private void ProcessSignatureMessage(OTRMessage otr_message)
{
DebugPrint("Received Signature Message");
_otr_event_args = new OTREventArgs();
if (_authentication_state != OTR_AUTH_STATE.AUTH_STATE_AWAITING_SIG)
{
OTRError("ProcessSignatureMessage: OTR Engine is not in the AUTH_STATE_AWAITING_SIG state",
"ProcessSignatureMessage: OTR Engine is not in the AUTH_STATE_AWAITING_SIG state",
null);
return;
}
if (otr_message.GetEncodedEncryptedSignature() == null || otr_message.GetEncodedEncryptedSignature().Length < 1)
{
OTRError("ProcessSignatureMessage: The encoded encrypted signature byte array cannot be null/empty", null,
"OTR Failed. Unexpected error");
return;
}
if (otr_message.GetMacDSignature() == null || otr_message.GetMacDSignature().Length < 1)
{
OTRError("ProcessSignatureMessage: The MAC'd signature byte array cannot be null/empty", null,
"OTR Failed. Unexpected error");
return;
}
_otr_event_args.SetOTREvent(OTR_EVENT.ERROR);
byte[] dsa_public_key_byte_array_encoded = null;
bool _is_sig_verified = SignatureManager.IsSignatureVerified(_ake_keys, _otr_session_object.GetMyRecentDHKeyPair(), _otr_session_object.GetBuddyRecentPublicKeyMpi(),
otr_message.GetEncodedEncryptedSignature(), otr_message.GetMacDSignature(), false, ref _temp_int_32_val, ref dsa_public_key_byte_array_encoded);
if (_otr_session_object.IsComputeBuddyFingerPrint(dsa_public_key_byte_array_encoded) == false)
{
OTRError("ProcessSignatureMessage:" + _my_buddy_unique_id + "'s DSA public key fingerprint computation failed",
"ProcessSignatureMessage:" + _my_buddy_unique_id + "'s DSA public key fingerprint computation failed",
null);
_authentication_state = OTR_AUTH_STATE.AUTH_STATE_NONE;
return;
}
if (_is_sig_verified != true)
{
OTRError("ProcessSignatureMessage:" + _my_buddy_unique_id + "'s signature verification failed",
"ProcessSignatureMessage:" + _my_buddy_unique_id + "'s signature verification failed",
null);
_authentication_state = OTR_AUTH_STATE.AUTH_STATE_NONE;
return;
}
/* Inform client of OTR readiness */
_otr_session_object.SetFirstBuddyPublicKeyID(_temp_int_32_val);
_authentication_state = OTR_AUTH_STATE.AUTH_STATE_NONE;
_message_state = OTR_MESSAGE_STATE.MSG_STATE_ENCRYPTED;
_otr_event_args.SetOTREvent(OTR_EVENT.READY);
_otr_event_args.SetMessage(_my_buddy_unique_id + "'s signature verification successful");
DoOTREvent(_otr_event_args);
}
private void ProcessDataMessage(OTRMessage otr_message)
{
DebugPrint("Received Data Message");
if (_message_state != OTR_MESSAGE_STATE.MSG_STATE_ENCRYPTED)
{
OTRError("ProcessDataMessage: OTR Engine is not in the MSG_STATE_ENCRYPTED state",
"ProcessDataMessage: OTR Engine is not in the MSG_STATE_ENCRYPTED state",
null);
return;
}
/*Compute new keys */
DataExchangeKeys _data_exchange_keys = _otr_session_object.GetDataExchangeKeys(otr_message.GetRecipientKeyId(),
_otr_message.GetSenderKeyId(), _otr_message.GetNextDHPublicKeyMpi(), _re_key_my_dh_keys);
string _error_string = null;
if (_data_exchange_keys == null)
{
if (otr_message.GetFlags() != OTRConstants.IGNORE_UNREADABLE)
_error_string = "You transmitted an unreadable encrypted message";
OTRError("ProcessDataMessage: Data exchange keys are null",
"ProcessDataMessage: Data exchange keys are null",
_error_string);
return;
}
/* Compute hash with MAC receiving key */
_temp_buffer = Utility.SHA1GetKeyedHash(_data_exchange_keys.GetMACKeyRecv(), otr_message.GetBytesToAuthenticate());
/* Compare hashed MAC */
if (Utility.IsArrayEqual(_temp_buffer, otr_message.GetAuthenticationMAC()) == false)
{
if (otr_message.GetFlags() != OTRConstants.IGNORE_UNREADABLE)
_error_string = "You transmitted an unreadable encrypted message";
OTRError("Message MAC authentication failed", "Message MAC authentication failed", _error_string);
return;
}
/* Decrypt message data */
try
{
_temp_buffer = Utility.AESGetDecrypt(_data_exchange_keys.GetAESKeyRecv(),
otr_message.GetEncryptedData(), otr_message.GetCounterTopHalf());
_extra_symmetric_key_temp = _data_exchange_keys.GetAESKeyExtra();
}
catch (Exception ex)
{
if (otr_message.GetFlags() != OTRConstants.IGNORE_UNREADABLE)
_error_string = "You transmitted an unreadable encrypted message";
else
_error_string = string.Empty;
OTRError("ProcessDataMessage:Unable to decrypte message",
"ProcessDataMessage:" + ex.ToString(),
_error_string);
_otr_fragment_object = null;
return;
}
/* Process plain text */
if (_otr_fragment_object != null)
{
_otr_fragment_object.ClearCombinedString();
_otr_fragment_object = null;
}
ProcessPlaintext(_temp_buffer,_otr_message.GetOldMacKeys());
}
private void ProcessRevealSigMessage(OTRMessage otr_message)
{
DebugPrint("Received Reveal Signature Message");
_otr_event_args = new OTREventArgs();
if (_authentication_state != OTR_AUTH_STATE.AUTH_STATE_AWAITING_REVEAL_SIG)
{
OTRError("ProcessRevealSigMessage: OTR Engine is not in the AUTH_STATE_AWAITING_REVEAL_SIG state",
"ProcessRevealSigMessage: OTR Engine is not in the AUTH_STATE_AWAITING_REVEAL_SIG state",
null);
return;
}
if (otr_message.GetRevealedKey() == null || otr_message.GetRevealedKey().Length < 1)
{
OTRError("ProcessRevealSigMessage: The AES revealed key byte array cannot be null/empty", null,
"OTR Failed. Unexpected error");
return;
}
if (otr_message.GetEncodedEncryptedSignature() == null || otr_message.GetEncodedEncryptedSignature().Length < 1)
{
OTRError("ProcessRevealSigMessage: The encoded encrypted signature byte array cannot be null/empty", null,
"OTR Failed. Unexpected error");
return;
}
if (otr_message.GetMacDSignature() == null || otr_message.GetMacDSignature().Length < 1)
{
OTRError("ProcessRevealSigMessage: The MAC'd signature byte array cannot be null/empty", null,
"OTR Failed. Unexpected error");
return;
}
_otr_event_args.SetOTREvent(OTR_EVENT.ERROR);
if (_dh_commit_message == null || _dh_commit_message.GetEncryptedGxMpi() == null || _dh_commit_message.GetEncryptedGxMpi().Length < 1)
{
OTRError("ProcessRevealSigMessage: The MPI encoded encrypted public key (g^x mpi) should not be null/empty",
"ProcessRevealSigMessage: The MPI encoded encrypted public key (g^x mpi) should not be null/empty",
"OTR Failed. Unexpected error");
return;
}
if (_otr_session_object.IsSetMyBuddyFirstPublicKey(otr_message.GetRevealedKey(), _dh_commit_message.GetEncryptedGxMpi(),
_dh_commit_message.GetHashedGxMpi()) == false)
{
OTRError("ProcessRevealSigMessage: The MPI encoded decrypted public key (g^x mpi) should not be null/empty",
"ProcessRevealSigMessage: The MPI encoded decrypted public key (g^x mpi) should not be null/empty",
"OTR Failed. Unexpected error");
return;
}
_ake_keys = _ake_keys_manager.ComputeKeys(_otr_session_object.GetMyRecentDHKeyPair(), _otr_session_object.GetBuddyRecentPublicKey());
byte[] dsa_public_key_byte_array_encoded = null;
bool _is_sig_verified = SignatureManager.IsSignatureVerified(_ake_keys, _otr_session_object.GetMyRecentDHKeyPair(), _otr_session_object.GetBuddyRecentPublicKeyMpi(),
otr_message.GetEncodedEncryptedSignature(), otr_message.GetMacDSignature(), true, ref _temp_int_32_val, ref dsa_public_key_byte_array_encoded);
if (_otr_session_object.IsComputeBuddyFingerPrint(dsa_public_key_byte_array_encoded) == false)
{
OTRError("ProcessRevealSigMessage:" + _my_buddy_unique_id + "'s DSA public key fingerprint computation failed",
"ProcessRevealSigMessage:" + _my_buddy_unique_id + "'s DSA public key fingerprint computation failed",
null);
_authentication_state = OTR_AUTH_STATE.AUTH_STATE_NONE;
return;
}
if (_is_sig_verified != true)
{
OTRError("ProcessRevealSigMessage:" + _my_buddy_unique_id + "'s signature verification failed",
"ProcessRevealSigMessage:" + _my_buddy_unique_id + "'s signature verification failed",
"OTR Failed. Unexpected error");
_authentication_state = OTR_AUTH_STATE.AUTH_STATE_NONE;
return;
}
_signature_manager.ComputeSignature(_ake_keys, _otr_session_object.GetMyRecentDHKeyPair().GetPublicKeyMpiBytes(), _otr_session_object.GetMyRecentDHKeyPair().GetKeyIDBytes(),
_otr_session_object.GetBuddyRecentPublicKeyMpi(), _otr_session_object.GetCounter(), false);
//Send signature message
byte[] _dh_signature_byte_array = _message_manager.FormatSignature(_signature_manager.GetSignatureDataBytes());
DebugPrint("Sending Signature Message");
SendOTRMessage(_dh_signature_byte_array);
/* Inform client of OTR readiness */
_otr_session_object.SetFirstBuddyPublicKeyID(_temp_int_32_val);
_authentication_state = OTR_AUTH_STATE.AUTH_STATE_NONE;
_message_state = OTR_MESSAGE_STATE.MSG_STATE_ENCRYPTED;
_otr_event_args.SetOTREvent(OTR_EVENT.READY);
_otr_event_args.SetMessage(_my_buddy_unique_id + "'s signature verification successful");
DoOTREvent(_otr_event_args);
}
private void ProcessOTRMessage(string otr_message_string)
{
byte[] _message_byte_array = null;
try
{
RemoveHeaderFooter(otr_message_string, ref _message_byte_array);
if (_message_byte_array == null || _message_byte_array.Length < 1)
{
OTRError("The OTR data byte array cannot be null/empty", null, null);
return;
}
OTR_VERSION _otr_version = MessageManager.GetMessageOTRVersion(_message_byte_array);
if (_current_otr_version == OTR_VERSION.INVALID)
{
if (_otr_version == OTR_VERSION.INVALID)
{
OTRError("ProcessMessage: Received OTR version not supported.",
"ProcessMessage: Received OTR version not supported.",
null);
return;
}
else
SetOTRVersion(_otr_version);
}
else if (_current_otr_version != _otr_version)
{
OTRError("ProcessMessage: Received OTR version is invalid.",
"ProcessMessage: Received OTR version is invalid.",
null);
return;
}
if (_message_byte_array == null || _message_byte_array.Length < 1)
return;
_otr_message = _message_manager.ExtractMessage(_message_byte_array);
if (_otr_message == null)
{
OTRError("Received OTR message not properly formatted", null, "Message not properly formatted.");
return;
}
switch (_otr_message.GetMessageType())
{
case OTR_MESSAGE_TYPE.DH_COMMIT:
ProcessDHCommitMessage(_otr_message);
break;
case OTR_MESSAGE_TYPE.DH_KEY:
ProcessDHKeyMessage(_otr_message);
break;
case OTR_MESSAGE_TYPE.REVEAL_SIGNATURE:
ProcessRevealSigMessage(_otr_message);
break;
case OTR_MESSAGE_TYPE.SIGNATURE:
ProcessSignatureMessage(_otr_message);
break;
case OTR_MESSAGE_TYPE.DATA:
ProcessDataMessage(_otr_message);
break;
default:
OTRError("ProcessMessage: Invalid Message type.",
"ProcessMessage: Invalid Message type.",
"Message not properly formatted.");
break;
}
}
catch (Exception ex)
{
OTRError("ProcessOTRMesaage: Received OTR message not properly formatted",
"ProcessOTRMesaage:" + ex.ToString(),
"Message not properly formatted.");
return;
}
}
private void ProcessDHKeyMessage(OTRMessage otr_message)
{
DebugPrint("Received DH Key Message");
_otr_event_args = new OTREventArgs();
if (_authentication_state != OTR_AUTH_STATE.AUTH_STATE_AWAITING_DH_KEY)
{
OTRError("ProcessDHKeyMessage: OTR Engine is not in the AUTH_STATE_AWAITING_DH_KEY state", "ProcessDHKeyMessage: OTR Engine is not in the AUTH_STATE_AWAITING_DH_KEY state",
null);
return;
}
if (otr_message.GetGxMpi() == null || otr_message.GetGxMpi().Length < 1)
{
OTRError("ProcessDHKeyMessage: The received MPI encoded public key byte array cannot be null/empty", null,
"OTR Failed. Unexpected error");
return;
}
if (_otr_session_object.IsSetBuddyFirstPublicKey(otr_message.GetGxMpi()) == false)
{
OTRError("ProcessDHKeyMessage:" + _my_buddy_unique_id + "'s DH public key is invalid",
"ProcessDHKeyMessage:" + _my_buddy_unique_id + "'s DH public key is invalid",
"OTR Failed. Unexpected error");
return;
}
_ake_keys = _ake_keys_manager.ComputeKeys(_otr_session_object.GetMyRecentDHKeyPair(), _otr_session_object.GetBuddyRecentPublicKey());
_signature_manager.ComputeSignature(_ake_keys, _otr_session_object.GetMyRecentDHKeyPair().GetPublicKeyMpiBytes(), _otr_session_object.GetMyRecentDHKeyPair().GetKeyIDBytes(),
otr_message.GetGxMpi(), _otr_session_object.GetCounter(), true);
if (_aes_key == null || _aes_key.Length < 1)
{
OTRError("ProcessDHKeyMessage: The AES key byte array cannot be null/empty", null,
"OTR Failed. Unexpected error");
return;
}
Utility.EncodeOTRDataBE(_aes_key, ref _temp_buffer);
_temp_buffer_2 = new byte[_temp_buffer.Length + _signature_manager.GetSignatureDataLength()];
Buffer.BlockCopy(_temp_buffer, 0, _temp_buffer_2, 0, _temp_buffer.Length);
Buffer.BlockCopy(_signature_manager.GetSignatureDataBytes(), 0, _temp_buffer_2, _temp_buffer.Length, _signature_manager.GetSignatureDataLength());
byte[] _dh_reveal_byte_array = _message_manager.FormatRevealSig(_temp_buffer_2);
_authentication_state = OTR_AUTH_STATE.AUTH_STATE_AWAITING_SIG;
DebugPrint("Sending Reveal Signature Message");
SendOTRMessage(_dh_reveal_byte_array);
}
private void ProcessDHCommitMessage(OTRMessage otr_message)
{
DebugPrint("Received DH Commit Message");
if (_authentication_state != OTR_AUTH_STATE.AUTH_STATE_NONE)
{
OTRError("ProcessDHCommitMessage: OTR Engine is not in the AUTH_STATE_NONE state", "ProcessDHCommitMessage: OTR Engine is not in the AUTH_STATE_NONE state",
null);
return;
}
_dh_commit_message = otr_message;
byte[] _dh_key_message = _message_manager.FormatDHKey(_otr_session_object.GetMyRecentDHKeyPair().GetPublicKeyMpiBytes());
_authentication_state = OTR_AUTH_STATE.AUTH_STATE_AWAITING_REVEAL_SIG;
DebugPrint("Sending DH Key Message");
SendOTRMessage(_dh_key_message);
}
public OTRMessage ExtractMessage(byte[] in_message_byte_array)
{
int _next_index = 0;
_otr_message = null;
_temp_buffer = null;
_message_type = OTR_MESSAGE_TYPE.INVALID;
//get protocol version
_next_index = Utility.DecodeShortFromBytes(in_message_byte_array, _next_index, ref _temp_buffer_2);
OTR_VERSION _otr_version = Utility.GetOTRVersion(_temp_buffer_2);
if (_otr_version == OTR_VERSION.INVALID)
throw new ArgumentException("ExtractMessage:OTR version is invalid");
_otr_message = new OTRMessage();
_otr_message.SetProtocolVersion(_otr_version);
// get message type
_temp_buffer_2 = _temp_buffer = null;
_next_index = Utility.DecodeByteFromBytes(in_message_byte_array, _next_index, ref _temp_buffer_2);
_message_type = GetMessageType(_temp_buffer_2[0]);
if (_message_type == OTR_MESSAGE_TYPE.INVALID)
throw new ArgumentException("ExtractMessage:OTR message type is invalid");
_otr_message.SetMessageType(_message_type);
//get instance tags
if (_otr_version != OTR_VERSION.VERSION_2)
{
_temp_buffer_2 = _temp_buffer = null;
_next_index = Utility.DecodeIntFromBytes(in_message_byte_array, _next_index, ref _temp_buffer_2);
_otr_message.SetSenderInstanceTag(_temp_buffer_2);
if (_otr_message.GetSenderInstanceTag() < 4)
throw new ArgumentException("ExtractMessage:The Sender's instance tag cannot be less than 4");
if (_buddy_instance_tag == 0)
_buddy_instance_tag = _otr_message.GetSenderInstanceTag();
if (_buddy_instance_tag != 0 && _otr_message.GetSenderInstanceTag() != _buddy_instance_tag)
throw new ArgumentException("ExtractMessage:The Sender's instance tag is invalid");
_temp_buffer_2 = _temp_buffer = null;
_next_index = Utility.DecodeIntFromBytes(in_message_byte_array, _next_index, ref _temp_buffer_2);
_otr_message.SetReceiverInstanceTag(_temp_buffer_2);
}
if (_message_type == OTR_MESSAGE_TYPE.DATA)
return ExtractData(in_message_byte_array, _next_index);
else if (_message_type == OTR_MESSAGE_TYPE.DH_COMMIT)
return ExtractDHCommit(in_message_byte_array, _next_index);
else if (_message_type == OTR_MESSAGE_TYPE.DH_KEY)
return ExtractDHKey(in_message_byte_array, _next_index);
else if (_message_type == OTR_MESSAGE_TYPE.REVEAL_SIGNATURE)
return ExtractRevealSig(in_message_byte_array, _next_index);
else if (_message_type == OTR_MESSAGE_TYPE.SIGNATURE)
return ExtractSignature(in_message_byte_array, _next_index);
return null;
}
