/*****************************************************************************************

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

***		Developed by Langfine Ltd. 
***		Released to the public domain 12/Nov/2001.
***		Please visit our website www.langfine.com

***		Any modifications must be clearly commented to distinguish them from Langfine's 
***		original source code. Please advise Langfine of useful modifications so that we 
***		can make them generally available. 

*****************************************************************************************/


/****************************************************************************************
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 "MD5Checksum.h"
#include "MD5ChecksumDefines.h"

#ifdef _DEBUG
#undef THIS_FILE
static char THIS_FILE[]=__FILE__;
#define new DEBUG_NEW
#endif


/*****************************************************************************************
FUNCTION:		CMD5Checksum::GetMD5
DETAILS:		static, public
DESCRIPTION:	Gets the MD5 checksum for a specified file
RETURNS:		CString : the hexadecimal MD5 checksum for the specified file
ARGUMENTS:		CString& strFilePath : the full pathname of the specified file
NOTES:			Provides an interface to the CMD5Checksum class. 'strFilePath' name should 
				hold the full pathname of the file, eg C:\My Documents\Arcticle.txt.
				NB. If any problems occur with opening or reading this file, a CFileException
				will be thrown; callers of this function should be ready to catch this 
				exception.
*****************************************************************************************/
CString CMD5Checksum::GetMD5(const CString& strFilePath)
{
	//open the file as a binary file in readonly mode, denying write access 
	CFile File(strFilePath, CFile::modeRead | CFile::shareDenyWrite | CFile::typeBinary);

	//the file has been successfully opened, so now get and return its checksum
	return GetMD5(File);
}


/*****************************************************************************************
FUNCTION:		CMD5Checksum::GetMD5
DETAILS:		static, public
DESCRIPTION:	Gets the MD5 checksum for a specified file
RETURNS:		CString : the hexadecimal MD5 checksum for the specified file
ARGUMENTS:		CFile& File : the specified file
NOTES:			Provides an interface to the CMD5Checksum class. 'File' should be open in 
				binary readonly mode before calling this function. 
				NB. Callers of this function should be ready to catch any CFileException
				thrown by the CFile functions
*****************************************************************************************/
CString CMD5Checksum::GetMD5(CFile& File)
{
	try
	{
		CMD5Checksum MD5Checksum;		//checksum object	
		int nLength = 0;				//number of bytes read from the file
		const int nBufferSize = 1024;	//checksum the file in blocks of 1024 bytes
		BYTE Buffer[nBufferSize];		//buffer for data read from the file

		//checksum the file in blocks of 1024 bytes
		while ((nLength = File.Read( Buffer, nBufferSize )) > 0 )
		{
			MD5Checksum.Update( Buffer, nLength );
		}

		//finalise the checksum and return it
		return MD5Checksum.Final();
	}

	//report any file exceptions in debug mode only
	catch (CFileException* e )
	{
		TRACE0("CMD5Checksum::GetMD5: CFileException caught");	
		throw e;
	}
}


/*****************************************************************************************
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. 
*****************************************************************************************/
CString CMD5Checksum::GetMD5(BYTE* pBuf, UINT nLength)
{
	//entry invariants
	AfxIsValidAddress(pBuf,nLength,FALSE);

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


/*****************************************************************************************
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
	ASSERT( sizeof(x) == 4 );

	//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