user-util: add lookup_groups_in_files

src/basic/user-util.c

@@ -1366,6 +1366,67 @@ int sysconf_ngroups_max(void) {
         return ngroups_max;
 }
 
+ssize_t lookup_groups_in_files(
+                char * const *files,
+                const char *name,
+                gid_t gid,
+                gid_t **ret) {
+
+        _cleanup_free_ gid_t *arr = NULL;
+        ssize_t n_arr = 0;
+        int r;
+
+        assert(files);
+        assert(name);
+        assert(gid_is_valid(gid));
+
+        int ngroups_max = sysconf_ngroups_max();
+        if (ngroups_max < 0)
+                return ngroups_max;
+
+        if (!GREEDY_REALLOC(arr, n_arr + 1))
+                return -ENOMEM;
+        arr[n_arr++] = gid;
+
+        STRV_FOREACH(fname, files) {
+                _cleanup_fclose_ FILE *f = NULL;
+                struct group *gr;
+
+                r = fopen_unlocked(*fname, "re", &f);
+                if (r == -ENOENT)
+                        continue;
+                if (r < 0)
+                        return r;
+
+                while ((r = fgetgrent_sane(f, &gr)) > 0) {
+                        if (gid == gr->gr_gid)
+                                continue;
+
+                        /* Deduplicate groups, in case the group is doubly defined in the same or
+                         * different files. */
+                        if (gid_list_has(arr, n_arr, gr->gr_gid))
+                                continue;
+
+                        if (!strv_contains(gr->gr_mem, name))
+                                continue;
+
+                        /* Do not allow more than _SC_NGROUPS_MAX. */
+                        if (n_arr >= ngroups_max)
+                                return -ENOBUFS;
+
+                        if (!GREEDY_REALLOC(arr, n_arr + 1))
+                                return -ENOMEM;
+                        arr[n_arr++] = gr->gr_gid;
+                }
+                if (r < 0)
+                        return r;
+        }
+
+        if (ret)
+                *ret = TAKE_PTR(arr);
+        return n_arr;
+}
+
 static size_t getgr_buffer_size(void) {
         long bufsize = sysconf(_SC_GETGR_R_SIZE_MAX);
         return bufsize <= 0 ? 4096U : (size_t) bufsize;

src/basic/user-util.h

@@ -185,6 +185,11 @@ int lookup_grent_in_files(
                 const char *name,
                 gid_t gid,
                 struct group **ret);
+ssize_t lookup_groups_in_files(
+                char * const *files,
+                const char *name,
+                gid_t gid,
+                gid_t **ret);
 
 int getpwuid_malloc(uid_t uid, struct passwd **ret);
 int getpwnam_malloc(const char *name, struct passwd **ret);

src/test/test-user-util.c

@@ -596,4 +596,38 @@ TEST(lookup_grent_in_files) {
         ASSERT_STREQ(gr->gr_name, "testgroup1");
 }
 
+TEST(lookup_groups_in_files) {
+        _cleanup_(unlink_tempfilep) char fn[] = "/tmp/test-user-util-group-XXXXXX";
+        _cleanup_fclose_ FILE *f = NULL;
+
+        ASSERT_OK(fmkostemp_safe(fn, "w", &f));
+        ASSERT_OK(write_string_stream(
+                                f,
+                                "testgroup1:x:100:testuser1,testuser2\n"
+                                "testgroup2:x:200:testuser1\n"
+                                "testgroup3:x:300:\n"
+                                "testgroup4:x:400:root,somebody,testuser1\n",
+                                /* flags= */ 0));
+        ASSERT_OK(fflush_and_check(f));
+
+        char **files = STRV_MAKE(fn);
+
+        /* Lookup by name */
+        _cleanup_free_ gid_t *arr = NULL;
+
+        ASSERT_EQ(lookup_groups_in_files(files, "testuser1", 100, &arr), 3);
+        gid_t exp1[] = { 100, 200, 400 };
+        ASSERT_EQ(memcmp(arr, exp1, sizeof(exp1)), 0);
+        arr = mfree(arr);
+
+        ASSERT_EQ(lookup_groups_in_files(files, "testuser1", 0, &arr), 4);
+        gid_t exp2[] = { 0, 100, 200, 400 };
+        ASSERT_EQ(memcmp(arr, exp2, sizeof(exp2)), 0);
+        arr = mfree(arr);
+
+        ASSERT_EQ(lookup_groups_in_files(files, "testuser3", 300, &arr), 1);
+        gid_t exp3[] = { 300 };
+        ASSERT_EQ(memcmp(arr, exp3, sizeof(exp3)), 0);
+}
+
 DEFINE_TEST_MAIN(LOG_INFO);