The OpenId plugin does not seem to work bvehind a proxy. I have configured the proxy in the jenkins plugin settings (jenkins can now download plugins via proxy), added JAVA_ARGS="-Dhttp.proxyHost=proxy1 -Dhttp.proxyPort=3128" to /etc/defaults/jenkins (and verified via ps -Af | grep jenkins, exported $http_proxy from /etc/profile, but nothing seems to work.
I have found the following hint: http://code.google.com/p/openid4java/wiki/ConsumerForwardProxy - but in the plugin source code there is no such configuration before the instantiation of the ConsumerManager (see OpenIdLoginService.java, line 52). I don't know if there's some magic there already that makes this obsolete and works if used correctly, but unfortunately it does not work out of the box in my case. Id would be nice to have a mechanism that observes any of the standard configurations mentioned above (preferrably the one inside hudson, because this is the one that is most likely correct once the open id plugin is installed), or at least a setting for the proxy in the open id plugin itself.