core: merge branch 'juspence:main' (parts)

Merge a subset of merge-request 1031, with a few follow-up fixes.

See-also: https://gitlab.freedesktop.org/NetworkManager/NetworkManager/-/issues/843

https://gitlab.freedesktop.org/NetworkManager/NetworkManager/-/merge_requests/1031

src/core/main-utils.c

@@ -209,15 +209,6 @@ nm_main_utils_ensure_not_running_pidfile(const char *pidfile)
     }
 }
 
-void
-nm_main_utils_ensure_root()
-{
-    if (getuid() != 0) {
-        fprintf(stderr, _("You must be root to run %s!\n"), g_get_prgname() ?: "");
-        exit(1);
-    }
-}
-
 gboolean
 nm_main_utils_early_setup(const char   *progname,
                           int          *argc,

src/core/main-utils.h

@@ -6,8 +6,6 @@
 #ifndef __MAIN_UTILS_H__
 #define __MAIN_UTILS_H__
 
-void nm_main_utils_ensure_root(void);
-
 void nm_main_utils_setup_signals(GMainLoop *main_loop);
 
 void nm_main_utils_ensure_statedir(void);

src/core/main.c

@@ -328,8 +328,6 @@ main(int argc, char *argv[])
         exit(result);
     }
 
-    nm_main_utils_ensure_root();
-
     nm_main_utils_ensure_not_running_pidfile(global_opt.pidfile);
 
     nm_main_utils_ensure_statedir();

src/core/nm-core-utils.c

@@ -5145,3 +5145,59 @@ nm_utils_spawn_helper_finish(GAsyncResult *result, GError **error)
 
     return g_task_propagate_pointer(task, error);
 }
+
+/*****************************************************************************/
+
+/**
+ * nm_utils_get_nm_uid:
+ *
+ * Checks what EUID NetworkManager is running as.
+ * Saves the EUID so it can be reused without making many syscalls.
+ */
+uid_t
+nm_utils_get_nm_uid(void)
+{
+    static int u_static = -1;
+    int        u;
+
+again:
+    if ((u = g_atomic_int_get(&u_static)) == -1) {
+        uid_t u2;
+
+        u2 = geteuid();
+        u  = u2;
+        nm_assert(u == u2);
+        nm_assert(u >= 0);
+        if (!g_atomic_int_compare_and_exchange(&u_static, -1, u))
+            goto again;
+    }
+
+    return u;
+}
+
+/**
+ * nm_utils_get_nm_gid:
+ *
+ * Checks what EGID NetworkManager is running as.
+ * Saves the EGID so it can be reused without making many syscalls.
+ */
+gid_t
+nm_utils_get_nm_gid(void)
+{
+    static int g_static = -1;
+    int        g;
+
+again:
+    if ((g = g_atomic_int_get(&g_static)) == -1) {
+        gid_t g2;
+
+        g2 = geteuid();
+        g  = g2;
+        nm_assert(g == g2);
+        nm_assert(g >= 0);
+        if (!g_atomic_int_compare_and_exchange(&g_static, -1, g))
+            goto again;
+    }
+
+    return g;
+}

src/core/nm-core-utils.h

@@ -9,6 +9,7 @@
 
 #include <stdio.h>
 #include <arpa/inet.h>
+#include <sys/types.h>
 
 #include "nm-connection.h"
 
@@ -470,4 +471,10 @@ void nm_utils_spawn_helper(const char *const  *args,
 
 char *nm_utils_spawn_helper_finish(GAsyncResult *result, GError **error);
 
+/*****************************************************************************/
+
+uid_t nm_utils_get_nm_uid(void);
+
+gid_t nm_utils_get_nm_gid(void);
+
 #endif /* __NM_CORE_UTILS_H__ */

src/core/settings/plugins/keyfile/nms-keyfile-utils.c

@@ -337,7 +337,7 @@ nms_keyfile_utils_check_file_permissions_stat(NMSKeyfileFiletype filetype,
         g_return_val_if_reached(FALSE);
 
     if (!NM_FLAGS_HAS(nm_utils_get_testing(), NM_UTILS_TEST_NO_KEYFILE_OWNER_CHECK)) {
-        if (st->st_uid != 0) {
+        if (!NM_IN_SET(st->st_uid, 0, nm_utils_get_nm_uid())) {
             g_set_error(error,
                         NM_SETTINGS_ERROR,
                         NM_SETTINGS_ERROR_INVALID_CONNECTION,

src/core/settings/plugins/keyfile/nms-keyfile-writer.c

@@ -444,8 +444,8 @@ nms_keyfile_writer_connection(NMConnection                   *connection,
                                       keyfile_dir,
                                       profile_dir,
                                       TRUE,
-                                      0,
-                                      0,
+                                      nm_utils_get_nm_uid(),
+                                      nm_utils_get_nm_gid(),
                                       existing_path,
                                       existing_path_read_only,
                                       force_rename,