From 9da3cfc5d31bc4e1b9c4ea70f56e07b9aed8bb85 Mon Sep 17 00:00:00 2001 From: Christophe Besson Date: Sun, 13 Sep 2026 16:29:36 +0200 Subject: fix(node): the node's own controls take no authority from a hub token MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit `_is_node_admin()` is `self._user_id == node_user_id`, and `_user_id` is the `sub` of a JWT the hub issued. Six node-wide controls were gated on that alone: `node_status` — which lists every group on the machine with each root's **absolute path** — plus `node_settings_set`, `roster_read`, `denylist_read`, `denylist_clear` and `node_reload`. So the answer to "are you the operator of this node" was "the hub says so", which NS4 and M3 rule out in as many words: operator authority comes from the node's roster and from nowhere else, and asking the hub is how the hub installs itself as node administrator. The reach is bounded — a completed handshake also needs the group key — but an active hub obtains one legitimately in an open-join group, which §3.5 concedes, and from there it could read the operator's directory layout or clear the denylist, which is the persisted revocation H4 exists to keep. `_operator_device()` requires both halves now: the account is the one the node belongs to, *and* the device on this connection has proved a key the roster holds as an operator. `device_hello` is signed over a transcript naming the node, the group and this connection's nonce, and `operator_pks()` is rebuilt from the roster on each call, so an unpinned browser and a revoked one are both refused at once. The hub holds no user keys and cannot countersign a device. Keeping the account check as well is deliberate: dropping it would widen these node-wide controls to any paired operator of any group on the machine, which is a separate decision. `_is_node_admin()` stays as what it is in the handshake ack — a hint telling a client whether to offer the Node page — and says so. Nothing changes for a paired operator: `device_hello` runs unconditionally after the ack, and anyone using the Node page's controls is already paired, since `root_add` and every other signed op has always verified against `operator_pks()`. A browser that never paired now reads nothing there, which is the state in which it could already write nothing. test_node_status.py's fixture set the account and not the device, which is how it went on passing; it now wires the device the way `device_hello` leaves it. The adversary itself is in test_security_regressions.py — a token naming the owner's account with no proved device, which the previous source answered with `node_status_ack`. Co-Authored-By: Claude Opus 5 Claude-Session: https://claude.ai/code/session_01UMxEQadpzPkYLFf5CYKhpW --- packages/meshbay-node/tests/test_node_status.py | 7 ++ .../tests/test_security_regressions.py | 121 +++++++++++++++++++++ 2 files changed, 128 insertions(+) (limited to 'packages/meshbay-node/tests') diff --git a/packages/meshbay-node/tests/test_node_status.py b/packages/meshbay-node/tests/test_node_status.py index 091b1db..897be33 100644 --- a/packages/meshbay-node/tests/test_node_status.py +++ b/packages/meshbay-node/tests/test_node_status.py @@ -110,6 +110,13 @@ async def _session( session._group_id = GROUP session._user_id = "grenet" if operator else "mallory" session._username = session._user_id + # The device on the connection, as `device_hello` leaves it. Node-wide + # controls are gated on a key the node pinned as an operator and *proved* + # on this connection, not on the account id in the token — a hub can choose + # the second and cannot produce the first (NS4, M3). A fixture that sets + # only the account tests a check that is no longer the check. + session._pinned_pk = pk_op if operator else "" + session._device_confirmed = bool(operator) session._pk_user = "" session._uploads = {} session._admin_ops = {} diff --git a/packages/meshbay-node/tests/test_security_regressions.py b/packages/meshbay-node/tests/test_security_regressions.py index 988aa46..fa55ff6 100644 --- a/packages/meshbay-node/tests/test_security_regressions.py +++ b/packages/meshbay-node/tests/test_security_regressions.py @@ -837,3 +837,124 @@ def test_node_control_api_serves_no_html(): for gone in ("_render_page", "_render_audit_page", "_render_roster", "_AUDIT_HTML"): assert not hasattr(ui_app, gone), f"{gone} came back — HTML surface" + + +# ── NS4 / M3: the node's own controls take no authority from the hub ───────── + +async def _owner_session(tmp_path, roster, *, device: str = "", + confirmed: bool = False): + """A session whose token says it is the account this node belongs to. + + Which is all a hub can decide: `_user_id` is the `sub` of a JWT it issued, + so this is what an active hub forging a token arrives holding. Whether the + *device* on the connection is one the node pinned as an operator is the + other half, and no token can assert it. + """ + from meshbay_node.indexer.group_index import GroupIndex + + shared = tmp_path / "shared" + shared.mkdir(exist_ok=True) + index = GroupIndex(group_id="g" * 32, sk_node=Ed25519PrivateKey.generate()) + session = WebRTCPeerSession.__new__(WebRTCPeerSession) + session._ctx = { + "roots": one_root(shared), "index": index, "sk_node": index.sk_node, + "gek": generate_gek(), "roster": roster, + "node_user_id": "the-owner", + "daemon_state": {"groups_ctx": {}, "reload_fn": None}, + } + session._group_id = "g" * 32 + session._user_id = "the-owner" + session._username = "the-owner" + session._pinned_pk = device + session._device_confirmed = confirmed + session._pk_user = "" + session.sent = [] + session._send = session.sent.append + session._audit = lambda *a, **k: None + return session + + +@pytest.mark.asyncio +async def test_a_token_naming_the_owner_is_not_node_authority(tmp_path): + """ + The hub holds no user keys, so it cannot countersign a device — but it does + choose what a token says. Six node-wide controls used to be gated on the + account id alone, which is the hub's to decide: `node_status` (every group + on the machine, with the operator's absolute paths), `node_settings_set`, + `roster_read`, `denylist_read`, `denylist_clear` (the persisted revocation + H4 exists to keep) and `node_reload`. + + An active hub reaches a completed handshake wherever it can also obtain the + group key, which §3.5 concedes it can in an open-join group. From there, + "the hub says you are the owner" was the whole of the check. + """ + from meshbay_node.roster import Roster + + roster = Roster(db_path=tmp_path / "roster.db") + await roster.open() + try: + forged = await _owner_session(tmp_path, roster) + await forged._do_node_status({}) + assert forged.sent[-1]["type"] == "error" + assert forged.sent[-1]["code"] == "not_operator" + + forged.sent.clear() + await forged._do_denylist_read({}) + assert forged.sent[-1]["type"] == "error" + + forged.sent.clear() + await forged._do_denylist_clear({"subject": ""}) + assert forged.sent[-1]["type"] == "error", ( + "clearing the denylist undoes a revocation every node enforces") + finally: + await roster.close() + + +@pytest.mark.asyncio +async def test_an_identified_device_that_is_not_an_operator_is_refused(tmp_path): + """Being a pinned member of the group is not being the node's operator. + + The device proof is real here; what it proves is an ordinary member's key, + and `operator_pks()` is rebuilt from the roster on every call so a revoked + one stops working at once. + """ + from meshbay_node.roster import Roster + from meshbay_common.crypto import pk_to_b64 + + roster = Roster(db_path=tmp_path / "roster.db") + await roster.open() + try: + sk = Ed25519PrivateKey.generate() + member_pk = pk_to_b64(sk.public_key()) + await roster.pin_identity("the-owner", "the-owner", member_pk, + member_pk, "code") + session = await _owner_session(tmp_path, roster, device=member_pk, + confirmed=True) + await session._do_node_status({}) + assert session.sent[-1]["type"] == "error" + finally: + await roster.close() + + +@pytest.mark.asyncio +async def test_a_paired_operator_device_is_what_opens_it(tmp_path): + """The positive case, so the test above is about authority and not about + everything being refused.""" + from meshbay_node.roster import Roster + from meshbay_common.join import ROLE_OPERATOR + from meshbay_common.crypto import pk_to_b64 + + roster = Roster(db_path=tmp_path / "roster.db") + await roster.open() + try: + sk = Ed25519PrivateKey.generate() + pk = pk_to_b64(sk.public_key()) + await roster.pin_identity("the-owner", "the-owner", pk, pk, "code") + await roster.set_member("", "the-owner", ROLE_OPERATOR, "active", + "local-cli") + session = await _owner_session(tmp_path, roster, device=pk, + confirmed=True) + await session._do_denylist_read({}) + assert session.sent[-1]["type"] != "error", session.sent[-1] + finally: + await roster.close() -- cgit v1.2.3