const { numberToHex, toWei, toHex, toBN } = require('web3-utils') const Web3 = require('web3') const express = require('express') const app = express() app.use(express.json()) app.use(function(req, res, next) { res.header('Access-Control-Allow-Origin', '*') res.header('Access-Control-Allow-Headers', 'Origin, X-Requested-With, Content-Type, Accept') next() }) const { netId, rpcUrl, privateKey, mixerAddress, defaultGasPrice, desiredFee } = require('./config') const { fetchGasPrice, isValidProof } = require('./utils') const web3 = new Web3(rpcUrl, null, { transactionConfirmationBlocks: 1 }) const account = web3.eth.accounts.privateKeyToAccount('0x' + privateKey) web3.eth.accounts.wallet.add('0x' + privateKey) web3.eth.defaultAccount = account.address const mixerABI = require('./mixerABI.json') const mixer = new web3.eth.Contract(mixerABI, mixerAddress) const gasPrices = { fast: defaultGasPrice } app.get('/', function (req, res) { // just for testing purposes res.send(`Tornado mixer relayer. Gas Price is ${JSON.stringify(gasPrices)}`) }) app.post('/relay', async (req, resp) => { const { valid , reason } = isValidProof(req.body) if (!valid) { console.log('Proof is invalid:', reason) return resp.status(400).send('Proof is invalid') } let { pi_a, pi_b, pi_c, publicSignals } = req.body const fee = toBN(publicSignals[3]) if (fee.lt(toBN(desiredFee))) { console.log('Fee is too low') return resp.status(400).send('Fee is too low') } try { const nullifier = publicSignals[1] const isSpent = await mixer.methods.isSpent(nullifier).call() if (isSpent) { throw new Error('The note has been spent') } const root = publicSignals[0] const isKnownRoot = await mixer.methods.isKnownRoot(root).call() if (!isKnownRoot) { throw new Error('The merkle root is too old or invalid') } const gas = await mixer.methods.withdraw(pi_a, pi_b, pi_c, publicSignals).estimateGas() const result = mixer.methods.withdraw(pi_a, pi_b, pi_c, publicSignals).send({ gas: numberToHex(gas + 50000), gasPrice: toHex(toWei(gasPrices.fast.toString(), 'gwei')), // TODO: nonce }) result.once('transactionHash', function(hash){ resp.json({ txHash: hash }) }).on('error', function(e){ console.log(e) resp.status(400).send('Proof is malformed') }) } catch (e) { console.log(e) resp.status(400).send('Proof is malformed or spent') } }) app.listen(8000) if (netId === 1) { fetchGasPrice({ gasPrices }) console.log('Gas price oracle started.') }