diff options
Diffstat (limited to 'src/core/dynamic-user.c')
| -rw-r--r-- | src/core/dynamic-user.c | 826 |
1 files changed, 826 insertions, 0 deletions
diff --git a/src/core/dynamic-user.c b/src/core/dynamic-user.c new file mode 100644 index 0000000..18b36e7 --- /dev/null +++ b/src/core/dynamic-user.c @@ -0,0 +1,826 @@ +/* SPDX-License-Identifier: LGPL-2.1-or-later */ + +#include <sys/file.h> +#include <sys/stat.h> +#include <sys/types.h> + +#include "clean-ipc.h" +#include "dynamic-user.h" +#include "fd-util.h" +#include "fileio.h" +#include "format-util.h" +#include "fs-util.h" +#include "io-util.h" +#include "nscd-flush.h" +#include "parse-util.h" +#include "random-util.h" +#include "serialize.h" +#include "socket-util.h" +#include "stdio-util.h" +#include "string-util.h" +#include "strv.h" +#include "uid-alloc-range.h" +#include "user-util.h" + +/* Takes a value generated randomly or by hashing and turns it into a UID in the right range */ +#define UID_CLAMP_INTO_RANGE(rnd) (((uid_t) (rnd) % (DYNAMIC_UID_MAX - DYNAMIC_UID_MIN + 1)) + DYNAMIC_UID_MIN) + +DEFINE_PRIVATE_TRIVIAL_REF_FUNC(DynamicUser, dynamic_user); + +static DynamicUser* dynamic_user_free(DynamicUser *d) { + if (!d) + return NULL; + + if (d->manager) + (void) hashmap_remove(d->manager->dynamic_users, d->name); + + safe_close_pair(d->storage_socket); + return mfree(d); +} + +static int dynamic_user_add(Manager *m, const char *name, int storage_socket[static 2], DynamicUser **ret) { + DynamicUser *d; + int r; + + assert(m); + assert(name); + assert(storage_socket); + + r = hashmap_ensure_allocated(&m->dynamic_users, &string_hash_ops); + if (r < 0) + return r; + + d = malloc0(offsetof(DynamicUser, name) + strlen(name) + 1); + if (!d) + return -ENOMEM; + + strcpy(d->name, name); + + d->storage_socket[0] = storage_socket[0]; + d->storage_socket[1] = storage_socket[1]; + + r = hashmap_put(m->dynamic_users, d->name, d); + if (r < 0) { + free(d); + return r; + } + + d->manager = m; + + if (ret) + *ret = d; + + return 0; +} + +static int dynamic_user_acquire(Manager *m, const char *name, DynamicUser** ret) { + _cleanup_close_pair_ int storage_socket[2] = { -1, -1 }; + DynamicUser *d; + int r; + + assert(m); + assert(name); + + /* Return the DynamicUser structure for a specific user name. Note that this won't actually allocate a UID for + * it, but just prepare the data structure for it. The UID is allocated only on demand, when it's really + * needed, and in the child process we fork off, since allocation involves NSS checks which are not OK to do + * from PID 1. To allow the children and PID 1 share information about allocated UIDs we use an anonymous + * AF_UNIX/SOCK_DGRAM socket (called the "storage socket") that contains at most one datagram with the + * allocated UID number, plus an fd referencing the lock file for the UID + * (i.e. /run/systemd/dynamic-uid/$UID). Why involve the socket pair? So that PID 1 and all its children can + * share the same storage for the UID and lock fd, simply by inheriting the storage socket fds. The socket pair + * may exist in three different states: + * + * a) no datagram stored. This is the initial state. In this case the dynamic user was never realized. + * + * b) a datagram containing a UID stored, but no lock fd attached to it. In this case there was already a + * statically assigned UID by the same name, which we are reusing. + * + * c) a datagram containing a UID stored, and a lock fd is attached to it. In this case we allocated a dynamic + * UID and locked it in the file system, using the lock fd. + * + * As PID 1 and various children might access the socket pair simultaneously, and pop the datagram or push it + * back in any time, we also maintain a lock on the socket pair. Note one peculiarity regarding locking here: + * the UID lock on disk is protected via a BSD file lock (i.e. an fd-bound lock), so that the lock is kept in + * place as long as there's a reference to the fd open. The lock on the storage socket pair however is a POSIX + * file lock (i.e. a process-bound lock), as all users share the same fd of this (after all it is anonymous, + * nobody else could get any access to it except via our own fd) and we want to synchronize access between all + * processes that have access to it. */ + + d = hashmap_get(m->dynamic_users, name); + if (d) { + if (ret) { + /* We already have a structure for the dynamic user, let's increase the ref count and reuse it */ + d->n_ref++; + *ret = d; + } + return 0; + } + + if (!valid_user_group_name(name, VALID_USER_ALLOW_NUMERIC)) + return -EINVAL; + + if (socketpair(AF_UNIX, SOCK_DGRAM|SOCK_CLOEXEC, 0, storage_socket) < 0) + return -errno; + + r = dynamic_user_add(m, name, storage_socket, &d); + if (r < 0) + return r; + + storage_socket[0] = storage_socket[1] = -1; + + if (ret) { + d->n_ref++; + *ret = d; + } + + return 1; +} + +static int make_uid_symlinks(uid_t uid, const char *name, bool b) { + + char path1[STRLEN("/run/systemd/dynamic-uid/direct:") + DECIMAL_STR_MAX(uid_t) + 1]; + const char *path2; + int r = 0, k; + + /* Add direct additional symlinks for direct lookups of dynamic UIDs and their names by userspace code. The + * only reason we have this is because dbus-daemon cannot use D-Bus for resolving users and groups (since it + * would be its own client then). We hence keep these world-readable symlinks in place, so that the + * unprivileged dbus user can read the mappings when it needs them via these symlinks instead of having to go + * via the bus. Ideally, we'd use the lock files we keep for this anyway, but we can't since we use BSD locks + * on them and as those may be taken by any user with read access we can't make them world-readable. */ + + xsprintf(path1, "/run/systemd/dynamic-uid/direct:" UID_FMT, uid); + if (unlink(path1) < 0 && errno != ENOENT) + r = -errno; + + if (b && symlink(name, path1) < 0) { + k = log_warning_errno(errno, "Failed to symlink \"%s\": %m", path1); + if (r == 0) + r = k; + } + + path2 = strjoina("/run/systemd/dynamic-uid/direct:", name); + if (unlink(path2) < 0 && errno != ENOENT) { + k = -errno; + if (r == 0) + r = k; + } + + if (b && symlink(path1 + STRLEN("/run/systemd/dynamic-uid/direct:"), path2) < 0) { + k = log_warning_errno(errno, "Failed to symlink \"%s\": %m", path2); + if (r == 0) + r = k; + } + + return r; +} + +static int pick_uid(char **suggested_paths, const char *name, uid_t *ret_uid) { + + /* Find a suitable free UID. We use the following strategy to find a suitable UID: + * + * 1. Initially, we try to read the UID of a number of specified paths. If any of these UIDs works, we use + * them. We use in order to increase the chance of UID reuse, if StateDirectory=, CacheDirectory= or + * LogsDirectory= are used, as reusing the UID these directories are owned by saves us from having to + * recursively chown() them to new users. + * + * 2. If that didn't yield a currently unused UID, we hash the user name, and try to use that. This should be + * pretty good, as the use ris by default derived from the unit name, and hence the same service and same + * user should usually get the same UID as long as our hashing doesn't clash. + * + * 3. Finally, if that didn't work, we randomly pick UIDs, until we find one that is empty. + * + * Since the dynamic UID space is relatively small we'll stop trying after 100 iterations, giving up. */ + + enum { + PHASE_SUGGESTED, /* the first phase, reusing directory ownership UIDs */ + PHASE_HASHED, /* the second phase, deriving a UID from the username by hashing */ + PHASE_RANDOM, /* the last phase, randomly picking UIDs */ + } phase = PHASE_SUGGESTED; + + static const uint8_t hash_key[] = { + 0x37, 0x53, 0x7e, 0x31, 0xcf, 0xce, 0x48, 0xf5, + 0x8a, 0xbb, 0x39, 0x57, 0x8d, 0xd9, 0xec, 0x59 + }; + + unsigned n_tries = 100, current_suggested = 0; + int r; + + (void) mkdir("/run/systemd/dynamic-uid", 0755); + + for (;;) { + char lock_path[STRLEN("/run/systemd/dynamic-uid/") + DECIMAL_STR_MAX(uid_t) + 1]; + _cleanup_close_ int lock_fd = -1; + uid_t candidate; + ssize_t l; + + if (--n_tries <= 0) /* Give up retrying eventually */ + return -EBUSY; + + switch (phase) { + + case PHASE_SUGGESTED: { + struct stat st; + + if (!suggested_paths || !suggested_paths[current_suggested]) { + /* We reached the end of the suggested paths list, let's try by hashing the name */ + phase = PHASE_HASHED; + continue; + } + + if (stat(suggested_paths[current_suggested++], &st) < 0) + continue; /* We can't read the UID of this path, but that doesn't matter, just try the next */ + + candidate = st.st_uid; + break; + } + + case PHASE_HASHED: + /* A static user by this name does not exist yet. Let's find a free ID then, and use that. We + * start with a UID generated as hash from the user name. */ + candidate = UID_CLAMP_INTO_RANGE(siphash24(name, strlen(name), hash_key)); + + /* If this one fails, we should proceed with random tries */ + phase = PHASE_RANDOM; + break; + + case PHASE_RANDOM: + + /* Pick another random UID, and see if that works for us. */ + random_bytes(&candidate, sizeof(candidate)); + candidate = UID_CLAMP_INTO_RANGE(candidate); + break; + + default: + assert_not_reached(); + } + + /* Make sure whatever we picked here actually is in the right range */ + if (!uid_is_dynamic(candidate)) + continue; + + xsprintf(lock_path, "/run/systemd/dynamic-uid/" UID_FMT, candidate); + + for (;;) { + struct stat st; + + lock_fd = open(lock_path, O_CREAT|O_RDWR|O_NOFOLLOW|O_CLOEXEC|O_NOCTTY, 0600); + if (lock_fd < 0) + return -errno; + + r = flock(lock_fd, LOCK_EX|LOCK_NB); /* Try to get a BSD file lock on the UID lock file */ + if (r < 0) { + if (IN_SET(errno, EBUSY, EAGAIN)) + goto next; /* already in use */ + + return -errno; + } + + if (fstat(lock_fd, &st) < 0) + return -errno; + if (st.st_nlink > 0) + break; + + /* Oh, bummer, we got the lock, but the file was unlinked between the time we opened it and + * got the lock. Close it, and try again. */ + lock_fd = safe_close(lock_fd); + } + + /* Some superficial check whether this UID/GID might already be taken by some static user */ + if (getpwuid(candidate) || + getgrgid((gid_t) candidate) || + search_ipc(candidate, (gid_t) candidate) != 0) { + (void) unlink(lock_path); + continue; + } + + /* Let's store the user name in the lock file, so that we can use it for looking up the username for a UID */ + l = pwritev(lock_fd, + (struct iovec[2]) { + IOVEC_INIT_STRING(name), + IOVEC_INIT((char[1]) { '\n' }, 1), + }, 2, 0); + if (l < 0) { + r = -errno; + (void) unlink(lock_path); + return r; + } + + (void) ftruncate(lock_fd, l); + (void) make_uid_symlinks(candidate, name, true); /* also add direct lookup symlinks */ + + *ret_uid = candidate; + return TAKE_FD(lock_fd); + + next: + ; + } +} + +static int dynamic_user_pop(DynamicUser *d, uid_t *ret_uid, int *ret_lock_fd) { + uid_t uid = UID_INVALID; + struct iovec iov = IOVEC_INIT(&uid, sizeof(uid)); + int lock_fd; + ssize_t k; + + assert(d); + assert(ret_uid); + assert(ret_lock_fd); + + /* Read the UID and lock fd that is stored in the storage AF_UNIX socket. This should be called with + * the lock on the socket taken. */ + + k = receive_one_fd_iov(d->storage_socket[0], &iov, 1, MSG_DONTWAIT, &lock_fd); + if (k < 0) + return (int) k; + + *ret_uid = uid; + *ret_lock_fd = lock_fd; + + return 0; +} + +static int dynamic_user_push(DynamicUser *d, uid_t uid, int lock_fd) { + struct iovec iov = IOVEC_INIT(&uid, sizeof(uid)); + + assert(d); + + /* Store the UID and lock_fd in the storage socket. This should be called with the socket pair lock taken. */ + return send_one_fd_iov(d->storage_socket[1], lock_fd, &iov, 1, MSG_DONTWAIT); +} + +static void unlink_uid_lock(int lock_fd, uid_t uid, const char *name) { + char lock_path[STRLEN("/run/systemd/dynamic-uid/") + DECIMAL_STR_MAX(uid_t) + 1]; + + if (lock_fd < 0) + return; + + xsprintf(lock_path, "/run/systemd/dynamic-uid/" UID_FMT, uid); + (void) unlink(lock_path); + + (void) make_uid_symlinks(uid, name, false); /* remove direct lookup symlinks */ +} + +static int lockfp(int fd, int *fd_lock) { + if (lockf(fd, F_LOCK, 0) < 0) + return -errno; + *fd_lock = fd; + return 0; +} + +static void unlockfp(int *fd_lock) { + if (*fd_lock < 0) + return; + lockf(*fd_lock, F_ULOCK, 0); + *fd_lock = -1; +} + +static int dynamic_user_realize( + DynamicUser *d, + char **suggested_dirs, + uid_t *ret_uid, gid_t *ret_gid, + bool is_user) { + + _cleanup_(unlockfp) int storage_socket0_lock = -1; + _cleanup_close_ int uid_lock_fd = -1; + _cleanup_close_ int etc_passwd_lock_fd = -1; + uid_t num = UID_INVALID; /* a uid if is_user, and a gid otherwise */ + gid_t gid = GID_INVALID; /* a gid if is_user, ignored otherwise */ + bool flush_cache = false; + int r; + + assert(d); + assert(is_user == !!ret_uid); + assert(ret_gid); + + /* Acquire a UID for the user name. This will allocate a UID for the user name if the user doesn't exist + * yet. If it already exists its existing UID/GID will be reused. */ + + r = lockfp(d->storage_socket[0], &storage_socket0_lock); + if (r < 0) + return r; + + r = dynamic_user_pop(d, &num, &uid_lock_fd); + if (r < 0) { + int new_uid_lock_fd; + uid_t new_uid; + + if (r != -EAGAIN) + return r; + + /* OK, nothing stored yet, let's try to find something useful. While we are working on this release the + * lock however, so that nobody else blocks on our NSS lookups. */ + unlockfp(&storage_socket0_lock); + + /* Let's see if a proper, static user or group by this name exists. Try to take the lock on + * /etc/passwd, if that fails with EROFS then /etc is read-only. In that case it's fine if we don't + * take the lock, given that users can't be added there anyway in this case. */ + etc_passwd_lock_fd = take_etc_passwd_lock(NULL); + if (etc_passwd_lock_fd < 0 && etc_passwd_lock_fd != -EROFS) + return etc_passwd_lock_fd; + + /* First, let's parse this as numeric UID */ + r = parse_uid(d->name, &num); + if (r < 0) { + struct passwd *p; + struct group *g; + + if (is_user) { + /* OK, this is not a numeric UID. Let's see if there's a user by this name */ + p = getpwnam(d->name); + if (p) { + num = p->pw_uid; + gid = p->pw_gid; + } else { + /* if the user does not exist but the group with the same name exists, refuse operation */ + g = getgrnam(d->name); + if (g) + return -EILSEQ; + } + } else { + /* Let's see if there's a group by this name */ + g = getgrnam(d->name); + if (g) + num = (uid_t) g->gr_gid; + else { + /* if the group does not exist but the user with the same name exists, refuse operation */ + p = getpwnam(d->name); + if (p) + return -EILSEQ; + } + } + } + + if (num == UID_INVALID) { + /* No static UID assigned yet, excellent. Let's pick a new dynamic one, and lock it. */ + + uid_lock_fd = pick_uid(suggested_dirs, d->name, &num); + if (uid_lock_fd < 0) + return uid_lock_fd; + } + + /* So, we found a working UID/lock combination. Let's see if we actually still need it. */ + r = lockfp(d->storage_socket[0], &storage_socket0_lock); + if (r < 0) { + unlink_uid_lock(uid_lock_fd, num, d->name); + return r; + } + + r = dynamic_user_pop(d, &new_uid, &new_uid_lock_fd); + if (r < 0) { + if (r != -EAGAIN) { + /* OK, something bad happened, let's get rid of the bits we acquired. */ + unlink_uid_lock(uid_lock_fd, num, d->name); + return r; + } + + /* Great! Nothing is stored here, still. Store our newly acquired data. */ + flush_cache = true; + } else { + /* Hmm, so as it appears there's now something stored in the storage socket. Throw away what we + * acquired, and use what's stored now. */ + + unlink_uid_lock(uid_lock_fd, num, d->name); + safe_close(uid_lock_fd); + + num = new_uid; + uid_lock_fd = new_uid_lock_fd; + } + } else if (is_user && !uid_is_dynamic(num)) { + struct passwd *p; + + /* Statically allocated user may have different uid and gid. So, let's obtain the gid. */ + errno = 0; + p = getpwuid(num); + if (!p) + return errno_or_else(ESRCH); + + gid = p->pw_gid; + } + + /* If the UID/GID was already allocated dynamically, push the data we popped out back in. If it was already + * allocated statically, push the UID back too, but do not push the lock fd in. If we allocated the UID + * dynamically right here, push that in along with the lock fd for it. */ + r = dynamic_user_push(d, num, uid_lock_fd); + if (r < 0) + return r; + + if (flush_cache) { + /* If we allocated a new dynamic UID, refresh nscd, so that it forgets about potentially cached + * negative entries. But let's do so after we release the /etc/passwd lock, so that there's no + * potential for nscd wanting to lock that for completing the invalidation. */ + etc_passwd_lock_fd = safe_close(etc_passwd_lock_fd); + (void) nscd_flush_cache(STRV_MAKE("passwd", "group")); + } + + if (is_user) { + *ret_uid = num; + *ret_gid = gid != GID_INVALID ? gid : num; + } else + *ret_gid = num; + + return 0; +} + +int dynamic_user_current(DynamicUser *d, uid_t *ret) { + _cleanup_(unlockfp) int storage_socket0_lock = -1; + _cleanup_close_ int lock_fd = -1; + uid_t uid; + int r; + + assert(d); + + /* Get the currently assigned UID for the user, if there's any. This simply pops the data from the + * storage socket, and pushes it back in right-away. */ + + r = lockfp(d->storage_socket[0], &storage_socket0_lock); + if (r < 0) + return r; + + r = dynamic_user_pop(d, &uid, &lock_fd); + if (r < 0) + return r; + + r = dynamic_user_push(d, uid, lock_fd); + if (r < 0) + return r; + + if (ret) + *ret = uid; + + return 0; +} + +static DynamicUser* dynamic_user_unref(DynamicUser *d) { + if (!d) + return NULL; + + /* Note that this doesn't actually release any resources itself. If a dynamic user should be fully + * destroyed and its UID released, use dynamic_user_destroy() instead. NB: the dynamic user table may + * contain entries with no references, which is commonly the case right before a daemon reload. */ + + assert(d->n_ref > 0); + d->n_ref--; + + return NULL; +} + +static int dynamic_user_close(DynamicUser *d) { + _cleanup_(unlockfp) int storage_socket0_lock = -1; + _cleanup_close_ int lock_fd = -1; + uid_t uid; + int r; + + /* Release the user ID, by releasing the lock on it, and emptying the storage socket. After this the + * user is unrealized again, much like it was after it the DynamicUser object was first allocated. */ + + r = lockfp(d->storage_socket[0], &storage_socket0_lock); + if (r < 0) + return r; + + r = dynamic_user_pop(d, &uid, &lock_fd); + if (r == -EAGAIN) + /* User wasn't realized yet, nothing to do. */ + return 0; + if (r < 0) + return r; + + /* This dynamic user was realized and dynamically allocated. In this case, let's remove the lock file. */ + unlink_uid_lock(lock_fd, uid, d->name); + + (void) nscd_flush_cache(STRV_MAKE("passwd", "group")); + return 1; +} + +static DynamicUser* dynamic_user_destroy(DynamicUser *d) { + if (!d) + return NULL; + + /* Drop a reference to a DynamicUser object, and destroy the user completely if this was the last + * reference. This is called whenever a service is shut down and wants its dynamic UID gone. Note that + * dynamic_user_unref() is what is called whenever a service is simply freed, for example during a reload + * cycle, where the dynamic users should not be destroyed, but our datastructures should. */ + + dynamic_user_unref(d); + + if (d->n_ref > 0) + return NULL; + + (void) dynamic_user_close(d); + return dynamic_user_free(d); +} + +int dynamic_user_serialize(Manager *m, FILE *f, FDSet *fds) { + DynamicUser *d; + + assert(m); + assert(f); + assert(fds); + + /* Dump the dynamic user database into the manager serialization, to deal with daemon reloads. */ + + HASHMAP_FOREACH(d, m->dynamic_users) { + int copy0, copy1; + + copy0 = fdset_put_dup(fds, d->storage_socket[0]); + if (copy0 < 0) + return log_error_errno(copy0, "Failed to add dynamic user storage fd to serialization: %m"); + + copy1 = fdset_put_dup(fds, d->storage_socket[1]); + if (copy1 < 0) + return log_error_errno(copy1, "Failed to add dynamic user storage fd to serialization: %m"); + + (void) serialize_item_format(f, "dynamic-user", "%s %i %i", d->name, copy0, copy1); + } + + return 0; +} + +void dynamic_user_deserialize_one(Manager *m, const char *value, FDSet *fds) { + _cleanup_free_ char *name = NULL, *s0 = NULL, *s1 = NULL; + int r, fd0, fd1; + + assert(m); + assert(value); + assert(fds); + + /* Parse the serialization again, after a daemon reload */ + + r = extract_many_words(&value, NULL, 0, &name, &s0, &s1, NULL); + if (r != 3 || !isempty(value)) { + log_debug("Unable to parse dynamic user line."); + return; + } + + if (safe_atoi(s0, &fd0) < 0 || !fdset_contains(fds, fd0)) { + log_debug("Unable to process dynamic user fd specification."); + return; + } + + if (safe_atoi(s1, &fd1) < 0 || !fdset_contains(fds, fd1)) { + log_debug("Unable to process dynamic user fd specification."); + return; + } + + r = dynamic_user_add(m, name, (int[]) { fd0, fd1 }, NULL); + if (r < 0) { + log_debug_errno(r, "Failed to add dynamic user: %m"); + return; + } + + (void) fdset_remove(fds, fd0); + (void) fdset_remove(fds, fd1); +} + +void dynamic_user_vacuum(Manager *m, bool close_user) { + DynamicUser *d; + + assert(m); + + /* Empty the dynamic user database, optionally cleaning up orphaned dynamic users, i.e. destroy and free users + * to which no reference exist. This is called after a daemon reload finished, in order to destroy users which + * might not be referenced anymore. */ + + HASHMAP_FOREACH(d, m->dynamic_users) { + if (d->n_ref > 0) + continue; + + if (close_user) { + log_debug("Removing orphaned dynamic user %s", d->name); + (void) dynamic_user_close(d); + } + + dynamic_user_free(d); + } +} + +int dynamic_user_lookup_uid(Manager *m, uid_t uid, char **ret) { + char lock_path[STRLEN("/run/systemd/dynamic-uid/") + DECIMAL_STR_MAX(uid_t) + 1]; + _cleanup_free_ char *user = NULL; + uid_t check_uid; + int r; + + assert(m); + assert(ret); + + /* A friendly way to translate a dynamic user's UID into a name. */ + if (!uid_is_dynamic(uid)) + return -ESRCH; + + xsprintf(lock_path, "/run/systemd/dynamic-uid/" UID_FMT, uid); + r = read_one_line_file(lock_path, &user); + if (IN_SET(r, -ENOENT, 0)) + return -ESRCH; + if (r < 0) + return r; + + /* The lock file might be stale, hence let's verify the data before we return it */ + r = dynamic_user_lookup_name(m, user, &check_uid); + if (r < 0) + return r; + if (check_uid != uid) /* lock file doesn't match our own idea */ + return -ESRCH; + + *ret = TAKE_PTR(user); + + return 0; +} + +int dynamic_user_lookup_name(Manager *m, const char *name, uid_t *ret) { + DynamicUser *d; + int r; + + assert(m); + assert(name); + + /* A friendly call for translating a dynamic user's name into its UID */ + + d = hashmap_get(m->dynamic_users, name); + if (!d) + return -ESRCH; + + r = dynamic_user_current(d, ret); + if (r == -EAGAIN) /* not realized yet? */ + return -ESRCH; + + return r; +} + +int dynamic_creds_acquire(DynamicCreds *creds, Manager *m, const char *user, const char *group) { + bool acquired = false; + int r; + + assert(creds); + assert(m); + + /* A DynamicUser object encapsulates an allocation of both a UID and a GID for a specific name. However, some + * services use different user and groups. For cases like that there's DynamicCreds containing a pair of user + * and group. This call allocates a pair. */ + + if (!creds->user && user) { + r = dynamic_user_acquire(m, user, &creds->user); + if (r < 0) + return r; + + acquired = true; + } + + if (!creds->group) { + + if (creds->user && (!group || streq_ptr(user, group))) + creds->group = dynamic_user_ref(creds->user); + else if (group) { + r = dynamic_user_acquire(m, group, &creds->group); + if (r < 0) { + if (acquired) + creds->user = dynamic_user_unref(creds->user); + return r; + } + } + } + + return 0; +} + +int dynamic_creds_realize(DynamicCreds *creds, char **suggested_paths, uid_t *uid, gid_t *gid) { + uid_t u = UID_INVALID; + gid_t g = GID_INVALID; + int r; + + assert(creds); + assert(uid); + assert(gid); + + /* Realize both the referenced user and group */ + + if (creds->user) { + r = dynamic_user_realize(creds->user, suggested_paths, &u, &g, true); + if (r < 0) + return r; + } + + if (creds->group && creds->group != creds->user) { + r = dynamic_user_realize(creds->group, suggested_paths, NULL, &g, false); + if (r < 0) + return r; + } + + *uid = u; + *gid = g; + return 0; +} + +void dynamic_creds_unref(DynamicCreds *creds) { + assert(creds); + + creds->user = dynamic_user_unref(creds->user); + creds->group = dynamic_user_unref(creds->group); +} + +void dynamic_creds_destroy(DynamicCreds *creds) { + assert(creds); + + creds->user = dynamic_user_destroy(creds->user); + creds->group = dynamic_user_destroy(creds->group); +} |