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hub: answer the local network only, whichever way a client arrives

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The reported bug was the Hub being reachable from outside the local
network when Server + Desktop is active. c33457f guards the Caddy site
for sovransystemsos.local, but the Hub is an application that also
listens on a port of its own (8937), and a check in Caddy does nothing
for a client that never goes through Caddy. Whether a client could reach
the Hub depended on which door it used.

The Hub now asks the question itself. LanOnlyMiddleware is registered
outermost, so a client that is not on this computer or the local network
gets a bare 403 before authentication is considered; it never sees the
login page.

- Local means loopback, 10/8, 172.16/12, 192.168/16, 100.64/10
  (Tailscale and other CGNAT/VPN ranges) and 169.254/16 over IPv4, and
  ::1, fc00::/7 and fe80::/10 over IPv6.
- IPv6 global addresses are not on the list. A global address belonging
  to a laptop on the LAN cannot be told apart from a stranger's by the
  address alone, and 2000::/3 is every public IPv6 address there is.
- ::ffff:a.b.c.d is read as the IPv4 address inside it.
- sovran_systemsOS.hub.extraLanNetworks adds networks (IPv4 or IPv6 CIDR)
  for setups whose own devices use addresses outside those ranges. It is
  checked at build time. The app ignores an entry it cannot parse and
  refuses 0.0.0.0/0 and ::/0: it must never widen its policy by
  guessing, and "everyone" is hub.lanOnly = false, asked for by name.
- sovran_systemsOS.hub.lanOnly (default true) turns the check off.
- The first refusal from each address is logged, naming the option to
  change, so an operator whose own device is refused can find out why.
  The list is capped so a scanner cannot fill the journal or memory.

Behind Caddy the policy applies to the real client, not to Caddy: uvicorn
takes the address from X-Forwarded-For only when the peer is 127.0.0.1.

Checked, not only reviewed:
- The real app with the config.json the module really generates (nix
  eval on the nixpkgs revision flake.lock pins, read back from the
  derivation), on a real socket with the source address chosen per
  request: 127.0.0.1, 192.168/16, 100.64/10 and a declared extra
  network are served; 203.0.113.9, 8.8.4.4 and an address just outside
  the declared /28 get 403 on /login, / and /api/ping. /auto-login still
  answers 303 to loopback and 403 to everyone else.
- With c33457f's Caddy guard in front, an IPv6 client at 2001:db8::9
  passes Caddy (it is inside 2000::/3) and is refused by the Hub; an
  IPv4 stranger has the connection closed by Caddy; a LAN client is
  served.
- hub.extraLanNetworks accepts 203.0.113.0/28, 2001:db8:abcd::/48 and
  bare hosts, and fails the build for /33, 300.1.1.1/8, 0.0.0.0/0, ::/0,
  2001:db8::/129 and junk, with a message that says what to write.

Add tests/test_lan_policy.py and tests/test_hub_lan_only.py, and a note
in SECURITY.md.
This commit is contained in:
Security Fix
2026-10-02 02:24:29 -05:00
committed by naturallaw777
parent 7d784eb653
commit 361b25a8bd
7 changed files with 492 additions and 0 deletions
Download Patch File Download Diff File Expand all files Collapse all files
tests/test_lan_policy.py
+230
View File
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"""Tests for the Hub's local-network policy and the middleware that enforces it.
The Hub runs as root, so it answers this computer and the local network and
nobody else: LanPolicy in security_helpers decides, LanOnlyMiddleware in
server.py enforces it before authentication is considered.
LanPolicy is exercised directly. The middleware is exercised over real HTTP
where the environment allows it; server.py cannot be imported from this repo
(it needs sovran_nwc from the Sovran_Bitcoin flake), so those tests skip rather
than fail, and the wiring is additionally asserted from source so it is always
checked.
"""
import logging
import os
import sys
import unittest
_REPO_ROOT = os.path.normpath(os.path.join(os.path.dirname(__file__), ".."))
_APP_PARENT = os.path.join(_REPO_ROOT, "app")
if _APP_PARENT not in sys.path:
sys.path.insert(0, _APP_PARENT)
from sovran_systemsos_web.security_helpers import ( # noqa: E402
LanPolicy,
LAN_ONLY_IPV4,
LAN_ONLY_IPV6,
)
_LOCAL = (
"127.0.0.1", "10.0.0.1", "172.16.0.1", "172.31.255.254", "192.168.1.10",
"100.64.0.1", "169.254.1.1",
"::1", "fd12:3456::1", "fc00::1", "fe80::1",
)
_REMOTE = (
"8.8.8.8", "1.1.1.1", "203.0.113.9", "9.255.255.255",
"172.15.255.255", "172.32.0.1", "192.169.0.1", "100.63.255.255",
# public IPv6 — every address in 2000::/3 is on the internet
"2001:4860:4860::8888", "2606:4700:4700::1111",
"2a00:1450:4001::1", "2400:cb00::1",
)
class LanPolicyMatrix(unittest.TestCase):
def test_local_addresses_are_allowed(self):
policy = LanPolicy()
for address in _LOCAL:
with self.subTest(local=address):
self.assertTrue(policy.allows(address))
def test_remote_addresses_are_refused(self):
policy = LanPolicy()
for address in _REMOTE:
with self.subTest(remote=address):
self.assertFalse(policy.allows(address))
def test_ipv6_global_is_not_whitelisted(self):
# 2000::/3 is the whole IPv6 global unicast space: allowing it would
# let every public IPv6 address through.
joined = " ".join(LAN_ONLY_IPV4 + LAN_ONLY_IPV6)
self.assertNotIn("2000::/3", joined)
for net in LanPolicy().networks:
if net.version == 6:
with self.subTest(range=str(net)):
self.assertTrue(str(net).startswith(("::1", "fc00", "fe80")),
f"{net} is not a local-only IPv6 range")
class LanPolicyConfiguration(unittest.TestCase):
def test_declared_networks_are_allowed(self):
policy = LanPolicy(extra_networks=["203.0.113.0/28", "2001:db8:abcd::/48"])
self.assertTrue(policy.allows("203.0.113.9"))
self.assertFalse(policy.allows("203.0.113.16"))
self.assertTrue(policy.allows("2001:db8:abcd::5"))
self.assertFalse(policy.allows("2001:db8:abce::5"))
def test_a_bare_address_is_a_single_host(self):
policy = LanPolicy(extra_networks=["203.0.113.9"])
self.assertTrue(policy.allows("203.0.113.9"))
self.assertFalse(policy.allows("203.0.113.10"))
def test_disabled_allows_everything(self):
policy = LanPolicy(enabled=False)
for address in _REMOTE:
with self.subTest(remote=address):
self.assertTrue(policy.allows(address))
def test_malformed_network_does_not_widen_the_policy(self):
# A typo must fail closed, not open the Hub to everything.
policy = LanPolicy(extra_networks=["not-a-network", "203.0.113.0/28"])
self.assertTrue(policy.allows("203.0.113.9"))
self.assertFalse(policy.allows("8.8.8.8"))
def test_a_zero_length_prefix_is_not_a_network(self):
# 0.0.0.0/0 and ::/0 mean "everyone". That is lan_only = false and it
# has to be asked for by name rather than arrive as a "network".
policy = LanPolicy(extra_networks=["0.0.0.0/0", "::/0"])
for address in _REMOTE:
with self.subTest(remote=address):
self.assertFalse(policy.allows(address))
def test_missing_or_unparseable_client_is_refused(self):
policy = LanPolicy()
for address in (None, "", "testclient", "not-an-ip"):
with self.subTest(client=address):
self.assertFalse(policy.allows(address))
def test_a_dual_stack_socket_does_not_hide_the_ipv4_client(self):
# With an IPv6 listener, IPv4 clients arrive as ::ffff:a.b.c.d. The
# address that counts is the IPv4 one inside it, both ways round.
policy = LanPolicy()
for address in ("::ffff:192.168.1.5", "::ffff:127.0.0.1", "::ffff:10.1.2.3"):
with self.subTest(local=address):
self.assertTrue(policy.allows(address))
for address in ("::ffff:8.8.8.8", "::ffff:203.0.113.9"):
with self.subTest(remote=address):
self.assertFalse(policy.allows(address))
# ── Middleware ───────────────────────────────────────────────────────────────
try:
from fastapi import FastAPI # noqa: E402
from fastapi.testclient import TestClient # noqa: E402
from sovran_systemsos_web.server import LanOnlyMiddleware # noqa: E402
HAVE_MIDDLEWARE = True
except Exception: # fastapi / sovran_nwc unavailable from this repo
HAVE_MIDDLEWARE = False
def _app_with(policy):
app = FastAPI()
@app.get("/ping")
async def ping():
return {"ok": True}
app.add_middleware(LanOnlyMiddleware, policy=policy)
return app
@unittest.skipUnless(HAVE_MIDDLEWARE, "server.py is not importable here")
class LanOnlyMiddlewareOverHttp(unittest.TestCase):
def _status(self, policy, client_ip):
client = TestClient(_app_with(policy), client=(client_ip, 51234))
return client.get("/ping").status_code
def test_local_client_is_served(self):
for address in ("127.0.0.1", "192.168.1.10", "10.0.0.1"):
with self.subTest(local=address):
self.assertEqual(self._status(LanPolicy(), address), 200)
def test_remote_client_is_refused(self):
for address in ("203.0.113.9", "8.8.8.8", "2001:4860:4860::8888"):
with self.subTest(remote=address):
self.assertEqual(self._status(LanPolicy(), address), 403)
def test_refusal_says_nothing_about_the_configuration(self):
# An outsider learns that the answer is no, not why or what to change.
client = TestClient(_app_with(LanPolicy()), client=("203.0.113.9", 51234))
response = client.get("/ping")
self.assertEqual(response.status_code, 403)
self.assertEqual(response.json(), {"detail": "Not available from this network"})
def test_disabled_policy_admits_remote_clients(self):
self.assertEqual(self._status(LanPolicy(enabled=False), "203.0.113.9"), 200)
def test_a_refused_address_is_logged_once(self):
# The operator whose own device is refused needs to find out why; a
# scanner must not be able to fill the journal.
client = TestClient(_app_with(LanPolicy()), client=("203.0.113.9", 51234))
with self.assertLogs("sovran_systemsos_web.server", level="WARNING") as seen:
for _ in range(5):
client.get("/ping")
self.assertEqual(len(seen.records), 1)
message = seen.records[0].getMessage()
self.assertIn("203.0.113.9", message)
self.assertIn("sovran_systemsOS.hub.extraLanNetworks", message)
def test_a_served_client_is_not_logged(self):
records = []
class _Collect(logging.Handler):
def emit(self, record):
records.append(record)
logger = logging.getLogger("sovran_systemsos_web.server")
handler = _Collect(level=logging.WARNING)
logger.addHandler(handler)
try:
client = TestClient(_app_with(LanPolicy()), client=("192.168.1.10", 51234))
client.get("/ping")
finally:
logger.removeHandler(handler)
self.assertEqual(records, [])
# ── Wiring, checked from source so it always runs ─────────────────────────────
def _server_source():
with open(os.path.join(_APP_PARENT, "sovran_systemsos_web", "server.py"),
encoding="utf-8") as f:
return f.read()
class LanOnlyWiring(unittest.TestCase):
def test_middleware_is_registered_outermost(self):
# Starlette makes the last-registered middleware the outermost one, so
# an off-network client is turned away before auth is considered.
src = _server_source()
auth = src.index("app.add_middleware(AuthMiddleware)")
nocache = src.index("app.add_middleware(NoCacheMiddleware)")
lan = src.index("app.add_middleware(LanOnlyMiddleware")
self.assertLess(auth, nocache)
self.assertLess(nocache, lan)
def test_policy_comes_from_the_generated_config(self):
src = _server_source()
self.assertIn("LanPolicy(", src)
self.assertIn('_hub_cfg.get("lan_only", True)', src)
self.assertIn('_hub_cfg.get("lan_extra_networks")', src)
if __name__ == "__main__":
unittest.main()