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Subject: nsswitch: Add group merging support

From: Stephen Gallagher <sgallagh@redhat.com>

X-Patchwork-Id: 10289

Message-Id: <1452213991-6499-1-git-send-email-sgallagh@redhat.com>

To: libc-alpha@sourceware.org

Date: Thu,  7 Jan 2016 19:46:31 -0500

https://sourceware.org/glibc/wiki/Proposals/GroupMerging

== Justification ==

It is common today for users to rely on centrally-managed user stores for

handling their user accounts. However, much software existing today does

not have an innate understanding of such accounts. Instead, they commonly

rely on membership in known groups for managing access-control (for

example the "wheel" group on Fedora and RHEL systems or the "adm" group

on Debian-derived systems). In the present incarnation of nsswitch, the

only way to have such groups managed by a remote user store such as

FreeIPA or Active Directory would be to manually remove the groups from

/etc/group on the clients so that nsswitch would then move past nss_files

and into the SSSD, nss-ldap or other remote user database.

== Solution ==

With this patch, a new action is introduced for nsswitch:

NSS_ACTION_MERGE. To take advantage of it, one will add [SUCCESS=merge]

between two database entries in the nsswitch.conf file. When a group is

located in the first of the two group entries, processing will continue

on to the next one. If the group is also found in the next entry (and the

group name and GID are an exact match), the member list of the second

entry will be added to the group object to be returned.

== Implementation ==

After each DL_LOOKUP_FN() returns, the next action is checked. If the

function returned NSS_STATUS_SUCCESS and the next action is

NSS_ACTION_MERGE, a copy of the result buffer is saved for the next pass

through the loop. If on this next pass through the loop the database

returns another instance of a group matching both the group name and GID,

the member list is added to the previous list and it is returned as a

single object. If the following database does not contain the same group,

then the original is copied back into the destination buffer.

This patch implements merge functionality only for the group database.

For other databases, there is a default implementation that will return

the EINVAL errno if a merge is requested. The merge functionality can be

implemented for other databases at a later time if such is needed. Each

database must provide a unique implementation of the deep-copy and merge

functions.

If [SUCCESS=merge] is present in nsswitch.conf for a glibc version that

does not support it, glibc will process results up until that operation,

at which time it will return results if it has found them or else will

simply return an error. In practical terms, this ends up behaving like

the remainder of the nsswitch.conf line does not exist.

== Iterators ==

This feature does not modify the iterator functionality from its current

behavior. If getgrnam() or getgrgid() is called, glibc will iterate

through all entries in the `group` line in nsswitch.conf and display the

list of members without attempting to merge them. This is consistent with

the behavior of nss_files where if two separate lines are specified for

the same group in /etc/groups, getgrnam()/getgrgid() will display both.

Clients are already expected to handle this gracefully.

== No Premature Optimizations ==

The following is a list of places that might be eligible for

optimization, but were not overengineered for this initial contribution:

 * Any situation where a merge may occur will result in one malloc() of

   the same size as the input buffer.

 * Any situation where a merge does occur will result in a second

   malloc() to hold the list of pointers to member name strings.

 * The list of members is simply concatenated together and is not tested

   for uniqueness (which is identical to the behavior for nss_files,

   which will simply return identical values if they both exist on the

   line in the file. This could potentially be optimized to reduce space

   usage in the buffer, but it is both complex and computationally

   expensive to do so.

== Testing ==

I performed testing by running the getent utility against my newly-built

glibc and configuring /etc/nsswitch.conf with the following entry:

group: group:      files [SUCCESS=merge] sss

In /etc/group I included the line:

wheel:x:10:sgallagh

I then configured my local SSSD using the id_provider=local to respond

with:

wheel:*:10:localuser,localuser2

I then ran `getent group wheel` against the newly-built glibc in

multiple situations and received the expected output as described

above:

 * When SSSD was running.

 * When SSSD was configured in nsswitch.conf but the daemon was not

   running.

 * When SSSD was configured in nsswitch.conf but nss_sss.so.2 was not

   installed on the system.

 * When the order of 'sss' and 'files' was reversed.

 * All of the above with the [SUCCESS=merge] removed (to ensure no

   regressions).

 * All of the above with `getent group 10`.

 * All of the above with `getent group` with and without

   `enumerate=true` set in SSSD.

 * All of the above with and without nscd enabled on the system.

== NEWS ==

* A new NSS action is added to facilitate large distribution system

  administration.  The action, MERGE, allows remote user stores like

  LDAP to be merged into local user stores like /etc/groups in order

  to provide easy to use, updated, and managed sets of merged

  credentials.  The new action can be used by configuring it in

  /etc/nsswitch.conf:

  group: files [SUCCESS=merge] nis

  Implemented by Stephen Gallagher (Red Hat).

== ChangeLog ==

2015-12-16  Stephen Gallagher  <sgallagh@redhat.com>

	[BZ #19072]

	* grp/Makefile (headers): Add grp-merge.h

	(routines): Add grp-merge.

	* grp/getgrgid_r.c: Include grp-merge.h.

	(DEEPCOPY_FN): Define.

	(MERGE_FN): Define.

	* grp/getgrname_r.c: Include grp-merge.h.

	(DEEPCOPY_FN): Define.

	(MERGE_FN): Define.

	* grp/grp-merge.c: New file.

	* grp/grp-merge.h: New file.

	* manual/nss.texi (Actions in the NSS configuration): Describe

	return, continue, and merge.

	* nscd/Makefile: Add vpath to find grp-merge.c

	(nscd-modules): Add grp-merge.

	* nscd/getgrgid_r.c: Include grp/grp-merge.h.

	(DEEPCOPY_FN): Define.

	(MERGE_FN): Define.

	* nscd/getgrnam_r.c: Include grp/grp-merge.h.

	(DEEPCOPY_FN): Define.

	(MERGE_FN): Define.

	* nss/getXXbyYY_r.c [!DEEPCOPY_FN]: Define __copy_einval.

	[!MERGE_FN]: Define __merge_einval.

	(CHECK_MERGE): Define.

	(REENTRANT_NAME): Process merge if do_merge is true.

	* nss/getnssent_r.c (__nss_setent): Process NSS_ACTION_MERGE.

	(__nss_getent_r): Likewise.

	* nss/nsswitch.c (nss_parse_service_list): Likewise.

	* nss/nsswitch.h (lookup_actions): Define NSS_ACTION_MERGE.

Resolves BZ #19072

---

grp/Makefile      |   5 +-

 grp/getgrgid_r.c  |   3 +

 grp/getgrnam_r.c  |   4 ++

 grp/grp-merge.c   | 178 ++++++++++++++++++++++++++++++++++++++++++++++++++++++

 grp/grp-merge.h   |  35 +++++++++++

 manual/nss.texi   |  46 +++++++++++++-

 nscd/Makefile     |   5 +-

 nscd/getgrgid_r.c |   4 ++

 nscd/getgrnam_r.c |   4 ++

 nss/getXXbyYY_r.c | 105 +++++++++++++++++++++++++++++++-

 nss/getnssent_r.c |  34 ++++++++++-

 nss/nsswitch.c    |   3 +

 nss/nsswitch.h    |   3 +-

 13 files changed, 419 insertions(+), 10 deletions(-)

 create mode 100644 grp/grp-merge.c

 create mode 100644 grp/grp-merge.h

diff --git a/grp/Makefile b/grp/Makefile

index ed8cc2b0564f0e3842cd78f24a4e0788d659bbc4..52af992365268aae8cf8a80cd7216160b1431e84 100644

--- a/grp/Makefile

+++ b/grp/Makefile

@@ -20,15 +20,16 @@

 #

 subdir	:= grp

 include ../Makeconfig

-headers := grp.h

+headers := grp.h grp-merge.h

 routines := fgetgrent initgroups setgroups \

 	    getgrent getgrgid getgrnam putgrent \

-	    getgrent_r getgrgid_r getgrnam_r fgetgrent_r

+	    getgrent_r getgrgid_r getgrnam_r fgetgrent_r \

+	    grp-merge

 tests := testgrp tst-putgrent

 ifeq (yes,$(build-shared))

 test-srcs :=  tst_fgetgrent

diff --git a/grp/getgrgid_r.c b/grp/getgrgid_r.c

index 05d4d772d3ef0bfae8f9375387c41310885ce41a..447fa633807deec8f26d654ebeb6386a150d3a37 100644

--- a/grp/getgrgid_r.c

+++ b/grp/getgrgid_r.c

@@ -16,14 +16,17 @@

    License along with the GNU C Library; if not, see

    <http://www.gnu.org/licenses/>.  */

 #include <grp.h>

+#include "grp-merge.h"

 #define LOOKUP_TYPE	struct group

 #define FUNCTION_NAME	getgrgid

 #define DATABASE_NAME	group

 #define ADD_PARAMS	gid_t gid

 #define ADD_VARIABLES	gid

 #define BUFLEN		NSS_BUFLEN_GROUP

+#define DEEPCOPY_FN	__copy_grp

+#define MERGE_FN	__merge_grp

 #include <nss/getXXbyYY_r.c>

diff --git a/grp/getgrnam_r.c b/grp/getgrnam_r.c

index 0061cb2f7e0bd311d19775e49eb3fdd8a93447f1..c5535f4057ddfc40965f27789c34345045c8bf3b 100644

--- a/grp/getgrnam_r.c

+++ b/grp/getgrnam_r.c

@@ -16,13 +16,17 @@

    License along with the GNU C Library; if not, see

    <http://www.gnu.org/licenses/>.  */

 #include <grp.h>

+#include "grp-merge.h"

 #define LOOKUP_TYPE	struct group

 #define FUNCTION_NAME	getgrnam

 #define DATABASE_NAME	group

 #define ADD_PARAMS	const char *name

 #define ADD_VARIABLES	name

+#define DEEPCOPY_FN	__copy_grp

+#define MERGE_FN	__merge_grp

+

 #include <nss/getXXbyYY_r.c>

diff --git a/grp/grp-merge.c b/grp/grp-merge.c

new file mode 100644

index 0000000000000000000000000000000000000000..ca959dbfe403c89d6f3184f2b361b0c6488c9182

--- /dev/null

+++ b/grp/grp-merge.c

@@ -0,0 +1,178 @@

+/* Group merging implementation.

+   Copyright (C) 2016 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

+   <http://www.gnu.org/licenses/>.  */

+

+#include <errno.h>

+#include <stdlib.h>

+#include <string.h>

+#include <grp.h>

+#include "grp-merge.h"

+

+#define BUFCHECK(size)		\

+  do {						\

+    if (c + size > buflen)	\

+    {						\

+        free (members);		\

+        return ERANGE;		\

+    }						\

+  } while(0)

+

+int

+__copy_grp (const struct group srcgrp, const size_t buflen,

+	    struct group *destgrp, char *destbuf, char **endptr)

+{

+  size_t i;

+  size_t c = 0;

+  size_t len;

+  size_t memcount;

+  char **members = NULL;

+

+  /* Copy the GID.  */

+  destgrp->gr_gid = srcgrp.gr_gid;

+

+  /* Copy the name.  */

+  len = strlen (srcgrp.gr_name) + 1;

+  BUFCHECK (len);

+  memcpy (&destbuf[c], srcgrp.gr_name, len);

+  destgrp->gr_name = &destbuf[c];

+  c += len;

+

+  /* Copy the password.  */

+  len = strlen (srcgrp.gr_passwd) + 1;

+  BUFCHECK (len);

+  memcpy (&destbuf[c], srcgrp.gr_passwd, len);

+  destgrp->gr_passwd = &destbuf[c];

+  c += len;

+

+  /* Count all of the members.  */

+  for (memcount = 0; srcgrp.gr_mem[memcount]; memcount++)

+    ;

+

+  /* Allocate a temporary holding area for the pointers to the member

+     contents, including space for a NULL-terminator.  */

+  members = malloc (sizeof (char *) * (memcount + 1));

+  if (members == NULL)

+    return ENOMEM;

+

+  /* Copy all of the group members to destbuf and add a pointer to each of

+     them into the 'members' array.  */

+  for (i = 0; srcgrp.gr_mem[i]; i++)

+    {

+      len = strlen (srcgrp.gr_mem[i]) + 1;

+      BUFCHECK (len);

+      memcpy (&destbuf[c], srcgrp.gr_mem[i], len);

+      members[i] = &destbuf[c];

+      c += len;

+    }

+  members[i] = NULL;

+

+  /* Copy the pointers from the members array into the buffer and assign them

+     to the gr_mem member of destgrp.  */

+  destgrp->gr_mem = (char **) &destbuf[c];

+  len = sizeof (char *) * (memcount + 1);

+  BUFCHECK (len);

+  memcpy (&destbuf[c], members, len);

+  c += len;

+  free (members);

+  members = NULL;

+

+  /* Save the count of members at the end.  */

+  BUFCHECK (sizeof (size_t));

+  memcpy (&destbuf[c], &memcount, sizeof (size_t));

+  c += sizeof (size_t);

+

+  if (endptr)

+    *endptr = destbuf + c;

+  return 0;

+}

+

+/* Check that the name, GID and passwd fields match, then

+   copy in the gr_mem array.  */

+int

+__merge_grp (struct group *savedgrp, char *savedbuf, char *savedend,

+	     size_t buflen, struct group *mergegrp, char *mergebuf)

+{

+  size_t c, i, len;

+  size_t savedmemcount;

+  size_t memcount;

+  size_t membersize;

+  char **members = NULL;

+

+  /* We only support merging members of groups with identical names and

+     GID values. If we hit this case, we need to overwrite the current

+     buffer with the saved one (which is functionally equivalent to

+     treating the new lookup as NSS_STATUS NOTFOUND.  */

+  if (mergegrp->gr_gid != savedgrp->gr_gid

+      || strcmp (mergegrp->gr_name, savedgrp->gr_name))

+    return __copy_grp (*savedgrp, buflen, mergegrp, mergebuf, NULL);

+

+  /* Get the count of group members from the last sizeof (size_t) bytes in the

+     mergegrp buffer.  */

+  savedmemcount = (size_t) *(savedend - sizeof (size_t));

+

+  /* Get the count of new members to add.  */

+  for (memcount = 0; mergegrp->gr_mem[memcount]; memcount++)

+    ;

+

+  /* Create a temporary array to hold the pointers to the member values from

+     both the saved and merge groups.  */

+  membersize = savedmemcount + memcount + 1;

+  members = malloc (sizeof (char *) * membersize);

+  if (members == NULL)

+    return ENOMEM;

+

+  /* Copy in the existing member pointers from the saved group

+     Note: this is not NULL-terminated yet.  */

+  memcpy (members, savedgrp->gr_mem, sizeof (char *) * savedmemcount);

+

+  /* Back up into the savedbuf until we get back to the NULL-terminator of the

+     group member list. (This means walking back savedmemcount + 1 (char *) pointers

+     and the member count value.

+     The value of c is going to be the used length of the buffer backed up by

+     the member count and further backed up by the size of the pointers.  */

+  c = savedend - savedbuf

+      - sizeof (size_t)

+      - sizeof (char *) * (savedmemcount + 1);

+

+  /* Add all the new group members, overwriting the old NULL-terminator while

+     adding the new pointers to the temporary array.  */

+  for (i = 0; mergegrp->gr_mem[i]; i++)

+    {

+      len = strlen (mergegrp->gr_mem[i]) + 1;

+      BUFCHECK (len);

+      memcpy (&savedbuf[c], mergegrp->gr_mem[i], len);

+      members[savedmemcount + i] = &savedbuf[c];

+      c += len;

+    }

+  /* Add the NULL-terminator.  */

+  members[savedmemcount + memcount] = NULL;

+

+  /* Copy the member array back into the buffer after the member list and free

+     the member array.  */

+  savedgrp->gr_mem = (char **) &savedbuf[c];

+  len = sizeof (char *) * membersize;

+  BUFCHECK (len);

+  memcpy (&savedbuf[c], members, len);

+  c += len;

+

+  free (members);

+  members = NULL;

+

+  /* Finally, copy the results back into mergebuf, since that's the buffer

+     that we were provided by the caller.  */

+  return __copy_grp (*savedgrp, buflen, mergegrp, mergebuf, NULL);

+}

diff --git a/grp/grp-merge.h b/grp/grp-merge.h

new file mode 100644

index 0000000000000000000000000000000000000000..59013487d0d907c76521ab504e265077937bfb5e

--- /dev/null

+++ b/grp/grp-merge.h

@@ -0,0 +1,35 @@

+/* Group merging implementation.

+   Copyright (C) 2016 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

+   <http://www.gnu.org/licenses/>.  */

+

+#ifndef _GRP_MERGE_H

+#define _GRP_MERGE_H 1

+

+#include <grp.h>

+

+/* Duplicate a grp struct (and its members). When no longer needed, the

+   calling function must free(newbuf). */

+int

+__copy_grp (const struct group srcgrp, const size_t buflen,

+	    struct group *destgrp, char *destbuf, char **endptr);

+

+/* Merge the member lists of two grp structs together. */

+int

+__merge_grp (struct group *savedgrp, char *savedbuf, char *savedend,

+	     size_t buflen, struct group *mergegrp, char *mergebuf);

+

+#endif /* _GRP_MERGE_H */

diff --git a/manual/nss.texi b/manual/nss.texi

index 66dcceffe01f225f078e88dd006bb90e80c85723..95e3544bcd97995720e7154ec43df4090154bf4c 100644

--- a/manual/nss.texi

+++ b/manual/nss.texi

@@ -178,11 +178,11 @@ where

 @var{action} @result{} return | continue

 @end smallexample

 The case of the keywords is insignificant.  The @var{status}

 values are the results of a call to a lookup function of a specific

-service.  They mean

+service.  They mean:

 @ftable @samp

 @item success

 No error occurred and the wanted entry is returned.  The default action

 for this is @code{return}.

@@ -202,10 +202,54 @@ The service is temporarily unavailable.  This could mean a file is

 locked or a server currently cannot accept more connections.  The

 default action is @code{continue}.

 @end ftable

 @noindent

+The @var{action} values mean:

+

+@ftable @samp

+@item return

+

+If the status matches, stop the lookup process at this service

+specification.  If an entry is available, provide it to the application.

+If an error occurred, report it to the application.  In case of a prior

+@samp{merge} action, the data is combined with previous lookup results,

+as explained below.

+

+@item continue

+

+If the status matches, proceed with the lookup process at the next

+entry, discarding the result of the current lookup (and any merged

+data).  An exception is the @samp{initgroups} database and the

+@samp{success} status, where @samp{continue} acts like @code{merge}

+below.

+

+@item merge

+

+Proceed with the lookup process, retaining the current lookup result.

+This action is useful only with the @samp{success} status.  If a

+subsequent service lookup succeeds and has a matching @samp{return}

+specification, the results are merged, the lookup process ends, and the

+merged results are returned to the application.  If the following service

+has a matching @samp{merge} action, the lookup process continues,

+retaining the combined data from this and any previous lookups.

+

+After a @code{merge} action, errors from subsequent lookups are ignored,

+and the data gathered so far will be returned.

+

+The @samp{merge} only applies to the @samp{success} status.  It is

+currently implemented for the @samp{group} database and its group

+members field, @samp{gr_mem}.  If specified for other databases, it

+causes the lookup to fail (if the @var{status} matches).

+

+When processing @samp{merge} for @samp{group} membership, the group GID

+and name must be identical for both entries. If only one or the other is

+a match, the behavior is undefined.

+

+@end ftable

+

+@noindent

 If we have a line like

 @smallexample

 ethers: nisplus [NOTFOUND=return] db files

 @end smallexample

diff --git a/nscd/Makefile b/nscd/Makefile

index e1a1aa92fc699aa132f7192da49f698a078e5910..3e6895573ae33221c728617f4c95bb3e8c5d5c47 100644

--- a/nscd/Makefile

+++ b/nscd/Makefile

@@ -29,16 +29,19 @@ aux	:= nscd_helper

 endif

 # To find xmalloc.c

 vpath %.c ../locale/programs

+# To find grp-merge.c

+vpath %.c ../grp

+

 nscd-modules := nscd connections pwdcache getpwnam_r getpwuid_r grpcache \

 		getgrnam_r getgrgid_r hstcache gethstbyad_r gethstbynm3_r \

 		getsrvbynm_r getsrvbypt_r servicescache \

 		dbg_log nscd_conf nscd_stat cache mem nscd_setup_thread \

 		xmalloc xstrdup aicache initgrcache gai res_hconf \

-		netgroupcache

+		netgroupcache grp-merge

 ifeq ($(build-nscd)$(have-thread-library),yesyes)

 others += nscd

 others-pie += nscd

diff --git a/nscd/getgrgid_r.c b/nscd/getgrgid_r.c

index fe5bda424169d56f642f125ef1f2df77a84de221..25de4a3b0b74841c44844a0541cf4d2365b22515 100644

--- a/nscd/getgrgid_r.c

+++ b/nscd/getgrgid_r.c

@@ -15,17 +15,21 @@

    You should have received a copy of the GNU General Public License

    along with this program; if not, see <http://www.gnu.org/licenses/>.  */

 #include <grp.h>

+#include "grp/grp-merge.h"

 #define LOOKUP_TYPE	struct group

 #define FUNCTION_NAME	getgrgid

 #define DATABASE_NAME	group

 #define ADD_PARAMS	gid_t gid

 #define ADD_VARIABLES	gid

 #define BUFLEN		NSS_BUFLEN_GROUP

+#define DEEPCOPY_FN	__copy_grp

+#define MERGE_FN	__merge_grp

+

 /* We are nscd, so we don't want to be talking to ourselves.  */

 #undef	USE_NSCD

 #include <nss/getXXbyYY_r.c>

diff --git a/nscd/getgrnam_r.c b/nscd/getgrnam_r.c

index 5ec56877f5798ca34c2e0074d5093cc22b6d58dc..386d66c5832ffee68e95195f6e34b723f41d0984 100644

--- a/nscd/getgrnam_r.c

+++ b/nscd/getgrnam_r.c

@@ -15,16 +15,20 @@

    You should have received a copy of the GNU General Public License

    along with this program; if not, see <http://www.gnu.org/licenses/>.  */

 #include <grp.h>

+#include "grp/grp-merge.h"

 #define LOOKUP_TYPE	struct group

 #define FUNCTION_NAME	getgrnam

 #define DATABASE_NAME	group

 #define ADD_PARAMS	const char *name

 #define ADD_VARIABLES	name

+#define DEEPCOPY_FN	__copy_grp

+#define MERGE_FN	__merge_grp

+

 /* We are nscd, so we don't want to be talking to ourselves.  */

 #undef	USE_NSCD

 #include <nss/getXXbyYY_r.c>

diff --git a/nss/getXXbyYY_r.c b/nss/getXXbyYY_r.c

index 198f8cfebd51be9c738f03f950f093b0855ab3cb..5f49ae8b828fce6dc30c7ccc9606319bffc52d5b 100644

--- a/nss/getXXbyYY_r.c

+++ b/nss/getXXbyYY_r.c

@@ -129,10 +129,52 @@

 # define AF_VAL af

 #else

 # define AF_VAL AF_INET

 #endif

+

+/* Set defaults for merge functions that haven't been defined.  */

+#ifndef DEEPCOPY_FN

+static inline int

+__copy_einval (LOOKUP_TYPE a,

+	      const size_t b,

+	      LOOKUP_TYPE *c,

+	      char *d,

+	      char **e)

+{

+  return EINVAL;

+}

+# define DEEPCOPY_FN __copy_einval

+#endif

+

+#ifndef MERGE_FN

+static inline int

+__merge_einval (LOOKUP_TYPE *a,

+	       char *b,

+	       char *c,

+	       size_t d,

+	       LOOKUP_TYPE *e,

+	       char *f)

+{

+  return EINVAL;

+}

+# define MERGE_FN __merge_einval

+#endif

+

+#define CHECK_MERGE(err, status)	\

+do {					\

+  if (err)				\

+    {					\

+      __set_errno (err);		\

+      if (err == ERANGE)		\

+          status = NSS_STATUS_TRYAGAIN;	\

+      else				\

+          status = NSS_STATUS_UNAVAIL;	\

+      break;				\

+    }					\

+} while(0)

+

 /* Type of the lookup function we need here.  */

 typedef enum nss_status (*lookup_function) (ADD_PARAMS, LOOKUP_TYPE *, char *,

 					    size_t, int * H_ERRNO_PARM

 					    EXTRA_PARAMS);

@@ -150,17 +192,20 @@ INTERNAL (REENTRANT_NAME) (ADD_PARAMS, LOOKUP_TYPE *resbuf, char *buffer,

 {

   static bool startp_initialized;

   static service_user *startp;

   static lookup_function start_fct;

   service_user *nip;

+  int do_merge = 0;

+  LOOKUP_TYPE mergegrp;

+  char *mergebuf = NULL;

+  char *endptr = NULL;

   union

   {

     lookup_function l;

     void *ptr;

   } fct;

-

-  int no_more;

+  int no_more, err;

   enum nss_status status = NSS_STATUS_UNAVAIL;

 #ifdef USE_NSCD

   int nscd_status;

 #endif

 #ifdef NEED_H_ERRNO

@@ -276,13 +321,69 @@ INTERNAL (REENTRANT_NAME) (ADD_PARAMS, LOOKUP_TYPE *resbuf, char *buffer,

 	  && *h_errnop == NETDB_INTERNAL

 #endif

 	  && errno == ERANGE)

 	break;

+      if (do_merge)

+	{

+

+	  if (status == NSS_STATUS_SUCCESS)

+	    {

+		/* The previous loop saved a buffer for merging.

+		   Perform the merge now.  */

+		err = MERGE_FN (&mergegrp, mergebuf, endptr, buflen, resbuf,

+				buffer);

+		CHECK_MERGE (err,status);

+		do_merge = 0;

+	    }

+	  else

+	    {

+	      /* If the result wasn't SUCCESS, copy the saved buffer back

+	         into the result buffer and set the status back to

+	         NSS_STATUS_SUCCESS to match the previous pass through the loop.

+	          * If the next action is CONTINUE, it will overwrite the value

+	            currently in the buffer and return the new value.

+	          * If the next action is RETURN, we'll return the previously-

+	            acquired values.

+	          * If the next action is MERGE, then it will be added to the buffer

+	            saved from the previous source.  */

+	      err = DEEPCOPY_FN (mergegrp, buflen, resbuf, buffer, NULL);

+	      CHECK_MERGE (err, status);

+	      status = NSS_STATUS_SUCCESS;

+	    }

+	}

+

+      /* If we were are configured to merge this value with the next one,

+         save the current value of the group struct.  */

+      if (nss_next_action (nip, status) == NSS_ACTION_MERGE

+	  && status == NSS_STATUS_SUCCESS)

+	{

+	  /* Copy the current values into a buffer to be merged with the next

+	     set of retrieved values.  */

+	  if (!mergebuf)

+	    {

+	      /* Only allocate once and reuse it for as many merges as we need

+	         to perform.  */

+	      mergebuf = malloc (buflen);

+	      if (!mergebuf)

+		{

+		  __set_errno (ENOMEM);

+		  status = NSS_STATUS_UNAVAIL;

+		  break;

+		}

+	    }

+

+	  err = DEEPCOPY_FN (*resbuf, buflen, &mergegrp, mergebuf, &endptr);

+	  CHECK_MERGE (err, status);

+	  do_merge = 1;

+	}

+

       no_more = __nss_next2 (&nip, REENTRANT_NAME_STRING,

 			     REENTRANT2_NAME_STRING, &fct.ptr, status, 0);

     }

+  free(mergebuf);

+  mergebuf = NULL;

 #ifdef HANDLE_DIGITS_DOTS

 done:

 #endif

   *result = status == NSS_STATUS_SUCCESS ? resbuf : NULL;

diff --git a/nss/getnssent_r.c b/nss/getnssent_r.c

index f5b903671ca53ccad108eeb4e49ea40a45fa5cdf..c0743436f661d4d83045a6353b49291a4c0f220b 100644

--- a/nss/getnssent_r.c

+++ b/nss/getnssent_r.c

@@ -77,11 +77,25 @@ __nss_setent (const char *func_name, db_lookup_function lookup_fct,

       if (stayopen_tmp)

 	status = DL_CALL_FCT (fct.f, (*stayopen_tmp));

       else

 	status = DL_CALL_FCT (fct.f, (0));

-      no_more = __nss_next2 (nip, func_name, NULL, &fct.ptr, status, 0);

+      if (nss_next_action (*nip, status) == NSS_ACTION_MERGE)

+	{

+	  /* This is a special-case. When [SUCCESS=merge] is in play,

+	     _nss_next2() will skip to the next database.  Due to the

+	     implementation of that function, we can't know whether we're

+	     in an enumeration or an individual lookup, which behaves

+	     differently with regards to merging.  We'll treat SUCCESS as

+	     an indication to start the enumeration at this database. */

+	  no_more = 1;

+	}

+      else

+	{

+	  no_more = __nss_next2 (nip, func_name, NULL, &fct.ptr, status, 0);

+	}

+

       if (is_last_nip)

 	*last_nip = *nip;

     }

   if (stayopen_tmp)

@@ -173,12 +187,26 @@ __nss_getent_r (const char *getent_func_name,

 	  && errno == ERANGE)

 	break;

       do

 	{

-	  no_more = __nss_next2 (nip, getent_func_name, NULL, &fct.ptr,

-				 status, 0);

+	  if (status == NSS_STATUS_SUCCESS

+	      && nss_next_action (*nip, status) == NSS_ACTION_MERGE)

+	    {

+	      /* This is a special-case. When [SUCCESS=merge] is in play,

+	         _nss_next2() will skip to the next database.  Due to the

+	         implementation of that function, we can't know whether we're

+	         in an enumeration or an individual lookup, which behaves

+	         differently with regards to merging.  We'll treat SUCCESS as

+	         an indication to return the results here. */

+	      no_more = 1;

+	    }

+	  else

+	    {

+	      no_more = __nss_next2 (nip, getent_func_name, NULL, &fct.ptr,

+				     status, 0);

+	    }

 	  if (is_last_nip)

 	    *last_nip = *nip;

 	  if (! no_more)

diff --git a/nss/nsswitch.c b/nss/nsswitch.c

index faf9d1a0d5680aa79e88b2dfeea18da371c336fb..f8f60ba05aad9a571f928a3ea7d3b14f908ccb2d 100644

--- a/nss/nsswitch.c

+++ b/nss/nsswitch.c

@@ -710,10 +710,13 @@ nss_parse_service_list (const char *line)

 	      if (line - name == 6 && __strncasecmp (name, "RETURN", 6) == 0)

 		action = NSS_ACTION_RETURN;

 	      else if (line - name == 8

 		       && __strncasecmp (name, "CONTINUE", 8) == 0)

 		action = NSS_ACTION_CONTINUE;

+	      else if (line - name == 5

+		       && __strncasecmp (name, "MERGE", 5) == 0)

+		action = NSS_ACTION_MERGE;

 	      else

 		goto finish;

 	      if (not)

 		{

diff --git a/nss/nsswitch.h b/nss/nsswitch.h

index a5318fa82be43c8314807ad76de231e572e91c06..5bc2de3b1d82978102ac7a129c0ba5b7eb3cfd25 100644

--- a/nss/nsswitch.h

+++ b/nss/nsswitch.h

@@ -30,11 +30,12 @@

 /* Actions performed after lookup finished.  */

 typedef enum

 {

   NSS_ACTION_CONTINUE,

-  NSS_ACTION_RETURN

+  NSS_ACTION_RETURN,

+  NSS_ACTION_MERGE

 } lookup_actions;

 typedef struct service_library

 {