accounts, cmd, contracts, les: integrate clef for transaction signing (#19783)

* accounts, cmd, contracts, les: integrate clef for transaction signing

* accounts, cmd/checkpoint-admin, signer/core: minor fixups

accounts/abi/bind/auth.go

@@ -23,6 +23,7 @@ import (
 	"io/ioutil"
 
 	"github.com/ethereum/go-ethereum/accounts"
+	"github.com/ethereum/go-ethereum/accounts/external"
 	"github.com/ethereum/go-ethereum/accounts/keystore"
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/core/types"
@@ -43,7 +44,7 @@ func NewTransactor(keyin io.Reader, passphrase string) (*TransactOpts, error) {
 	return NewKeyedTransactor(key.PrivateKey), nil
 }
 
-// NewKeystoreTransactor is a utility method to easily create a transaction signer from
+// NewKeyStoreTransactor is a utility method to easily create a transaction signer from
 // an decrypted key from a keystore
 func NewKeyStoreTransactor(keystore *keystore.KeyStore, account accounts.Account) (*TransactOpts, error) {
 	return &TransactOpts{
@@ -79,3 +80,17 @@ func NewKeyedTransactor(key *ecdsa.PrivateKey) *TransactOpts {
 		},
 	}
 }
+
+// NewClefTransactor is a utility method to easily create a transaction signer
+// with a clef backend.
+func NewClefTransactor(clef *external.ExternalSigner, account accounts.Account) *TransactOpts {
+	return &TransactOpts{
+		From: account.Address,
+		Signer: func(signer types.Signer, address common.Address, transaction *types.Transaction) (*types.Transaction, error) {
+			if address != account.Address {
+				return nil, errors.New("not authorized to sign this account")
+			}
+			return clef.SignTx(account, transaction, nil) // Clef enforces its own chain id
+		},
+	}
+}

accounts/external/backend.go

@@ -182,18 +182,21 @@ func (api *ExternalSigner) SignText(account accounts.Account, text []byte) ([]by
 
 func (api *ExternalSigner) SignTx(account accounts.Account, tx *types.Transaction, chainID *big.Int) (*types.Transaction, error) {
 	res := ethapi.SignTransactionResult{}
-	to := common.NewMixedcaseAddress(*tx.To())
 	data := hexutil.Bytes(tx.Data())
+	var to *common.MixedcaseAddress
+	if tx.To() != nil {
+		t := common.NewMixedcaseAddress(*tx.To())
+		to = &t
+	}
 	args := &core.SendTxArgs{
 		Data:     &data,
 		Nonce:    hexutil.Uint64(tx.Nonce()),
 		Value:    hexutil.Big(*tx.Value()),
 		Gas:      hexutil.Uint64(tx.Gas()),
 		GasPrice: hexutil.Big(*tx.GasPrice()),
-		To:       &to,
+		To:       to,
 		From:     common.NewMixedcaseAddress(account.Address),
 	}
-
 	if err := api.client.Call(&res, "account_signTransaction", args); err != nil {
 		return nil, err
 	}