[Bug 172336] New: getgrnam() crashes with "Out of memory" if /etc/group contains long lines

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https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=172336

           Summary: getgrnam() crashes with "Out of memory" if /etc/group
                    contains   long lines
           Product: Fedora Core
           Version: fc4
          Platform: i386
               URL: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=227621
        OS/Version: Linux
            Status: NEW
          Severity: security
          Priority: normal
         Component: perl
        AssignedTo: jvdias at redhat.com
        ReportedBy: jvdias at redhat.com
         QAContact: dkl at redhat.com
                CC: fedora-perl-devel-list at redhat.com,prockai at redhat.com


+++ This bug was initially created as a clone of Bug #163958 +++

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Description of problem:
This bug has been fixed in Debian and in newest Perl. I'm just wondering does
this concern RHEL 3 too, because we are rather close having "too much" users in
one group and I would rather see this bug fixed before that we are going to have
problems.

* Fix test of reenterant function return values which was causing
  perl to malloc itself to death if ERANGE was encountered before
  ENOENT (such as a long line in /etc/group; closes: #227621).

Version-Release number of selected component (if applicable):


How reproducible:
Didn't try


Additional info:

-- Additional comment from jvdias at redhat.com on 2005-11-02 16:23 EST --
This is PERL bug 37056, fixed with patch 25084 in bleadperl (5.9.x):
   (  http://rt.perl.org/rt3/Ticket/Display.html?id=37056 )
   	
Subject: getgrent fails if a line in /etc/groups gets too long
Date: Fri, 02 Sep 2005 15:53:08 +0200
To: perlbug at perl.org
From: Michiel Blotwijk <michiel at blotwijk.com>

This is a bug report for perl from michiel at altiplano.be,
generated with the help of perlbug 1.35 running under perl v5.8.5.


-----------------------------------------------------------------
[Please enter your report here]

The function getgrent throws an error if a line in /etc/groups gets
too long (> 3000 characters). This error can be reproduced as follows:

1/ Manually add a large number of users to a group in /etc/group. It doesn't
really matter if these are real users or not, as long as the line exceeds
3000 characters.

2/ perl -e 'use User::grent; while (my $gr = getgrent() ) { print
$gr->name."\n"; }'

This will return an "Out of memory!" message.

This thread seems to be related:
http://lists.debian.org/debian-security/2005/06/msg00041.html

Originally reported at Debian:

http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=227621

As said in the Debian bug report:

From: "Steinar H. Gunderson" <sgunderson at bigfoot.com>
To: Peter Palúch <peterp at frix.fri.utc.sk>
Cc: control at bugs.debian.org, 227621 at bugs.debian.org,
	debian-security at lists.debian.org
Subject: Re: perl: getgrnam() crashes with "Out of memory" if /etc/group
contains long lines
Date: Fri, 10 Jun 2005 15:03:02 +0200

It's about the same bug in perl as it was in glibc. reentr.pl line 698 reads:

  $call = qq[((PL_REENTRANT_RETINT = $call)$test ? $true :
(((PL_REENTRANT_RETINT == ERANGE) || (errno == ERANGE)) ? 
($seenm{$func}{$seenr{$func}})Perl_reentrant_retry("$func"$rv) : 0))];
  
The problem here is "errno == ERANGE". If, at any time, there's a line longer
than the initial buffer, getgrent() (or any in the same family) will get
ERANGE back (and errno will be set to ERANGE). However, this is never reset.
Thus, when getgrent_r() hits EOF, it returns ENOENT, _but errno is still
ERANGE_. Perl figures the buffer was too small, doubles it and tries again,
but still gets ENOENT, of course (and errno is still ERANGE). This goes on
forever and ever until you run out of memory (which happens quite fast).

The solution is simply to remove "errno == ERANGE" AFAICS; getgrent_r() does
not define what happens to errno, and the return message will always be
ERANGE if the buffer is too small.

I'm a bit tempted to tag this "security"; if a user can (say) change his or
her own GECOS field to make it long enough, Perl programs using getpwent()
will crash, for instance. I can't find any direct way to exploit it (chfn
limits the length of the fields, for instance), but I'm still slightly
concerned over the possibilities of a DoS; Cc-ing debian-security.

/* Steinar */

I agree this bug has security implications .

This problem affects all {get,set}* nss perl wrapper functions, not only
getgrent .

This problem affects all previous releases of PERL in all current Red Hat
releases.

The patch is very straightforward - replace all occurences of 
  ((PL_REENTRANT_RETINT == ERANGE) || (errno == ERANGE))
with 
  (PL_REENTRANT_RETINT == ERANGE)
in reentr.inc and reentr.pl. 

This bug is now being fixed in these perl versions:

Rawhide / FC-5   : perl-5.8.7-0.7.fc5
          FC-4   : perl-5.8.6-16
          RHEL-4 : perl-5.8.5-17.RHEL4
          RHEL-3 : perl-5.8.0-90.2

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