Add initial API for rendezvous plugins.

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

@@ -5,7 +5,7 @@ import org.briarproject.bramble.api.data.BdfList;
 import java.io.IOException;
 
 /**
- * An class for managing a particular key agreement listener.
+ * Accepts key agreement connections over a given transport.
  */
 public abstract class KeyAgreementListener {
 

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

@@ -36,4 +36,9 @@ public interface PluginManager {
 	 * Returns any duplex plugins that support key agreement.
 	 */
 	Collection<DuplexPlugin> getKeyAgreementPlugins();
+
+	/**
+	 * Returns any duplex plugins that support rendezvous.
+	 */
+	Collection<DuplexPlugin> getRendezvousPlugins();
 }

bramble-api/src/main/java/org/briarproject/bramble/api/plugin/duplex/DuplexPlugin.java

@@ -5,6 +5,8 @@ import org.briarproject.bramble.api.keyagreement.KeyAgreementListener;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.plugin.Plugin;
 import org.briarproject.bramble.api.properties.TransportProperties;
+import org.briarproject.bramble.api.rendezvous.KeyMaterialSource;
+import org.briarproject.bramble.api.rendezvous.RendezvousHandler;
 
 import javax.annotation.Nullable;
 
@@ -40,4 +42,15 @@ public interface DuplexPlugin extends Plugin {
 	@Nullable
 	DuplexTransportConnection createKeyAgreementConnection(
 			byte[] remoteCommitment, BdfList descriptor);
+
+	/**
+	 * Returns true if the plugin supports rendezvous connections.
+	 */
+	boolean supportsRendezvous();
+
+	/**
+	 * Creates and returns a handler that uses the given key material to
+	 * rendezvous with a pending contact.
+	 */
+	RendezvousHandler createRendezvousHandler(KeyMaterialSource k);
 }

bramble-api/src/main/java/org/briarproject/bramble/api/rendezvous/KeyMaterialSource.java

@@ -0,0 +1,15 @@
+package org.briarproject.bramble.api.rendezvous;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+
+/**
+ * A source of key material for use in making rendezvous connections.
+ */
+@NotNullByDefault
+public interface KeyMaterialSource {
+
+	/**
+	 * Returns the requested amount of key material.
+	 */
+	byte[] getKeyMaterial(int length);
+}

bramble-api/src/main/java/org/briarproject/bramble/api/rendezvous/RendezvousConstants.java

@@ -0,0 +1,10 @@
+package org.briarproject.bramble.api.rendezvous;
+
+public interface RendezvousConstants {
+
+	/**
+	 * Label for deriving key material from the master key.
+	 */
+	String KEY_MATERIAL_LABEL =
+			"org.briarproject.bramble.rendezvous/KEY_MATERIAL";
+}

bramble-api/src/main/java/org/briarproject/bramble/api/rendezvous/RendezvousCrypto.java

@@ -0,0 +1,12 @@
+package org.briarproject.bramble.api.rendezvous;
+
+import org.briarproject.bramble.api.crypto.SecretKey;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.plugin.TransportId;
+
+@NotNullByDefault
+public interface RendezvousCrypto {
+
+	KeyMaterialSource createKeyMaterialSource(SecretKey masterKey,
+			TransportId t);
+}

bramble-api/src/main/java/org/briarproject/bramble/api/rendezvous/RendezvousHandler.java

@@ -0,0 +1,24 @@
+package org.briarproject.bramble.api.rendezvous;
+
+import org.briarproject.bramble.api.properties.TransportProperties;
+
+import java.io.IOException;
+
+/**
+ * An interface for making and accepting rendezvous connections with a pending
+ * contact over a given transport.
+ */
+public interface RendezvousHandler {
+
+	/**
+	 * Returns a set of transport properties for connecting to the pending
+	 * contact.
+	 */
+	TransportProperties getRemoteTransportProperties();
+
+	/**
+	 * Closes the handler and releases any resources held by it, such as
+	 * network sockets.
+	 */
+	void close() throws IOException;
+}

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

@@ -15,6 +15,7 @@ import org.briarproject.bramble.plugin.PluginModule;
 import org.briarproject.bramble.properties.PropertiesModule;
 import org.briarproject.bramble.record.RecordModule;
 import org.briarproject.bramble.reliability.ReliabilityModule;
+import org.briarproject.bramble.rendezvous.RendezvousModule;
 import org.briarproject.bramble.reporting.ReportingModule;
 import org.briarproject.bramble.settings.SettingsModule;
 import org.briarproject.bramble.socks.SocksModule;
@@ -42,6 +43,7 @@ import dagger.Module;
 		PropertiesModule.class,
 		RecordModule.class,
 		ReliabilityModule.class,
+		RendezvousModule.class,
 		ReportingModule.class,
 		SettingsModule.class,
 		SocksModule.class,

bramble-core/src/main/java/org/briarproject/bramble/plugin/PluginManagerImpl.java

@@ -169,6 +169,14 @@ class PluginManagerImpl implements PluginManager, Service {
 		return supported;
 	}
 
+	@Override
+	public Collection<DuplexPlugin> getRendezvousPlugins() {
+		List<DuplexPlugin> supported = new ArrayList<>();
+		for (DuplexPlugin d : duplexPlugins)
+			if (d.supportsRendezvous()) supported.add(d);
+		return supported;
+	}
+
 	private class PluginStarter implements Runnable {
 
 		private final Plugin plugin;

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

@@ -22,6 +22,8 @@ import org.briarproject.bramble.api.plugin.event.BluetoothEnabledEvent;
 import org.briarproject.bramble.api.plugin.event.DisableBluetoothEvent;
 import org.briarproject.bramble.api.plugin.event.EnableBluetoothEvent;
 import org.briarproject.bramble.api.properties.TransportProperties;
+import org.briarproject.bramble.api.rendezvous.KeyMaterialSource;
+import org.briarproject.bramble.api.rendezvous.RendezvousHandler;
 import org.briarproject.bramble.api.settings.Settings;
 import org.briarproject.bramble.api.settings.event.SettingsUpdatedEvent;
 
@@ -390,6 +392,16 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 		return macToString(mac);
 	}
 
+	@Override
+	public boolean supportsRendezvous() {
+		return false;
+	}
+
+	@Override
+	public RendezvousHandler createRendezvousHandler(KeyMaterialSource k) {
+		throw new UnsupportedOperationException();
+	}
+
 	@Override
 	public void eventOccurred(Event e) {
 		if (e instanceof EnableBluetoothEvent) {

bramble-core/src/main/java/org/briarproject/bramble/plugin/tcp/TcpPlugin.java

@@ -12,6 +12,8 @@ import org.briarproject.bramble.api.plugin.PluginCallback;
 import org.briarproject.bramble.api.plugin.duplex.DuplexPlugin;
 import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
 import org.briarproject.bramble.api.properties.TransportProperties;
+import org.briarproject.bramble.api.rendezvous.KeyMaterialSource;
+import org.briarproject.bramble.api.rendezvous.RendezvousHandler;
 import org.briarproject.bramble.util.IoUtils;
 
 import java.io.IOException;
@@ -301,6 +303,16 @@ abstract class TcpPlugin implements DuplexPlugin {
 		throw new UnsupportedOperationException();
 	}
 
+	@Override
+	public boolean supportsRendezvous() {
+		return false;
+	}
+
+	@Override
+	public RendezvousHandler createRendezvousHandler(KeyMaterialSource k) {
+		throw new UnsupportedOperationException();
+	}
+
 	Collection<InetAddress> getLocalIpAddresses() {
 		try {
 			Enumeration<NetworkInterface> ifaces = getNetworkInterfaces();

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

@@ -25,6 +25,8 @@ import org.briarproject.bramble.api.plugin.TransportId;
 import org.briarproject.bramble.api.plugin.duplex.DuplexPlugin;
 import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
 import org.briarproject.bramble.api.properties.TransportProperties;
+import org.briarproject.bramble.api.rendezvous.KeyMaterialSource;
+import org.briarproject.bramble.api.rendezvous.RendezvousHandler;
 import org.briarproject.bramble.api.settings.Settings;
 import org.briarproject.bramble.api.settings.event.SettingsUpdatedEvent;
 import org.briarproject.bramble.api.system.Clock;
@@ -605,6 +607,16 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 		throw new UnsupportedOperationException();
 	}
 
+	@Override
+	public boolean supportsRendezvous() {
+		return false;
+	}
+
+	@Override
+	public RendezvousHandler createRendezvousHandler(KeyMaterialSource k) {
+		throw new UnsupportedOperationException();
+	}
+
 	@Override
 	public void circuitStatus(String status, String id, String path) {
 		if (status.equals("BUILT") &&

bramble-core/src/main/java/org/briarproject/bramble/rendezvous/KeyMaterialSourceImpl.java

@@ -0,0 +1,33 @@
+package org.briarproject.bramble.rendezvous;
+
+import org.briarproject.bramble.api.crypto.SecretKey;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.rendezvous.KeyMaterialSource;
+import org.spongycastle.crypto.engines.Salsa20Engine;
+import org.spongycastle.crypto.params.KeyParameter;
+import org.spongycastle.crypto.params.ParametersWithIV;
+
+import javax.annotation.concurrent.GuardedBy;
+import javax.annotation.concurrent.ThreadSafe;
+
+@ThreadSafe
+@NotNullByDefault
+class KeyMaterialSourceImpl implements KeyMaterialSource {
+
+	@GuardedBy("this")
+	private final Salsa20Engine cipher = new Salsa20Engine();
+
+	KeyMaterialSourceImpl(SecretKey sourceKey) {
+		// Initialise the stream cipher with an all-zero nonce
+		KeyParameter k = new KeyParameter(sourceKey.getBytes());
+		cipher.init(true, new ParametersWithIV(k, new byte[8]));
+	}
+
+	@Override
+	public synchronized byte[] getKeyMaterial(int length) {
+		byte[] in = new byte[length];
+		byte[] out = new byte[length];
+		cipher.processBytes(in, 0, length, out, 0);
+		return out;
+	}
+}

bramble-core/src/main/java/org/briarproject/bramble/rendezvous/RendezvousCryptoImpl.java

@@ -0,0 +1,34 @@
+package org.briarproject.bramble.rendezvous;
+
+import org.briarproject.bramble.api.crypto.CryptoComponent;
+import org.briarproject.bramble.api.crypto.SecretKey;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.plugin.TransportId;
+import org.briarproject.bramble.api.rendezvous.KeyMaterialSource;
+import org.briarproject.bramble.api.rendezvous.RendezvousCrypto;
+
+import javax.annotation.concurrent.Immutable;
+import javax.inject.Inject;
+
+import static org.briarproject.bramble.api.rendezvous.RendezvousConstants.KEY_MATERIAL_LABEL;
+import static org.briarproject.bramble.util.StringUtils.toUtf8;
+
+@Immutable
+@NotNullByDefault
+class RendezvousCryptoImpl implements RendezvousCrypto {
+
+	private final CryptoComponent crypto;
+
+	@Inject
+	RendezvousCryptoImpl(CryptoComponent crypto) {
+		this.crypto = crypto;
+	}
+
+	@Override
+	public KeyMaterialSource createKeyMaterialSource(SecretKey masterKey,
+			TransportId t) {
+		SecretKey sourceKey = crypto.deriveKey(KEY_MATERIAL_LABEL, masterKey,
+				toUtf8(t.getString()));
+		return new KeyMaterialSourceImpl(sourceKey);
+	}
+}

bramble-core/src/main/java/org/briarproject/bramble/rendezvous/RendezvousModule.java

@@ -0,0 +1,16 @@
+package org.briarproject.bramble.rendezvous;
+
+import org.briarproject.bramble.api.rendezvous.RendezvousCrypto;
+
+import dagger.Module;
+import dagger.Provides;
+
+@Module
+public class RendezvousModule {
+
+	@Provides
+	RendezvousCrypto provideKeyMaterialSourceFactory(
+			RendezvousCryptoImpl keyMaterialSourceFactory) {
+		return keyMaterialSourceFactory;
+	}
+}

bramble-java/src/main/java/org/briarproject/bramble/plugin/modem/ModemPlugin.java

@@ -13,6 +13,8 @@ import org.briarproject.bramble.api.plugin.duplex.AbstractDuplexTransportConnect
 import org.briarproject.bramble.api.plugin.duplex.DuplexPlugin;
 import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
 import org.briarproject.bramble.api.properties.TransportProperties;
+import org.briarproject.bramble.api.rendezvous.KeyMaterialSource;
+import org.briarproject.bramble.api.rendezvous.RendezvousHandler;
 
 import java.io.IOException;
 import java.io.InputStream;
@@ -184,6 +186,16 @@ class ModemPlugin implements DuplexPlugin, Modem.Callback {
 		throw new UnsupportedOperationException();
 	}
 
+	@Override
+	public boolean supportsRendezvous() {
+		return false;
+	}
+
+	@Override
+	public RendezvousHandler createRendezvousHandler(KeyMaterialSource k) {
+		throw new UnsupportedOperationException();
+	}
+
 	@Override
 	public void incomingCallConnected() {
 		LOG.info("Incoming call connected");