relay wip

package.json

@@ -26,6 +26,7 @@
     "circom": "0.0.30",
     "circomlib": "^0.0.10",
     "dotenv": "^8.0.0",
+    "express": "^4.17.1",
     "ganache-cli": "^6.4.5",
     "snarkjs": "git+https://github.com/iden3/snarkjs.git#5fe2bd4642ec567c75ad5ac3f73687999c412e73",
     "truffle": "^5.0.27",

relay/relay.js

@@ -0,0 +1,44 @@
+let bigInt = require('snarkjs/src/bigint');
+
+require('dotenv').config();
+const { AMOUNT, MERKLE_TREE_HEIGHT, EMPTY_ELEMENT } = process.env;
+
+const express = require('express');
+const app = express();
+app.use(express.json());
+
+const Web3 = require('web3');
+web3 = new Web3('http://localhost:8545', null, {transactionConfirmationBlocks: 1});
+contractJson = require('../build/contracts/Mixer.json');
+let netId = 42;
+mixer = new web3.eth.Contract(contractJson.abi, contractJson.networks[netId].address);
+
+function getMinimumFee() {
+  // todo calc acceptable fee
+  return 1e16;
+}
+
+app.post('/deposit', async (req, resp) => {
+  let proof = req.body;
+  if (!(proof.pi_a && proof.pi_b && proof.pi_c && proof.publicSignals)) { // check that it's kinda well formed
+    resp.status(400).end();
+  }
+
+  if (bigInt(proof.publicSignals[3]) < getMinimumFee()) {
+    resp.status(403).send("Fee is too low");
+  }
+
+  if (!utils.snarkVerify(proof)) {
+    resp.status(403).send("Invalid snark proof");
+  }
+
+  try {
+    let receipt = await mixer.withdraw(proof.pi_a, proof.pi_b, proof.pi_b, proof.publicSignals);
+    console.log(receipt);
+    resp.send({transaction: receipt.transactionHash})
+  } catch (e) {
+    console.log(e);
+    resp.status(400).send("Transaction was reverted");
+  }
+});
+app.listen(3000);

scripts/utils.js

@@ -10,7 +10,7 @@ const unstringifyBigInts2 = require("snarkjs/src/stringifybigint").unstringifyBi
 const rbigint = (nbytes) => snarkjs.bigInt.leBuff2int(crypto.randomBytes(nbytes));
 const pedersenHash = (data) => babyjub.unpackPoint(pedersen.hash(data))[0];
 
-async function snarkVerify(proof) {
+function snarkVerify(proof) {
   proof = unstringifyBigInts2(websnarkUtils.fromSolidityInput(proof));
   const verification_key = unstringifyBigInts2(require('../build/circuits/withdraw_verification_key.json'));
   return groth.isValid(verification_key, proof, proof.publicSignals);