mirror of
https://github.com/djdevin/recflare.git
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Devin Zuczek
83 lines
3.3 KiB
Markdown
83 lines
3.3 KiB
Markdown
# img
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Image-delivery worker served on the `img` subdomain.
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Images are stored as objects in the **`recflare-img` R2 bucket** and streamed back by
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key:
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- `GET /` — service status `{ "service": "img", "status": "ok" }`.
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- `GET /<key>` — streams the matching R2 object (e.g.
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`GET /DefaultProfileImage.jpg`). The key may contain slashes for nested
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objects. Content-Type comes from the object's stored HTTP metadata. Supports
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conditional requests via `If-None-Match` (returns `304`). Missing keys fall
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back to the bundled `static/DefaultProfileImage.jpg` asset (served `200` via
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the `ASSETS` binding), so clients always get a valid image. The fallback also
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honours `?sig=p1` and returns a `Content-Signature` header.
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- `GET /<key>?sig=p1` — same, plus a
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`Content-Signature: key-id=KEY:RSA:p1.rec.net; data=<base64>` header. By default
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that value is a **placeholder, not a real signature** — see below.
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The bucket is bound in the Worker as `env.IMAGES` (see `wrangler.jsonc`).
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## Response signing
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The client requires a `Content-Signature` header to be present when it asks for
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`?sig=p1`, but it never verifies the value. Signing for real is this worker's
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dominant CPU cost: it has to buffer the whole object into the isolate rather than
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streaming it out of R2, then hash the full body with SHA-1 and run an RSA-2048
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private-key operation — on every request the edge cache misses.
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So by default (`IMG_SIGNING_ENABLED: false` in `wrangler.jsonc`) the header is
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filled with a placeholder derived from the object key: FNV-1a seeds an xorshift32
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PRNG that emits 256 bytes, the length of a real RSA-2048 signature, so the value
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is structurally indistinguishable to the client's parser and stable for a given
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key. It costs no body access, so untransformed images keep streaming.
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Set the var to `true` for genuine RSA-SHA1 signatures over the returned bytes.
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Note this is a **placeholder, not a downgrade of a security control** — nothing
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in the system authenticates images either way. Turn it on before relying on the
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header for integrity. (Resizes buffer regardless — the Photon codec needs the
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whole image.)
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### Signing key
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`?sig=p1` signs with the RSA-2048 key in `env.IMG_SIGNING_KEY` (PKCS8 DER,
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base64). `wrangler.jsonc` ships an **insecure dev key** for local dev / tests;
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in production override it with a real secret:
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```sh
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wrangler secret put IMG_SIGNING_KEY # paste base64 PKCS8 DER of the private key
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```
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The matching public key must be published wherever the client looks up
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`KEY:RSA:p1.rec.net` so it can verify responses. Generate a keypair with:
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```sh
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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'))"
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```
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## One-time bucket setup
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```sh
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wrangler r2 bucket create recflare-img
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```
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## Seeding / uploading images
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A starter image lives in `static/` so it can be uploaded to R2:
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```sh
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wrangler r2 object put recflare-img/DefaultProfileImage.jpg \
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--file=apps/img/static/DefaultProfileImage.jpg \
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--content-type=image/jpeg --remote
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```
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(Drop `--remote` to write to the local dev bucket used by `pnpm dev`.)
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## Development
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```sh
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pnpm dev # run locally
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pnpm test # run tests
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```
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