fix(notes): fail closed when an unauthenticated request reaches owner-scoped routes (#4062)

* fix(notes): fail closed when an unauthenticated request reaches owner-scoped routes

The notes CRUD routes resolved the acting user with bare get_current_user().
A request that reached them with no identity (auth-middleware regression,
SSRF from a sibling service) came through as user=None — which every query
treats as the single-user mode: list all accounts' notes, read/update/
delete/pin/archive any row, reorder globally.

Resolve the owner through require_user() instead, which already encodes the
right policy: 401 when auth is configured, while the documented anonymous
modes (AUTH_ENABLED=false, LOCALHOST_BYPASS on loopback, unconfigured
first-run) still resolve to the single-user path. fire-reminder in the same
file already gated this way; the CRUD routes now match, and the inline
require_user import there is folded into the module import.

Extracted from #2940 (stabilization slice).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* test(notes): drive fail-closed test via ASGITransport, not sync TestClient

The focused fail-closed test hung at `TestClient(app).get(...)` on some
environments. Starlette's sync TestClient runs the app in a background
event-loop thread (anyio blocking portal) and then dispatches each sync
endpoint onto a second worker thread; that handshake deadlocks on certain
anyio/httpx/platform combos. The identity injection also used
BaseHTTPMiddleware (@app.middleware("http")), the other known TestClient
deadlock source.

Switch to the repo's existing httpx.ASGITransport + AsyncClient idiom so the
whole request runs on the test's own event loop (no portal thread, no
BaseHTTPMiddleware). Identity now comes from a pure-ASGI shim that writes the
same request.state fields the real auth middleware sets, and a non-loopback
client peer keeps require_user's loopback fall-throughs out of the picture.
Same assertions and coverage; production code unchanged.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

tests/test_notes_fail_closed_auth.py

@@ -0,0 +1,188 @@
+"""Owner-scoped note routes must fail closed when the request has no identity.
+
+The notes CRUD routes resolved the acting user with bare get_current_user().
+A request that reached them carrying no identity (auth-middleware regression,
+SSRF from a sibling service) therefore came through as user=None — and the
+queries treat None as the single-user mode, i.e. blanket access to every
+account's notes: list everything, read/update/delete/pin/archive any row,
+reorder globally.
+
+require_user() already encodes the correct policy — 401 when auth is
+configured, while the documented anonymous modes (AUTH_ENABLED=false,
+LOCALHOST_BYPASS on loopback, unconfigured first-run) still pass — and
+fire-reminder in the same file already used it. The CRUD routes now resolve
+the owner through it too.
+
+Test transport note: these drive the ASGI app through ``httpx.ASGITransport``
++ ``httpx.AsyncClient`` rather than ``starlette.testclient.TestClient``.
+TestClient runs the app inside a background event-loop thread spun up by
+``anyio.from_thread.start_blocking_portal`` and then dispatches each sync
+endpoint onto *another* worker thread; on some anyio/httpx/platform
+combinations that two-thread handshake deadlocks and ``TestClient(app).get(...)``
+simply hangs. ASGITransport runs the whole request on the test's own event
+loop — no portal thread, no BaseHTTPMiddleware — so the suite is portable.
+Identity is injected by a pure-ASGI shim that writes the same
+``request.state`` fields the real auth middleware sets.
+"""
+import uuid
+from types import SimpleNamespace
+
+import httpx
+import pytest
+from fastapi import FastAPI
+from sqlalchemy import create_engine
+from sqlalchemy.orm import sessionmaker
+from sqlalchemy.pool import NullPool
+
+import core.database as cdb
+from core.database import Note
+import routes.note_routes as nr
+
+
+# A deliberately NON-loopback peer. require_user has loopback fall-throughs
+# (unconfigured first-run, LOCALHOST_BYPASS); pinning a public-looking client
+# keeps every assertion below about the *configured-auth* path and not an
+# accidental loopback bypass — the same reason the old fixture leaned on
+# TestClient's non-loopback "testclient" host.
+_PEER = ("203.0.113.7", 54321)
+
+
+class _Identity:
+    """Pure-ASGI shim mirroring what the auth middleware writes onto
+    request.state. Pure-ASGI on purpose — it stays off Starlette's
+    BaseHTTPMiddleware + sync-TestClient path, the source of the
+    ``TestClient(app).get(...)`` hang. No x-test-user header => no identity,
+    the exact state an auth-middleware regression would produce."""
+
+    def __init__(self, app):
+        self.app = app
+
+    async def __call__(self, scope, receive, send):
+        if scope["type"] == "http":
+            headers = dict(scope.get("headers") or [])
+            state = scope.setdefault("state", {})
+            user = headers.get(b"x-test-user")
+            if user:
+                state["current_user"] = user.decode()
+            if headers.get(b"x-test-api-token"):
+                state["current_user"] = "api"
+                state["api_token"] = True
+        await self.app(scope, receive, send)
+
+
+def _temp_db(tmp_path):
+    """Note routes over a fresh temp DB; returns the session factory."""
+    engine = create_engine(
+        f"sqlite:///{tmp_path / 'notes.db'}",
+        connect_args={"check_same_thread": False},
+        poolclass=NullPool,
+    )
+    cdb.Base.metadata.create_all(engine)
+    return sessionmaker(bind=engine)
+
+
+def _build_app(factory, *, configured=True):
+    app = FastAPI()
+    app.state.auth_manager = SimpleNamespace(is_configured=configured)
+    app.include_router(nr.setup_note_routes())
+    return _Identity(app)
+
+
+def _client(app):
+    """AsyncClient over the ASGI app with a non-loopback peer. Caller drives
+    it inside ``async with``."""
+    transport = httpx.ASGITransport(app=app, client=_PEER)
+    return httpx.AsyncClient(transport=transport, base_url="http://notes.test")
+
+
+@pytest.fixture
+def env(monkeypatch, tmp_path):
+    """Configured-auth world: AUTH_ENABLED=true, auth_manager.is_configured,
+    no LOCALHOST_BYPASS. Identity comes only from the x-test-user header
+    (mirroring the auth middleware); no header => no identity, the exact state
+    an auth-middleware regression leaves behind. Seeds one note each for alice
+    and bob. Returns (app, factory)."""
+    factory = _temp_db(tmp_path)
+    monkeypatch.setattr(nr, "SessionLocal", factory)
+    monkeypatch.setenv("AUTH_ENABLED", "true")
+    monkeypatch.delenv("LOCALHOST_BYPASS", raising=False)
+
+    app = _build_app(factory)
+
+    db = factory()
+    db.add(Note(id="note-alice", owner="alice", title="a", content="x",
+                items='[{"text": "t", "done": false}]'))
+    db.add(Note(id="note-bob", owner="bob", title="b", content="y"))
+    db.commit()
+    db.close()
+    return app, factory
+
+
+async def test_no_identity_fails_closed_on_every_owner_scoped_route(env):
+    app, _ = env
+    async with _client(app) as c:
+        assert (await c.get("/api/notes")).status_code == 401
+        assert (await c.get("/api/notes/note-alice")).status_code == 401
+        assert (await c.put("/api/notes/note-alice", json={"title": "pwn"})).status_code == 401
+        assert (await c.delete("/api/notes/note-alice")).status_code == 401
+        assert (await c.post("/api/notes/note-alice/pin")).status_code == 401
+        assert (await c.post("/api/notes/note-alice/archive")).status_code == 401
+        assert (await c.post("/api/notes/note-alice/items/0/toggle")).status_code == 401
+        assert (await c.post("/api/notes/reorder", json={"ids": ["note-bob", "note-alice"]})).status_code == 401
+        assert (await c.post("/api/notes", json={"title": "ghost"})).status_code == 401
+
+
+async def test_no_identity_did_not_mutate_anything(env):
+    app, factory = env
+    async with _client(app) as c:
+        await c.put("/api/notes/note-alice", json={"title": "pwn"})
+        await c.post("/api/notes/note-alice/pin")
+        await c.delete("/api/notes/note-bob")
+    db = factory()
+    rows = {n.id: n for n in db.query(Note).all()}
+    db.close()
+    assert set(rows) == {"note-alice", "note-bob"}
+    assert rows["note-alice"].title == "a"
+    assert not rows["note-alice"].pinned
+
+
+async def test_authenticated_user_still_scoped_to_own_notes(env):
+    app, _ = env
+    alice = {"x-test-user": "alice"}
+    async with _client(app) as c:
+        listed = (await c.get("/api/notes", headers=alice)).json()["notes"]
+        assert [n["id"] for n in listed] == ["note-alice"]
+        assert (await c.get("/api/notes/note-alice", headers=alice)).status_code == 200
+        # Someone else's note stays a 404 (don't reveal it exists).
+        assert (await c.get("/api/notes/note-bob", headers=alice)).status_code == 404
+        assert (await c.put("/api/notes/note-alice", json={"title": "mine"}, headers=alice)).status_code == 200
+
+
+async def test_api_token_pseudo_user_is_rejected(env):
+    """Bearer tokens must use the scope-aware API routes (require_user's
+    existing contract), not slip into cookie-session routes as user 'api'."""
+    app, _ = env
+    async with _client(app) as c:
+        r = await c.get("/api/notes", headers={"x-test-api-token": "1"})
+    assert r.status_code == 403
+
+
+async def test_auth_disabled_keeps_single_user_mode_working(monkeypatch, tmp_path):
+    """AUTH_ENABLED=false is the operator's explicit anonymous mode: no
+    identity must still mean full single-user access (issue #622 contract),
+    even with a stale configured auth.json on disk."""
+    factory = _temp_db(tmp_path)
+    monkeypatch.setattr(nr, "SessionLocal", factory)
+    monkeypatch.setenv("AUTH_ENABLED", "false")
+
+    app = _build_app(factory)
+
+    db = factory()
+    db.add(Note(id="n1", owner=None, title="solo", content="x"))
+    db.commit()
+    db.close()
+
+    async with _client(app) as c:
+        assert [n["id"] for n in (await c.get("/api/notes")).json()["notes"]] == ["n1"]
+        assert (await c.put("/api/notes/n1", json={"title": "still mine"})).status_code == 200
+        assert (await c.post("/api/notes/n1/pin")).status_code == 200