Calling a Google Apps Script web app with access token

Question

I need to execute a GAS service on behalf of a user that is logged to my system. So I have her/his access token. I would like somehow to transfer the token to the web app and without having to authorize again the user to use it for some activities. Can this be accomplished? Thank you.

EDIT: I think I didn't explain right what I try to accomplish. Here is the work flow I try to achieve:

1. We authorize a user visiting our website using OAuth2 and Google;
2. We get hold of her/his access token that Google returns;
3. There is a Google Apps Script web app that is executed as the user running the web app;
4. We want to call this app (3) by providing the access token (2) so Google not to ask again for authorization;
5. Actually, we want to call this app (3) not by redirecting the user to it but by calling it as a web service.

Thanks

Answer 1

I found a way! Just include the following header in the request:

Authorization: Bearer <user's_access_token>