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How to bypass BitGo's error when using a Ledger wallet

BitGo recently updated the version of its bitcoinjs-lib dependency, but failed to update the code that interacted with legacy wallets that relied on Ledger hardware wallets. This triggered a r.bufferutils.varIntSize is not a function error whenever trying to use the funds in the wallet. Following is a workaround you can use to manually patch the error, and get your funds out of BitGo.

Disclaimer: I set up this workaround to help a friend rescue their funds. I have no idea if it works for every instance of this error, and it may lead to loss of funds. I strongly suggest that you try it out with a small amount before you attempt to remove all your bitcoin from BitGo.

The problem

The problem seems to happen when interacting with a legacy wallet managed by a Ledger hardware wallet. You have a legacy wallet if BitGo displays the following notice when you open your wallet (fun fact: the link to the instructions to mi

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pragma solidity ^0.7.0;

// Each mining pool that intends to provide flash loans deploys a Loaner contract and transfers ETH to it
// When testing each bundle, the diff in balance in this contract is taking into account for calculating effective gas price
// The contract loans funds only on blocks mined by the miner and on zero-gasprice txs
contract Loaner {
    address immutable owner;
    
    constructor(address _owner) {
        owner = _owner;

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Falsehoods that Ethereum programmers believe

I recently stumbled upon Falsehoods programmers believe about time zones, which got a good laugh out of me. It reminded me of other great lists of falsehoods, such as about names or time, and made me look for an equivalent for Ethereum. Having found none, here is my humble contribution to this set.

About Gas

Calling estimateGas will return the gas required by my transaction

Calling estimateGas will return the gas that your transaction would require if it were mined now. The current state of the chain may be very different to the state in which your tx will get mined. So when your tx i

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#! /usr/bin/env node

const TEMPLATE_FILENAME = 'template.yaml';
const WEBPACK_CONFIG = './api/webpack.config.js';
const WEBPACK_CONTEXT = './api';
const STACKNAME = process.env.STACKNAME;

const { Lambda, CloudFormation } = require('aws-sdk');
const { yamlParse } = require('yaml-cfn');
const { readFileSync } = require('fs');

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export async function tryGetRevertReason(to: string, from: string, data: string): Promise<string | undefined> {
  const provider = ethers.getDefaultProvider();
  const tx = { to, from, data };
  try {
    await provider.estimateGas(tx);
  } catch {
    const value = await provider.call(tx);
    return hexDataLength(value) % 32 === 4 && hexDataSlice(value, 0, 4) === '0x08c379a0'
      ? defaultAbiCoder.decode(['string'], hexDataSlice(value, 4))
      : undefined;

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AWS_ACCOUNT_ID= # aws account
AWS_USER_PROFILE= # profile in aws/credentials to your access key
AWS_REGION= # default region
AWS_IAM_NAME= # your iam name in the aws account
ARN_OF_ROLE= # the role you want to assume

ARN_OF_MFA=arn:aws:iam::$AWS_ACCOUNT_ID:mfa/$AWS_IAM_NAME
MFA_TOKEN_CODE=$1

read AWS_ACCESS_KEY_ID AWS_SECRET_ACCESS_KEY AWS_SESSION_TOKEN <<< \

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#!/usr/bin/env python3

import json
import subprocess
import sys
import re

VERSIONS = [f'0.5.{minor}' for minor in range(0,16)]
RUNS = [0, 100, 200, 300]
TARGETS = ['byzantium', 'constantinople', 'petersburg', 'istanbul']

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Manual setup for a GSN relayer

⚠️ This setup is only good for GSNv1. Head over to https://docs.opengsn.org for the latest setup for GSNv2.

Install nginx and certbot

sudo add-apt-repository universe
sudo add-apt-repository ppa:certbot/certbot
sudo apt-get update
sudo apt-get install nginx software-properties-common certbot python-certbot-nginx

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[
  {
    "constant": false,
    "inputs": [
      {
        "name": "newImplementation",
        "type": "address"
      }
    ],
    "name": "upgradeTo",

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contract RepoPackage {
  event NewVersion(uint256 versionId, uint16[3] semanticVersion);

  struct Version {
    uint16[3] semanticVersion;
    address contractAddress;
    bytes contentURI;
  }

  mapping (bytes32 => Version) versions;