I do not find how to make this extension work with MW1.27. The fix proposed here (try to use $wgMainCacheType = CACHE_DB
or use a different SimpleSAMLphp store type) does not work for me. I use SImpleSamlPHP version 1.14.12, the authentication works when testing but in combination with the extension I always get the "User cannot be authenticated." message.
Could someone help ?