Fortinet FortiWeb Web Application Firewall – Policy Bypass
BINAR10 Report on Fortinet Fortiweb Findings 02/05/2012 - Fortinet FortiWeb Web Application Firewall Policy Bypass - ============================================================ 1) Affected Product Fabricant: Fortinet Product name: FortiWeb Version: Latest update to Tue, 2 May 2012 Type: Web Application Firewall Product URL: http://www.fortinet.com/products/fortiweb/index.html 2) Description of the Findings BINAR10 has found a policy bypass occurrence when large size data is sent in POST (data) or GET request. 3) Technical Details 3.1. POST Request Example When is appended to a POST request any padding data that surpasses 2399 bytes, the WAF do not inspect the data sent and the request hits directly the application. This should occur when the product is not configured to block malformed requests, but this feature also check the POST size limit, blocking the request if it surpass a fixed limit, therefore is likely that is being disabled due to application requirements in medium size forms. The response is also not verified by the WAF and information disclosure occurs with details of the infrastructure. This bypass could be used to inject different types of vectors, as is shown in the example only is needed to append a new variable at the end of the POST data filled with arbitrary data that exceeds 2399 bytes. ---POST example POST /<path>/login-app.aspx HTTP/1.1 Host: <host> User-Agent: <any valid user agent string> Accept-Encoding: gzip, deflate Connection: keep-alive Content-Type: application/x-www-form-urlencoded Content-Length: <the content length must be at least 2399 bytes> var1=datavar1&var2=datavar12&pad=<random data to complete at least 2399 bytes> 3.2. GET Requests The same issue with POST Request but it could be done through the sending arbitrary data at the end of the URL. --GET example http://<domain>/path?var1=vardata1&var2=vardata2&pad=<large arbitrary data> 4. Validation Required It requires the validation of other researchers who have access to product. 5. Time Table 04/27/2012 - Vendor notified. 04/27/2012 - Vendor response, requiring some tests. 05/02/2012 - Vendor indicates that this is a configuration problem and not a product vulnerability. 6. Credits Geffrey Velasquez <geffrey at gmail.com> at BINAR10 S.A.C. |