The session callbackUrl becomes a server-side fetch target in
api.save-to-journal (POSTed with the callback bearer token, and the
journal's response is reflected to the caller). The /new query-param
loader already validated it, but the programmatic POST /api/sessions
entry point — anonymous, since the Planner is stateless — stored it
unvalidated. An attacker could make the Planner backend POST to
arbitrary hosts, including 169.254.169.254 and other internal targets.
- validateFetchUrl now blocks private / loopback / link-local /
CGNAT / cloud-metadata hosts (IPv4, IPv6, IPv4-mapped) when an
explicit allowlist isn't set. Gated on NODE_ENV=production && !E2E
(the requireSecret idiom) so the dev/e2e journal-on-localhost save
flow is unaffected. An explicit PLANNER_CALLBACK_ALLOWED_HOSTS still
takes precedence and remains the full-closure control (it also stops
DNS-name-to-private rebinding, which literal blocking does not).
- POST /api/sessions now validates callbackUrl exactly as /new does.
- api.save-to-journal re-validates immediately before the fetch
(defense in depth: covers sessions persisted before this change and
narrows the create→save rebinding window).
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
The Save-to-Journal flow had the browser fetch the journal with a
\`Bearer \${callbackToken}\` header. The JWT was visible in DevTools,
exfiltratable via any XSS or browser extension, and the planner's
\`loader\` shipped it down to the client as part of the page payload.
Now:
- **New action**: \`POST /api/save-to-journal\` (\`routes/api.save-to-journal.ts\`).
Body: \`{ sessionId, gpx }\`. The action loads \`callbackUrl\` +
\`callbackToken\` from \`planner.sessions\` (set at /new time when the
user came from the journal), POSTs to the journal server-to-server
with the Bearer, and forwards the response.
- **\`SaveToJournalButton\`**: drops the \`callbackUrl\` + \`callbackToken\`
props. Takes \`sessionId\` only and POSTs to the planner action.
- **\`session.\$id.tsx\` loader**: stops returning \`callbackUrl\` /
\`callbackToken\` to the client. Returns a single \`hasJournalCallback\`
boolean so the button still knows whether to render.
- **\`SessionView\`**: same prop simplification.
Trust model is unchanged: the same \`sessionId\` that grants Yjs
membership grants save authority. Knowing the URL = ability to act.
The action only adds a server-side hop so the JWT never reaches
browser JS.
Phase B (jti single-use enforcement on the journal side) follows in
a separate PR — needs a journal DB column + verifier change.
Full repo: pnpm typecheck / lint / test all green.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
