Wikimedia Bugzilla is closed!

Picture this situation:

LocalSettings.php:

    # Deny all OpenIDs except the ones we allow:
    $wgOpenIDConsumerDenyByDefault = true;
    $wgOpenIDConsumerAllow = array("@^(http://)?mydomain.com@");

Someone enters in http://mydomain.com/ - validation passes - all is good.

Then, then take the URL that their browser is redirected to (I used Firefox's Live HTTP Headers plugin to see this), copy the OpenID parameters off it, and then suffix them onto a server which they have an account on (say, https://login.launchpad.net/+openid).

Voila, I am logged into this supposedly-restricted wiki with an OpenID that fails the consumer allow test.

Two things come to mind here:

  - Aren't OpenID requests meant to be signed, so they can't be tampered with in this way?
  - You should validate after the OpenID is returned, not (just) before. 

For example, I have solved this by adding to SpecialOpenIDFinish.body.php 

			 case Auth_OpenID_SUCCESS:
				// This means the authentication succeeded.
				$openid = $response->getDisplayIdentifier();
				// Check we have been given an identifier we accept.
				if (!$this->canLogin($openid_url)) {
					$wgOut->showErrorPage('openidpermission', 'openidpermissiontext');
					return;
				}

However, I don't think this will stop a OP that is prepared to issue an ID in any name - only signing will fix that.