Re: Controlling access to pdf/doc files

[Blasted <blasted () tech9security com>]

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You could just have the application,
for example if it was in php,
open (fopen()) the file 
(which is stored outside the webroot),
then print some headers for content type etc,
and have it spit out (fpassthru()) the file.
Then you would check the session etc as normal
within the script/application.

The user would see it as if they downloaded the file directly,
but no one could access the file directly.

- -david

On Tuesday 24 February 2004 09:21, Sangita Pakala wrote:
> Hi,
>
> Could I have the list's thoughts on an answer we are preparing for the
> next version of the AppSec FAQ at OWASP.
>
> Question - How can I ensure my application allows only authenticated
> users access to files like *.pdf or *.doc?
>
> Issue - Suppose a web site, say a bank site, displays the user's account
> statement as a .doc file. What if someone tries to access this file by
> typing its full URL into the address bar? How does the application check
> whether the user trying to access the file is the authenticated user and
> that the session has not expired?
>
> Solution - One solution is to have a random number for the name of the
> file or the folder containing it. This random number could even be
> related to the session token of the user. This file/folder should then
> be deleted as soon as the user's session has expired.
>
> Are there better methods available to address this issue? Can the web
> server run a server side program to verify the session token before
> serving the final GET request for the file?
>
>
> Thanks,
> Sangita.
>
> OWASP AppSec FAQ
> http://www.owasp.org/documentation/appsecfaq
>
> Paladion Networks
> http://www.paladion.net
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