RandomSeed.c

static void RandomSeed(void)
{
    /* 1. Seed the weak C PRNGs. */

    /* Mix various stuff. */
    pid_t pid = getpid();
    size_t fqdn_len = strlen(VFQNAME) > 0 ? strlen(VFQNAME) : 1;
    time_t start_time = CFSTARTTIME;
    time_t now = time(NULL);

    srand((unsigned) pid      * start_time ^
          (unsigned) fqdn_len * now);
    srand48((long)  pid      * start_time ^
            (long)  fqdn_len * now);

    /* 2. Seed the strong OpenSSL PRNG. */

    /* randseed file is written by cf-key. */
    char randfile[CF_BUFSIZE];
    snprintf(randfile, CF_BUFSIZE, "%s%crandseed",
             CFWORKDIR, FILE_SEPARATOR);
    Log(LOG_LEVEL_VERBOSE, "Looking for a source of entropy in '%s'",
        randfile);

    if (!RAND_load_file(randfile, -1))
    {   
        Log(LOG_LEVEL_VERBOSE,
            "Could not read sufficient randomness from '%s'", randfile);
    }   

#ifndef __MINGW32__                                     /* windows may hang */
    RAND_poll();
#else
    RAND_screen();
#endif

    /* We should have had enough entropy by now. Else we print a message and
     * use non-crypto-safe random data. */
    if (RAND_status() != 1)
    {   
        /* TODO raise to LOG_LEVEL_WARNING? */
        Log(LOG_LEVEL_INFO,
            "PRNG hasn't been seeded enough, using some pseudo-random bytes for seed!");
        Log(LOG_LEVEL_INFO,
            "A workaround is to copy 1KB of random bytes to '%s'",
            randfile);

        unsigned char rand_buf[128];
        for (size_t i = 0; i < sizeof(rand_buf); i++)
        {   
            rand_buf[i] = rand() % 256;
        }   
        RAND_seed(rand_buf, sizeof(rand_buf));

        /* If we *still* do not have enough entropy, then things will be
         * failing all over the place. Should never happen because of the
         * rand() buffer above which should be enough for all cases. */
        if (RAND_status() != 1)
        {   
            UnexpectedError("Low entropy, crypto operations will fail! "
                            "See verbose log and report which platform you are using.");
        }   
    }   
}