From bce962c39fcb2d124506e33f77c3ca9082f145dd Mon Sep 17 00:00:00 2001 From: Christophe Besson Date: Fri, 25 Sep 2026 14:53:42 +0200 Subject: fix(hub): present a node-audience token in the handshake, not the hub session token MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit A member authenticated to a node in the MNP handshake with its hub *session* token — scope=user, valid at the hub API for hours. A node operator is in the threat model, so this handed them a live hub credential for the member: enough to enumerate the member's other groups, act as them, and (before the previous commit closed it) take the account over. The node genuinely needs a hub-signed membership assertion, so the fix is to make that a separate credential that opens nothing at the hub API. Two audiences signed by the one hub key (meshbay_common/tokens.py): - HUB_API_AUD — session tokens (login, device-auth, node-auth, refresh), used for hub calls and signaling. decode_access_token now binds this audience, so an MNP token cannot be replayed against the hub API. - MNP_AUD — a short-lived token a member presents to a node and nothing else, from POST /v1/nodes/mnp-token. authorize_token now binds this audience, so a session token presented to a node is refused. This closes the disclosure. The node's own self-decode (hub_client.py) reads its node token with audience=HUB_API_AUD. The client fetches the MNP token inside transport.connect() (and on every reconnect) using the session token, so callers are unchanged and signaling keeps using the session token. No regression to a long session: the MNP token is checked once, at the handshake, before any proof — a film already playing is not re-authenticated, so a 15-minute token does not interrupt a 4-hour film; reconnects refetch a fresh one. Denylist and membership checks are unchanged (the MNP token carries sub/jti/groups). Tests: authorize_token refuses a session/no-audience token and accepts an MNP token; the hub API refuses an MNP token; POST /v1/nodes/mnp-token is minted only for a member's own session. Verified red-before/green-after; common, node and hub suites green (the pre-existing test_cli_golden failure is an argparse/pytest prog artifact unrelated to this change). Still to do before deploy (B2): bump the MNP version and client.minimum so a stale desktop client is told to update rather than getting a handshake refusal, update docs/MESHBAY_DESIGN.md and MESHBAY_NODE_PROTOCOL.md, and validate against a real node locally, then deploy hub+node+SPA atomically. Co-Authored-By: Claude Opus 4.8 --- packages/meshbay-node/src/meshbay_node/hub_client.py | 8 +++++++- packages/meshbay-node/tests/test_hub_client.py | 5 +++-- packages/meshbay-node/tests/test_multi_group.py | 3 ++- packages/meshbay-node/tests/test_quic_transport.py | 4 +++- packages/meshbay-node/tests/test_webrtc_transport.py | 4 +++- 5 files changed, 18 insertions(+), 6 deletions(-) (limited to 'packages/meshbay-node') diff --git a/packages/meshbay-node/src/meshbay_node/hub_client.py b/packages/meshbay-node/src/meshbay_node/hub_client.py index 49bb920..346a4cd 100644 --- a/packages/meshbay-node/src/meshbay_node/hub_client.py +++ b/packages/meshbay-node/src/meshbay_node/hub_client.py @@ -135,8 +135,14 @@ class HubClient: access_token = data["access_token"] from meshbay_common.handshake import JWT_LEEWAY_SECONDS + from meshbay_common.tokens import HUB_API_AUD + # This is the node's own hub-API session token (scope=node), so it + # carries aud=HUB_API_AUD and must be decoded with that audience — the + # node reads its own exp/scope/jti here. It is a different credential + # from the MNP token a member presents in the handshake (aud=MNP_AUD), + # which authorize_token binds separately. decoded = jwt.decode(access_token, hub_pk_pem, algorithms=["EdDSA"], - leeway=JWT_LEEWAY_SECONDS) + leeway=JWT_LEEWAY_SECONDS, audience=HUB_API_AUD) # No pk_user claim to check any more: tokens carry no key. What binds this # token to this node is the Ed25519 challenge it was issued against. assert "jti" in decoded, "Hub token missing jti — hub is outdated" diff --git a/packages/meshbay-node/tests/test_hub_client.py b/packages/meshbay-node/tests/test_hub_client.py index e733610..95c93c7 100644 --- a/packages/meshbay-node/tests/test_hub_client.py +++ b/packages/meshbay-node/tests/test_hub_client.py @@ -10,6 +10,7 @@ import pytest from cryptography.hazmat.primitives import serialization from cryptography.hazmat.primitives.asymmetric.ed25519 import Ed25519PrivateKey from cryptography.hazmat.primitives.asymmetric.x25519 import X25519PrivateKey +from meshbay_common.tokens import HUB_API_AUD from meshbay_node.hub_client import HubClient, HubConfig from meshbay_node.keystore import NodeKeys @@ -52,7 +53,7 @@ def make_node_token(sk_pem, user_id, pk_user_b64, hub_id="fake-hub", ttl=3600): return jwt.encode({ "iss": hub_id, "sub": user_id, "pk_user": pk_user_b64, "hub_id": hub_id, "jti": "test-jti", "scope": "node", - "iat": now, "exp": now + ttl, + "iat": now, "exp": now + ttl, "aud": HUB_API_AUD, }, sk_pem, algorithm="EdDSA") @@ -89,7 +90,7 @@ async def test_login_rejects_missing_jti(hub_keys, node_keys, hub_config): sk_hub, sk_hub_pem, pk_hub_pem = hub_keys bad_token = jwt.encode({ "iss": "fake-hub", "sub": "uid", "pk_user": node_keys.pk_ed25519_b64, - "hub_id": "fake-hub", "scope": "node", + "hub_id": "fake-hub", "scope": "node", "aud": HUB_API_AUD, "iat": int(time.time()), "exp": int(time.time()) + 3600, }, sk_hub_pem, algorithm="EdDSA") diff --git a/packages/meshbay-node/tests/test_multi_group.py b/packages/meshbay-node/tests/test_multi_group.py index b75bad0..01b2abc 100644 --- a/packages/meshbay-node/tests/test_multi_group.py +++ b/packages/meshbay-node/tests/test_multi_group.py @@ -7,6 +7,7 @@ Verifies that: - A user in both groups can access both """ +from meshbay_common.tokens import MNP_AUD import time import jwt @@ -63,7 +64,7 @@ def make_jwt(sk_hub, pk_node_b64, groups, user_id="user-001", ttl=3600): "iss": "test-hub", "sub": user_id, "pk_user": pk_node_b64, "hub_id": "test-hub", "jti": "test-jti", "iat": now, "exp": now + ttl, - "groups": groups, + "groups": groups, "scope": "user", "aud": MNP_AUD, }, sk_pem, algorithm="EdDSA") diff --git a/packages/meshbay-node/tests/test_quic_transport.py b/packages/meshbay-node/tests/test_quic_transport.py index 8eb0622..a32402a 100644 --- a/packages/meshbay-node/tests/test_quic_transport.py +++ b/packages/meshbay-node/tests/test_quic_transport.py @@ -3,6 +3,7 @@ Integration test: QuicChunkServer ↔ QuicChunkClient over QUIC/UDP loopback. Same structure as test_transport.py but uses QUIC instead of TCP+TLS. """ +from meshbay_common.tokens import MNP_AUD import asyncio import os import time @@ -51,7 +52,8 @@ def make_jwt(sk_hub, pk_node_b64, ttl=3600, groups=None): "pk_user": pk_node_b64, "hub_id": "test-hub", "jti": "test-jti", "iat": now, "exp": now + ttl, # group_id is mandatory (M1), so default tokens are members of "g". - "groups": groups if groups is not None else ["g"], + "groups": groups if groups is not None else ["g"], "scope": "user", + "aud": MNP_AUD, }, sk_pem, algorithm="EdDSA") diff --git a/packages/meshbay-node/tests/test_webrtc_transport.py b/packages/meshbay-node/tests/test_webrtc_transport.py index 0245c4e..990b1da 100644 --- a/packages/meshbay-node/tests/test_webrtc_transport.py +++ b/packages/meshbay-node/tests/test_webrtc_transport.py @@ -7,6 +7,7 @@ for MNP protocol exchange (handshake, index_sync, file_request, file_chunk). Uses local loopback (no STUN/ICE needed for localhost). """ +from meshbay_common.tokens import MNP_AUD import asyncio import base64 import hashlib @@ -115,6 +116,7 @@ def _make_jwt(sk_hub, groups=None, pk_user="test"): "pk_user": pk_user, "hub_id": "test-hub", "jti": "test-jti-webrtc", "iat": now, "exp": now + 3600, "groups": groups if groups is not None else [TEST_GROUP], + "scope": "user", "aud": MNP_AUD, }, sk_pem, algorithm="EdDSA") @@ -218,7 +220,7 @@ def _token(sk_hub, jwt_sub, peer_id, group_id, pk_user="test"): "iss": "test-hub", "sub": jwt_sub, "pk_user": pk_user, "hub_id": "test-hub", "jti": f"jti-{peer_id}", "iat": now, "exp": now + 3600, - "groups": [group_id], "scope": "user", + "groups": [group_id], "scope": "user", "aud": MNP_AUD, }, sk_h_pem, algorithm="EdDSA") -- cgit v1.2.3