// Section 3.3.2
//
// Set LmChallengeResponse to ConcatenationOf(
// HMAC_MD5(ResponseKeyLM, ConcatenationOf(CHALLENGE_MESSAGE.ServerChallenge, ClientChallenge)),
// ClientChallenge )
private int makeLm2ChallengeResponse(byte[] lm2Hash, ReadOnlySpan <byte> serverChallenge, Span <byte> clientChallenge, ref Span <byte> responseAsBytes)
{
Debug.Assert(serverChallenge.Length == ChallengeLength);
Debug.Assert(clientChallenge.Length == ChallengeLength);
Debug.Assert(lm2Hash.Length == DigestLength);
Span <AuthenticateMessage> response = MemoryMarshal.Cast <byte, AuthenticateMessage>(responseAsBytes);
// Get server and client nonce
Span <byte> blob = stackalloc byte[16];
serverChallenge.CopyTo(blob);
clientChallenge.CopyTo(blob.Slice(ChallengeLength));
Span <byte> lmResponse = responseAsBytes.Slice((int)Marshal.OffsetOf(typeof(AuthenticateMessage), "LmResponse"), ChallengeResponseLength);
HMACMD5 hmac = new HMACMD5(lm2Hash);
bool result = hmac.TryComputeHash(blob, lmResponse, out int bytes);
if (!result || bytes != DigestLength)
{
return(0);
}
clientChallenge.CopyTo(lmResponse.Slice(DigestLength));
SetField(ref response[0].LmChallengeResponse, ChallengeResponseLength, (int)Marshal.OffsetOf(typeof(AuthenticateMessage), "LmResponse"));
return(ChallengeResponseLength);
}
// Section 3.3.2
//
// Set temp to ConcatenationOf(Responserversion, HiResponserversion, Z(6), Time, ClientChallenge, Z(4), ServerName, Z(4))
// Set NTProofStr to HMAC_MD5(ResponseKeyNT, ConcatenationOf(CHALLENGE_MESSAGE.ServerChallenge, temp))
// Set NtChallengeResponse to ConcatenationOf(NTProofStr, temp)
private unsafe int makeNtlm2ChallengeResponse(byte[] lm2Hash, ReadOnlySpan <byte> serverChallenge, Span <byte> clientChallenge, ReadOnlySpan <byte> serverInfo, ref MessageField field, ref Span <byte> payload)
{
Debug.Assert(serverChallenge.Length == ChallengeLength);
Debug.Assert(clientChallenge.Length == ChallengeLength);
Debug.Assert(lm2Hash.Length == DigestLength);
Span <byte> blob = payload.Slice(0, sizeof(NtChallengeResponse) + serverInfo.Length);
Span <NtChallengeResponse> temp = MemoryMarshal.Cast <byte, NtChallengeResponse>(blob.Slice(0, sizeof(NtChallengeResponse)));
temp[0].HiResponserversion = 1;
temp[0].Responserversion = 1;
temp[0].Time = DateTime.Now.Ticks;
int offset = (int)Marshal.OffsetOf(typeof(NtChallengeResponse), "ClientChallenge");
clientChallenge.CopyTo(blob.Slice(offset, ChallengeLength));
offset += ChallengeLength + 4; // challengeLength + Z4
serverInfo.CopyTo(blob.Slice(offset));
// We will prepend server chalenge for purpose of calculating NTProofStr
// It will be overriten later.
serverChallenge.CopyTo(blob.Slice(ChallengeLength, ChallengeLength));
Span <byte> NTProofStr = stackalloc byte[DigestLength];
HMACMD5 hmac = new HMACMD5(lm2Hash);
bool result = hmac.TryComputeHash(blob.Slice(ChallengeLength), NTProofStr, out int bytes);
if (!result || bytes != DigestLength)
{
return(0);
}
// we created temp part in place where it needs to be.
// now we need to prepend it with calculated hmac.
// Write first 16 bytes, overiding challengeLength part.
NTProofStr.CopyTo(blob);
SetField(ref field, blob.Length, sizeof(AuthenticateMessage));
payload = payload.Slice(blob.Length);
return(blob.Length);
}
