crypto-mcf.c

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

#ifndef S_SPLINT_S /* Including this here triggers a known bug in splint */
//#include <unistd.h>
#endif

#include "libscrypt.h"

/* ilog2 for powers of two */
static uint32_t scrypt_ilog2(uint32_t n)
{
#ifndef S_SPLINT_S

        /* Check for a valid power of two */
        if (n < 2 || (n & (n - 1)))
                return -1;
#endif
        uint32_t t = 1;
        while (((uint32_t)1 << t) < n)
        {
                if(t > SCRYPT_SAFE_N)
                        return (uint32_t) -1; /* Check for insanity */
                t++;
        }

        return t;
}

#ifdef _MSC_VER
  #define SNPRINTF _snprintf
#else
  #define SNPRINTF snprintf
#endif

int libscrypt_mcf(uint32_t N, uint32_t r, uint32_t p, const char *salt,
                const char *hash, char *mcf)
{

        uint32_t t, params;
        int s;

        if(!mcf || !hash)
                return 0;
        /* Although larger values of r, p are valid in scrypt, this mcf format
        * limits to 8 bits. If your number is larger, current computers will
        * struggle
        */
        if(r > (uint8_t)(-1) || p > (uint8_t)(-1))
                return 0;

        t = scrypt_ilog2(N);
        if (t < 1)
                return 0;
                
        params = (r << 8) + p;
        params += (uint32_t)t << 16;
        
        /* Using snprintf - not checking for overflows. We've already
        * determined that mcf should be defined as at least SCRYPT_MCF_LEN
        * in length 
        */
        s = SNPRINTF(mcf, SCRYPT_MCF_LEN,  SCRYPT_MCF_ID "$%06x$%s$%s", (unsigned int)params, salt, hash);
        if (s > SCRYPT_MCF_LEN)
                return 0;

        return 1;
}