Create keyed transaction with chain ID in host chain utils package

Instead of just calling bind.NewKeyedTransactorWithChainID we need to
have two different versions - one for Ethereum and one for Celo.

Celo codebase does not have bind.NewKeyedTransactorWithChainID function
yet so we need to create EIP155-compatible transactor manually while for
go-ethereum we can just use bind.NewKeyedTransactorWithChainID.

We can get rid of a host-chain-specific approach when
celo-org/celo-blockchain merges in changes from upstream
ethereum/go-ethereum beyond v1.9.25.

Constructing the transactor manually in the contract template just like
before is not an option because bind.SignerFn has a different signature
for ethereum/go-ethereum and celo-org/celo-blockchain.

Author: pdyraga

pkg/chain/celo/celoutil/celoutil.go

@@ -2,19 +2,23 @@ package celoutil
 
 import (
 	"context"
+	"crypto/ecdsa"
 	"fmt"
+	"io/ioutil"
+	"math/big"
+	"time"
+
 	"github.com/celo-org/celo-blockchain"
 	"github.com/celo-org/celo-blockchain/accounts/abi"
 	"github.com/celo-org/celo-blockchain/accounts/abi/bind"
 	"github.com/celo-org/celo-blockchain/accounts/keystore"
 	"github.com/celo-org/celo-blockchain/common"
+	"github.com/celo-org/celo-blockchain/core/types"
+	"github.com/celo-org/celo-blockchain/crypto"
 	celoclient "github.com/celo-org/celo-blockchain/ethclient"
 	"github.com/celo-org/celo-blockchain/rpc"
 	"github.com/ipfs/go-log"
 	"github.com/keep-network/keep-common/pkg/chain/ethlike"
-	"io/ioutil"
-	"math/big"
-	"time"
 )
 
 var logger = log.Logger("keep-celoutil")
@@ -227,3 +231,37 @@ func NewNonceManager(
 		ethlike.Address(account),
 	)
 }
+
+// NewKeyedTransactorWithChainID is a utility method to easily create
+// a transaction signer from a single private key.
+// FIXME Remove this function and rely on bind.NewKeyedTransactorWithChainID
+// FIXME when celo-org/celo-blockchain merges in changes from upstream
+// FIXME ethereum/go-ethereum beyond v1.9.25.
+func NewKeyedTransactorWithChainID(
+	key *ecdsa.PrivateKey,
+	chainID *big.Int,
+) (*bind.TransactOpts, error) {
+	keyAddress := crypto.PubkeyToAddress(key.PublicKey)
+	if chainID == nil {
+		return nil, fmt.Errorf("no chain id specified")
+	}
+	return &bind.TransactOpts{
+		From: keyAddress,
+		Signer: func(
+			_ types.Signer,
+			address common.Address,
+			tx *types.Transaction,
+		) (*types.Transaction, error) {
+			signer := types.NewEIP155Signer(chainID)
+
+			if address != keyAddress {
+				return nil, fmt.Errorf("not authorized to sign this account")
+			}
+			signature, err := crypto.Sign(signer.Hash(tx).Bytes(), key)
+			if err != nil {
+				return nil, err
+			}
+			return tx.WithSignature(signer, signature)
+		},
+	}, nil
+}

pkg/chain/ethereum/ethutil/ethutil.go

@@ -4,6 +4,7 @@ package ethutil
 
 import (
 	"context"
+	"crypto/ecdsa"
 	"fmt"
 	"io/ioutil"
 	"math/big"
@@ -218,3 +219,12 @@ func NewNonceManager(
 		ethlike.Address(account),
 	)
 }
+
+// NewKeyedTransactorWithChainID is a utility method to easily create
+// a transaction signer from a single private key.
+func NewKeyedTransactorWithChainID(
+	privateKey *ecdsa.PrivateKey,
+	chainID *big.Int,
+) (*bind.TransactOpts, error) {
+	return bind.NewKeyedTransactorWithChainID(privateKey, chainID)
+}

tools/generators/ethlike/contract.go.tmpl

@@ -57,7 +57,10 @@ func New{{.Class}}(
 		From: accountKey.Address,
 	}
 
-	transactorOptions, err := bind.NewKeyedTransactorWithChainID(
+	// FIXME Switch to bind.NewKeyedTransactorWithChainID when
+	// FIXME celo-org/celo-blockchain merges in changes from upstream
+	// FIXME ethereum/go-ethereum beyond v1.9.25.
+	transactorOptions, err := chainutil.NewKeyedTransactorWithChainID(
 		accountKey.PrivateKey,
 		chainId,
 	)

tools/generators/ethlike/contract_template_content.go

@@ -60,7 +60,10 @@ func New{{.Class}}(
 		From: accountKey.Address,
 	}
 
-	transactorOptions, err := bind.NewKeyedTransactorWithChainID(
+	// FIXME Switch to bind.NewKeyedTransactorWithChainID when
+	// FIXME celo-org/celo-blockchain merges in changes from upstream
+	// FIXME ethereum/go-ethereum beyond v1.9.25.
+	transactorOptions, err := chainutil.NewKeyedTransactorWithChainID(
 		accountKey.PrivateKey,
 		chainId,
 	)