Harden daemon TCP transport: require loopback Host + reject cross-origin (CSRF/DNS-rebinding)#145
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BunsDev merged 2 commits intoMay 30, 2026
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…P transport (CSRF/DNS-rebinding) Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
is_loopback_host accepted any authority starting with "127.", so a hostname like 127.evil.com passed the Host/Origin guard and defeated its DNS-rebinding defense. Parse the host as an IpAddr and ask is_loopback(); keep the localhost literal.
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Summary
coven daemon serve --tcp <addr>serves the full unauthenticated/api/v1over loopback HTTP.bind_tcp_listeneralready refuses non-loopback binds, but the request handler did not checkHostorOrigin— so a web page the user visits could drive the daemon via a cross-origin "simple" request (CSRF), and DNS-rebinding (a foreignHostrebound to 127.0.0.1) could reach it. This adds a loopback guard to the TCP transport only; the Unix socket path is filesystem-gated and unchanged.Why
docs/AUTH.mdstates the API must not be exposed "on localhost TCP ... or a browser page" without "an explicit additional auth and pairing design," and notes there is "no CSRF/origin policy." The--tcpfeature (documented for "cockpit via Vite proxy") ships exactly that browser-reachable surface. This guard is the minimal origin/pairing design for it.Changes (
crates/coven-cli/src/daemon.rs)read_http_headersnow also capturesHostandOrigin.handle_http_streamgains anenforce_loopback_guardflag. On the TCP path it:Hostis not a loopback authority (127.x/localhost/::1) →403(defeats DNS-rebinding);Origin→403(defeats browser CSRF; a CLI/Vite-proxy client sends no cross-originOrigin).false(unaffected). Addswrite_forbidden(403) plus smallhost_is_loopback/origin_is_loopback/strip_port/is_loopback_hosthelpers.No new dependencies, no
unsafe, Unix-gated.Verification
cargo fmt,cargo clippy --workspace --all-targets -- -D warnings(clean), andcargo test --workspace --lockedall green on Linux: 697 pass, 0 fail. Four new tests cover the cross-origin block, the foreign-Host block, the loopback-origin allow, and the Unix path ignoringOrigin.Tracked by #143.
Note: PRs are frozen until July per CONTRIBUTING — opening this for visibility since it is a small, isolated security fix for the documented TCP/browser gap. Completely fine to close or hold until the window reopens; the branch will keep.