The web-tab proxy, its Test probe and its WebSocket relay accepted any http(s)
host. A live PoC relayed an IMDSv2-shaped PUT with custom headers to a loopback
echo server through a capability and no cookie, and 169.254.169.254 (decimal,
hex, IPv6-mapped, or via a DNS name) was as valid a dashboard as any other.
Loopback and RFC1918 stay allowed on purpose: a localhost Grafana is the feature.
Only link-local and the fixed cloud-metadata addresses are refused
(169.254.0.0/16, fe80::/10, fd00:ec2::254, 168.63.129.16, 100.100.100.200,
metadata.google.internal), at three stages that are each load-bearing:
- the Zod schema, so a save gets a clear refusal;
- a synchronous hostname check at every connect site, because net.connect skips
DNS for an IP literal and a lookup hook never sees one;
- a `lookup` hook on an undici Agent (webviewFetch) and on the ws client, which
judges the RESOLVED addresses of a name and refuses when any is blocked. This
is what closes DNS rebinding, which a hostname-string check cannot.
Adds undici@^6 so the proxy runs the package's own fetch with the package's own
Agent; a package Agent handed to Node's bundled fetch can mismatch protocols.
Verified live on an isolated beta: 169.254.169.254.nip.io (a real name resolving
to the metadata address) is refused by probe, proxy (403) and WS relay (4003),
while 127.0.0.1.nip.io still passes.
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WKtW48T1UjAaecHAJxKobE
