searcher-sponsored-tx

This repository contains a simple Flashbots "searcher" for submitting a transaction from an executor account, but paying for the transaction from a sponsor account. This is accomplished by submitting a Flashbots transaction bundle, with the first "sponsor" transaction paying the "executor" wallet in ETH, followed by a series of executor transactions that spend this newly received ETH on gas fees.

We hope you will use this repository as an example of how to integrate Flashbots into your own Flashbot searcher (bot). For more information, see the Flashbots Searcher Quick Start

Use case

The use case for this multi-transaction setup is to make calls from an account that has a compromised private key. Since transferring in any ETH to this compromised wallet will immediately be swept by bots that monitor that account, transferring in funds will also give any attacker the ability to withdraw tokens that are held by that account.

Using this searcher, you can create a bundle of transaction that execute against the compromised account, spending ETH that was received in the same block.

With the activation of EIP-1559, the old method of using gasPrice = 0 is no longer functional. Transactions must pay at least baseFee.

Environment Variables

• ETHEREUM_RPC_URL - Ethereum RPC endpoint. Can not be the same as FLASHBOTS_RPC_URL
• PRIVATE_KEY_EXECUTOR - Private key for the compromised Ethereum EOA that owns assets that needs to be transferred
• PRIVATE_KEY_SPONSOR - Private key for an account that has ETH that will be used to fund the miner for the "ZERO_GAS" transactions
• RECIPIENT - Ethereum EOA to receive assets from ZERO_GAS account
• FLASHBOTS_RELAY_SIGNING_KEY - Optional param, private key used to sign messages to Flashbots to establish reputation of profitability

Setting Miner Reward

Inside src/index.ts is :

const PRIORITY_GAS_PRICE = GWEI.mul(31)

This is the priority fee, on top of baseFee, sent to the miner for all transactions in the bundle, including the sponsor-funding transaction. All transactions use the same gasPrice, with no coinbase transfers in any transaction. In the case of a block re-organization, hopefully all transactions will appear in the next block as well, preventing sweeper bots from gaining access to the incoming ETH before it is spent on gas fees.

Selecting a different "engine"

This system can operate against different protocols by swapping a new "engine" class that adheres to "Base" functionality in the main() function. Available engines:

• TransferERC20
• CryptoKitties
• Approval721

An engine accepts relevant parameters during construction and provides functions to retrieve transaction descriptions to be passed in to Flashbots. Selecting and configuring a different engine requires directly modifying the source, uncommenting the engine and setting the necessary variables.

Usage

$ npm install

# First create/update .env and populate environment variables
cp example.env .env

$ npm run start

Analyze Account

• Check account on etherscan
• Check account on opensea

TODO

• It would be nice to have a tool that searched the transaction history for an account, and recorded all tokens/NFTs received as part of those transactions, then reviewed all tokens received outside of a transaction and compared them against lists of known good tokens. The goal being to quickly identify valuable tokens and ignore scam tokens.
• It would be nice for the multitoken engine to report how much gas would be used by running the list of tx so they could be prioritized
• Break the send eth into something more official than a commented out code block