Pass SSO IdP information to spam checker's registration function (#9626)

Fixes https://github.com/matrix-org/synapse/issues/9572

When a SSO user logs in for the first time, we create a local Matrix user for them. This goes through the register_user flow, which ends up triggering the spam checker. Spam checker modules don't currently have any way to differentiate between a user trying to sign up initially, versus an SSO user (whom has presumably already been approved elsewhere) trying to log in for the first time.

This PR passes `auth_provider_id` as an argument to the `check_registration_for_spam` function. This argument will contain an ID of an SSO provider (`"saml"`, `"cas"`, etc.) if one was used, else `None`.

1 files changed, 2 insertions, 2 deletions

diff --git a/synapse/handlers/register.py b/synapse/handlers/register.py

index cd001e87c7..1abc8875cb 100644
--- a/synapse/handlers/register.py
+++ b/synapse/handlers/register.py
@@ -198,8 +198,7 @@ class RegistrationHandler(BaseHandler):
               admin api, otherwise False.
             user_agent_ips: Tuples of IP addresses and user-agents used
                 during the registration process.
-            auth_provider_id: The SSO IdP the user used, if any (just used for the
-                prometheus metrics).
+            auth_provider_id: The SSO IdP the user used, if any.
         Returns:
             The registered user_id.
         Raises:
@@ -211,6 +210,7 @@ class RegistrationHandler(BaseHandler):
             threepid,
             localpart,
             user_agent_ips or [],
+            auth_provider_id=auth_provider_id,
         )
 
         if result == RegistrationBehaviour.DENY: