X-Git-Url: https://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?a=blobdiff_plain;f=src%2Fcore%2Fmachine-id-setup.c;h=74582a5dcd0be2121778197e6301bc0f922fc4b7;hb=652212b0c2b60b9ef9b2e24eae82401f880fa21a;hp=671003820b77b2a815ddbf37a8b60be1ec096196;hpb=4a62c710b62a5a3c7a8a278b810b9d5b5a0c8f4f;p=elogind.git diff --git a/src/core/machine-id-setup.c b/src/core/machine-id-setup.c index 671003820..74582a5dc 100644 --- a/src/core/machine-id-setup.c +++ b/src/core/machine-id-setup.c @@ -157,6 +157,116 @@ static int generate(char id[34], const char *root) { return 0; } +static int get_valid_machine_id(int fd, char id[34]) { + char id_to_validate[34]; + + assert(fd >= 0); + assert(id); + + if (loop_read(fd, id_to_validate, 33, false) == 33 && id_to_validate[32] == '\n') { + id_to_validate[32] = 0; + + if (id128_is_valid(id_to_validate)) { + memcpy(id, id_to_validate, 32); + id[32] = '\n'; + id[33] = 0; + return 0; + } + } + + return -EINVAL; +} + +static int write_machine_id(int fd, char id[34]) { + assert(fd >= 0); + assert(id); + lseek(fd, 0, SEEK_SET); + + if (loop_write(fd, id, 33, false) == 33) + return 0; + + return -errno; +} + +int machine_id_commit(const char *root) { + _cleanup_close_ int fd = -1, initial_mntns_fd = -1; + const char *etc_machine_id; + char id[34]; /* 32 + \n + \0 */ + int r; + + if (isempty(root)) + etc_machine_id = "/etc/machine-id"; + else { + char *x; + + x = strappenda(root, "/etc/machine-id"); + etc_machine_id = path_kill_slashes(x); + } + + r = path_is_mount_point(etc_machine_id, false); + if (r < 0) + return log_error_errno(r, "Failed to determine wether %s is a mount point: %m", etc_machine_id); + if (r == 0) { + log_debug("%s is is not a mount point. Nothing to do.", etc_machine_id); + return 0; + } + + /* Read existing machine-id */ + fd = open(etc_machine_id, O_RDONLY|O_CLOEXEC|O_NOCTTY); + if (fd < 0) + return log_error_errno(errno, "Cannot open %s: %m", etc_machine_id); + + r = get_valid_machine_id(fd, id); + if (r < 0) + return log_error_errno(r, "We didn't find a valid machine ID in %s.", etc_machine_id); + + r = is_fd_on_temporary_fs(fd); + if (r < 0) + return log_error_errno(r, "Failed to determine whether %s is on a temporary file system: %m", etc_machine_id); + if (r == 0) { + log_error("%s is not on a temporary file system.", etc_machine_id); + return -EROFS; + } + + fd = safe_close(fd); + + /* Store current mount namespace */ + r = namespace_open(0, NULL, &initial_mntns_fd, NULL, NULL); + if (r < 0) + return log_error_errno(r, "Can't fetch current mount namespace: %m"); + + /* Switch to a new mount namespace, isolate ourself and unmount etc_machine_id in our new namespace */ + if (unshare(CLONE_NEWNS) < 0) + return log_error_errno(errno, "Failed to enter new namespace: %m"); + + if (mount(NULL, "/", NULL, MS_SLAVE | MS_REC, NULL) < 0) + return log_error_errno(errno, "Couldn't make-rslave / mountpoint in our private namespace: %m"); + + if (umount(etc_machine_id) < 0) + return log_error_errno(errno, "Failed to unmount transient %s file in our private namespace: %m", etc_machine_id); + + /* Update a persistent version of etc_machine_id */ + fd = open(etc_machine_id, O_RDWR|O_CREAT|O_CLOEXEC|O_NOCTTY, 0444); + if (fd < 0) + return log_error_errno(errno, "Cannot open for writing %s. This is mandatory to get a persistent machine-id: %m", etc_machine_id); + + r = write_machine_id(fd, id); + if (r < 0) + return log_error_errno(r, "Cannot write %s: %m", etc_machine_id); + + fd = safe_close(fd); + + /* Return to initial namespace and proceed a lazy tmpfs unmount */ + r = namespace_enter(-1, initial_mntns_fd, -1, -1); + if (r < 0) + return log_warning_errno(r, "Failed to switch back to initial mount namespace: %m.\nWe'll keep transient %s file until next reboot.", etc_machine_id); + + if (umount2(etc_machine_id, MNT_DETACH) < 0) + return log_warning_errno(errno, "Failed to unmount transient %s file: %m.\nWe keep that mount until next reboot.", etc_machine_id); + + return 0; +} + int machine_id_setup(const char *root) { const char *etc_machine_id, *run_machine_id; _cleanup_close_ int fd = -1; @@ -169,11 +279,13 @@ int machine_id_setup(const char *root) { etc_machine_id = "/etc/machine-id"; run_machine_id = "/run/machine-id"; } else { - etc_machine_id = strappenda(root, "/etc/machine-id"); - path_kill_slashes((char*) etc_machine_id); + char *x; - run_machine_id = strappenda(root, "/run/machine-id"); - path_kill_slashes((char*) run_machine_id); + x = strappenda(root, "/etc/machine-id"); + etc_machine_id = path_kill_slashes(x); + + x = strappenda(root, "/run/machine-id"); + run_machine_id = path_kill_slashes(x); } RUN_WITH_UMASK(0000) { @@ -207,13 +319,8 @@ int machine_id_setup(const char *root) { if (fstat(fd, &st) < 0) return log_error_errno(errno, "fstat() failed: %m"); - if (S_ISREG(st.st_mode)) - if (loop_read(fd, id, 33, false) == 33 && id[32] == '\n') { - id[32] = 0; - - if (id128_is_valid(id)) - return 0; - } + if (S_ISREG(st.st_mode) && get_valid_machine_id(fd, id) == 0) + return 0; /* Hmm, so, the id currently stored is not useful, then let's * generate one */ @@ -223,9 +330,7 @@ int machine_id_setup(const char *root) { return r; if (S_ISREG(st.st_mode) && writable) { - lseek(fd, 0, SEEK_SET); - - if (loop_write(fd, id, 33, false) == 33) + if (write_machine_id(fd, id) == 0) return 0; }