GET / — service status { "service": "img", "status": "ok" }.
GET /<key> — streams the matching R2 object (e.g. GET /DefaultProfileImage.jpg). The key may contain slashes for nested objects. Content-Type comes from the object's stored HTTP metadata. Supports conditional requests via If-None-Match (returns 304). Missing keys fall back to the bundled static/DefaultProfileImage.jpg asset (served 200 via the ASSETS binding), so clients always get a valid image. The fallback also honours ?sig=p1 and returns a Content-Signature header.
GET /<key>?sig=p1 — same, plus a Content-Signature: key-id=KEY:RSA:p1.rec.net; data=<base64> header. By default that value is a placeholder, not a real signature — see below.

The bucket is bound in the Worker as env.IMAGES (see wrangler.jsonc).

Response signing

The client requires a Content-Signature header to be present when it asks for ?sig=p1, but it never verifies the value. Signing for real is this worker's dominant CPU cost: it has to buffer the whole object into the isolate rather than streaming it out of R2, then hash the full body with SHA-1 and run an RSA-2048 private-key operation — on every request the edge cache misses.

So by default (IMG_SIGNING_ENABLED: false in wrangler.jsonc) the header is filled with a placeholder derived from the object key: FNV-1a seeds an xorshift32 PRNG that emits 256 bytes, the length of a real RSA-2048 signature, so the value is structurally indistinguishable to the client's parser and stable for a given key. It costs no body access, so untransformed images keep streaming.

Set the var to true for genuine RSA-SHA1 signatures over the returned bytes. Note this is a placeholder, not a downgrade of a security control — nothing in the system authenticates images either way. Turn it on before relying on the header for integrity. (Resizes buffer regardless — the Photon codec needs the whole image.)

Signing key

?sig=p1 signs with the RSA-2048 key in env.IMG_SIGNING_KEY (PKCS8 DER, base64). wrangler.jsonc ships an insecure dev key for local dev / tests; in production override it with a real secret:

wrangler secret put IMG_SIGNING_KEY   # paste base64 PKCS8 DER of the private key

The matching public key must be published wherever the client looks up KEY:RSA:p1.rec.net so it can verify responses. Generate a keypair with:

node -e "const{generateKeyPairSync}=require('crypto');const{publicKey,privateKey}=generateKeyPairSync('rsa',{modulusLength:2048});console.log('PRIVATE',privateKey.export({type:'pkcs8',format:'der'}).toString('base64'));console.log('PUBLIC',publicKey.export({type:'spki',format:'der'}).toString('base64'))"

One-time bucket setup

wrangler r2 bucket create recflare-img

Seeding / uploading images

A starter image lives in static/ so it can be uploaded to R2:

wrangler r2 object put recflare-img/DefaultProfileImage.jpg \
  --file=apps/img/static/DefaultProfileImage.jpg \
  --content-type=image/jpeg --remote

(Drop --remote to write to the local dev bucket used by pnpm dev.)

Development

pnpm dev    # run locally
pnpm test   # run tests