[PATCH COMMITTED] sunrpc: Always obtain AF_INET addresses from NSS [BZ #20964]

[fweimer at redhat dot com (Florian Weimer)]

The new __libc_rpc_gethostbyname function calls gethostbyname2_r
with an AF_INET argument and is therefore not affected by the
RES_USE_INET6 flag.

Validated with the following test program, with and without
RES_OPTIONS=inet6, against a NFS server.  (Link with -lrpcsvc.)

#include <rpc/clnt.h>
#include <rpcsvc/mount.h>
#include <stdio.h>
#include <string.h>

static void
usage (char **argv)
{
  printf ("usage:\n"
          "  %1$s HOST getrpcport\n"
          "  %1$s HOST callrpc\n"
          "  %1$s HOST clnt_create\n",
          argv[0]);
}

static void
dump_exports (struct exportnode *exports)
{
  while (exports != NULL)
    {
      printf ("%s\n", exports->ex_dir);
      exports = exports->ex_next;
    }
}

int
main (int argc, char **argv)
{
  if (argc != 3)
    {
      usage (argv);
      return 1;
    }

  const char *host = argv[1];
  const char *command = argv[2];

  if (strcmp (command, "getrpcport") == 0)
    {
      int port = getrpcport (host, MOUNTPROG, MOUNTVERS, IPPROTO_UDP);
      printf ("getrpcport: %d\n", port);
    }
  else if (strcmp (command, "callrpc") == 0)
    {
      struct exportnode *exports = NULL;
      int ret = callrpc (host, MOUNTPROG, MOUNTVERS, MOUNTPROC_EXPORT,
                         (xdrproc_t) xdr_void, NULL,
                         (xdrproc_t) xdr_exports, (char *)&exports);
      if (ret != 0)
        {
          clnt_perrno (ret);
          puts ("");
          return 1;
        }
      dump_exports (exports);
    }
  else if (strcmp (command, "clnt_create") == 0)
    {
      CLIENT *client = clnt_create
        (host, MOUNTPROG, MOUNTVERS, "udp");
      if (client == NULL)
        {
          printf ("error: clnt_create failed\n");
          return 1;
        }
      struct exportnode *exports = NULL;
      int ret = CLNT_CALL (client, MOUNTPROC_EXPORT,
                           (xdrproc_t) xdr_void, NULL,
                           (xdrproc_t) xdr_exports, (char *)&exports,
                           ((struct timeval) {15, 0}));
      if (ret != 0)
        {
          clnt_perrno (ret);
          puts ("");
          return 1;
        }
      dump_exports (exports);
    }
  else
    {
      usage (argv);
      return 1;
    }

  return 0;
}

2016-12-27  Florian Weimer  <fweimer@redhat.com>

	[BZ #20964]
	sunrpc: Always obtain AF_INET addresses from NSS.
	* include/rpc/rpc.h (__libc_rpc_gethostbyname): Declare.
	* sunrpc/rpc_gethostbyname.c: New file.
	* sunrpc/Makefile (routines): Add it.
	* sunrpc/clnt_gen.c (clnt_create): Use __libc_rpc_gethostbyname.
	* sunrpc/clnt_simp.c (callrpc): Likewise.
	* sunrpc/getrpcport.c (getrpcport): Likewise.

diff --git a/include/rpc/rpc.h b/include/rpc/rpc.h
index 4c9ee82..60c7896 100644
--- a/include/rpc/rpc.h
+++ b/include/rpc/rpc.h
@@ -57,6 +57,12 @@ libc_hidden_proto (__rpc_thread_svc_pollfd)
 libc_hidden_proto (__rpc_thread_svc_fdset)
 libc_hidden_proto (__rpc_thread_createerr)
 
+/* Perform a host name lookup for NAME and return the first IPv4
+   address in *ADDR.  Return 0 on success and -1 on error (and set an
+   RPC error).  */
+int __libc_rpc_gethostbyname (const char *host, struct sockaddr_in *addr)
+  attribute_hidden;
+
 #endif /* _RPC_THREAD_SAFE_ */
 
 # endif /* !_ISOMAC */
diff --git a/sunrpc/Makefile b/sunrpc/Makefile
index da6dffa..f7c593a 100644
--- a/sunrpc/Makefile
+++ b/sunrpc/Makefile
@@ -78,7 +78,8 @@ routines := auth_none authuxprot bindrsvprt clnt_raw clnt_simp \
 	    des_crypt des_impl des_soft key_prot openchild rtime svcauth_des \
 	    getrpcent getrpcbyname getrpcbynumber \
 	    getrpcent_r getrpcbyname_r getrpcbynumber_r \
-	    clnt_unix svc_unix create_xid $(need-export-routines)
+	    clnt_unix svc_unix create_xid $(need-export-routines) \
+	    rpc_gethostbyname
 ifneq ($(link-obsolete-rpc),yes)
 # We only add the RPC for compatibility to libc.so.
 shared-only-routines = $(routines)
diff --git a/sunrpc/clnt_gen.c b/sunrpc/clnt_gen.c
index df34672..8dffaa9 100644
--- a/sunrpc/clnt_gen.c
+++ b/sunrpc/clnt_gen.c
@@ -45,9 +45,6 @@ CLIENT *
 clnt_create (const char *hostname, u_long prog, u_long vers,
 	     const char *proto)
 {
-  struct hostent hostbuf, *h;
-  size_t hstbuflen;
-  char *hsttmpbuf;
   struct protoent protobuf, *p;
   size_t prtbuflen;
   char *prttmpbuf;
@@ -56,7 +53,6 @@ clnt_create (const char *hostname, u_long prog, u_long vers,
   int sock;
   struct timeval tv;
   CLIENT *client;
-  int herr;
 
   if (strcmp (proto, "unix") == 0)
     {
@@ -78,37 +74,8 @@ clnt_create (const char *hostname, u_long prog, u_long vers,
       return client;
     }
 
-  hstbuflen = 1024;
-  hsttmpbuf = __alloca (hstbuflen);
-  while (__gethostbyname_r (hostname, &hostbuf, hsttmpbuf, hstbuflen,
-			    &h, &herr) != 0
-	 || h == NULL)
-    if (herr != NETDB_INTERNAL || errno != ERANGE)
-      {
-	get_rpc_createerr().cf_stat = RPC_UNKNOWNHOST;
-	return NULL;
-      }
-    else
-      {
-	/* Enlarge the buffer.  */
-	hstbuflen *= 2;
-	hsttmpbuf = __alloca (hstbuflen);
-      }
-
-  if (h->h_addrtype != AF_INET)
-    {
-      /*
-       * Only support INET for now
-       */
-      struct rpc_createerr *ce = &get_rpc_createerr ();
-      ce->cf_stat = RPC_SYSTEMERROR;
-      ce->cf_error.re_errno = EAFNOSUPPORT;
-      return NULL;
-    }
-  sin.sin_family = h->h_addrtype;
-  sin.sin_port = 0;
-  __bzero (sin.sin_zero, sizeof (sin.sin_zero));
-  memcpy ((char *) &sin.sin_addr, h->h_addr, h->h_length);
+  if (__libc_rpc_gethostbyname (hostname, &sin) != 0)
+    return NULL;
 
   prtbuflen = 1024;
   prttmpbuf = __alloca (prtbuflen);
diff --git a/sunrpc/clnt_simp.c b/sunrpc/clnt_simp.c
index d612df0..0ecb64c 100644
--- a/sunrpc/clnt_simp.c
+++ b/sunrpc/clnt_simp.c
@@ -61,7 +61,6 @@ callrpc (const char *host, u_long prognum, u_long versnum, u_long procnum,
   struct callrpc_private_s *crp = callrpc_private;
   struct sockaddr_in server_addr;
   enum clnt_stat clnt_stat;
-  struct hostent hostbuf, *hp;
   struct timeval timeout, tottimeout;
 
   if (crp == 0)
@@ -84,10 +83,6 @@ callrpc (const char *host, u_long prognum, u_long versnum, u_long procnum,
     }
   else
     {
-      size_t buflen;
-      char *buffer;
-      int herr;
-
       crp->valid = 0;
       if (crp->socket != RPC_ANYSOCK)
 	{
@@ -100,25 +95,11 @@ callrpc (const char *host, u_long prognum, u_long versnum, u_long procnum,
 	  crp->client = NULL;
 	}
 
-      buflen = 1024;
-      buffer = __alloca (buflen);
-      while (__gethostbyname_r (host, &hostbuf, buffer, buflen,
-				&hp, &herr) != 0
-	     || hp == NULL)
-	if (herr != NETDB_INTERNAL || errno != ERANGE)
-	  return (int) RPC_UNKNOWNHOST;
-	else
-	  {
-	    /* Enlarge the buffer.  */
-	    buflen *= 2;
-	    buffer = __alloca (buflen);
-	  }
+      if (__libc_rpc_gethostbyname (host, &server_addr) != 0)
+	return (int) get_rpc_createerr().cf_stat;
 
       timeout.tv_usec = 0;
       timeout.tv_sec = 5;
-      memcpy ((char *) &server_addr.sin_addr, hp->h_addr, hp->h_length);
-      server_addr.sin_family = AF_INET;
-      server_addr.sin_port = 0;
       if ((crp->client = clntudp_create (&server_addr, (u_long) prognum,
 			  (u_long) versnum, timeout, &crp->socket)) == NULL)
 	return (int) get_rpc_createerr().cf_stat;
diff --git a/sunrpc/getrpcport.c b/sunrpc/getrpcport.c
index 07ee8c0..8fde0a9 100644
--- a/sunrpc/getrpcport.c
+++ b/sunrpc/getrpcport.c
@@ -1,3 +1,21 @@
+/* Obtain the RPC port number for an RPC service on a host.
+   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; see the file COPYING.LIB.  If
+   not, see <http://www.gnu.org/licenses/>.  */
+
 /*
  * Copyright (c) 2010, Oracle America, Inc.
  *
@@ -43,26 +61,8 @@ int
 getrpcport (const char *host, u_long prognum, u_long versnum, u_int proto)
 {
   struct sockaddr_in addr;
-  struct hostent hostbuf, *hp;
-  size_t buflen;
-  char *buffer;
-  int herr;
 
-  buflen = 1024;
-  buffer = __alloca (buflen);
-  while (__gethostbyname_r (host, &hostbuf, buffer, buflen, &hp, &herr) != 0
-	 || hp == NULL)
-    if (herr != NETDB_INTERNAL || errno != ERANGE)
-      return 0;
-    else
-      {
-	/* Enlarge the buffer.  */
-	buflen *= 2;
-	buffer = __alloca (buflen);
-      }
-
-  memcpy ((char *) &addr.sin_addr, hp->h_addr, hp->h_length);
-  addr.sin_family = AF_INET;
-  addr.sin_port = 0;
+  if (__libc_rpc_gethostbyname (host, &addr) != 0)
+    return 0;
   return pmap_getport (&addr, prognum, versnum, proto);
 }
diff --git a/sunrpc/rpc_gethostbyname.c b/sunrpc/rpc_gethostbyname.c
new file mode 100644
index 0000000..a2ee960
--- /dev/null
+++ b/sunrpc/rpc_gethostbyname.c
@@ -0,0 +1,73 @@
+/* IPv4-only variant of gethostbyname.
+   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; see the file COPYING.LIB.  If
+   not, see <http://www.gnu.org/licenses/>.  */
+
+#include <errno.h>
+#include <netdb.h>
+#include <rpc/rpc.h>
+#include <scratch_buffer.h>
+#include <string.h>
+
+int
+__libc_rpc_gethostbyname (const char *host, struct sockaddr_in *addr)
+{
+  struct hostent hostbuf;
+  struct hostent *hp = NULL;
+  int herr;
+  struct scratch_buffer tmpbuf;
+  scratch_buffer_init (&tmpbuf);
+
+  while (__gethostbyname2_r (host, AF_INET,
+                             &hostbuf, tmpbuf.data, tmpbuf.length, &hp,
+                             &herr) != 0
+         || hp == NULL)
+    if (herr != NETDB_INTERNAL || errno != ERANGE)
+      {
+        struct rpc_createerr *ce = &get_rpc_createerr ();
+        ce->cf_stat = RPC_UNKNOWNHOST;
+        scratch_buffer_free (&tmpbuf);
+        return -1;
+      }
+    else
+      {
+        if (!scratch_buffer_grow (&tmpbuf))
+          {
+            /* If memory allocation failed, allocating the RPC error
+               structure might could as well, so this could lead to a
+               crash.  */
+            struct rpc_createerr *ce = &get_rpc_createerr ();
+            ce->cf_stat = RPC_SYSTEMERROR;
+            ce->cf_error.re_errno = ENOMEM;
+            return -1;
+          }
+      }
+
+  if (hp->h_addrtype != AF_INET || hp->h_length != sizeof (addr->sin_addr))
+    {
+      struct rpc_createerr *ce = &get_rpc_createerr ();
+      ce->cf_stat = RPC_SYSTEMERROR;
+      ce->cf_error.re_errno = EAFNOSUPPORT;
+      scratch_buffer_free (&tmpbuf);
+      return -1;
+    }
+
+  addr->sin_family = AF_INET;
+  addr->sin_port = htons (0);
+  memcpy (&addr->sin_addr, hp->h_addr, sizeof (addr->sin_addr));
+  scratch_buffer_free (&tmpbuf);
+  return 0;
+}