src/lib/randgen.c

	randgen.c revision 19a02b635e2c5e796cdaecbef49a16eaec19c479
/* Copyright (c) 2002-2016 Dovecot authors, see the included COPYING file */

#include "lib.h"
#include "randgen.h"
#include "fd-close-on-exec.h"
#include <unistd.h>
#include <fcntl.h>

static int init_refcount = 0;
static int urandom_fd;

void random_fill(void *buf, size_t size)
{
    size_t pos;
    ssize_t ret;

    i_assert(init_refcount > 0);
    i_assert(size < SSIZE_T_MAX);

    for (pos = 0; pos < size; ) {
        ret = read(urandom_fd, (char *) buf + pos, size - pos);
        if (unlikely(ret <= 0)) {
            if (ret == 0)
                i_fatal("EOF when reading from "DEV_URANDOM_PATH);
            else if (errno != EINTR)
                i_fatal("read("DEV_URANDOM_PATH") failed: %m");
        } else {
            pos += ret;
        }
    }
}

void random_init(void)
{
    unsigned int seed;

    if (init_refcount++ > 0)
        return;

    urandom_fd = open(DEV_URANDOM_PATH, O_RDONLY);
    if (urandom_fd == -1) {
        if (errno == ENOENT) {
            i_fatal(DEV_URANDOM_PATH" doesn't exist, "
                "currently we require it");
        } else {
            i_fatal("Can't open "DEV_URANDOM_PATH": %m");
        }
    }

    random_fill(&seed, sizeof(seed));
    rand_set_seed(seed);

    fd_close_on_exec(urandom_fd, TRUE);
}

void random_deinit(void)
{
    if (--init_refcount > 0)
        return;

    i_close_fd(&urandom_fd);
}

#ifdef HAVE_ARC4RANDOM
#ifdef HAVE_LIBBSD
#include <bsd/stdlib.h>
#endif

void random_fill_weak(void *buf, size_t size)
{
    arc4random_buf(buf, size);
}

#else

void random_fill_weak(void *buf, size_t size)
{
    unsigned char *cbuf = buf;

    for (; size > 0; size--)
        *cbuf++ = (unsigned char)rand();
}

#endif