Hide menu items on API < 19.

bramble-android/src/main/java/org/briarproject/bramble/account/AndroidAccountManager.java

@@ -5,12 +5,15 @@ import android.content.Context;
 import android.content.SharedPreferences;
 import android.preference.PreferenceManager;
 
+import org.briarproject.bramble.api.FeatureFlags;
 import org.briarproject.bramble.api.account.AccountManager;
 import org.briarproject.bramble.api.crypto.CryptoComponent;
 import org.briarproject.bramble.api.db.DatabaseConfig;
 import org.briarproject.bramble.api.identity.IdentityManager;
+import org.briarproject.bramble.api.logging.PersistentLogManager;
 
 import java.io.File;
+import java.io.IOException;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Set;
@@ -23,14 +26,18 @@ import javax.inject.Inject;
 import static android.os.Build.VERSION.SDK_INT;
 import static java.util.Arrays.asList;
 import static java.util.logging.Level.INFO;
+import static java.util.logging.Level.WARNING;
+import static java.util.logging.Logger.getLogger;
+import static org.briarproject.bramble.util.AndroidUtils.getPersistentLogDir;
 import static org.briarproject.bramble.util.IoUtils.deleteFileOrDir;
+import static org.briarproject.bramble.util.LogUtils.logException;
 import static org.briarproject.bramble.util.LogUtils.logFileOrDir;
 
 class AndroidAccountManager extends AccountManagerImpl
 		implements AccountManager {
 
 	private static final Logger LOG =
-			Logger.getLogger(AndroidAccountManager.class.getName());
+			getLogger(AndroidAccountManager.class.getName());
 
 	/**
 	 * Directories that shouldn't be deleted when deleting the user's account.
@@ -40,13 +47,22 @@ class AndroidAccountManager extends AccountManagerImpl
 
 	protected final Context appContext;
 	private final SharedPreferences prefs;
+	private final PersistentLogManager logManager;
+	private final FeatureFlags featureFlags;
 
 	@Inject
-	AndroidAccountManager(DatabaseConfig databaseConfig,
-			CryptoComponent crypto, IdentityManager identityManager,
-			SharedPreferences prefs, Application app) {
+	AndroidAccountManager(
+			DatabaseConfig databaseConfig,
+			CryptoComponent crypto,
+			IdentityManager identityManager,
+			SharedPreferences prefs,
+			PersistentLogManager logManager,
+			FeatureFlags featureFlags,
+			Application app) {
 		super(databaseConfig, crypto, identityManager);
 		this.prefs = prefs;
+		this.logManager = logManager;
+		this.featureFlags = featureFlags;
 		appContext = app.getApplicationContext();
 	}
 
@@ -74,6 +90,9 @@ class AndroidAccountManager extends AccountManagerImpl
 				LOG.info("Contents of account directory after deleting:");
 				logFileOrDir(LOG, INFO, getDataDir());
 			}
+			if (featureFlags.shouldEnablePersistentLogs()) {
+				replacePersistentLogger();
+			}
 		}
 	}
 
@@ -134,4 +153,13 @@ class AndroidAccountManager extends AccountManagerImpl
 	private void addIfNotNull(Set<File> files, @Nullable File file) {
 		if (file != null) files.add(file);
 	}
+
+	private void replacePersistentLogger() {
+		File logDir = getPersistentLogDir(appContext);
+		try {
+			logManager.addLogHandler(logDir, getLogger(""));
+		} catch (IOException e) {
+			logException(LOG, WARNING, e);
+		}
+	}
 }

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

@@ -111,10 +111,14 @@ public class AndroidUtils {
 		return ctx.getDir(STORED_REPORTS, MODE_PRIVATE);
 	}
 
-	public static File getLogcatFile(Context ctx) {
+	public static File getTemporaryLogFile(Context ctx) {
 		return new File(ctx.getFilesDir(), STORED_LOGCAT);
 	}
 
+	public static File getPersistentLogDir(Context ctx) {
+		return ctx.getDir("log", MODE_PRIVATE);
+	}
+
 	/**
 	 * Returns an array of supported content types for image attachments.
 	 */

bramble-android/src/test/java/org/briarproject/bramble/account/AndroidAccountManagerTest.java

@@ -4,9 +4,11 @@ import android.app.Application;
 import android.content.SharedPreferences;
 import android.content.pm.ApplicationInfo;
 
+import org.briarproject.bramble.api.FeatureFlags;
 import org.briarproject.bramble.api.crypto.CryptoComponent;
 import org.briarproject.bramble.api.db.DatabaseConfig;
 import org.briarproject.bramble.api.identity.IdentityManager;
+import org.briarproject.bramble.api.logging.PersistentLogManager;
 import org.briarproject.bramble.test.BrambleMockTestCase;
 import org.jmock.Expectations;
 import org.jmock.lib.legacy.ClassImposteriser;
@@ -15,7 +17,9 @@ import org.junit.Before;
 import org.junit.Test;
 
 import java.io.File;
+import java.util.logging.Logger;
 
+import static android.content.Context.MODE_PRIVATE;
 import static junit.framework.Assert.assertFalse;
 import static junit.framework.Assert.assertTrue;
 import static org.briarproject.bramble.test.TestUtils.deleteTestDirectory;
@@ -27,6 +31,10 @@ public class AndroidAccountManagerTest extends BrambleMockTestCase {
 			context.mock(SharedPreferences.class, "prefs");
 	private final SharedPreferences defaultPrefs =
 			context.mock(SharedPreferences.class, "defaultPrefs");
+	private final PersistentLogManager logManager =
+			context.mock(PersistentLogManager.class);
+	private final FeatureFlags featureFlags =
+			context.mock(FeatureFlags.class);
 	private final DatabaseConfig databaseConfig =
 			context.mock(DatabaseConfig.class);
 	private final CryptoComponent crypto = context.mock(CryptoComponent.class);
@@ -40,6 +48,7 @@ public class AndroidAccountManagerTest extends BrambleMockTestCase {
 	private final File testDir = getTestDirectory();
 	private final File keyDir = new File(testDir, "key");
 	private final File dbDir = new File(testDir, "db");
+	private final File logDir = new File(testDir, "log");
 
 	private AndroidAccountManager accountManager;
 
@@ -61,7 +70,7 @@ public class AndroidAccountManagerTest extends BrambleMockTestCase {
 			will(returnValue(app));
 		}});
 		accountManager = new AndroidAccountManager(databaseConfig, crypto,
-				identityManager, prefs, app) {
+				identityManager, prefs, logManager, featureFlags, app) {
 			@Override
 			SharedPreferences getDefaultSharedPreferences() {
 				return defaultPrefs;
@@ -109,10 +118,17 @@ public class AndroidAccountManagerTest extends BrambleMockTestCase {
 			will(returnValue(cacheDir));
 			oneOf(app).getExternalCacheDir();
 			will(returnValue(externalCacheDir));
+			oneOf(featureFlags).shouldEnablePersistentLogs();
+			will(returnValue(true));
+			oneOf(app).getDir("log", MODE_PRIVATE);
+			will(returnValue(logDir));
+			oneOf(logManager).addLogHandler(with(logDir),
+					with(any(Logger.class)));
 		}});
 
 		assertTrue(dbDir.mkdirs());
 		assertTrue(keyDir.mkdirs());
+		assertTrue(logDir.mkdirs());
 		assertTrue(codeCacheDir.mkdirs());
 		assertTrue(codeCacheFile.createNewFile());
 		assertTrue(libDir.mkdirs());
@@ -130,6 +146,7 @@ public class AndroidAccountManagerTest extends BrambleMockTestCase {
 
 		assertFalse(dbDir.exists());
 		assertFalse(keyDir.exists());
+		assertFalse(logDir.exists());
 		assertTrue(codeCacheDir.exists());
 		assertTrue(codeCacheFile.exists());
 		assertTrue(libDir.exists());

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

@@ -10,4 +10,6 @@ public interface FeatureFlags {
 	boolean shouldEnableProfilePictures();
 
 	boolean shouldEnableDisappearingMessages();
+
+	boolean shouldEnablePersistentLogs();
 }

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

@@ -1,8 +1,16 @@
 package org.briarproject.bramble.api;
 
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+
 import java.util.Hashtable;
 import java.util.Map;
 
+import javax.annotation.Nullable;
+
+import static org.briarproject.bramble.util.StringUtils.fromHexString;
+import static org.briarproject.bramble.util.StringUtils.toHexString;
+
+@NotNullByDefault
 public abstract class StringMap extends Hashtable<String, String> {
 
 	protected StringMap(Map<String, String> m) {
@@ -52,4 +60,19 @@ public abstract class StringMap extends Hashtable<String, String> {
 	public void putLong(String key, long value) {
 		put(key, String.valueOf(value));
 	}
+
+	@Nullable
+	public byte[] getBytes(String key) {
+		String s = get(key);
+		if (s == null) return null;
+		try {
+			return fromHexString(s);
+		} catch (IllegalArgumentException e) {
+			return null;
+		}
+	}
+
+	public void putBytes(String key, byte[] value) {
+		put(key, toHexString(value));
+	}
 }

bramble-api/src/main/java/org/briarproject/bramble/api/logging/PersistentLogManager.java

@@ -0,0 +1,46 @@
+package org.briarproject.bramble.api.logging;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.settings.Settings;
+
+import java.io.File;
+import java.io.IOException;
+import java.util.Scanner;
+import java.util.logging.Handler;
+import java.util.logging.Logger;
+
+@NotNullByDefault
+public interface PersistentLogManager {
+
+	/**
+	 * The namespace of the (@link Settings) where the log key is stored.
+	 */
+	String LOG_SETTINGS_NAMESPACE = "log";
+
+	/**
+	 * The {@link Settings} key under which the log key is stored.
+	 */
+	String LOG_KEY_KEY = "logKey";
+
+	/**
+	 * Creates and returns a persistent log handler that stores its logs in
+	 * the given directory.
+	 */
+	Handler createLogHandler(File dir) throws IOException;
+
+	/**
+	 * Creates a persistent log handler that stores its logs in the given
+	 * directory and adds the handler to the given logger, replacing any
+	 * existing persistent log handler.
+	 */
+	void addLogHandler(File dir, Logger logger) throws IOException;
+
+	/**
+	 * Returns a {@link Scanner} for reading the persistent log entries stored
+	 * in the given directory.
+	 *
+	 * @param old True if the previous session's log should be loaded, or false
+	 * if the current session's log should be loaded
+	 */
+	Scanner getPersistentLog(File dir, boolean old) throws IOException;
+}

bramble-api/src/main/java/org/briarproject/bramble/api/reporting/DevConfig.java

@@ -8,11 +8,24 @@ import java.io.File;
 @NotNullByDefault
 public interface DevConfig {
 
+	/**
+	 * Returns the public key for encrypting feedback and crash reports.
+	 */
 	PublicKey getDevPublicKey();
 
+	/**
+	 * Returns the onion address for submitting feedback and crash reports.
+	 */
 	String getDevOnionAddress();
 
+	/**
+	 * Returns the directory for storing unsent feedback and crash reports.
+	 */
 	File getReportDir();
 
-	File getLogcatFile();
+	/**
+	 * Returns the temporary file for passing the encrypted app log from the
+	 * main process to the crash reporter process.
+	 */
+	File getTemporaryLogFile();
 }

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

@@ -1,7 +1,10 @@
 package org.briarproject.bramble.util;
 
 import java.io.File;
+import java.util.Collection;
+import java.util.logging.Formatter;
 import java.util.logging.Level;
+import java.util.logging.LogRecord;
 import java.util.logging.Logger;
 
 import static java.util.logging.Level.FINE;
@@ -57,4 +60,13 @@ public class LogUtils {
 			String type) {
 		logger.log(level, type + " " + f.getAbsolutePath() + " " + f.length());
 	}
+
+	public static String formatLog(Formatter formatter,
+			Collection<LogRecord> logRecords) {
+		StringBuilder sb = new StringBuilder();
+		for (LogRecord record : logRecords) {
+			sb.append(formatter.format(record)).append('\n');
+		}
+		return sb.toString();
+	}
 }

bramble-core/src/main/java/org/briarproject/bramble/BrambleCoreModule.java

@@ -14,6 +14,7 @@ import org.briarproject.bramble.identity.IdentityModule;
 import org.briarproject.bramble.io.IoModule;
 import org.briarproject.bramble.keyagreement.KeyAgreementModule;
 import org.briarproject.bramble.lifecycle.LifecycleModule;
+import org.briarproject.bramble.logging.LoggingModule;
 import org.briarproject.bramble.mailbox.MailboxModule;
 import org.briarproject.bramble.plugin.PluginModule;
 import org.briarproject.bramble.properties.PropertiesModule;
@@ -44,6 +45,7 @@ import dagger.Module;
 		IoModule.class,
 		KeyAgreementModule.class,
 		LifecycleModule.class,
+		LoggingModule.class,
 		MailboxModule.class,
 		PluginModule.class,
 		PropertiesModule.class,

bramble-core/src/main/java/org/briarproject/bramble/logging/BriefLogFormatter.java

@@ -1,10 +1,9 @@
-package org.briarproject.briar.android.logging;
+package org.briarproject.bramble.logging;
 
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 
 import java.text.DateFormat;
 import java.text.SimpleDateFormat;
-import java.util.Collection;
 import java.util.Date;
 import java.util.TimeZone;
 import java.util.logging.Formatter;
@@ -18,16 +17,6 @@ import static java.util.Locale.US;
 @NotNullByDefault
 public class BriefLogFormatter extends Formatter {
 
-	public static String formatLog(Formatter formatter,
-			Collection<LogRecord> logRecords) {
-		StringBuilder sb = new StringBuilder();
-		for (LogRecord record : logRecords) {
-			String formatted = formatter.format(record);
-			sb.append(formatted).append('\n');
-		}
-		return sb.toString();
-	}
-
 	private final Object lock = new Object();
 	private final DateFormat dateFormat; // Locking: lock
 	private final Date date; // Locking: lock

bramble-core/src/main/java/org/briarproject/bramble/logging/FlushingStreamHandler.java

@@ -0,0 +1,44 @@
+package org.briarproject.bramble.logging;
+
+import org.briarproject.bramble.api.lifecycle.IoExecutor;
+import org.briarproject.bramble.api.system.TaskScheduler;
+
+import java.io.OutputStream;
+import java.util.concurrent.Executor;
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.logging.Formatter;
+import java.util.logging.LogRecord;
+import java.util.logging.StreamHandler;
+
+import static java.util.concurrent.TimeUnit.MILLISECONDS;
+
+class FlushingStreamHandler extends StreamHandler {
+
+	private static final int FLUSH_DELAY_MS = 5_000;
+
+	private final TaskScheduler scheduler;
+	private final Executor ioExecutor;
+	private final AtomicBoolean flushScheduled = new AtomicBoolean(false);
+
+	FlushingStreamHandler(TaskScheduler scheduler,
+			Executor ioExecutor, OutputStream out, Formatter formatter) {
+		super(out, formatter);
+		this.scheduler = scheduler;
+		this.ioExecutor = ioExecutor;
+	}
+
+	@Override
+	public void publish(LogRecord record) {
+		super.publish(record);
+		if (!flushScheduled.getAndSet(true)) {
+			scheduler.schedule(this::scheduledFlush, ioExecutor,
+					FLUSH_DELAY_MS, MILLISECONDS);
+		}
+	}
+
+	@IoExecutor
+	private void scheduledFlush() {
+		flushScheduled.set(false);
+		flush();
+	}
+}

bramble-core/src/main/java/org/briarproject/bramble/logging/LoggingModule.java

@@ -0,0 +1,29 @@
+package org.briarproject.bramble.logging;
+
+import org.briarproject.bramble.api.lifecycle.LifecycleManager;
+import org.briarproject.bramble.api.logging.PersistentLogManager;
+
+import java.util.logging.Formatter;
+
+import javax.inject.Singleton;
+
+import dagger.Module;
+import dagger.Provides;
+
+@Module
+public class LoggingModule {
+
+	@Provides
+	Formatter provideFormatter() {
+		return new BriefLogFormatter();
+	}
+
+	@Provides
+	@Singleton
+	PersistentLogManager providePersistentLogManager(
+			LifecycleManager lifecycleManager,
+			PersistentLogManagerImpl persistentLogManager) {
+		lifecycleManager.registerOpenDatabaseHook(persistentLogManager);
+		return persistentLogManager;
+	}
+}

bramble-core/src/main/java/org/briarproject/bramble/logging/PersistentLogManagerImpl.java

@@ -0,0 +1,176 @@
+package org.briarproject.bramble.logging;
+
+import org.briarproject.bramble.api.crypto.CryptoComponent;
+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.Transaction;
+import org.briarproject.bramble.api.lifecycle.IoExecutor;
+import org.briarproject.bramble.api.lifecycle.LifecycleManager.OpenDatabaseHook;
+import org.briarproject.bramble.api.lifecycle.ShutdownManager;
+import org.briarproject.bramble.api.logging.PersistentLogManager;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.settings.Settings;
+import org.briarproject.bramble.api.system.TaskScheduler;
+import org.briarproject.bramble.api.transport.StreamReaderFactory;
+import org.briarproject.bramble.api.transport.StreamWriter;
+import org.briarproject.bramble.api.transport.StreamWriterFactory;
+
+import java.io.ByteArrayInputStream;
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+import java.util.Scanner;
+import java.util.concurrent.Executor;
+import java.util.concurrent.atomic.AtomicReference;
+import java.util.logging.Formatter;
+import java.util.logging.Handler;
+import java.util.logging.Logger;
+import java.util.logging.StreamHandler;
+
+import javax.annotation.Nullable;
+import javax.annotation.concurrent.ThreadSafe;
+import javax.inject.Inject;
+
+import static java.util.logging.Level.WARNING;
+import static java.util.logging.Logger.getLogger;
+import static org.briarproject.bramble.util.LogUtils.logException;
+
+@ThreadSafe
+@NotNullByDefault
+class PersistentLogManagerImpl implements PersistentLogManager,
+		OpenDatabaseHook {
+
+	private static final Logger LOG =
+			getLogger(PersistentLogManagerImpl.class.getName());
+
+	private static final String LOG_FILE = "briar.log";
+	private static final String OLD_LOG_FILE = "briar.log.old";
+
+	private final TaskScheduler scheduler;
+	private final Executor ioExecutor;
+	private final ShutdownManager shutdownManager;
+	private final DatabaseComponent db;
+	private final StreamReaderFactory streamReaderFactory;
+	private final StreamWriterFactory streamWriterFactory;
+	private final Formatter formatter;
+	private final SecretKey logKey;
+	private final AtomicReference<Integer> shutdownHookHandle =
+			new AtomicReference<>();
+
+	@Nullable
+	private volatile SecretKey oldLogKey = null;
+
+	@Inject
+	PersistentLogManagerImpl(
+			TaskScheduler scheduler,
+			@IoExecutor Executor ioExecutor,
+			ShutdownManager shutdownManager,
+			DatabaseComponent db,
+			StreamReaderFactory streamReaderFactory,
+			StreamWriterFactory streamWriterFactory,
+			Formatter formatter,
+			CryptoComponent crypto) {
+		this.scheduler = scheduler;
+		this.ioExecutor = ioExecutor;
+		this.shutdownManager = shutdownManager;
+		this.db = db;
+		this.streamReaderFactory = streamReaderFactory;
+		this.streamWriterFactory = streamWriterFactory;
+		this.formatter = formatter;
+		logKey = crypto.generateSecretKey();
+	}
+
+	@Override
+	public void onDatabaseOpened(Transaction txn) throws DbException {
+		Settings s = db.getSettings(txn, LOG_SETTINGS_NAMESPACE);
+		// Load the old log key, if any
+		byte[] oldKeyBytes = s.getBytes(LOG_KEY_KEY);
+		if (oldKeyBytes != null && oldKeyBytes.length == SecretKey.LENGTH) {
+			LOG.info("Loaded old log key");
+			oldLogKey = new SecretKey(oldKeyBytes);
+		}
+		// Store the current log key
+		s.putBytes(LOG_KEY_KEY, logKey.getBytes());
+		db.mergeSettings(txn, s, LOG_SETTINGS_NAMESPACE);
+	}
+
+	@Override
+	public Handler createLogHandler(File dir) throws IOException {
+		File logFile = new File(dir, LOG_FILE);
+		File oldLogFile = new File(dir, OLD_LOG_FILE);
+		if (oldLogFile.exists() && !oldLogFile.delete())
+			LOG.warning("Failed to delete old log file");
+		if (logFile.exists() && !logFile.renameTo(oldLogFile))
+			LOG.warning("Failed to rename log file");
+		try {
+			OutputStream out = new FileOutputStream(logFile);
+			StreamWriter writer =
+					streamWriterFactory.createLogStreamWriter(out, logKey);
+			StreamHandler handler = new FlushingStreamHandler(scheduler,
+					ioExecutor, writer.getOutputStream(), formatter);
+			// Flush the log and terminate the stream at shutdown
+			Runnable shutdownHook = () -> {
+				LOG.info("Shutting down");
+				handler.flush();
+				try {
+					writer.sendEndOfStream();
+				} catch (IOException e) {
+					logException(LOG, WARNING, e);
+				}
+			};
+			int handle = shutdownManager.addShutdownHook(shutdownHook);
+			// If a previous handler registered a shutdown hook, remove it
+			Integer oldHandle = shutdownHookHandle.getAndSet(handle);
+			if (oldHandle != null) {
+				shutdownManager.removeShutdownHook(oldHandle);
+			}
+			return handler;
+		} catch (SecurityException e) {
+			throw new IOException(e);
+		}
+	}
+
+	@Override
+	public void addLogHandler(File dir, Logger logger) throws IOException {
+		for (Handler h : logger.getHandlers()) {
+			if (h instanceof FlushingStreamHandler) logger.removeHandler(h);
+		}
+		logger.addHandler(createLogHandler(dir));
+	}
+
+	@Override
+	public Scanner getPersistentLog(File dir, boolean old)
+			throws IOException {
+		if (old) {
+			SecretKey oldLogKey = this.oldLogKey;
+			if (oldLogKey == null) {
+				LOG.info("Old log key has not been loaded");
+				return emptyScanner();
+			}
+			return getPersistentLog(new File(dir, OLD_LOG_FILE), oldLogKey);
+		} else {
+			return getPersistentLog(new File(dir, LOG_FILE), logKey);
+		}
+	}
+
+	private Scanner getPersistentLog(File logFile, SecretKey key)
+			throws IOException {
+		if (logFile.exists()) {
+			LOG.info("Reading log file");
+			InputStream in = new FileInputStream(logFile);
+			return new Scanner(streamReaderFactory.createLogStreamReader(in,
+					key));
+		} else {
+			LOG.info("Log file does not exist");
+			return emptyScanner();
+		}
+	}
+
+	private Scanner emptyScanner() {
+		return new Scanner(new ByteArrayInputStream(new byte[0]));
+	}
+}

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

@@ -24,6 +24,11 @@ public class TestFeatureFlagModule {
 			public boolean shouldEnableDisappearingMessages() {
 				return true;
 			}
+
+			@Override
+			public boolean shouldEnablePersistentLogs() {
+				return true;
+			}
 		};
 	}
 }

briar-android/src/main/java/org/briarproject/bramble/account/BriarAccountManager.java

@@ -3,9 +3,11 @@ package org.briarproject.bramble.account;
 import android.app.Application;
 import android.content.SharedPreferences;
 
+import org.briarproject.bramble.api.FeatureFlags;
 import org.briarproject.bramble.api.crypto.CryptoComponent;
 import org.briarproject.bramble.api.db.DatabaseConfig;
 import org.briarproject.bramble.api.identity.IdentityManager;
+import org.briarproject.bramble.api.logging.PersistentLogManager;
 import org.briarproject.briar.R;
 import org.briarproject.briar.android.Localizer;
 import org.briarproject.briar.android.util.UiUtils;
@@ -15,10 +17,16 @@ import javax.inject.Inject;
 class BriarAccountManager extends AndroidAccountManager {
 
 	@Inject
-	BriarAccountManager(DatabaseConfig databaseConfig, CryptoComponent crypto,
-			IdentityManager identityManager, SharedPreferences prefs,
+	BriarAccountManager(
+			DatabaseConfig databaseConfig,
+			CryptoComponent crypto,
+			IdentityManager identityManager,
+			SharedPreferences prefs,
+			PersistentLogManager logManager,
+			FeatureFlags featureFlags,
 			Application app) {
-		super(databaseConfig, crypto, identityManager, prefs, app);
+		super(databaseConfig, crypto, identityManager, prefs, logManager,
+				featureFlags, app);
 	}
 
 	@Override

briar-android/src/main/java/org/briarproject/briar/android/AndroidComponent.java

@@ -22,6 +22,7 @@ import org.briarproject.bramble.api.keyagreement.PayloadEncoder;
 import org.briarproject.bramble.api.keyagreement.PayloadParser;
 import org.briarproject.bramble.api.lifecycle.IoExecutor;
 import org.briarproject.bramble.api.lifecycle.LifecycleManager;
+import org.briarproject.bramble.api.logging.PersistentLogManager;
 import org.briarproject.bramble.api.plugin.PluginManager;
 import org.briarproject.bramble.api.settings.SettingsManager;
 import org.briarproject.bramble.api.system.AndroidExecutor;
@@ -78,6 +79,7 @@ import org.briarproject.briar.api.privategroup.invitation.GroupInvitationManager
 import org.briarproject.briar.api.test.TestDataCreator;
 
 import java.util.concurrent.Executor;
+import java.util.logging.Formatter;
 
 import javax.inject.Singleton;
 
@@ -204,6 +206,10 @@ public interface AndroidComponent
 
 	AutoDeleteManager autoDeleteManager();
 
+	PersistentLogManager persistentLogManager();
+
+	Formatter formatter();
+
 	void inject(SignInReminderReceiver briarService);
 
 	void inject(BriarService briarService);

briar-android/src/main/java/org/briarproject/briar/android/AppModule.java

@@ -245,8 +245,9 @@ public class AppModule {
 			}
 
 			@Override
-			public File getLogcatFile() {
-				return AndroidUtils.getLogcatFile(app.getApplicationContext());
+			public File getTemporaryLogFile() {
+				return AndroidUtils
+						.getTemporaryLogFile(app.getApplicationContext());
 			}
 		};
 		return devConfig;
@@ -337,6 +338,11 @@ public class AppModule {
 			public boolean shouldEnableDisappearingMessages() {
 				return true;
 			}
+
+			@Override
+			public boolean shouldEnablePersistentLogs() {
+				return IS_DEBUG_BUILD;
+			}
 		};
 	}
 }

briar-android/src/main/java/org/briarproject/briar/android/BriarApplicationImpl.java

@@ -17,11 +17,14 @@ import com.vanniktech.emoji.google.GoogleEmojiProvider;
 import org.briarproject.bramble.BrambleAndroidEagerSingletons;
 import org.briarproject.bramble.BrambleAppComponent;
 import org.briarproject.bramble.BrambleCoreEagerSingletons;
+import org.briarproject.bramble.api.logging.PersistentLogManager;
 import org.briarproject.briar.BriarCoreEagerSingletons;
 import org.briarproject.briar.R;
 import org.briarproject.briar.android.logging.CachingLogHandler;
 import org.briarproject.briar.android.util.UiUtils;
 
+import java.io.File;
+import java.io.IOException;
 import java.lang.Thread.UncaughtExceptionHandler;
 import java.util.logging.Handler;
 import java.util.logging.Logger;
@@ -31,7 +34,10 @@ import androidx.annotation.NonNull;
 import static android.app.ActivityManager.RunningAppProcessInfo.IMPORTANCE_FOREGROUND;
 import static java.util.logging.Level.FINE;
 import static java.util.logging.Level.INFO;
+import static java.util.logging.Level.WARNING;
 import static java.util.logging.Logger.getLogger;
+import static org.briarproject.bramble.util.AndroidUtils.getPersistentLogDir;
+import static org.briarproject.bramble.util.LogUtils.logException;
 import static org.briarproject.briar.android.TestingConstants.IS_DEBUG_BUILD;
 
 public class BriarApplicationImpl extends Application
@@ -81,6 +87,17 @@ public class BriarApplicationImpl extends Application
 		rootLogger.addHandler(logHandler);
 		rootLogger.setLevel(IS_DEBUG_BUILD ? FINE : INFO);
 
+		if (applicationComponent.featureFlags().shouldEnablePersistentLogs()) {
+			PersistentLogManager logManager =
+					applicationComponent.persistentLogManager();
+			File logDir = getPersistentLogDir(this);
+			try {
+				rootLogger.addHandler(logManager.createLogHandler(logDir));
+			} catch (IOException e) {
+				logException(LOG, WARNING, e);
+			}
+		}
+
 		LOG.info("Created");
 
 		EmojiManager.install(new GoogleEmojiProvider());

briar-android/src/main/java/org/briarproject/briar/android/logging/LogDecrypter.java

@@ -8,8 +8,9 @@ import androidx.annotation.Nullable;
 @NotNullByDefault
 public interface LogDecrypter {
 	/**
-	 * Returns decrypted log records from {@link AndroidUtils#getLogcatFile}
-	 * or null if there was an error reading the logs.
+	 * Returns decrypted log records from
+	 * {@link AndroidUtils#getTemporaryLogFile} or null if there was an error
+	 * reading the logs.
 	 */
 	@Nullable
 	String decryptLogs(@Nullable byte[] logKey);

briar-android/src/main/java/org/briarproject/briar/android/logging/LogDecrypterImpl.java

@@ -41,7 +41,7 @@ class LogDecrypterImpl implements LogDecrypter {
 	public String decryptLogs(@Nullable byte[] logKey) {
 		if (logKey == null) return null;
 		SecretKey key = new SecretKey(logKey);
-		File logFile = devConfig.getLogcatFile();
+		File logFile = devConfig.getTemporaryLogFile();
 		try (InputStream in = new FileInputStream(logFile)) {
 			InputStream reader =
 					streamReaderFactory.createLogStreamReader(in, key);

briar-android/src/main/java/org/briarproject/briar/android/logging/LogEncrypter.java

@@ -8,7 +8,7 @@ import androidx.annotation.Nullable;
 @NotNullByDefault
 public interface LogEncrypter {
 	/**
-	 * Writes encrypted log records to {@link AndroidUtils#getLogcatFile}
+	 * Writes encrypted log records to {@link AndroidUtils#getTemporaryLogFile}
 	 * and returns the encryption key if everything went fine.
 	 */
 	@Nullable

briar-android/src/main/java/org/briarproject/briar/android/logging/LogEncrypterImpl.java

@@ -33,16 +33,19 @@ class LogEncrypterImpl implements LogEncrypter {
 
 	private final DevConfig devConfig;
 	private final CachingLogHandler logHandler;
+	private final Formatter formatter;
 	private final CryptoComponent crypto;
 	private final StreamWriterFactory streamWriterFactory;
 
 	@Inject
 	LogEncrypterImpl(DevConfig devConfig,
 			CachingLogHandler logHandler,
+			Formatter formatter,
 			CryptoComponent crypto,
 			StreamWriterFactory streamWriterFactory) {
 		this.devConfig = devConfig;
 		this.logHandler = logHandler;
+		this.formatter = formatter;
 		this.crypto = crypto;
 		this.streamWriterFactory = streamWriterFactory;
 	}
@@ -51,7 +54,7 @@ class LogEncrypterImpl implements LogEncrypter {
 	@Override
 	public byte[] encryptLogs() {
 		SecretKey logKey = crypto.generateSecretKey();
-		File logFile = devConfig.getLogcatFile();
+		File logFile = devConfig.getTemporaryLogFile();
 		try (OutputStream out = new FileOutputStream(logFile)) {
 			StreamWriter streamWriter =
 					streamWriterFactory.createLogStreamWriter(out, logKey);
@@ -67,10 +70,8 @@ class LogEncrypterImpl implements LogEncrypter {
 	}
 
 	private void writeLogString(Writer writer) throws IOException {
-		Formatter formatter = new BriefLogFormatter();
 		for (LogRecord record : logHandler.getRecentLogRecords()) {
-			String formatted = formatter.format(record);
-			writer.append(formatted).append('\n');
+			writer.append(formatter.format(record)).append('\n');
 		}
 	}
 

briar-android/src/main/java/org/briarproject/briar/android/reporting/BriarReportCollector.java

@@ -26,6 +26,7 @@ import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.briar.BuildConfig;
 import org.briarproject.briar.R;
 import org.briarproject.briar.android.reporting.ReportData.MultiReportInfo;
+import org.briarproject.briar.android.reporting.ReportData.ReportInfo;
 import org.briarproject.briar.android.reporting.ReportData.ReportItem;
 import org.briarproject.briar.android.reporting.ReportData.SingleReportInfo;
 
@@ -71,7 +72,7 @@ class BriarReportCollector {
 	}
 
 	ReportData collectReportData(@Nullable Throwable t, long appStartTime,
-			String logs) {
+			ReportInfo logs) {
 		ReportData reportData = new ReportData()
 				.add(getBasicInfo(t))
 				.add(getDeviceInfo());
@@ -82,7 +83,7 @@ class BriarReportCollector {
 				.add(getStorage())
 				.add(getConnectivity())
 				.add(getBuildConfig())
-				.add(getLogcat(logs))
+				.add(getLogs(logs))
 				.add(getDeviceFeatures());
 	}
 
@@ -309,8 +310,8 @@ class BriarReportCollector {
 				buildConfig);
 	}
 
-	private ReportItem getLogcat(String logs) {
-		return new ReportItem("Logcat", R.string.dev_report_logcat, logs);
+	private ReportItem getLogs(ReportInfo logs) {
+		return new ReportItem("Logs", R.string.dev_report_logcat, logs);
 	}
 
 	private ReportItem getDeviceFeatures() {

briar-android/src/main/java/org/briarproject/briar/android/reporting/ReportViewModel.java

@@ -4,6 +4,8 @@ import android.app.Application;
 import android.os.Handler;
 import android.os.Looper;
 
+import org.briarproject.bramble.api.FeatureFlags;
+import org.briarproject.bramble.api.logging.PersistentLogManager;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.plugin.Plugin;
 import org.briarproject.bramble.api.plugin.PluginManager;
@@ -11,7 +13,6 @@ import org.briarproject.bramble.api.plugin.TorConstants;
 import org.briarproject.bramble.api.reporting.DevReporter;
 import org.briarproject.bramble.util.AndroidUtils;
 import org.briarproject.briar.R;
-import org.briarproject.briar.android.logging.BriefLogFormatter;
 import org.briarproject.briar.android.logging.CachingLogHandler;
 import org.briarproject.briar.android.logging.LogDecrypter;
 import org.briarproject.briar.android.reporting.ReportData.MultiReportInfo;
@@ -22,6 +23,9 @@ import org.json.JSONException;
 
 import java.io.File;
 import java.io.FileNotFoundException;
+import java.io.IOException;
+import java.util.LinkedList;
+import java.util.Scanner;
 import java.util.UUID;
 import java.util.logging.Formatter;
 import java.util.logging.Logger;
@@ -39,18 +43,24 @@ import static java.util.Objects.requireNonNull;
 import static java.util.logging.Level.WARNING;
 import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.api.plugin.Plugin.State.ACTIVE;
+import static org.briarproject.bramble.util.AndroidUtils.getPersistentLogDir;
+import static org.briarproject.bramble.util.LogUtils.formatLog;
 import static org.briarproject.bramble.util.LogUtils.logException;
 import static org.briarproject.bramble.util.StringUtils.isNullOrEmpty;
-import static org.briarproject.briar.android.logging.BriefLogFormatter.formatLog;
 
 @NotNullByDefault
 class ReportViewModel extends AndroidViewModel {
 
+	private static final int MAX_PERSISTENT_LOG_LINES = 1000;
+
 	private static final Logger LOG =
 			getLogger(ReportViewModel.class.getName());
 
 	private final CachingLogHandler logHandler;
 	private final LogDecrypter logDecrypter;
+	private final Formatter formatter;
+	private final PersistentLogManager logManager;
+	private final FeatureFlags featureFlags;
 	private final BriarReportCollector collector;
 	private final DevReporter reporter;
 	private final PluginManager pluginManager;
@@ -71,12 +81,18 @@ class ReportViewModel extends AndroidViewModel {
 	ReportViewModel(@NonNull Application application,
 			CachingLogHandler logHandler,
 			LogDecrypter logDecrypter,
+			Formatter formatter,
+			PersistentLogManager logManager,
+			FeatureFlags featureFlags,
 			DevReporter reporter,
 			PluginManager pluginManager) {
 		super(application);
 		collector = new BriarReportCollector(application);
 		this.logHandler = logHandler;
 		this.logDecrypter = logDecrypter;
+		this.formatter = formatter;
+		this.logManager = logManager;
+		this.featureFlags = featureFlags;
 		this.reporter = reporter;
 		this.pluginManager = pluginManager;
 	}
@@ -86,22 +102,30 @@ class ReportViewModel extends AndroidViewModel {
 		this.initialComment = initialComment;
 		isFeedback = t == null;
 		if (reportData.getValue() == null) new SingleShotAndroidExecutor(() -> {
-			String decryptedLogs;
+			String currentLog;
 			if (isFeedback) {
-				Formatter formatter = new BriefLogFormatter();
-				decryptedLogs =
-						formatLog(formatter, logHandler.getRecentLogRecords());
+				// We're in the main process, so get the log for this process
+				currentLog = formatLog(formatter,
+						logHandler.getRecentLogRecords());
 			} else {
-				decryptedLogs = logDecrypter.decryptLogs(logKey);
-				if (decryptedLogs == null) {
+				// We're in the crash reporter process, so try to load
+				// the encrypted log that was saved by the main process
+				currentLog = logDecrypter.decryptLogs(logKey);
+				if (currentLog == null) {
 					// error decrypting logs, get logs from this process
-					Formatter formatter = new BriefLogFormatter();
-					decryptedLogs = formatLog(formatter,
+					currentLog = formatLog(formatter,
 							logHandler.getRecentLogRecords());
 				}
 			}
+			MultiReportInfo logs = new MultiReportInfo();
+			logs.add("Current", currentLog);
+			if (isFeedback && featureFlags.shouldEnablePersistentLogs()) {
+				// Add persistent logs for the current and previous processes
+				logs.add("Persistent", getPersistentLog(false));
+				logs.add("PersistentOld", getPersistentLog(true));
+			}
 			ReportData data =
-					collector.collectReportData(t, appStartTime, decryptedLogs);
+					collector.collectReportData(t, appStartTime, logs);
 			reportData.postValue(data);
 		}).start();
 	}
@@ -226,6 +250,27 @@ class ReportViewModel extends AndroidViewModel {
 		return closeReport;
 	}
 
+	private String getPersistentLog(boolean old) {
+		File logDir = getPersistentLogDir(getApplication());
+		StringBuilder sb = new StringBuilder();
+		try {
+			Scanner scanner = logManager.getPersistentLog(logDir, old);
+			LinkedList<String> lines = new LinkedList<>();
+			int numLines = 0;
+			while (scanner.hasNextLine()) {
+				lines.add(scanner.nextLine());
+				// If there are too many lines, return the most recent ones
+				if (numLines == MAX_PERSISTENT_LOG_LINES) lines.pollFirst();
+				else numLines++;
+			}
+			scanner.close();
+			for (String line : lines) sb.append(line).append('\n');
+		} catch (IOException e) {
+			sb.append("Could not recover persistent log: ").append(e);
+		}
+		return sb.toString();
+	}
+
 	// Used for a new thread as the Android executor thread may have died
 	private static class SingleShotAndroidExecutor extends Thread {
 

briar-android/src/main/java/org/briarproject/briar/android/settings/SettingsFragment.java

@@ -8,6 +8,7 @@ import android.view.View;
 import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
 import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
 import org.briarproject.briar.R;
+import org.briarproject.briar.android.util.ActivityLaunchers.CreateDocumentAdvanced;
 import org.briarproject.briar.android.util.ActivityLaunchers.GetImageAdvanced;
 
 import javax.inject.Inject;
@@ -21,6 +22,7 @@ import androidx.preference.Preference;
 import androidx.preference.PreferenceFragmentCompat;
 import androidx.preference.PreferenceGroup;
 
+import static android.os.Build.VERSION.SDK_INT;
 import static java.util.Objects.requireNonNull;
 import static org.briarproject.briar.android.AppModule.getAndroidComponent;
 import static org.briarproject.briar.android.TestingConstants.IS_DEBUG_BUILD;
@@ -37,6 +39,10 @@ public class SettingsFragment extends PreferenceFragmentCompat {
 	private static final String PREF_KEY_DEV = "pref_key_dev";
 	private static final String PREF_KEY_EXPLODE = "pref_key_explode";
 	private static final String PREF_KEY_SHARE_APP = "pref_key_share_app";
+	private static final String PREF_KEY_EXPORT_LOG = "pref_key_export_log";
+	private static final String PREF_EXPORT_OLD_LOG = "pref_key_export_old_log";
+
+	private static final String LOG_EXPORT_FILENAME = "briar-log.txt";
 
 	@Inject
 	ViewModelProvider.Factory viewModelFactory;
@@ -44,10 +50,18 @@ public class SettingsFragment extends PreferenceFragmentCompat {
 	private SettingsViewModel viewModel;
 	private AvatarPreference prefAvatar;
 
-	private final ActivityResultLauncher<String> launcher =
+	private final ActivityResultLauncher<String> imageLauncher =
 			registerForActivityResult(new GetImageAdvanced(),
 					this::onImageSelected);
 
+	private final ActivityResultLauncher<String> logLauncher =
+			registerForActivityResult(new CreateDocumentAdvanced(),
+					uri -> onLogFileSelected(false, uri));
+
+	private final ActivityResultLauncher<String> oldLogLauncher =
+			registerForActivityResult(new CreateDocumentAdvanced(),
+					uri -> onLogFileSelected(true, uri));
+
 	@Override
 	public void onAttach(@NonNull Context context) {
 		super.onAttach(context);
@@ -63,7 +77,7 @@ public class SettingsFragment extends PreferenceFragmentCompat {
 		prefAvatar = requireNonNull(findPreference(PREF_KEY_AVATAR));
 		if (viewModel.shouldEnableProfilePictures()) {
 			prefAvatar.setOnPreferenceClickListener(preference -> {
-				launcher.launch("image/*");
+				imageLauncher.launch("image/*");
 				return true;
 			});
 		} else {
@@ -77,11 +91,32 @@ public class SettingsFragment extends PreferenceFragmentCompat {
 			return true;
 		});
 
-		Preference explode = requireNonNull(findPreference(PREF_KEY_EXPLODE));
 		if (IS_DEBUG_BUILD) {
+			Preference explode =
+					requireNonNull(findPreference(PREF_KEY_EXPLODE));
 			explode.setOnPreferenceClickListener(preference -> {
 				throw new RuntimeException("Boom!");
 			});
+			Preference exportLog =
+					requireNonNull(findPreference(PREF_KEY_EXPORT_LOG));
+			if (SDK_INT >= 19) {
+				exportLog.setOnPreferenceClickListener(preference -> {
+					logLauncher.launch(LOG_EXPORT_FILENAME);
+					return true;
+				});
+			} else {
+				exportLog.setVisible(false);
+			}
+			Preference exportOldLog =
+					requireNonNull(findPreference(PREF_EXPORT_OLD_LOG));
+			if (SDK_INT >= 19) {
+				exportOldLog.setOnPreferenceClickListener(preference -> {
+					oldLogLauncher.launch(LOG_EXPORT_FILENAME);
+					return true;
+				});
+			} else {
+				exportOldLog.setVisible(false);
+			}
 		} else {
 			PreferenceGroup dev = requireNonNull(findPreference(PREF_KEY_DEV));
 			dev.setVisible(false);
@@ -111,4 +146,7 @@ public class SettingsFragment extends PreferenceFragmentCompat {
 				ConfirmAvatarDialogFragment.TAG);
 	}
 
+	private void onLogFileSelected(boolean old, @Nullable Uri uri) {
+		if (uri != null) viewModel.exportPersistentLog(old, uri);
+	}
 }

briar-android/src/main/java/org/briarproject/briar/android/settings/SettingsViewModel.java

@@ -16,6 +16,7 @@ import org.briarproject.bramble.api.identity.IdentityManager;
 import org.briarproject.bramble.api.identity.LocalAuthor;
 import org.briarproject.bramble.api.lifecycle.IoExecutor;
 import org.briarproject.bramble.api.lifecycle.LifecycleManager;
+import org.briarproject.bramble.api.logging.PersistentLogManager;
 import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
 import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
 import org.briarproject.bramble.api.plugin.BluetoothConstants;
@@ -35,8 +36,12 @@ import org.briarproject.briar.api.avatar.AvatarManager;
 import org.briarproject.briar.api.identity.AuthorInfo;
 import org.briarproject.briar.api.identity.AuthorManager;
 
+import java.io.File;
 import java.io.IOException;
 import java.io.InputStream;
+import java.io.OutputStream;
+import java.io.PrintWriter;
+import java.util.Scanner;
 import java.util.concurrent.Executor;
 import java.util.logging.Logger;
 
@@ -50,6 +55,7 @@ import static android.widget.Toast.LENGTH_LONG;
 import static java.util.Arrays.asList;
 import static java.util.logging.Level.WARNING;
 import static java.util.logging.Logger.getLogger;
+import static org.briarproject.bramble.util.AndroidUtils.getPersistentLogDir;
 import static org.briarproject.bramble.util.AndroidUtils.getSupportedImageContentTypes;
 import static org.briarproject.bramble.util.LogUtils.logDuration;
 import static org.briarproject.bramble.util.LogUtils.logException;
@@ -78,6 +84,7 @@ class SettingsViewModel extends DbViewModel implements EventListener {
 	private final ImageCompressor imageCompressor;
 	private final Executor ioExecutor;
 	private final FeatureFlags featureFlags;
+	private final PersistentLogManager logManager;
 
 	final SettingsStore settingsStore;
 	final TorSummaryProvider torSummaryProvider;
@@ -108,7 +115,8 @@ class SettingsViewModel extends DbViewModel implements EventListener {
 			LocationUtils locationUtils,
 			CircumventionProvider circumventionProvider,
 			@IoExecutor Executor ioExecutor,
-			FeatureFlags featureFlags) {
+			FeatureFlags featureFlags,
+			PersistentLogManager logManager) {
 		super(application, dbExecutor, lifecycleManager, db, androidExecutor);
 		this.settingsManager = settingsManager;
 		this.identityManager = identityManager;
@@ -118,6 +126,7 @@ class SettingsViewModel extends DbViewModel implements EventListener {
 		this.authorManager = authorManager;
 		this.ioExecutor = ioExecutor;
 		this.featureFlags = featureFlags;
+		this.logManager = logManager;
 		settingsStore = new SettingsStore(settingsManager, dbExecutor,
 				SETTINGS_NAMESPACE);
 		torSummaryProvider = new TorSummaryProvider(getApplication(),
@@ -262,4 +271,38 @@ class SettingsViewModel extends DbViewModel implements EventListener {
 		return screenLockTimeout;
 	}
 
+	void exportPersistentLog(boolean old, Uri uri) {
+		// We can use untranslated strings here, as this method is only called
+		// in debug builds
+		ioExecutor.execute(() -> {
+			Application app = getApplication();
+			try {
+				OutputStream os =
+						app.getContentResolver().openOutputStream(uri);
+				if (os == null) throw new IOException();
+				File logDir = getPersistentLogDir(app);
+				Scanner scanner = logManager.getPersistentLog(logDir, old);
+				if (!scanner.hasNextLine()) {
+					scanner.close();
+					androidExecutor.runOnUiThread(() ->
+							Toast.makeText(app, "Log is empty",
+									LENGTH_LONG).show());
+					return;
+				}
+				PrintWriter w = new PrintWriter(os);
+				while (scanner.hasNextLine()) w.println(scanner.nextLine());
+				w.flush();
+				w.close();
+				scanner.close();
+				androidExecutor.runOnUiThread(() ->
+						Toast.makeText(app, "Log exported",
+								LENGTH_LONG).show());
+			} catch (IOException e) {
+				logException(LOG, WARNING, e);
+				androidExecutor.runOnUiThread(() ->
+						Toast.makeText(app, "Failed to export log",
+								LENGTH_LONG).show());
+			}
+		});
+	}
 }

briar-android/src/main/res/xml/settings.xml

@@ -58,6 +58,14 @@
 				android:targetPackage="@string/app_package" />
 		</Preference>
 
+		<Preference
+			android:key="pref_key_export_log"
+			android:title="Export current log to SD card" />
+
+		<Preference
+			android:key="pref_key_export_old_log"
+			android:title="Export previous log to SD card" />
+
 		<Preference
 			android:key="pref_key_explode"
 			android:title="Crash" />

briar-android/src/test/java/org/briarproject/briar/android/logging/LogEncryptionDecryptionTest.java

@@ -1,5 +1,6 @@
 package org.briarproject.briar.android.logging;
 
+import org.briarproject.bramble.logging.BriefLogFormatter;
 import org.briarproject.bramble.test.BrambleMockTestCase;
 import org.junit.ClassRule;
 import org.junit.Test;
@@ -15,8 +16,8 @@ import static java.util.logging.Level.FINE;
 import static java.util.logging.Level.INFO;
 import static java.util.logging.Level.SEVERE;
 import static java.util.logging.Level.WARNING;
+import static org.briarproject.bramble.util.LogUtils.formatLog;
 import static org.briarproject.bramble.util.StringUtils.getRandomString;
-import static org.briarproject.briar.android.logging.BriefLogFormatter.formatLog;
 import static org.junit.Assert.assertEquals;
 
 public class LogEncryptionDecryptionTest extends BrambleMockTestCase {

briar-android/src/test/java/org/briarproject/briar/android/logging/LoggingTestModule.java

@@ -42,7 +42,7 @@ class LoggingTestModule {
 			}
 
 			@Override
-			public File getLogcatFile() {
+			public File getTemporaryLogFile() {
 				return logFile;
 			}
 		};

briar-headless/src/main/java/org/briarproject/briar/headless/HeadlessModule.kt

@@ -107,5 +107,6 @@ internal class HeadlessModule(private val appDir: File) {
         override fun shouldEnableImageAttachments() = false
         override fun shouldEnableProfilePictures() = false
         override fun shouldEnableDisappearingMessages() = false
+        override fun shouldEnablePersistentLogs() = false
     }
 }