secret-proxy

Secret Proxy

MITM proxy that injects API secrets into HTTP headers. Runs outside sandbox microVMs.

For architecture overview and security analysis, see docs/secret-proxy.md.

Building

go build -o secret-proxy ./cmd/secret-proxy
go build -o genca ./cmd/genca

Configuration

Variable	Default	Description
LISTEN_ADDR	:8080	Address to listen on
CONTROL_PLANE_URL	required	URL of control-plane for token validation
CA_CERT_PATH	/etc/secret-proxy/ca.crt	Path to CA certificate for MITM
CA_KEY_PATH	/etc/secret-proxy/ca.key	Path to CA private key
SECRETS_PATH	/etc/secret-proxy/secrets.json	Path to secrets JSON file

Secrets JSON Format

{
  "anthropic": "sk-ant-api03-xxxxx...",
  "openai": "sk-xxxxx...",
  "mistral": "xxxxx...",
  "github_copilot": "gho_xxxxx..."
}

Keys match the secret_key returned by control-plane validation.

Running Locally

# Generate CA certificate
go run ./cmd/genca -out /tmp/secret-proxy

# Run proxy
CONTROL_PLANE_URL=http://localhost:3000 \
CA_CERT_PATH=/tmp/secret-proxy/ca.crt \
CA_KEY_PATH=/tmp/secret-proxy/ca.key \
SECRETS_PATH=./secrets.json \
go run ./cmd/secret-proxy

Testing

go test ./...

Docker

docker build -t secret-proxy .
docker run \
  -e CONTROL_PLANE_URL=http://control-plane:3000 \
  -v /path/to/ca.crt:/etc/secret-proxy/ca.crt \
  -v /path/to/ca.key:/etc/secret-proxy/ca.key \
  -v /path/to/secrets.json:/etc/secret-proxy/secrets.json \
  secret-proxy

How It Works

1. Receives CONNECT request with Proxy-Authorization: Bearer <token> header
2. Validates token with control-plane (POST /internal/validate-proxy-auth)
3. If allowed, establishes HTTPS tunnel with MITM
4. Scans request headers for placeholder values (e.g., NETCLODE_PLACEHOLDER_anthropic)
5. Replaces with real secret from secrets.json
6. Forwards to destination

Secrets are only injected into headers, never request bodies (prevents reflection attacks).