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, 35 insertions, 3 deletions

diff --git a/nss/nss_database.c b/nss/nss_database.c
index fb72d0cc03..1e11294406 100644
--- a/nss/nss_database.c
+++ b/nss/nss_database.c
@@ -93,13 +93,16 @@ enum nss_database_default
 static const char per_database_defaults[NSS_DATABASE_COUNT] =
   {
    [nss_database_group] = nss_database_default_compat,
+   [nss_database_group_compat] = nss_database_default_nis,
    [nss_database_gshadow] = nss_database_default_files,
    [nss_database_hosts] = nss_database_default_dns,
    [nss_database_initgroups] = nss_database_default_none,
    [nss_database_networks] = nss_database_default_dns,
    [nss_database_passwd] = nss_database_default_compat,
+   [nss_database_passwd_compat] = nss_database_default_nis,
    [nss_database_publickey] = nss_database_default_nis_nisplus,
    [nss_database_shadow] = nss_database_default_compat,
+   [nss_database_shadow_compat] = nss_database_default_nis,
   };
 
 struct nss_database_default_cache
@@ -166,13 +169,12 @@ nss_database_select_default (struct nss_database_default_cache *cache,
       assert (errno == ENOMEM);
       return false;
     }
-  else
-    return true;
+  return true;
 }
 
 /* database_name must be large enough for each individual name plus a
    null terminator.  */
-typedef char database_name[11];
+typedef char database_name[14];
 #define DEFINE_DATABASE(name) \
   _Static_assert (sizeof (#name) <= sizeof (database_name), #name);
 #include "databases.def"
@@ -323,14 +325,43 @@ nss_database_reload (struct nss_database_data *staging,
     /* No other threads have access to fp.  */
     __fsetlocking (fp, FSETLOCKING_BYCALLER);
 
+  /* We start with all of *staging pointing to NULL.  */
+
   bool ok = true;
   if (fp != NULL)
     ok = nss_database_reload_1 (staging, fp);
 
+  /* Now we have non-NULL entries where the user explictly listed the
+     service in nsswitch.conf.  */
+
   /* Apply defaults.  */
   if (ok)
     {
       struct nss_database_default_cache cache = { };
+
+      /* These three default to other services if the user listed the
+	 other service.  */
+
+      /* "shadow_compat" defaults to "passwd_compat" if only the
+	 latter is given.  */
+      if (staging->services[nss_database_shadow_compat] == NULL)
+	staging->services[nss_database_shadow_compat] =
+	  staging->services[nss_database_passwd_compat];
+
+      /* "shadow" defaults to "passwd" if only the latter is
+	 given.  */
+      if (staging->services[nss_database_shadow] == NULL)
+	staging->services[nss_database_shadow] =
+	  staging->services[nss_database_passwd];
+
+      /* "gshadow" defaults to "group" if only the latter is
+	 given.  */
+      if (staging->services[nss_database_gshadow] == NULL)
+	staging->services[nss_database_gshadow] =
+	  staging->services[nss_database_group];
+
+      /* For anything still unspecified, load the default configs.  */
+
       for (int i = 0; i < NSS_DATABASE_COUNT; ++i)
         if (staging->services[i] == NULL)
           {
@@ -440,6 +471,7 @@ __nss_database_get (enum nss_database db, nss_action_list *actions)
   struct nss_database_state *local = nss_database_state_get ();
   return nss_database_check_reload_and_get (local, actions, db);
 }
+libc_hidden_def (__nss_database_get)
 
 nss_action_list
 __nss_database_get_noreload (enum nss_database db)