From 2ccb6653e8841d4d6f3ab933f84746cce4e2fe2b Mon Sep 17 00:00:00 2001 From: Christophe Besson Date: Sat, 26 Sep 2026 02:03:50 +0200 Subject: feat(protocol): bind the MNP token to the node it is for (E10) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The audience split stopped a member's node credential from opening the hub API. It did not stop the credential being *replayed to another node*: the MNP token carried the member's whole group set and named no node, so a token handed to node A's operator could be presented to node B the member also belongs to. That does not read content on B — the handshake still requires proving node B's group key, which the operator lacks — but it reaches B's pre-proof window and fetches the member's *encrypted* keypair bundle for B (offline-attackable, bounded, audited): a disclosure §2.4 says should not follow from hosting a member on A. The token now names the node it is minted for (a `node` claim = that node's Ed25519 key), and authorize_token refuses one that names a different key. The client already knows the target node's key (from /v1/groups/{id}/nodes) and asks for a token bound to it: POST /v1/nodes/mnp-token takes node_pk, and transport.connect threads it (group-page, the connection pool and rewrap pass n.pk_node; reconnect preserves it). A token that names no node is still accepted, because the hub only mints one for the authenticated requester, so an unbound token grants nothing across accounts — which also keeps non-binding callers working with no churn. Done before deploy, so it folds into the MNP 4.0 flag day rather than needing its own. Docs: §5.2, register E10, MESHBAY_NODE_PROTOCOL.md §6.3. test_handshake.py and test_mnp_token.py hold the binding (a token for node A is refused by node B, accepted by node A; an unbound token still works); red before, green after. common/node/hub suites green. Co-Authored-By: Claude Opus 4.8 --- packages/meshbay-hub/tests/test_mnp_token.py | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+) (limited to 'packages/meshbay-hub/tests/test_mnp_token.py') diff --git a/packages/meshbay-hub/tests/test_mnp_token.py b/packages/meshbay-hub/tests/test_mnp_token.py index 7b483ff..3aa3115 100644 --- a/packages/meshbay-hub/tests/test_mnp_token.py +++ b/packages/meshbay-hub/tests/test_mnp_token.py @@ -69,3 +69,24 @@ async def test_a_session_token_is_refused_by_a_node_but_the_mnp_token_is_not(cli # The MNP token authorises the member to the node. peer = authorize_token(mnp, pk, group_id=gid) assert peer.group_id == gid + + +@pytest.mark.asyncio +async def test_the_mnp_token_is_bound_to_the_node_it_names(client): + """E10: a token minted for node A is refused by node B, so an operator who + captures a member's token cannot replay it to another of the member's nodes.""" + from meshbay_hub.auth import hub_public_key_pem + + tok = await _session_token(client, "mnp_bind_test") + H = {"Authorization": f"Bearer {tok}"} + gid = (await client.post("/v1/groups", headers=H, json={ + "name": "g", "visibility": "private", "join_policy": "invite"})).json()["group_id"] + # A token bound to node A's key. + mnp = (await client.post("/v1/nodes/mnp-token", headers=H, + json={"node_pk": "node-A-pk"})).json()["mnp_token"] + pk = hub_public_key_pem() + # Node B refuses it; node A accepts it. + with pytest.raises(HandshakeError, match="this node"): + authorize_token(mnp, pk, group_id=gid, node_pk_b64="node-B-pk") + peer = authorize_token(mnp, pk, group_id=gid, node_pk_b64="node-A-pk") + assert peer.group_id == gid -- cgit v1.2.3