/*
*  sha1.c
*
*	Copyright (C) 1998
*	Paul E. Jones <paulej@arid.us>
*	All Rights Reserved
*
*****************************************************************************
*	$Id: sha1.c,v 1.2 2004/03/27 18:00:33 paulej Exp $
*****************************************************************************
*
*  Description:
*      This file implements the Secure Hashing Standard as defined
*      in FIPS PUB 180-1 published April 17, 1995.
*
*      The Secure Hashing Standard, which uses the Secure Hashing
*      Algorithm (SHA), produces a 160-bit message digest for a
*      given data stream.  In theory, it is highly improbable that
*      two messages will produce the same message digest.  Therefore,
*      this algorithm can serve as a means of providing a "fingerprint"
*      for a message.
*
*  Portability Issues:
*      SHA-1 is defined in terms of 32-bit "words".  This code was
*      written with the expectation that the processor has at least
*      a 32-bit machine word size.  If the machine word size is larger,
*      the code should still function properly.  One caveat to that
*      is that the input functions taking characters and character
*      arrays assume that only 8 bits of information are stored in each
*      character.
*
*  Caveats:
*      SHA-1 is designed to work with messages less than 2^64 bits
*      long. Although SHA-1 allows a message digest to be generated for
*      messages of any number of bits less than 2^64, this
*      implementation only works with messages with a length that is a
*      multiple of the size of an 8-bit character.
*
*/

#include "sha1.h"

/*
*  Define the circular shift macro
*/
#define SHA1CircularShift(bits,word) \
	((((word) << (bits)) & 0xFFFFFFFF) | \
	((word) >> (32-(bits))))

/* Function prototypes */
void SHA1ProcessMessageBlock(SHA1Context *);
void SHA1PadMessage(SHA1Context *);

/*  
*  SHA1Reset
*
*  Description:
*      This function will initialize the SHA1Context in preparation
*      for computing a new message digest.
*
*  Parameters:
*      context: [in/out]
*          The context to reset.
*
*  Returns:
*      Nothing.
*
*  Comments:
*
*/
void SHA1Reset(SHA1Context *context)
{
	context->Length_Low             = 0;
	context->Length_High            = 0;
	context->Message_Block_Index    = 0;

	context->Message_Digest[0]      = 0x67452301;
	context->Message_Digest[1]      = 0xEFCDAB89;
	context->Message_Digest[2]      = 0x98BADCFE;
	context->Message_Digest[3]      = 0x10325476;
	context->Message_Digest[4]      = 0xC3D2E1F0;

	context->Computed   = 0;
	context->Corrupted  = 0;
}

/*  
*  SHA1Result
*
*  Description:
*      This function will return the 160-bit message digest into the
*      Message_Digest array within the SHA1Context provided
*
*  Parameters:
*      context: [in/out]
*          The context to use to calculate the SHA-1 hash.
*
*  Returns:
*      1 if successful, 0 if it failed.
*
*  Comments:
*
*/
int SHA1Result(SHA1Context *context)
{

	if (context->Corrupted)
	{
		return 0;
	}

	if (!context->Computed)
	{
		SHA1PadMessage(context);
		context->Computed = 1;
	}

	return 1;
}

/*  
*  SHA1Input
*
*  Description:
*      This function accepts an array of octets as the next portion of
*      the message.
*
*  Parameters:
*      context: [in/out]
*          The SHA-1 context to update
*      message_array: [in]
*          An array of characters representing the next portion of the
*          message.
*      length: [in]
*          The length of the message in message_array
*
*  Returns:
*      Nothing.
*
*  Comments:
*
*/
void SHA1Input(     SHA1Context         *context,
	const unsigned char *message_array,
	unsigned            length)
{
	if (!length)
	{
		return;
	}

	if (context->Computed || context->Corrupted)
	{
		context->Corrupted = 1;
		return;
	}

	while(length-- && !context->Corrupted)
	{
		context->Message_Block[context->Message_Block_Index++] =
			(*message_array & 0xFF);

		context->Length_Low += 8;
		/* Force it to 32 bits */
		context->Length_Low &= 0xFFFFFFFF;
		if (context->Length_Low == 0)
		{
			context->Length_High++;
			/* Force it to 32 bits */
			context->Length_High &= 0xFFFFFFFF;
			if (context->Length_High == 0)
			{
				/* Message is too long */
				context->Corrupted = 1;
			}
		}

		if (context->Message_Block_Index == 64)
		{
			SHA1ProcessMessageBlock(context);
		}

		message_array++;
	}
}

/*  
*  SHA1ProcessMessageBlock
*
*  Description:
*      This function will process the next 512 bits of the message
*      stored in the Message_Block array.
*
*  Parameters:
*      None.
*
*  Returns:
*      Nothing.
*
*  Comments:
*      Many of the variable names in the SHAContext, especially the
*      single character names, were used because those were the names
*      used in the publication.
*         
*
*/
void SHA1ProcessMessageBlock(SHA1Context *context)
{
	const unsigned K[] =            /* Constants defined in SHA-1   */      
	{
		0x5A827999,
		0x6ED9EBA1,
		0x8F1BBCDC,
		0xCA62C1D6
	};
	int         t;                  /* Loop counter                 */
	unsigned    temp;               /* Temporary word value         */
	unsigned    W[80];              /* Word sequence                */
	unsigned    A, B, C, D, E;      /* Word buffers                 */

	/*
	*  Initialize the first 16 words in the array W
	*/
	for(t = 0; t < 16; t++)
	{
		W[t] = ((unsigned) context->Message_Block[t * 4]) << 24;
		W[t] |= ((unsigned) context->Message_Block[t * 4 + 1]) << 16;
		W[t] |= ((unsigned) context->Message_Block[t * 4 + 2]) << 8;
		W[t] |= ((unsigned) context->Message_Block[t * 4 + 3]);
	}

	for(t = 16; t < 80; t++)
	{
		W[t] = SHA1CircularShift(1,W[t-3] ^ W[t-8] ^ W[t-14] ^ W[t-16]);
	}

	A = context->Message_Digest[0];
	B = context->Message_Digest[1];
	C = context->Message_Digest[2];
	D = context->Message_Digest[3];
	E = context->Message_Digest[4];

	for(t = 0; t < 20; t++)
	{
		temp =  SHA1CircularShift(5,A) +
			((B & C) | ((~B) & D)) + E + W[t] + K[0];
		temp &= 0xFFFFFFFF;
		E = D;
		D = C;
		C = SHA1CircularShift(30,B);
		B = A;
		A = temp;
	}

	for(t = 20; t < 40; t++)
	{
		temp = SHA1CircularShift(5,A) + (B ^ C ^ D) + E + W[t] + K[1];
		temp &= 0xFFFFFFFF;
		E = D;
		D = C;
		C = SHA1CircularShift(30,B);
		B = A;
		A = temp;
	}

	for(t = 40; t < 60; t++)
	{
		temp = SHA1CircularShift(5,A) +
			((B & C) | (B & D) | (C & D)) + E + W[t] + K[2];
		temp &= 0xFFFFFFFF;
		E = D;
		D = C;
		C = SHA1CircularShift(30,B);
		B = A;
		A = temp;
	}

	for(t = 60; t < 80; t++)
	{
		temp = SHA1CircularShift(5,A) + (B ^ C ^ D) + E + W[t] + K[3];
		temp &= 0xFFFFFFFF;
		E = D;
		D = C;
		C = SHA1CircularShift(30,B);
		B = A;
		A = temp;
	}

	context->Message_Digest[0] =
		(context->Message_Digest[0] + A) & 0xFFFFFFFF;
	context->Message_Digest[1] =
		(context->Message_Digest[1] + B) & 0xFFFFFFFF;
	context->Message_Digest[2] =
		(context->Message_Digest[2] + C) & 0xFFFFFFFF;
	context->Message_Digest[3] =
		(context->Message_Digest[3] + D) & 0xFFFFFFFF;
	context->Message_Digest[4] =
		(context->Message_Digest[4] + E) & 0xFFFFFFFF;

	context->Message_Block_Index = 0;
}

/*  
*  SHA1PadMessage
*
*  Description:
*      According to the standard, the message must be padded to an even
*      512 bits.  The first padding bit must be a '1'.  The last 64
*      bits represent the length of the original message.  All bits in
*      between should be 0.  This function will pad the message
*      according to those rules by filling the Message_Block array
*      accordingly.  It will also call SHA1ProcessMessageBlock()
*      appropriately.  When it returns, it can be assumed that the
*      message digest has been computed.
*
*  Parameters:
*      context: [in/out]
*          The context to pad
*
*  Returns:
*      Nothing.
*
*  Comments:
*
*/
void SHA1PadMessage(SHA1Context *context)
{
	/*
	*  Check to see if the current message block is too small to hold
	*  the initial padding bits and length.  If so, we will pad the
	*  block, process it, and then continue padding into a second
	*  block.
	*/
	if (context->Message_Block_Index > 55)
	{
		context->Message_Block[context->Message_Block_Index++] = 0x80;
		while(context->Message_Block_Index < 64)
		{
			context->Message_Block[context->Message_Block_Index++] = 0;
		}

		SHA1ProcessMessageBlock(context);

		while(context->Message_Block_Index < 56)
		{
			context->Message_Block[context->Message_Block_Index++] = 0;
		}
	}
	else
	{
		context->Message_Block[context->Message_Block_Index++] = 0x80;
		while(context->Message_Block_Index < 56)
		{
			context->Message_Block[context->Message_Block_Index++] = 0;
		}
	}

	/*
	*  Store the message length as the last 8 octets
	*/
	context->Message_Block[56] = (context->Length_High >> 24) & 0xFF;
	context->Message_Block[57] = (context->Length_High >> 16) & 0xFF;
	context->Message_Block[58] = (context->Length_High >> 8) & 0xFF;
	context->Message_Block[59] = (context->Length_High) & 0xFF;
	context->Message_Block[60] = (context->Length_Low >> 24) & 0xFF;
	context->Message_Block[61] = (context->Length_Low >> 16) & 0xFF;
	context->Message_Block[62] = (context->Length_Low >> 8) & 0xFF;
	context->Message_Block[63] = (context->Length_Low) & 0xFF;

	SHA1ProcessMessageBlock(context);
}