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

[Tom Yu]

Recent discussion on #krbdev suggests that this is actually (in part) a
glibc bug in getaddinfo(). With ai_flags=AI_CANONNAME and
ai_family=AF_INET, getaddrinfo() performs a PTR lookup anyway (contrary
to POSIX), effectively preventing a setting of rdns=false from being
effective. We have a workaround for the glibc bug upstream at
http://krbdev.mit.edu/rt/Ticket/Display.html?id=6922

** Bug watch added: krbdev.mit.edu/rt/ #6922
   http://krbdev.mit.edu/rt/Ticket/Display.html?id=6922

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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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