/*
 *  sha1.cpp
 *
 *  Copyright (C) 1998, 2009
 *  Paul E. Jones <paulej@packetizer.com>
 *  All Rights Reserved.
 *
 *****************************************************************************
 *  $Id: sha1.cpp 12 2009-06-22 19:34:25Z paulej $
 *****************************************************************************
 *
 *  Description:
 *      This class 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.
 *
 *  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 8
 *      bits.
 *
 */

#include <string.h>

#include "sha1.h"

/*
 *  Reset
 *
 *  Description:
 *      This function will initialize the sha1 class member variables
 *      in preparation for computing a new message digest.
 *
 *  Parameters:
 *      None.
 *
 *  Returns:
 *      Nothing.
 *
 *  Comments:
 *
 */
void SHA1::Reset()
{
	Length_Low          = 0;
	Length_High         = 0;
	Message_Block_Index = 0;

	H[0]        = 0x67452301;
	H[1]        = 0xEFCDAB89;
	H[2]        = 0x98BADCFE;
	H[3]        = 0x10325476;
	H[4]        = 0xC3D2E1F0;

	Computed    = false;
	Corrupted   = false;
}

/*
 *  Result
 *
 *  Description:
 *      This function will return the 160-bit message digest into the
 *      array provided.
 *
 *  Parameters:
 *      message_digest_array: [out]
 *          This is an array of five uint32 integers which will be filled
 *          with the message digest that has been computed.
 *
 *  Returns:
 *      True if successful, false if it failed.
 *
 *  Comments:
 *
 */
bool SHA1::Result(uint8 *message_digest_array )
{
	if (Corrupted) {
		return false;
	}

	if (!Computed) {
		PadMessage();
		Computed = true;
	}

#ifdef SIM_BIG_ENDIAN
	uint32 H_little_endian[5];
	for(int i = 0; i < 5; i++) {
		H_little_endian[i] = endian( H[i] );
	}
	memcpy( message_digest_array, H_little_endian, 20 );
#else
	memcpy( message_digest_array, H, 20 );
#endif

	return true;
}

/*
 *  Input
 *
 *  Description:
 *      This function accepts an array of octets as the next portion of
 *      the message.
 *
 *  Parameters:
 *      message_array: [in]
 *          An array of characters representing the next portion of the
 *          message.
 *
 *  Returns:
 *      Nothing.
 *
 *  Comments:
 *
 */
void SHA1::Input( const char *message_array, uint32 length)
{
	if (!length) {
		return;
	}

	if (Computed || Corrupted) {
		Corrupted = true;
		return;
	}

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

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

		if (Message_Block_Index == 64) {
			ProcessMessageBlock();
		}

		message_array++;
	}
}

/*
 *  Input
 *
 *  Description:
 *      This function accepts a single octets as the next message element.
 *
 *  Parameters:
 *      message_element: [in]
 *          The next octet in the message.
 *
 *  Returns:
 *      Nothing.
 *
 *  Comments:
 *
 */
void SHA1::Input(char message_element)
{
	Input(&message_element, 1);
}

/*
 *  ProcessMessageBlock
 *
 *  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 this function, especially the single
 *      character names, were used because those were the names used
 *      in the publication.
 *
 */
void SHA1::ProcessMessageBlock()
{
	const uint32 K[] =    {               // Constants defined for SHA-1
								0x5A827999,
								0x6ED9EBA1,
								0x8F1BBCDC,
								0xCA62C1D6
							};
	int         t;                          // Loop counter
	uint32    temp;                       // Temporary word value
	uint32    W[80];                      // Word sequence
	uint32    A, B, C, D, E;              // Word buffers

	/*
	 *  Initialize the first 16 words in the array W
	 */
	for(t = 0; t < 16; t++) {
		W[t] = ((uint32) Message_Block[t * 4]) << 24;
		W[t] |= ((uint32) Message_Block[t * 4 + 1]) << 16;
		W[t] |= ((uint32) Message_Block[t * 4 + 2]) << 8;
		W[t] |= ((uint32) Message_Block[t * 4 + 3]);
	}

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

	A = H[0];
	B = H[1];
	C = H[2];
	D = H[3];
	E = H[4];

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

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

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

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

	H[0] = (H[0] + A) & 0xFFFFFFFF;
	H[1] = (H[1] + B) & 0xFFFFFFFF;
	H[2] = (H[2] + C) & 0xFFFFFFFF;
	H[3] = (H[3] + D) & 0xFFFFFFFF;
	H[4] = (H[4] + E) & 0xFFFFFFFF;

	Message_Block_Index = 0;
}

/*
 *  PadMessage
 *
 *  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 ProcessMessageBlock() appropriately.  When it returns, it
 *      can be assumed that the message digest has been computed.
 *
 *  Parameters:
 *      None.
 *
 *  Returns:
 *      Nothing.
 *
 *  Comments:
 *
 */
void SHA1::PadMessage()
{
	/*
	 *  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 (Message_Block_Index > 55) {
		Message_Block[Message_Block_Index++] = 0x80;
		while(Message_Block_Index < 64) {
			Message_Block[Message_Block_Index++] = 0;
		}

		ProcessMessageBlock();

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

	}

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

	ProcessMessageBlock();
}


/*
 *  CircularShift
 *
 *  Description:
 *      This member function will perform a circular shifting operation.
 *
 *  Parameters:
 *      bits: [in]
 *          The number of bits to shift (1-31)
 *      word: [in]
 *          The value to shift (assumes a 32-bit integer)
 *
 *  Returns:
 *      The shifted value.
 *
 *  Comments:
 *
 */
uint32 SHA1::CircularShift(int bits, uint32 word)
{
	return ((word << bits) & 0xFFFFFFFF) | ((word & 0xFFFFFFFF) >> (32-bits));
}
