Addresses planner audit #3 (SSRF via callbackUrl) and #7 (URL-param
size). Two attack surfaces hardened:
1. /new loader — \`callback\`, \`token\`, \`returnUrl\`, \`gpx\` query
params now validated:
- callbackUrl: must be a valid absolute http(s) URL ≤ 2048 chars.
If \`PLANNER_CALLBACK_ALLOWED_HOSTS\` is set (comma-separated),
the host must match — defense-in-depth SSRF guard for self-
hosted instances. Unset = no allowlist (dev / open self-host).
- token: max 2048 chars.
- returnUrl: must be a same-origin path or absolute http(s) URL
≤ 2048 chars. Rejects \`javascript:\`, \`data:\`, and
protocol-relative \`//host\` (which would resolve to a remote
origin on HTTPS pages).
- gpx: ≤ 2 MB encoded.
Invalid input throws 400 from the loader.
2. /session/:id default-export component — \`waypoints\`, \`noGoAreas\`,
\`notes\`, \`returnUrl\` URL params now bounded before
\`JSON.parse\` / use:
- waypoints / noGoAreas: ≤ 50KB each; over-cap returns undefined
(component starts with empty initial state, same as malformed).
- notes: ≤ 10KB.
- returnUrl: ≤ 2KB + same scheme rules as #1.
Pulled the URL validation into \`lib/url-validation.server.ts\` so
both routes (and any future caller) share the same rules.
Tests: \`url-validation.server.test.ts\` (14 cases — schemes,
allowlist, length caps, protocol-relative guards, env parsing).
Full repo: pnpm typecheck / lint / test all green.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
