thoughtsync/tests/test_ratelimit.py

"""The credential throttle. DB-free, like the rest of this suite.

The window itself is exercised directly with an injected clock, so nothing here
sleeps: a 15-minute window tested in real time is a test nobody runs twice.

The routes are exercised only as far as they get WITHOUT a database — a throttled
request returns 429 before any session is opened, which is the whole point of
checking the limit before the password. The happy path can't be reached here and is
not pretended at.
"""
import pytest

from thoughtsync import ratelimit
from thoughtsync.app import create_app
from thoughtsync.ratelimit import SlidingWindow


@pytest.fixture(autouse=True)
def _clean_counters():
    ratelimit.reset_all()
    yield
    ratelimit.reset_all()


@pytest.fixture
def app():
    return create_app()


def test_under_the_limit_is_not_blocked():
    w = SlidingWindow(limit=3, window_s=60)
    for i in range(3):
        assert w.retry_after("k", now=i) is None
        w.record("k", now=i)
    assert w.retry_after("k", now=3) is not None


def test_window_slides_rather_than_resetting():
    w = SlidingWindow(limit=2, window_s=60)
    w.record("k", now=0)
    w.record("k", now=30)
    assert w.retry_after("k", now=31) is not None
    # The 0s hit falls out at t=60, which frees exactly one slot — the 30s hit is
    # still inside the window, so this is a slide and not a reset.
    assert w.retry_after("k", now=61) is None
    w.record("k", now=61)
    assert w.retry_after("k", now=62) is not None


def test_retry_after_points_past_the_oldest_hit():
    w = SlidingWindow(limit=1, window_s=100)
    w.record("k", now=10)
    wait = w.retry_after("k", now=40)
    # The hit at t=10 leaves the window at t=110, i.e. 70s away. Rounded up, never
    # under-reported — a client that waits exactly this long must not be refused
    # again.
    assert wait is not None
    assert 70 <= wait <= 72
    assert w.retry_after("k", now=40 + wait) is None


def test_keys_are_counted_separately():
    w = SlidingWindow(limit=1, window_s=60)
    w.record("a", now=0)
    assert w.retry_after("a", now=1) is not None
    assert w.retry_after("b", now=1) is None


def test_forget_clears_one_key():
    w = SlidingWindow(limit=1, window_s=60)
    w.record("a", now=0)
    w.record("b", now=0)
    w.forget("a")
    assert w.retry_after("a", now=1) is None
    assert w.retry_after("b", now=1) is not None


def test_bucket_count_is_bounded(monkeypatch):
    # An attacker rotating a forged X-Forwarded-For must not be able to grow this
    # dict without limit — the limiter cannot become the exhaustion it prevents.
    monkeypatch.setattr(ratelimit, "MAX_BUCKETS", 8)
    w = SlidingWindow(limit=5, window_s=60)
    for i in range(50):
        w.record(f"addr-{i}", now=i)
    assert len(w._hits) <= 8


async def test_login_starts_refusing(app):
    client = app.test_client()
    body = {"email": "someone@example.com", "password": "wrong-password"}
    # Pre-load the account's counter to its limit rather than posting that many
    # times: every real attempt would need a database to reach the password check.
    for i in range(ratelimit.ACCOUNT_LIMIT):
        ratelimit.sign_in_by_account.record("someone@example.com", now=float(i))
    resp = await client.post("/api/auth/login", json=body)
    assert resp.status_code == 429
    assert resp.headers.get("Retry-After")
    # The refusal says nothing about whether that account exists.
    assert "someone@example.com" not in (await resp.get_data(as_text=True))


async def test_device_login_shares_the_account_counter(app):
    client = app.test_client()
    for i in range(ratelimit.ACCOUNT_LIMIT):
        ratelimit.sign_in_by_account.record("someone@example.com", now=float(i))
    resp = await client.post(
        "/api/auth/device-login",
        json={"email": "someone@example.com", "password": "wrong-password"},
    )
    # Same budget as /login — otherwise guessing just moves to the route that hands
    # out a long-lived bearer token.
    assert resp.status_code == 429


async def test_register_is_throttled_by_address(app):
    client = app.test_client()
    for i in range(ratelimit.REGISTER_LIMIT):
        ratelimit.register_by_address.record("203.0.113.9", now=float(i))
    resp = await client.post(
        "/api/auth/register",
        json={"email": "new@example.com", "password": "a-long-enough-password"},
        headers={"X-Forwarded-For": "203.0.113.9"},
    )
    assert resp.status_code == 429


async def test_client_address_prefers_the_forwarded_client(app):
    # Behind a reverse proxy, remote_addr is the PROXY for every request on earth —
    # keying on it would rate-limit the entire internet as one caller. The leftmost
    # X-Forwarded-For entry is the original client.
    async with app.test_request_context("/", headers={"X-Forwarded-For": "198.51.100.4, 10.0.0.1"}):
        assert ratelimit.client_address() == "198.51.100.4"


async def test_client_address_falls_back_to_the_peer(app):
    async with app.test_request_context("/"):
        # No proxy header: whatever the peer address is, it must be a usable key
        # rather than an empty string sharing one bucket with everyone.
        assert ratelimit.client_address()