✨ [#99] Implement IDP availability check

Optionally, the OIDC init view can check the identity provider
availability before redirecting the user to it.

mozilla_django_oidc_db/views.py

@@ -10,12 +10,14 @@
 from django.utils.http import url_has_allowed_host_and_scheme
 from django.views.generic import TemplateView
 
+import requests
 from mozilla_django_oidc.views import (
     OIDCAuthenticationCallbackView,
     OIDCAuthenticationRequestView as _OIDCAuthenticationRequestView,
 )
 
 from .config import get_setting_from_config, store_config
+from .exceptions import OIDCProviderOutage
 from .models import OpenIDConnectConfig, OpenIDConnectConfigBase
 
 logger = logging.getLogger(__name__)
@@ -181,7 +183,8 @@ def get(
         if not self.allow_next_from_query:
             self._validate_return_url(request, return_url=return_url)
 
-        self.check_idp_availability()
+        if self.get_settings("OIDCDB_CHECK_IDP_AVAILABILITY", False):
+            self.check_idp_availability()
 
         response = super().get(request, *args, **kwargs)
 
@@ -241,9 +244,30 @@ def check_idp_availability(self) -> None:
         """
         Hook for subclasses.
 
-        Raise :class:`OIDCProviderOutage` if the Identity Provider is not available.
+        Raise :class:`OIDCProviderOutage` if the Identity Provider is not available,
+        which your application code needs to handle.
+
+        The default implementation checks if the endpoint has a status code < 401.
         """
-        pass
+        endpoint = self.OIDC_OP_AUTH_ENDPOINT
+        try:
+            # Verify that the identity provider endpoint can be reached. This is where
+            # the user ultimately gets redirected to.
+            #
+            # 5 seconds wait time is probably already too long for a good user
+            # experience, but we don't want to be *too* aggressive.
+            response = requests.get(endpoint, timeout=5.0)
+            # some IDPs have been observed to return HTTP 400 because of the missing
+            # query params
+            if response.status_code > 400:
+                response.raise_for_status()
+        except requests.RequestException as exc:
+            logger.info(
+                "OIDC provider endpoint '%s' could not be retrieved",
+                endpoint,
+                exc_info=exc,
+            )
+            raise OIDCProviderOutage("Identity provider appears to be down.") from exc
 
     def get_extra_params(self, request: HttpRequest) -> dict[str, str]:
         """

tests/test_init_flow.py

@@ -8,6 +8,8 @@
 
 import pytest
 
+from mozilla_django_oidc_db.exceptions import OIDCProviderOutage
+
 
 @pytest.mark.oidcconfig(
     oidc_op_authorization_endpoint="http://localhost:8080/openid-connect/auth"
@@ -46,3 +48,26 @@ def test_keycloak_idp_hint_via_settings(dummy_config, settings, client):
 
     query = parse_qs(parsed_url.query)
     assert query["kc_idp_hint"] == ["keycloak-idp1"]
+
+
+def test_check_idp_availability_not_available(
+    dummy_config, settings, client, requests_mock
+):
+    settings.OIDCDB_CHECK_IDP_AVAILABILITY = True
+    requests_mock.get("https://mock-oidc-provider:9999/oidc/auth", status_code=503)
+    start_url = reverse("oidc_authentication_init")
+
+    with pytest.raises(OIDCProviderOutage):
+        client.get(start_url)
+
+
+def test_check_idp_availability_available(
+    dummy_config, settings, client, requests_mock
+):
+    settings.OIDCDB_CHECK_IDP_AVAILABILITY = True
+    requests_mock.get("https://mock-oidc-provider:9999/oidc/auth", status_code=400)
+    start_url = reverse("oidc_authentication_init")
+
+    response = client.get(start_url)
+
+    assert response.status_code == 302