sah-1.txt

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/*
 *  sha1.h
 *
 *  Description:
 *      This is the header file for code which implements the Secure
 *      Hashing Algorithm 1 as defined in FIPS PUB 180-1 published
 *      April 17, 1995.
 *
 *      Many of the variable names in this code, especially the
 *      single character names, were used because those were the names
 *      used in the publication.
 *
 *      Please read the file sha1.c for more information.
 *
 */

#ifndef _SHA1_H_
#define _SHA1_H_

#include <stdint.h>
/*
 * If you do not have the ISO standard stdint.h header file, then you
 * must typdef the following:
 *    name              meaning
 *  uint32_t         unsigned 32 bit integer
 *  uint8_t          unsigned 8 bit integer (i.e., unsigned char)
 *  int_least16_t    integer of >= 16 bits
 *
 */

#ifndef _SHA_enum_
#define _SHA_enum_
enum
{
    shaSuccess = 0,
    shaNull,            /* Null pointer parameter */
    shaInputTooLong,    /* input data too long */
    shaStateError       /* called Input after Result */
};
#endif
#define SHA1HashSize 20

/*
 *  This structure will hold context information for the SHA-1
 *  hashing operation
 */
typedef struct SHA1Context
{
    uint32_t Intermediate_Hash[SHA1HashSize/4]; /* Message Digest  */

    uint32_t Length_Low;            /* Message length in bits      */
    uint32_t Length_High;           /* Message length in bits      */

                               /* Index into message block array   */
    int_least16_t Message_Block_Index;
    uint8_t Message_Block[64];      /* 512-bit message blocks      */

    int Computed;               /* Is the digest computed?         */
    int Corrupted;             /* Is the message digest corrupted? */
} SHA1Context;

/*
 *  Function Prototypes
 */

int SHA1Reset(  SHA1Context *);
int SHA1Input(  SHA1Context *,
                const uint8_t *,
                unsigned int);
int SHA1Result( SHA1Context *,
                uint8_t Message_Digest[SHA1HashSize]);

#endif

7.2 .c file

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

/*
 *  SHA1Reset
 *
 *  Description:
 *      This function will initialize the SHA1Context in preparation
 *      for computing a new SHA1 message digest.
 *
 *  Parameters:
 *      context: [in/out]
 *          The context to reset.
 *
 *  Returns:
 *      sha Error Code.
 *
 */
int SHA1Reset(SHA1Context *context)
{
    if (!context)
    {
        return shaNull;
    }

    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;
}

/*
 *  SHA1Result
 *
 *  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 SHA1Result( SHA1Context *context,
                uint8_t Message_Digest[SHA1HashSize])
{
    int i;

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

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

    if (!context->Computed)
    {
        SHA1PadMessage(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 < SHA1HashSize; ++i)
    {
        Message_Digest[i] = context->Intermediate_Hash[i>>2]
                            >> 8 * ( 3 - ( i & 0x03 ) );
    }

    return shaSuccess;
}

/*
 *  SHA1Input
 *
 *  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 SHA1Input(    SHA1Context    *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)
    {
        SHA1ProcessMessageBlock(context);
    }

    message_array++;
    }

    return shaSuccess;
}

/*
 *  SHA1ProcessMessageBlock
 *
 *  Description:
 *      This function will process the next 512 bits of the message
 *      stored in the Message_Block array.