Sha1.cpp

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/*
*       Sha1.cpp
*
*       Copyright (C) 1998
*       Paul E. Jones <paulej@acm.org>
*       All Rights Reserved.
*
*****************************************************************************
*       $Id: sha1.cpp,v 1.6 2001/03/20 06:54:54 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((unsigned 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((unsigned 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] = Message_Block[t * 4] << 24;
                W[t] |= Message_Block[t * 4 + 1] << 16;
                W[t] |= Message_Block[t * 4 + 2] << 8;
                W[t] |= 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:
*
*/
unsigned SHA1::CircularShift(int bits, unsigned word)
{
        return ((word << bits) & 0xFFFFFFFF) | ((word & 0xFFFFFFFF) >> (32-bits));
}