Extracting the Sender from a Transaction with Go-Ethereum

When working with Ethereum transactions in Go, extracting the sender (the address that initiated the transaction) is not straightforward. The go-ethereum library provides the necessary tools, but you need to follow a specific process to get the sender's address. This post will guide you through the steps required to extract the sender from a transaction using go-ethereum.

Prerequisites

Before we dive in, make sure you have the following:

Go installed on your machine.
The go-ethereum package installed. If not, you can install it using:

go get github.com/ethereum/go-ethereum

Step-by-Step Guide

Import Necessary Packages

Start by importing the necessary packages in your Go file:

package main

import (
    "log"
    "github.com/ethereum/go-ethereum/core/types"
    "github.com/ethereum/go-ethereum/ethclient"
)

Get the Chain ID

The chain ID is essential for signing and verifying transactions. Here’s a helper function to get the chain ID:

func getChainId() (*big.Int, error) {
    client, err := ethclient.Dial("https://mainnet.infura.io/v3/YOUR_INFURA_PROJECT_ID")
    if err != nil {
        return nil, err
    }

    chainID, err := client.NetworkID(context.Background())
    if err != nil {
        return nil, err
    }

    return chainID, nil
}

Extract the Sender

Here’s the core function to extract the sender from a transaction:

func getTxSender(tx *types.Transaction) (string, error) {
    chainId, err := getChainId()
    if err != nil {
        log.Fatal("Failed to get chainId:", err)
        return "", err
    }

    sender, err := types.Sender(types.NewLondonSigner(chainId), tx)
    if err != nil {
        log.Fatal("Not able to retrieve sender:", err)
        return "", err
    }

    return sender.Hex(), nil
}

This function retrieves the chain ID, and then uses the types.Sender function with a NewLondonSigner to get the sender’s address. The NewLondonSigner is used to handle transactions post-EIP-1559 (the London hard fork).

Usage Example

func main() {
    // Example transaction hash
    txHash := "0x..."

    // Connect to Ethereum client
    client, err := ethclient.Dial("https://mainnet.infura.io/v3/YOUR_INFURA_PROJECT_ID")
    if err != nil {
        log.Fatal("Failed to connect to the Ethereum client:", err)
    }

    // Get the transaction
    tx, _, err := client.TransactionByHash(context.Background(), common.HexToHash(txHash))
    if err != nil {
        log.Fatal("Failed to retrieve transaction:", err)
    }

    // Get the sender
    sender, err := getTxSender(tx)
    if err != nil {
        log.Fatal("Failed to get transaction sender:", err)
    }

    log.Printf("Transaction was sent by: %s", sender)
}

Conclusion

Extracting the sender from a transaction in Go using go-ethereum involves retrieving the chain ID and using the appropriate signer. This method ensures compatibility with transactions after the London hard fork. With the provided code snippets, you should be able to implement this functionality in your Go applications easily.

Feel free to leave comments or ask questions if you encounter any issues. Happy coding!

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Extracting the Sender from a Transaction with Go-Ethereum

Rodrigo Burgos

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