X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?p=elogind.git;a=blobdiff_plain;f=src%2Fbasic%2Fuser-util.c;h=893790f78f861ac7affb9158223195634246601c;hp=0d199cf18da7dbfbce93fbae2206cba66aa8d4a9;hb=1e2c11636861da69c5637e59afe207a11dd4f386;hpb=4d1a9dbea12127dd8fd8c0ee9a53b544ef92f6bf

diff --git a/src/basic/user-util.c b/src/basic/user-util.c
index 0d199cf18..893790f78 100644
--- a/src/basic/user-util.c
+++ b/src/basic/user-util.c
@@ -463,9 +463,11 @@ 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;
@@ -608,3 +610,32 @@ 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;
+}