balancer-verify-message.js

const { verifyMessage } = require('@ethersproject/wallet');

async function verify(signedMessage, sig, address, type) {
  const message = JSON.parse(JSON.stringify(signedMessage));
  if (type === 'author') {
    delete message.authors[0].sig;
    delete message.relayers;
  }
  if (type === 'relayer') delete message.relayers[0].sig;
  const recovered = await verifyMessage(JSON.stringify(message), sig);
  return recovered === address;
}

/** Raw message from IPFS */
const message = {
  version: '0.1.0',
  token: '0xba100000625a3754423978a60c9317c58a424e3D',
  type: 'vote',
  authors: [
    {
      address: '0xeF8305E140ac520225DAf050e2f71d5fBcC543e7',
      timestamp: '1594990541',
      sig: '0x2814c1639aa424c8e1ffb16148c8a230b67c7180c11e29dab7deb6fc1eeb51b32d9050f830c73dd1670164566b7cff182bcdf3595b14976c6a1d00bae883671f1b'
    }
  ],
  payload: {
    proposal: 'QmfDFTmfoGJ7PHSp3mJRMmAutiAxTdznkRicZ5uhmKSpSt',
    choice: 1
  },
  relayers: [
    {
      address: '0x14b48b810B4Bf538054140466ADDC716D17b1eA6',
      timestamp: '1594990548',
      sig: '0xa807642bc0555de43d82d0a24a6321acc78314390af53dc4f2089a6c7d59fe8750e0bca38e68f0595209bd5983f2f0c81c56e9c2c03cb8d77f969cbf245db9cb1b'
    }
  ]
};

/** Verify author signature */
const authorAddress = '0xeF8305E140ac520225DAf050e2f71d5fBcC543e7';
const authorSig = '0x2814c1639aa424c8e1ffb16148c8a230b67c7180c11e29dab7deb6fc1eeb51b32d9050f830c73dd1670164566b7cff182bcdf3595b14976c6a1d00bae883671f1b';

verify(message, authorSig, authorAddress, 'author').then(authorSigIsValid => {
  console.log('Is author sig valid?', authorSigIsValid);
});

/** Verify relayer signature */
const relayerAddress = '0x14b48b810B4Bf538054140466ADDC716D17b1eA6';
const relayerSig = '0xa807642bc0555de43d82d0a24a6321acc78314390af53dc4f2089a6c7d59fe8750e0bca38e68f0595209bd5983f2f0c81c56e9c2c03cb8d77f969cbf245db9cb1b';

verify(message, relayerSig, relayerAddress, 'relayer').then(relayerSigIsValid => {
  console.log('Is relayer sig valid?', relayerSigIsValid);
});

Message signed by author

{"version":"0.1.0","token":"0xba100000625a3754423978a60c9317c58a424e3D","type":"vote","authors":[{"address":"0xeF8305E140ac520225DAf050e2f71d5fBcC543e7","timestamp":"1594990541"}],"payload":{"proposal":"QmfDFTmfoGJ7PHSp3mJRMmAutiAxTdznkRicZ5uhmKSpSt","choice":1}}

Message signed by relayer

{"version":"0.1.0","token":"0xba100000625a3754423978a60c9317c58a424e3D","type":"vote","authors":[{"address":"0xeF8305E140ac520225DAf050e2f71d5fBcC543e7","timestamp":"1594990541","sig":"0x2814c1639aa424c8e1ffb16148c8a230b67c7180c11e29dab7deb6fc1eeb51b32d9050f830c73dd1670164566b7cff182bcdf3595b14976c6a1d00bae883671f1b"}],"payload":{"proposal":"QmfDFTmfoGJ7PHSp3mJRMmAutiAxTdznkRicZ5uhmKSpSt","choice":1},"relayers":[{"address":"0x14b48b810B4Bf538054140466ADDC716D17b1eA6","timestamp":"1594990548"}]}