fix: rate limit /token and /revoke, bucket IPv6 by /64 and warn about untrusted forwarded headers (SEC-08)

tests/security/test_rate_limits.py

@@ -0,0 +1,169 @@
+"""Rate limiting covers the OAuth endpoints, IPv6 subscribers and untrusted proxies (SEC-08)."""
+
+from __future__ import annotations
+
+import logging
+from typing import Any
+
+import pytest
+from starlette.types import Message, Receive, Scope, Send
+
+from aegis_gitea_mcp.rate_limit import RequestRateLimiter, client_bucket
+from aegis_gitea_mcp.transports import ForwardedHeadersMiddleware
+from tests.test_executor_helpers import make_settings
+from tests.test_oauth_helpers import browser, build_oauth_app, oauth_settings
+
+LIMIT = 3
+
+
+@pytest.fixture(autouse=True)
+def _env(mock_env: None) -> None:
+    """The audit logger and the rate limiter read the process-wide settings."""
+
+
+@pytest.mark.parametrize(
+    ("method", "path"),
+    [
+        ("POST", "/token"),
+        ("POST", "/revoke"),
+        ("POST", "/register"),
+        ("GET", "/authorize"),
+        ("GET", "/oauth/callback"),
+        ("POST", "/oauth/consent"),
+        ("POST", "/mcp"),
+    ],
+)
+def test_every_unauthenticated_endpoint_is_rate_limited(method: str, path: str) -> None:
+    client = browser(build_oauth_app(oauth_settings(rate_limit_per_minute=LIMIT)).app)
+
+    statuses = [client.request(method, path).status_code for _ in range(LIMIT + 1)]
+
+    assert statuses[LIMIT] == 429
+    assert 429 not in statuses[:LIMIT]
+
+
+def test_the_429_answer_has_retry_after_and_no_detail() -> None:
+    client = browser(build_oauth_app(oauth_settings(rate_limit_per_minute=1)).app)
+    client.post("/token")
+
+    response = client.post("/token")
+
+    assert response.status_code == 429
+    assert response.headers["retry-after"] == "60"
+    assert response.json() == {"error": {"kind": "rate_limited", "message": "Too many requests"}}
+
+
+def test_ipv6_addresses_of_one_slash_64_share_a_bucket() -> None:
+    limiter = RequestRateLimiter(make_settings(rate_limit_per_minute=2))
+
+    first = limiter.check("2001:db8:1:2::1", None)
+    second = limiter.check("2001:db8:1:2:ffff:ffff:ffff:ffff", None)
+    third = limiter.check("2001:db8:1:2::abcd", None)
+    other_network = limiter.check("2001:db8:1:3::1", None)
+
+    assert first.allowed and second.allowed
+    assert not third.allowed
+    assert other_network.allowed
+
+
+def test_ipv4_clients_and_mapped_addresses_keep_their_own_bucket() -> None:
+    assert client_bucket("192.0.2.10") == "192.0.2.10"
+    assert client_bucket("::ffff:192.0.2.10") == "192.0.2.10"
+    assert client_bucket("2001:db8:1:2::1") == "2001:db8:1:2::/64"
+    assert client_bucket("fe80::1%eth0") == "fe80::/64"
+    assert client_bucket("testclient") == "testclient"
+    limiter = RequestRateLimiter(make_settings(rate_limit_per_minute=1))
+    assert limiter.check("192.0.2.10", None).allowed
+    assert limiter.check("192.0.2.11", None).allowed
+    assert not limiter.check("192.0.2.10", None).allowed
+
+
+# Forwarded headers
+
+
+class Recorder:
+    """Downstream ASGI app that remembers the client address it saw."""
+
+    def __init__(self) -> None:
+        self.clients: list[Any] = []
+
+    async def __call__(self, scope: Scope, receive: Receive, send: Send) -> None:
+        self.clients.append(scope.get("client"))
+
+
+def http_scope(peer: str, forwarded: str | None) -> Scope:
+    headers = [(b"host", b"mcp.example.com")]
+    if forwarded is not None:
+        headers.append((b"x-forwarded-for", forwarded.encode()))
+    return {
+        "type": "http",
+        "method": "GET",
+        "path": "/",
+        "scheme": "http",
+        "headers": headers,
+        "client": (peer, 5000),
+    }
+
+
+async def noop_receive() -> Message:
+    return {"type": "http.disconnect"}
+
+
+async def noop_send(message: Message) -> None:
+    return None
+
+
+async def test_forwarded_for_from_an_untrusted_peer_is_ignored_and_warned_about_once(
+    caplog: pytest.LogCaptureFixture,
+) -> None:
+    app = Recorder()
+    middleware = ForwardedHeadersMiddleware(app, "127.0.0.1")
+
+    with caplog.at_level(logging.WARNING, logger="aegis_gitea_mcp.transports"):
+        for _ in range(3):
+            await middleware(http_scope("172.18.0.5", "203.0.113.9"), noop_receive, noop_send)
+
+    # Spoofed header: the peer address stays the client address.
+    assert app.clients == [("172.18.0.5", 5000)] * 3
+    warnings = [r for r in caplog.records if "FORWARDED_ALLOW_IPS" in r.getMessage()]
+    assert len(warnings) == 1
+    assert "203.0.113.9" not in warnings[0].getMessage()
+    assert "172.18.0.5" not in warnings[0].getMessage()
+
+
+async def test_forwarded_for_from_a_trusted_peer_is_applied_without_a_warning(
+    caplog: pytest.LogCaptureFixture,
+) -> None:
+    app = Recorder()
+    middleware = ForwardedHeadersMiddleware(app, "172.18.0.0/16, 127.0.0.1")
+
+    with caplog.at_level(logging.WARNING, logger="aegis_gitea_mcp.transports"):
+        await middleware(http_scope("172.18.0.5", "203.0.113.9"), noop_receive, noop_send)
+        await middleware(http_scope("127.0.0.1", "203.0.113.10"), noop_receive, noop_send)
+
+    assert [client[0] for client in app.clients] == ["203.0.113.9", "203.0.113.10"]
+    assert caplog.records == []
+
+
+async def test_requests_without_forwarded_for_never_warn(caplog: pytest.LogCaptureFixture) -> None:
+    app = Recorder()
+    middleware = ForwardedHeadersMiddleware(app, "127.0.0.1")
+
+    with caplog.at_level(logging.WARNING, logger="aegis_gitea_mcp.transports"):
+        await middleware(http_scope("198.51.100.7", None), noop_receive, noop_send)
+
+    assert caplog.records == []
+    assert app.clients == [("198.51.100.7", 5000)]
+
+
+async def test_wildcard_trusts_every_peer_without_a_warning(
+    caplog: pytest.LogCaptureFixture,
+) -> None:
+    app = Recorder()
+    middleware = ForwardedHeadersMiddleware(app, "*")
+
+    with caplog.at_level(logging.WARNING, logger="aegis_gitea_mcp.transports"):
+        await middleware(http_scope("198.51.100.7", "203.0.113.9"), noop_receive, noop_send)
+
+    assert app.clients[0][0] == "203.0.113.9"
+    assert caplog.records == []