private void SendSessionKey(byte[] session_key)
{
try {
//step1 XOR with session_id
byte[] working_data = new byte[session_key.Length];
byte[] session_id = CalcSessionID();
Array.Copy(session_key, 0, working_data, 0, session_key.Length);
for (int i = 0; i < session_id.Length; i++)
{
working_data[i] ^= session_id[i];
}
//step2 decrypts with RSA
RSAPublicKey first_encryption;
RSAPublicKey second_encryption;
SSHServerInfo si = _cInfo._serverinfo;
int first_key_bytelen, second_key_bytelen;
if (si.server_key_bits < si.host_key_bits)
{
first_encryption = new RSAPublicKey(si.server_key_public_exponent, si.server_key_public_modulus);
second_encryption = new RSAPublicKey(si.host_key_public_exponent, si.host_key_public_modulus);
first_key_bytelen = (si.server_key_bits + 7) / 8;
second_key_bytelen = (si.host_key_bits + 7) / 8;
}
else
{
first_encryption = new RSAPublicKey(si.host_key_public_exponent, si.host_key_public_modulus);
second_encryption = new RSAPublicKey(si.server_key_public_exponent, si.server_key_public_modulus);
first_key_bytelen = (si.host_key_bits + 7) / 8;
second_key_bytelen = (si.server_key_bits + 7) / 8;
}
Rng rng = RngManager.GetSecureRng();
BigInteger first_result = RSAUtil.PKCS1PadType2(new BigInteger(working_data), first_key_bytelen, rng).modPow(first_encryption.Exponent, first_encryption.Modulus);
BigInteger second_result = RSAUtil.PKCS1PadType2(first_result, second_key_bytelen, rng).modPow(second_encryption.Exponent, second_encryption.Modulus);
//output
SSH1DataWriter writer = new SSH1DataWriter();
writer.WriteByte((byte)_cInfo._algorithmForTransmittion);
writer.Write(si.anti_spoofing_cookie);
writer.WriteBigInteger(second_result);
writer.WriteInt32(0); //protocol flags
//send
TraceTransmissionEvent(PacketType.SSH_CMSG_SESSION_KEY, "sent encrypted session-keys");
SSH1Packet packet = SSH1Packet.FromPlainPayload(PacketType.SSH_CMSG_SESSION_KEY, writer.ToByteArray());
packet.WriteTo(_stream);
_sessionID = session_id;
}
catch (Exception e) {
if (e is IOException)
{
throw (IOException)e;
}
else
{
string t = e.StackTrace;
throw new SSHException(e.Message); //IOException以外はみなSSHExceptionにしてしまう
}
}
}