public static bool IsSignatureVerified(AKEKeys ake_keys, DHKeyPair key_pair, byte[] their_public_key_mpi_byte_array, byte[] encrypted_signature_byte_array,
byte[] hashed_encrypted_signature_byte_array, bool is_top_half_keys, ref UInt32 public_key_id, ref byte[] dsa_public_key_byte_array_encoded)
{
if (encrypted_signature_byte_array == null || encrypted_signature_byte_array.Length < 1)
throw new ArgumentException("IsSignatureVerified: Encrypted signature byte array cannot be null/empty");
if (hashed_encrypted_signature_byte_array == null || hashed_encrypted_signature_byte_array.Length < 1)
throw new ArgumentException("IsSignatureVerified: The hashed encrypted byte array cannot be null/empty");
if (ake_keys == null)
throw new ArgumentException("IsSignatureVerified: The AKE keys cannot be null");
bool _is_hash_verified = false;
if (is_top_half_keys == true)
_is_hash_verified = IsHashSignatureVerified(ake_keys.GetMACKey2(), encrypted_signature_byte_array, hashed_encrypted_signature_byte_array);
else
_is_hash_verified = IsHashSignatureVerified(ake_keys.GetMACKey4(), encrypted_signature_byte_array, hashed_encrypted_signature_byte_array);
if (_is_hash_verified == false)
return false;
if (IsEncryptedSignatureVerified(ake_keys, key_pair, their_public_key_mpi_byte_array,
encrypted_signature_byte_array, 0, is_top_half_keys, ref public_key_id, ref dsa_public_key_byte_array_encoded) == false)
return false;
return true;
}
public AKEKeys ComputeKeys(DHKeyPair my_key_pair, BigInteger public_key)
{
if (Utility.IsValidPublicKey(public_key) == false)
throw new ArgumentException("AKEKeysManager:Public key is invalid");
if (my_key_pair == null)
throw new ArgumentException("AKEKeysManager: My Key Pair cannot be null");
if (my_key_pair.GetPrivateKey() < 1)
throw new ArgumentException("AKEKeysManager: Private key in my_key_pair value cannot be less than 0");
if (public_key < 1)
throw new ArgumentException("AKEKeysManager: Public key value cannot be less than 0");
_ake_keys = new AKEKeys();
_secret = Utility.ComputeSecret(my_key_pair, public_key, OTRConstants.RFC_3526_GENERATOR, OTRConstants.RFC_3526_PRIME_MODULO());
Utility.SetSecByteMpi(_secret, ref _sec_data_byte_array_mpi);
_ake_keys.SetSecData(_sec_data_byte_array_mpi);
ComputeSessionIDByte();
ComputeEncryptionKeysBytes();
ComputeMACKeysBytes();
return _ake_keys;
}
public void ComputeSignature(AKEKeys ake_keys, byte[] my_public_key_mpi_byte_array, byte[] key_id_byte_array, byte[] their_public_key_mpi_byte_array, UInt64 aes_counter, bool is_top_half_keys)
{
byte[] hashed_m_byte_array_data = ComputeM(ake_keys, my_public_key_mpi_byte_array, their_public_key_mpi_byte_array, _dsa_public_key_bytes_encoded, key_id_byte_array, is_top_half_keys);
byte[] _x_byte_array_data = ComputeX(_dsa_signer, _dsa_public_key_bytes_encoded, key_id_byte_array, hashed_m_byte_array_data);
ComputeSignatureValues(ake_keys, _x_byte_array_data,aes_counter,is_top_half_keys);
}
private void ComputeSignatureValues(AKEKeys ake_keys, byte[] x_byte_array_data, UInt64 aes_counter, bool is_top_half_keys)
{
if (ake_keys == null)
throw new ArgumentException("ComputeSignatureValues: AKE keys object should not be null");
if (is_top_half_keys == true && (ake_keys.GetAESKey1() == null || ake_keys.GetAESKey1().Length < 1))
throw new ArgumentException("ComputeSignatureValues: The AKE AES key 1 should not be null/empty");
if (is_top_half_keys == false && (ake_keys.GetAESKey2() == null || ake_keys.GetAESKey2().Length < 1))
throw new ArgumentException("ComputeSignatureValues: The AKE AES key 2 should not be null/empty");
if (x_byte_array_data == null || x_byte_array_data.Length < 1)
throw new ArgumentException("ComputeSignatureValues: The x_byte_array_data cannot be null/empty");
if (aes_counter < 0)
throw new ArgumentException("ComputeSignatureValues: The aes counter value cannot be less than zero");
byte[] _encrypted_signature_byte_array = null;
if (is_top_half_keys == true)
_encrypted_signature_byte_array = Utility.AESGetEncrypt(ake_keys.GetAESKey1(), x_byte_array_data, aes_counter);
else
_encrypted_signature_byte_array = Utility.AESGetEncrypt(ake_keys.GetAESKey2(), x_byte_array_data, aes_counter);
try
{
Utility.EncodeOTRDataBE(_encrypted_signature_byte_array, ref _encoded_encrypted_signature_byte_array);
}
catch (Exception ex)
{
throw new InvalidDataException("ComputeSignatureValues:" + ex.ToString());
}
if (is_top_half_keys == true && (ake_keys.GetMACKey2() == null || ake_keys.GetMACKey2().Length < 1))
throw new InvalidDataException("ComputeSignatureValues: The AKE MAC key 2 should not be null/empty");
if (is_top_half_keys == false && (ake_keys.GetMACKey4() == null || ake_keys.GetMACKey4().Length < 1))
throw new InvalidDataException("ComputeSignatureValues: The AKE MAC key 4 should not be null/empty");
if (is_top_half_keys == true)
_hashed_encoded_encrypted_byte_array = Utility.SHA256GetKeyedHash(ake_keys.GetMACKey2(), _encoded_encrypted_signature_byte_array);
else
_hashed_encoded_encrypted_byte_array = Utility.SHA256GetKeyedHash(ake_keys.GetMACKey4(), _encoded_encrypted_signature_byte_array);
_truncated_hash_signature = new byte[OTRConstants.MAC_SIGNATURE_LENGTH_BITS / 8];
Buffer.BlockCopy(_hashed_encoded_encrypted_byte_array, 0, _truncated_hash_signature, 0, _truncated_hash_signature.Length);
}
private static bool IsEncryptedSignatureVerified(AKEKeys ake_keys, DHKeyPair key_pair, byte[] their_public_key_mpi_byte_array,
byte[] encryted_byte_array, UInt64 counter, bool is_top_half_keys,ref UInt32 public_key_id, ref byte[] dsa_public_key_byte_array_encoded)
{
int _next_start_index = -1;
bool _is_verified = false;
byte[] _decrypted_x_data_array = null;
byte[] _hashed_m_data_signature = null;
byte[] _dh_kid_bytes = null;
byte[] _temp_byte_array = null;
byte[] _dsa_public_key_type = null;
byte[] _dsa_public_key_param_p_mpi = null;
byte[] _dsa_public_key_param_q_mpi = null;
byte[] _dsa_public_key_param_g_mpi = null;
byte[] _dsa_public_key_param_y_mpi = null;
try
{
/*get encrypted signature bytes*/
_next_start_index = 0;
_temp_byte_array = null;
_next_start_index = Utility.DecodeDataFromBytesBE(encryted_byte_array, _next_start_index, ref _temp_byte_array);
if (_temp_byte_array == null || _temp_byte_array.Length < 1)
throw new InvalidDataException("IsEncryptedSignatureVerified: The decoded Encrypted OTR Data type byte array cannot be null/empty");
if (is_top_half_keys == true)
_decrypted_x_data_array = Utility.AESGetDecrypt(ake_keys.GetAESKey1(), _temp_byte_array, counter);
else
_decrypted_x_data_array = Utility.AESGetDecrypt(ake_keys.GetAESKey2(), _temp_byte_array, counter);
if (_decrypted_x_data_array == null || _decrypted_x_data_array.Length < 1)
throw new InvalidDataException("IsEncryptedSignatureVerified: The decrypted byte array cannot be null/empty");
/*get public key parameter bytes*/
_next_start_index = 0;
_temp_byte_array = null;
//get public key type
int _pub_key_start_index = _next_start_index;
_next_start_index = Utility.DecodeShortFromBytes(_decrypted_x_data_array, _next_start_index, ref _dsa_public_key_type);
if (_dsa_public_key_type == null || _dsa_public_key_type.Length < 1)
throw new InvalidDataException("IsEncryptedSignatureVerified: The decoded DSA public key type byte array cannot be null/empty");
if (BitConverter.ToUInt16(_dsa_public_key_type,0) != OTRConstants.DSA_PUB_KEY_TYPE)
throw new InvalidDataException("IsEncryptedSignatureVerified: The DSA public key type is invalid");
//get MPI encoded DSA public key parameters
_next_start_index = Utility.DecoupleMpiFromBytes(_decrypted_x_data_array, _next_start_index, ref _dsa_public_key_param_p_mpi);
_next_start_index = Utility.DecoupleMpiFromBytes(_decrypted_x_data_array, _next_start_index, ref _dsa_public_key_param_q_mpi);
_next_start_index = Utility.DecoupleMpiFromBytes(_decrypted_x_data_array, _next_start_index, ref _dsa_public_key_param_g_mpi);
_next_start_index = Utility.DecoupleMpiFromBytes(_decrypted_x_data_array, _next_start_index, ref _dsa_public_key_param_y_mpi);
int _pub_key_end_index = _next_start_index;
//get the whole encoded DSA key
dsa_public_key_byte_array_encoded = new byte[_pub_key_end_index - _pub_key_start_index];
Buffer.BlockCopy(_decrypted_x_data_array, _pub_key_start_index, dsa_public_key_byte_array_encoded, 0, dsa_public_key_byte_array_encoded.Length);
DsaPublicKeyParameters _dsa_public_key_params = GetDSAPublicKeyParams(_dsa_public_key_param_p_mpi, _dsa_public_key_param_q_mpi, _dsa_public_key_param_g_mpi, _dsa_public_key_param_y_mpi);
/*Get DH Key ID bytes*/
_next_start_index = Utility.DecodeIntFromBytes(_decrypted_x_data_array, _next_start_index, ref _dh_kid_bytes);
if (_dh_kid_bytes == null || _dh_kid_bytes.Length < 1)
throw new InvalidDataException("IsEncryptedSignatureVerified: The decoded Key ID OTR Int type byte array cannot be null/empty");
public_key_id = BitConverter.ToUInt32(_dh_kid_bytes, 0);
/*Get Signed M_b*/
_hashed_m_data_signature = new byte[_decrypted_x_data_array.Length - _next_start_index];
Buffer.BlockCopy(_decrypted_x_data_array, _next_start_index, _hashed_m_data_signature, 0, _hashed_m_data_signature.Length);
if (_hashed_m_data_signature == null || _hashed_m_data_signature.Length < 1)
throw new InvalidDataException("IsEncryptedSignatureVerified: The extracted Signed byte array, M_b, cannot be null/empty");
/*Decode r and s */
_next_start_index = 0;
byte[] _decoded_signature_r_byte_array = null;
byte[] _decoded_signature_s_byte_array = null;
_next_start_index = Utility.DecodeMacFromBytesBE(_hashed_m_data_signature, _next_start_index, ref _decoded_signature_r_byte_array);
_next_start_index = Utility.DecodeMacFromBytesBE(_hashed_m_data_signature, _next_start_index, ref _decoded_signature_s_byte_array);
if (_decoded_signature_r_byte_array == null || _decoded_signature_r_byte_array.Length < 1)
throw new InvalidDataException("IsEncryptedSignatureVerified: The decoded DSA signature parameter 'r' byte array cannot be null/empty");
if (_decoded_signature_s_byte_array == null || _decoded_signature_s_byte_array.Length < 1)
throw new InvalidDataException("IsEncryptedSignatureVerified: The decoded DSA signature parameter 's' byte array cannot be null/empty");
/*Verify Signature*/
byte[] _hashed_m_data_byte_array = ComputeM(ake_keys, their_public_key_mpi_byte_array, key_pair.GetPublicKeyMpiBytes(), dsa_public_key_byte_array_encoded, _dh_kid_bytes, is_top_half_keys);
_is_verified = DSASigner.VerifySignature(_dsa_public_key_params, _hashed_m_data_byte_array, _decoded_signature_r_byte_array, _decoded_signature_s_byte_array);
}
catch (Exception ex)
{
_is_verified = false;
throw new InvalidDataException("IsEncryptedVerified:" + ex.ToString());
}
return _is_verified;
}
private static byte[] ComputeM(AKEKeys ake_keys, byte[] my_public_key_mpi_byte_array, byte[] their_public_key_mpi_byte_array, byte[] dsa_public_key_bytes_encoded, byte[] key_id_byte_array, bool is_top_half_keys)
{
if (my_public_key_mpi_byte_array == null || my_public_key_mpi_byte_array.Length < 1)
throw new ArgumentException("ComputeM: My public key mpi byte array cannot be null/empty");
if (their_public_key_mpi_byte_array == null || their_public_key_mpi_byte_array.Length < 1)
throw new ArgumentException("ComputeM: Their public key mpi byte array cannot be null/empty");
if (key_id_byte_array == null || key_id_byte_array.Length < 1)
throw new ArgumentException("ComputeM: The id byte array cannot be null/empty");
if (dsa_public_key_bytes_encoded == null || dsa_public_key_bytes_encoded.Length < 1)
throw new ArgumentException("ComputeM: The encoded DSA public key byte array cannot be null/empty");
if (ake_keys == null)
throw new ArgumentException("ComputeM: AKE keys object cannot be null");
byte[] _encoded_key_id_byte_array = null;
try
{
Utility.EncodeOTRInt(key_id_byte_array, ref _encoded_key_id_byte_array);
}
catch (Exception ex)
{
throw new InvalidDataException("ComputeM:" + ex.ToString());
}
int _m_data_array_length = _encoded_key_id_byte_array.Length + my_public_key_mpi_byte_array.Length +
their_public_key_mpi_byte_array.Length +
dsa_public_key_bytes_encoded.Length;
byte [] _m_data_array = new byte[_m_data_array_length];
Buffer.BlockCopy(my_public_key_mpi_byte_array, 0, _m_data_array, 0, my_public_key_mpi_byte_array.Length);
Buffer.BlockCopy(their_public_key_mpi_byte_array, 0, _m_data_array, my_public_key_mpi_byte_array.Length, their_public_key_mpi_byte_array.Length);
Buffer.BlockCopy(dsa_public_key_bytes_encoded, 0, _m_data_array, my_public_key_mpi_byte_array.Length + their_public_key_mpi_byte_array.Length, dsa_public_key_bytes_encoded.Length);
Buffer.BlockCopy(_encoded_key_id_byte_array, 0, _m_data_array, my_public_key_mpi_byte_array.Length + their_public_key_mpi_byte_array.Length + dsa_public_key_bytes_encoded.Length, _encoded_key_id_byte_array.Length);
if (is_top_half_keys == true && (ake_keys.GetMACKey1() == null || ake_keys.GetMACKey1().Length < 1))
throw new ArgumentException("ComputeM: The AKE MAC key 1 cannot be null/empty");
if (is_top_half_keys == false && (ake_keys.GetMACKey3() == null || ake_keys.GetMACKey3().Length < 1))
throw new ArgumentException("ComputeM: The AKE MAC key 3 cannot be null/empty");
if (is_top_half_keys == true)
return Utility.SHA256GetKeyedHash(ake_keys.GetMACKey1(),_m_data_array);
else
return Utility.SHA256GetKeyedHash(ake_keys.GetMACKey3(), _m_data_array);
}
private void CloseOTRSession(string session_closed_message)
{
DebugPrint("Ending OTR session");
_otr_event_args = new OTREventArgs();
_otr_event_args.SetMessage(session_closed_message);
_otr_event_args.SetOTREvent(OTR_EVENT.CLOSED);
DoOTREvent(_otr_event_args);
_message_state = OTR_MESSAGE_STATE.MSG_STATE_PLAINTEXT;
_message_manager = null;
_ake_keys_manager = null;
_dsa_signer = null;
_signature_manager = null;
_smp_manager = null;
_ake_keys = null;
_my_unique_id = string.Empty;
_my_buddy_unique_id = string.Empty;
_otr_fragment_object = null;
EndSMPSession();
}
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 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);
}