iDEFENSE Security Advisory 2005-10-10.t

`SGI IRIX runpriv Design Error Vulnerability   
  
iDEFENSE Security Advisory 10.10.05  
www.idefense.com/application/poi/display?id=312&type=vulnerabilities  
October 10, 2005  
  
I. BACKGROUND  
  
The runpriv program is a setuid root application that checks to see if a  
  
regular user has been granted privileges to execute a certain predefined  
  
command, and if so it runs the command found in the directory   
/usr/sysadm/privbin with root privileges. It is installed by default   
under multiple versions of IRIX 6.   
  
II. DESCRIPTION  
  
Local exploitation of a design error vulnerability in the runpriv   
command included in multiple versions of Silicon Graphics Inc.'s IRIX   
could allow for arbitrary code execution as the root user.  
  
The runpriv program is a setuid root application that checks to see if a  
  
regular user has been granted privileges to execute a certain predefined  
  
command, and if so it runs the command found in the directory   
/usr/sysadm/privbin with root privileges.   
  
The vulnerability specifically exists because runpriv unsafely executes   
commands after it has verified a user's privileges. This allows an   
attacker who has been given privileged access to one binary in   
/usr/sysadm/privbin to effectively execute any command as root. To   
exploit this vulnerability, all that is required is appending a string   
of the form "command to execute" to the end of an otherwise authorized   
and legitimate command. For example, if a user has been authorized to   
run the mountfs utility, they can exploit this vulnerability in the   
following way:   
  
/usr/sysadm/bin/runpriv mountfs -s test -d / -o \|  
"ksh -c 'echo r00t::0:0:r00t:/tmp:/bin/sh >> /etc/passwd'"  
su r00t -c "chown root:sys /tmp/passwd123 ;  
mv /tmp/passwd123 /etc/passwd ;  
chmod 644 /etc/passwd ; su"   
  
This will have the effect of adding an administrative user "r00t" to the  
  
system with no password, which allows for trivial privilege escalation.  
  
III. ANALYSIS  
  
Exploitation requires an attacker to have access to an account which has  
  
been granted usage of a binary in the /usr/sysadm/privbin directory. As   
root must explicitly allow such privileges, the impact of this   
vulnerability is lessened significantly. Exploitation does not require   
any knowledge of application internals, making exploitation trivial,   
even for unskilled attackers.   
  
IV. DETECTION  
  
iDEFENSE has confirmed the existence of this vulnerability in SGI IRIX   
version 6.5.22 (maintenance). It is suspected that previous and later   
versions of both the feature and maintenance revisions of IRIX 6.5 are   
also vulnerable.  
  
V. WORKAROUND  
  
Only grant runpriv privileges to trusted users with secure accounts.   
  
Alternately, remove the setuid and setgid bits from runpriv:   
  
chmod ug-s /usr/sysadm/bin/runpriv   
  
VI. VENDOR RESPONSE  
  
A vendor advisory for this vulnerability is to be posted at:  
  
http://www.sgi.com/support/security/advisories.html  
  
Vendor patch 7004 for IRIX 6.5.27 and 6.5.28 is available at:  
  
http://support.sgi.com/  
  
VII. CVE INFORMATION  
  
The Common Vulnerabilities and Exposures (CVE) project has assigned the  
name CAN-2005-2925 to this issue. This is a candidate for inclusion in  
the CVE list (http://cve.mitre.org), which standardizes names for  
security problems.  
  
VIII. DISCLOSURE TIMELINE  
  
09/08/2005 Initial vendor notification  
09/09/2005 Initial vendor response  
10/05/2005 Coordinated public disclosure  
  
IX. CREDIT  
  
The discoverer of this vulnerability wishes to remain anonymous.  
  
Get paid for vulnerability research  
http://www.idefense.com/poi/teams/vcp.jsp  
  
Free tools, research and upcoming events  
http://labs.idefense.com  
  
X. LEGAL NOTICES  
  
Copyright (c) 2005 iDEFENSE, Inc.  
  
Permission is granted for the redistribution of this alert  
electronically. It may not be edited in any way without the express  
written consent of iDEFENSE. If you wish to reprint the whole or any  
part of this alert in any other medium other than electronically, please  
email [email protected] for permission.  
  
Disclaimer: The information in the advisory is believed to be accurate  
at the time of publishing based on currently available information. Use  
of the information constitutes acceptance for use in an AS IS condition.  
There are no warranties with regard to this information. Neither the  
author nor the publisher accepts any liability for any direct, indirect,  
or consequential loss or damage arising from use of, or reliance on,  
this information.  
`