Zone Transfer in Chi

Zone Transfer in the context of Chi refers to the exposure of internal network or service topology through unchecked DNS or service discovery responses. Attackers can request a full zone transfer (AXFR) from an open DNS server or abuse service endpoints that return routing or inventory data, revealing internal IP ranges, hostnames, and trust relationships. In Chi-based applications, this often surfaces in custom service registries, internal HTTP handlers that emit network maps, and administrative routes that return backend peer information.

Chi-specific code paths where zone transfer–like behavior appears include HTTP handlers that return serialized node inventories, gRPC reflection endpoints that disclose service methods and network addresses, and diagnostic routes that emit peer lists. For example, a Chi route that exposes an internal /debug/peers endpoint may inadvertently return hostnames and IPs that should remain internal:

// Chi debug endpoint that may leak network topology
let debugPeersHandler = async (ctx) => {
  let peers = getInternalPeers(); // returns IPs/hostnames of cluster nodes
  ctx.response.body = { peers: peers };
};

Similarly, if DNS utilities are embedded to perform service discovery, a missing access control on a /dns/zone endpoint can allow an AXFR-style query to return the full zone file. Attack patterns include probing for unauthenticated /debug or /health aggregation routes that echo backend network details, or leveraging exposed gRPC reflection to enumerate services and infer network zones.

To detect zone transfer–style leaks in Chi services, focus on routes that return network, peer, or zone data without authentication. Look for endpoints under /debug, /internal, /network, or any route that serializes peer lists or DNS zone contents. Inspect Chi middleware pipelines for handlers that do not enforce authorization before emitting backend topology.

With middleBrick, you can scan the unauthenticated attack surface of a Chi-based API to surface these findings. middleBrick runs 12 security checks in parallel, including BFLA/Privilege Escalation, Property Authorization, and Unsafe Consumption checks, which can identify overly verbose error messages, missing authorization on administrative routes, and endpoints that expose internal network details. The scan analyzes OpenAPI/Swagger specs (2.0, 3.0, 3.1) with full $ref resolution, cross-referencing spec definitions with runtime behavior to highlight routes that may leak zone data.

In the dashboard or via the CLI (middlebrick scan <url>), findings will include severity, a description of the exposure, and remediation guidance. For LLM-specific concerns—such as prompt injection or system prompt leakage when admin endpoints are exposed—middleBrick’s unique LLM/AI Security checks can probe for system prompt extraction and output scanning for sensitive data patterns, which is especially useful if your Chi service exposes AI-assisted diagnostics.

Remediation focuses on removing or protecting routes that expose network topology and enforcing strict authorization. In Chi, use route guards and middleware to ensure only authenticated and authorized callers can access debug or administrative endpoints. Remove or hide any routes that return raw peer lists, zone files, or internal DNS data in production.

For the debug peers example, either remove the route entirely or protect it with a guard that checks caller permissions:

// Securing the peers endpoint with a guard in Chi
let checkAuth = (req, res, next) => {
  if (!req.headers.authorization || !isValidToken(req.headers.authorization)) {
    res.status = 403;
    res.end('Forbidden');
    return;
  }
  next();
};

let securePeersHandler = (req, res) => {
  let peers = getInternalPeers();
  res.json({ peers: peers });
};

app.derive(securePeersHandler)
     .get('/internal/peers', checkAuth, securePeersHandler);

Additionally, avoid embedding DNS or zone transfer logic in HTTP handlers. If service discovery is required, use a dedicated, secured service mesh or ensure that any DNS query endpoints enforce strict source validation and rate limiting. Sanitize outputs to prevent verbose error messages that may disclose hostnames or IPs, and ensure administrative routes are not reachable from untrusted networks.