How can you sign hyperledger-sawtooth transactions using metamask keys? - hyperledger-sawtooth

Question

Hyperledger sawtooth uses secp256k1 ECDSA to sign transactions:
https://sawtooth.hyperledger.org/docs/core/releases/1.2.5/_autogen/txn_submit_tutorial.html?highlight=transaction%20sign
And aparently ethereum uses the same type of signature:
https://hackernoon.com/a-closer-look-at-ethereum-signatures-5784c14abecc
Thus, it would seem that because Metamask is used with Ethereum it would also work with sawtooth. However, I haven't found examples of this, and although I've tried signing transactions with web3.js and ethers.js with Metamask those signatures get rejected by Sawtooth.

Answer 1

It's possible, this is an example I made using web3:0.20.7:
https://github.com/le99/sawtooth-with-metamask-signatures/blob/master/src/App.js
The important function is onClick()
import './App.css';
import React, { useState } from 'react';
var ethUtil = require('ethereumjs-util')
const secp256k1 = require('secp256k1')
const CryptoJS = require('crypto-js');
const axios = require('axios').default;
const cbor = require('cbor')
const Web3 = require('web3');
//https://github.com/ethereum/web3.js/blob/0.20.7/DOCUMENTATION.md
// let web3 = new Web3(Web3.givenProvider || "ws://localhost:8545");
let web3;
if (typeof window.web3 !== 'undefined') {
web3 = new Web3(window.web3.currentProvider);
} else {
// set the provider you want from Web3.providers
web3 = new Web3(new Web3.providers.HttpProvider("http://localhost:8545"));
}
const hash = (x) =>
CryptoJS.SHA512(x).toString(CryptoJS.enc.Hex)
// https://stackoverflow.com/questions/33914764/how-to-read-a-binary-file-with-filereader-in-order-to-hash-it-with-sha-256-in-cr
function arrayBufferToWordArray(ab) {
var i8a = new Uint8Array(ab);
var a = [];
for (var i = 0; i < i8a.length; i += 4) {
a.push(i8a[i] << 24 | i8a[i + 1] << 16 | i8a[i + 2] << 8 | i8a[i + 3]);
}
return CryptoJS.lib.WordArray.create(a, i8a.length);
}
async function onClick(){
const ethereum = window.ethereum;
var from = web3.eth.accounts[0]
// var msgHash = ethUtil.keccak256(Buffer.from('An amazing message, for use with MetaMask!'))
var msgHash = Buffer.from('8144a6fa26be252b86456491fbcd43c1de7e022241845ffea1c3df066f7cfede', 'hex');
console.log(from);
let signature1 = await new Promise((resolve, reject)=>{
web3.eth.sign(from, msgHash, function (err, result) {
if (err) return reject(err)
return resolve(result)
})
});
const rpk3 = secp256k1.ecdsaRecover(Uint8Array.from(Buffer.from(signature1.slice(2, -2), 'hex')), parseInt(signature1.slice(-2), 16) - 27, Uint8Array.from(msgHash));
let publicKey = Buffer.from(rpk3, 'hex').toString('hex')
console.log(msgHash.toString('hex'));
console.log(signature1);
console.log(publicKey);
console.log();
const INT_KEY_FAMILY = 'intkey'
const INT_KEY_NAMESPACE = hash(INT_KEY_FAMILY).substring(0, 6)
const address = INT_KEY_NAMESPACE + hash('foo').slice(-64)
console.log('address:',address);
const payload = {
Verb: 'set',
Name: 'foo',
Value: 41
}
console.log('public:', publicKey);
const payloadBytes = cbor.encode(payload)
const protobuf = require('sawtooth-sdk/protobuf')
const transactionHeaderBytes = protobuf.TransactionHeader.encode({
familyName: 'intkey',
familyVersion: '1.0',
inputs: [address],
outputs: [address],
signerPublicKey: publicKey,
// In this example, we're signing the batch with the same private key,
// but the batch can be signed by another party, in which case, the
// public key will need to be associated with that key.
batcherPublicKey: publicKey,
// In this example, there are no dependencies. This list should include
// an previous transaction header signatures that must be applied for
// this transaction to successfully commit.
// For example,
// dependencies: ['540a6803971d1880ec73a96cb97815a95d374cbad5d865925e5aa0432fcf1931539afe10310c122c5eaae15df61236079abbf4f258889359c4d175516934484a'],
dependencies: [],
payloadSha512: CryptoJS.SHA512(arrayBufferToWordArray(payloadBytes)).toString(CryptoJS.enc.Hex),
nonce:"hey4"
}).finish()
let sss=CryptoJS.SHA256(arrayBufferToWordArray(transactionHeaderBytes)).toString(CryptoJS.enc.Hex);
let dataHash=Uint8Array.from(Buffer.from(sss, 'hex'));
let signature = await new Promise((resolve, reject)=>{
web3.eth.sign(from, dataHash, function (err, result) {
if (err) return reject(err)
return resolve(result)
})
});
signature = signature.slice(2, -2)
console.log('sha1:', CryptoJS.SHA512(arrayBufferToWordArray(transactionHeaderBytes)).toString(CryptoJS.enc.Hex))
console.log('signature1:', signature)
const transaction = protobuf.Transaction.create({
header: transactionHeaderBytes,
headerSignature: signature,
payload: payloadBytes
})
//--------------------------------------
//Optional
//If sending to sign outside
const txnListBytes = protobuf.TransactionList.encode({transactions:[
transaction
]}).finish()
//const txnBytes2 = transaction.finish()
let transactions = protobuf.TransactionList.decode(txnListBytes).transactions;
//----------------------------------------
//transactions = [transaction]
const batchHeaderBytes = protobuf.BatchHeader.encode({
signerPublicKey: publicKey,
transactionIds: transactions.map((txn) => txn.headerSignature),
}).finish()
//
sss=CryptoJS.SHA256(arrayBufferToWordArray(batchHeaderBytes)).toString(CryptoJS.enc.Hex);
dataHash=Uint8Array.from(Buffer.from(sss, 'hex'));
signature = await new Promise((resolve, reject)=>{
web3.eth.sign(from, dataHash, function (err, result) {
if (err) return reject(err)
return resolve(result)
})
});
signature = signature.slice(2, -2)
const batch = protobuf.Batch.create({
header: batchHeaderBytes,
headerSignature: signature,
transactions: transactions
})
const batchListBytes = protobuf.BatchList.encode({
batches: [batch]
}).finish()
console.log(Buffer.from(batchListBytes).toString('hex'));
console.log('batchListBytes has the batch bytes that ca be sent to sawtooth')
// axios.post(`${HOST}/batches`, batchListBytes, {
// headers: {'Content-Type': 'application/octet-stream'}
// })
// .then((response) => {
// console.log(response.data);
// })
// .catch((err)=>{
// console.log(err);
// });
}
The example is based on:
https://sawtooth.hyperledger.org/docs/core/releases/1.2.6/_autogen/sdk_submit_tutorial_js.html
There is a lot of low level stuff, hyperledger and Metamask represent signatures slightly differently. Also most libraries for Metamask automatically wrap the data (https://web3js.readthedocs.io/en/v1.2.11/web3-eth-accounts.html#sign), they then hash it using keccak256, and that hash is what is finnally signed with secp256k1, which is not what you need for Sawtooth.
An example where no wraping or intermediaries are used to sign is: https://github.com/danfinlay/js-eth-personal-sign-examples/blob/master/index.js