1 /* SPDX-License-Identifier: LGPL-2.1+ */
17 #include "alloc-util.h"
20 #include "format-util.h"
23 #include "parse-util.h"
24 #include "path-util.h"
25 #include "string-util.h"
27 #include "user-util.h"
30 bool uid_is_valid(uid_t uid) {
32 /* Also see POSIX IEEE Std 1003.1-2008, 2016 Edition, 3.436. */
34 /* Some libc APIs use UID_INVALID as special placeholder */
35 if (uid == (uid_t) UINT32_C(0xFFFFFFFF))
38 /* A long time ago UIDs where 16bit, hence explicitly avoid the 16bit -1 too */
39 if (uid == (uid_t) UINT32_C(0xFFFF))
45 int parse_uid(const char *s, uid_t *ret) {
51 assert_cc(sizeof(uid_t) == sizeof(uint32_t));
52 r = safe_atou32(s, &uid);
56 if (!uid_is_valid(uid))
57 return -ENXIO; /* we return ENXIO instead of EINVAL
58 * here, to make it easy to distuingish
59 * invalid numeric uids from invalid
68 char* getlogname_malloc(void) {
72 if (isatty(STDIN_FILENO) && fstat(STDIN_FILENO, &st) >= 0)
77 return uid_to_name(uid);
80 #if 0 /// UNNEEDED by elogind
81 char *getusername_malloc(void) {
88 return uid_to_name(getuid());
93 const char **username,
94 uid_t *uid, gid_t *gid,
104 /* We enforce some special rules for uid=0 and uid=65534: in order to avoid NSS lookups for root we hardcode
105 * their user record data. */
107 if (STR_IN_SET(*username, "root", "0")) {
124 if (synthesize_nobody() &&
125 STR_IN_SET(*username, NOBODY_USER_NAME, "65534")) {
126 *username = NOBODY_USER_NAME;
137 *shell = "/sbin/nologin";
142 if (parse_uid(*username, &u) >= 0) {
146 /* If there are multiple users with the same id, make
147 * sure to leave $USER to the configured value instead
148 * of the first occurrence in the database. However if
149 * the uid was configured by a numeric uid, then let's
150 * pick the real username from /etc/passwd. */
152 *username = p->pw_name;
155 p = getpwnam(*username);
159 return errno > 0 ? -errno : -ESRCH;
162 if (!uid_is_valid(p->pw_uid))
169 if (!gid_is_valid(p->pw_gid))
179 *shell = p->pw_shell;
184 static inline bool is_nologin_shell(const char *shell) {
186 return PATH_IN_SET(shell,
187 /* 'nologin' is the friendliest way to disable logins for a user account. It prints a nice
188 * message and exits. Different distributions place the binary at different places though,
189 * hence let's list them all. */
194 /* 'true' and 'false' work too for the same purpose, but are less friendly as they don't do
195 * any message printing. Different distributions place the binary at various places but at
196 * least not in the 'sbin' directory. */
203 #if 0 /// UNNEEDED by elogind
204 int get_user_creds_clean(
205 const char **username,
206 uid_t *uid, gid_t *gid,
208 const char **shell) {
212 /* Like get_user_creds(), but resets home/shell to NULL if they don't contain anything relevant. */
214 r = get_user_creds(username, uid, gid, home, shell);
219 (isempty(*shell) || is_nologin_shell(*shell)))
222 if (home && empty_or_root(*home))
228 int get_group_creds(const char **groupname, gid_t *gid) {
234 /* We enforce some special rules for gid=0: in order to avoid
235 * NSS lookups for root we hardcode its data. */
237 if (STR_IN_SET(*groupname, "root", "0")) {
246 if (synthesize_nobody() &&
247 STR_IN_SET(*groupname, NOBODY_GROUP_NAME, "65534")) {
248 *groupname = NOBODY_GROUP_NAME;
256 if (parse_gid(*groupname, &id) >= 0) {
261 *groupname = g->gr_name;
264 g = getgrnam(*groupname);
268 return errno > 0 ? -errno : -ESRCH;
271 if (!gid_is_valid(g->gr_gid))
281 char* uid_to_name(uid_t uid) {
285 /* Shortcut things to avoid NSS lookups */
287 return strdup("root");
288 if (synthesize_nobody() &&
290 return strdup(NOBODY_USER_NAME);
292 if (uid_is_valid(uid)) {
295 bufsize = sysconf(_SC_GETPW_R_SIZE_MAX);
300 struct passwd pwbuf, *pw = NULL;
301 _cleanup_free_ char *buf = NULL;
303 buf = malloc(bufsize);
307 r = getpwuid_r(uid, &pwbuf, buf, (size_t) bufsize, &pw);
309 return strdup(pw->pw_name);
317 if (asprintf(&ret, UID_FMT, uid) < 0)
323 char* gid_to_name(gid_t gid) {
328 return strdup("root");
329 if (synthesize_nobody() &&
331 return strdup(NOBODY_GROUP_NAME);
333 if (gid_is_valid(gid)) {
336 bufsize = sysconf(_SC_GETGR_R_SIZE_MAX);
341 struct group grbuf, *gr = NULL;
342 _cleanup_free_ char *buf = NULL;
344 buf = malloc(bufsize);
348 r = getgrgid_r(gid, &grbuf, buf, (size_t) bufsize, &gr);
350 return strdup(gr->gr_name);
358 if (asprintf(&ret, GID_FMT, gid) < 0)
364 #if 0 /// UNNEEDED by elogind
365 int in_gid(gid_t gid) {
373 if (getegid() == gid)
376 if (!gid_is_valid(gid))
379 ngroups_max = sysconf(_SC_NGROUPS_MAX);
380 assert(ngroups_max > 0);
382 gids = newa(gid_t, ngroups_max);
384 r = getgroups(ngroups_max, gids);
388 for (i = 0; i < r; i++)
395 int in_group(const char *name) {
399 r = get_group_creds(&name, &gid);
406 int get_home_dir(char **_h) {
414 /* Take the user specified one */
415 e = secure_getenv("HOME");
416 if (e && path_is_absolute(e)) {
425 /* Hardcode home directory for root and nobody to avoid NSS */
435 if (synthesize_nobody() &&
445 /* Check the database... */
449 return errno > 0 ? -errno : -ESRCH;
451 if (!path_is_absolute(p->pw_dir))
454 h = strdup(p->pw_dir);
462 int get_shell(char **_s) {
470 /* Take the user specified one */
481 /* Hardcode shell for root and nobody to avoid NSS */
484 s = strdup("/bin/sh");
491 if (synthesize_nobody() &&
493 s = strdup("/sbin/nologin");
501 /* Check the database... */
505 return errno > 0 ? -errno : -ESRCH;
507 if (!path_is_absolute(p->pw_shell))
510 s = strdup(p->pw_shell);
519 int reset_uid_gid(void) {
522 r = maybe_setgroups(0, NULL);
526 if (setresgid(0, 0, 0) < 0)
529 if (setresuid(0, 0, 0) < 0)
535 #if 0 /// UNNEEDED by elogind
536 int take_etc_passwd_lock(const char *root) {
538 struct flock flock = {
540 .l_whence = SEEK_SET,
548 /* This is roughly the same as lckpwdf(), but not as awful. We
549 * don't want to use alarm() and signals, hence we implement
550 * our own trivial version of this.
552 * Note that shadow-utils also takes per-database locks in
553 * addition to lckpwdf(). However, we don't given that they
554 * are redundant as they invoke lckpwdf() first and keep
555 * it during everything they do. The per-database locks are
556 * awfully racy, and thus we just won't do them. */
559 path = prefix_roota(root, ETC_PASSWD_LOCK_PATH);
561 path = ETC_PASSWD_LOCK_PATH;
563 fd = open(path, O_WRONLY|O_CREAT|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW, 0600);
565 return log_debug_errno(errno, "Cannot open %s: %m", path);
567 r = fcntl(fd, F_SETLKW, &flock);
570 return log_debug_errno(errno, "Locking %s failed: %m", path);
577 bool valid_user_group_name(const char *u) {
581 /* Checks if the specified name is a valid user/group name. Also see POSIX IEEE Std 1003.1-2008, 2016 Edition,
582 * 3.437. We are a bit stricter here however. Specifically we deviate from POSIX rules:
584 * - We don't allow any dots (this would break chown syntax which permits dots as user/group name separator)
585 * - We require that names fit into the appropriate utmp field
586 * - We don't allow empty user names
588 * Note that other systems are even more restrictive, and don't permit underscores or uppercase characters.
594 if (!(u[0] >= 'a' && u[0] <= 'z') &&
595 !(u[0] >= 'A' && u[0] <= 'Z') &&
599 for (i = u+1; *i; i++) {
600 if (!(*i >= 'a' && *i <= 'z') &&
601 !(*i >= 'A' && *i <= 'Z') &&
602 !(*i >= '0' && *i <= '9') &&
603 !IN_SET(*i, '_', '-'))
607 sz = sysconf(_SC_LOGIN_NAME_MAX);
610 if ((size_t) (i-u) > (size_t) sz)
613 if ((size_t) (i-u) > UT_NAMESIZE - 1)
619 bool valid_user_group_name_or_id(const char *u) {
621 /* Similar as above, but is also fine with numeric UID/GID specifications, as long as they are in the right
622 * range, and not the invalid user ids. */
627 if (valid_user_group_name(u))
630 return parse_uid(u, NULL) >= 0;
633 bool valid_gecos(const char *d) {
638 if (!utf8_is_valid(d))
641 if (string_has_cc(d, NULL))
644 /* Colons are used as field separators, and hence not OK */
651 bool valid_home(const char *p) {
652 /* Note that this function is also called by valid_shell(), any
653 * changes must account for that. */
658 if (!utf8_is_valid(p))
661 if (string_has_cc(p, NULL))
664 if (!path_is_absolute(p))
667 if (!path_is_normalized(p))
670 /* Colons are used as field separators, and hence not OK */
677 int maybe_setgroups(size_t size, const gid_t *list) {
680 /* Check if setgroups is allowed before we try to drop all the auxiliary groups */
681 if (size == 0) { /* Dropping all aux groups? */
682 _cleanup_free_ char *setgroups_content = NULL;
685 r = read_one_line_file("/proc/self/setgroups", &setgroups_content);
687 /* Old kernels don't have /proc/self/setgroups, so assume we can use setgroups */
688 can_setgroups = true;
692 can_setgroups = streq(setgroups_content, "allow");
694 if (!can_setgroups) {
695 log_debug("Skipping setgroups(), /proc/self/setgroups is set to 'deny'");
700 if (setgroups(size, list) < 0)
706 bool synthesize_nobody(void) {
711 /* Returns true when we shall synthesize the "nobody" user (which we do by default). This can be turned off by
712 * touching /etc/systemd/dont-synthesize-nobody in order to provide upgrade compatibility with legacy systems
713 * that used the "nobody" user name and group name for other UIDs/GIDs than 65534.
715 * Note that we do not employ any kind of synchronization on the following caching variable. If the variable is
716 * accessed in multi-threaded programs in the worst case it might happen that we initialize twice, but that
717 * shouldn't matter as each initialization should come to the same result. */
718 static int cache = -1;
721 cache = access("/etc/elogind/dont-synthesize-nobody", F_OK) < 0;
727 #if 0 /// UNNEEDED by elogind
728 int putpwent_sane(const struct passwd *pw, FILE *stream) {
733 if (putpwent(pw, stream) != 0)
734 return errno > 0 ? -errno : -EIO;
739 int putspent_sane(const struct spwd *sp, FILE *stream) {
744 if (putspent(sp, stream) != 0)
745 return errno > 0 ? -errno : -EIO;
750 int putgrent_sane(const struct group *gr, FILE *stream) {
755 if (putgrent(gr, stream) != 0)
756 return errno > 0 ? -errno : -EIO;
762 int putsgent_sane(const struct sgrp *sg, FILE *stream) {
767 if (putsgent(sg, stream) != 0)
768 return errno > 0 ? -errno : -EIO;
774 int fgetpwent_sane(FILE *stream, struct passwd **pw) {
781 p = fgetpwent(stream);
782 if (!p && errno != ENOENT)
783 return errno > 0 ? -errno : -EIO;
789 int fgetspent_sane(FILE *stream, struct spwd **sp) {
796 s = fgetspent(stream);
797 if (!s && errno != ENOENT)
798 return errno > 0 ? -errno : -EIO;
804 int fgetgrent_sane(FILE *stream, struct group **gr) {
811 g = fgetgrent(stream);
812 if (!g && errno != ENOENT)
813 return errno > 0 ? -errno : -EIO;
820 int fgetsgent_sane(FILE *stream, struct sgrp **sg) {
827 s = fgetsgent(stream);
828 if (!s && errno != ENOENT)
829 return errno > 0 ? -errno : -EIO;