/*
 *	sha1.cpp
 *
 *	Copyright (C) 1998
 *	Paul E. Jones <paulej@arid.us>
 *	All Rights Reserved.
 *
 *****************************************************************************
 *	$Id: sha1.cpp,v 1.9 2004/03/27 18:02:20 paulej Exp $
 *****************************************************************************
 *
 *	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.
 *
 *	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 8
 * 		bits.
 *
 */


#include "sha1.h"

/*	
 *	SHA1
 *
 *	Description:
 *		This is the constructor for the sha1 class.
 *
 *	Parameters:
 *		None.
 *
 *	Returns:
 *		Nothing.
 *
 *	Comments:
 *
 */
SHA1::SHA1()
{
	Reset();
}

/*	
 *	~SHA1
 *
 *	Description:
 *		This is the destructor for the sha1 class
 *
 *	Parameters:
 *		None.
 *
 *	Returns:
 *		Nothing.
 *
 *	Comments:
 *
 */
SHA1::~SHA1()
{
	// The destructor does nothing
}

/*	
 *	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 unsigned 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(unsigned *message_digest_array)
{
	int i;									// Counter

	if (Corrupted)
	{
		return false;
	}

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

	for(i = 0; i < 5; i++)
	{
		message_digest_array[i] = H[i];
	}

	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 unsigned char	*message_array,
					unsigned 			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 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.
 *		length: [in]
 *			The length of the message_array
 *
 *	Returns:
 *		Nothing.
 *
 *	Comments:
 *
 */
void SHA1::Input(	const char	*message_array,
					unsigned 	length)
{
	Input(reinterpret_cast<unsigned char *>(const_cast<char *>(message_array)), length);
}

/*	
 *	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(unsigned char message_element)
{
	Input(&message_element, 1);
}

/*	
 *	Input
 *
 *	Description:
 *		This function accepts a single octet 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((unsigned char *) &message_element, 1);
}

/*	
 *	operator<<
 *
 *	Description:
 *		This operator makes it convenient to provide character strings to
 *		the SHA1 object for processing.
 *
 *	Parameters:
 *		message_array: [in]
 *			The character array to take as input.
 *
 *	Returns:
 *		A reference to the SHA1 object.
 *
 *	Comments:
 *		Each character is assumed to hold 8 bits of information.
 *
 */
SHA1& SHA1::operator<<(const char *message_array)
{
	const char *p = message_array;

	while(*p)
	{
		Input(*p);
		p++;
	}

	return *this;
}

/*	
 *	operator<<
 *
 *	Description:
 *		This operator makes it convenient to provide character strings to
 *		the SHA1 object for processing.
 *
 *	Parameters:
 *		message_array: [in]
 *			The character array to take as input.
 *
 *	Returns:
 *		A reference to the SHA1 object.
 *
 *	Comments:
 *		Each character is assumed to hold 8 bits of information.
 *
 */
SHA1& SHA1::operator<<(const unsigned char *message_array)
{
	const unsigned char *p = message_array;

	while(*p)
	{
		Input(*p);
		p++;
	}

	return *this;
}

/*	
 *	operator<<
 *
 *	Description:
 *		This function provides the next octet in the message.
 *
 *	Parameters:
 *		message_element: [in]
 *			The next octet in the message
 *
 *	Returns:
 *		A reference to the SHA1 object.
 *
 *	Comments:
 *		The character is assumed to hold 8 bits of information.
 *
 */
SHA1& SHA1::operator<<(const char message_element)
{
	Input(reinterpret_cast<unsigned char *>(const_cast<char *>(&message_element)), 1);

	return *this;
}

/*	
 *	operator<<
 *
 *	Description:
 *		This function provides the next octet in the message.
 *
 *	Parameters:
 *		message_element: [in]
 *			The next octet in the message
 *
 *	Returns:
 *		A reference to the SHA1 object.
 *
 *	Comments:
 *		The character is assumed to hold 8 bits of information.
 *
 */
SHA1& SHA1::operator<<(const unsigned char message_element)
{
	Input(&message_element, 1);

	return *this;
}

/*	
 *	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 unsigned K[] = 	{ 				// Constants defined for 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) Message_Block[t * 4]) << 24;
		W[t] |= ((unsigned) Message_Block[t * 4 + 1]) << 16;
		W[t] |= ((unsigned) Message_Block[t * 4 + 2]) << 8;
		W[t] |= ((unsigned) 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] = static_cast<unsigned char>((Length_High >> 24) & 0xFF);
	Message_Block[57] = static_cast<unsigned char>((Length_High >> 16) & 0xFF);
	Message_Block[58] = static_cast<unsigned char>((Length_High >> 8) & 0xFF);
	Message_Block[59] = static_cast<unsigned char>((Length_High) & 0xFF);
	Message_Block[60] = static_cast<unsigned char>((Length_Low >> 24) & 0xFF);
	Message_Block[61] = static_cast<unsigned char>((Length_Low >> 16) & 0xFF);
	Message_Block[62] = static_cast<unsigned char>((Length_Low >> 8) & 0xFF);
	Message_Block[63] = static_cast<unsigned char>((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:
 *
 */
unsigned SHA1::CircularShift(int bits, unsigned word)
{
	return ((word << bits) & 0xFFFFFFFF) | ((word & 0xFFFFFFFF) >> (32-bits));
}
