Subdomain app routing derived the app identity from
httpapi.RequestHost, which returned the client-supplied
X-Forwarded-Host header verbatim. No middleware validated or stripped
that header, so a request from an untrusted peer could forge it. Since
the application_connect cookie is scoped to the wildcard apps domain,
JavaScript in a share=authenticated app could fetch() with a forged
X-Forwarded-Host pointing at a victim's owner-only app; coderd routed
and authorized the request as the victim and returned the private app
response same-origin to the attacker.
Replace RequestHost with httpmw.EffectiveHost, which honors
X-Forwarded-Host only when the original socket peer is a configured
trusted origin, otherwise falling back to the received Host header.
This ties host trust to the same RealIPConfig model already used for
X-Forwarded-For and -Proto. Wire it into HandleSubdomain for both
coderd and wsproxy, and log both the effective host and the raw
received_host.
Add coverage: EffectiveHost unit tests assert the trust decision uses
the socket peer rather than the spoofable forwarded client IP, and a
HandleSubdomain test confirms a forged X-Forwarded-Host from an
untrusted peer never reaches token resolution.
Refs: https://linear.app/codercom/issue/PLAT-259
Workspace-agent logs emitted while serving chatd-driven requests were
not correlated with the originating chat, making agent logs hard to
attribute to the corresponding/originating chat.
This adds agent-side chat context middleware that parses `Coder-Chat-Id`
once, enriches agent access logs and structured handler/background logs,
and adds a chatd bridge log when chat headers are attached to an agent
connection.
Closes CODAGT-324
George K