diff mbox series

[v4] nss: fix nss_database_lookup2's alternate handling [BZ #27416]

Message ID xn8s71t6h0.fsf@rhel8.vm
State Superseded
Headers show
Series [v4] nss: fix nss_database_lookup2's alternate handling [BZ #27416] | expand

Commit Message

DJ Delorie March 6, 2021, 1:29 a.m. UTC
__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.
---
 nscd/aicache.c                                |  4 +-
 nscd/initgrcache.c                            |  3 +-
 nscd/netgroupcache.c                          |  2 +-
 nss/Makefile                                  |  1 +
 nss/Versions                                  |  2 +-
 nss/XXX-lookup.c                              | 17 +---
 nss/databases.def                             |  3 +
 nss/grp-lookup.c                              |  1 -
 nss/hosts-lookup.c                            |  1 -
 nss/key-lookup.c                              |  1 -
 nss/network-lookup.c                          |  1 -
 nss/nss_compat/compat-grp.c                   |  2 +-
 nss/nss_compat/compat-initgroups.c            |  2 +-
 nss/nss_compat/compat-pwd.c                   |  2 +-
 nss/nss_compat/compat-spwd.c                  |  3 +-
 nss/nss_database.c                            | 35 ++++++-
 nss/nss_database.h                            |  5 +-
 nss/nss_module.c                              | 20 ++--
 nss/nss_test.h                                |  7 ++
 nss/nss_test1.c                               | 93 +++++++++++++++++++
 nss/nsswitch.c                                | 25 +----
 nss/nsswitch.h                                |  7 +-
 nss/pwd-lookup.c                              |  1 -
 nss/sgrp-lookup.c                             |  2 -
 nss/spwd-lookup.c                             |  2 -
 nss/tst-nss-compat1.c                         | 81 ++++++++++++++++
 nss/tst-nss-compat1.root/etc/group            |  1 +
 nss/tst-nss-compat1.root/etc/nsswitch.conf    |  3 +
 nss/tst-nss-compat1.root/etc/passwd           |  3 +
 nss/tst-nss-compat1.root/etc/shadow           |  2 +
 .../tst-nss-compat1.script                    |  1 +
 sysdeps/posix/getaddrinfo.c                   |  4 +-
 32 files changed, 256 insertions(+), 81 deletions(-)
 create mode 100644 nss/tst-nss-compat1.c
 create mode 100644 nss/tst-nss-compat1.root/etc/group
 create mode 100644 nss/tst-nss-compat1.root/etc/nsswitch.conf
 create mode 100644 nss/tst-nss-compat1.root/etc/passwd
 create mode 100644 nss/tst-nss-compat1.root/etc/shadow
 create mode 100644 nss/tst-nss-compat1.root/tst-nss-compat1.script

Comments

Andreas Schwab March 8, 2021, 11:23 a.m. UTC | #1
On Mär 05 2021, DJ Delorie via Libc-alpha wrote:

> 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.

There are no callers of __nss_database_lookup2 left.

Andreas.
diff mbox series

Patch

diff --git a/nscd/aicache.c b/nscd/aicache.c
index 1b4245ea53..38ef804fb1 100644
--- a/nscd/aicache.c
+++ b/nscd/aicache.c
@@ -77,9 +77,7 @@  addhstaiX (struct database_dyn *db, int fd, request_header *req,
   int rc4 = 0;
   int herrno = 0;
 
-  no_more = __nss_database_lookup2 ("hosts", NULL,
-				    "dns [!UNAVAIL=return] files",
-				    &nip);
+  no_more = (__nss_database_get (nss_database_hosts, &nip) == false);
 
   /* Initialize configurations.  */
   struct resolv_context *ctx = __resolv_context_get ();
diff --git a/nscd/initgrcache.c b/nscd/initgrcache.c
index f7e326811f..1c562d7dd3 100644
--- a/nscd/initgrcache.c
+++ b/nscd/initgrcache.c
@@ -82,8 +82,7 @@  addinitgroupsX (struct database_dyn *db, int fd, request_header *req,
   int no_more;
 
   if (group_database == NULL)
-    no_more = __nss_database_lookup2 ("group", NULL, "files",
-				      &group_database);
+    no_more = (__nss_database_get (nss_database_group, &group_database) == false);
   else
     no_more = 0;
   nip = group_database;
diff --git a/nscd/netgroupcache.c b/nscd/netgroupcache.c
index ad2daddafd..2f71bf2999 100644
--- a/nscd/netgroupcache.c
+++ b/nscd/netgroupcache.c
@@ -143,7 +143,7 @@  addgetnetgrentX (struct database_dyn *db, int fd, request_header *req,
   *tofreep = NULL;
 
   if (netgroup_database == NULL
-      && __nss_database_lookup2 ("netgroup", NULL, NULL, &netgroup_database))
+      && !__nss_database_get (nss_database_netgroup, &netgroup_database))
     {
       /* No such service.  */
       cacheable = do_notfound (db, fd, req, key, &dataset, &total, &timeout,
diff --git a/nss/Makefile b/nss/Makefile
index 0906202db9..71fbe583bf 100644
--- a/nss/Makefile
+++ b/nss/Makefile
@@ -63,6 +63,7 @@  tests			= test-netdb test-digits-dots tst-nss-getpwent bug17079 \
 xtests			= bug-erange
 
 tests-container = \
+			  tst-nss-compat1 \
 			  tst-nss-test3 \
 			  tst-nss-files-hosts-long \
 			  tst-nss-db-endpwent \
diff --git a/nss/Versions b/nss/Versions
index 71703750bf..9351a38870 100644
--- a/nss/Versions
+++ b/nss/Versions
@@ -17,7 +17,7 @@  libc {
 
     __nss_passwd_lookup2; __nss_group_lookup2; __nss_hosts_lookup2;
     __nss_services_lookup2; __nss_next2; __nss_lookup;
-    __nss_hash; __nss_database_lookup2;
+    __nss_hash; __nss_database_lookup2; __nss_database_get;
     __nss_files_fopen; __nss_readline; __nss_parse_line_result;
   }
 }
diff --git a/nss/XXX-lookup.c b/nss/XXX-lookup.c
index 48fc7b92fc..f1c97f7c8e 100644
--- a/nss/XXX-lookup.c
+++ b/nss/XXX-lookup.c
@@ -37,27 +37,20 @@ 
 #define CONCAT3_1(Pre, Name, Post) CONCAT3_2 (Pre, Name, Post)
 #define CONCAT3_2(Pre, Name, Post) Pre##Name##Post
 
+#define DATABASE_NAME_ID CONCAT2_1 (nss_database_, DATABASE_NAME)
+#define CONCAT2_1(Pre, Name) CONCAT2_2 (Pre, Name)
+#define CONCAT2_2(Pre, Name) Pre##Name
+
 #define DATABASE_NAME_SYMBOL CONCAT3_1 (__nss_, DATABASE_NAME, _database)
 #define DATABASE_NAME_STRING STRINGIFY1 (DATABASE_NAME)
 #define STRINGIFY1(Name) STRINGIFY2 (Name)
 #define STRINGIFY2(Name) #Name
 
-#ifdef ALTERNATE_NAME
-#define ALTERNATE_NAME_STRING STRINGIFY1 (ALTERNATE_NAME)
-#else
-#define ALTERNATE_NAME_STRING NULL
-#endif
-
-#ifndef DEFAULT_CONFIG
-#define DEFAULT_CONFIG NULL
-#endif
-
 int
 DB_LOOKUP_FCT (nss_action_list *ni, const char *fct_name, const char *fct2_name,
 	       void **fctp)
 {
-  if (__nss_database_lookup2 (DATABASE_NAME_STRING, ALTERNATE_NAME_STRING,
-			      DEFAULT_CONFIG, &DATABASE_NAME_SYMBOL) < 0)
+  if (! __nss_database_get (DATABASE_NAME_ID, &DATABASE_NAME_SYMBOL))
     return -1;
 
   *ni = DATABASE_NAME_SYMBOL;
diff --git a/nss/databases.def b/nss/databases.def
index df5fab4168..3dc95648a8 100644
--- a/nss/databases.def
+++ b/nss/databases.def
@@ -23,17 +23,20 @@ 
 DEFINE_DATABASE (aliases)
 DEFINE_DATABASE (ethers)
 DEFINE_DATABASE (group)
+DEFINE_DATABASE (group_compat)
 DEFINE_DATABASE (gshadow)
 DEFINE_DATABASE (hosts)
 DEFINE_DATABASE (initgroups)
 DEFINE_DATABASE (netgroup)
 DEFINE_DATABASE (networks)
 DEFINE_DATABASE (passwd)
+DEFINE_DATABASE (passwd_compat)
 DEFINE_DATABASE (protocols)
 DEFINE_DATABASE (publickey)
 DEFINE_DATABASE (rpc)
 DEFINE_DATABASE (services)
 DEFINE_DATABASE (shadow)
+DEFINE_DATABASE (shadow_compat)
 
 /*
    Local Variables:
diff --git a/nss/grp-lookup.c b/nss/grp-lookup.c
index 7099544be5..034fa2ab7f 100644
--- a/nss/grp-lookup.c
+++ b/nss/grp-lookup.c
@@ -19,6 +19,5 @@ 
 #include <config.h>
 
 #define DATABASE_NAME group
-#define DEFAULT_CONFIG "files"
 
 #include "XXX-lookup.c"
diff --git a/nss/hosts-lookup.c b/nss/hosts-lookup.c
index c96b60ed66..1acafd01cd 100644
--- a/nss/hosts-lookup.c
+++ b/nss/hosts-lookup.c
@@ -17,6 +17,5 @@ 
    <https://www.gnu.org/licenses/>.  */
 
 #define DATABASE_NAME hosts
-#define DEFAULT_CONFIG "dns [!UNAVAIL=return] files"
 
 #include "XXX-lookup.c"
diff --git a/nss/key-lookup.c b/nss/key-lookup.c
index 60d803ded5..aa267d36f9 100644
--- a/nss/key-lookup.c
+++ b/nss/key-lookup.c
@@ -17,6 +17,5 @@ 
    <https://www.gnu.org/licenses/>.  */
 
 #define DATABASE_NAME publickey
-#define DEFAULT_CONFIG "nis nisplus"
 
 #include "XXX-lookup.c"
diff --git a/nss/network-lookup.c b/nss/network-lookup.c
index 8c1eeb3c84..eed4dc3d0f 100644
--- a/nss/network-lookup.c
+++ b/nss/network-lookup.c
@@ -17,6 +17,5 @@ 
    <https://www.gnu.org/licenses/>.  */
 
 #define DATABASE_NAME networks
-#define DEFAULT_CONFIG "dns [!UNAVAIL=return] files"
 
 #include "XXX-lookup.c"
diff --git a/nss/nss_compat/compat-grp.c b/nss/nss_compat/compat-grp.c
index eb4c68d5d4..aaf35e75b4 100644
--- a/nss/nss_compat/compat-grp.c
+++ b/nss/nss_compat/compat-grp.c
@@ -81,7 +81,7 @@  static bool in_blacklist (const char *, int, ent_t *);
 static void
 init_nss_interface (void)
 {
-  if (__nss_database_lookup2 ("group_compat", NULL, "nis", &ni) >= 0)
+  if (__nss_database_get (nss_database_group_compat, &ni))
     {
       setgrent_impl = __nss_lookup_function (ni, "setgrent");
       getgrnam_r_impl = __nss_lookup_function (ni, "getgrnam_r");
diff --git a/nss/nss_compat/compat-initgroups.c b/nss/nss_compat/compat-initgroups.c
index cfd36b64b8..c3b065c931 100644
--- a/nss/nss_compat/compat-initgroups.c
+++ b/nss/nss_compat/compat-initgroups.c
@@ -91,7 +91,7 @@  init_nss_interface (void)
 
   /* Retest.  */
   if (ni == NULL
-      && __nss_database_lookup2 ("group_compat", NULL, "nis", &ni) >= 0)
+      && __nss_database_get (nss_database_group_compat, &ni))
     {
       initgroups_dyn_impl = __nss_lookup_function (ni, "initgroups_dyn");
       getgrnam_r_impl = __nss_lookup_function (ni, "getgrnam_r");
diff --git a/nss/nss_compat/compat-pwd.c b/nss/nss_compat/compat-pwd.c
index f536754559..64d708ff63 100644
--- a/nss/nss_compat/compat-pwd.c
+++ b/nss/nss_compat/compat-pwd.c
@@ -91,7 +91,7 @@  static bool in_blacklist (const char *, int, ent_t *);
 static void
 init_nss_interface (void)
 {
-  if (__nss_database_lookup2 ("passwd_compat", NULL, "nis", &ni) >= 0)
+  if (__nss_database_get (nss_database_passwd_compat, &ni))
     {
       setpwent_impl = __nss_lookup_function (ni, "setpwent");
       getpwnam_r_impl = __nss_lookup_function (ni, "getpwnam_r");
diff --git a/nss/nss_compat/compat-spwd.c b/nss/nss_compat/compat-spwd.c
index 5c91f9572a..b548dfbee1 100644
--- a/nss/nss_compat/compat-spwd.c
+++ b/nss/nss_compat/compat-spwd.c
@@ -88,8 +88,7 @@  static bool in_blacklist (const char *, int, ent_t *);
 static void
 init_nss_interface (void)
 {
-  if (__nss_database_lookup2 ("shadow_compat", "passwd_compat",
-			      "nis", &ni) >= 0)
+  if (__nss_database_get (nss_database_shadow_compat, &ni))
     {
       setspent_impl = __nss_lookup_function (ni, "setspent");
       getspnam_r_impl = __nss_lookup_function (ni, "getspnam_r");
diff --git a/nss/nss_database.c b/nss/nss_database.c
index fb72d0cc03..6e9b36a1eb 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 +325,40 @@  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.  */
+
+      /* was  lookup2() in nss/nss_compat/compat-spwd.c */
+      if (staging->services[nss_database_shadow_compat] == NULL)
+	staging->services[nss_database_shadow_compat] =
+	  staging->services[nss_database_passwd_compat];
+
+      /* was ALTERNATE_NAME in nss/spwd_lookup.c */
+      if (staging->services[nss_database_shadow] == NULL)
+	staging->services[nss_database_shadow] =
+	  staging->services[nss_database_passwd];
+
+      /* was ALTERNATE_NAME in nss/sgrp_lookup.c */
+      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 +468,7 @@  __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)
diff --git a/nss/nss_database.h b/nss/nss_database.h
index 1f827e6def..d4b23b5295 100644
--- a/nss/nss_database.h
+++ b/nss/nss_database.h
@@ -52,12 +52,11 @@  enum nss_database
   NSS_DATABASE_COUNT
 };
 
-
 /* Looks up the action list for DB and stores it in *ACTIONS.  Returns
    true on success or false on failure.  Success can mean that
    *ACTIONS is NULL.  */
-bool __nss_database_get (enum nss_database db, nss_action_list *actions)
-  attribute_hidden;
+bool __nss_database_get (enum nss_database db, nss_action_list *actions);
+libc_hidden_proto (__nss_database_get)
 
 /* Like __nss_database_get, but does not reload /etc/nsswitch.conf
    from disk.  This assumes that there has been a previous successful
diff --git a/nss/nss_module.c b/nss/nss_module.c
index 6c5f341f3e..60c070c851 100644
--- a/nss/nss_module.c
+++ b/nss/nss_module.c
@@ -31,14 +31,6 @@ 
 #include <stdlib.h>
 #include <string.h>
 
-#ifdef LINK_OBSOLETE_NSL
-# define DEFAULT_CONFIG    "compat [NOTFOUND=return] files"
-# define DEFAULT_DEFCONFIG "nis [NOTFOUND=return] files"
-#else
-# define DEFAULT_CONFIG    "files"
-# define DEFAULT_DEFCONFIG "files"
-#endif
-
 /* Suffix after .so of NSS service modules.  This is a bit of magic,
    but we assume LIBNSS_FILES_SO looks like "libnss_files.so.2" and we
    want a pointer to the ".2" part.  We have no API to extract this
@@ -292,11 +284,11 @@  __nss_module_get_function (struct nss_module *module, const char *name)
 #if defined SHARED && defined USE_NSCD
 /* Load all libraries for the service.  */
 static void
-nss_load_all_libraries (const char *service, const char *def)
+nss_load_all_libraries (enum nss_database service)
 {
   nss_action_list ni = NULL;
 
-  if (__nss_database_lookup2 (service, NULL, def, &ni) == 0)
+  if (__nss_database_get (service, &ni))
     while (ni->module != NULL)
       {
         __nss_module_load (ni->module);
@@ -323,10 +315,10 @@  __nss_disable_nscd (void (*cb) (size_t, struct traced_file *))
   is_nscd = true;
 
   /* Find all the relevant modules so that the init functions are called.  */
-  nss_load_all_libraries ("passwd", DEFAULT_CONFIG);
-  nss_load_all_libraries ("group", DEFAULT_CONFIG);
-  nss_load_all_libraries ("hosts", "dns [!UNAVAIL=return] files");
-  nss_load_all_libraries ("services", NULL);
+  nss_load_all_libraries (nss_database_passwd);
+  nss_load_all_libraries (nss_database_group);
+  nss_load_all_libraries (nss_database_hosts);
+  nss_load_all_libraries (nss_database_services);
 
   /* Make sure NSCD purges its cache if nsswitch.conf changes.  */
   init_traced_file (&pwd_traced_file.file, _PATH_NSSWITCH_CONF, 0);
diff --git a/nss/nss_test.h b/nss/nss_test.h
index f8b81c27a7..db3d617585 100644
--- a/nss/nss_test.h
+++ b/nss/nss_test.h
@@ -33,11 +33,13 @@ 
 
 #include <pwd.h>
 #include <grp.h>
+#include <shadow.h>
 #include <netdb.h>
 
 typedef struct test_tables {
   struct passwd *pwd_table;
   struct group *grp_table;
+  struct spwd *spwd_table;
   struct hostent *host_table;
 } test_tables;
 
@@ -46,10 +48,12 @@  extern void _nss_test2_init_hook (test_tables *) __attribute__((weak));
 
 #define PWD_LAST()    { .pw_name = NULL, .pw_uid = 0 }
 #define GRP_LAST()    { .gr_name = NULL, .gr_gid = 0 }
+#define SPWD_LAST()    { .sp_namp = NULL, .sp_pwdp = NULL }
 #define HOST_LAST()    { .h_name = NULL, .h_aliases = NULL, .h_length = 0, .h_addr_list = NULL }
 
 #define PWD_ISLAST(p)    ((p)->pw_name == NULL && (p)->pw_uid == 0)
 #define GRP_ISLAST(g)    ((g)->gr_name == NULL && (g)->gr_gid == 0)
+#define SPWD_ISLAST(s)    ((s)->sp_namp == NULL && (s)->sp_pwdp == 0)
 #define HOST_ISLAST(h)    ((h)->h_name == NULL && (h)->h_length == 0)
 
 /* Macros to fill in the tables easily.  */
@@ -76,6 +80,9 @@  extern void _nss_test2_init_hook (test_tables *) __attribute__((weak));
     { .gr_name = (char *) n, .gr_passwd = (char *) "*", .gr_gid = u, \
       .gr_mem = (char **) m }
 
+#define SPWD(u) \
+    { .sp_namp = (char *) "name" #u, .sp_pwdp = (char *) "passwd" #u }
+
 #define HOST(u)								\
     { .h_name = (char *) "name" #u, .h_aliases = NULL, .h_addrtype = u,	\
       .h_length = 4,							\
diff --git a/nss/nss_test1.c b/nss/nss_test1.c
index f73c7a6cd8..f8d81831ee 100644
--- a/nss/nss_test1.c
+++ b/nss/nss_test1.c
@@ -66,6 +66,9 @@  static int npwd_data = default_npwd_data;
 static struct group *grp_data = NULL;
 static int ngrp_data = 0;
 
+static struct spwd *spwd_data = NULL;
+static int nspwd_data = 0;
+
 static struct hostent *host_data = NULL;
 static int nhost_data = 0;
 
@@ -102,6 +105,13 @@  init(void)
 	    ;
 	  ngrp_data = i;
 	}
+      if (t.spwd_table)
+	{
+	  spwd_data = t.spwd_table;
+	  for (i=0; ! SPWD_ISLAST(& spwd_data[i]); i++)
+	    ;
+	  nspwd_data = i;
+	}
       if (t.host_table)
 	{
 	  host_data = t.host_table;
@@ -323,6 +333,89 @@  NAME(getgrnam_r) (const char *name, struct group *result, char *buffer,
   return NSS_STATUS_NOTFOUND;
 }
 
+/* -------------------------------------------------- */
+/* Shadow password handling.  */
+
+static size_t spwd_iter;
+#define CURSPWD spwd_data[spwd_iter]
+
+static pthread_mutex_t spwd_lock = PTHREAD_MUTEX_INITIALIZER;
+
+enum nss_status
+NAME(setspent) (int stayopen)
+{
+  init();
+  spwd_iter = 0;
+  return NSS_STATUS_SUCCESS;
+}
+
+
+enum nss_status
+NAME(endspwent) (void)
+{
+  init();
+  return NSS_STATUS_SUCCESS;
+}
+
+static enum nss_status
+copy_shadow (struct spwd *result, struct spwd *local,
+	    char *buffer, size_t buflen, int *errnop)
+{
+  struct alloc_buffer buf = alloc_buffer_create (buffer, buflen);
+
+  result->sp_namp = alloc_buffer_maybe_copy_string (&buf, local->sp_namp);
+  result->sp_pwdp = alloc_buffer_maybe_copy_string (&buf, local->sp_pwdp);
+  result->sp_lstchg = local->sp_lstchg;
+  result->sp_min = local->sp_min;
+  result->sp_max = local->sp_max;
+  result->sp_warn = local->sp_warn;
+  result->sp_inact = local->sp_inact;
+  result->sp_expire = local->sp_expire;
+  result->sp_flag = local->sp_flag;
+
+  if (alloc_buffer_has_failed (&buf))
+    {
+      *errnop = ERANGE;
+      return NSS_STATUS_TRYAGAIN;
+    }
+
+  return NSS_STATUS_SUCCESS;
+}
+
+enum nss_status
+NAME(getspent_r) (struct spwd *result, char *buffer, size_t buflen,
+		  int *errnop)
+{
+  int res = NSS_STATUS_SUCCESS;
+
+  init();
+  pthread_mutex_lock (&spwd_lock);
+
+  if (spwd_iter >= nspwd_data)
+    res = NSS_STATUS_NOTFOUND;
+  else
+    {
+      res = copy_shadow (result, &CURSPWD, buffer, buflen, errnop);
+      ++spwd_iter;
+    }
+
+  pthread_mutex_unlock (&spwd_lock);
+
+  return res;
+}
+
+enum nss_status
+NAME(getspnam_r) (const char *name, struct spwd *result, char *buffer,
+		  size_t buflen, int *errnop)
+{
+  init();
+  for (size_t idx = 0; idx < nspwd_data; ++idx)
+    if (strcmp (spwd_data[idx].sp_namp, name) == 0)
+      return copy_shadow (result, &spwd_data[idx], buffer, buflen, errnop);
+
+  return NSS_STATUS_NOTFOUND;
+}
+
 /* -------------------------------------------------- */
 /* Host handling.  */
 
diff --git a/nss/nsswitch.c b/nss/nsswitch.c
index 46f232d720..076c0f12c4 100644
--- a/nss/nsswitch.c
+++ b/nss/nsswitch.c
@@ -63,37 +63,22 @@  static const char * database_names[] = {
 bool __nss_database_custom[NSS_DBSIDX_max];
 #endif
 
-
 /*__libc_lock_define_initialized (static, lock)*/
 
 /* -1 == database not found
     0 == database entry pointer stored */
 int
-__nss_database_lookup2 (const char *database, const char *alternate_name,
-			const char *defconfig, nss_action_list *ni)
+__nss_database_lookup2 (const char *database, nss_action_list *ni)
 {
   int database_id;
 
   for (database_id = 0; database_names[database_id]; database_id++)
     if (strcmp (database_names[database_id], database) == 0)
-	break;
-
-  if (database_names[database_id] == NULL)
-    return -1;
+      if (__nss_database_get (database_id, ni))
+	return 0;
 
-  /* If *NI is NULL, the database was not mentioned in nsswitch.conf.
-     If *NI is not NULL, but *NI->module is NULL, the database was in
-     nsswitch.conf but listed no actions.  We test for the former.  */
-  if (__nss_database_get (database_id, ni) && *ni != NULL)
-    {
-      /* Success.  */
-      return 0;
-    }
-  else
-    {
-      /* Failure.  */
-      return -1;
-    }
+  /* Failure.  */
+  return -1;
 }
 libc_hidden_def (__nss_database_lookup2)
 
diff --git a/nss/nsswitch.h b/nss/nsswitch.h
index c483bbd891..af2e2faf7e 100644
--- a/nss/nsswitch.h
+++ b/nss/nsswitch.h
@@ -88,13 +88,10 @@  extern bool __nss_database_custom[NSS_DBSIDX_max] attribute_hidden;
 
 /* Interface functions for NSS.  */
 
-/* Get the data structure representing the specified database.
-   If there is no configuration for this database in the file,
-   parse a service list from DEFCONFIG and use that.  More
+/* Get the data structure representing the specified database.  More
    than one function can use the database.  */
 extern int __nss_database_lookup2 (const char *database,
-				   const char *alternative_name,
-				   const char *defconfig, struct nss_action **ni);
+				   struct nss_action **ni);
 libc_hidden_proto (__nss_database_lookup2)
 
 /* Put first function with name FCT_NAME for SERVICE in FCTP.  The
diff --git a/nss/pwd-lookup.c b/nss/pwd-lookup.c
index 4f5c47422f..5ec8a8b485 100644
--- a/nss/pwd-lookup.c
+++ b/nss/pwd-lookup.c
@@ -19,6 +19,5 @@ 
 #include <config.h>
 
 #define DATABASE_NAME passwd
-#define DEFAULT_CONFIG "files"
 
 #include "XXX-lookup.c"
diff --git a/nss/sgrp-lookup.c b/nss/sgrp-lookup.c
index 6df4c49ff1..9a2becc202 100644
--- a/nss/sgrp-lookup.c
+++ b/nss/sgrp-lookup.c
@@ -17,7 +17,5 @@ 
    <https://www.gnu.org/licenses/>.  */
 
 #define DATABASE_NAME gshadow
-#define ALTERNATE_NAME group
-#define DEFAULT_CONFIG "files"
 
 #include "XXX-lookup.c"
diff --git a/nss/spwd-lookup.c b/nss/spwd-lookup.c
index e3c8c1df7b..e9e661af12 100644
--- a/nss/spwd-lookup.c
+++ b/nss/spwd-lookup.c
@@ -19,7 +19,5 @@ 
 #include <config.h>
 
 #define DATABASE_NAME shadow
-#define ALTERNATE_NAME passwd
-#define DEFAULT_CONFIG "files"
 
 #include "XXX-lookup.c"
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>
diff --git a/nss/tst-nss-compat1.root/etc/group b/nss/tst-nss-compat1.root/etc/group
new file mode 100644
index 0000000000..ee467c7950
--- /dev/null
+++ b/nss/tst-nss-compat1.root/etc/group
@@ -0,0 +1 @@ 
+wilma:x:100:
diff --git a/nss/tst-nss-compat1.root/etc/nsswitch.conf b/nss/tst-nss-compat1.root/etc/nsswitch.conf
new file mode 100644
index 0000000000..7fe69d5ffa
--- /dev/null
+++ b/nss/tst-nss-compat1.root/etc/nsswitch.conf
@@ -0,0 +1,3 @@ 
+passwd : compat
+passwd_compat : test1
+
diff --git a/nss/tst-nss-compat1.root/etc/passwd b/nss/tst-nss-compat1.root/etc/passwd
new file mode 100644
index 0000000000..84635587bd
--- /dev/null
+++ b/nss/tst-nss-compat1.root/etc/passwd
@@ -0,0 +1,3 @@ 
+name5:x:5:555:name5 for testing:/home/name5:/bin/nologin
++name100
++name30
diff --git a/nss/tst-nss-compat1.root/etc/shadow b/nss/tst-nss-compat1.root/etc/shadow
new file mode 100644
index 0000000000..cba3152172
--- /dev/null
+++ b/nss/tst-nss-compat1.root/etc/shadow
@@ -0,0 +1,2 @@ 
++name100
++name30
diff --git a/nss/tst-nss-compat1.root/tst-nss-compat1.script b/nss/tst-nss-compat1.root/tst-nss-compat1.script
new file mode 100644
index 0000000000..fe6e863f01
--- /dev/null
+++ b/nss/tst-nss-compat1.root/tst-nss-compat1.script
@@ -0,0 +1 @@ 
+cp $B/nss/libnss_test1.so $L/libnss_test1.so.2
diff --git a/sysdeps/posix/getaddrinfo.c b/sysdeps/posix/getaddrinfo.c
index 92d2a1c284..5357b5a873 100644
--- a/sysdeps/posix/getaddrinfo.c
+++ b/sysdeps/posix/getaddrinfo.c
@@ -720,9 +720,7 @@  gaih_inet (const char *name, const struct gaih_service *service,
 	    }
 #endif
 
-	  no_more = __nss_database_lookup2 ("hosts", NULL,
-					    "dns [!UNAVAIL=return] files",
-					    &nip);
+	  no_more = (__nss_database_get (nss_database_hosts, &nip) == false);
 
 	  /* If we are looking for both IPv4 and IPv6 address we don't
 	     want the lookup functions to automatically promote IPv4