletonList(oldLocalVersionsId)));
@@ -293,8 +289,6 @@ public class ClientVersioningManagerImplTest extends BrambleMockTestCase {
 			oneOf(clientHelper).addLocalMessage(txn, newLocalUpdate,
 					newLocalUpdateMeta, true);
 			// No visibilities have changed
-			oneOf(db).commitTransaction(txn);
-			oneOf(db).endTransaction(txn);
 		}});
 
 		ClientVersioningManagerImpl c = createInstance();
@@ -348,9 +342,8 @@ public class ClientVersioningManagerImplTest extends BrambleMockTestCase {
 				new BdfEntry(MSG_KEY_UPDATE_VERSION, 2L),
 				new BdfEntry(MSG_KEY_LOCAL, true));
 
-		context.checking(new Expectations() {{
-			oneOf(db).startTransaction(false);
-			will(returnValue(txn));
+		context.checking(new DbExpectations() {{
+			oneOf(db).transaction(with(false), withDbRunnable(txn));
 			// Load the old client versions
 			oneOf(db).getMessageIds(txn, localGroup.getId());
 			will(returnValue(singletonList(oldLocalVersionsId)));
@@ -395,8 +388,6 @@ public class ClientVersioningManagerImplTest extends BrambleMockTestCase {
 					newLocalUpdateMeta, true);
 			// The client's visibility has changed
 			oneOf(hook).onClientVisibilityChanging(txn, contact, visibility);
-			oneOf(db).commitTransaction(txn);
-			oneOf(db).endTransaction(txn);
 		}});
 
 		ClientVersioningManagerImpl c = createInstance();

bramble-core/witness.gradle

@@ -1,12 +1,20 @@
 dependencyVerification {
     verify = [
         'cglib:cglib:3.2.0:cglib-3.2.0.jar:adb13bab79712ad6bdf1bd59f2a3918018a8016e722e8a357065afb9e6690861',
-        'com.google.dagger:dagger-compiler:2.0.2:dagger-compiler-2.0.2.jar:b74bc9de063dd4c6400b232231f2ef5056145b8fbecbf5382012007dd1c071b3',
-        'com.google.dagger:dagger-producers:2.0-beta:dagger-producers-2.0-beta.jar:99ec15e8a0507ba569e7655bc1165ee5e5ca5aa914b3c8f7e2c2458f724edd6b',
-        'com.google.dagger:dagger:2.0.2:dagger-2.0.2.jar:84c0282ed8be73a29e0475d639da030b55dee72369e58dd35ae7d4fe6243dcf9',
-        'com.google.guava:guava:18.0:guava-18.0.jar:d664fbfc03d2e5ce9cab2a44fb01f1d0bf9dfebeccc1a473b1f9ea31f79f6f99',
+        'com.google.code.findbugs:jsr305:1.3.9:jsr305-1.3.9.jar:905721a0eea90a81534abb7ee6ef4ea2e5e645fa1def0a5cd88402df1b46c9ed',
+        'com.google.dagger:dagger-compiler:2.19:dagger-compiler-2.19.jar:27a4b202a2de908182edb261f8c0a264e08e5e4733d7514bc7fbf0d31da5c0fc',
+        'com.google.dagger:dagger-producers:2.19:dagger-producers-2.19.jar:a17663abe0fc38b676026950907d4c5f5e2bf338375415861eaff6e3bdb0b768',
+        'com.google.dagger:dagger-spi:2.19:dagger-spi-2.19.jar:e7a6379d82c841f6aac2866948ad1eed716528707814602842a8d844ce04e2e1',
+        'com.google.dagger:dagger:2.19:dagger-2.19.jar:514b6f1e0727c6572e1d65cb27e4ae668b7aeaeb93a29515182965265b609939',
+        'com.google.errorprone:error_prone_annotations:2.1.3:error_prone_annotations-2.1.3.jar:03d0329547c13da9e17c634d1049ea2ead093925e290567e1a364fd6b1fc7ff8',
+        'com.google.errorprone:javac-shaded:9-dev-r4023-3:javac-shaded-9-dev-r4023-3.jar:65bfccf60986c47fbc17c9ebab0be626afc41741e0a6ec7109e0768817a36f30',
+        'com.google.googlejavaformat:google-java-format:1.5:google-java-format-1.5.jar:aa19ad7850fb85178aa22f2fddb163b84d6ce4d0035872f30d4408195ca1144e',
+        'com.google.guava:guava:25.0-jre:guava-25.0-jre.jar:3fd4341776428c7e0e5c18a7c10de129475b69ab9d30aeafbb5c277bb6074fa9',
+        'com.google.j2objc:j2objc-annotations:1.1:j2objc-annotations-1.1.jar:40ceb7157feb263949e0f503fe5f71689333a621021aa20ce0d0acee3badaa0f',
         'com.h2database:h2:1.4.192:h2-1.4.192.jar:225b22e9857235c46c93861410b60b8c81c10dc8985f4faf188985ba5445126c',
         'com.madgag.spongycastle:core:1.58.0.0:core-1.58.0.0.jar:199617dd5698c5a9312b898c0a4cec7ce9dd8649d07f65d91629f58229d72728',
+        'com.squareup:javapoet:1.11.1:javapoet-1.11.1.jar:9cbf2107be499ec6e95afd36b58e3ca122a24166cdd375732e51267d64058e90',
+        'javax.annotation:jsr250-api:1.0:jsr250-api-1.0.jar:a1a922d0d9b6d183ed3800dfac01d1e1eb159f0e8c6f94736931c1def54a941f',
         'javax.inject:javax.inject:1:javax.inject-1.jar:91c77044a50c481636c32d916fd89c9118a72195390452c81065080f957de7ff',
         'junit:junit:4.12:junit-4.12.jar:59721f0805e223d84b90677887d9ff567dc534d7c502ca903c0c2b17f05c116a',
         'net.i2p.crypto:eddsa:0.2.0:eddsa-0.2.0.jar:a7cb1b85c16e2f0730b9204106929a1d9aaae1df728adc7041a8b8b605692140',
@@ -15,7 +23,9 @@ dependencyVerification {
         'org.beanshell:bsh:1.3.0:bsh-1.3.0.jar:9b04edc75d19db54f1b4e8b5355e9364384c6cf71eb0a1b9724c159d779879f8',
         'org.bitlet:weupnp:0.1.4:weupnp-0.1.4.jar:88df7e6504929d00bdb832863761385c68ab92af945b04f0770b126270a444fb',
         'org.briarproject:jtorctl:0.3:jtorctl-0.3.jar:f2939238a097898998432effe93b0334d97a787972ab3a91a8973a1d309fc864',
+        'org.checkerframework:checker-compat-qual:2.5.3:checker-compat-qual-2.5.3.jar:d76b9afea61c7c082908023f0cbc1427fab9abd2df915c8b8a3e7a509bccbc6d',
         'org.codehaus.mojo.signature:java16:1.1:java16-1.1.signature:53799223a2c98dba2d0add810bed76315460df285c69e4f397ae6098f87dd619',
+        'org.codehaus.mojo:animal-sniffer-annotations:1.14:animal-sniffer-annotations-1.14.jar:2068320bd6bad744c3673ab048f67e30bef8f518996fa380033556600669905d',
         'org.codehaus.mojo:animal-sniffer-ant-tasks:1.16:animal-sniffer-ant-tasks-1.16.jar:890040976fbe2d584619a6a61b1fd2e925b3b5eb342a85eb2762c467c0d64e90',
         'org.codehaus.mojo:animal-sniffer:1.16:animal-sniffer-1.16.jar:72be8bcc226ba43b937c722a08a07852bfa1b11400089265d5df0ee7b38b1d52',
         'org.hamcrest:hamcrest-core:1.3:hamcrest-core-1.3.jar:66fdef91e9739348df7a096aa384a5685f4e875584cce89386a7a47251c4d8e9',
@@ -28,6 +38,6 @@ dependencyVerification {
         'org.objenesis:objenesis:2.1:objenesis-2.1.jar:c74330cc6b806c804fd37e74487b4fe5d7c2750c5e15fbc6efa13bdee1bdef80',
         'org.ow2.asm:asm-all:5.2:asm-all-5.2.jar:7fbffbc1db3422e2101689fd88df8384b15817b52b9b2b267b9f6d2511dc198d',
         'org.ow2.asm:asm:5.0.4:asm-5.0.4.jar:896618ed8ae62702521a78bc7be42b7c491a08e6920a15f89a3ecdec31e9a220',
-        'org.whispersystems:curve25519-java:0.4.1:curve25519-java-0.4.1.jar:7dd659d8822c06c3aea1a47f18fac9e5761e29cab8100030b877db445005f03e',
+        'org.whispersystems:curve25519-java:0.5.0:curve25519-java-0.5.0.jar:0aadd43cf01d11e9b58f867b3c4f25c3194e8b0623d1953d32dfbfbee009e38d',
     ]
 }

bramble-java/build.gradle

@@ -2,10 +2,10 @@ apply plugin: 'java-library'
 sourceCompatibility = 1.8
 targetCompatibility = 1.8
 
-apply plugin: 'net.ltgt.apt'
 apply plugin: 'idea'
 apply plugin: 'witness'
 apply from: 'witness.gradle'
+apply from: '../dagger.gradle'
 
 configurations {
 	tor
@@ -14,11 +14,12 @@ configurations {
 dependencies {
 	implementation project(path: ':bramble-core', configuration: 'default')
 	implementation fileTree(dir: 'libs', include: '*.jar')
-	implementation 'net.java.dev.jna:jna:4.4.0'
-	implementation 'net.java.dev.jna:jna-platform:4.4.0'
-	tor 'org.briarproject:tor:0.2.9.16@zip'
+	implementation 'net.java.dev.jna:jna:4.5.2'
+	implementation 'net.java.dev.jna:jna-platform:4.5.2'
+	tor 'org.briarproject:tor:0.3.4.8@zip'
+	tor 'org.briarproject:obfs4proxy:0.0.7@zip'
 
-	apt 'com.google.dagger:dagger-compiler:2.0.2'
+	annotationProcessor 'com.google.dagger:dagger-compiler:2.19'
 
 	testImplementation project(path: ':bramble-api', configuration: 'testOutput')
 	testImplementation project(path: ':bramble-core', configuration: 'testOutput')
@@ -26,19 +27,35 @@ dependencies {
 	testImplementation "org.jmock:jmock:2.8.2"
 	testImplementation "org.jmock:jmock-junit4:2.8.2"
 	testImplementation "org.jmock:jmock-legacy:2.8.2"
-	testImplementation "org.hamcrest:hamcrest-library:1.3"
-	testImplementation "org.hamcrest:hamcrest-core:1.3"
 
-	testApt 'com.google.dagger:dagger-compiler:2.0.2'
+	testAnnotationProcessor 'com.google.dagger:dagger-compiler:2.19'
 }
 
-project.afterEvaluate {
-	copy {
-		from configurations.tor.collect { zipTree(it) }
-		into 'src/main/resources'
+def torBinariesDir = 'src/main/resources'
+
+task cleanTorBinaries {
+	doLast {
+		delete fileTree(torBinariesDir) { include '*.zip' }
 	}
 }
 
+clean.dependsOn cleanTorBinaries
+
+task unpackTorBinaries {
+	doLast {
+		copy {
+			from configurations.tor.collect { zipTree(it) }
+			into torBinariesDir
+		}
+	}
+	dependsOn cleanTorBinaries
+}
+
+processResources {
+	inputs.dir torBinariesDir
+	dependsOn unpackTorBinaries
+}
+
 tasks.withType(Test) {
 	systemProperty 'java.library.path', 'libs'
 }

bramble-java/src/main/java/org/briarproject/bramble/network/JavaNetworkManager.java

@@ -1,10 +1,7 @@
 package org.briarproject.bramble.network;
 
-import org.briarproject.bramble.api.event.EventBus;
-import org.briarproject.bramble.api.lifecycle.Service;
 import org.briarproject.bramble.api.network.NetworkManager;
 import org.briarproject.bramble.api.network.NetworkStatus;
-import org.briarproject.bramble.api.network.event.NetworkStatusEvent;
 import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
 import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
 
@@ -23,25 +20,13 @@ import static org.briarproject.bramble.util.LogUtils.logException;
 
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
-class JavaNetworkManager implements NetworkManager, Service {
+class JavaNetworkManager implements NetworkManager {
 
 	private static final Logger LOG =
 			Logger.getLogger(JavaNetworkManager.class.getName());
 
-	private final EventBus eventBus;
-
 	@Inject
-	JavaNetworkManager(EventBus eventBus) {
-		this.eventBus = eventBus;
-	}
-
-	@Override
-	public void startService() {
-		eventBus.broadcast(new NetworkStatusEvent(getNetworkStatus()));
-	}
-
-	@Override
-	public void stopService() {
+	JavaNetworkManager() {
 	}
 
 	@Override

bramble-java/src/main/java/org/briarproject/bramble/network/JavaNetworkModule.java

@@ -1,6 +1,5 @@
 package org.briarproject.bramble.network;
 
-import org.briarproject.bramble.api.lifecycle.LifecycleManager;
 import org.briarproject.bramble.api.network.NetworkManager;
 
 import javax.inject.Singleton;
@@ -13,9 +12,7 @@ public class JavaNetworkModule {
 
 	@Provides
 	@Singleton
-	NetworkManager provideNetworkManager(LifecycleManager lifecycleManager,
-			JavaNetworkManager networkManager) {
-		lifecycleManager.registerService(networkManager);
+	NetworkManager provideNetworkManager(JavaNetworkManager networkManager) {
 		return networkManager;
 	}
 }

bramble-java/src/main/java/org/briarproject/bramble/plugin/bluetooth/JavaBluetoothPlugin.java

@@ -108,6 +108,12 @@ class JavaBluetoothPlugin extends BluetoothPlugin<StreamConnectionNotifier> {
 		return wrapSocket((StreamConnection) Connector.open(url));
 	}
 
+	@Override
+	@Nullable
+	DuplexTransportConnection discoverAndConnect(String uuid) {
+		return null; // TODO
+	}
+
 	private String makeUrl(String address, String uuid) {
 		return "btspp://" + address + ":" + uuid + ";name=RFCOMM";
 	}