public override ReadOnlyMemory <byte> Decrypt(ReadOnlyMemory <byte> ciphertext, KerberosKey key, KeyUsage usage)
{
var k1 = key.GetKey(this);
var salt = GetSalt((int)usage);
var k2 = HMACMD5(k1, salt);
var incomingChecksum = ciphertext.Slice(0, HashSize);
var k3 = HMACMD5(k2, incomingChecksum);
var ciphertextOffset = ciphertext.Slice(HashSize);
var plaintext = new Memory <byte>(new byte[ciphertextOffset.Length]);
RC4.Transform(k3.Span, ciphertextOffset.Span, plaintext.Span);
var actualChecksum = HMACMD5(k2, plaintext);
if (!AreEqualSlow(incomingChecksum.Span, actualChecksum.Span.Slice(0, actualChecksum.Length)))
{
throw new SecurityException("Invalid Checksum");
}
return(plaintext.Slice(ConfounderSize));
}
public override ReadOnlyMemory <byte> Encrypt(ReadOnlyMemory <byte> data, KerberosKey key, KeyUsage usage)
{
var k1 = key.GetKey(this);
var salt = GetSalt((int)usage);
var k2 = HMACMD5(k1, salt);
var confounder = GenerateRandomBytes(ConfounderSize);
var plaintextBuffer = new byte[data.Length + confounder.Length];
var plaintext = new Memory <byte>(plaintextBuffer);
confounder.CopyTo(plaintext);
data.CopyTo(plaintext.Slice(confounder.Length));
var checksum = HMACMD5(k2, plaintextBuffer);
var k3 = HMACMD5(k2, checksum);
var ciphertext = new Memory <byte>(new byte[plaintext.Length + checksum.Length]);
RC4.Transform(k3.Span, plaintext.Span, ciphertext.Span.Slice(checksum.Length));
checksum.CopyTo(ciphertext);
return(ciphertext);
}
public override byte[] Decrypt(ReadOnlyMemory <byte> ciphertext, KerberosKey key, KeyUsage usage)
{
var k1 = key.GetKey(this);
var salt = GetSalt((int)usage);
var k2 = HMACMD5(k1, salt);
var checksum = new byte[HashSize];
Buffer.BlockCopy(ciphertext.ToArray(), 0, checksum, 0, HashSize);
var k3 = HMACMD5(k2, checksum);
var ciphertextOffset = new byte[ciphertext.Length - HashSize];
Buffer.BlockCopy(ciphertext.ToArray(), HashSize, ciphertextOffset, 0, ciphertextOffset.Length);
var plaintext = RC4.Transform(k3, ciphertextOffset);
var actualChecksum = HMACMD5(k2, plaintext.ToArray());
if (!AreEqualSlow(checksum, ciphertext.ToArray(), actualChecksum.Length))
{
throw new SecurityException("Invalid Checksum");
}
var output = new byte[plaintext.Length - ConfounderSize];
Buffer.BlockCopy(plaintext.ToArray(), ConfounderSize, output, 0, output.Length);
return(output);
}
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 override ReadOnlyMemory <byte> Encrypt(ReadOnlyMemory <byte> data, KerberosKey key, KeyUsage usage)
{
var k1 = key.GetKey(this);
var salt = GetSalt((int)usage);
var k2 = HMACMD5(k1, salt);
var confounder = GenerateRandomBytes(ConfounderSize);
var plaintext = new byte[data.Length + confounder.Length];
Buffer.BlockCopy(confounder.ToArray(), 0, plaintext, 0, confounder.Length);
Buffer.BlockCopy(data.ToArray(), 0, plaintext, confounder.Length, data.Length);
var checksum = HMACMD5(k2, plaintext);
var k3 = HMACMD5(k2, checksum);
var ciphertext = RC4.Transform(k3, plaintext);
return(new ReadOnlyMemory <byte>(checksum.Concat(ciphertext.ToArray()).ToArray()));
}
