Skip to content

apiproxy.md

Latest commit

 

History

History
64 lines (52 loc) · 3.33 KB

apiproxy.md

File metadata and controls

64 lines (52 loc) · 3.33 KB
Raw

apiproxy binary

cmd/apiproxy is a small Anthropic-compatible HTTP proxy used to observe agent model traffic. It forwards requests to an upstream API and emits JSON event logs for requests/responses and SSE chunks.

Two independent credentials are involved:

  • Client auth token (PROXY_AUTH_TOKEN) — required; what callers must present to the proxy. Every request must carry either Authorization: Bearer <PROXY_AUTH_TOKEN> or X-Api-Key: <PROXY_AUTH_TOKEN>, otherwise the proxy returns 401 Unauthorized without logging or forwarding the request. The comparison is constant time. The gate token is stripped from the request and never forwarded upstream.
  • Upstream API key (ANTHROPIC_API_KEY) — what the proxy sends upstream. Once a caller passes the gate, the proxy injects this key as Authorization: Bearer <ANTHROPIC_API_KEY> unless the caller supplied its own real upstream credential (a non-dummy Authorization/X-Api-Key), which is forwarded as-is. This preserves the dummy-key workflow used by agent CLIs.

The two are deliberately separate so that the host upstream key is never an implicit credential for anyone who can reach the listener. The proxy fails closed: if PROXY_AUTH_TOKEN is unset, cmd/apiproxy exits with an error at startup, and the proxy handler refuses every request with 503 Service Unavailable rather than acting as an open relay. Otherwise any co-resident loopback process — including a prompt-injected agent — could spend the host ANTHROPIC_API_KEY unauthenticated.

Run

go build -o bin/apiproxy ./cmd/apiproxy
PROXY_AUTH_TOKEN=... ANTHROPIC_API_KEY=... \
  bin/apiproxy --port 9000 --upstream https://api.anthropic.com --log apiproxy.jsonl
# To expose beyond the local host, opt in explicitly:
PROXY_AUTH_TOKEN=... ANTHROPIC_API_KEY=... \
  bin/apiproxy --host 0.0.0.0 --port 9000 --upstream https://api.anthropic.com

Flags verified from cmd/apiproxy/main.go:

Flag Default Purpose
--host 127.0.0.1 Listen address. The default is localhost-only; use --host 0.0.0.0 only when another container/pod must reach the proxy and network policy/firewall rules protect it.
--port 9000 Listen port.
--upstream https://api.anthropic.com Upstream API base URL.
--log stdout Optional JSONL log file.

Environment:

Name Purpose
PROXY_AUTH_TOKEN Required. Client auth token callers must present to the proxy (Authorization: Bearer <token> or X-Api-Key: <token>). Validated with a constant-time compare and stripped before the upstream request. When unset, cmd/apiproxy refuses to start and the proxy handler answers 503.
ANTHROPIC_API_KEY Upstream API key injected on the outbound request when the caller did not supply its own real upstream credential. Never used to authenticate callers.

Deployment notes

The binary listens on 127.0.0.1:<port> by default. Treat --host 0.0.0.0 as an explicit compatibility opt-in for deployments that need cross-container or cross-pod access, and pair it with network policy/firewall controls. PROXY_AUTH_TOKEN is mandatory: without it the proxy would accept any caller and lend them the host ANTHROPIC_API_KEY, so the binary refuses to start. Use a high-entropy random value distinct from the upstream key, and rotate the two independently.