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Added an initiator flag (bit 31) to the IV.

Browse Source 
The flag is used to distinguish between the initiator and responder
directions of a stream-mode connection, allowing them to use the same
connection number without risking IV reuse.

The flag is also raised for batch-mode connections, which only have
one direction.
This commit is contained in:
akwizgran
2011-09-07 17:21:52 +01:00
parent 39be97a4d6
commit 7ed747b2a3
13 changed files with 85 additions and 76 deletions
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15
components/net/sf/briar/transport/ConnectionDecrypterImpl.java
View File

@@ -20,8 +20,6 @@ import javax.crypto.spec.IvParameterSpec;
class ConnectionDecrypterImpl extends FilterInputStream
implements ConnectionDecrypter {
private final int transportId;
private final long connection;
private final Cipher frameCipher;
private final SecretKey frameKey;
private final byte[] buf, iv;
@@ -30,15 +28,13 @@ implements ConnectionDecrypter {
private long frame = 0L;
private boolean betweenFrames = true;
ConnectionDecrypterImpl(InputStream in, int transportId, long connection,
Cipher frameCipher, SecretKey frameKey) {
ConnectionDecrypterImpl(InputStream in, boolean initiator, int transportId,
long connection, Cipher frameCipher, SecretKey frameKey) {
super(in);
this.transportId = transportId;
this.connection = connection;
this.frameCipher = frameCipher;
this.frameKey = frameKey;
buf = new byte[IV_LENGTH];
iv = new byte[IV_LENGTH];
iv = IvEncoder.encodeIv(initiator, transportId, connection);
}
public InputStream getInputStream() {
@@ -132,8 +128,7 @@ implements ConnectionDecrypter {
private void initialiseCipher() {
assert betweenFrames;
if(frame > MAX_32_BIT_UNSIGNED) throw new IllegalStateException();
IvEncoder.encodeIv(iv, transportId, connection, frame);
// Use the plaintext IV to initialise the frame cipher
IvEncoder.updateIv(iv, frame);
IvParameterSpec ivSpec = new IvParameterSpec(iv);
try {
frameCipher.init(Cipher.DECRYPT_MODE, frameKey, ivSpec);
@@ -145,4 +140,4 @@ implements ConnectionDecrypter {
frame++;
betweenFrames = false;
}
}
}

29
components/net/sf/briar/transport/ConnectionEncrypterImpl.java
View File

@@ -18,25 +18,21 @@ import javax.crypto.spec.IvParameterSpec;
class ConnectionEncrypterImpl extends FilterOutputStream
implements ConnectionEncrypter {
private final int transportId;
private final long connection;
private final Cipher ivCipher, frameCipher;
private final SecretKey frameKey;
private final byte[] iv;
private long frame = 0L;
private boolean started = false, betweenFrames = false;
private boolean ivWritten = false, betweenFrames = false;
ConnectionEncrypterImpl(OutputStream out, int transportId,
long connection, Cipher ivCipher, Cipher frameCipher,
SecretKey ivKey, SecretKey frameKey) {
ConnectionEncrypterImpl(OutputStream out, boolean initiator,
int transportId, long connection, Cipher ivCipher,
Cipher frameCipher, SecretKey ivKey, SecretKey frameKey) {
super(out);
this.transportId = transportId;
this.connection = connection;
this.ivCipher = ivCipher;
this.frameCipher = frameCipher;
this.frameKey = frameKey;
iv = new byte[IV_LENGTH];
iv = IvEncoder.encodeIv(initiator, transportId, connection);
try {
ivCipher.init(Cipher.ENCRYPT_MODE, ivKey);
} catch(InvalidKeyException badKey) {
@@ -51,7 +47,7 @@ implements ConnectionEncrypter {
}
public void writeMac(byte[] mac) throws IOException {
if(!started || betweenFrames) throw new IllegalStateException();
if(!ivWritten || betweenFrames) throw new IllegalStateException();
try {
out.write(frameCipher.doFinal(mac));
} catch(BadPaddingException badCipher) {
@@ -64,7 +60,7 @@ implements ConnectionEncrypter {
@Override
public void write(int b) throws IOException {
if(!started) writeIv();
if(!ivWritten) writeIv();
if(betweenFrames) initialiseCipher();
byte[] ciphertext = frameCipher.update(new byte[] {(byte) b});
if(ciphertext != null) out.write(ciphertext);
@@ -77,16 +73,15 @@ implements ConnectionEncrypter {
@Override
public void write(byte[] b, int off, int len) throws IOException {
if(!started) writeIv();
if(!ivWritten) writeIv();
if(betweenFrames) initialiseCipher();
byte[] ciphertext = frameCipher.update(b, off, len);
if(ciphertext != null) out.write(ciphertext);
}
private void writeIv() throws IOException {
assert !started;
assert !ivWritten;
assert !betweenFrames;
IvEncoder.encodeIv(iv, transportId, connection, 0L);
try {
out.write(ivCipher.doFinal(iv));
} catch(BadPaddingException badCipher) {
@@ -94,15 +89,15 @@ implements ConnectionEncrypter {
} catch(IllegalBlockSizeException badCipher) {
throw new RuntimeException(badCipher);
}
started = true;
ivWritten = true;
betweenFrames = true;
}
private void initialiseCipher() {
assert started;
assert ivWritten;
assert betweenFrames;
if(frame > MAX_32_BIT_UNSIGNED) throw new IllegalStateException();
IvEncoder.encodeIv(iv, transportId, connection, frame);
IvEncoder.updateIv(iv, frame);
IvParameterSpec ivSpec = new IvParameterSpec(iv);
try {
frameCipher.init(Cipher.ENCRYPT_MODE, frameKey, ivSpec);

5
components/net/sf/briar/transport/ConnectionReaderFactoryImpl.java
View File

@@ -23,7 +23,8 @@ class ConnectionReaderFactoryImpl implements ConnectionReaderFactory {
}
public ConnectionReader createConnectionReader(InputStream in,
int transportId, long connection, byte[] secret) {
boolean initiator, int transportId, long connection,
byte[] secret) {
SecretKey macKey = crypto.deriveIncomingMacKey(secret);
SecretKey frameKey = crypto.deriveIncomingFrameKey(secret);
Cipher frameCipher = crypto.getFrameCipher();
@@ -34,7 +35,7 @@ class ConnectionReaderFactoryImpl implements ConnectionReaderFactory {
throw new IllegalArgumentException(e);
}
ConnectionDecrypter decrypter = new ConnectionDecrypterImpl(in,
transportId, connection, frameCipher, frameKey);
initiator, transportId, connection, frameCipher, frameKey);
return new ConnectionReaderImpl(decrypter, mac);
}
}

2
components/net/sf/briar/transport/ConnectionRecogniserImpl.java
View File

@@ -81,7 +81,7 @@ DatabaseListener {
}
private synchronized byte[] encryptIv(ContactId c, long connection) {
byte[] iv = IvEncoder.encodeIv(transportId, connection);
byte[] iv = IvEncoder.encodeIv(true, transportId, connection);
Cipher cipher = contactToCipher.get(c);
assert cipher != null;
try {

7
components/net/sf/briar/transport/ConnectionWriterFactoryImpl.java
View File

@@ -23,7 +23,8 @@ class ConnectionWriterFactoryImpl implements ConnectionWriterFactory {
}
public ConnectionWriter createConnectionWriter(OutputStream out,
int transportId, long connection, byte[] secret) {
boolean initiator, int transportId, long connection,
byte[] secret) {
SecretKey macKey = crypto.deriveOutgoingMacKey(secret);
SecretKey ivKey = crypto.deriveOutgoingIvKey(secret);
SecretKey frameKey = crypto.deriveOutgoingFrameKey(secret);
@@ -36,8 +37,8 @@ class ConnectionWriterFactoryImpl implements ConnectionWriterFactory {
throw new IllegalArgumentException(badKey);
}
ConnectionEncrypter encrypter = new ConnectionEncrypterImpl(out,
transportId, connection, ivCipher, frameCipher, ivKey,
frameKey);
initiator, transportId, connection, ivCipher, frameCipher,
ivKey, frameKey);
return new ConnectionWriterImpl(encrypter, mac);
}
}

18
components/net/sf/briar/transport/IvEncoder.java
View File

@@ -5,8 +5,11 @@ import net.sf.briar.util.ByteUtils;
class IvEncoder {
static byte[] encodeIv(int transportId, long connection) {
static byte[] encodeIv(boolean initiator, int transportId,
long connection) {
byte[] iv = new byte[IV_LENGTH];
// Bit 31 is the initiator flag
if(initiator) iv[3] = 1;
// Encode the transport identifier as an unsigned 16-bit integer
ByteUtils.writeUint16(transportId, iv, 4);
// Encode the connection number as an unsigned 32-bit integer
@@ -14,20 +17,9 @@ class IvEncoder {
return iv;
}
static void encodeIv(byte[] iv, int transportId, long connection,
long frame) {
static void updateIv(byte[] iv, long frame) {
if(iv.length != IV_LENGTH) throw new IllegalArgumentException();
// The first 16 bits of the IV must be zero (reserved)
iv[0] = 0;
iv[1] = 0;
// Encode the transport identifier as an unsigned 16-bit integer
ByteUtils.writeUint16(transportId, iv, 4);
// Encode the connection number as an unsigned 32-bit integer
ByteUtils.writeUint32(connection, iv, 6);
// Encode the frame number as an unsigned 32-bit integer
ByteUtils.writeUint32(frame, iv, 10);
// The last 16 bits of the IV must be zero (block number)
iv[14] = 0;
iv[15] = 0;
}
}