[Bug 571572] Re: krb5 prefers the reverse pointer no matter what for locating service tickets.

Tom Yu tlyu at mit.edu
Sat Jan 12 04:14:44 UTC 2013


I would strongly recommend SRUs for all supported releases, because this
is a high-impact bug for people who are deploying krb5 in environments
where they do not have tight control over their reverse DNS information.
Experience has shown that this type of hard-to-debug DNS interaction
leads to a lot of frustration and wasted time.

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https://bugs.launchpad.net/bugs/571572

Title:
  krb5 prefers the reverse pointer no matter what for locating service
  tickets.

Status in “krb5” package in Ubuntu:
  Confirmed

Bug description:
  I'm trying to upgrade workstations to lucid an fails to access our
  kerberos enabled websites. It reveals that the krb5 implementation in
  lucid now tries to resolve the "reverse dns" and aquire a tikket for
  <service>/<reverse dns> instead of <service>/<what the user typed in
  the first place>.

  The latter behavior is what the MS environment does and is what Ubuntu
  has done (i think) until Lucid. A diff of the sourcecode from hardy
  revealse that we now hint the getaddrinfo with AI_CANONNAME which it
  didnt before.

  Applying below patch enables the old behaviour.

  --- krb5-1.8.1+dfsg/src/lib/krb5/os/sn2princ.c.orig	2010-04-29 09:04:11.401567914 +0200
  +++ krb5-1.8.1+dfsg/src/lib/krb5/os/sn2princ.c	2010-04-29 09:04:21.762191834 +0200
  @@ -112,7 +112,7 @@
   
               memset(&hints, 0, sizeof(hints));
               hints.ai_family = AF_INET;
  -            hints.ai_flags = AI_CANONNAME;
  +//            hints.ai_flags = AI_CANONNAME;
           try_getaddrinfo_again:
               err = getaddrinfo(hostname, 0, &hints, &ai);
               if (err) {

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