eth_sign_tx: integrate address case feature to go library

see : BitBoxSwiss/bitbox02-firmware@055bda6

For ETH signing legacy and EIP1559 transactions, the BitBox02 device
shows confirmation screens for recipient and amount. For recipient, the
device was previously showing the address in mixed case according to
EIP-55, no matter the case user has entered. This created confusions
among the users.

That is why not the go library detects the case of the recipient address
useer inputted and sends this case information to BitBox02 device, which
will in turn show the recipient address in the same case that it got
from the library.

Signed-off-by: asi345 <inanata15@gmail.com>

Author: asi345

api/firmware/eth.go

@@ -141,6 +141,22 @@ func (device *Device) handleSignerNonceCommitment(response *messages.ETHResponse
 	return signature, nil
 }
 
+// ETHIdentifyCase identifies the case of the recipient address given as hexadecimal string.
+// This function exists as a convenience to potentially help clients to determine the case of the
+// recipient address. The output of the function goes to ETHSign and ETHSignEIP1559 as the
+// recipientAddressCase parameter, which is forwarded to BitBox02 device to reconstruct the address
+// in the correct case(the one that the user enters).
+func ETHIdentifyCase(recipientAddress string) messages.ETHAddressCase {
+	switch {
+	case strings.ToUpper(recipientAddress) == recipientAddress:
+		return messages.ETHAddressCase_ETH_ADDRESS_CASE_UPPER
+	case strings.ToLower(recipientAddress) == recipientAddress:
+		return messages.ETHAddressCase_ETH_ADDRESS_CASE_LOWER
+	default:
+		return messages.ETHAddressCase_ETH_ADDRESS_CASE_MIXED
+	}
+}
+
 // ETHSign signs an ethereum transaction. It returns a 65 byte signature (R, S, and 1 byte recID).
 func (device *Device) ETHSign(
 	chainID uint64,
@@ -150,7 +166,8 @@ func (device *Device) ETHSign(
 	gasLimit uint64,
 	recipient [20]byte,
 	value *big.Int,
-	data []byte) ([]byte, error) {
+	data []byte,
+	recipientAddressCase messages.ETHAddressCase) ([]byte, error) {
 	supportsAntiklepto := device.version.AtLeast(semver.NewSemVer(9, 5, 0))
 
 	var hostNonceCommitment *messages.AntiKleptoHostNonceCommitment
@@ -168,6 +185,7 @@ func (device *Device) ETHSign(
 	if err != nil {
 		return nil, err
 	}
+
 	request := &messages.ETHRequest{
 		Request: &messages.ETHRequest_Sign{
 			Sign: &messages.ETHSignRequest{
@@ -181,6 +199,7 @@ func (device *Device) ETHSign(
 				Value:               value.Bytes(),
 				Data:                data,
 				HostNonceCommitment: hostNonceCommitment,
+				AddressCase:         recipientAddressCase,
 			},
 		},
 	}
@@ -213,7 +232,8 @@ func (device *Device) ETHSignEIP1559(
 	gasLimit uint64,
 	recipient [20]byte,
 	value *big.Int,
-	data []byte) ([]byte, error) {
+	data []byte,
+	recipientAddressCase messages.ETHAddressCase) ([]byte, error) {
 
 	if !device.version.AtLeast(semver.NewSemVer(9, 16, 0)) {
 		return nil, UnsupportedError("9.16.0")
@@ -237,6 +257,7 @@ func (device *Device) ETHSignEIP1559(
 				Value:                value.Bytes(),
 				Data:                 data,
 				HostNonceCommitment:  hostNonceCommitment,
+				AddressCase:          recipientAddressCase,
 			},
 		},
 	}