Bitrix->Moodle end-to-end authorization?

Question

PHP

Good day! As part of my own development, I'm trying to implement pass-through authorization (SSO) between sites on the same server. Website1(Bitrix) Website2(Moodle). The authorization algorithm is as follows, the user logged in to Bitrix and clicked on the button to switch to the moodle and immediately logged into his account, but not vice versa. That is, so that the moodle uses only Bitrix accounts, and not its own. I'm trying to implement using the Oauth2.0 protocol using an external database that stores data about users and tokens. Here it would be desirable to see examples though any implementation.