X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?a=blobdiff_plain;f=src%2Fbasic%2Fuser-util.c;h=332e1c6a9c7bc6a4b640208f70958a45004fa3c5;hb=f082899f180431f04553e4ee3b0968020ef59188;hp=2ba5c8575f414cc57257ff192e94e5c9539a814e;hpb=599f015c68718f04ee1946fc263aad8aaa614072;p=elogind.git

diff --git a/src/basic/user-util.c b/src/basic/user-util.c
index 2ba5c8575..332e1c6a9 100644
--- a/src/basic/user-util.c
+++ b/src/basic/user-util.c
@@ -29,19 +29,25 @@
 #include <string.h>
 #include <sys/stat.h>
 #include <unistd.h>
+#include <utmp.h>
 
-#include "missing.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;
@@ -175,6 +181,36 @@ int get_user_creds(
         return 0;
 }
 
+#if 0 /// UNNEEDED by elogind
+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;
@@ -216,6 +252,7 @@ int get_group_creds(const char **groupname, gid_t *gid) {
 
         return 0;
 }
+#endif // 0
 
 char* uid_to_name(uid_t uid) {
         char *ret;
@@ -431,9 +468,11 @@ int get_shell(char **_s) {
 #endif // 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;
@@ -490,7 +529,15 @@ bool valid_user_group_name(const char *u) {
         const char *i;
         long sz;
 
-        /* Checks if the specified name is a valid user/group name. */
+        /* 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;
@@ -576,3 +623,32 @@ bool valid_home(const char *p) {
 
         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;
+}