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itcp advisory 3 advisoriesit-checkpoint.net
http://www.it-checkpoint.net/advisory/3.html
March 10th, 2002
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Marcus S. Xenakis "directory.php" allows arbitrary code execution
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Affected program : directory.php
Vendor: Marcus S. Xenakis (www.xenakis.net)
Vulnerability-Class: Arbitrary Code execution
OS specific : Yes: *nix
Problem-Type : remote

SUMMARY
Marcus S. Xenakis developped some quite nice PHP-Scripts to support some
works with shell commands.
Description of "directory.php" (taken from the source of the script):

// This simple PHP script only runs on a UNIX server. //
// It is based on the "ls" command. //
// It should reside in your web server root directory //
// //
// This program reads the directory based upon the //
// a passed paramter (parm) or the current directory //
// the program resides in if parm is null. //

This script could cause a headache for some admins itself because it allows
viewing arbitrary directories.
Futhermore it allows arbitrary code execution caused by missing filters for
"dangerous characters" (like ";"). This is quite the same as the "Unix
Manual PHP Script"-Bug of the same author, which was discovered and fixed
recently.

DETAILS
Marcus S. Xenakis PHP-Scripts very often use simple calls of shell commands:

exec("ls -la $dir",$lines,$rc);

This is quite easy programming but doesn't deal with dangers, that calls of
shell commands can bring.

Bug analysis: Missing filters for Characters like ";"

Impact: It is possible to execute arbitrary code with the rights of the
HTTP-Daemon

Exploit:
In the contrary to the "Unix Manual PHP Script" this script doesn't offer a
form where you can enter the commands. Because of that you have to call the
script directly including the parameter and command you want to execute.

http://www.vulnerableserver.com/directory.php?dir=%3Bmore%20/etc/passwd
will show you the Password File.

http://www.vulnerableserver.com/directory.php?dir=%3Bps+-aux
will show you all running processes.

Solution: Implement a filter which filters dangerous characters, especially
";"

ADDITIONAL INFORMATION
Vendor has been contacted.

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BlueScreen / Florian Hobelsberger (UIN: 101782087)
Member of:
http://www.IT-Checkpoint.net
http://www.Hackeinsteiger.de
http://www.DvLdW.de.vu

http://www.bugreplace.de
We work for your security

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