private void SendKEXINIT(Mode mode) {
const string mac_algorithm = "hmac-sha1";
SSH2DataWriter wr = new SSH2DataWriter();
wr.WritePacketType(PacketType.SSH_MSG_KEXINIT);
byte[] cookie = new byte[16];
RngManager.GetSecureRng().GetBytes(cookie);
wr.Write(cookie);
wr.WriteString(GetSupportedKexAlgorithms()); // kex_algorithms
wr.WriteString(FormatHostKeyAlgorithmDescription()); // server_host_key_algorithms
wr.WriteString(FormatCipherAlgorithmDescription()); // encryption_algorithms_client_to_server
wr.WriteString(FormatCipherAlgorithmDescription()); // encryption_algorithms_server_to_client
wr.WriteString(mac_algorithm); // mac_algorithms_client_to_server
wr.WriteString(mac_algorithm); // mac_algorithms_server_to_client
wr.WriteString("none"); // compression_algorithms_client_to_server
wr.WriteString("none"); // compression_algorithms_server_to_client
wr.WriteString(""); // languages_client_to_server
wr.WriteString(""); // languages_server_to_client
wr.WriteBool(false); //Indicates whether a guessed key exchange packet follows
wr.WriteInt32(0); //reserved for future extension
_clientKEXINITPayload = wr.ToByteArray();
_status = Status.WAIT_KEXINIT;
if (_connection.IsEventTracerAvailable) {
StringBuilder bld = new StringBuilder();
bld.Append("kex_algorithm=");
bld.Append(GetSupportedKexAlgorithms());
bld.Append("; server_host_key_algorithms=");
bld.Append(FormatHostKeyAlgorithmDescription());
bld.Append("; encryption_algorithms_client_to_server=");
bld.Append(FormatCipherAlgorithmDescription());
bld.Append("; encryption_algorithms_server_to_client=");
bld.Append(FormatCipherAlgorithmDescription());
bld.Append("; mac_algorithms_client_to_server=");
bld.Append(mac_algorithm);
bld.Append("; mac_algorithms_server_to_client=");
bld.Append(mac_algorithm);
TraceTransmissionNegotiation(PacketType.SSH_MSG_KEXINIT, bld.ToString());
}
TransmitRawPayload(_clientKEXINITPayload);
}
private byte[] DeriveKey(BigInteger key, byte[] hash, char ch, int length) {
byte[] result = new byte[length];
SSH2DataWriter wr = new SSH2DataWriter();
wr.WriteBigInteger(key);
wr.Write(hash);
wr.WriteByte((byte)ch);
wr.Write(_sessionID);
byte[] h1 = new SHA1CryptoServiceProvider().ComputeHash(wr.ToByteArray());
if (h1.Length >= length) {
Array.Copy(h1, 0, result, 0, length);
return result;
}
else {
wr = new SSH2DataWriter();
wr.WriteBigInteger(key);
wr.Write(_sessionID);
wr.Write(h1);
byte[] h2 = new SHA1CryptoServiceProvider().ComputeHash(wr.ToByteArray());
if (h1.Length + h2.Length >= length) {
Array.Copy(h1, 0, result, 0, h1.Length);
Array.Copy(h2, 0, result, h1.Length, length - h1.Length);
return result;
}
else
throw new SSHException("necessary key length is too big"); //long key is not supported
}
}
public void WritePrivatePartInSECSHStyleFile(Stream dest, string comment,
SecureString passphrase)
{
//step1 key body
SSH2DataWriter wr = new SSH2DataWriter();
wr.WriteInt32(0); //this field is filled later
if (_keypair.Algorithm == PublicKeyAlgorithm.RSA)
{
RSAKeyPair rsa = (RSAKeyPair)_keypair;
RSAPublicKey pub = (RSAPublicKey)_keypair.PublicKey;
wr.WriteBigIntWithBits(pub.Exponent);
wr.WriteBigIntWithBits(rsa.D);
wr.WriteBigIntWithBits(pub.Modulus);
wr.WriteBigIntWithBits(rsa.U);
wr.WriteBigIntWithBits(rsa.P);
wr.WriteBigIntWithBits(rsa.Q);
}
else
{
DSAKeyPair dsa = (DSAKeyPair)_keypair;
DSAPublicKey pub = (DSAPublicKey)_keypair.PublicKey;
wr.WriteInt32(0);
wr.WriteBigIntWithBits(pub.P);
wr.WriteBigIntWithBits(pub.G);
wr.WriteBigIntWithBits(pub.Q);
wr.WriteBigIntWithBits(pub.Y);
wr.WriteBigIntWithBits(dsa.X);
}
int padding_len = 0;
if (passphrase != null)
{
padding_len = 8 - (int)wr.Length%8;
wr.Write(new byte[padding_len]);
}
byte[] encrypted_body = wr.ToByteArray();
SSHUtil.WriteIntToByteArray(encrypted_body, 0,
encrypted_body.Length - padding_len - 4);
//encrypt if necessary
if (passphrase != null)
{
var c = CipherFactory.CreateCipher(SSHProtocol.SSH2, CipherAlgorithm.TripleDES,
PassphraseToKey(passphrase, 24));
Debug.Assert(encrypted_body.Length%8 == 0);
var tmp = new byte[encrypted_body.Length];
c.Encrypt(encrypted_body, 0, encrypted_body.Length, tmp, 0);
encrypted_body = tmp;
}
//step2 make binary key data
wr = new SSH2DataWriter();
wr.WriteInt32(MAGIC_VAL);
wr.WriteInt32(0); //for total size
wr.WriteString(_keypair.Algorithm == PublicKeyAlgorithm.RSA
? "if-modn{sign{rsa-pkcs1-sha1},encrypt{rsa-pkcs1v2-oaep}}"
: "dl-modp{sign{dsa-nist-sha1},dh{plain}}");
wr.WriteString(passphrase == null ? "none" : "3des-cbc");
wr.WriteAsString(encrypted_body);
var rawdata = wr.ToByteArray();
SSHUtil.WriteIntToByteArray(rawdata, 4, rawdata.Length); //fix total length
//step3 write final data
var sw = new StreamWriter(dest, Encoding.ASCII);
sw.WriteLine("---- BEGIN SSH2 ENCRYPTED PRIVATE KEY ----");
if (comment != null)
WriteKeyFileBlock(sw, "Comment: " + comment, true);
WriteKeyFileBlock(sw, Encoding.ASCII.GetString(Base64.Encode(rawdata)), false);
sw.WriteLine("---- END SSH2 ENCRYPTED PRIVATE KEY ----");
sw.Close();
}
