consortium-v2: fix the EOA check of system transaction (axieinfinity#431

)

The EOA check wants to make sure that the sender of system transaction has no
code. The code hash of existing account that has no code is
crypto.Keccak256Hash(nil). Meanwhile, an empty/non-existing account's code hash
is 0x000...00. Currently, we miss the case for empty account, which makes the
system transaction from empty account be rejected.

consensus/consortium/common/contract.go

@@ -312,7 +312,9 @@ func ApplyTransaction(msg types.Message, opts *ApplyTransactOpts) (err error) {
 	expectedHash := signer.Hash(expectedTx)
 
 	sender := msg.From()
-	if codeHash := opts.State.GetCodeHash(sender); codeHash != crypto.Keccak256Hash(nil) {
+	// An empty/non-existing account's code hash is 0x000...00, while an existing account with no code has code hash
+	// that is equal to crypto.Keccak256Hash(nil)
+	if codeHash := opts.State.GetCodeHash(sender); codeHash != crypto.Keccak256Hash(nil) && codeHash != (common.Hash{}) {
 		return fmt.Errorf("%w: address %v, codehash: %s", core.ErrSenderNoEOA, sender.Hex(), codeHash)
 	}
 

consensus/consortium/common/contract_test.go

@@ -48,10 +48,46 @@ func TestApplyTransactionSender(t *testing.T) {
 			Signer: signer,
 		},
 	)
+	// Sender is an empty account, we must not get core.ErrSenderNoEOA
+	if errors.Is(err, core.ErrSenderNoEOA) {
+		t.Fatalf("Don't expect err: %s, have %s", core.ErrSenderNoEOA, err)
+	}
+
+	// Sender is not an empty account but still has no code, we must
+	// not get core.ErrSenderNoEOA
+	state.SetBalance(sender, common.Big1)
+	err = ApplyTransaction(
+		msg,
+		&ApplyTransactOpts{
+			ApplyMessageOpts: &ApplyMessageOpts{
+				State:  state,
+				Header: &types.Header{},
+			},
+			Signer: signer,
+		},
+	)
+	if errors.Is(err, core.ErrSenderNoEOA) {
+		t.Fatalf("Don't expect err: %s, have %s", core.ErrSenderNoEOA, err)
+	}
+
+	// Sender has code, is not an EOA
+	state.SetCode(sender, []byte{0x1})
+	err = ApplyTransaction(
+		msg,
+		&ApplyTransactOpts{
+			ApplyMessageOpts: &ApplyMessageOpts{
+				State:  state,
+				Header: &types.Header{},
+			},
+			Signer: signer,
+		},
+	)
 	if !errors.Is(err, core.ErrSenderNoEOA) {
 		t.Fatalf("Expect err: %s, have %s", core.ErrSenderNoEOA, err)
 	}
 
+	// Sender is an EOA but the sender of system transaction
+	// does not match with coinbase
 	state.SetCode(sender, []byte{})
 	coinbase := common.Address{0x2}
 	err = ApplyTransaction(