bimr-studio/proxy

Studio forge proxy

A stateless, host-allowlisted CORS proxy that lets a browser-based Studio read from a Forgejo instance on another origin. It forwards both the REST API and git smart HTTP; the target's absolute URL is carried in the path, so one scheme serves everything. It also fronts bimr.net so the agent can read the BIMR help page (a plain GET, no credentials):

/forge-proxy/https://forge.example/api/v1/repos/search?q=x
/forge-proxy/https://forge.example/owner/repo.git/info/refs?service=git-upload-pack

It has no dependencies and no state. It exists because browsers enforce the same-origin policy, and Forgejo never sends CORS headers on git routes.

Run

# allow one or more forges (exact hosts or *.suffix wildcards)
FORGE_ALLOWED_HOSTS="artefacts.bimr.net,bimr.net,*.example.org" node proxy/node.mjs

Then point Studio at it: set Proxy URL in Settings to http://localhost:8787/forge-proxy/, or serve it same-origin at /forge-proxy/.

Env	Default	Meaning
FORGE_ALLOWED_HOSTS	(empty)	Comma-separated allowlist. Empty denies every target.
FORGE_ALLOW_ANY	0	1 allows any host — development only.
FORGE_PROXY_PREFIX	/forge-proxy	Mount prefix, stripped to resolve scheme-less targets.
PORT	8787	Listen port.
HOST	127.0.0.1	Listen address.

URL scheme

The absolute target URL is appended to the mount path. The proxy accepts two shapes:

• with scheme — /forge-proxy/https://host/path (used for the REST API);
• scheme-less — /forge-proxy/host/path, which is what isomorphic-git's corsProxy produces (it strips https://). The proxy strips the mount prefix (FORGE_PROXY_PREFIX) and assumes https.

Both are validated against the allowlist.

Deployment

Behind nginx (same-origin)

nginx merges repeated slashes by default, which would turn https:// in the path into https:/. Disable that for the proxy location:

location /forge-proxy/ {
    merge_slashes off;
    proxy_pass http://127.0.0.1:8787;
    proxy_set_header Host $host;
    proxy_set_header X-Forwarded-Proto $scheme;
    proxy_request_buffering off;
    proxy_buffering off;
    client_max_body_size 256m;
}

systemd

[Unit]
Description=Studio forge proxy
After=network-online.target

[Service]
Environment=FORGE_ALLOWED_HOSTS=artefacts.bimr.net,bimr.net
Environment=PORT=8787
ExecStart=/usr/bin/node /srv/studio/proxy/node.mjs
Restart=on-failure

[Install]
WantedBy=multi-user.target

Edge / serverless

proxy/proxy.mjs exports a Web fetch handler and a default { fetch } object, so it also runs on Cloudflare Workers, Deno Deploy and Vercel Edge without changes. Provide the allowlist via the runtime's env binding; the handler reads FORGE_ALLOWED_HOSTS from process.env or globalThis.

Development

The Vite dev server mounts the same handler at /forge-proxy/ (see vite.config.ts), so development and production share one implementation. In dev, FORGE_ALLOW_ANY is enabled automatically when no allowlist is set.

Security

• Deny by default. An open proxy is an SSRF and abuse vector; always set FORGE_ALLOWED_HOSTS in production.
• HTTPS only, except http://localhost for local development.
• Browser credentials (Cookie, Origin, Referer) are stripped before forwarding; Set-Cookie is stripped from responses.
• Authorization and request/response bodies are never logged.
• Bodies are streamed (no buffering); put rate limiting and a body-size cap in the reverse proxy in front (see the nginx block above).

Test

node --test proxy/proxy.test.mjs