Reproducer for the null pw_name returned from getpwuid()

Signed-off-by: Jakub Jelen <jjelen@redhat.com>

glib/tests/getpwuid-preload.c

@@ -0,0 +1,45 @@
+/* GLIB - Library of useful routines for C programming
+ *
+ * Copyright (C) 2020 Red Hat, Inc.
+ *
+ * Author: Jakub Jelen <jjelen@redhat.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General
+ * Public License along with this library; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <dlfcn.h>
+#include <pwd.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+static struct passwd my_pw;
+
+/* This is used in gutils.c used to make sure utility functions
+ * handling user information do not crash on bad data (for example
+ * caused by getpwuid returning some NULL elements.
+ */
+struct passwd *
+getpwuid (uid_t uid)
+{
+  static struct passwd *(*real_getpwuid) (uid_t);
+  struct passwd *pw;
+
+  if (real_getpwuid == NULL)
+    real_getpwuid = dlsym (RTLD_NEXT, "getpwuid");
+
+  pw = real_getpwuid (uid);
+  my_pw = *pw;
+  my_pw.pw_name = NULL;
+  return &my_pw;
+}

glib/tests/gutils-user-database.c

@@ -0,0 +1,43 @@
+/*
+ * Copyright © 2020 Red Hat, Inc.
+ *
+ * Author: Jakub Jelen <jjelen@redhat.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * See the included COPYING file for more information.
+ */
+
+#include <glib.h>
+
+/* The function g_get_user_database_entry() is called from the
+ * g_get_real_name(), g_get_user_name() and g_build_home_dir()
+ * functions. These two calls are here just to invoke the code
+ * paths. The real-test is the ld_preload used to inject the
+ * NULL in place of pw->pw_name.
+ */
+static void
+test_get_user_database_entry (void)
+{
+  const gchar *r = NULL;
+
+  r = g_get_user_name ();
+  g_assert_nonnull (r);
+
+  r = g_get_real_name ();
+  g_assert_nonnull (r);
+}
+
+int
+main (int argc, char *argv[])
+{
+  g_test_init (&argc, &argv, NULL);
+  g_test_bug_base ("https://gitlab.gnome.org/GNOME/glib/issues");
+
+  g_test_add_func ("/gutils/get_user_database_entry", test_get_user_database_entry);
+
+  return g_test_run ();
+}

glib/tests/meson.build

@@ -148,6 +148,27 @@ else
     'include' : {},
     'unix' : {},
   }
+  if have_rtld_next
+    glib_tests += {
+      'gutils-user-database' : {
+        'depends' : [
+          shared_library('getpwuid-preload',
+            'getpwuid-preload.c',
+            name_prefix : '',
+            dependencies: libdl_dep,
+            install_dir : installed_tests_execdir,
+            install: installed_tests_enabled,
+          ),
+        ],
+        'env' : {
+          'LD_PRELOAD': '@0@/getpwuid-preload.so'.format(meson.current_build_dir()),
+        },
+        'installed_tests_env' : {
+          'LD_PRELOAD': '@0@/getpwuid-preload.so'.format(installed_tests_execdir),
+        },
+      },
+    }
+  endif
 endif
 
 if installed_tests_enabled