private static void ComputeAesKeyAndIV(byte[] authKey, Int128 msgKey, out byte[] aesKey, out byte[] aesIV, IHashServices hashServices, Sender sender)
{
// x = 0 for messages from client to server and x = 8 for those from server to client.
int x;
switch (sender)
{
case Sender.Client:
x = 0;
break;
case Sender.Server:
x = 8;
break;
default:
throw new ArgumentOutOfRangeException("sender");
}
byte[] msgKeyBytes = msgKey.ToBytes();
byte[] buffer = _aesKeyAndIVComputationBuffer ?? (_aesKeyAndIVComputationBuffer = new byte[32 + MsgKeyLength]);
// sha1_a = SHA1 (msg_key + substr (auth_key, x, 32));
Buffer.BlockCopy(msgKeyBytes, 0, buffer, 0, MsgKeyLength);
Buffer.BlockCopy(authKey, x, buffer, MsgKeyLength, 32);
byte[] sha1A = hashServices.ComputeSHA1(buffer);
// sha1_b = SHA1 (substr (auth_key, 32+x, 16) + msg_key + substr (auth_key, 48+x, 16));
Buffer.BlockCopy(authKey, 32 + x, buffer, 0, 16);
Buffer.BlockCopy(msgKeyBytes, 0, buffer, 16, MsgKeyLength);
Buffer.BlockCopy(authKey, 48 + x, buffer, 16 + MsgKeyLength, 16);
byte[] sha1B = hashServices.ComputeSHA1(buffer);
// sha1_с = SHA1 (substr (auth_key, 64+x, 32) + msg_key);
Buffer.BlockCopy(authKey, 64 + x, buffer, 0, 32);
Buffer.BlockCopy(msgKeyBytes, 0, buffer, 32, MsgKeyLength);
byte[] sha1C = hashServices.ComputeSHA1(buffer);
// sha1_d = SHA1 (msg_key + substr (auth_key, 96+x, 32));
Buffer.BlockCopy(msgKeyBytes, 0, buffer, 0, MsgKeyLength);
Buffer.BlockCopy(authKey, 96 + x, buffer, MsgKeyLength, 32);
byte[] sha1D = hashServices.ComputeSHA1(buffer);
// aes_key = substr (sha1_a, 0, 8) + substr (sha1_b, 8, 12) + substr (sha1_c, 4, 12);
aesKey = new byte[32];
Buffer.BlockCopy(sha1A, 0, aesKey, 0, 8);
Buffer.BlockCopy(sha1B, 8, aesKey, 8, 12);
Buffer.BlockCopy(sha1C, 4, aesKey, 20, 12);
// aes_iv = substr (sha1_a, 8, 12) + substr (sha1_b, 0, 8) + substr (sha1_c, 16, 4) + substr (sha1_d, 0, 8);
aesIV = new byte[32];
Buffer.BlockCopy(sha1A, 8, aesIV, 0, 12);
Buffer.BlockCopy(sha1B, 0, aesIV, 12, 8);
Buffer.BlockCopy(sha1C, 16, aesIV, 20, 4);
Buffer.BlockCopy(sha1D, 0, aesIV, 24, 8);
}
/// <summary>
/// Calculates fingerprint for a public RSA key.
/// </summary>
/// <param name="keyData">Bare serialized type of a constructor: "rsa_public_key n:string e:string = RSAPublicKey".</param>
/// <returns>Returns fingerprint as lower 64 bits of the SHA1(RSAPublicKey).</returns>
public ulong ComputeFingerprint(byte[] keyData)
{
byte[] hash = _hashServices.ComputeSHA1(keyData);
return(hash.ToUInt64(hash.Length - 8));
}
private byte[] ComputeSHA1(byte[] data)
{
return(_hashServices.ComputeSHA1(data));
}
private ulong ComputeAuthKeyId(byte[] authKey, IHashServices hashServices)
{
byte[] authKeySHA1 = hashServices.ComputeSHA1(authKey);
return(authKeySHA1.ToUInt64(authKeySHA1.Length - 8, true));
}
private static Int128 ComputeMsgKey(ArraySegment <byte> bytes, [NotNull] IHashServices hashServices)
{
byte[] innerDataSHA1 = hashServices.ComputeSHA1(bytes);
return(innerDataSHA1.ToInt128(innerDataSHA1.Length - 16, true));
}
