[UNIX] Yaws Webserver Code Disclosure

The following security advisory is sent to the securiteam mailing list, and can be found at the SecuriTeam web site: http://www.securiteam.com
- - promotion

The SecuriTeam alerts list - Free, Accurate, Independent.

Get your security news from a reliable source.
http://www.securiteam.com/mailinglist.html 

- - - - - - - - -



  Yaws Webserver Code Disclosure
------------------------------------------------------------------------


SUMMARY

 <http://yaws.hyber.org> Yaws is "a HTTP high performance 1.1 web server. 
Yaws is entirely written in Erlang furthermore it is a multi-threaded web 
server where one Erlang light weight process is used to handle each 
client".

Yaws server discloses the script's source whenever a NULL byte is appended 
to scripts filename.

DETAILS

Vulnerable Systems:
 * Yaws versions 1.55 and prior

Immune Systems:
 * Yaws versions 1.56

If a NULL byte is appended to the filename of a yaws script (.yaws), the 
yaws web server will return the page containing the source code of the 
according script. This flaw allows a malicious attacker to analyze the 
source code of the entire web application, which might result in the 
attacker gaining sensitive information like passwords.

The yaws homepage itself was vulnerable to the attack. Opening the link 
http://yaws.hyber.org/dynamic.yaws%00 in a browser resulted in the display 
of the following code (only the first couple of lines...):

<erl>
box(Str) ->
    {'div',[{class,"box"}],
     {pre, [], yaws_api:htmlize(Str)}}.

tbox(T) ->
    box(lists:flatten(io_lib:format("~p",[T]))).

..

Disclosure Timeline:
16.06.05 - Vendor notified
16.06.05 - Vendor response
16.06.05 - Patch available

Vendor Status:
Vendor was extremely fast to response and post a fix. You can download a 
patch from:  <http://yaws.hyber.org/yaws-1.55_to_1.56.patch> 
http://yaws.hyber.org/yaws-1.55_to_1.56.patch


ADDITIONAL INFORMATION

The information has been provided by  <mailto:[email protected]> 
Daniel Fabian.
The original article can be found at:  
<http://www.sec-consult.com/181.html> http://www.sec-consult.com/181.html



======================================== 


This bulletin is sent to members of the SecuriTeam mailing list. 
To unsubscribe from the list, send mail with an empty subject line and body to: [email protected] 
In order to subscribe to the mailing list, simply forward this email to: [email protected] 


==================== 
==================== 

DISCLAIMER: 
The information in this bulletin is provided "AS IS" without warranty of any kind. 
In no event shall we be liable for any damages whatsoever including direct, indirect, incidental, consequential, loss of business profits or special damages.