private byte[] GenerateSessionKey()
{
//session key(256bits)
byte[] session_key = new byte[32];
RngManager.GetSecureRng().GetBytes(session_key);
return(session_key);
}
// Derived class can override this method to modify the buffer.
public virtual DataFragment Close(Cipher cipher, MAC mac, int sequence)
{
if (!_isOpen)
{
throw new SSHException("internal state error");
}
int blocksize = cipher == null ? 8 : cipher.BlockSize;
int payloadLength = _writer.Length - (SEQUENCE_MARGIN + LENGTH_MARGIN + PADDING_MARGIN);
int paddingLength = 11 - payloadLength % blocksize;
while (paddingLength < 4)
{
paddingLength += blocksize;
}
int packetLength = PADDING_MARGIN + payloadLength + paddingLength;
int imageLength = packetLength + LENGTH_MARGIN;
//fill padding
byte[] tmp = new byte[4];
Rng rng = RngManager.GetSecureRng();
for (int i = 0; i < paddingLength; i += 4)
{
rng.GetBytes(tmp);
_writer.Write(tmp);
}
//manipulate stream
byte[] rawbuf = _writer.UnderlyingBuffer;
SSHUtil.WriteIntToByteArray(rawbuf, 0, sequence);
SSHUtil.WriteIntToByteArray(rawbuf, SEQUENCE_MARGIN, packetLength);
rawbuf[SEQUENCE_MARGIN + LENGTH_MARGIN] = (byte)paddingLength;
//mac
if (mac != null)
{
byte[] macCode = mac.ComputeHash(rawbuf, 0, packetLength + LENGTH_MARGIN + SEQUENCE_MARGIN);
Array.Copy(macCode, 0, rawbuf, packetLength + LENGTH_MARGIN + SEQUENCE_MARGIN, macCode.Length);
imageLength += macCode.Length;
}
//encrypt
if (cipher != null)
{
cipher.Encrypt(rawbuf, SEQUENCE_MARGIN, packetLength + LENGTH_MARGIN, rawbuf, SEQUENCE_MARGIN);
}
_dataFragment.Init(rawbuf, SEQUENCE_MARGIN, imageLength);
_isOpen = false;
return(_dataFragment);
}
//Tutorial: Generating a new DSA key for user authentication
private static void GenerateDSAKey()
{
//DSA KEY GENERATION TEST
byte[] testdata = Encoding.ASCII.GetBytes("CHRISTIAN VIERI");
DSAKeyPair kp = DSAKeyPair.GenerateNew(2048, RngManager.GetSecureRng());
//sign and verify test
byte[] sig = kp.Sign(testdata);
kp.Verify(sig, testdata);
//export / import test
SSH2UserAuthKey key = new SSH2UserAuthKey(kp);
key.WritePublicPartInOpenSSHStyle(new FileStream("newdsakey.pub", FileMode.Create));
key.WritePrivatePartInSECSHStyleFile(new FileStream("newrsakey.bin", FileMode.Create), "comment", "passphrase");
//read test
SSH2UserAuthKey newpk = SSH2UserAuthKey.FromSECSHStyleFile("newrsakey.bin", "passphrase");
}
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
}
}
}
