lnwallet: import badge's script utils in new file

lnwallet/script_utils.go

@@ -0,0 +1,85 @@
+package lnwallet
+
+import (
+	"bytes"
+	"fmt"
+
+	"github.com/btcsuite/btcd/txscript"
+	"github.com/btcsuite/btcd/wire"
+	"github.com/btcsuite/btcutil"
+)
+
+// scriptHashPkScript...
+func scriptHashPkScript(scriptBytes []byte) ([]byte, error) {
+	bldr := txscript.NewScriptBuilder()
+	bldr.AddOp(txscript.OP_HASH160)
+	bldr.AddData(btcutil.Hash160(scriptBytes))
+	bldr.AddOp(txscript.OP_EQUAL)
+	return bldr.Script()
+}
+
+// getFundingPkScript generates the non-p2sh'd multisig script for 2 of 2
+// pubkeys.
+func genFundingPkScript(aPub, bPub []byte) ([]byte, error) {
+	if len(aPub) != 33 || len(bPub) != 33 {
+		return nil, fmt.Errorf("Pubkey size error. Compressed pubkeys only")
+	}
+
+	if bytes.Compare(aPub, bPub) == -1 { // swap to sort pubkeys if needed
+		aPub, bPub = bPub, aPub
+	}
+
+	bldr := txscript.NewScriptBuilder()
+	// Require 2 signatures, so from both of the pubkeys
+	bldr.AddOp(txscript.OP_2)
+	// add both pubkeys (sorted)
+	bldr.AddData(aPub)
+	bldr.AddData(bPub)
+	// 2 keys total.  In case that wasn't obvious.
+	bldr.AddOp(txscript.OP_2)
+	// Good ol OP_CHECKMULTISIG.  Don't forget the zero!
+	bldr.AddOp(txscript.OP_CHECKMULTISIG)
+	// get byte slice
+	return bldr.Script()
+}
+
+// fundMultiSigOut creates a TxOut for the funding transaction.
+// Give it the two pubkeys and it'll give you the p2sh'd txout.
+// You don't have to remember the p2sh preimage, as long as you remember the
+// pubkeys involved.
+func fundMultiSigOut(aPub, bPub []byte, amt int64) ([]byte, *wire.TxOut, error) {
+	if amt < 0 {
+		return nil, nil, fmt.Errorf("Can't create FundTx script with negative coins")
+	}
+
+	// p2shify
+	redeemScript, err := genFundingPkScript(aPub, bPub)
+	if err != nil {
+		return nil, nil, err
+	}
+	pkScript, err := scriptHashPkScript(redeemScript)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	return redeemScript, wire.NewTxOut(amt, pkScript), nil
+}
+
+// the scriptsig to put on a P2SH input
+func spendMultiSig(redeemScript, sigA, sigB []byte) ([]byte, error) {
+	bldr := txscript.NewScriptBuilder()
+
+	// add a 0 for some multisig fun
+	bldr.AddOp(txscript.OP_0)
+
+	// add sigA
+	bldr.AddData(sigA)
+	// add sigB
+	bldr.AddData(sigB)
+
+	// preimage goes on AT THE ENDDDD
+	bldr.AddData(redeemScript)
+
+	// that's all, get bytes
+	return bldr.Script()
+}