/// <summary>
/// Update session key according to section 5.3.7 Session Key Updates.
/// </summary>
internal void UpdateSessionKey()
{
if (encryptionMethod == EncryptionMethods.ENCRYPTION_METHOD_40BIT ||
encryptionMethod == EncryptionMethods.ENCRYPTION_METHOD_56BIT ||
encryptionMethod == EncryptionMethods.ENCRYPTION_METHOD_128BIT)
{
currentClientEncryptKey = UpdateKey(initialClientEncryptKey,
currentClientEncryptKey,
encryptionMethod);
currentClientDecryptKey = UpdateKey(initialClientDecryptKey,
currentClientDecryptKey,
encryptionMethod);
currentServerEncryptKey = UpdateKey(initialServerEncryptKey,
currentServerEncryptKey,
encryptionMethod);
currentServerDecryptKey = UpdateKey(initialServerDecryptKey,
currentServerDecryptKey,
encryptionMethod);
RC4CryptoServiceProvider rc4Enc = new RC4CryptoServiceProvider();
rc4Encrypt = rc4Enc.CreateEncryptor(currentClientEncryptKey, null);
rc4EncryptServer = rc4Enc.CreateEncryptor(currentServerEncryptKey, null);
RC4CryptoServiceProvider rc4Dec = new RC4CryptoServiceProvider();
rc4Decrypt = rc4Dec.CreateDecryptor(currentClientDecryptKey, null);
rc4DecryptServer = rc4Dec.CreateDecryptor(currentServerDecryptKey, null);
}
// else in other cases we don't need to update session key
}
internal void GenerateSessionKey(byte[] clientRandom, byte[] serverRandom)
{
if (encryptionMethod == EncryptionMethods.ENCRYPTION_METHOD_40BIT ||
encryptionMethod == EncryptionMethods.ENCRYPTION_METHOD_56BIT ||
encryptionMethod == EncryptionMethods.ENCRYPTION_METHOD_128BIT)
{
byte[] mackey = null;
byte[] clientEncKey = null;
byte[] clientDecKey = null;
GenerateNonFIPSSessionKey(clientRandom, serverRandom, out mackey, out clientEncKey, out clientDecKey);
if (encryptionMethod == EncryptionMethods.ENCRYPTION_METHOD_40BIT)
{
// MACKey40 = 0xD1269E + Last40Bits(First64Bits(MACKey128))
byte[] salt = ConstValue.NON_FIPS_SALT_40BIT;
byte[] first = GetFirstNBits(64, mackey);
byte[] last = GetLastNBits(40, first);
macKey = RdpbcgrUtility.ConcatenateArrays(salt, last);
// InitialClientEncryptKey40 = 0xD1269E + Last40Bits(First64Bits(InitialClientEncryptKey128))
first = GetFirstNBits(64, clientEncKey);
last = GetLastNBits(40, first);
currentClientEncryptKey = RdpbcgrUtility.ConcatenateArrays(salt, last);
currentServerDecryptKey = RdpbcgrUtility.ConcatenateArrays(salt, last);
// InitialClientDecryptKey40 = 0xD1269E + Last40Bits(First64Bits(InitialClientDecryptKey128))
first = GetFirstNBits(64, clientDecKey);
last = GetLastNBits(40, first);
currentClientDecryptKey = RdpbcgrUtility.ConcatenateArrays(salt, last);
currentServerEncryptKey = RdpbcgrUtility.ConcatenateArrays(salt, last);
}
else if (encryptionMethod == EncryptionMethods.ENCRYPTION_METHOD_56BIT)
{
// MACKey56 = 0xD1 + Last56Bits(First64Bits(MACKey128))
byte[] salt = ConstValue.NON_FIPS_SALT_56BIT;
byte[] first = GetFirstNBits(64, mackey);
byte[] last = GetLastNBits(56, first);
macKey = RdpbcgrUtility.ConcatenateArrays(salt, last);
// InitialClientEncryptKey56 = 0xD1 + Last56Bits(First64Bits(InitialClientEncryptKey128))
first = GetFirstNBits(64, clientEncKey);
last = GetLastNBits(56, first);
currentClientEncryptKey = RdpbcgrUtility.ConcatenateArrays(salt, last);
currentServerDecryptKey = RdpbcgrUtility.ConcatenateArrays(salt, last);
// InitialClientDecryptKey56 = 0xD1 + Last56Bits(First64Bits(InitialClientDecryptKey128))
first = GetFirstNBits(64, clientDecKey);
last = GetLastNBits(56, first);
currentClientDecryptKey = RdpbcgrUtility.ConcatenateArrays(salt, last);
currentServerEncryptKey = RdpbcgrUtility.ConcatenateArrays(salt, last);
}
else // encryptionMethod == EncryptionMethods.ENCRYPTION_METHOD_128BIT
{
macKey = mackey;
currentClientEncryptKey = clientEncKey;
currentServerDecryptKey = clientEncKey;
currentClientDecryptKey = clientDecKey;
currentServerEncryptKey = clientDecKey;
}
initialClientDecryptKey = currentClientDecryptKey;
initialClientEncryptKey = currentClientEncryptKey;
initialServerEncryptKey = currentServerEncryptKey;
initialServerDecryptKey = currentServerDecryptKey;
RC4CryptoServiceProvider rc4Enc = new RC4CryptoServiceProvider();
rc4Encrypt = rc4Enc.CreateEncryptor(currentClientEncryptKey, null);
rc4EncryptServer = rc4Enc.CreateEncryptor(currentServerEncryptKey, null);
RC4CryptoServiceProvider rc4Dec = new RC4CryptoServiceProvider();
rc4Decrypt = rc4Dec.CreateDecryptor(currentClientDecryptKey, null);
rc4DecryptServer = rc4Dec.CreateDecryptor(currentServerDecryptKey, null);
}
else if (encryptionMethod == EncryptionMethods.ENCRYPTION_METHOD_FIPS)
{
GenerateFIPSSessionKey(clientRandom, serverRandom, out macKey,
out currentClientEncryptKey, out currentClientDecryptKey,
out currentServerEncryptKey, out currentServerDecryptKey);
initialClientDecryptKey = currentClientDecryptKey;
initialClientEncryptKey = currentClientEncryptKey;
initialServerDecryptKey = currentServerDecryptKey;
initialServerEncryptKey = currentServerEncryptKey;
// suppress "CA5353:TripleDESCannotBeUsed" message, since TripleDES is used according protocol definition in MS-RDPBCGR
desEncrypt = new TripleDESCryptoServiceProvider();
desEncrypt.IV = ConstValue.TRPLE_DES_IV;
desEncrypt.Key = currentClientEncryptKey;
desEncrypt.Mode = CipherMode.CBC;
desDecrypt = new TripleDESCryptoServiceProvider();
desDecrypt.IV = ConstValue.TRPLE_DES_IV;
desDecrypt.Key = currentClientDecryptKey;
desDecrypt.Mode = CipherMode.CBC;
desEncryptServer = new TripleDESCryptoServiceProvider();
desEncryptServer.IV = ConstValue.TRPLE_DES_IV;
desEncryptServer.Key = currentServerEncryptKey;
desEncryptServer.Mode = CipherMode.CBC;
desDecryptServer = new TripleDESCryptoServiceProvider();
desDecryptServer.IV = ConstValue.TRPLE_DES_IV;
desDecryptServer.Key = currentServerDecryptKey;
desDecryptServer.Mode = CipherMode.CBC;
}
else // the encryption method is ENCRYPTION_METHOD_NONE or error
{
macKey = null;
initialClientEncryptKey = null;
initialClientDecryptKey = null;
currentClientEncryptKey = null;
currentClientDecryptKey = null;
initialServerEncryptKey = null;
initialServerDecryptKey = null;
currentServerEncryptKey = null;
currentServerDecryptKey = null;
rc4Encrypt = null;
rc4Decrypt = null;
rc4EncryptServer = null;
rc4DecryptServer = null;
desEncrypt = null;
desDecrypt = null;
desEncryptServer = null;
desDecryptServer = null;
}
// the cumulative encryption/decryption count
// indicating how many encryptions/decryptions have been carried out.
encryptionCount = 0; // the first encryption start with 0
decryptionCount = -1; // after the first decryption, decryptionCount++ up to 0
}