directory traversal bug

[zbeng]

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:

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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:

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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("/"))

{

.

.

..