source: lib/sha1.c @ 7f4016b

/*
 * SHA1 hashing code copied from Lepton's crack <http://usuarios.lycos.es/reinob/>
 *
 * Adapted to be API-compatible with the previous (GPL-incompatible) code.
 */

/*
 *  sha1.c
 *
 *  Description:
 *      This file implements the Secure Hashing Algorithm 1 as
 *      defined in FIPS PUB 180-1 published April 17, 1995.
 *
 *      The SHA-1, produces a 160-bit message digest for a given
 *      data stream.  It should take about 2**n steps to find a
 *      message with the same digest as a given message and
 *      2**(n/2) to find any two messages with the same digest,
 *      when n is the digest size in bits.  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
 *      uses <stdint.h> (included via "sha1.h" to define 32 and 8
 *      bit unsigned integer types.  If your C compiler does not
 *      support 32 bit unsigned integers, this code is not
 *      appropriate.
 *
 *  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 SHA1 circular left shift macro
 */
#define SHA1CircularShift(bits,word) \
       (((word) << (bits)) | ((word) >> (32-(bits))))

/* Local Function Prototyptes */
static void sha1_pad(sha1_state_t *);
static void sha1_process_block(sha1_state_t *);

/*
 *  sha1_init
 *
 *  Description:
 *      This function will initialize the sha1_state_t in preparation
 *      for computing a new SHA1 message digest.
 *
 *  Parameters:
 *      context: [in/out]
 *          The context to reset.
 *
 *  Returns:
 *      sha Error Code.
 *
 */
int sha1_init(sha1_state_t * context)
{
        context->Length_Low = 0;
        context->Length_High = 0;
        context->Message_Block_Index = 0;

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

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

/*
 *  sha1_finish
 *
 *  Description:
 *      This function will return the 160-bit message digest into the
 *      Message_Digest array  provided by the caller.
 *      NOTE: The first octet of hash is stored in the 0th element,
 *            the last octet of hash in the 19th element.
 *
 *  Parameters:
 *      context: [in/out]
 *          The context to use to calculate the SHA-1 hash.
 *      Message_Digest: [out]
 *          Where the digest is returned.
 *
 *  Returns:
 *      sha Error Code.
 *
 */
int sha1_finish(sha1_state_t * context, uint8_t Message_Digest[sha1_hash_size])
{
        int i;

        if (!context || !Message_Digest) {
                return shaNull;
        }

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

        if (!context->Computed) {
                sha1_pad(context);
                for (i = 0; i < 64; ++i) {
                        /* message may be sensitive, clear it out */
                        context->Message_Block[i] = 0;
                }
                context->Length_Low = 0;        /* and clear length */
                context->Length_High = 0;
                context->Computed = 1;

        }

        for (i = 0; i < sha1_hash_size; ++i) {
                Message_Digest[i] = context->Intermediate_Hash[i >> 2]
                    >> 8 * (3 - (i & 0x03));
        }

        return shaSuccess;
}

/*
 *  sha1_append
 *
 *  Description:
 *      This function accepts an array of octets as the next portion
 *      of the message.
 *
 *  Parameters:
 *      context: [in/out]
 *          The SHA 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:
 *      sha Error Code.
 *
 */
int
sha1_append(sha1_state_t * context,
          const uint8_t * message_array, unsigned length)
{
        if (!length) {
                return shaSuccess;
        }

        if (!context || !message_array) {
                return shaNull;
        }

        if (context->Computed) {
                context->Corrupted = shaStateError;

                return shaStateError;
        }

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

                context->Length_Low += 8;
                if (context->Length_Low == 0) {
                        context->Length_High++;
                        if (context->Length_High == 0) {
                                /* Message is too long */
                                context->Corrupted = 1;
                        }
                }

                if (context->Message_Block_Index == 64) {
                        sha1_process_block(context);
                }

                message_array++;
        }

        return shaSuccess;
}

/*
 *  sha1_process_block
 *
 *  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 code, especially the
 *      single character names, were used because those were the
 *      names used in the publication.
 *
 *
 */
static void sha1_process_block(sha1_state_t * context)
{
        const uint32_t K[] = {  /* Constants defined in SHA-1   */
                0x5A827999,
                0x6ED9EBA1,
                0x8F1BBCDC,
                0xCA62C1D6
        };
        int t;                  /* Loop counter                */
        uint32_t temp;          /* Temporary word value        */
        uint32_t W[80];         /* Word sequence               */
        uint32_t A, B, C, D, E; /* Word buffers                */

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

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

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

        context->Message_Block_Index = 0;
}

/*
 *  sha1_pad
 *
 *  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 the ProcessMessageBlock function
 *      provided appropriately.  When it returns, it can be assumed that
 *      the message digest has been computed.
 *
 *  Parameters:
 *      context: [in/out]
 *          The context to pad
 *      ProcessMessageBlock: [in]
 *          The appropriate SHA*ProcessMessageBlock function
 *  Returns:
 *      Nothing.
 *
 */

static void sha1_pad(sha1_state_t * 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;
                }

                sha1_process_block(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;
        context->Message_Block[57] = context->Length_High >> 16;
        context->Message_Block[58] = context->Length_High >> 8;
        context->Message_Block[59] = context->Length_High;
        context->Message_Block[60] = context->Length_Low >> 24;
        context->Message_Block[61] = context->Length_Low >> 16;
        context->Message_Block[62] = context->Length_Low >> 8;
        context->Message_Block[63] = context->Length_Low;

        sha1_process_block(context);
}