test: Add a targeted test for _dbus_unix_groups_from_uid()

Helps: https://gitlab.freedesktop.org/dbus/dbus/-/issues/343
Signed-off-by: Simon McVittie <smcv@collabora.com>

test/CMakeLists.txt

@@ -215,6 +215,7 @@ if(DBUS_WITH_GLIB)
     add_test_executable(test-sysdeps internals/sysdeps.c ${TEST_LIBRARIES})
     add_test_executable(test-syslog internals/syslog.c ${TEST_LIBRARIES})
     add_test_executable(test-uid-permissions uid-permissions.c ${TEST_LIBRARIES})
+    add_test_executable(test-userdb internals/userdb.c ${TEST_LIBRARIES})
     add_helper_executable(manual-authz manual-authz.c ${TEST_LIBRARIES})
     add_helper_executable(manual-test-thread-blocking thread-blocking.c ${TEST_LIBRARIES})
 endif()

test/Makefile.am

@@ -177,6 +177,9 @@ test_sysdeps_LDADD =  libdbus-testutils.la $(GLIB_LIBS)
 test_syslog_SOURCES = internals/syslog.c
 test_syslog_LDADD = libdbus-testutils.la $(GLIB_LIBS)
 
+test_userdb_SOURCES = internals/userdb.c
+test_userdb_LDADD =  libdbus-testutils.la $(GLIB_LIBS)
+
 test_variant_SOURCES = internals/variant.c
 test_variant_LDADD = libdbus-testutils.la $(GLIB_LIBS)
 
@@ -352,6 +355,7 @@ installable_tests += \
 	test-sysdeps \
 	test-syslog \
 	test-uid-permissions \
+	test-userdb \
 	test-variant \
 	$(NULL)
 

test/internals/userdb.c

@@ -0,0 +1,143 @@
+/*
+ * Copyright © 2023 Collabora Ltd.
+ * SPDX-License-Identifier: MIT
+ */
+
+#include <config.h>
+
+#include <glib.h>
+
+#include <dbus/dbus.h>
+#include "dbus/dbus-sysdeps.h"
+#include "test-utils-glib.h"
+
+#ifdef DBUS_UNIX
+#include <errno.h>
+#include <pwd.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include "dbus/dbus-sysdeps-unix.h"
+#include "dbus/dbus-userdb.h"
+#endif
+
+typedef struct
+{
+  int dummy;
+} Fixture;
+
+static void
+setup (Fixture *f G_GNUC_UNUSED,
+       gconstpointer context G_GNUC_UNUSED)
+{
+}
+
+static void
+test_groups_from_uid (Fixture *f,
+                      gconstpointer context G_GNUC_UNUSED)
+{
+  DBusError error = DBUS_ERROR_INIT;
+  dbus_gid_t *gids = NULL;
+  int n_gids = -1;
+  dbus_bool_t ret;
+#ifdef DBUS_UNIX
+  int i;
+#endif
+
+  /* We assume that uid 0 (root) is available on all Unix systems,
+   * so this should succeed */
+  ret = _dbus_unix_groups_from_uid (0, &gids, &n_gids, &error);
+
+#ifdef DBUS_UNIX
+  test_assert_no_error (&error);
+  g_assert_true (ret);
+  g_assert_cmpint (n_gids, >=, 0);
+
+  g_test_message ("Groups of uid 0:");
+
+  for (i = 0; i < n_gids; i++)
+    {
+      g_test_message ("[%d]: %ld", i, (long) gids[i]);
+      g_assert_cmpint (gids[i], >=, 0);
+    }
+#else
+  g_assert_cmpstr (error.name, ==, DBUS_ERROR_NOT_SUPPORTED);
+  g_assert_false (ret);
+  g_test_message ("Getting Unix groups on Windows failed as expected: %s: %s",
+                  error.name, error.message);
+  g_assert_null (gids);
+  g_assert_cmpint (n_gids, <=, 0);
+#endif
+
+  dbus_free (gids);
+  dbus_error_free (&error);
+
+#ifdef DBUS_UNIX
+  /* Assume that the current uid is something sensible */
+  ret = _dbus_unix_groups_from_uid (geteuid (), &gids, &n_gids, &error);
+  test_assert_no_error (&error);
+  g_assert_true (ret);
+  g_assert_cmpint (n_gids, >=, 0);
+
+  g_test_message ("Groups of uid %ld:", (long) geteuid ());
+
+  for (i = 0; i < n_gids; i++)
+    {
+      g_test_message ("[%d]: %ld", i, (long) gids[i]);
+      g_assert_cmpint (gids[i], >=, 0);
+    }
+
+  g_test_message ("Total: %i groups", n_gids);
+
+  dbus_free (gids);
+  dbus_error_free (&error);
+
+  errno = 0;
+
+  /* arbitrarily chosen, probably isn't a valid uid */
+  if (getpwuid (31337) == NULL)
+    {
+      g_test_message ("uid 31337 doesn't exist: %s",
+                      errno == 0 ? "(no errno)" : g_strerror (errno));
+      ret = _dbus_unix_groups_from_uid (31337, &gids, &n_gids, &error);
+      g_assert_nonnull (error.name);
+      g_assert_nonnull (error.message);
+      g_assert_false (ret);
+      g_test_message ("Getting groups from non-uid failed as expected: %s: %s",
+                      error.name, error.message);
+      /* The Unix implementation always clears gids/n_gids,
+       * even on failure, and even if they were uninitialized */
+      g_assert_null (gids);
+      g_assert_cmpint (n_gids, ==, 0);
+
+      dbus_free (gids);
+      dbus_error_free (&error);
+    }
+  else
+    {
+      g_test_skip ("against our expectations, uid 31337 exists on this system");
+    }
+#endif
+}
+
+static void
+teardown (Fixture *f G_GNUC_UNUSED,
+          gconstpointer context G_GNUC_UNUSED)
+{
+}
+
+int
+main (int argc,
+      char **argv)
+{
+  int ret;
+
+  test_init (&argc, &argv);
+
+  g_test_add ("/userdb/groups_from_uid",
+              Fixture, NULL, setup, test_groups_from_uid, teardown);
+
+  ret = g_test_run ();
+  dbus_shutdown ();
+  return ret;
+}

test/meson.build

@@ -556,6 +556,12 @@ if use_glib
             'deps': [ glib, gio, ],
             'suite': ['runs-dbus-daemon'],
         },
+        {
+            'name': 'userdb',
+            'srcs': [ 'internals/userdb.c' ],
+            'link': [ libdbus_testutils, ],
+            'deps': [ glib, gio, ],
+        },
         {
             'name': 'variant',
             'srcs': [ 'internals/variant.c' ],