wallet/pkg/eth/eth_account.go

package eth

import (
	"crypto/ecdsa"
	"strings"

	"git.pspay.io/crypto-stories/custodial/pkg/locker"
	"github.com/btcsuite/btcd/chaincfg"
	"github.com/btcsuite/btcutil/hdkeychain"
	"github.com/ethereum/go-ethereum/accounts"
	"github.com/ethereum/go-ethereum/common"
	"github.com/ethereum/go-ethereum/crypto"
	"github.com/tyler-smith/go-bip39"
)

const MAX_ACCOUNT_INDEX int = 4294967295

type EthAccount struct {
	privateKey *ecdsa.PrivateKey
	publicKey  *ecdsa.PublicKey
	address    common.Address
}

func (e *EthAccount) PrivateKey() *ecdsa.PrivateKey {
	return e.privateKey
}

func (e *EthAccount) PublicKey() *ecdsa.PublicKey {
	return e.publicKey
}

func (e *EthAccount) Address() common.Address {
	return e.address
}

const path = "m/44'/60'/0'/0"

var master *hdkeychain.ExtendedKey

func InitMaster(mnemonic, passphrase string) {
	if master != nil {
		return
	}

	seed := bip39.NewSeed(strings.TrimSpace(mnemonic), strings.TrimSpace(passphrase))
	dpath, err := accounts.ParseDerivationPath(path)
	if err != nil {
		panic(err)
	}

	key, err := hdkeychain.NewMaster(seed, &chaincfg.MainNetParams)
	if err != nil {
		panic(err)
	}

	for _, n := range dpath {
		key, err = key.Child(n)
		if err != nil {
			panic(err)
		}
	}

	master = key
	privateKey, err := key.ECPrivKey()
	privateKeyECDSA := privateKey.ToECDSA()
	if err != nil {
		panic(err)
	}

	publicKey := privateKeyECDSA.Public()
	_, ok := publicKey.(*ecdsa.PublicKey)
	if !ok {
		panic("error casting public key to ECDSA")
	}

}

func InitMasterFromPrivateSettings() {
	mnemonic := locker.GetPrivateEnv("BIP39_MNEMONIC")
	passphrase := locker.GetPrivateEnv("PASSPHRASE")
	if mnemonic == "" {
		panic("BIP39_MNEMONIC is not set")
	}
	InitMaster(mnemonic, passphrase)
}

func DeriveAccount(index int) (*EthAccount, error) {

	address, err := master.Child(uint32(index))
	if err != nil {
		return nil, err
	}

	privateKey, err := address.ECPrivKey()

	privateKeyECDSA := privateKey.ToECDSA()
	if err != nil {
		return nil, err
	}

	publicKey, _ := address.ECPubKey()
	publicKeyECDSA := publicKey.ToECDSA()

	e := EthAccount{
		privateKey: privateKeyECDSA,
		publicKey:  publicKeyECDSA,
		address:    crypto.PubkeyToAddress(*publicKeyECDSA),
	}

	return &e, nil
}

func GetSpender() (*EthAccount, error){
	return DeriveAccount(MAX_ACCOUNT_INDEX)
}