/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/ /*** This file is part of systemd. Copyright 2010 Lennart Poettering systemd is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 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 General Public License for more details. You should have received a copy of the GNU General Public License along with systemd; If not, see <http://www.gnu.org/licenses/>. ***/ #include <unistd.h> #include <stdio.h> #include <errno.h> #include <string.h> #include <stdlib.h> #include <fcntl.h> #include <sys/mount.h> #include "machine-id-setup.h" #include "macro.h" #include "util.h" #include "log.h" static void make_v4_uuid(unsigned char *id) { /* Stolen from generate_random_uuid() of drivers/char/random.c * in the kernel sources */ /* Set UUID version to 4 --- truly random generation */ id[6] = (id[6] & 0x0F) | 0x40; /* Set the UUID variant to DCE */ id[8] = (id[8] & 0x3F) | 0x80; } static int generate(char id[34]) { int fd; unsigned char buf[16], *p; char *q; ssize_t k; assert(id); /* First, try reading the D-Bus machine id, unless it is a symlink */ fd = open("/var/lib/dbus/machine-id", O_RDONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW); if (fd >= 0) { k = loop_read(fd, id, 33, false); close_nointr_nofail(fd); if (k >= 32) { id[32] = '\n'; id[33] = 0; log_info("Initializing machine ID from D-Bus machine ID."); return 0; } } /* If that didn't work, generate a random machine id */ fd = open("/dev/urandom", O_RDONLY|O_CLOEXEC|O_NOCTTY); if (fd < 0) { log_error("Failed to open /dev/urandom: %m"); return -errno; } k = loop_read(fd, buf, sizeof(buf), false); close_nointr_nofail(fd); if (k != sizeof(buf)) { log_error("Failed to read /dev/urandom: %s", strerror(k < 0 ? -k : EIO)); return k < 0 ? (int) k : -EIO; } /* 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.*/ make_v4_uuid(buf); for (p = buf, q = id; p < buf + sizeof(buf); p++, q += 2) { q[0] = hexchar(*p >> 4); q[1] = hexchar(*p & 15); } id[32] = '\n'; id[33] = 0; log_info("Initializing machine ID from random generator."); return 0; } int machine_id_setup(void) { int fd, r; bool writable; struct stat st; char id[34]; /* 32 + \n + \0 */ mode_t m; m = umask(0000); /* We create this 0444, to indicate that this isn't really * something you should ever modify. Of course, since the file * will be owned by root it doesn't matter much, but maybe * people look. */ fd = open("/etc/machine-id", O_RDWR|O_CREAT|O_CLOEXEC|O_NOCTTY, 0444); if (fd >= 0) writable = true; else { fd = open("/etc/machine-id", O_RDONLY|O_CLOEXEC|O_NOCTTY); if (fd < 0) { umask(m); log_error("Cannot open /etc/machine-id: %m"); return -errno; } writable = false; } umask(m); if (fstat(fd, &st) < 0) { log_error("fstat() failed: %m"); r = -errno; goto finish; } if (S_ISREG(st.st_mode)) { if (loop_read(fd, id, 32, false) >= 32) { r = 0; goto finish; } } /* Hmm, so, the id currently stored is not useful, then let's * generate one */ r = generate(id); if (r < 0) goto finish; if (S_ISREG(st.st_mode) && writable) { lseek(fd, 0, SEEK_SET); if (loop_write(fd, id, 33, false) == 33) { r = 0; goto finish; } } close_nointr_nofail(fd); fd = -1; /* Hmm, we couldn't write it? So let's write it to * /run/systemd/machine-id as a replacement */ mkdir_p("/run/systemd", 0755); m = umask(0022); r = write_one_line_file("/run/systemd/machine-id", id); umask(m); if (r < 0) { log_error("Cannot write /run/systemd/machine-id: %s", strerror(-r)); unlink("/run/systemd/machine-id"); goto finish; } /* And now, let's mount it over */ r = mount("/run/systemd/machine-id", "/etc/machine-id", "bind", MS_BIND|MS_RDONLY, NULL) < 0 ? -errno : 0; unlink("/run/systemd/machine-id"); if (r < 0) log_error("Failed to mount /etc/machine-id: %s", strerror(-r)); else log_info("Installed transient /etc/machine-id file."); finish: if (fd >= 0) close_nointr_nofail(fd); return r; }