crypto_scrypt-check.c

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#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <math.h>

#include "b64.h"
#include "slowequals.h"
#include "libscrypt.h"

#if defined(_WIN32)
/* On windows, strtok uses a thread-local static variable in strtok to
 * make strtok thread-safe.  It also neglects to provide a strtok_r. */
#define strtok_r(str, val, saveptr) strtok((str), (val))
#endif

int libscrypt_check(char *mcf, const char *password)
{
        /* Return values:
        * <0 error
        * == 0 password incorrect
        * >0 correct password
        */

#ifndef _WIN32
        char *saveptr = NULL;
#endif
        uint32_t params;
        uint64_t N;
        uint8_t r, p;
        int retval;
        uint8_t hashbuf[64];
        char outbuf[128];
        uint8_t salt[32];
        char *tok;

        if(memcmp(mcf, SCRYPT_MCF_ID, 3) != 0)
        {
                /* Only version 0 supported */
                return -1;
        }

        tok = strtok_r(mcf, "$", &saveptr);
        if ( !tok )
                return -1;

        tok = strtok_r(NULL, "$", &saveptr);

        if ( !tok )
                return -1;

        params = (uint32_t)strtoul(tok, NULL, 16);
        if ( params == 0 )
                return -1;

        tok = strtok_r(NULL, "$", &saveptr);

        if ( !tok )
                return -1;

        p = params & 0xff;
        r = (params >> 8) & 0xff;
        N = params >> 16;

        if (N > SCRYPT_SAFE_N)
                return -1;

        N = (uint64_t)1 << N;

        /* Useful debugging:
        printf("We've obtained salt 'N' r p of '%s' %d %d %d\n", tok, N,r,p);
        */

        memset(salt, 0, sizeof(salt)); /* Keeps splint happy */
        retval = libscrypt_b64_decode(tok, (unsigned char*)salt, sizeof(salt));
        if (retval < 1)
                return -1;

        retval = libscrypt_scrypt((uint8_t*)password, strlen(password), salt,
            (uint32_t)retval, N, r, p, hashbuf, sizeof(hashbuf));

        if (retval != 0)
                return -1;

        retval = libscrypt_b64_encode((unsigned char*)hashbuf, sizeof(hashbuf), 
            outbuf, sizeof(outbuf));

        if (retval == 0)
                return -1;

        tok = strtok_r(NULL, "$", &saveptr);

        if ( !tok )
                return -1;

        if(slow_equals(tok, outbuf) == 0)
                return 0;

        return 1; /* This is the "else" condition */
}