I don't see it documented properly anywhere, but Hybridauth allows providing curl proxy settings via config.

I believe there is no way to set curl settings globally.

Setting the proxy for curl in the hybridauth code worked, thanks.

However, the social login process does not work properly yet. 

- when using google the user is directed to google, logs in, is being redirected to the elgg "complete registration" page and when he tries to submit the form, the error "Form is missing __token or __ts fields" shows up. 

- when using facebook the user is directed to facebook, logs in, is being redirected to elgg and confronted with the error "Facebook returned an invalid user id".

- when using twitter the user is directed to twitter, logs in, is being redirected to elgg and gets the error "Twitter has returned an error".