From b86be704df752f2fd3086fcca43b7f4de78389d1 Mon Sep 17 00:00:00 2001 From: Christophe Besson Date: Thu, 13 Aug 2026 11:18:24 +0200 Subject: fix: resource limits, signaling authz, node admin UI token MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Phase 11.5 — findings H6, C4 (partial), and milestone 11.5.3. H6 — resource exhaustion. Several paths let one peer degrade or stall a node: * the DataChannel frame limit was a flat 64 MB applied BEFORE authentication, so an unauthenticated peer could announce a huge frame and dribble bytes into it. Unauthenticated peers now get 64 KB; the large budget is granted only after the GEK proof, where it is needed for uploads. * _do_stream_segment ran subprocess.run(..., timeout=30) directly in the event loop, stalling the entire daemon — every peer, every group — for up to thirty seconds per request. Now async, with a timeout and process kill. * ffmpeg was spawned per stream request with no cap. Both streaming paths now share a transport-wide semaphore. * POST /v1/nodes/{id}/webrtc/offer was reachable by any authenticated user for any node, with no membership check and no rate limit, making the target node allocate an aiortc PeerConnection and gather ICE on demand — remote resource exhaustion against a third party's machine. Now rate limited, capped per user, SDP size bounded, and the caller must share an active group with the node. That also closes the H4 gap where signaling ignored group status. * POST /v1/nodes/{id}/incoming took peer_ip verbatim, so any user could make an arbitrary node emit UDP packets to an address of their choosing. The probe target must now match the caller's own source address. C4 (partial) — the pre-proof bundle window. GEK and keypair bundle fetches are served before the GEK proof by necessity: the client needs its wrapped bundle in order to compute the proof. That window is a disclosure surface a hub can reach by forging a JWT. Bounded to 4 fetches per session and audited as "pre_proof_fetch". The real fix is removing remote keypair bundles entirely, which belongs to the native client (Phase 13.3). 11.5.3 — the node admin UI was unauthenticated because it binds loopback. But any local process can reach it, and so can a page in the operator's browser via DNS rebinding — and this API re-initialises group keys and reads the audit log. H2 showed script execution there equals full control. Now gated by a per-run token, printed at startup, accepted as ?t= or X-MeshBay-Token. One test needed rewriting rather than adding: the first version asserted "subprocess.run(" was absent from the source, which also matched the comment documenting the old behaviour. It now parses the AST and checks the property. Tests: 121 node, 142 hub+common. Regression suite 47 node + 10 hub. Co-Authored-By: Claude Opus 5 --- .../meshbay-hub/src/meshbay_hub/api/signaling.py | 56 ++++++++++++++++++++-- 1 file changed, 53 insertions(+), 3 deletions(-) (limited to 'packages/meshbay-hub/src/meshbay_hub/api/signaling.py') diff --git a/packages/meshbay-hub/src/meshbay_hub/api/signaling.py b/packages/meshbay-hub/src/meshbay_hub/api/signaling.py index bd343c9..8f84163 100644 --- a/packages/meshbay-hub/src/meshbay_hub/api/signaling.py +++ b/packages/meshbay-hub/src/meshbay_hub/api/signaling.py @@ -17,11 +17,15 @@ import json import logging import uuid -from fastapi import APIRouter, Depends, HTTPException +from fastapi import APIRouter, Depends, HTTPException, Request from pydantic import BaseModel +from sqlalchemy import select +from sqlalchemy.ext.asyncio import AsyncSession from meshbay_hub.api.deps import get_current_user -from meshbay_hub.db.models import User +from meshbay_hub.api.middleware import limiter +from meshbay_hub.db.engine import get_db +from meshbay_hub.db.models import Group, GroupMember, User log = logging.getLogger(__name__) @@ -41,25 +45,66 @@ class WebRTCOfferResponse(BaseModel): peer_id: str +MAX_SDP_BYTES = 16 * 1024 # an SDP offer is ~2 KB +MAX_PENDING_PER_USER = 3 # concurrent in-flight offers per account + +_pending_per_user: dict[str, int] = {} + + @router.post("/{node_id}/webrtc/offer", response_model=WebRTCOfferResponse) +@limiter.limit("30/minute") async def webrtc_offer( node_id: str, body: WebRTCOfferRequest, + request: Request, current_user: User = Depends(get_current_user), + db: AsyncSession = Depends(get_db), ): """ Browser sends WebRTC SDP offer for a node. Hub relays via WebSocket. Returns the node's SDP answer once received. + + Finding H6: this was reachable by any authenticated user, for any node, with no + rate limit and no membership check. Each call makes the node allocate an + aiortc RTCPeerConnection and gather ICE, so it was a remote resource-exhaustion + primitive against an arbitrary third party's machine. + + Finding H4: it also ignored group status, so "suspend a group" did not stop new + connections from being brokered to nodes hosting it. """ - from meshbay_hub.api.revocation import _connected_nodes + from meshbay_hub.api.revocation import _connected_nodes, _node_groups + + if len(body.sdp) > MAX_SDP_BYTES: + raise HTTPException(status_code=413, detail="SDP too large") ws = _connected_nodes.get(node_id) if not ws: raise HTTPException(status_code=404, detail="Node not connected") + # The caller must share at least one active group with the target node. + node_group_ids = set(_node_groups.get(node_id, [])) + if node_group_ids: + result = await db.execute( + select(GroupMember.group_id).where( + GroupMember.user_id == current_user.id, + GroupMember.group_id.in_(node_group_ids), + )) + shared = [gid for (gid,) in result.all()] + if not shared: + raise HTTPException(status_code=403, detail="Not a member of any group on this node") + + active = await db.execute( + select(Group.id).where(Group.id.in_(shared), Group.status == "active")) + if not active.first(): + raise HTTPException(status_code=403, detail="Group is not active") + + if _pending_per_user.get(current_user.id, 0) >= MAX_PENDING_PER_USER: + raise HTTPException(status_code=429, detail="Too many pending connections") + peer_id = str(uuid.uuid4()) answer_future: asyncio.Future = asyncio.get_event_loop().create_future() _webrtc_answers[peer_id] = answer_future + _pending_per_user[current_user.id] = _pending_per_user.get(current_user.id, 0) + 1 try: await ws.send_text(json.dumps({ @@ -83,6 +128,11 @@ async def webrtc_offer( ) finally: _webrtc_answers.pop(peer_id, None) + remaining = _pending_per_user.get(current_user.id, 1) - 1 + if remaining > 0: + _pending_per_user[current_user.id] = remaining + else: + _pending_per_user.pop(current_user.id, None) def handle_webrtc_answer(msg: dict) -> None: -- cgit v1.2.3