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79 lines
2.7 KiB
79 lines
2.7 KiB
const utils = require('ethereumjs-util');
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const { soliditySha3 } = require('web3-utils');
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const REAL_SIGNATURE_SIZE = 2 * 65; // 65 bytes in hexadecimal string legnth
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const PADDED_SIGNATURE_SIZE = 2 * 96; // 96 bytes in hexadecimal string length
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const DUMMY_SIGNATURE = `0x${web3.padLeft('', REAL_SIGNATURE_SIZE)}`;
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/**
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* Hash and add same prefix to the hash that ganache use.
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* @param {string} message the plaintext/ascii/original message
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* @return {string} the hash of the message, prefixed, and then hashed again
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*/
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function hashMessage (message) {
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const messageHex = Buffer.from(utils.sha3(message).toString('hex'), 'hex');
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const prefix = utils.toBuffer('\u0019Ethereum Signed Message:\n' + messageHex.length.toString());
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return utils.bufferToHex(utils.sha3(Buffer.concat([prefix, messageHex])));
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}
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// signs message in node (auto-applies prefix)
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// message must be in hex already! will not be autoconverted!
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const signMessage = (signer, message = '') => {
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return web3.eth.sign(signer, message);
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};
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// @TODO - remove this when we migrate to web3-1.0.0
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const transformToFullName = function (json) {
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if (json.name.indexOf('(') !== -1) {
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return json.name;
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}
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const typeName = json.inputs.map(function (i) { return i.type; }).join();
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return json.name + '(' + typeName + ')';
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};
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/**
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* Create a signer between a contract and a signer for a voucher of method, args, and redeemer
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* Note that `method` is the web3 method, not the truffle-contract method
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* Well truffle is terrible, but luckily (?) so is web3 < 1.0, so we get to make our own method id
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* fetcher because the method on the contract isn't actually the SolidityFunction object ಠ_ಠ
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* @param contract TruffleContract
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* @param signer address
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* @param redeemer address
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* @param methodName string
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* @param methodArgs any[]
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*/
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const getBouncerSigner = (contract, signer) => (redeemer, methodName, methodArgs = []) => {
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const parts = [
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contract.address,
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redeemer,
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];
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// if we have a method, add it to the parts that we're signing
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if (methodName) {
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if (methodArgs.length > 0) {
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parts.push(
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contract.contract[methodName].getData(...methodArgs.concat([DUMMY_SIGNATURE])).slice(
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0,
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-1 * PADDED_SIGNATURE_SIZE
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)
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);
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} else {
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const abi = contract.abi.find(abi => abi.name === methodName);
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const name = transformToFullName(abi);
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const signature = web3.sha3(name).slice(0, 10);
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parts.push(signature);
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}
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}
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// ^ substr to remove `0x` because in solidity the address is a set of byes, not a string `0xabcd`
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const hashOfMessage = soliditySha3(...parts);
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return signMessage(signer, hashOfMessage);
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};
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module.exports = {
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hashMessage,
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signMessage,
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getBouncerSigner,
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};
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