nss: fix nss_database_lookup2's alternate handling [BZ #27416]

__nss_database_lookup2's extra arguments were left unused in the
nsswitch reloading patch set; this broke compat (default config
ignored) and shadow files (secondary name ignored) which relies on
these fallbacks.

This patch adds in the previous behavior by correcting the
initialization of the database list to reflect the fallbacks.  This
means that the nss_database_lookup2 interface no longer needs to be
passed the fallback info, so API and callers were adjusted.

Since all callers needed to be edited anyway, the calls were changed
from __nss_database_lookup2 to the faster __nss_database_get.  This
was an intended optimization which was deferred during the initial
lookup changes to avoid touching so many files.

The test case verifies that compat targets work (passwd) and that the
default configuration works (group).  Tested on x86-64.

1 files changed, 81 insertions, 0 deletions

diff --git a/nss/tst-nss-compat1.c b/nss/tst-nss-compat1.c
new file mode 100644
index 0000000000..670cffe538
--- /dev/null
+++ b/nss/tst-nss-compat1.c
@@ -0,0 +1,81 @@
+/* Test error checking for group entries.
+   Copyright (C) 2021 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C 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.
+
+   The GNU C 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 the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <nss.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <shadow.h>
+
+#include <support/support.h>
+#include <support/check.h>
+
+#include "nss_test.h"
+
+static struct passwd pwd_table[] = {
+    PWD (100),
+    PWD (30),
+    PWD_LAST ()
+  };
+
+static struct spwd spwd_table[] = {
+    SPWD (100),
+    SPWD (30),
+    SPWD_LAST ()
+  };
+
+void
+_nss_test1_init_hook(test_tables *t)
+{
+  t->pwd_table = pwd_table;
+  t->spwd_table = spwd_table;
+}
+
+static int
+do_test (void)
+{
+  struct passwd *p = NULL;
+  struct spwd *s = NULL;
+  struct group *g = NULL;
+
+  /* Test that compat-to-test works.  */
+  p = getpwuid (100);
+  if (p == NULL)
+    FAIL_EXIT1("getpwuid-compat-test1 p");
+  else if (strcmp (p->pw_name, "name100") != 0)
+    FAIL_EXIT1("getpwuid-compat-test1 name100");
+
+  /* Shadow compat should use passwd via the alternate name.  */
+  s = getspnam ("name30");
+  if (s == NULL)
+    FAIL_EXIT1("getspnam-compat-test1 s");
+  else if (strcmp (s->sp_namp, "name30") != 0)
+    FAIL_EXIT1("getpwuid-compat-test1 name30");
+
+  /* Test that internal defconfig works.  */
+  g = getgrgid (100);
+  if (g == NULL)
+    FAIL_EXIT1("getgrgid-compat-null");
+  if (strcmp (g->gr_name, "wilma") != 0)
+    FAIL_EXIT1("getgrgid-compat-name");
+
+  return 0;
+}
+
+#include <support/test-driver.c>