Rosiello Security - Eterm-LibAST Advisory

[angelo@xxxxxxxxxxxx]

             Eterm-LibAST Advisory

              Rosiello Security
           http://www.rosiello.org


I. BACKGROUND

Eterm (http://www.eterm.org) is a color vt102 terminal emulator intended as an 
xterm(1) replacement. It is designed with a Freedom of Choice philosophy, 
leaving as much power, flexibility, and freedom as possible in the hands of the 
user. It is designed to look good and work well, but takes a feature-rich 
approach rather than one of minimalism. Eterm uses Imlib for advanced graphic 
abilities and includes LibAST.


II. DESCRIPTION

Eterm when builded links to LibAST. A stack overflow vulnerability exists in 
LibAST that allows an attacker to execute commands with user group ?utmp?. The 
vulnerability is triggered when using an alternative configuration file name by 
the '-X' option. In this case Eterm will call conf_find_file() in conf.c from 
LibAST. Here is where vulnerability takes place at:

if (dir) {

strcpy(name, dir);

strcat(name, "/");

strcat(name, file);

}


III. ANALISYS

By exploiting this vulnerability an attacker can gain control of the return 
address of the executing function allowing arbitrary code execution with "utmp" 
group privileges.


IV. DETECTION

All vulnerable versions of Eterm using LibAST prior to 0.7 are vulnerable.


V. WORKAROUND

Rosiello Security is currently unaware of any workaround for this issue.


VI. VENDOR RESPONSE

The vendor has released the following new package of LibAST to fix the problem:

http://www.eterm.org/download/libast-0.7.tar.gz


VII. CVE INFORMATION

The Common Vulnerabilities and Exposures (CVE) project has assigned the name 
CVE-2006-0224 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

15/01/2006 - Initial Vendor Contact

16/01/2006 ? Initial Vendor Response

23/01/2006 ? Coordinated public disclosure


IX. CREDITS

Johnny Mast from Rosiello Security (http://www.rosiello.org) is credited with 
discovering this vulnerability.

Rosiello Security home page: http://www.rosiello.org

You can find Rosiello Security's members in our irc server: irc.rosiello.net 
#rosiello

Visit our latest project Obsidis where you can find free security white papers: 
http://www.obsidis.org


X. LEGAL NOTICES

Copyright © 2006 Rosiello Security

Permission is granted for the redistribution of this alert electronically. It 
may not be edited in any way without the express written consent of Rosiello 
Security. If you wish to reprint the whole or any part of this alert in any 
other medium other than electronically, please email angelo@xxxxxxxxxxxx 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.


Exploit: http://www.rosiello.org/archivio/eterm-exploit.c  (Ubuntu with no 
random stack)