[Ethereum] Truffle web3.eth.sign produces wrong signature

contract-debuggingecrecoversignaturetruffletruffle-test

Somehow truffle produces an invalid signature.
To clarify this I imported the private key of the first Ganache account to metamask and compared the results.

The following code used in a chrome console returns the following (verifiable correct) signature:

// frontend
let msg = web3.sha3("truffle"); // => 0x28610e27d085e348e6ebd0da2c982947eddf7d308b82e951a896432cdac99a74
let sig;
web3.eth.sign(web3.eth.accounts[0], msg, (err, res) => {
  if(!err) {
    sig = res;
  }
})

// sig => 0xb453386b73ba5608314e9b4c7890a4bd12cc24c2c7bdf5f87778960ff85c56a8520dabdbea357fc561120dd2625bd8a904f35bdb4b153cf706b6ff25bb0d898d1c

Here's the code in truffle which should produce the same signature – but doesn't.

// Truffle:
let first = accounts[0];
let msg = web3.sha3("truffle");
let sig = await web3.eth.sign(first, msg)
// sig => 0x511fafdf71306ff89a063a76b52656c18e9a7d80d19e564c90f0126f732696bb673cde46003aad0ccb6dab2ca91ae38b82170824b0725883875194b273f709b901

This sucks as I am trying to test my contracts which rely on these signatures.

Best Answer

Apparently it's an issue with Truffle, see this issue here. More info here and here.

Related Solutions

Web3js Signature – web3.eth.sign Not Returning Valid Signature

I came across the answer myself, See working code below. I was following this guide which I would not recommend!.

I was also using parity in geth mode to sign the data, which I also would not recommend. Switching to plain old geth RPC gave me more sane results.

That being said, beware of v!. There is a bug between implementations of geth which will return either 00/01 or 1b/1c for v. I solved my problem by using ethereumjs-util's fromRpcSig method, which accounts for the bug. If the following doesn't work try importing web3 and using its sha3 method with ethUtils toBuffer.

Here's a complete snippet of code client side and server side which implement login:

CLIENT

function login() {
  let data = web3.sha3('hello world');
  web3.eth.sign(web3.eth.defaultAccount, data, (err, result) => {
    if (!err) {
      axios.post(url + '/login', {
        addr: web3.eth.defaultAccount,
        sig: result
      }).then((res) => {
        console.log(res);
      });

    }
  });
}

SERVER

var ethUtils = require('ethereumjs-util');

let addr = req.body.addr;
let sig = req.body.sig;

let signature = ethUtils.fromRpcSig(sig);

let data = 'hello world';

let pubKey = ethUtils.ecrecover(
  ethUtils.sha3(data),
  signature.v,
  signature.r,
  signature.s);

let foundAddr = '0x' + ethUtils.pubToAddress(pubKey).toString('hex');

if (foundAddr === addr) {
  // Hooray! The user's signature proves they are who they say they are!
} else {
  // Not authenticated successfully
}

Solidity ecrecover – Using Geth and web3.eth.sign

I was stuck on this issue as well for a very long time.

So the solution is: Add this prefix string to your Solidity smart contract.

function verify(bytes32 hash, uint8 v, bytes32 r, bytes32 s) constant returns(bool) {

    bytes memory prefix = "\x19Ethereum Signed Message:\n32";
    bytes32 prefixedHash = keccak256(prefix, hash);
    return ecrecover(prefixedHash, v, r, s) == (Your Address);
}

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