test(auth): login rate limit

backend/tests/test_auth_login_rate_limit.py

@@ -0,0 +1,81 @@
+"""Login rate limit: 5 fails / 5 min per username."""
+
+from __future__ import annotations
+
+import pytest
+from fastapi.testclient import TestClient
+from sqlalchemy import delete
+
+from cyclone.api import app
+from cyclone.auth import rate_limit, users
+from cyclone.db import Session as DbSession
+from cyclone.db import SessionLocal, User
+
+
+@pytest.fixture(autouse=True)
+def _clear():
+    with SessionLocal()() as db:
+        db.execute(delete(DbSession))
+        db.execute(delete(User))
+        db.commit()
+    # Reset the in-memory rate-limit counter so a previous test's 5
+    # failures don't poison this test. The plan recipe calls this out.
+    rate_limit.reset("victim")
+    yield
+    with SessionLocal()() as db:
+        db.execute(delete(DbSession))
+        db.execute(delete(User))
+        db.commit()
+    rate_limit.reset("victim")
+
+
+def test_5_fails_then_429():
+    with SessionLocal()() as db:
+        users.create(db, username="victim", password="hunter2hunter2", role="user")
+    client = TestClient(app)
+    for _ in range(5):
+        r = client.post(
+            "/api/auth/login",
+            json={"username": "victim", "password": "WRONG"},
+        )
+        assert r.status_code == 401
+    # 6th should be 429.
+    r = client.post(
+        "/api/auth/login",
+        json={"username": "victim", "password": "WRONG"},
+    )
+    assert r.status_code == 429
+    assert "Retry-After" in r.headers
+    # And the module-level helper confirms we're now over the threshold.
+    assert rate_limit.check("victim") > 0
+
+
+def test_successful_login_resets_counter():
+    with SessionLocal()() as db:
+        users.create(db, username="victim", password="hunter2hunter2", role="user")
+    client = TestClient(app)
+    for _ in range(4):
+        r = client.post(
+            "/api/auth/login",
+            json={"username": "victim", "password": "WRONG"},
+        )
+        assert r.status_code == 401
+    # Successful login — should reset the counter.
+    r = client.post(
+        "/api/auth/login",
+        json={"username": "victim", "password": "hunter2hunter2"},
+    )
+    assert r.status_code == 200
+    # Counter reset — 5 more fails allowed.
+    for _ in range(5):
+        r = client.post(
+            "/api/auth/login",
+            json={"username": "victim", "password": "WRONG"},
+        )
+        assert r.status_code == 401
+    # 6th is now throttled.
+    r = client.post(
+        "/api/auth/login",
+        json={"username": "victim", "password": "WRONG"},
+    )
+    assert r.status_code == 429