[Bug 1697339] Re: rpc.gssd performs reverse DNS by default (regardless of -D flag)

[Ubuntu Foundations Team Bug Bot]

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** Tags added: patch

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Title:
  rpc.gssd performs reverse DNS by default (regardless of -D flag)

Status in nfs-utils package in Ubuntu:
  New

Bug description:
  Description:	Ubuntu 16.04.2 LTS
  Release:	16.04

  Package: nfs-common 1:1.2.8-9ubuntu12.1.0

  This bug affects all active and proposed versions of nfs-common used
  by ubuntu (as every version is based on nfs-utils_1.2.8) from trusty
  to artful.

  There is a small error in the code for rpc.gssd that causes it to always perform reverse DNS when looking up the server name to pass to GSSAPI. This causes a problem for NFS4 in environments where reverse DNS is correctly configured. This has been confirmed in Debian and a more recent version of nfs-utils that appears to have fixed this has been pushed to sid:
  https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=803710

  However, I do not know if that version of nfs-utils will make it to
  ubuntu soon. Will it?

  If not, the patch to this appears to be rather straightforward.
  The error is an '== 1' instead of an '== 0' in two lines of gssd_proc.c that are evaluated when the -D flag to rpc.gssd is not passed (and thus avoid_dns is true)

  --- utils/gssd/gssd_proc.c	2017-06-11 15:47:35.000000000 -0700
  +++ utils/gssd/gssd_proc_patch.c	2017-06-11 15:48:36.152115792 -0700
  @@ -181,17 +181,17 @@
   	if (avoid_dns) {
   		/*
   		 * Determine if this is a server name, or an IP address.
   		 * If it is an IP address, do the DNS lookup otherwise
   		 * skip the DNS lookup.
   		 */
   		servername = 0;
  -		if (strchr(name, '.') && inet_pton(AF_INET, name, buf) == 1)
  +		if (strchr(name, '.') && inet_pton(AF_INET, name, buf) == 0)
   			servername = 1; /* IPv4 */
  -		else if (strchr(name, ':') && inet_pton(AF_INET6, name, buf) == 1)
  +		else if (strchr(name, ':') && inet_pton(AF_INET6, name, buf) == 0)
   			servername = 1; /* or IPv6 */
   
   		if (servername) {
   			return strdup(name);
   		}
   	}

  Is there any way to get either 1) the updated version of nfs-utils or
  2) this patch applied to xenial (and, hopefully, other versions of
  ubuntu)? Thank you for looking at this!

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