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Restrict the public CORS proxy to allowlisted calling sites - #118
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Add an optional ALLOWED_ORIGINS setting to the proxy core. When set, a request whose Origin is missing, null or unlisted gets the same 404 as a bad token, checked before the edge cache and any upstream fetch; allowed responses echo the caller's origin with Vary: Origin. Targets are never restricted. Refusals are recorded in the stats. The public instance allows savr.link, Netlify preview/branch deploys and localhost. Unset (every self-hosted proxy) behaves as before. Rate limiting is tracked separately in #117. See ADR 0006. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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jonocodes
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Oct 16, 2026
The public proxy now refuses unlisted calling sites (#118). The probe must still read as "running" there: an allowed caller gets the CORS 400, a refused one a 404 that still carries CORS headers. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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Summary
Stops other websites from spending the shared proxy's free-tier quota through their visitors' browsers.
ALLOWED_ORIGINSsetting in the proxy core: comma-separated origins,*within a host label (never crosses a.),:*for any port.null/ unlistedOrigin→ the same 404 as a bad token, checked before the edge cache and any upstream fetch. Refusals are recorded in the stats (404/bypass/ no host).Access-Control-Allow-OriginwithVary: Origin.OPTIONSand/healthstay open. Composes withPROXY_TOKENS.[env.public.vars]):https://savr.link,https://*--savrlist.netlify.app,http://localhost:*,http://127.0.0.1:*. Unset (every self-hosted proxy) = unchanged behaviour.Caveats
Origin. Rate limiting is tracked in CORS proxy: consider a Cloudflare rate-limiting rule on the public instance #117.Deploy
Takes effect after
npx wrangler deploy --env publicfrominfra/cors-worker.Test plan
node --test "infra/cors-worker/*.test.mjs" "infra/cors-stats/*.test.mjs"— 61 pass (9 new: allowed origins incl. previews/localhost, refusals incl. dot-crossing and wrong scheme/port, targets unrestricted, cache ordering, token composition, unset = open, stats recording, pattern parsing)curlwithoutOrigingets 404🤖 Generated with Claude Code