+
+bool valid_user_group_name(const char *u) {
+ const char *i;
+ long sz;
+
+ /* Checks if the specified name is a valid user/group name. */
+
+ 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') &&
+ *i != '_' &&
+ *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) {
+
+ 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_safe(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;
+}