Donato Ferrante

Application: PWebServer
http://sourceforge.net/projects/pwebserver/

Version: 0.3.3

Bug: directory traversal bug

Author: Donato Ferrante
e-mail: fdonato (at) autistici (dot) org [email concealed]
web: www.autistici.org/fdonato

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1. Description
2. The bug
3. The code
4. The fix

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1. Description:
----------------

Vendor's Description:

"A simple Java multi-threaded Web Server that supports HTTP/1.0
protocol."

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2. The bug:
------------

The program doesn't check for malicious patterns like "/../", so an
attacker is able to see and download all the files on the remote
system simply using a browser.

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3. The code:
-------------

To test the vulnerability:

http://[host]:6789/../someFile

or:

http://[host]:6789/../../../../etc/passwd

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4. The fix:
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Bug fixed in the version 0.3.4.

If you want, you can use my following little patch, that should fix
the bug for this version of PWebServer:

..
.
.

( line: 99 )
fileName = tokenizedLine.nextToken(); // get the relative file name

/* start of patch */

boolean check = false;
for(int t = 0; t < fileName.length()-1 && check == false; t++){
if(fileName.charAt(t) == '.' && fileName.charAt(t+1) == '.')
check = true;
}
if(check == true)
fileName = "";

/* end of patch */

/* empty filename */
if(fileName.equals("") | fileName.equals("/"))
{

.
.
..

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