Validate the decrypted IV before creating a reader/writer.

api/net/sf/briar/api/transport/BatchConnectionFactory.java

@@ -5,8 +5,8 @@ import net.sf.briar.api.TransportId;
 
 public interface BatchConnectionFactory {
 
-	void createIncomingConnection(ContactId c, BatchTransportReader r,
-			byte[] encryptedIv);
+	void createIncomingConnection(TransportId t, ContactId c,
+			BatchTransportReader r, byte[] encryptedIv);
 
 	void createOutgoingConnection(TransportId t, ContactId c,
 			BatchTransportWriter w);

api/net/sf/briar/api/transport/ConnectionReaderFactory.java

@@ -6,9 +6,17 @@ import net.sf.briar.api.TransportId;
 
 public interface ConnectionReaderFactory {
 
-	ConnectionReader createConnectionReader(InputStream in, byte[] encryptedIv,
-			byte[] secret);
+	/**
+	 * Creates a connection reader for a batch-mode connection or the
+	 * initiator's side of a stream-mode connection.
+	 */
+	ConnectionReader createConnectionReader(InputStream in, TransportId t,
+			byte[] encryptedIv, byte[] secret);
 
-	ConnectionReader createConnectionReader(InputStream in, boolean initiator,
-			TransportId t, long connection, byte[] secret);
+	/**
+	 * Creates a connection reader for the responder's side of a stream-mode
+	 * connection.
+	 */
+	ConnectionReader createConnectionReader(InputStream in, TransportId t,
+			long connection, byte[] secret);
 }

api/net/sf/briar/api/transport/ConnectionWriterFactory.java

@@ -6,9 +6,17 @@ import net.sf.briar.api.TransportId;
 
 public interface ConnectionWriterFactory {
 
+	/**
+	 * Creates a connection writer for a batch-mode connection or the
+	 * initiator's side of a stream-mode connection.
+	 */
 	ConnectionWriter createConnectionWriter(OutputStream out, long capacity,
-			boolean initiator, TransportId t, long connection, byte[] secret);
+			TransportId t, long connection, byte[] secret);
 
+	/**
+	 * Creates a connection writer for the responder's side of a stream-mode
+	 * connection.
+	 */
 	ConnectionWriter createConnectionWriter(OutputStream out, long capacity,
 			TransportId t, byte[] encryptedIv, byte[] secret);
 }

components/net/sf/briar/transport/ConnectionDecrypterImpl.java

@@ -28,26 +28,6 @@ implements ConnectionDecrypter {
 	private long frame = 0L;
 	private boolean betweenFrames = true;
 
-	ConnectionDecrypterImpl(InputStream in, byte[] encryptedIv, Cipher ivCipher,
-			Cipher frameCipher, SecretKey ivKey, SecretKey frameKey) {
-		super(in);
-		this.frameCipher = frameCipher;
-		this.frameKey = frameKey;
-		// Decrypt the IV
-		try {
-			ivCipher.init(Cipher.DECRYPT_MODE, ivKey);
-			iv = ivCipher.doFinal(encryptedIv);
-		} catch(BadPaddingException badCipher) {
-			throw new IllegalArgumentException(badCipher);
-		} catch(IllegalBlockSizeException badCipher) {
-			throw new IllegalArgumentException(badCipher);
-		} catch(InvalidKeyException badKey) {
-			throw new IllegalArgumentException(badKey);
-		}
-		if(iv.length != IV_LENGTH) throw new IllegalArgumentException();
-		buf = new byte[IV_LENGTH];
-	}
-
 	ConnectionDecrypterImpl(InputStream in, byte[] iv, Cipher frameCipher,
 			SecretKey frameKey) {
 		super(in);

components/net/sf/briar/transport/ConnectionDispatcherImpl.java

@@ -63,7 +63,7 @@ public class ConnectionDispatcherImpl implements ConnectionDispatcher {
 			r.dispose(false);
 			return;
 		}
-		batchConnFactory.createIncomingConnection(c, r, encryptedIv);
+		batchConnFactory.createIncomingConnection(t, c, r, encryptedIv);
 	}
 
 	private byte[] readIv(InputStream in) throws IOException {

components/net/sf/briar/transport/ConnectionReaderFactoryImpl.java

@@ -1,8 +1,11 @@
 package net.sf.briar.transport;
 
 import java.io.InputStream;
+import java.security.InvalidKeyException;
 
+import javax.crypto.BadPaddingException;
 import javax.crypto.Cipher;
+import javax.crypto.IllegalBlockSizeException;
 import javax.crypto.Mac;
 import javax.crypto.SecretKey;
 
@@ -23,21 +26,35 @@ class ConnectionReaderFactoryImpl implements ConnectionReaderFactory {
 	}
 
 	public ConnectionReader createConnectionReader(InputStream in,
-			byte[] encryptedIv, byte[] secret) {
-		// Create the decrypter
+			TransportId t, byte[] encryptedIv, byte[] secret) {
+		// Decrypt the IV
 		Cipher ivCipher = crypto.getIvCipher();
-		Cipher frameCipher = crypto.getFrameCipher();
 		SecretKey ivKey = crypto.deriveIncomingIvKey(secret);
-		SecretKey frameKey = crypto.deriveIncomingFrameKey(secret);
-		ConnectionDecrypter decrypter = new ConnectionDecrypterImpl(in,
-				encryptedIv, ivCipher, frameCipher, ivKey, frameKey);
-		// Create the reader
-		Mac mac = crypto.getMac();
-		SecretKey macKey = crypto.deriveIncomingMacKey(secret);
-		return new ConnectionReaderImpl(decrypter, mac, macKey);
+		byte[] iv;
+		try {
+			ivCipher.init(Cipher.DECRYPT_MODE, ivKey);
+			iv = ivCipher.doFinal(encryptedIv);
+		} catch(BadPaddingException badCipher) {
+			throw new IllegalArgumentException(badCipher);
+		} catch(IllegalBlockSizeException badCipher) {
+			throw new IllegalArgumentException(badCipher);
+		} catch(InvalidKeyException badKey) {
+			throw new IllegalArgumentException(badKey);
+		}
+		// Validate the IV
+		if(!IvEncoder.validateIv(iv, true, t))
+			throw new IllegalArgumentException();
+		// Copy the connection number
+		long connection = IvEncoder.getConnectionNumber(iv);
+		return createConnectionReader(in, true, t, connection, secret);
 	}
 
 	public ConnectionReader createConnectionReader(InputStream in,
+			TransportId t, long connection, byte[] secret) {
+		return createConnectionReader(in, false, t, connection, secret);
+	}
+
+	private ConnectionReader createConnectionReader(InputStream in,
 			boolean initiator, TransportId t, long connection, byte[] secret) {
 		byte[] iv = IvEncoder.encodeIv(initiator, t, connection);
 		// Create the decrypter

components/net/sf/briar/transport/ConnectionWriterFactoryImpl.java

@@ -26,20 +26,9 @@ class ConnectionWriterFactoryImpl implements ConnectionWriterFactory {
 	}
 
 	public ConnectionWriter createConnectionWriter(OutputStream out,
-			long capacity, boolean initiator, TransportId t, long connection,
-			byte[] secret) {
-		// Create the encrypter
-		Cipher ivCipher = crypto.getIvCipher();
-		Cipher frameCipher = crypto.getFrameCipher();
-		SecretKey ivKey = crypto.deriveOutgoingIvKey(secret);
-		SecretKey frameKey = crypto.deriveOutgoingFrameKey(secret);
-		byte[] iv = IvEncoder.encodeIv(initiator, t, connection);
-		ConnectionEncrypter encrypter = new ConnectionEncrypterImpl(out,
-				capacity, iv, ivCipher, frameCipher, ivKey, frameKey);
-		// Create the writer
-		Mac mac = crypto.getMac();
-		SecretKey macKey = crypto.deriveOutgoingMacKey(secret);
-		return new ConnectionWriterImpl(encrypter, mac, macKey);
+			long capacity, TransportId t, long connection, byte[] secret) {
+		return createConnectionWriter(out, capacity, true, t, connection,
+				secret);
 	}
 
 	public ConnectionWriter createConnectionWriter(OutputStream out,
@@ -58,15 +47,29 @@ class ConnectionWriterFactoryImpl implements ConnectionWriterFactory {
 		} catch(InvalidKeyException badKey) {
 			throw new RuntimeException(badKey);
 		}
-		// Check that the initiator flag is raised
-		if(!IvEncoder.getInitiatorFlag(iv))
-			throw new IllegalArgumentException();
-		// Check that the transport ID matches the expected ID
-		if(!t.equals(new TransportId(IvEncoder.getTransportId(iv))))
+		// Validate the IV
+		if(!IvEncoder.validateIv(iv, true, t))
 			throw new IllegalArgumentException();
 		// Copy the connection number
 		long connection = IvEncoder.getConnectionNumber(iv);
 		return createConnectionWriter(out, capacity, false, t, connection,
 				secret);
 	}
+
+	private ConnectionWriter createConnectionWriter(OutputStream out,
+			long capacity, boolean initiator, TransportId t, long connection,
+			byte[] secret) {
+		// Create the encrypter
+		Cipher ivCipher = crypto.getIvCipher();
+		Cipher frameCipher = crypto.getFrameCipher();
+		SecretKey ivKey = crypto.deriveOutgoingIvKey(secret);
+		SecretKey frameKey = crypto.deriveOutgoingFrameKey(secret);
+		byte[] iv = IvEncoder.encodeIv(initiator, t, connection);
+		ConnectionEncrypter encrypter = new ConnectionEncrypterImpl(out,
+				capacity, iv, ivCipher, frameCipher, ivKey, frameKey);
+		// Create the writer
+		Mac mac = crypto.getMac();
+		SecretKey macKey = crypto.deriveOutgoingMacKey(secret);
+		return new ConnectionWriterImpl(encrypter, mac, macKey);
+	}
 }

components/net/sf/briar/transport/IvEncoder.java

@@ -24,6 +24,20 @@ class IvEncoder {
 		ByteUtils.writeUint32(frame, iv, 10);
 	}
 
+	static boolean validateIv(byte[] iv, boolean initiator, TransportId t) {
+		if(iv.length != IV_LENGTH) return false;
+		// Check that the reserved bits are all zero
+		for(int i = 0; i < 2; i++) if(iv[i] != 0) return false;
+		if(iv[3] != 0 && iv[3] != 1) return false;
+		for(int i = 10; i < iv.length; i++) if(iv[i] != 0) return false;
+		// Check that the initiator flag matches
+		if(initiator != getInitiatorFlag(iv)) return false;
+		// Check that the transport ID matches
+		if(t.getInt() != getTransportId(iv)) return false;
+		// The IV is valid
+		return true;
+	}
+
 	static boolean getInitiatorFlag(byte[] iv) {
 		if(iv.length != IV_LENGTH) throw new IllegalArgumentException();
 		return (iv[3] & 1) == 1;

components/net/sf/briar/transport/batch/BatchConnectionFactoryImpl.java

@@ -33,10 +33,11 @@ class BatchConnectionFactoryImpl implements BatchConnectionFactory {
 		this.protoWriterFactory = protoWriterFactory;
 	}
 
-	public void createIncomingConnection(ContactId c,
+	public void createIncomingConnection(TransportId t, ContactId c,
 			BatchTransportReader r, byte[] encryptedIv) {
 		final IncomingBatchConnection conn = new IncomingBatchConnection(
-				connReaderFactory, db, protoReaderFactory, c, r, encryptedIv);
+				connReaderFactory, db, protoReaderFactory, t, c, r,
+				encryptedIv);
 		Runnable read = new Runnable() {
 			public void run() {
 				conn.read();

components/net/sf/briar/transport/batch/IncomingBatchConnection.java

@@ -6,6 +6,7 @@ import java.util.logging.Logger;
 
 import net.sf.briar.api.ContactId;
 import net.sf.briar.api.FormatException;
+import net.sf.briar.api.TransportId;
 import net.sf.briar.api.db.DatabaseComponent;
 import net.sf.briar.api.db.DbException;
 import net.sf.briar.api.protocol.Ack;
@@ -26,17 +27,19 @@ class IncomingBatchConnection {
 	private final ConnectionReaderFactory connFactory;
 	private final DatabaseComponent db;
 	private final ProtocolReaderFactory protoFactory;
+	private final TransportId transportId;
 	private final ContactId contactId;
 	private final BatchTransportReader reader;
 	private final byte[] encryptedIv;
 
 	IncomingBatchConnection(ConnectionReaderFactory connFactory,
 			DatabaseComponent db, ProtocolReaderFactory protoFactory,
-			ContactId contactId, BatchTransportReader reader,
-			byte[] encryptedIv) {
+			TransportId transportId, ContactId contactId,
+			BatchTransportReader reader, byte[] encryptedIv) {
 		this.connFactory = connFactory;
 		this.db = db;
 		this.protoFactory = protoFactory;
+		this.transportId = transportId;
 		this.contactId = contactId;
 		this.reader = reader;
 		this.encryptedIv = encryptedIv;
@@ -46,7 +49,7 @@ class IncomingBatchConnection {
 		try {
 			byte[] secret = db.getSharedSecret(contactId);
 			ConnectionReader conn = connFactory.createConnectionReader(
-					reader.getInputStream(), encryptedIv, secret);
+					reader.getInputStream(), transportId, encryptedIv, secret);
 			ProtocolReader proto = protoFactory.createProtocolReader(
 					conn.getInputStream());
 			// Read packets until EOF

components/net/sf/briar/transport/batch/OutgoingBatchConnection.java

@@ -49,8 +49,8 @@ class OutgoingBatchConnection {
 			byte[] secret = db.getSharedSecret(contactId);
 			long connection = db.getConnectionNumber(contactId, transportId);
 			ConnectionWriter conn = connFactory.createConnectionWriter(
-					writer.getOutputStream(), writer.getCapacity(), true,
-					transportId, connection, secret);
+					writer.getOutputStream(), writer.getCapacity(), transportId,
+					connection, secret);
 			OutputStream out = conn.getOutputStream();
 			// There should be enough space for a packet
 			long capacity = conn.getRemainingCapacity();

components/net/sf/briar/transport/stream/IncomingStreamConnection.java

@@ -34,7 +34,7 @@ public class IncomingStreamConnection extends StreamConnection {
 	IOException {
 		byte[] secret = db.getSharedSecret(contactId);
 		return connReaderFactory.createConnectionReader(
-				connection.getInputStream(), encryptedIv, secret);
+				connection.getInputStream(), transportId, encryptedIv, secret);
 	}
 
 	@Override

components/net/sf/briar/transport/stream/OutgoingStreamConnection.java

@@ -36,7 +36,7 @@ public class OutgoingStreamConnection extends StreamConnection {
 		}
 		byte[] secret = db.getSharedSecret(contactId);
 		return connReaderFactory.createConnectionReader(
-				connection.getInputStream(), false, transportId, connectionNum,
+				connection.getInputStream(), transportId, connectionNum,
 				secret);
 	}
 
@@ -49,7 +49,7 @@ public class OutgoingStreamConnection extends StreamConnection {
 		}
 		byte[] secret = db.getSharedSecret(contactId);
 		return connWriterFactory.createConnectionWriter(
-				connection.getOutputStream(), Long.MAX_VALUE, true, transportId,
+				connection.getOutputStream(), Long.MAX_VALUE, transportId,
 				connectionNum, secret);
 	}
 }

test/net/sf/briar/ProtocolIntegrationTest.java

@@ -131,7 +131,7 @@ public class ProtocolIntegrationTest extends TestCase {
 		ByteArrayOutputStream out = new ByteArrayOutputStream();
 		// Use Alice's secret for writing
 		ConnectionWriter w = connectionWriterFactory.createConnectionWriter(out,
-				Long.MAX_VALUE, true, transportId, connection, aliceSecret);
+				Long.MAX_VALUE, transportId, connection, aliceSecret);
 		OutputStream out1 = w.getOutputStream();
 
 		AckWriter a = protocolWriterFactory.createAckWriter(out1);
@@ -175,17 +175,17 @@ public class ProtocolIntegrationTest extends TestCase {
 
 	private void read(byte[] connection) throws Exception {
 		InputStream in = new ByteArrayInputStream(connection);
-		byte[] iv = new byte[16];
+		byte[] encryptedIv = new byte[16];
 		int offset = 0;
 		while(offset < 16) {
-			int read = in.read(iv, offset, iv.length - offset);
+			int read = in.read(encryptedIv, offset, 16 - offset);
 			if(read == -1) break;
 			offset += read;
 		}
 		assertEquals(16, offset);
 		// Use Bob's secret for reading
 		ConnectionReader r = connectionReaderFactory.createConnectionReader(in,
-				iv, bobSecret);
+				transportId, encryptedIv, bobSecret);
 		in = r.getInputStream();
 		ProtocolReader protocolReader =
 			protocolReaderFactory.createProtocolReader(in);

test/net/sf/briar/transport/ConnectionDecrypterImplTest.java

@@ -84,8 +84,9 @@ public class ConnectionDecrypterImplTest extends TestCase {
 		out.write(ciphertextMac);
 		ByteArrayInputStream in = new ByteArrayInputStream(out.toByteArray());
 		// Use a ConnectionDecrypter to decrypt the ciphertext
-		ConnectionDecrypter d = new ConnectionDecrypterImpl(in, encryptedIv,
-				ivCipher, frameCipher, ivKey, frameKey);
+		ConnectionDecrypter d = new ConnectionDecrypterImpl(in, 
+				IvEncoder.encodeIv(initiator, transportId, connection),
+				frameCipher, frameKey);
 		// First frame
 		byte[] decrypted = new byte[ciphertext.length];
 		TestUtils.readFully(d.getInputStream(), decrypted);

test/net/sf/briar/transport/ConnectionWriterTest.java

@@ -40,7 +40,7 @@ public class ConnectionWriterTest extends TestCase {
 		ByteArrayOutputStream out =
 			new ByteArrayOutputStream(MIN_CONNECTION_LENGTH);
 		ConnectionWriter w = connectionWriterFactory.createConnectionWriter(out,
-				MIN_CONNECTION_LENGTH, true, transportId, connection, secret);
+				MIN_CONNECTION_LENGTH, transportId, connection, secret);
 		// Check that the connection writer thinks there's room for a packet
 		long capacity = w.getRemainingCapacity();
 		assertTrue(capacity >= MAX_PACKET_LENGTH);

test/net/sf/briar/transport/FrameReadWriteTest.java

@@ -84,12 +84,17 @@ public class FrameReadWriteTest extends TestCase {
 		out1.flush();
 		// Read the IV back
 		ByteArrayInputStream in = new ByteArrayInputStream(out.toByteArray());
-		byte[] recoveredIv = new byte[IV_LENGTH];
-		assertEquals(IV_LENGTH, in.read(recoveredIv));
-		assertArrayEquals(encryptedIv, recoveredIv);
+		byte[] recoveredEncryptedIv = new byte[IV_LENGTH];
+		assertEquals(IV_LENGTH, in.read(recoveredEncryptedIv));
+		assertArrayEquals(encryptedIv, recoveredEncryptedIv);
+		// Decrypt the IV
+		ivCipher.init(Cipher.DECRYPT_MODE, ivKey);
+		byte[] recoveredIv = ivCipher.doFinal(recoveredEncryptedIv);
+		iv = IvEncoder.encodeIv(initiator, transportId, connection);
+		assertArrayEquals(iv, recoveredIv);
 		// Read the frames back
-		ConnectionDecrypter decrypter = new ConnectionDecrypterImpl(in,
-				recoveredIv, ivCipher, frameCipher, ivKey, frameKey);
+		ConnectionDecrypter decrypter = new ConnectionDecrypterImpl(in, iv,
+				frameCipher, frameKey);
 		ConnectionReader reader = new ConnectionReaderImpl(decrypter, mac,
 				macKey);
 		InputStream in1 = reader.getInputStream();

test/net/sf/briar/transport/batch/BatchConnectionReadWriteTest.java

@@ -145,7 +145,8 @@ public class BatchConnectionReadWriteTest extends TestCase {
 			bob.getInstance(ProtocolReaderFactory.class);
 		BatchTransportReader reader = new TestBatchTransportReader(in);
 		IncomingBatchConnection batchIn = new IncomingBatchConnection(
-				connFactory, db, protoFactory, contactId, reader, encryptedIv);
+				connFactory, db, protoFactory, transportId, contactId, reader,
+				encryptedIv);
 		// No messages should have been added yet
 		assertFalse(listener.messagesAdded);
 		// Read whatever needs to be read