searcher-sponsored-tx

This repository contains a simple Flashbots "searcher" for submitting a transaction from account X, but paying for the transaction from account Y. This is accomplished by submitting a Flashbots transaction bundle, with the first transaction(s) executing from account X, and the last, single transaction calling a contract which verifies the early transactions ran successfully, then pays the miner.

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 FAQ

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 0-gas-price transaction that execute against the compromised account, then reward the miner in a later transaction from a non-compromised account. The last transaction should execute a contract function to ensure the earlier transaction ran successfully (both to avoid mistakes AND to ensure the miner can't simply take the reward transaction without processing the 0-gas-price transactions).

Environment Variables

ETHEREUM_RPC_URL - Ethereum RPC endpoint. Can not be the same as FLASHBOTS_RPC_URL
PRIVATE_KEY_ZERO_GAS - Private key for the compromised Ethereum EOA that owns assets that needs to be transferred
PRIVATE_KEY_DONOR - 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

Setting Miner Reward

Inside src/index.ts is :

const MINER_REWARD_IN_WEI = ETHER.div(1000).mul(12); // 0.012 ETH

This is the amount, in wei, sent to block.coinbase from the DONOR EOA. This value is specified in TypeScript, instead of an ENVIRONMENT variable, due to how important it is. Setting this to a very large value could result in massive losses of funds to the DONOR EOA. For safety, do not store large amounts of eth in DONOR EOA

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

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