machine-id-setup: don't try to read UUID from VM/container manager if we operate on a root directory that's not /

This should make sure no UUID from the host systemd-machine-id-setup is
running on leaks onto a disk image that is provisioned with the tool.

1 files changed, 41 insertions, 38 deletions

diff --git a/src/core/machine-id-setup.c b/src/core/machine-id-setup.c
index 712f60cb11..efb074fcbd 100644
--- a/src/core/machine-id-setup.c
+++ b/src/core/machine-id-setup.c
@@ -64,15 +64,16 @@ static int generate(char id[34], const char *root) {
         int fd, r;
         unsigned char *p;
         sd_id128_t buf;
-        char *q;
+        char  *q;
         ssize_t k;
-        const char *vm_id;
-        _cleanup_free_ char *dbus_machine_id = NULL;
+        const char *vm_id, *dbus_machine_id;
 
         assert(id);
 
-        if (asprintf(&dbus_machine_id, "%s/var/lib/dbus/machine-id", root) < 0)
-                return log_oom();
+        if (isempty(root))
+                dbus_machine_id = "/var/lib/dbus/machine-id";
+        else
+                dbus_machine_id = strappenda(root, "/var/lib/dbus/machine-id");
 
         /* First, try reading the D-Bus machine id, unless it is a symlink */
         fd = open(dbus_machine_id, O_RDONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW);
@@ -93,46 +94,48 @@ static int generate(char id[34], const char *root) {
                 }
         }
 
-        /* If that didn't work, 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) {
-                _cleanup_free_ char *e = NULL;
-
-                r = getenv_for_pid(1, "container_uuid", &e);
+        if (isempty(root)) {
+                /* If that didn't work, 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) {
-                        if (strlen(e) >= 36) {
-                                r = shorten_uuid(id, e);
-                                if (r >= 0) {
-                                        log_info("Initializing machine ID from container UUID.");
-                                        return 0;
-                                }
-                        }
-                }
-
-        } else {
-                /* If we are not running in a container, see if we are
-                 * running in qemu/kvm and a machine ID was passed in
-                 * via -uuid on the qemu/kvm command line */
+                        _cleanup_free_ char *e = NULL;
 
-                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);
-                                safe_close(fd);
-
-                                if (k >= 36) {
-                                        r = shorten_uuid(id, uuid);
+                        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 KVM UUID.");
+                                                log_info("Initializing machine ID from container UUID.");
                                                 return 0;
                                         }
                                 }
                         }
+
+                } else {
+                        /* If we are not running in a container, 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);
+                                        safe_close(fd);
+
+                                        if (k >= 36) {
+                                                r = shorten_uuid(id, uuid);
+                                                if (r >= 0) {
+                                                        log_info("Initializing machine ID from KVM UUID.");
+                                                        return 0;
+                                                }
+                                        }
+                                }
+                        }
                 }
         }