private static byte[] Decrypt(byte[] k1, byte[] ciphertext, KeyUsage keyType)
{
var salt = GetSalt((int)keyType);
var k2 = KerberosHash.HMACMD5(k1, salt);
var checksum = new byte[HashSize];
Buffer.BlockCopy(ciphertext, 0, checksum, 0, HashSize);
var k3 = KerberosHash.HMACMD5(k2, checksum);
var ciphertextOffset = new byte[ciphertext.Length - HashSize];
Buffer.BlockCopy(ciphertext, HashSize, ciphertextOffset, 0, ciphertextOffset.Length);
var plaintext = RC4.Decrypt(k3, ciphertextOffset);
var calculatedHmac = KerberosHash.HMACMD5(k2, plaintext);
if (!KerberosHash.AreEqualSlow(calculatedHmac, ciphertext, calculatedHmac.Length))
{
throw new SecurityException("Invalid Checksum");
}
var output = new byte[plaintext.Length - ConfounderSize];
Buffer.BlockCopy(plaintext, ConfounderSize, output, 0, output.Length);
return(output);
}
public static byte[] NFold(byte[] inBytes, int size)
{
var inBytesNum = inBytes.Length;
var outBytesNum = size;
var a = outBytesNum;
var b = inBytesNum;
var c = 0;
while (b != 0)
{
c = b;
b = a % b;
a = c;
}
var lcm = (outBytesNum * inBytesNum) / a;
var outBytes = new byte[outBytesNum];
KerberosHash.Fill(outBytes, (byte)0);
var tmpByte = 0;
for (var i = lcm - 1; i >= 0; i--)
{
var tmp = ((inBytesNum << 3) - 1);
tmp += (((inBytesNum << 3) + 13) * (i / inBytesNum));
tmp += ((inBytesNum - (i % inBytesNum)) << 3);
var msbit = tmp % (inBytesNum << 3);
tmp = ((((inBytes[((inBytesNum - 1) - (msbit >> 3)) % inBytesNum] & 0xff) << 8) |
(inBytes[((inBytesNum) - (msbit >> 3)) % inBytesNum] & 0xff))
>> ((msbit & 7) + 1)) & 0xff;
tmpByte += tmp;
tmp = outBytes[i % outBytesNum] & 0xff;
tmpByte += tmp;
outBytes[i % outBytesNum] = (byte)(tmpByte & 0xff);
tmpByte >>= 8;
}
if (tmpByte != 0)
{
for (var i = outBytesNum - 1; i >= 0; i--)
{
tmpByte += (outBytes[i] & 0xff);
outBytes[i] = (byte)(tmpByte & 0xff);
tmpByte >>= 8;
}
}
return(outBytes);
}
public virtual byte[] MakeChecksum(byte[] key, byte[] data, int hashSize)
{
var hash = KerberosHash.KerberosHMAC(hasher, key, data);
var output = new byte[hashSize];
Buffer.BlockCopy(hash, 0, output, 0, hashSize);
return(output);
}
protected override bool ValidateInternal(KerberosKey key)
{
var actualChecksum = KerberosHash.KerbChecksumHmacMd5(
key.GetKey(new MD4Encryptor()),
(int)KeyUsage.KU_PA_FOR_USER_ENC_CKSUM,
Pac
);
return(KerberosHash.AreEqualSlow(actualChecksum, Signature));
}
protected override bool ValidateInternal(KerberosKey key)
{
var constant = new byte[5];
KerberosHash.ConvertToBigEndian((int)KeyUsage.KU_PA_FOR_USER_ENC_CKSUM, constant, 0);
constant[4] = 0x99;
var Ki = encryptor.DK(key.GetKey(encryptor), constant);
var actualChecksum = decryptor.MakeChecksum(Ki, Pac, decryptor.ChecksumSize);
return(KerberosHash.AreEqualSlow(actualChecksum, Signature));
}
public byte[] String2Key(KerberosKey key)
{
return(KerberosHash.MD4(key.PasswordBytes));
}
