api/firmware/btc: add support for OP_RETURN

Added in v9.24.0

Author: benma

api/firmware/btc.go

@@ -18,6 +18,7 @@ import (
 	"encoding/binary"
 	"errors"
 	"fmt"
+	"slices"
 	"strings"
 
 	"github.com/BitBoxSwiss/bitbox02-api-go/api/firmware/messages"
@@ -372,6 +373,14 @@ func (device *Device) nonAtomicBTCSign(
 		}
 	}
 
+	if !device.version.AtLeast(semver.NewSemVer(9, 24, 0)) {
+		if slices.ContainsFunc(tx.Outputs, func(output *messages.BTCSignOutputRequest) bool {
+			return output.Type == messages.BTCOutputType_OP_RETURN
+		}) {
+			return nil, UnsupportedError("9.24.0")
+		}
+	}
+
 	supportsAntiklepto := device.version.AtLeast(semver.NewSemVer(9, 4, 0))
 
 	containsSilentPaymentOutputs := false

api/firmware/messages/btc.pb.go

@@ -175,6 +175,7 @@ enum BTCOutputType {
   P2WPKH = 3;
   P2WSH = 4;
   P2TR = 5;
+  OP_RETURN = 6;
 }
 
 message BTCSignOutputRequest {

api/firmware/messages/btc.proto

@@ -224,6 +224,21 @@ func payloadFromPkScript(pkScript []byte) (messages.BTCOutputType, []byte, error
 		outputType = messages.BTCOutputType_P2TR
 		payload = pkScript[2:]
 
+	case len(pkScript) > 0 && pkScript[0] == txscript.OP_RETURN:
+		outputType = messages.BTCOutputType_OP_RETURN
+
+		tokenizer := txscript.MakeScriptTokenizer(0, pkScript[1:])
+		if !tokenizer.Next() {
+			return 0, nil, errp.New("naked OP_RETURN is not supported")
+		}
+		payload = tokenizer.Data()
+		// OP_0 is an empty data push
+		if payload == nil && tokenizer.Opcode() != txscript.OP_0 {
+			return 0, nil, errp.New("no data push found after OP_RETURN")
+		}
+		if !tokenizer.Done() {
+			return 0, nil, errp.New("only one data push supported after OP_RETURN")
+		}
 	default:
 		return 0, nil, errp.New("unrecognized output type")
 	}

api/firmware/psbt.go

@@ -84,6 +84,7 @@ func TestPayloadFromPkScript(t *testing.T) {
 	tests := []struct {
 		name            string
 		address         string
+		pkScriptHex     string // Used for OP_RETURN instead of address
 		expectedType    messages.BTCOutputType
 		expectedPayload string
 	}{
@@ -117,18 +118,41 @@ func TestPayloadFromPkScript(t *testing.T) {
 			expectedPayload: "a60869f0dbcf1dc659c9cecbaf8050135ea9e8cdc487053f1dc6880949dc684c",
 			expectedType:    messages.BTCOutputType_P2TR,
 		},
+		{
+			name:            "OP_RETURN empty",
+			pkScriptHex:     "6a00",
+			expectedType:    messages.BTCOutputType_OP_RETURN,
+			expectedPayload: "",
+		},
+		{
+			name:            "OP_RETURN 3 bytes",
+			pkScriptHex:     "6a03aabbcc",
+			expectedType:    messages.BTCOutputType_OP_RETURN,
+			expectedPayload: "aabbcc",
+		},
+		{
+			name:            "OP_RETURN 80 bytes (OP_PUSHDATA1)",
+			pkScriptHex:     "6a4c50aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
+			expectedType:    messages.BTCOutputType_OP_RETURN,
+			expectedPayload: "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
+		},
 	}
 
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
-			addr, err := btcutil.DecodeAddress(tt.address, &chaincfg.MainNetParams)
-			require.NoError(t, err)
+			var pkScript []byte
+			var err error
 
-			pkScript, err := txscript.PayToAddrScript(addr)
-			require.NoError(t, err)
+			if tt.pkScriptHex != "" {
+				pkScript = unhex(tt.pkScriptHex)
+			} else {
+				addr, err := btcutil.DecodeAddress(tt.address, &chaincfg.MainNetParams)
+				require.NoError(t, err)
+				pkScript, err = txscript.PayToAddrScript(addr)
+				require.NoError(t, err)
+			}
 
 			outputType, payload, err := payloadFromPkScript(pkScript)
-
 			require.NoError(t, err)
 			assert.Equal(t, tt.expectedType, outputType)
 			assert.Equal(t, tt.expectedPayload, hex.EncodeToString(payload))