1  URI.MungeSecretKey
 2  TYPE: string/null
 3  VERSION: 3.1.1
 4  DEFAULT: NULL
 5  --DESCRIPTION--
 6  <p>
 7      This directive enables secure checksum generation along with %URI.Munge.
 8      It should be set to a secure key that is not shared with anyone else.
 9      The checksum can be placed in the URI using %t. Use of this checksum
10      affords an additional level of protection by allowing a redirector
11      to check if a URI has passed through HTML Purifier with this line:
12  </p>
13  
14  <pre>$checksum === hash_hmac("sha256", $url, $secret_key)</pre>
15  
16  <p>
17      If the output is TRUE, the redirector script should accept the URI.
18  </p>
19  
20  <p>
21      Please note that it would still be possible for an attacker to procure
22      secure hashes en-mass by abusing your website's Preview feature or the
23      like, but this service affords an additional level of protection
24      that should be combined with website blacklisting.
25  </p>
26  
27  <p>
28      Remember this has no effect if %URI.Munge is not on.
29  </p>
30  --# vim: et sw=4 sts=4