cjdns/crypto/random/seed/LinuxRandomUuidSysctlRandomSeed.c

/* vim: set expandtab ts=4 sw=4: */
/*
 * You may redistribute this program and/or modify it under the terms of
 * the GNU General Public License as published by the Free Software Foundation,
 * either version 3 of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */
#define _GNU_SOURCE
#include "crypto/random/seed/LinuxRandomUuidSysctlRandomSeed.h"
#include "util/Identity.h"
#include "util/Bits.h"
#include "util/Hex.h"

#include <unistd.h>
#include <sys/syscall.h>
#ifndef SYS_getrandom
#include <sys/sysctl.h>

static int getUUID(uint64_t output[2])
{
    int mib[] = { CTL_KERN, KERN_RANDOM, RANDOM_UUID };
    size_t sixteen = 16;

    Bits_memset(output, 0, 16);
    if (sysctl(mib, 3, output, &sixteen, NULL, 0)
        || Bits_isZero(output, 16))
    {
        return -1;
    }
    return 0;
}
#endif

static int get(RandomSeed_t* randomSeed, uint64_t output[8])
{

#ifdef SYS_getrandom
    // Try using getrandom instead sysctl as with systems with getrandom
    // sysctl is probably alrady deprecated and possibly disabled.
    Bits_memset(output, 0, 64); // Just make sure that it is zero all along.

    long ret = syscall(SYS_getrandom, output, 64, 0);
    if (ret == 64 && !Bits_isZero(output, 64)) {
        return 0;
    }
    return -1;
#else
    if (getUUID(output) || getUUID(output+2) || getUUID(output+4) || getUUID(output+6)) {
        return -1;
    }
    return 0;
#endif
}

RandomSeed_t* LinuxRandomUuidSysctlRandomSeed_new(struct Allocator* alloc)
{
    return Allocator_clone(alloc, (&(RandomSeed_t) {
        .get = get,
        .name = "sysctl(RANDOM_UUID) (Linux)"
    }));
}