public String transformSending(String msgText, List<TLV> tlvs) throws OtrException {
switch (this.getSessionStatus()) {
case PLAINTEXT:
if (getSessionPolicy().getRequireEncryption()) {
lastSentMessage = msgText;
doTransmitLastMessage = true;
this.startSession();
return null;
} else
// TODO this does not precisly behave according to
// specification.
return msgText;
case ENCRYPTED:
this.lastSentMessage = msgText;
logger.finest(
getSessionID().getAccountID()
+ " sends an encrypted message to "
+ getSessionID().getUserID()
+ " through "
+ getSessionID().getProtocolName()
+ ".");
// Get encryption keys.
SessionKeys encryptionKeys = this.getEncryptionSessionKeys();
int senderKeyID = encryptionKeys.getLocalKeyID();
int receipientKeyID = encryptionKeys.getRemoteKeyID();
// Increment CTR.
encryptionKeys.incrementSendingCtr();
byte[] ctr = encryptionKeys.getSendingCtr();
ByteArrayOutputStream out = new ByteArrayOutputStream();
if (msgText != null && msgText.length() > 0)
try {
out.write(msgText.getBytes("UTF8"));
} catch (IOException e) {
throw new OtrException(e);
}
// Append tlvs
if (tlvs != null && tlvs.size() > 0) {
out.write((byte) 0x00);
OtrOutputStream eoos = new OtrOutputStream(out);
for (TLV tlv : tlvs) {
try {
eoos.writeShort(tlv.type);
eoos.writeTlvData(tlv.value);
} catch (IOException e) {
throw new OtrException(e);
}
}
}
OtrCryptoEngine otrCryptoEngine = new OtrCryptoEngineImpl();
byte[] data = out.toByteArray();
// Encrypt message.
logger.finest(
"Encrypting message with keyids (localKeyID, remoteKeyID) = ("
+ senderKeyID
+ ", "
+ receipientKeyID
+ ")");
byte[] encryptedMsg =
otrCryptoEngine.aesEncrypt(encryptionKeys.getSendingAESKey(), ctr, data);
// Get most recent keys to get the next D-H public key.
SessionKeys mostRecentKeys = this.getMostRecentSessionKeys();
DHPublicKey nextDH = (DHPublicKey) mostRecentKeys.getLocalPair().getPublic();
// Calculate T.
MysteriousT t =
new MysteriousT(2, 0, senderKeyID, receipientKeyID, nextDH, ctr, encryptedMsg);
// Calculate T hash.
byte[] sendingMACKey = encryptionKeys.getSendingMACKey();
logger.finest("Transforming T to byte[] to calculate it's HmacSHA1.");
byte[] serializedT;
try {
serializedT = SerializationUtils.toByteArray(t);
} catch (IOException e) {
throw new OtrException(e);
}
byte[] mac =
otrCryptoEngine.sha1Hmac(
serializedT, sendingMACKey, SerializationConstants.TYPE_LEN_MAC);
// Get old MAC keys to be revealed.
byte[] oldKeys = this.collectOldMacKeys();
DataMessage m = new DataMessage(t, mac, oldKeys);
try {
return SerializationUtils.toString(m);
} catch (IOException e) {
throw new OtrException(e);
}
case FINISHED:
this.lastSentMessage = msgText;
showError(
"Your message to "
+ sessionID.getUserID()
+ " was not sent. Either end your private conversation, or restart it.");
return null;
default:
logger.finest("Uknown message state, not processing.");
return msgText;
}
}
