CommBank.eth Relayer

Transaction relayer and RPC proxy for CommBank.eth, providing private transaction relay and secure RPC endpoint access with CORS protection.

Features

• Transaction Relay: Allows for submitting of transactions for a gasless UX
• RPC Proxy: Hide RPC credentials and enforce CORS policy

Quick Start

Development

# Install dependencies
pnpm install

# Copy environment configuration
cp .env.example .env

# Edit .env with your RPC URLs and allowed origins

# Run in development mode (with hot reload)
pnpm run dev

# Or build and run in production mode
pnpm run build
pnpm run start

Docker Deployment

# From root
docker build -t commbank-eth-relayer -f relayer/Dockerfile .

# Run the container
docker run -p 3000:3000 commbank-eth-relayer

Configuration

Environment Variables

Create a .env file based on .env.example:

# Server Configuration
PORT=3000
NODE_ENV=production

# CORS Configuration
ALLOWED_ORIGINS=https://commbank.eth.limo,http://localhost:3000,http://localhost:5173

# RPC Endpoints
RPC_ETH_MAINNET=https://eth-mainnet.g.alchemy.com/v2/YOUR_API_KEY
RPC_ETH_SEPOLIA=https://eth-sepolia.g.alchemy.com/v2/YOUR_API_KEY

# Optional: Enable RPC request logging
LOG_RPC_REQUESTS=false

Supported Chain IDs

Chain ID	Network	Environment Variable
1	Ethereum Mainnet	RPC_ETH_MAINNET
11155111	Ethereum Sepolia	RPC_ETH_SEPOLIA

API Endpoints

Health Check

GET /health

Response:

{
  "status": "ok",
  "timestamp": "2024-01-12T10:30:00.000Z"
}

RPC Proxy

POST /rpc/:chainId

Forward JSON-RPC requests to the configured RPC endpoint for the specified chain.

Example: Get latest block on Ethereum Mainnet

curl -X POST http://localhost:3000/rpc/1 \
  -H "Content-Type: application/json" \
  -d '{
    "jsonrpc": "2.0",
    "method": "eth_blockNumber",
    "params": [],
    "id": 1
  }'

Transaction Relay

POST /tx

Submit a zero-knowledge proof transaction for relay.

Request Body:

{
  "proof": {
    "proof": "0x...",
    "publicInputs": ["0x...", "0x..."]
  },
  "payload": ["0x..."]
}

Response:

{
  "success": true,
  "message": "Transaction received and queued for processing",
  "txId": "tx_1234567890_abc123"
}

CORS Security

The relayer enforces CORS to prevent unauthorized access to your RPC endpoints.

Configuration:

Set allowed origins in .env:

ALLOWED_ORIGINS=https://commbank.eth.limo,https://app.example.com

Behavior:

• Requests from allowed origins are permitted
• Requests with no origin (curl, mobile apps) are allowed
• Requests from unauthorized origins are blocked with CORS error

Testing CORS:

# Allowed origin - will succeed
curl -X POST http://localhost:3000/rpc/1 \
  -H "Origin: https://commbank.eth.limo" \
  -H "Content-Type: application/json" \
  -d '{"jsonrpc":"2.0","method":"eth_blockNumber","params":[],"id":1}'

# Unauthorized origin - will fail
curl -X POST http://localhost:3000/rpc/1 \
  -H "Origin: https://malicious-site.com" \
  -H "Content-Type: application/json" \
  -d '{"jsonrpc":"2.0","method":"eth_blockNumber","params":[],"id":1}'