private String handleDataMessage(DataMessage data, List<TLV> tlvs) throws OtrException {
logger.finest(
getSessionID().getAccountID()
+ " received a data message from "
+ getSessionID().getUserID()
+ ".");
switch (this.getSessionStatus()) {
case ENCRYPTED:
logger.finest("Message state is ENCRYPTED. Trying to decrypt message.");
// Find matching session keys.
int senderKeyID = data.senderKeyID;
int receipientKeyID = data.recipientKeyID;
SessionKeys matchingKeys = this.getSessionKeysByID(receipientKeyID, senderKeyID);
if (matchingKeys == null) {
throw new OtrException("no matching keys found");
}
// Verify received MAC with a locally calculated MAC.
logger.finest("Transforming T to byte[] to calculate it's HmacSHA1.");
byte[] serializedT;
try {
serializedT = SerializationUtils.toByteArray(data.getT());
} catch (IOException e) {
throw new OtrException(e);
}
OtrCryptoEngine otrCryptoEngine = new OtrCryptoEngineImpl();
byte[] computedMAC =
otrCryptoEngine.sha1Hmac(
serializedT,
matchingKeys.getReceivingMACKey(),
SerializationConstants.TYPE_LEN_MAC);
if (!Arrays.equals(computedMAC, data.mac)) {
throw new OtrException("MAC verification failed, ignoring message");
}
logger.finest("Computed HmacSHA1 value matches sent one.");
// Mark this MAC key as old to be revealed.
matchingKeys.setIsUsedReceivingMACKey(true);
matchingKeys.setReceivingCtr(data.ctr);
byte[] dmc =
otrCryptoEngine.aesDecrypt(
matchingKeys.getReceivingAESKey(),
matchingKeys.getReceivingCtr(),
data.encryptedMessage);
String decryptedMsgContent;
try {
// Expect bytes to be text encoded in UTF-8.
decryptedMsgContent = new String(dmc, "UTF-8");
} catch (UnsupportedEncodingException e) {
throw new OtrException(e);
}
logger.finest("Decrypted message: \"" + decryptedMsgContent + "\"");
// FIXME extraKey = authContext.getExtraSymmetricKey();
// Rotate keys if necessary.
SessionKeys mostRecent = this.getMostRecentSessionKeys();
if (mostRecent.getLocalKeyID() == receipientKeyID) this.rotateLocalSessionKeys();
if (mostRecent.getRemoteKeyID() == senderKeyID) this.rotateRemoteSessionKeys(data.nextDH);
// Handle TLVs
if (tlvs == null) {
tlvs = new ArrayList<TLV>();
}
int tlvIndex = decryptedMsgContent.indexOf((char) 0x0);
if (tlvIndex > -1) {
decryptedMsgContent = decryptedMsgContent.substring(0, tlvIndex);
tlvIndex++;
byte[] tlvsb = new byte[dmc.length - tlvIndex];
System.arraycopy(dmc, tlvIndex, tlvsb, 0, tlvsb.length);
ByteArrayInputStream tin = new ByteArrayInputStream(tlvsb);
while (tin.available() > 0) {
int type;
byte[] tdata;
OtrInputStream eois = new OtrInputStream(tin);
try {
type = eois.readShort();
tdata = eois.readTlvData();
eois.close();
} catch (IOException e) {
throw new OtrException(e);
}
tlvs.add(new TLV(type, tdata));
}
}
if (tlvs.size() > 0) {
for (TLV tlv : tlvs) {
switch (tlv.getType()) {
case TLV.DISCONNECTED:
this.setSessionStatus(SessionStatus.FINISHED);
return null;
default:
for (OtrTlvHandler handler : tlvHandlers) {
handler.processTlv(tlv);
}
}
}
}
return decryptedMsgContent;
case FINISHED:
case PLAINTEXT:
showError("Unreadable encrypted message was received.");
injectMessage(
new ErrorMessage(
AbstractMessage.MESSAGE_ERROR, "You sent me an unreadable encrypted message"));
throw new OtrException("Unreadable encrypted message received");
}
return null;
}
private void handleRevealSignatureMessage(RevealSignatureMessage m) throws OtrException {
Session session = getSession();
SessionID sessionID = session.getSessionID();
logger.finest(
sessionID.getLocalUserId()
+ " received a reveal signature message from "
+ sessionID.getRemoteUserId()
+ " throught "
+ sessionID.getProtocolName()
+ ".");
if (!session.getSessionPolicy().getAllowV2()) {
logger.finest("Policy does not allow OTRv2, ignoring message.");
return;
}
switch (this.getAuthenticationState()) {
case AWAITING_REVEALSIG:
// Use the received value of r to decrypt the value of gx
// received
// in the D-H Commit Message, and verify the hash therein.
// Decrypt
// the encrypted signature, and verify the signature and the
// MACs.
// If everything checks out:
// * Reply with a Signature Message.
// * Transition authstate to AUTHSTATE_NONE.
// * Transition msgstate to MSGSTATE_ENCRYPTED.
// * TODO If there is a recent stored message, encrypt it and
// send
// it as a Data Message.
OtrCryptoEngine otrCryptoEngine = new OtrCryptoEngineImpl();
// Uses r to decrypt the value of gx sent earlier
byte[] remoteDHPublicKeyDecrypted =
otrCryptoEngine.aesDecrypt(m.revealedKey, null, this.getRemoteDHPublicKeyEncrypted());
// Verifies that HASH(gx) matches the value sent earlier
byte[] remoteDHPublicKeyHash = otrCryptoEngine.sha256Hash(remoteDHPublicKeyDecrypted);
if (!Arrays.equals(remoteDHPublicKeyHash, this.getRemoteDHPublicKeyHash())) {
logger.finest("Hashes don't match, ignoring message.");
return;
}
// Verifies that Bob's gx is a legal value (2 <= gx <=
// modulus-2)
BigInteger remoteDHPublicKeyMpi;
try {
remoteDHPublicKeyMpi = SerializationUtils.readMpi(remoteDHPublicKeyDecrypted);
} catch (IOException e) {
throw new OtrException(e);
}
this.setRemoteDHPublicKey(otrCryptoEngine.getDHPublicKey(remoteDHPublicKeyMpi));
// Verify received Data.
if (!m.verify(this.getM2())) {
logger.finest("Signature MACs are not equal, ignoring message.");
return;
}
// Decrypt X.
byte[] remoteXDecrypted = m.decrypt(this.getC());
SignatureX remoteX;
try {
remoteX = SerializationUtils.toMysteriousX(remoteXDecrypted);
} catch (IOException e) {
throw new OtrException(e);
}
// Compute signature.
PublicKey remoteLongTermPublicKey = remoteX.longTermPublicKey;
SignatureM remoteM =
new SignatureM(
this.getRemoteDHPublicKey(),
(DHPublicKey) this.getLocalDHKeyPair().getPublic(),
remoteLongTermPublicKey,
remoteX.dhKeyID);
// Verify signature.
byte[] signature;
try {
signature =
otrCryptoEngine.sha256Hmac(SerializationUtils.toByteArray(remoteM), this.getM1());
} catch (IOException e) {
throw new OtrException(e);
}
if (!otrCryptoEngine.verify(signature, remoteLongTermPublicKey, remoteX.signature)) {
session.showWarning("Bad revealed signature");
logger.finest("Signature verification failed.");
return;
}
logger.finest("Signature verification succeeded.");
this.setAuthenticationState(AuthContext.NONE);
this.setIsSecure(true);
this.setRemoteLongTermPublicKey(remoteLongTermPublicKey);
getSession().injectMessage(messageFactory.getSignatureMessage());
break;
default:
logger.finest("Ignoring message.");
break;
}
}