// MD5Checksum.cpp: implementation of the MD5Checksum class.
//
//////////////////////////////////////////////////////////////////////


/****************************************************************************************
This software is derived from the RSA Data Security, Inc. MD5 Message-Digest Algorithm. 
Incorporation of this statement is a condition of use; please see the RSA
Data Security Inc copyright notice below:-

Copyright (C) 1990-2, RSA Data Security, Inc. Created 1990. All
rights reserved.

RSA Data Security, Inc. makes no representations concerning either
the merchantability of this software or the suitability of this
software for any particular purpose. It is provided "as is"
without express or implied warranty of any kind.

These notices must be retained in any copies of any part of this
documentation and/or software.

Copyright (C) 1991-2, RSA Data Security, Inc. Created 1991. All
rights reserved.
License to copy and use this software is granted provided that it
is identified as the "RSA Data Security, Inc. MD5 Message-Digest
Algorithm" in all material mentioning or referencing this software
or this function.
License is also granted to make and use derivative works provided
that such works are identified as "derived from the RSA Data
Security, Inc. MD5 Message-Digest Algorithm" in all material
mentioning or referencing the derived work.
RSA Data Security, Inc. makes no representations concerning either
the merchantability of this software or the suitability of this
software for any particular purpose. It is provided "as is"
without express or implied warranty of any kind.

These notices must be retained in any copies of any part of this
documentation and/or software.
*****************************************************************************************/

/****************************************************************************************
This implementation of the RSA MD5 Algorithm was written by Langfine Ltd 
(www.langfine.com).

Langfine Ltd makes no representations concerning either
the merchantability of this software or the suitability of this
software for any particular purpose. It is provided "as is"
without express or implied warranty of any kind.

In addition to the above, Langfine make no warrant or assurances regarding the 
accuracy of this implementation of the MD5 checksum algorithm nor any assurances regarding
its suitability for any purposes.

This implementation may be used freely provided that Langfine is credited
in a copyright or similar notices (eg, RSA MD5 Algorithm implemented by Langfine
Ltd.) and provided that the RSA Data Security notices are complied with.
*/
#include "stdafx.h"
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include "MD5Checksum.h"


/*****************************************************************************************
FUNCTION:		CMD5Checksum::GetMD5
DETAILS:		static, public
DESCRIPTION:	Gets the MD5 checksum for data in a BYTE array
RETURNS:		CString : the hexadecimal MD5 checksum for the specified data
ARGUMENTS:		BYTE* pBuf  :	pointer to the BYTE array
				UINT nLength :	number of BYTEs of data to be checksumed
NOTES:			Provides an interface to the CMD5Checksum class. Any data that can
				be cast to a BYTE array of known length can be checksummed by this
				function. Typically, CString and char arrays will be checksumed, 
				although this function can be used to check the integrity of any BYTE array. 
				A buffer of zero length can be checksummed; all buffers of zero length 
				will return the same checksum. 
*****************************************************************************************/
void CMD5Checksum::GetMD5(BYTE* pBuf, UINT nLength, BYTE *pMD5)
{

	//calculate and return the checksum
	CMD5Checksum MD5Checksum;
	MD5Checksum.Update( pBuf, nLength );
	MD5Checksum.Final(pMD5);
}


/*****************************************************************************************
FUNCTION:		CMD5Checksum::RotateLeft
DETAILS:		private
DESCRIPTION:	Rotates the bits in a 32 bit DWORD left by a specified amount
RETURNS:		The rotated DWORD 
ARGUMENTS:		DWORD x : the value to be rotated
				int n   : the number of bits to rotate by
*****************************************************************************************/
DWORD CMD5Checksum::RotateLeft(DWORD x, int n)
{
	//check that DWORD is 4 bytes long - true in Visual C++ 6 and 32 bit Windows

	//rotate and return x
	return (x << n) | (x >> (32-n));
}


/*****************************************************************************************
FUNCTION:		CMD5Checksum::FF
DETAILS:		protected
DESCRIPTION:	Implementation of basic MD5 transformation algorithm
RETURNS:		none
ARGUMENTS:		DWORD &A, B, C, D : Current (partial) checksum
				DWORD X           : Input data
				DWORD S			  : MD5_SXX Transformation constant
				DWORD T			  :	MD5_TXX Transformation constant
NOTES:			None
*****************************************************************************************/
void CMD5Checksum::FF( DWORD& A, DWORD B, DWORD C, DWORD D, DWORD X, DWORD S, DWORD T)
{
	DWORD F = (B & C) | (~B & D);
	A += F + X + T;
	A = RotateLeft(A, S);
	A += B;
}


/*****************************************************************************************
FUNCTION:		CMD5Checksum::GG
DETAILS:		protected
DESCRIPTION:	Implementation of basic MD5 transformation algorithm
RETURNS:		none
ARGUMENTS:		DWORD &A, B, C, D : Current (partial) checksum
				DWORD X           : Input data
				DWORD S			  : MD5_SXX Transformation constant
				DWORD T			  :	MD5_TXX Transformation constant
NOTES:			None
*****************************************************************************************/
void CMD5Checksum::GG( DWORD& A, DWORD B, DWORD C, DWORD D, DWORD X, DWORD S, DWORD T)
{
	DWORD G = (B & D) | (C & ~D);
	A += G + X + T;
	A = RotateLeft(A, S);
	A += B;
}


/*****************************************************************************************
FUNCTION:		CMD5Checksum::HH
DETAILS:		protected
DESCRIPTION:	Implementation of basic MD5 transformation algorithm
RETURNS:		none
ARGUMENTS:		DWORD &A, B, C, D : Current (partial) checksum
				DWORD X           : Input data
				DWORD S			  : MD5_SXX Transformation constant
				DWORD T			  :	MD5_TXX Transformation constant
NOTES:			None
*****************************************************************************************/
void CMD5Checksum::HH( DWORD& A, DWORD B, DWORD C, DWORD D, DWORD X, DWORD S, DWORD T)
{
	DWORD H = (B ^ C ^ D);
	A += H + X + T;
	A = RotateLeft(A, S);
	A += B;
}


/*****************************************************************************************
FUNCTION:		CMD5Checksum::II
DETAILS:		protected
DESCRIPTION:	Implementation of basic MD5 transformation algorithm
RETURNS:		none
ARGUMENTS:		DWORD &A, B, C, D : Current (partial) checksum
				DWORD X           : Input data
				DWORD S			  : MD5_SXX Transformation constant
				DWORD T			  :	MD5_TXX Transformation constant
NOTES:			None
*****************************************************************************************/
void CMD5Checksum::II( DWORD& A, DWORD B, DWORD C, DWORD D, DWORD X, DWORD S, DWORD T)
{
	DWORD I = (C ^ (B | ~D));
	A += I + X + T;
	A = RotateLeft(A, S);
	A += B;
}


/*****************************************************************************************
FUNCTION:		CMD5Checksum::ByteToDWord
DETAILS:		private
DESCRIPTION:	Transfers the data in an 8 bit array to a 32 bit array
RETURNS:		void
ARGUMENTS:		DWORD* Output : the 32 bit (unsigned long) destination array 
				BYTE* Input	  : the 8 bit (unsigned char) source array
				UINT nLength  : the number of 8 bit data items in the source array
NOTES:			Four BYTES from the input array are transferred to each DWORD entry
				of the output array. The first BYTE is transferred to the bits (0-7) 
				of the output DWORD, the second BYTE to bits 8-15 etc. 
				The algorithm assumes that the input array is a multiple of 4 bytes long
				so that there is a perfect fit into the array of 32 bit words.
*****************************************************************************************/
void CMD5Checksum::ByteToDWord(DWORD* Output, BYTE* Input, UINT nLength)
{
	//entry invariants

	//initialisations
	UINT i=0;	//index to Output array
	UINT j=0;	//index to Input array

	//transfer the data by shifting and copying
	for ( ; j < nLength; i++, j += 4)
	{
		Output[i] = (ULONG)Input[j]			| 
					(ULONG)Input[j+1] << 8	| 
					(ULONG)Input[j+2] << 16 | 
					(ULONG)Input[j+3] << 24;
	}
}

/*****************************************************************************************
FUNCTION:		CMD5Checksum::Transform
DETAILS:		protected
DESCRIPTION:	MD5 basic transformation algorithm;  transforms 'm_lMD5'
RETURNS:		void
ARGUMENTS:		BYTE Block[64]
NOTES:			An MD5 checksum is calculated by four rounds of 'Transformation'.
				The MD5 checksum currently held in m_lMD5 is merged by the 
				transformation process with data passed in 'Block'.  
*****************************************************************************************/
void CMD5Checksum::Transform(BYTE Block[64])
{
	//initialise local data with current checksum
	ULONG a = m_lMD5[0];
	ULONG b = m_lMD5[1];
	ULONG c = m_lMD5[2];
	ULONG d = m_lMD5[3];