How to make authorization at once on 2 sites?

Question

symfony

There are two independent sites ( A and B )
you need to make sure that if a user opens site B and at the same time he is logged in on site A, then we authorize him automatically
. Site A has an API to ask if the user is logged in, and this API can be extended in accordance with needs
in my head 2 thoughts
1. when a user opens site A we generate a hash from some browser data like user-agent, os etc
when we open site B we generate a hash again and do ajax to site A try to check if the user is logged in with such a hash
2. when the user logs in to site A, open an invisible iframe href="siteB/login_me?email=" site B processes this request, check that the request is from a specific domain and the user logs in, then when the user opens site B, the browser will send the cookie received through iframe earlier
or how can this case be solved?

Answer 1

You can just insert a 1px image into site A from site B, and set the cookie.

Answer 2

If the sites are on the same domain, then do SSO .
If on different ones, then crutch some integration of sessions, work through the apishka or other crutches. Well, or like SSO, only use between different domains.
1. You don’t need to use any browser data, this is your inner kitchen, so deal with it on the backend. Not to mention the safety of such methods.
2. And definitely not an option through an iframe, for the same reason as p1.

Answer 3

You are all correct in your reasoning, I can say how almost all major sites do it. If a user visits a page that requires authorization, but there is no information about it (there is no cookie, for example), then first there is a redirect to a certain authorization domain, and he already has a cookie, and he, in turn, redirects back and passes to the URL some authorization token for the first domain.