improve ibc transfer script building and parsing

Author: keithsue

x/btcbridge/types/ibc.go

@@ -1,8 +1,16 @@
 package types
 
 import (
+	"encoding/binary"
+	"fmt"
+	"strconv"
+	"strings"
+
 	"github.com/btcsuite/btcd/txscript"
 	"github.com/btcsuite/btcd/wire"
+
+	errorsmod "cosmossdk.io/errors"
+	channeltypes "github.com/cosmos/ibc-go/v8/modules/core/04-channel/types"
 )
 
 const (
@@ -21,22 +29,29 @@ const (
 
 // BuildIBCTransferScript builds the script for IBC transfer with the given channel and recipient address
 func BuildIBCTransferScript(channelId string, recipient string) ([]byte, error) {
+	// unprefix channel id
+	unprefixedChannelId, err := GetUnprefixedChannelId(channelId)
+	if err != nil {
+		return nil, err
+	}
+
+	// build OP_RETURN script
 	scriptBuilder := txscript.NewScriptBuilder()
 	scriptBuilder.AddOp(txscript.OP_RETURN)
 
 	// add magic number
 	scriptBuilder.AddOp(IBCTransferMagicNumber)
 
 	// add payload
-	scriptBuilder.AddData([]byte(channelId)).AddData([]byte(recipient))
+	scriptBuilder.AddData(unprefixedChannelId).AddData([]byte(recipient))
 
 	return scriptBuilder.Script()
 }
 
 // GetIBCTransferScript gets the IBC transfer script from the given deposit tx
 func GetIBCTransferScript(depositTx *wire.MsgTx) []byte {
 	for _, out := range depositTx.TxOut {
-		if IsOpReturnOutput(out) && out.PkScript[1] == IBCTransferMagicNumber {
+		if IsOpReturnOutput(out) && len(out.PkScript) > 1 && out.PkScript[1] == IBCTransferMagicNumber {
 			return out.PkScript
 		}
 	}
@@ -48,21 +63,25 @@ func GetIBCTransferScript(depositTx *wire.MsgTx) []byte {
 func ParseIBCTransferScript(script []byte) (channelId string, recipient string, err error) {
 	tokenizer := txscript.MakeScriptTokenizer(0, script)
 	if !tokenizer.Next() || tokenizer.Err() != nil || tokenizer.Opcode() != txscript.OP_RETURN {
-		return "", "", ErrInvalidIBCTransferScript
+		return "", "", errorsmod.Wrap(ErrInvalidIBCTransferScript, "non OP_RETURN script")
 	}
 
 	if !tokenizer.Next() || tokenizer.Err() != nil || tokenizer.Opcode() != IBCTransferMagicNumber {
-		return "", "", ErrInvalidIBCTransferScript
+		return "", "", errorsmod.Wrap(ErrInvalidIBCTransferScript, "failed to parse magic number")
 	}
 
 	if !tokenizer.Next() || tokenizer.Err() != nil {
-		return "", "", ErrInvalidIBCTransferScript
+		return "", "", errorsmod.Wrap(ErrInvalidIBCTransferScript, "failed to parse channel id")
+	}
+
+	if len(tokenizer.Data()) != 4 {
+		return "", "", errorsmod.Wrap(ErrInvalidIBCTransferScript, "invalid channel id")
 	}
 
-	channelId = string(tokenizer.Data())
+	channelId = NormalizeChannelId(tokenizer.Data())
 
 	if !tokenizer.Next() || tokenizer.Err() != nil {
-		return "", "", ErrInvalidIBCTransferScript
+		return "", "", errorsmod.Wrap(ErrInvalidIBCTransferScript, "failed to parse recipient address")
 	}
 
 	recipient = string(tokenizer.Data())
@@ -73,3 +92,30 @@ func ParseIBCTransferScript(script []byte) (channelId string, recipient string,
 
 	return
 }
+
+// GetUnprefixedChannelId gets the channel id without prefix
+func GetUnprefixedChannelId(channelId string) ([]byte, error) {
+	unprefixedChannelId, found := strings.CutPrefix(channelId, channeltypes.ChannelPrefix)
+	if !found {
+		return nil, channeltypes.ErrInvalidChannelIdentifier
+	}
+
+	id, err := strconv.ParseUint(unprefixedChannelId, 10, 32)
+	if err != nil {
+		return nil, err
+	}
+
+	bz := make([]byte, 4)
+	binary.BigEndian.PutUint32(bz, uint32(id))
+
+	return bz, nil
+}
+
+// NormalizeChannelId normalizes the given channel id
+func NormalizeChannelId(unprefixedChannelId []byte) string {
+	if len(unprefixedChannelId) != 4 {
+		return ""
+	}
+
+	return fmt.Sprintf("%s%d", channeltypes.ChannelPrefix, binary.BigEndian.Uint32(unprefixedChannelId))
+}