src/libsystemd/sd-id128/sd-id128.c

/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/

/***
  This file is part of systemd.

  Copyright 2011 Lennart Poettering

  systemd is free software; you can redistribute it and/or modify it
  under the terms of the GNU Lesser General Public License as published by
  the Free Software Foundation; either version 2.1 of the License, or
  (at your option) any later version.

  systemd 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
  Lesser General Public License for more details.

  You should have received a copy of the GNU Lesser General Public License
  along with systemd; If not, see <http://www.gnu.org/licenses/>.
***/

#include <errno.h>
#include <fcntl.h>
#include <unistd.h>

#include "util.h"
#include "macro.h"
#include "sd-id128.h"
#include "random-util.h"

_public_ char *sd_id128_to_string(sd_id128_t id, char s[33]) {
        unsigned n;

        assert_return(s, NULL);

        for (n = 0; n < 16; n++) {
                s[n*2] = hexchar(id.bytes[n] >> 4);
                s[n*2+1] = hexchar(id.bytes[n] & 0xF);
        }

        s[32] = 0;

        return s;
}

_public_ int sd_id128_from_string(const char s[], sd_id128_t *ret) {
        unsigned n, i;
        sd_id128_t t;
        bool is_guid = false;

        assert_return(s, -EINVAL);
        assert_return(ret, -EINVAL);

        for (n = 0, i = 0; n < 16;) {
                int a, b;

                if (s[i] == '-') {
                        /* Is this a GUID? Then be nice, and skip over
                         * the dashes */

                        if (i == 8)
                                is_guid = true;
                        else if (i == 13 || i == 18 || i == 23) {
                                if (!is_guid)
                                        return -EINVAL;
                        } else
                                return -EINVAL;

                        i++;
                        continue;
                }

                a = unhexchar(s[i++]);
                if (a < 0)
                        return -EINVAL;

                b = unhexchar(s[i++]);
                if (b < 0)
                        return -EINVAL;

                t.bytes[n++] = (a << 4) | b;
        }

        if (i != (is_guid ? 36 : 32))
                return -EINVAL;

        if (s[i] != 0)
                return -EINVAL;

        *ret = t;
        return 0;
}

static sd_id128_t make_v4_uuid(sd_id128_t id) {
        /* Stolen from generate_random_uuid() of drivers/char/random.c
         * in the kernel sources */

        /* Set UUID version to 4 --- truly random generation */
        id.bytes[6] = (id.bytes[6] & 0x0F) | 0x40;

        /* Set the UUID variant to DCE */
        id.bytes[8] = (id.bytes[8] & 0x3F) | 0x80;

        return id;
}

_public_ int sd_id128_get_machine(sd_id128_t *ret) {
        static thread_local sd_id128_t saved_machine_id;
        static thread_local bool saved_machine_id_valid = false;
        _cleanup_close_ int fd = -1;
        char buf[33];
        unsigned j;
        sd_id128_t t;
        int r;

        assert_return(ret, -EINVAL);

        if (saved_machine_id_valid) {
                *ret = saved_machine_id;
                return 0;
        }

        fd = open("/etc/machine-id", O_RDONLY|O_CLOEXEC|O_NOCTTY);
        if (fd < 0)
                return -errno;

        r = loop_read_exact(fd, buf, 33, false);
        if (r < 0)
                return r;
        if (buf[32] !='\n')
                return -EIO;

        for (j = 0; j < 16; j++) {
                int a, b;

                a = unhexchar(buf[j*2]);
                b = unhexchar(buf[j*2+1]);

                if (a < 0 || b < 0)
                        return -EIO;

                t.bytes[j] = a << 4 | b;
        }

        saved_machine_id = t;
        saved_machine_id_valid = true;

        *ret = t;
        return 0;
}

_public_ int sd_id128_get_boot(sd_id128_t *ret) {
        static thread_local sd_id128_t saved_boot_id;
        static thread_local bool saved_boot_id_valid = false;
        _cleanup_close_ int fd = -1;
        char buf[36];
        unsigned j;
        sd_id128_t t;
        char *p;
        int r;

        assert_return(ret, -EINVAL);

        if (saved_boot_id_valid) {
                *ret = saved_boot_id;
                return 0;
        }

        fd = open("/proc/sys/kernel/random/boot_id", O_RDONLY|O_CLOEXEC|O_NOCTTY);
        if (fd < 0)
                return -errno;

        r = loop_read_exact(fd, buf, 36, false);
        if (r < 0)
                return r;

        for (j = 0, p = buf; j < 16; j++) {
                int a, b;

                if (p >= buf + 35)
                        return -EIO;

                if (*p == '-') {
                        p++;
                        if (p >= buf + 35)
                                return -EIO;
                }

                a = unhexchar(p[0]);
                b = unhexchar(p[1]);

                if (a < 0 || b < 0)
                        return -EIO;

                t.bytes[j] = a << 4 | b;

                p += 2;
        }

        saved_boot_id = t;
        saved_boot_id_valid = true;

        *ret = t;
        return 0;
}

_public_ int sd_id128_randomize(sd_id128_t *ret) {
        sd_id128_t t;
        int r;

        assert_return(ret, -EINVAL);

        r = dev_urandom(&t, sizeof(t));
        if (r < 0)
                return r;

        /* Turn this into a valid v4 UUID, to be nice. Note that we
         * only guarantee this for newly generated UUIDs, not for
         * pre-existing ones. */

        *ret = make_v4_uuid(t);
        return 0;
}