public DigestMD5PrivacyIoFilterCodec(IoSession session) {
super(session);
String encoding = (String) session.getAttribute(AuthDigestMD5Command.ENCODING);
try {
AuthDigestMD5IoFilter.computePrivacyKeys(session, encoding, false);
} catch (Exception e) {
e.printStackTrace();
}
encCipher = (Cipher) session.getAttribute(AuthDigestMD5IoFilter.ENCODING_CIPHER);
decCipher = (Cipher) session.getAttribute(AuthDigestMD5IoFilter.DECODING_CIPHER);
}
public void wrap(NextFilter nextFilter, WriteRequest writeRequest, IoBuffer buf)
throws AuthException {
int start = buf.position();
int len = buf.remaining() - LINE_TERMINATOR.length;
if (len == 0) throw new AuthException("Decryption failed");
// HMAC(Ki, {SeqNum, msg})[0..9]
byte[] originalMessage = new byte[len];
buf.get(originalMessage);
byte[] mac = AuthDigestMD5IoFilter.computeMACBlock(session, originalMessage, false);
// Calculate padding
int bs = encCipher.getBlockSize();
byte[] padding;
if (bs > 1) {
int pad = bs - ((len + 10) % bs); // add 10 for HMAC[0..9]
padding = new byte[pad];
for (int i = 0; i < pad; i++) padding[i] = (byte) pad;
} else padding = EMPTY_BYTE_ARRAY;
byte[] toBeEncrypted = new byte[len + padding.length + 10];
// {msg, pad, HMAC(Ki, {SeqNum, msg}[0..9])}
System.arraycopy(originalMessage, start, toBeEncrypted, 0, len);
System.arraycopy(padding, 0, toBeEncrypted, len, padding.length);
System.arraycopy(mac, 0, toBeEncrypted, len + padding.length, 10);
// CIPHER(Kc, {msg, pad, HMAC(Ki, {SeqNum, msg}[0..9])})
byte[] cipherBlock;
try {
// Do CBC (chaining) across packets
cipherBlock = encCipher.update(toBeEncrypted);
// update() can return null
if (cipherBlock == null) throw new IllegalBlockSizeException("" + toBeEncrypted.length);
} catch (IllegalBlockSizeException e) {
throw new AuthException("Invalid block size for cipher", e);
}
IoBuffer out = IoBuffer.allocate(cipherBlock.length + 2 + 4 + LINE_TERMINATOR.length);
out.put(cipherBlock);
out.put(mac, 10, 6); // messageType & sequenceNum
out.put(LINE_TERMINATOR);
out.flip();
if (out.limit()
> ((Integer) session.getAttribute(AuthDigestMD5Command.CLIENT_MAXBUF)).intValue())
throw new AuthException("Data exceeds client maxbuf capability");
nextFilter.filterWrite(session, new DefaultWriteRequest(out, writeRequest.getFuture()));
}
public void unwrap(NextFilter nextFilter, IoBuffer buf) {
try {
int len = buf.remaining();
if (len == 0) throw new AuthException("Decryption failed");
byte[] encryptedMsg = new byte[len - 6];
byte[] msgType = new byte[2];
byte[] seqNum = new byte[4];
// Get cipherMsg; msgType; sequenceNum
buf.get(encryptedMsg);
buf.get(msgType);
buf.get(seqNum);
// Decrypt message - CIPHER(Kc, {msg, pad, HMAC(Ki, {SeqNum, msg}[0..9])})
byte[] decryptedMsg;
try {
// Do CBC (chaining) across packets
decryptedMsg = decCipher.update(encryptedMsg);
// update() can return null
if (decryptedMsg == null) throw new IllegalBlockSizeException("" + encryptedMsg.length);
} catch (IllegalBlockSizeException e) {
throw new AuthException("Illegal block sizes used with chosen cipher", e);
}
byte[] msgWithPadding = new byte[decryptedMsg.length - 10];
byte[] mac = new byte[10];
System.arraycopy(decryptedMsg, 0, msgWithPadding, 0, msgWithPadding.length);
System.arraycopy(decryptedMsg, msgWithPadding.length, mac, 0, 10);
int msgLength = msgWithPadding.length;
int blockSize = decCipher.getBlockSize();
if (blockSize > 1) {
// get value of last octet of the byte array
msgLength -= (int) msgWithPadding[msgWithPadding.length - 1];
if (msgLength < 0)
// Discard message and do not increment sequence number
throw new AuthException("Decryption failed");
}
byte[] msg = new byte[msgLength];
System.arraycopy(msgWithPadding, 0, msg, 0, msgLength);
// Re-calculate MAC to ensure integrity
byte[] expectedMac = AuthDigestMD5IoFilter.computeMACBlock(session, msg, true);
byte[] fullMac = new byte[16];
System.arraycopy(mac, 0, fullMac, 0, 10);
System.arraycopy(msgType, 0, fullMac, 10, 2);
System.arraycopy(seqNum, 0, fullMac, 12, 4);
if (isValidMAC(fullMac, expectedMac)) {
IoBuffer out = IoBuffer.allocate(msgLength + LINE_TERMINATOR.length);
out.put(msg);
out.put(LINE_TERMINATOR);
out.flip();
nextFilter.messageReceived(session, out);
}
} catch (Exception ex) {
log.debug(ex.getMessage());
nextFilter.messageReceived(session, "\r\n");
}
if (session instanceof AbstractIoSession)
((AbstractIoSession) session).increaseReadMessages(System.currentTimeMillis());
}
