////////////////////////////////////////////////////////////////////////////////
//
//  Microsoft Research Singularity
//
//  Copyright (c) Microsoft Corporation.  All rights reserved.
//
//  File:   NtlmSupplicant.cs
//
//  Note:
//
//		This file contains an implementation of the NTLM v1 authentication 
//		protocol.
//
//		This implementation contains only the logic for building, parsing, and
//		validating, etc. NTLM messages and hashes.  This code does not handle
//		anything related to a specific application of NTLM; it does not handle
//		storing or retrieving credentials, nor does it handle transmitting
//		NTLM messages to or from remote applications.  All of that logic depends
//		on the situation in which NTLM is used, and so is omitted.
//
//		The NtlmSupplicant class provides methods for computing the NTLM v1
//		hashes (both Lan Man and NT hashes), given a username, password, and
//		a challenge (nonce) received from the authenticator (server).  These
//		methods can be used in two different ways: they can act directly on
//		already-parsed fields (useful when the application carries the fields
//		separately, as basic SMB authentication does), or they can act on
//		NTLMSSP messages.
//
//		NTLMSSP messages are those that are produced and consumed by the Windows
//		NTLM SSPI package.  These messages are treated as opaque byte blobs by
//		application protocols, and the NTLM SSPI package handles building and
//		parsing these messages.  This simplifies integration of NTLM into
//		application protocols, and also enables NTLM to be used with the SPNEGO
//		multi-protocol negotiation protocol.
//
//
// TODO:
//
//		*	Only the supplicant logic is provided.  Need to provide the methods that
//			an authenticator would need.
//
//		*	Byte-order cleanup.  The protocol is little-endian.
//
//		*	NTLM v2
//
///////////////////////////////////////////////////////////////////////////////

using System;
using System.Diagnostics;
using System.Text;
using Microsoft.Singularity;
using System.Security.Cryptography;
using Utils;

namespace System.Security.Protocols.Ntlm
{
	///
	//<summary>
	//	<para>
	//		Implements the NTLM authentication protocol.
	//	</para>
	//	<para>
	//		This is a "static" class; there are no instance fields or methods.
	//		None of the methods of this class have any side-effects, outside of
	//		operating on the parameters passed to them.
	//	</para>
	//</summary>
	//
    public /*static*/ sealed class NtlmSupplicant 
    {
		private NtlmSupplicant() {}
		
		///
		//	<summary>
		//		Builds an NTLMSSP "Negotiate" message, which begins an NTLM authentication exchange.
		//		The caller supplies negotiation flags, which request certain behaviors, as well as
		//		the domain name and workstation name of the client computer.
		//	</summary>
//
		//	<remarks>
		//		<para>
		//			The caller can also provide the domain name and workstation name of the client.
		//			These values are not required, and are usually used for event logging.
		//		</para>
		//		<para>
		//			This method does not have any side-effects.
		//		</para>
		//	</remarks>
		//	
		//	<param name="flags">
		//		Enables certain NTLM options.  See the NtlmNegotiateFlags enumerated type for more info.
		//	</param>	
		//	<param name="domain">
		//		The domain name of the client computer.  If the caller does not want
		//		to provide this information, pass an empty string.
		//	</param>
		//	<param name="workstation">
		//		The name of the client computer.  If the caller does not want to provide this information,
		//		then pass an empty string.
		//	</param>
		//	<returns>
		//		A buffer containing the encoded NTLMSSP "Negotiate" message.  This message should be sent 
		//		to any application that supports NTLM authentication, using whatever transport mechanism 
		//		is appropriate for the application.
		//	</returns>
		//
        public static byte[]! GetNegotiate(NtlmNegotiateFlags flags, string! domain, string! workstation)
        {
            Encoding encoding = Encoding.Unicode;
            
			// Build the fixed-length header of the message.  Also, compute the offsets and lengths
			// of the variable-length fields (the strings).			

			NtlmNegotiateMessage negotiate;			
			negotiate.Header.MessageType = (uint)NtlmMessageType.Negotiate;
			negotiate.Header.Signature = NtlmConstants.MessageSignature64Le;
			negotiate.NegotiateFlags = (uint)(flags |
                NtlmNegotiateFlags.RequestTarget
                | NtlmNegotiateFlags.NegotiateNtlm
                | NtlmNegotiateFlags.NegotiateNtOnly
                | NtlmNegotiateFlags.NegotiateLmKey
                | NtlmNegotiateFlags.NegotiateUnicode);
            negotiate.Version = 0;
            negotiate.OemDomainName = new BufferRegion((ushort)encoding.GetByteCount(domain), 0, (ushort)sizeof(NtlmNegotiateMessage));
			negotiate.OemWorkstationName = new BufferRegion((ushort)encoding.GetByteCount(workstation), 0, (ushort)(sizeof(NtlmNegotiateMessage) + negotiate.OemDomainName.Length));

			// Next, allocate the buffer, store the fixed-length header, and store the variable-length strings.
			int messageLength = sizeof(NtlmNegotiateMessage) + negotiate.OemDomainName.Length + negotiate.OemWorkstationName.Length;
			byte[]! negotiateBuffer = new byte[messageLength];
			
			ref NtlmNegotiateMessage negotiate_ref = ref negotiateBuffer[0];
			negotiate_ref = negotiate; // copy the header
			encoding.GetBytes(domain, 0, domain.Length, negotiateBuffer, negotiate.OemDomainName.Offset);
			encoding.GetBytes(workstation, 0, workstation.Length, negotiateBuffer, negotiate.OemWorkstationName.Offset);

            return negotiateBuffer;
        }

		#region From my DES port
		
        static byte[]! Convert7ByteKeyTo8ByteKey(byte[]! input)
        {
            // we pack the input into the HIGH bits of a 64-bit unsigned int
            ulong x =
                ((ulong)input[0] << 0x38) |
                ((ulong)input[1] << 0x30) |
                ((ulong)input[2] << 0x28) |
                ((ulong)input[3] << 0x20) |
                ((ulong)input[4] << 0x18) |
                ((ulong)input[5] << 0x10) |
                ((ulong)input[6] << 0x08);


            ulong a = x;

            byte[]! result = new byte[8];
            for (int i = 0; i < 8; i++) {
                // the LOWEST bit is the parity bit
                // right now, we always set the parity bit to 0
                byte b = (byte)((a >> 56) & 0xfe);
                b = FixParity0(b); // this isn't actually necessary
                result[i] = b;

                a <<= 7;
            }

            return result;
        }

        // bit 0 is the parity bit!
        static byte FixParity0(byte b)
        {
            byte temp = b;

            int parity = 0;
            for (int i = 1; i < 8; i++) {
                parity ^= temp & 2;
                temp >>= 1;
            }

            if (parity == 0)
                return (byte)(b | 1);
            else
                return (byte)(b & 0xfe);
        }
        #endregion

		///
		//<summary>
		//	<para>	
		//		This method computes part of the NTLM hash function.  It operates on part of the password, 7 characters
		//		at a time, and computes a hash of them.  The hash is then stored in the 'output' buffer at the offset
		//		'outputindex'.  The hash is always 8 bytes long, so the 'output' buffer needs to have a length of at
		//		least outputindex + 8.
		//	</para>
		//	<para>
		//		This hash function is known to be cryptographically weak.
		//	</para>
		//	<para>
		//		This method only works on passwords that contain only 7-bit ASCII character.
		//		Lower-case characters are forced to upper-case.
		//	</para>
		//</summary>
		//<param name="password">
		//	The cleartext password of the user.
		//	The method will read up to 7 characters of the password, starting at 'passwordindex'.
		//</param>
		//<param name="passwordindex">
		//	The index of the first character within 'password' to read.
		//	This value may legally be greater than or equal to the length of 'password'.
		//	The method will read the first 7 characters, beginning at this index, and if there
		//	are fewer than 7 valid characters (including no characters), the method will pad
		//	with zeroes.
		//</param>
		//<param name="output">
		//	The output buffer in which to store the 8-byte hash of the portion of the password.
		//	The length of this buffer must be at least 'outputindex' + 8.
		//</param>
		//<param name="outputindex">The position within the 'output' buffer to store the hash.</param>
		//
        static void ComputeLmResponseHalf(string! password, int passwordindex, byte[]! output, int outputindex)
			requires passwordindex >= 0;
			// requires passwordindex <= password.Length; <-- This is *NOT* a precondition!
			requires outputindex >= 0;
			requires outputindex + 8 <= output.Length;
        {
            byte[]! desKey7 = new byte[7];
            for (int i = 0; i < 7; i++) {
                if (i + passwordindex < password.Length) {
					char c = password[passwordindex + i];
					if (c >= 0x80)
						throw new ArgumentException("The password provided cannot be encoded.  NTLM/LM v1 does not support non-ASCII characters.");
                    desKey7[i] = (byte)Char.ToUpper(c);
                }
                else
                    desKey7[i] = 0;
            }

            byte[]! desKey8 = Convert7ByteKeyTo8ByteKey(desKey7);
            byte[]! cleartext = new byte[8];
            
            const string cleartext_string = "KGS!@#$%";
            
            for (int i = 0; i < 8; i++)
                cleartext[i] = (byte)cleartext_string[i];

            byte[]! cipher = new byte[8];
            Des.Encrypt(desKey8, cleartext, cipher);
            for (int i = 0; i < 8; i++)
                output[i + outputindex] = cipher[i];
        }

		///
		//<summary>
		//	This method computes the NTLM v1 One-Way Function.
		//</summary>
		//<param name="challenge">Contains the 8-byte challenge (nonce) generated by the server.</param>
		//<param name="hash">
		//	Contains the 21-byte intermediate password hash.
		//	This buffer must be exactly 21 bytes long.
		//</param>
		//<returns>
		//	The computed One-Way Function.  This is the value that is sent to the NTLM authenticator.
		//</returns>
		//
        public static byte[]! ComputeOwf(byte[]! challenge, byte[]! hash)
			requires challenge.Length >= 8;
			requires hash.Length == 21;
			ensures result.Length == 24;
        {
            if (hash.Length != 21)
                throw new Exception("Hash is wrong length");

#if NOISY
            DebugLine("ComputeOwf: challenge=" + Util.ByteArrayToStringHex(challenge) + " hash=" + Util.ByteArrayToStringHex(hash));
            DebugLine("    challenge: " + Util.ByteArrayToStringBitsLe(challenge));
#endif

            byte[] response = new byte[24];
            for (int r = 0; r < 3; r++) {
#if NOISY
                DebugLine("    r = " + r);
#endif

                // Next, we encrypt the server's challenge three times, using the DES algorithm.
                // The result is the LM response.
                byte[] thirdKey7 = new byte[7];
                Array.Copy(hash, r * 7, thirdKey7, 0, 7);

                
                byte[] thirdKey8 = Convert7ByteKeyTo8ByteKey(thirdKey7);
#if NOISY
                DebugLine("        key7 = " + Util.ByteArrayToStringHex(thirdKey7));
                //DebugLine("        key7 = " + Util.ByteArrayToStringBitsLe(thirdKey7));
                DebugLine("        key7 = " + Util.ByteArrayToStringBitsBe(thirdKey7));
                DebugLine("        key8 = " + Util.ByteArrayToStringHex(thirdKey8));
                //DebugLine("        key8 = " + Util.ByteArrayToStringBitsLe(thirdKey8));
                DebugLine("        key8 = " + Util.ByteArrayToStringBitsBe(thirdKey8));
#endif

                byte[] cipher = new byte[8];
                Des.Encrypt(thirdKey8, challenge, cipher);
                Array.Copy(cipher, 0, response, r * 8, 8);

#if NOISY
                DebugLine("        cipher = " + Util.ByteArrayToStringBitsBe(cipher));
                DebugLine("        cipher = " + Util.ByteArrayToStringHex(cipher));
#endif
            }

#if NOISY
            DebugLine("    response: " + Util.ByteArrayToStringHex(response));
#endif
            return response;
        }

		///
		//<summary>
		//	<para>
		//		This method computes the NTLM v1 "LAN Manager" authentication response.
		//		This response is known to be very weak, cryptographically.
		//	</para>
		//	<para>
		//		The 'challenge' parameter contains the 8-byte challenge nonce, which was
		//		generated by the NTLMSSP running in the context of the server application.
		//		The 'password' parameter contains the clear-text user password.
		//	</para>
		//	<para>
		//		This method does not have any side-effects.
		//	</para>
		//</summary>
		//<param name="challenge">The 8-byte challenge (nonce) generated by the server.</param>
		//<param name="password">The cleartext password of the authenticating user.</param>
		//<returns>
		//	The return value is a newly-allocated buffer containing the encoded NTLM
		//	response hash, which proves that the client is in possession of the password
		//	for an identified account.  This buffer is always 24 bytes in length.
		//</returns>
		//
        public static byte[]! ComputeLmResponse(byte[]! challenge, string! password)
			requires challenge.Length == 8;
			ensures result.Length == 24;
        {
            byte[]! hash = new byte[21];
            ComputeLmResponseHalf(password, 0, hash, 0);
            ComputeLmResponseHalf(password, 7, hash, 8);
            for (int i = 16; i < 21; i++)
                hash[i] = 0;

            byte[]! response = ComputeOwf(challenge, hash);
#if NOISY
            DebugLine("LM response: " + Util.ByteArrayToStringHex(response));
#endif
            return response;
        }

		///
		//<summary>
		//	<para>
		//		This method computes the NTLM v1 "NT" authentication response.
		//		This response is known to be weak, cryptographically, but is better than
		//		the NTLM v1 "LAN Manager" response.
		//	</para>
		//	<para>
		//		This method does not have any side-effects.
		//	</para>
		//</summary>
//
		//<param name="challenge">		
		//	Contains the 8-byte challenge nonce, which was generated by the NTLMSSP running 
		//	in the context of the server application.
		//</param>
		//<param name="password">Contains the clear-text user password.</param>
		//<returns>
		//	A buffer containing the encoded NTLM response hash, which proves that the client 
		//	is in possession of the password for an identified account.  This buffer is always 
		//	24 bytes in length.
		//</returns>
		//
        public static byte[]! ComputeNtResponse(byte[]! challenge, string! password)
			requires challenge.Length == 8;
			ensures result.Length == 24;
        {
            byte[]! password_bytes = (!)Encoding.Unicode.GetBytes(password);
#if true // THIS CAUSES BARTOK TO THROW AN UNHANDLED EXCEPTION!
            byte[]! digest = (!)(MD4Context.GetDigest(password_bytes).ToArray());
#else // compiler shuts up, but obviously the code doesn't work
			IgnoreConsume(password_bytes);
            byte[]! digest = new byte[0];
#endif

#if NOISY
            DebugLine("Computing NTLM v1 response:");
            DebugLine("    challenge:         " + Util.ByteArrayToStringHex(challenge));
            DebugLine("    password:          " + password);
            DebugLine("    password bytes:    " + Util.ByteArrayToStringHex(password_bytes));
            DebugLine("    MD4(pw bytes):     " + Util.ByteArrayToStringHex(digest));
#endif

            // The hash is the MD4 digest, padded with zeroes to a length of 21.
            // assert digest.Length == 16;
            byte[]! hash = new byte[21];
            ArrayCopy(digest, 0, hash, 0, 16);
            ArrayClear(hash, 16, 5);

            byte[]! response = ComputeOwf(challenge, hash);
#if NOISY
            DebugLine("NTLM v1 response: " + Util.ByteArrayToStringHex(response));
#endif
            return response;
        }
        
        static void ArrayCopy(byte[]! src, int srcoffset, byte[]! dst, int dstoffset, int length)
        {
			for (int i = 0; i < length; i++)
				dst[dstoffset + i] = src[srcoffset + i];
        }
        
        static void ArrayClear(byte[]! dst, int offset, int length)
        {
			for (int i = 0; i < length; i++)
				dst[offset + i] = 0;
        }
        
        public const int ChallengeLength = 8;
        public const int ResponseLength = 24;

		///
		//<summary>
		//	This method generates an NTLMSSP "Response" message, given valid client credentials and
		//	an NTLMSSP "Challenge" message.
		//</summary>
		//
		//<param name="challenge_buffer">
		//	Contains the encoded NTLMSSP "Response" message, which was generated by the remote 
		//	NTLM-enabled application.
		//</param>
		//<param name="domain">The domain name of the authenticating user.</param>
		//<param name="username">The username of the authenticating user.</param>
		//<param name="password">The cleartext password of the authenticating user.</param>
		//<returns>
		//	A buffer containing the encoded NTLMSSP "Response" message.  This buffer should be 
		//	sent to the remote application, using whatever transport is appropriate.
		//</returns>
		//
        public static byte[]! GetResponse(
			byte[]! challenge_buffer,
			string! domain,
			string! username,
			string! workstation,
			string! password)
        {
			if (challenge_buffer.Length < sizeof(NtlmChallengeMessage))
				throw new Exception("The buffer supplied contains too little data to contain a valid NTLM challenge message.");
				
			ref NtlmChallengeMessage challenge_msg = ref challenge_buffer[0];
			if (challenge_msg.Header.Signature != NtlmConstants.MessageSignature64Le)
				throw new Exception("The NTLM message has an invalid signature.");
			
			if (challenge_msg.Header.MessageType != (uint)NtlmMessageType.Challenge)
				throw new Exception("The NTLM message provided is not a Challenge message.");

            byte[]! challenge_bytes = NtlmUtil.GetSubArray(challenge_buffer, 0x18, NtlmConstants.ChallengeLength);
            
// known good here			
#if NOISY
            string TargetName = NtlmUtil.GetCountedStringAt(challenge_buffer, challenge_msg.TargetName.Offset);
            DebugLine("    TargetName:     " + TargetName);
            DebugLine("    Challenge:      " + Util.ByteArrayToStringHex(challenge_bytes));
#endif

            //
            // First, compute the ancient, horrible, insecure LM response.
            //

            byte[]! Lm_response = ComputeLmResponse(challenge_bytes, password);
            byte[]! Nt_response = ComputeNtResponse(challenge_bytes, password);
            
            // assert Lm_response.Length == 24;
            // assert Nt_response.Length == 24;

			//
			// Next, build the Authenticate message.  The message has a fixed-length header, described
			// by NtlmAuthenticateMessage, followed by the string bodies.
			//

			System.Text.Encoding encoding = System.Text.Encoding.Unicode;
			byte[]! domainBytes = (!)encoding.GetBytes(domain);
			byte[]! usernameBytes = (!)encoding.GetBytes(username);
			byte[]! workstationBytes = (!)encoding.GetBytes(workstation);
			
			int responseBufferLength = sizeof(NtlmResponseMessage)
				+ Lm_response.Length
				+ Nt_response.Length
				+ domainBytes.Length
				+ usernameBytes.Length
				+ workstationBytes.Length;
// known bad
			
            // Now we know the size of the entire response message.  Allocate it.
            byte[]! responseBuffer = new byte[responseBufferLength];
            
            ref NtlmResponseMessage response = ref responseBuffer[0];
            response.Header.Signature = NtlmConstants.MessageSignature64Le;
            response.Header.MessageType = (uint)NtlmMessageType.Response;

            byte[]![]! strings = {
                Lm_response,
                Nt_response,
                domainBytes,
                usernameBytes,
                workstationBytes
            };

            // Scan through the variable-length strings again and store the string headers.
            // Also copy the string body into place.
            int write_pos = sizeof(NtlmResponseMessage);
            for (int i = 0; i < strings.Length; i++) {
				byte[]! stringbytes = strings[i];
				ref BufferRegion region = ref responseBuffer[sizeof(NtlmMessageHeader) + i * sizeof(BufferRegion)];
				region = new BufferRegion((ushort)stringbytes.Length, (ushort)stringbytes.Length, (ushort)write_pos);
				Array.Copy(stringbytes, 0, responseBuffer, write_pos, stringbytes.Length);
				write_pos += stringbytes.Length;
            }
            
			return responseBuffer;
        }

#if NOISY
		static void DebugLine(string msg)
		{
			DebugStub.WriteLine("NTLM: " + msg);
		}
#endif

        static string! PadTruncate(string! s, int length)
        {
            if (s.Length == length)
                return s;
            if (s.Length > length)
                return s.Substring(0, length);
            return s.PadRight((Char)0);
        }
    }
    
    /*static*/ sealed class ByteOrder
    {
		private ByteOrder() {}
		
		public static ushort UInt16LeToHost(ushort value)
		{
			return value;
		}
		
		public static uint UInt32LeToHost(uint value)
		{
			return value;
		}
    }
}