/*-*- 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 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 <unistd.h> #include <stdio.h> #include <errno.h> #include <string.h> #include <stdlib.h> #include <fcntl.h> #include <sys/mount.h> #include <systemd/sd-id128.h> #include "machine-id-setup.h" #include "macro.h" #include "util.h" #include "mkdir.h" #include "log.h" #include "virt.h" #include "fileio.h" static int shorten_uuid(char destination[36], const char *source) { unsigned i, j; for (i = 0, j = 0; i < 36 && j < 32; i++) { int t; t = unhexchar(source[i]); if (t < 0) continue; destination[j++] = hexchar(t); } if (i == 36 && j == 32) { destination[32] = '\n'; destination[33] = 0; return 0; } return -EINVAL; } static int generate(char id[34]) { int fd, r; unsigned char *p; sd_id128_t buf; char *q; ssize_t k; const char *vm_id; 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, 32, 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, see if we are running in qemu/kvm and a * machine ID was passed in via -uuid on the qemu/kvm command * line */ r = detect_vm(&vm_id); if (r > 0 && streq(vm_id, "kvm")) { char uuid[37]; fd = open("/sys/class/dmi/id/product_uuid", O_RDONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW); if (fd >= 0) { k = loop_read(fd, uuid, 36, false); close_nointr_nofail(fd); if (k >= 36) { r = shorten_uuid(id, uuid); if (r >= 0) { log_info("Initializing machine ID from KVM UUID."); return 0; } } } } /* If that didn't work either, see if we are running in a * container, and a machine ID was passed in via * $container_uuid the way libvirt/LXC does it */ r = detect_container(NULL); if (r > 0) { char *e; r = getenv_for_pid(1, "container_uuid", &e); if (r > 0) { if (strlen(e) >= 36) { r = shorten_uuid(id, e); if (r >= 0) { log_info("Initializing machine ID from container UUID."); free(e); return 0; } } free(e); } } /* If that didn't work, generate a random machine id */ r = sd_id128_randomize(&buf); if (r < 0) { log_error("Failed to open /dev/urandom: %s", strerror(-r)); return r; } for (p = buf.bytes, q = id; p < buf.bytes + 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/machine-id as a replacement */ m = umask(0022); r = write_one_line_file("/run/machine-id", id); umask(m); if (r < 0) { log_error("Cannot write /run/machine-id: %s", strerror(-r)); unlink("/run/machine-id"); goto finish; } /* And now, let's mount it over */ r = mount("/run/machine-id", "/etc/machine-id", NULL, MS_BIND, NULL) < 0 ? -errno : 0; if (r < 0) { unlink("/run/machine-id"); log_error("Failed to mount /etc/machine-id: %s", strerror(-r)); } else { log_info("Installed transient /etc/machine-id file."); /* Mark the mount read-only */ mount(NULL, "/etc/machine-id", NULL, MS_BIND|MS_RDONLY|MS_REMOUNT, NULL); } finish: if (fd >= 0) close_nointr_nofail(fd); return r; }