Allow binary message for wallet.signMessage.

[jennazenk]

hello @ricmoo , what is the equivalent of web.eth.sign() (https://github.com/ethereum/wiki/wiki/JavaScript-API#web3ethsign) in ethers.js ?
I am trying to sign a piece of data in order to retrieve s, r and v from the signature. I tried with Wallet.sign() and also SigningKey.signDigest, but I don't get the same output as when I call web3.eth.sign().

The purpose of that is that I need to call the solidity ecrecover function to verify that my address has signed the data.

Thanks a lot!

[jennazenk]

Just saw this issue was opened #78 . It is a bit related and I've tried both way (with wallet instance and signing key) and I can't find the right output. Also, should signing the same piece of data through the wallet instance or through the signing key output the same data?

[ricmoo]

Hey Jenna!

Can you provide an example of a privateKey (obviously newly created for this sample) as well as data and the output you expect?

Also keep in mind that Web3 treats strings inconsistently. So the string "0x12". is 1 byte long, but the string "12" is two bytes long. And as a result there is no easy way to represent the 4 byte string "0x12", except to expand it to "0x30793132".

[ricmoo]

by the way, have you checked out:

var w = new ethers.Wallet('0x123456789012345678901234567890123456789012345678901234567890123');

var sig = w.signMessage("Hello World");
//'0xe0ed34fbbe927a58267ce2e8067a611c69869e20e731bc99187a8bc97058664c16de07f7660f06ce0985d1d8e063726783033fda59b307897f26a21392d62b3a1c'

var address = ethers.Wallet.verifyMessage("Hello World", sig);
// address === w.address

[jennazenk]

Thanks @ricmoo for your answer! I tried this indeed, and verifyMessage does return my account address. Still, its not the same output as the one I have when signing with api.eth.sign in parity.js .Pinged you on gitter to send you an example

[jennazenk]

Hey @ricmoo , here is some code to reproduce. I used ethereumjs-util (think its easier to reproduce than with parity.js). As you can see, signing with ethers.js and signing with ethereumjs-util doesn't give the same output.

const ethers = require("ethers");
const sigUtil = require("eth-sig-util");
const ethUtil = require("ethereumjs-util");

const hash =
  "0x47173285a8d7341e5e972fc677286384f802f8ef42a5ec5f03bbfa254cb01fad";

const wallet = new ethers.Wallet.fromMnemonic(
  "loan million aware switch length candy artwork finish comfort eyebrow mimic estate"
);
const privateKey = wallet.privateKey;

//SIGN WITH ETHERS-WALLET
const signEthWallet = () => {
  const rawSignature = wallet.signMessage(hash);
  const walletSignature = rawSignature.substr(2, rawSignature.length);
  return {
    fullSignature: rawSignature,
    r: `0x${walletSignature.substr(0, 64)}`,
    s: `0x${walletSignature.substr(64, 64)}`,
    v: parseFloat(walletSignature.substr(128, 2)) + 27
  };
};

//SIGN WITH ETH-SIG-UTIL
const signEthSig = () => {
  const sigUtilSignature = sigUtil.personalSign(ethUtil.toBuffer(privateKey), {
    data: hash
  });
  const personalSignature = sigUtilSignature.substr(2, sigUtilSignature.length);
  return {
    fullSignature: sigUtilSignature,
    r: `0x${personalSignature.substr(0, 64)}`,
    s: `0x${personalSignature.substr(64, 64)}`,
    v: parseFloat(personalSignature.substr(128, 2)) + 27
  };
};

const resultWithEthersJs = signEthWallet();
console.log(resultWithEthersJs);
// { fullSignature: '0x9476cf9425e8cb30f0589915e2900152aa6fcfeb15c097a090db3f43484f1c3d3c3d006896fcedd56b0d574da440347886f0d95a73f2ff013d621d200ab9dee11b',
//   r: '0x9476cf9425e8cb30f0589915e2900152aa6fcfeb15c097a090db3f43484f1c3d',
//   s: '0x3c3d006896fcedd56b0d574da440347886f0d95a73f2ff013d621d200ab9dee1',
//   v: 28 }
const resultWithEthSigUtil = signEthSig();
console.log(resultWithEthSigUtil);
// { fullSignature: '0x546f0c996fa4cfbf2b68fd413bfb477f05e44e66545d7782d87d52305831cd055fc9943e513297d0f6755ad1590a5476bf7d1761d4f9dc07dfe473824bbdec751b',
//   r: '0x546f0c996fa4cfbf2b68fd413bfb477f05e44e66545d7782d87d52305831cd05',
//   s: '0x5fc9943e513297d0f6755ad1590a5476bf7d1761d4f9dc07dfe473824bbdec75',
//   v: 28 }
```

[ricmoo]

Ok, I've found the problem.

I have updated the signMessage API to allow binary data to be passed in. Before it only allowed UTF-8 strings. You will have to make a small change to the above code, since "0x1234" is a valid string (of 6 bytes); the eth-sig-util is using the message as a binary payload.

var hash = "0x47173285a8d7341e5e972fc677286384f802f8ef42a5ec5f03bbfa254cb01fad"

// To use the 66 byte string (not what you want)
wallet.signMessage(hash);

// To use the 32 byte binary data (matches the above eth-sig-util)
var hashData = ethers.utils.arrayify(hash);
wallet.signMessage(hashData);

I've also added your example to the test-cases.

Once Travis-CI has completed, I'll publish to npm and close this issue. You'll have to delete your package-lock.json and node_modules and redo an npm install, but then you should be off to the races. :)

[jennazenk]

Awesome thanks @ricmoo

[ricmoo]

Just published to npm.

Thanks @jennazenk!

[Perseverance]

Thank you @jennazenk and @ricmoo ! This saved me (after spending whole Sunday trying to make it work). I would love for this to be included in the cookbook part of the docs as the most common case would be off-chain wallet.signMessage with on-chain ecrecover (or atleast this is what I would need if I need to implement state chanels). I can provide example if you need!

[ricmoo]

Excellent Point! I will add it to my todo list for the Cookbook.

[Perseverance]

Here is my playground: https://gitlab.com/limelabs/ecrecover-test/tree/master

I feel that in order for this to be a fully comprehensive example the Smart Contract part might be needed too. The meaty part is in scripts/sign.js