casm-provider

Express middleware for x402 payment challenges in CASM (Cronos Agentic Service Mesh).

Installation

npm install casm-provider

Quick Start

const express = require('express');
const { createPaymentMiddleware } = require('casm-provider');

const app = express();

// Create payment middleware
const requirePayment = createPaymentMiddleware({
  recipientAddress: '0xYourWalletAddress',
  price: 50000, // 0.05 USDC (6 decimals)
  tokenAddress: '0x...USDC_ADDRESS',
  facilitatorUrl: 'https://x402.cronos.org',
  chainId: 338, // Cronos testnet
});

// Protect your API endpoint
app.get('/api/premium-data', requirePayment, (req, res) => {
  // Payment verified! Return data
  res.json({
    success: true,
    paymentVerified: req.paymentVerified,
    data: { /* your premium data */ }
  });
});

app.listen(3001);

How It Works

1. Request without payment → Returns 402 Payment Required with a challenge
2. Request with valid signature → Verifies via x402 Facilitator → Returns data

402 Response Format

{
  "error": "Payment Required",
  "challenge": {
    "version": "1.0",
    "network": "cronos-testnet",
    "chainId": 338,
    "recipient": "0x...",
    "amount": "50000",
    "token": "0x...USDC",
    "nonce": "abc123...",
    "deadline": 1705000000,
    "facilitator": "https://x402.cronos.org",
    "message": "Pay 0.05 USDC to access this API"
  }
}

API Reference

createPaymentMiddleware(options)

Creates Express middleware for payment enforcement.

| Option | Type | Required | Description | |--------|------|----------|-------------| | recipientAddress | string | ✅ | Wallet to receive payments | | price | number | ✅ | Price in atomic units | | tokenAddress | string | ✅ | USDC token address | | facilitatorUrl | string | ✅ | x402 Facilitator URL | | chainId | number | | Chain ID (default: 338) |

verifyPaymentSignature(params)

Verify a payment signature via the x402 Facilitator.

const { verifyPaymentSignature } = require('casm-provider');

const isValid = await verifyPaymentSignature({
  signature: '0x...',
  nonce: 'abc123',
  recipientAddress: '0x...',
  amount: 50000,
  tokenAddress: '0x...USDC',
  facilitatorUrl: 'https://x402.cronos.org',
  chainId: 338,
});

License

MIT