I used vouch-proxy with nginx for something like this. The nginx auth_request module authenticates each request against vouch-proxy before it executes the prox

I used vouch-proxy with nginx for something like this. The nginx auth_request module authenticates each request against vouch-proxy before it executes the proxy_pass. Vouch-proxy can be configured to authenticate users against google apps or other oauth/iodc providers. And there are some options to pass along username, groups or other data as headers to the proxied service.