-/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
-
+/* SPDX-License-Identifier: LGPL-2.1+ */
/***
This file is part of systemd.
#include <string.h>
#include <sys/stat.h>
#include <unistd.h>
+#include <utmp.h>
#include "alloc-util.h"
#include "fd-util.h"
-#include "formats-util.h"
+#include "fileio.h"
+#include "format-util.h"
#include "macro.h"
+#include "missing.h"
#include "parse-util.h"
#include "path-util.h"
#include "string-util.h"
+#include "strv.h"
#include "user-util.h"
+#include "utf8.h"
bool uid_is_valid(uid_t uid) {
+ /* Also see POSIX IEEE Std 1003.1-2008, 2016 Edition, 3.436. */
+
/* Some libc APIs use UID_INVALID as special placeholder */
if (uid == (uid_t) UINT32_C(0xFFFFFFFF))
return false;
assert(username);
assert(*username);
- /* We enforce some special rules for uid=0: in order to avoid
- * NSS lookups for root we hardcode its data. */
+ /* We enforce some special rules for uid=0 and uid=65534: in order to avoid NSS lookups for root we hardcode
+ * their user record data. */
- if (streq(*username, "root") || streq(*username, "0")) {
+ if (STR_IN_SET(*username, "root", "0")) {
*username = "root";
if (uid)
*uid = 0;
-
if (gid)
*gid = 0;
return 0;
}
+ if (synthesize_nobody() &&
+ STR_IN_SET(*username, NOBODY_USER_NAME, "65534")) {
+ *username = NOBODY_USER_NAME;
+
+ if (uid)
+ *uid = UID_NOBODY;
+ if (gid)
+ *gid = GID_NOBODY;
+
+ if (home)
+ *home = "/";
+
+ if (shell)
+ *shell = "/sbin/nologin";
+
+ return 0;
+ }
+
if (parse_uid(*username, &u) >= 0) {
errno = 0;
p = getpwuid(u);
return 0;
}
+int get_user_creds_clean(
+ const char **username,
+ uid_t *uid, gid_t *gid,
+ const char **home,
+ const char **shell) {
+
+ int r;
+
+ /* Like get_user_creds(), but resets home/shell to NULL if they don't contain anything relevant. */
+
+ r = get_user_creds(username, uid, gid, home, shell);
+ if (r < 0)
+ return r;
+
+ if (shell &&
+ (isempty(*shell) || PATH_IN_SET(*shell,
+ "/bin/nologin",
+ "/sbin/nologin",
+ "/usr/bin/nologin",
+ "/usr/sbin/nologin")))
+ *shell = NULL;
+
+ if (home &&
+ (isempty(*home) || path_equal(*home, "/")))
+ *home = NULL;
+
+ return 0;
+}
+
int get_group_creds(const char **groupname, gid_t *gid) {
struct group *g;
gid_t id;
/* We enforce some special rules for gid=0: in order to avoid
* NSS lookups for root we hardcode its data. */
- if (streq(*groupname, "root") || streq(*groupname, "0")) {
+ if (STR_IN_SET(*groupname, "root", "0")) {
*groupname = "root";
if (gid)
return 0;
}
+ if (synthesize_nobody() &&
+ STR_IN_SET(*groupname, NOBODY_GROUP_NAME, "65534")) {
+ *groupname = NOBODY_GROUP_NAME;
+
+ if (gid)
+ *gid = GID_NOBODY;
+
+ return 0;
+ }
+
if (parse_gid(*groupname, &id) >= 0) {
errno = 0;
g = getgrgid(id);
/* Shortcut things to avoid NSS lookups */
if (uid == 0)
return strdup("root");
+ if (synthesize_nobody() &&
+ uid == UID_NOBODY)
+ return strdup(NOBODY_USER_NAME);
if (uid_is_valid(uid)) {
long bufsize;
if (gid == 0)
return strdup("root");
+ if (synthesize_nobody() &&
+ gid == GID_NOBODY)
+ return strdup(NOBODY_GROUP_NAME);
if (gid_is_valid(gid)) {
long bufsize;
}
int in_gid(gid_t gid) {
+ long ngroups_max;
gid_t *gids;
- int ngroups_max, r, i;
+ int r, i;
if (getgid() == gid)
return 1;
ngroups_max = sysconf(_SC_NGROUPS_MAX);
assert(ngroups_max > 0);
- gids = alloca(sizeof(gid_t) * ngroups_max);
+ gids = newa(gid_t, ngroups_max);
r = getgroups(ngroups_max, gids);
if (r < 0)
return 0;
}
- /* Hardcode home directory for root to avoid NSS */
+ /* Hardcode home directory for root and nobody to avoid NSS */
u = getuid();
if (u == 0) {
h = strdup("/root");
*_h = h;
return 0;
}
+ if (synthesize_nobody() &&
+ u == UID_NOBODY) {
+ h = strdup("/");
+ if (!h)
+ return -ENOMEM;
+
+ *_h = h;
+ return 0;
+ }
/* Check the database... */
errno = 0;
return 0;
}
- /* Hardcode home directory for root to avoid NSS */
+ /* Hardcode shell for root and nobody to avoid NSS */
u = getuid();
if (u == 0) {
s = strdup("/bin/sh");
*_s = s;
return 0;
}
+ if (synthesize_nobody() &&
+ u == UID_NOBODY) {
+ s = strdup("/sbin/nologin");
+ if (!s)
+ return -ENOMEM;
+
+ *_s = s;
+ return 0;
+ }
/* Check the database... */
errno = 0;
}
int reset_uid_gid(void) {
+ int r;
- if (setgroups(0, NULL) < 0)
- return -errno;
+ r = maybe_setgroups(0, NULL);
+ if (r < 0)
+ return r;
if (setresgid(0, 0, 0) < 0)
return -errno;
*
* Note that shadow-utils also takes per-database locks in
* addition to lckpwdf(). However, we don't given that they
- * are redundant as they they invoke lckpwdf() first and keep
+ * are redundant as they invoke lckpwdf() first and keep
* it during everything they do. The per-database locks are
* awfully racy, and thus we just won't do them. */
if (root)
- path = prefix_roota(root, "/etc/.pwd.lock");
+ path = prefix_roota(root, ETC_PASSWD_LOCK_PATH);
else
- path = "/etc/.pwd.lock";
+ path = ETC_PASSWD_LOCK_PATH;
fd = open(path, O_WRONLY|O_CREAT|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW, 0600);
if (fd < 0)
- return -errno;
+ return log_debug_errno(errno, "Cannot open %s: %m", path);
r = fcntl(fd, F_SETLKW, &flock);
if (r < 0) {
safe_close(fd);
- return -errno;
+ return log_debug_errno(errno, "Locking %s failed: %m", path);
}
return fd;
}
+
+bool valid_user_group_name(const char *u) {
+ const char *i;
+ long sz;
+
+ /* Checks if the specified name is a valid user/group name. Also see POSIX IEEE Std 1003.1-2008, 2016 Edition,
+ * 3.437. We are a bit stricter here however. Specifically we deviate from POSIX rules:
+ *
+ * - We don't allow any dots (this would break chown syntax which permits dots as user/group name separator)
+ * - We require that names fit into the appropriate utmp field
+ * - We don't allow empty user names
+ *
+ * Note that other systems are even more restrictive, and don't permit underscores or uppercase characters.
+ */
+
+ if (isempty(u))
+ return false;
+
+ if (!(u[0] >= 'a' && u[0] <= 'z') &&
+ !(u[0] >= 'A' && u[0] <= 'Z') &&
+ u[0] != '_')
+ return false;
+
+ for (i = u+1; *i; i++) {
+ if (!(*i >= 'a' && *i <= 'z') &&
+ !(*i >= 'A' && *i <= 'Z') &&
+ !(*i >= '0' && *i <= '9') &&
+ !IN_SET(*i, '_', '-'))
+ return false;
+ }
+
+ sz = sysconf(_SC_LOGIN_NAME_MAX);
+ assert_se(sz > 0);
+
+ if ((size_t) (i-u) > (size_t) sz)
+ return false;
+
+ if ((size_t) (i-u) > UT_NAMESIZE - 1)
+ return false;
+
+ return true;
+}
+
+bool valid_user_group_name_or_id(const char *u) {
+
+ /* Similar as above, but is also fine with numeric UID/GID specifications, as long as they are in the right
+ * range, and not the invalid user ids. */
+
+ if (isempty(u))
+ return false;
+
+ if (valid_user_group_name(u))
+ return true;
+
+ return parse_uid(u, NULL) >= 0;
+}
+
+bool valid_gecos(const char *d) {
+
+ if (!d)
+ return false;
+
+ if (!utf8_is_valid(d))
+ return false;
+
+ if (string_has_cc(d, NULL))
+ return false;
+
+ /* Colons are used as field separators, and hence not OK */
+ if (strchr(d, ':'))
+ return false;
+
+ return true;
+}
+
+bool valid_home(const char *p) {
+ /* Note that this function is also called by valid_shell(), any
+ * changes must account for that. */
+
+ if (isempty(p))
+ return false;
+
+ if (!utf8_is_valid(p))
+ return false;
+
+ if (string_has_cc(p, NULL))
+ return false;
+
+ if (!path_is_absolute(p))
+ return false;
+
+ if (!path_is_normalized(p))
+ return false;
+
+ /* Colons are used as field separators, and hence not OK */
+ if (strchr(p, ':'))
+ return false;
+
+ return true;
+}
+
+int maybe_setgroups(size_t size, const gid_t *list) {
+ int r;
+
+ /* Check if setgroups is allowed before we try to drop all the auxiliary groups */
+ if (size == 0) { /* Dropping all aux groups? */
+ _cleanup_free_ char *setgroups_content = NULL;
+ bool can_setgroups;
+
+ r = read_one_line_file("/proc/self/setgroups", &setgroups_content);
+ if (r == -ENOENT)
+ /* Old kernels don't have /proc/self/setgroups, so assume we can use setgroups */
+ can_setgroups = true;
+ else if (r < 0)
+ return r;
+ else
+ can_setgroups = streq(setgroups_content, "allow");
+
+ if (!can_setgroups) {
+ log_debug("Skipping setgroups(), /proc/self/setgroups is set to 'deny'");
+ return 0;
+ }
+ }
+
+ if (setgroups(size, list) < 0)
+ return -errno;
+
+ return 0;
+}
+
+bool synthesize_nobody(void) {
+
+#ifdef NOLEGACY
+ return true;
+#else
+ /* Returns true when we shall synthesize the "nobody" user (which we do by default). This can be turned off by
+ * touching /etc/systemd/dont-synthesize-nobody in order to provide upgrade compatibility with legacy systems
+ * that used the "nobody" user name and group name for other UIDs/GIDs than 65534.
+ *
+ * Note that we do not employ any kind of synchronization on the following caching variable. If the variable is
+ * accessed in multi-threaded programs in the worst case it might happen that we initialize twice, but that
+ * shouldn't matter as each initialization should come to the same result. */
+ static int cache = -1;
+
+ if (cache < 0)
+ cache = access("/etc/systemd/dont-synthesize-nobody", F_OK) < 0;
+
+ return cache;
+#endif
+}
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