private ServerDHInnerData DecryptServerDHInnerData(byte[] encryptedAnswer, byte[] tmpAesKey, byte[] tmpAesIV)
{
/* encrypted_answer := AES256_ige_encrypt (answer_with_hash, tmp_aes_key, tmp_aes_iv);
* here, tmp_aes_key is a 256-bit key, and tmp_aes_iv is a 256-bit initialization vector.
* The same as in all the other instances that use AES encryption,
* the encrypted data is padded with random bytes to a length divisible by 16 immediately prior to encryption.
*/
// Decrypting.
byte[] answerWithHash = _encryptionServices.Aes256IgeDecrypt(encryptedAnswer, tmpAesKey, tmpAesIV);
if ((answerWithHash.Length % 16) != 0)
{
throw new InvalidResponseException("Decrypted ServerDHInnerData with hash has invalid length.");
}
var answerHash = new byte[HashLength];
ServerDHInnerData serverDHInnerData;
using (var streamer = new TLStreamer(answerWithHash))
{
streamer.Read(answerHash, 0, answerHash.Length);
serverDHInnerData = _tlRig.Deserialize <ServerDHInnerData>(streamer);
}
// Checking the hash.
byte[] serverDHInnerDataBytes = _tlRig.Serialize(serverDHInnerData);
byte[] serverDHInnerDataBytesHash = ComputeSHA1(serverDHInnerDataBytes);
if (!serverDHInnerDataBytesHash.SequenceEqual(answerHash))
{
throw new InvalidResponseException("Decrypted ServerDHInnerData hash is invalid.");
}
return(serverDHInnerData);
}
public IMessage DecodeEncryptedMessage(byte[] messageBytes, byte[] authKey, Sender sender, out UInt64 salt, out UInt64 sessionId)
{
Argument.IsNotNull(() => authKey);
Argument.IsNotNull(() => messageBytes);
ulong providedAuthKeyId = ComputeAuthKeyId(authKey);
var encryptedData = new byte[messageBytes.Length - EncryptedOuterHeaderLength];
Int128 msgKey;
using (var streamer = new TLStreamer(messageBytes))
{
// Reading header.
ulong authKeyId = streamer.ReadUInt64();
if (authKeyId != providedAuthKeyId)
{
throw new InvalidAuthKey(string.Format("Message encrypted with auth key with id={0}, but auth key provided for decryption with id={1}.", authKeyId,
providedAuthKeyId));
}
msgKey = streamer.ReadInt128();
// Reading encrypted data.
streamer.Read(encryptedData, 0, encryptedData.Length);
}
// Decrypting.
byte[] aesKey, aesIV;
ComputeAesKeyAndIV(authKey, msgKey, out aesKey, out aesIV, sender);
byte[] innerDataWithPadding = _encryptionServices.Aes256IgeDecrypt(encryptedData, aesKey, aesIV);
Int32 msgDataLength;
UInt64 msgId;
UInt32 seqno;
Object body;
using (var streamer = new TLStreamer(innerDataWithPadding))
{
salt = streamer.ReadUInt64();
sessionId = streamer.ReadUInt64();
msgId = streamer.ReadUInt64();
seqno = streamer.ReadUInt32();
msgDataLength = streamer.ReadInt32();
body = _tlRig.Deserialize(streamer);
}
int innerDataLength = EncryptedInnerHeaderLength + msgDataLength;
// When an encrypted message is received, it must be checked that
// msg_key is in fact equal to the 128 lower-order bits
// of the SHA1 hash of the previously encrypted portion.
Int128 expectedMsgKey = ComputeMsgKey(new ArraySegment <byte>(innerDataWithPadding, 0, innerDataLength));
if (msgKey != expectedMsgKey)
{
throw new InvalidMessageException(string.Format("Expected message key to be {0}, but actual is {1}.", expectedMsgKey, msgKey));
}
return(new Message(msgId, seqno, body));
}
/// <summary>
/// Initializes a new instance of the <see cref="EncryptedMessage" /> class from a whole message bytes, which contain
/// encrypted data.
/// </summary>
/// <param name="authKey">
/// Authorization Key a 2048-bit key shared by the client device and the server, created upon user
/// registration directly on the client device be exchanging Diffie-Hellman keys, and never transmitted over a network.
/// Each authorization key is user-specific. There is nothing that prevents a user from having several keys (that
/// correspond to “permanent sessions” on different devices), and some of these may be locked forever in the event the
/// device is lost.
/// </param>
/// <param name="messageBytes">Whole message bytes, which contain encrypted data.</param>
/// <param name="sender">Sender of the message.</param>
/// <param name="hashServices">Hash services.</param>
/// <param name="encryptionServices">Encryption services.</param>
public EncryptedMessage([NotNull] byte[] authKey, [NotNull] byte[] messageBytes, Sender sender, [NotNull] IHashServices hashServices,
[NotNull] IEncryptionServices encryptionServices)
{
Argument.IsNotNull(() => authKey);
Argument.IsNotNull(() => messageBytes);
Argument.IsNotNull(() => hashServices);
Argument.IsNotNull(() => encryptionServices);
ulong authKeyId = ComputeAuthKeyId(authKey, hashServices);
_messageBytes = messageBytes;
_length = _messageBytes.Length;
var encryptedData = new byte[_length - OuterHeaderLength];
using (var streamer = new TLStreamer(_messageBytes))
{
// Reading header.
_authKeyId = streamer.ReadUInt64();
if (_authKeyId != authKeyId)
{
throw new InvalidAuthKey(string.Format("Message encrypted with auth key with id={0}, but auth key provided for decryption with id={1}.", _authKeyId,
authKeyId));
}
_msgKey = streamer.ReadInt128();
// Reading encrypted data.
streamer.Read(encryptedData, 0, encryptedData.Length);
}
// Decrypting.
byte[] aesKey, aesIV;
ComputeAesKeyAndIV(authKey, _msgKey, out aesKey, out aesIV, hashServices, sender);
byte[] innerDataWithPadding = encryptionServices.Aes256IgeDecrypt(encryptedData, aesKey, aesIV);
using (var streamer = new TLStreamer(innerDataWithPadding))
{
_salt = streamer.ReadUInt64();
_sessionId = streamer.ReadUInt64();
_messageId = streamer.ReadUInt64();
_seqNumber = streamer.ReadUInt32();
_messageDataLength = streamer.ReadInt32();
_messageData = streamer.ReadBytes(_messageDataLength);
}
int innerDataLength = InnerHeaderLength + _messageDataLength;
// When an encrypted message is received, it must be checked that
// msg_key is in fact equal to the 128 lower-order bits
// of the SHA1 hash of the previously encrypted portion.
var msgKey = ComputeMsgKey(new ArraySegment <byte>(innerDataWithPadding, 0, innerDataLength), hashServices);
if (_msgKey != msgKey)
{
throw new InvalidMessageException(string.Format("Expected message key to be {0}, but actual is {1}.", _msgKey, msgKey));
}
}