The way the flow goes now is this:
1. The user initiaties login via "Billing" in the gear menu.
2. That takes them to `/self-hosted-billing/` (possibly with a
`next_page` param if we use that for some gear menu options).
3. The server queries the bouncer to give the user a link with a signed
access token.
4. The user is redirected to that link (on `selfhosting.zulipchat.com`).
Now we have two cases, either the user is logging in for the first time
and already did in the past.
If this is the first time, we have:
5. The user is asked to fill in their email in a form that's shown,
pre-filled with the value provided inside the signed access token.
They POST this to the next endpoint.
6. The next endpoint sends a confirmation email to that address and asks
the user to go check their email.
7. The user clicks the link in their email is taken to the
from_confirmation endpoint.
8. Their initial RemoteBillingUser is created, a new signed link like in
(3) is generated and they're transparently taken back to (4),
where now that they have a RemoteBillingUser, they're handled
just like a user who already logged in before:
If the user already logged in before, they go straight here:
9. "Confirm login" page - they're shown their information (email and
full_name), can update
their full name in the form if they want. They also accept ToS here
if necessary. They POST this form back to
the endpoint and finally have a logged in session.
10. They're redirected to billing (or `next_page`) now that they have
access.
For the last form (with Full Name and ToS consent field), this pretty
shamelessly re-uses and directly renders the
corporate/remote_realm_billing_finalize_login_confirmation.html
template. That's probably good in terms of re-use, but calls for a
clean-up commit that will generalize the name of this template and the
classes/ids in the HTML.
Analogical to the more complex mechanism implemented for the RemoteRealm
flow in a previous commit in
authenticated_remote_realm_management_endpoint.
As explained in the code comment, this is much easier because:
In this flow, we can only redirect to our local "legacy server flow
login" page. That means that we can do it universally whether the user
has an expired
identity_dict, or just lacks any form of authentication info at all -
there are no security concerns since this is just a local redirect.
Implements a nice redirect flow to give a good UX for users attempting
to access a remote billing page with an expired RemoteRealm session e.g.
/realm/some-uuid/sponsorship - perhaps through their browser
history or just their session expired while they were doing things in
this billing system.
The logic has a few pieces:
1. get_remote_realm_from_session, if the user doesn't have a
identity_dict will raise RemoteBillingAuthenticationError.
2. If the user has an identity_dict, but it's expired, then
get_identity_dict_from_session inside of get_remote_realm_from_session
will raise RemoteBillingIdentityExpiredError.
3. The decorator authenticated_remote_realm_management_endpoint
catches that exception and uses some general logic, described in more
detail in the comments in the code, to figure out the right URL to
redirect them to. Something like:
https://theirserver.example.com/self-hosted-billing/?next_page=...
where the next_page param is determined based on parsing request.path
to see what kind of endpoint they're trying to access.
4. The remote_server_billing_entry endpoint is tweaked to also send
its uri scheme to the bouncer, so that the bouncer can know whether
to do the redirect on http or https.
This does two important things:
1. Fix return type of get_identity_dict_from_session to correctly be
Optional[Union[RemoteBillingIdentityDict, LegacyServerIdentityDict]].
RemoteBillingIdentityDict is the type in the 8.0+ auth flow,
LegacyServerIdentityDict is the type in old servers flow, where only
the server uuid info is available.
2. The uuid key used in request.session["remote_billing_identities"]
should be explicitly namespaced depending on which flow and type
we're
dealing with - to avoid confusion in case of collisions between a
realm and server that have the same UUID. Such a situation should not
occur naturally and I haven't come up with any actual exploitation
ideas that could utilize this by manipulating your server/realm
uuids, but it's much easier to just not think about such collision
security implications by making them impossible.
We pass `next` parameter with /self-hosted-billing to redirect
users to the intended page after login.
Fixed realm_uuid incorrectly required in remote_realm_upgrade_page.
