🔒️(backend) reject inactive users in resource server backend

The resource server backend returned any user matching the token's
`sub` claim without checking `User.is_active`. The upstream lasuite
backend only validates the token's introspection `active` claim, so a
deactivated Django account kept API access until its token expired.

Raise `SuspiciousOperation` in `get_or_create_user` when the user is
inactive, which the authentication class turns into a 401, consistent
with `BaseJWTAuthentication`. Add unit and end-to-end tests.

CHANGELOG.md

@@ -8,17 +8,18 @@ and this project adheres to
 
 ## [Unreleased]
 
-### Fixed
-
-- 🐛(backend) acknowledge unknown LiveKit webhook events instead of 422
-- 🔒️(backend) enforce display name setting on rename API
-
 ### Changed
 
 - 📈(frontend) include LiveKit SIDs in the connection analytics event
 - 🔇(backend) silence expected 401 warnings on /me
 - 🔇(backend) silence noisy request summary info logs
 
+### Fixed
+
+- 🐛(backend) acknowledge unknown LiveKit webhook events instead of 422
+- 🔒️(backend) enforce display name setting on rename API
+- 🔒️(backend) reject inactive users in resource server backend
+
 ## [1.31.0] - 2026-09-08
 
 ### Added

src/backend/core/external_api/authentication.py

@@ -286,6 +286,10 @@ class ResourceServerBackend(LaSuiteBackend):
         if user is None and settings.OIDC_CREATE_USER:
             user = self.create_user(sub)
 
+        if user is not None and not user.is_active:
+            logger.warning("Inactive user attempted authentication: %s", user.pk)
+            raise SuspiciousOperation("User account is disabled.")
+
         return user
 
     def create_user(self, sub):

src/backend/core/tests/test_external_api_authentication.py

@@ -0,0 +1,96 @@
+"""Tests for the external API ResourceServerBackend."""
+
+from django.core.exceptions import SuspiciousOperation
+
+import pytest
+import responses
+from rest_framework.test import APIClient
+
+from core.external_api.authentication import ResourceServerBackend
+from core.factories import UserFactory
+from core.models import User
+
+pytestmark = pytest.mark.django_db
+
+
+def _payload(sub):
+    return {"sub": sub, "active": True, "scope": "lasuite_meet", "client_id": "app"}
+
+
+def test_resource_server_backend_get_or_create_user_active():
+    """An existing active user matching the sub should be returned."""
+
+    user = UserFactory()
+
+    result = ResourceServerBackend().get_or_create_user(
+        access_token="token", id_token=None, payload=_payload(user.sub)
+    )
+
+    assert result == user
+
+
+def test_resource_server_backend_get_or_create_user_inactive():
+    """An inactive user should be rejected even with a valid token."""
+
+    user = UserFactory(is_active=False)
+
+    with pytest.raises(SuspiciousOperation, match="User account is disabled."):
+        ResourceServerBackend().get_or_create_user(
+            access_token="token", id_token=None, payload=_payload(user.sub)
+        )
+
+
+def test_resource_server_backend_get_or_create_user_creates(settings):
+    """An unknown sub should create an active user when OIDC_CREATE_USER is set."""
+
+    settings.OIDC_CREATE_USER = True
+
+    result = ResourceServerBackend().get_or_create_user(
+        access_token="token", id_token=None, payload=_payload("new-sub")
+    )
+
+    assert result.sub == "new-sub"
+    assert result.is_active is True
+    assert User.objects.filter(sub="new-sub").exists()
+
+
+def test_resource_server_backend_get_or_create_user_no_creation(settings):
+    """An unknown sub should return None when OIDC_CREATE_USER is unset."""
+
+    settings.OIDC_CREATE_USER = False
+
+    result = ResourceServerBackend().get_or_create_user(
+        access_token="token", id_token=None, payload=_payload("new-sub")
+    )
+
+    assert result is None
+    assert not User.objects.filter(sub="new-sub").exists()
+
+
+@responses.activate
+def test_api_rooms_list_resource_server_inactive_user(settings):
+    """End to end: a valid introspected token for an inactive user should get 401."""
+
+    settings.OIDC_OP_INTROSPECTION_ENDPOINT = "https://oidc.example.com/introspect"
+    settings.OIDC_OP_URL = "https://oidc.example.com"
+
+    user = UserFactory(is_active=False)
+
+    responses.add(
+        responses.POST,
+        "https://oidc.example.com/introspect",
+        json={
+            "iss": "https://oidc.example.com",
+            "active": True,
+            "sub": user.sub,
+            "scope": "openid lasuite_meet rooms:list",
+            "client_id": "app",
+        },
+    )
+
+    client = APIClient()
+    client.credentials(HTTP_AUTHORIZATION="Bearer rs-token")
+    response = client.get("/external-api/v1.0/rooms/")
+
+    assert response.status_code == 401
+    assert "login failed" in str(response.data).lower()