[Java-project] [WEB SECURITY] Universal XSS with PDF files: highly dangerous

Jeff Williams jeff.williams at owasp.org
Thu Jan 4 23:42:24 EST 2007



I've implemented a Java EE filter that implements this algorithm.  Thanks to
Amit for detailing this for everyone.


I've tested with Firefox and it appears to work in all three cases.  The
deployment is simple, you just drop in the class file and add a few lines to
web.xml.  There are a few configuration options, like token name, timeout,
and encryption password.  Please help us make sure the implementation is








Jeff Williams, Chair

The OWASP Foundation <http://www.owasp.org/> 

"Dedicated to finding and fighting the causes of insecure software"




On 1/4/07, Amit Klein <aksecurity at gmail.com> wrote:



1. In private communication, Tom Spector observed that the cookie

doesn't add any significant security. In retrospect, I could have

omitted it completely. It's there as a remnant of a previous idea I had.

In other words, I see nothing wrong with the following, simpler and more

elegant algorithm ("Look ma - no cookie"):


IF the URL doesn't contain token_query, then:

  calculate X=encrypt_with_key(server_time, client_IP_address)

  redirect to file.pdf?token_query=X


ELSE IF the URL contains token_query, and

decrypt(token_query).IP_address==client_IP_address and


  serve the PDF resource as an in-line resource



  serve the PDF resource as a "save to disk" resource via a proper

choice of the Content-Type header (and/or an attachment, via




And big thanks to Tom who pointed this out.



> -Amit




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