c# - Is Forms Authentication Ticket Decryption possible with PHP?

Question

I'm a PHP developer who knows almost nothing about .NET. I've been asked by the .NET guys at work to translate .NET code that decrypts an authentication ticket into PHP so that the PHP code can then set the appropriate session variables for my application to run. Is this even possible? I'm staring at the code and it's baffling me. I'll keep trying if someone can tell me it's not a waste of time for some reason I don't even know. Thanks for any help!

Additional info: Can I even grab the ticket with PHP in the first place?

Answer 1

First off, open your machine.config and add in a machinekey entry. Set the decryption key and validation key according to a randomly generated ones from a machinekey generator for aspnet 2.0.

Be sure to use the default's, ie. AES and SHA1. Now that you have the AES decrypt key, store it somewhere because you are going to need it on the php side. In your dot net app, go into the web.config and get the forms auth cookie name, usually something like .ASPXAUTH

Now go to the PHP side. Download and set up an AES encryption library, like this one, http://phpseclib.sourceforge.net/documentation/

Then in PHP you can do something like this (this uses the phpsec lib):

set_include_path(get_include_path() . PATH_SEPARATOR . 'phpseclib');
include('Crypt/AES.php');

$authCookie = $_COOKIE['_ASPXAUTH'];

echo $authCookie;

$aes = new Crypt_AES();

$aes->setKey('BCDCBE123654F3E365C24E0498346EB95226A307857B9BDE8EBA6198ACF7F03C');

echo $aes->decrypt($authCookie);

Now what ends up coming out is going to first be pm + the SHA1 hash + a byte representation of the auth ticket. You must convert the serialized bytes to a string to make it readable. Can someone else iluminate on that last step?