@rhino.fi/client-js/src/api/ledger/signEIP712Data.js

const selectTransport = require('../../lib/ledger/selectTransport')
const Eth = require('@ledgerhq/hw-app-eth').default
const { getStructHash } = require('eip-712')

// https://eips.ethereum.org/EIPS/eip-712
module.exports = async (dvf, jsonData, ledgerPath) => {
  const Transport = selectTransport(dvf.isBrowser)
  const createdTransport = await Transport.create()
  const ledgerEth = new Eth(createdTransport)

  const domainStructHash = getStructHash(
    jsonData,
    'EIP712Domain',
    jsonData.domain,
  )
  const domainStructString = Buffer.from(domainStructHash).toString('hex')

  const messageStructHash = getStructHash(
    jsonData,
    jsonData.primaryType,
    jsonData.message,
  )
  const messageStructString = Buffer.from(messageStructHash).toString('hex')

  return ledgerEth
    .signEIP712HashedMessage(
      ledgerPath,
      domainStructString,
      messageStructString,
    )
    .then(signature => {
      return {
        r: Buffer.from(signature.r, 'hex'),
        s: Buffer.from(signature.s, 'hex'),
        v: signature.v,
      }
    })
    .finally(() => {
      createdTransport.close()
    })
}