Merge pull request #3777 from poettering/id128-rework

uuid/id128 code rework

3 files changed, 65 insertions, 169 deletions

diff --git a/src/core/machine-id-setup.c b/src/core/machine-id-setup.c
index ea6b085e4f..76dfcfa6d7 100644
--- a/src/core/machine-id-setup.c
+++ b/src/core/machine-id-setup.c
@@ -17,11 +17,8 @@
   along with systemd; If not, see <http://www.gnu.org/licenses/>.
 ***/
 
-#include <errno.h>
 #include <fcntl.h>
 #include <sched.h>
-#include <stdio.h>
-#include <string.h>
 #include <sys/mount.h>
 #include <unistd.h>
 
@@ -29,10 +26,8 @@
 
 #include "alloc-util.h"
 #include "fd-util.h"
-#include "fileio.h"
 #include "fs-util.h"
-#include "hexdecoct.h"
-#include "io-util.h"
+#include "id128-util.h"
 #include "log.h"
 #include "machine-id-setup.h"
 #include "macro.h"
@@ -46,101 +41,23 @@
 #include "util.h"
 #include "virt.h"
 
-static int shorten_uuid(char destination[34], const char source[36]) {
-        unsigned i, j;
-
-        assert(destination);
-        assert(source);
-
-        /* Converts a UUID into a machine ID, by lowercasing it and
-         * removing dashes. Validates everything. */
-
-        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)
-                return -EINVAL;
-
-        destination[32] = '\n';
-        destination[33] = 0;
-        return 0;
-}
-
-static int read_machine_id(int fd, char id[34]) {
-        char id_to_validate[34];
-        int r;
-
-        assert(fd >= 0);
-        assert(id);
-
-        /* Reads a machine ID from a file, validates it, and returns
-         * it. The returned ID ends in a newline. */
-
-        r = loop_read_exact(fd, id_to_validate, 33, false);
-        if (r < 0)
-                return r;
-
-        if (id_to_validate[32] != '\n')
-                return -EINVAL;
-
-        id_to_validate[32] = 0;
-
-        if (!id128_is_valid(id_to_validate))
-                return -EINVAL;
-
-        memcpy(id, id_to_validate, 32);
-        id[32] = '\n';
-        id[33] = 0;
-        return 0;
-}
-
-static int write_machine_id(int fd, const char id[34]) {
-        int r;
-
-        assert(fd >= 0);
-        assert(id);
-
-        if (lseek(fd, 0, SEEK_SET) < 0)
-                return -errno;
-
-        r = loop_write(fd, id, 33, false);
-        if (r < 0)
-                return r;
-
-        if (fsync(fd) < 0)
-                return -errno;
-
-        return 0;
-}
-
-static int generate_machine_id(char id[34], const char *root) {
-        int fd, r;
-        unsigned char *p;
-        sd_id128_t buf;
-        char  *q;
+static int generate_machine_id(const char *root, sd_id128_t *ret) {
         const char *dbus_machine_id;
+        _cleanup_close_ int fd = -1;
+        int r;
 
-        assert(id);
-
-        dbus_machine_id = prefix_roota(root, "/var/lib/dbus/machine-id");
+        assert(ret);
 
         /* First, try reading the D-Bus machine id, unless it is a symlink */
+        dbus_machine_id = prefix_roota(root, "/var/lib/dbus/machine-id");
         fd = open(dbus_machine_id, O_RDONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW);
         if (fd >= 0) {
-                r = read_machine_id(fd, id);
-                safe_close(fd);
-
-                if (r >= 0) {
+                if (id128_read_fd(fd, ID128_PLAIN, ret) >= 0) {
                         log_info("Initializing machine ID from D-Bus machine ID.");
                         return 0;
                 }
+
+                fd = safe_close(fd);
         }
 
         if (isempty(root)) {
@@ -151,13 +68,10 @@ static int generate_machine_id(char id[34], const char *root) {
                 if (detect_container() > 0) {
                         _cleanup_free_ char *e = NULL;
 
-                        r = getenv_for_pid(1, "container_uuid", &e);
-                        if (r > 0) {
-                                r = shorten_uuid(id, e);
-                                if (r >= 0) {
-                                        log_info("Initializing machine ID from container UUID.");
-                                        return 0;
-                                }
+                        if (getenv_for_pid(1, "container_uuid", &e) > 0 &&
+                            sd_id128_from_string(e, ret) >= 0) {
+                                log_info("Initializing machine ID from container UUID.");
+                                return 0;
                         }
 
                 } else if (detect_vm() == VIRTUALIZATION_KVM) {
@@ -166,51 +80,29 @@ static int generate_machine_id(char id[34], const char *root) {
                          * running in qemu/kvm and a machine ID was passed in
                          * via -uuid on the qemu/kvm command line */
 
-                        char uuid[36];
-
-                        fd = open("/sys/class/dmi/id/product_uuid", O_RDONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW);
-                        if (fd >= 0) {
-                                r = loop_read_exact(fd, uuid, 36, false);
-                                safe_close(fd);
-
-                                if (r >= 0) {
-                                        r = shorten_uuid(id, uuid);
-                                        if (r >= 0) {
-                                                log_info("Initializing machine ID from KVM UUID.");
-                                                return 0;
-                                        }
-                                }
+                        if (id128_read("/sys/class/dmi/id/product_uuid", ID128_UUID, ret) >= 0) {
+                                log_info("Initializing machine ID from KVM UUID.");
+                                return 0;
                         }
                 }
         }
 
         /* If that didn't work, generate a random machine id */
-        r = sd_id128_randomize(&buf);
+        r = sd_id128_randomize(ret);
         if (r < 0)
-                return log_error_errno(r, "Failed to open /dev/urandom: %m");
-
-        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;
+                return log_error_errno(r, "Failed to generate randomized : %m");
 
         log_info("Initializing machine ID from random generator.");
-
         return 0;
 }
 
-int machine_id_setup(const char *root, sd_id128_t machine_id) {
+int machine_id_setup(const char *root, sd_id128_t machine_id, sd_id128_t *ret) {
         const char *etc_machine_id, *run_machine_id;
         _cleanup_close_ int fd = -1;
-        bool writable = true;
-        char id[34]; /* 32 + \n + \0 */
+        bool writable;
         int r;
 
         etc_machine_id = prefix_roota(root, "/etc/machine-id");
-        run_machine_id = prefix_roota(root, "/run/machine-id");
 
         RUN_WITH_UMASK(0000) {
                 /* We create this 0444, to indicate that this isn't really
@@ -218,7 +110,7 @@ int machine_id_setup(const char *root, sd_id128_t machine_id) {
                  * will be owned by root it doesn't matter much, but maybe
                  * people look. */
 
-                mkdir_parents(etc_machine_id, 0755);
+                (void) mkdir_parents(etc_machine_id, 0755);
                 fd = open(etc_machine_id, O_RDWR|O_CREAT|O_CLOEXEC|O_NOCTTY, 0444);
                 if (fd < 0) {
                         int old_errno = errno;
@@ -239,41 +131,41 @@ int machine_id_setup(const char *root, sd_id128_t machine_id) {
                         }
 
                         writable = false;
-                }
+                } else
+                        writable = true;
         }
 
-        /* A machine id argument overrides all other machined-ids */
-        if (!sd_id128_is_null(machine_id)) {
-                sd_id128_to_string(machine_id, id);
-                id[32] = '\n';
-                id[33] = 0;
-        } else {
-                if (read_machine_id(fd, id) >= 0)
-                        return 0;
+        /* A we got a valid machine ID argument, that's what counts */
+        if (sd_id128_is_null(machine_id)) {
 
-                /* Hmm, so, the id currently stored is not useful, then let's
-                 * generate one */
+                /* Try to read any existing machine ID */
+                if (id128_read_fd(fd, ID128_PLAIN, ret) >= 0)
+                        return 0;
 
-                r = generate_machine_id(id, root);
+                /* Hmm, so, the id currently stored is not useful, then let's generate one */
+                r = generate_machine_id(root, &machine_id);
                 if (r < 0)
                         return r;
+
+                if (lseek(fd, 0, SEEK_SET) == (off_t) -1)
+                        return log_error_errno(errno, "Failed to seek: %m");
         }
 
         if (writable)
-                if (write_machine_id(fd, id) >= 0)
-                        return 0;
+                if (id128_write_fd(fd, ID128_PLAIN, machine_id, true) >= 0)
+                        goto finish;
 
         fd = safe_close(fd);
 
-        /* Hmm, we couldn't write it? So let's write it to
-         * /run/machine-id as a replacement */
+        /* Hmm, we couldn't write it? So let's write it to /run/machine-id as a replacement */
 
-        RUN_WITH_UMASK(0022) {
-                r = write_string_file(run_machine_id, id, WRITE_STRING_FILE_CREATE);
-                if (r < 0) {
-                        (void) unlink(run_machine_id);
-                        return log_error_errno(r, "Cannot write %s: %m", run_machine_id);
-                }
+        run_machine_id = prefix_roota(root, "/run/machine-id");
+
+        RUN_WITH_UMASK(0022)
+                r = id128_write(run_machine_id, ID128_PLAIN, machine_id, false);
+        if (r < 0) {
+                (void) unlink(run_machine_id);
+                return log_error_errno(r, "Cannot write %s: %m", run_machine_id);
         }
 
         /* And now, let's mount it over */
@@ -286,7 +178,11 @@ int machine_id_setup(const char *root, sd_id128_t machine_id) {
 
         /* Mark the mount read-only */
         if (mount(NULL, etc_machine_id, NULL, MS_BIND|MS_RDONLY|MS_REMOUNT, NULL) < 0)
-                log_warning_errno(errno, "Failed to make transient %s read-only: %m", etc_machine_id);
+                log_warning_errno(errno, "Failed to make transient %s read-only, ignoring: %m", etc_machine_id);
+
+finish:
+        if (ret)
+                *ret = machine_id;
 
         return 0;
 }
@@ -294,9 +190,13 @@ int machine_id_setup(const char *root, sd_id128_t machine_id) {
 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 */
+        sd_id128_t id;
         int r;
 
+        /* Replaces a tmpfs bind mount of /etc/machine-id by a proper file, atomically. For this, the umount is removed
+         * in a mount namespace, a new file is created at the right place. Afterwards the mount is also removed in the
+         * original mount namespace, thus revealing the file that was just created. */
+
         etc_machine_id = prefix_roota(root, "/etc/machine-id");
 
         r = path_is_mount_point(etc_machine_id, 0);
@@ -312,10 +212,6 @@ int machine_id_commit(const char *root) {
         if (fd < 0)
                 return log_error_errno(errno, "Cannot open %s: %m", etc_machine_id);
 
-        r = read_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 = fd_is_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);
@@ -324,6 +220,10 @@ int machine_id_commit(const char *root) {
                 return -EROFS;
         }
 
+        r = id128_read_fd(fd, ID128_PLAIN, &id);
+        if (r < 0)
+                return log_error_errno(r, "We didn't find a valid machine ID in %s.", etc_machine_id);
+
         fd = safe_close(fd);
 
         /* Store current mount namespace */
@@ -342,15 +242,9 @@ int machine_id_commit(const char *root) {
                 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);
+        r = id128_write(etc_machine_id, ID128_PLAIN, id, true);
         if (r < 0)
-                return log_error_errno(r, "Cannot write %s: %m", etc_machine_id);
-
-        fd = safe_close(fd);
+                return log_error_errno(r, "Cannot write %s. This is mandatory to get a persistent machine ID: %m", etc_machine_id);
 
         /* Return to initial namespace and proceed a lazy tmpfs unmount */
         r = namespace_enter(-1, initial_mntns_fd, -1, -1, -1);
diff --git a/src/core/machine-id-setup.h b/src/core/machine-id-setup.h
index a7e7678ed9..29f4620646 100644
--- a/src/core/machine-id-setup.h
+++ b/src/core/machine-id-setup.h
@@ -20,4 +20,4 @@
 ***/
 
 int machine_id_commit(const char *root);
-int machine_id_setup(const char *root, sd_id128_t machine_id);
+int machine_id_setup(const char *root, sd_id128_t requested, sd_id128_t *ret);
diff --git a/src/core/main.c b/src/core/main.c
index c59228ad53..f2adca7d2b 100644
--- a/src/core/main.c
+++ b/src/core/main.c
@@ -291,14 +291,16 @@ static int parse_crash_chvt(const char *value) {
 }
 
 static int set_machine_id(const char *m) {
+        sd_id128_t t;
         assert(m);
 
-        if (sd_id128_from_string(m, &arg_machine_id) < 0)
+        if (sd_id128_from_string(m, &t) < 0)
                 return -EINVAL;
 
-        if (sd_id128_is_null(arg_machine_id))
+        if (sd_id128_is_null(t))
                 return -EINVAL;
 
+        arg_machine_id = t;
         return 0;
 }
 
@@ -1721,7 +1723,7 @@ int main(int argc, char *argv[]) {
                         status_welcome();
 
                 hostname_setup();
-                machine_id_setup(NULL, arg_machine_id);
+                machine_id_setup(NULL, arg_machine_id, NULL);
                 loopback_setup();
                 bump_unix_max_dgram_qlen();