Claim pegin (#165)

* added factory method FromPublicKeys for creating multiscript payment

* merkle tree v1-unstable

* invalid peg-in tx, wip

* refactor after review

* first working claim-pegin version

* skipping test since it requires nigiri

* comments, test fix

* removing todos

Makefile

@@ -5,4 +5,5 @@ help:
 
 test: 
 	export API_URL=http://localhost:3001; \
+	export API_BTC_URL=http://localhost:3000; \
 	go test -count=1 -v ./... 

block/merkle_block.go

@@ -0,0 +1,247 @@
+package block
+
+import (
+	"bytes"
+	"encoding/hex"
+	"errors"
+
+	"github.com/btcsuite/btcd/wire"
+
+	"github.com/btcsuite/btcd/blockchain"
+
+	"github.com/btcsuite/btcd/chaincfg/chainhash"
+)
+
+const (
+	// The maximum allowed weight for a block, see BIP 141 (network rule)
+	maxBlockWeight       = 4000000
+	witnessScaleFactor   = 4
+	minTransactionWeight = witnessScaleFactor * 60 // 60 is the lower bound for the size of a valid serialized tx
+
+)
+
+type MerkleBlock struct {
+	BlockHeader       *wire.BlockHeader
+	PartialMerkleTree *PartialMerkleTree
+}
+
+type PartialMerkleTree struct {
+	TxTotalCount uint32
+	TxHashes     [][]byte
+	FBad         bool
+	VBits        []bool
+}
+
+func NewMerkleBlockFromBuffer(buf *bytes.Buffer) (*MerkleBlock, error) {
+	return deserializeMerkleBlock(buf)
+}
+
+func NewMerkleBlockFromHex(h string) (*MerkleBlock, error) {
+	hexBytes, err := hex.DecodeString(h)
+	if err != nil {
+		return nil, err
+	}
+	buf := bytes.NewBuffer(hexBytes)
+	return NewMerkleBlockFromBuffer(buf)
+}
+
+func (m *MerkleBlock) ExtractMatches() (*chainhash.Hash, []chainhash.Hash, error) {
+	vMatch := make([]chainhash.Hash, 0)
+
+	if m.PartialMerkleTree.TxTotalCount == 0 {
+		return nil, nil, errors.New("tx count equal 0")
+	}
+
+	if m.PartialMerkleTree.TxTotalCount > maxBlockWeight/minTransactionWeight {
+		return nil, nil, errors.New("invalid tx count")
+	}
+	if len(m.PartialMerkleTree.TxHashes) > int(m.PartialMerkleTree.TxTotalCount) {
+		return nil, nil, errors.New(
+			"there can never be more hashes provided than one for every txid",
+		)
+	}
+
+	if len(m.PartialMerkleTree.VBits) < len(m.PartialMerkleTree.TxHashes) {
+		return nil, nil, errors.New(
+			"there must be at least one bit per node in the partial tree, " +
+				"and at least one node per hash",
+		)
+	}
+
+	// Calculate the number of merkle branches (height) in the tree.
+	height := uint32(0)
+	for m.calcTreeWidth(height) > 1 {
+		height++
+	}
+
+	var bitsUsed, hashUsed, position = 0, 0, 0
+	hashMerkleRoot, err := m.traverseAndExtract(
+		height,
+		position,
+		&bitsUsed,
+		&hashUsed,
+		&vMatch,
+	)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	if m.PartialMerkleTree.FBad {
+		return nil, nil, errors.New(
+			"there must be at least one bit per node in the partial tree, " +
+				"and at least one node per hash",
+		)
+	}
+	// verify that all bits were consumed (except for the padding caused by serializing it as a byte sequence)
+	if (bitsUsed+7)/8 != (len(m.PartialMerkleTree.VBits)+7)/8 {
+		return nil, nil, errors.New(
+			"except for the padding caused by serializing it as a byte" +
+				" sequence, not all bits were consumed",
+		)
+	}
+	// verify that all hashes were consumed
+	if hashUsed != len(m.PartialMerkleTree.TxHashes) {
+		return nil, nil, errors.New("not all hashes were consumed")
+	}
+
+	return hashMerkleRoot, vMatch, nil
+}
+
+func (m *MerkleBlock) traverseAndExtract(
+	height uint32,
+	position int,
+	bitsUsed *int,
+	hashUsed *int,
+	vMatch *[]chainhash.Hash,
+) (*chainhash.Hash, error) {
+	if *bitsUsed >= len(m.PartialMerkleTree.VBits) {
+		m.PartialMerkleTree.FBad = true
+		return nil, errors.New("overflowed the bits array")
+	}
+
+	fParentOfMatch := m.PartialMerkleTree.VBits[*bitsUsed]
+	*bitsUsed++
+	if height == 0 || !fParentOfMatch {
+		// if at height 0, or nothing interesting below, use stored hash and do not descend
+		if *hashUsed >= len(m.PartialMerkleTree.TxHashes) {
+			m.PartialMerkleTree.FBad = true
+			return nil, errors.New("overflowed the hash array")
+		}
+		hash, err := chainhash.NewHash(m.PartialMerkleTree.TxHashes[*hashUsed])
+		if err != nil {
+			return nil, err
+		}
+
+		*hashUsed++
+		if height == 0 && fParentOfMatch { // in case of height 0, we have a matched txid
+			*vMatch = append(*vMatch, *hash)
+		}
+
+		return hash, nil
+	} else {
+		//otherwise, descend into the subtrees to extract matched txids and hashes
+		left, err := m.traverseAndExtract(
+			height-1,
+			position*2,
+			bitsUsed,
+			hashUsed,
+			vMatch,
+		)
+		if err != nil {
+			return nil, err
+		}
+		var right *chainhash.Hash
+		if position*2+1 < int(m.calcTreeWidth(height-1)) {
+			right, err = m.traverseAndExtract(
+				height-1,
+				position*2+1,
+				bitsUsed,
+				hashUsed,
+				vMatch,
+			)
+			if err != nil {
+				return nil, err
+			}
+			if left.IsEqual(right) {
+				// The left and right branches should never be identical, as the transaction
+				// hashes covered by them must each be unique.
+				m.PartialMerkleTree.FBad = true
+			}
+		} else {
+			right = left
+		}
+
+		return blockchain.HashMerkleBranches(left, right), nil
+	}
+}
+
+// calcTreeWidth calculates and returns the the number of nodes (width) or a
+// merkle tree at the given depth-first height.
+func (m *MerkleBlock) calcTreeWidth(height uint32) uint32 {
+	return (m.PartialMerkleTree.TxTotalCount + (1 << height) - 1) >> height
+}
+
+func deserializePartialMerkleTree(
+	mb wire.MsgMerkleBlock,
+) (*PartialMerkleTree, error) {
+	txHashes := make([][]byte, 0, len(mb.Hashes))
+	for _, v := range mb.Hashes {
+
+		txHashes = append(txHashes, v.CloneBytes())
+	}
+
+	return &PartialMerkleTree{
+		TxTotalCount: mb.Transactions,
+		TxHashes:     txHashes,
+		FBad:         false,
+		VBits:        serializeVBits(mb.Flags),
+	}, nil
+}
+
+func deserializeMerkleBlock(buf *bytes.Buffer) (*MerkleBlock, error) {
+	mb := wire.MsgMerkleBlock{}
+	err := mb.BtcDecode(buf, wire.ProtocolVersion, wire.LatestEncoding)
+	if err != nil {
+		return nil, err
+	}
+
+	partialMerkleTree, err := deserializePartialMerkleTree(mb)
+	if err != nil {
+		return nil, err
+	}
+
+	return &MerkleBlock{
+		BlockHeader:       &mb.Header,
+		PartialMerkleTree: partialMerkleTree,
+	}, nil
+}
+
+func serializeVBits(b []byte) []bool {
+	bits := make([]bool, 0)
+
+	for _, v := range b {
+		l := byteToBits(v)
+		for _, v := range l {
+			if v == 1 {
+				bits = append(bits, true)
+			} else {
+				bits = append(bits, false)
+			}
+		}
+	}
+
+	return bits
+}
+
+func byteToBits(b byte) []byte {
+	return []byte{
+		(b >> 0) & 0x1,
+		(b >> 1) & 0x1,
+		(b >> 2) & 0x1,
+		(b >> 3) & 0x1,
+		(b >> 4) & 0x1,
+		(b >> 5) & 0x1,
+		(b >> 6) & 0x1,
+		(b >> 7) & 0x1,
+	}
+}

block/merkle_block_test.go

@@ -0,0 +1,44 @@
+package block
+
+import (
+	"encoding/hex"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+
+	"github.com/vulpemventures/go-elements/elementsutil"
+)
+
+func TestDeserializeMerkleBlock(t *testing.T) {
+	txOutProof := "0000003095a03ddcb18a359a1d41072ed373d45e57200f57d6f318238a7a6eb18df4c02dd4187f08f314f8436ac76f38cbe03a791a0893f26444ea5d5ec8f5b9b95a93015280ab60ffff7f20010000000200000002bdde18f707d02aa18ba82926965dc8bb8991d9510cd98e2812cc44b7aae8d3959745d887c8459cd4441f1dfe1a2d7ecbe225db87eeaa68bb22df6fdbf7017c480105"
+
+	merkleBlock, err := NewMerkleBlockFromHex(txOutProof)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	for _, v := range merkleBlock.PartialMerkleTree.TxHashes {
+		t.Log(hex.EncodeToString(elementsutil.ReverseBytes(v)))
+	}
+}
+
+func TestExtractMatches(t *testing.T) {
+	txOutProof := "0000003095a03ddcb18a359a1d41072ed373d45e57200f57d6f318238a7a6eb18df4c02dd4187f08f314f8436ac76f38cbe03a791a0893f26444ea5d5ec8f5b9b95a93015280ab60ffff7f20010000000200000002bdde18f707d02aa18ba82926965dc8bb8991d9510cd98e2812cc44b7aae8d3959745d887c8459cd4441f1dfe1a2d7ecbe225db87eeaa68bb22df6fdbf7017c480105"
+
+	merkleBlock, err := NewMerkleBlockFromHex(txOutProof)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	hashMerkleRoot, matchedHashes, err := merkleBlock.ExtractMatches()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	assert.Equal(
+		t,
+		true,
+		merkleBlock.BlockHeader.MerkleRoot.IsEqual(hashMerkleRoot),
+	)
+	assert.Equal(t, 1, len(matchedHashes))
+}

go.mod

@@ -8,6 +8,6 @@ require (
 	github.com/btcsuite/btcutil/psbt v1.0.2
 	github.com/stretchr/testify v1.7.0
 	github.com/vulpemventures/fastsha256 v0.0.0-20160815193821-637e65642941
-	github.com/vulpemventures/go-secp256k1-zkp v1.1.1-0.20210422114014-d9d676d706c1
+	github.com/vulpemventures/go-secp256k1-zkp v1.1.2
 	golang.org/x/crypto v0.0.0-20201221181555-eec23a3978ad
 )

go.sum

@@ -302,6 +302,8 @@ github.com/vulpemventures/go-secp256k1-zkp v1.1.0 h1:Z3qKc/lYxEQ1cukwwjD4n7EBCrg
 github.com/vulpemventures/go-secp256k1-zkp v1.1.0/go.mod h1:zo7CpgkuPgoe7fAV+inyxsI9IhGmcoFgyD8nqZaPSOM=
 github.com/vulpemventures/go-secp256k1-zkp v1.1.1-0.20210422114014-d9d676d706c1 h1:9rPKzVfNwHve4TkCtcECzT1/zTCuN90K08VXjaI0bb0=
 github.com/vulpemventures/go-secp256k1-zkp v1.1.1-0.20210422114014-d9d676d706c1/go.mod h1:zo7CpgkuPgoe7fAV+inyxsI9IhGmcoFgyD8nqZaPSOM=
+github.com/vulpemventures/go-secp256k1-zkp v1.1.2 h1:ZfM0r4QtkpQbNywlT9LFXXZBuMQ1Q8QiHGUTz4QV88M=
+github.com/vulpemventures/go-secp256k1-zkp v1.1.2/go.mod h1:zo7CpgkuPgoe7fAV+inyxsI9IhGmcoFgyD8nqZaPSOM=
 github.com/xiang90/probing v0.0.0-20190116061207-43a291ad63a2/go.mod h1:UETIi67q53MR2AWcXfiuqkDkRtnGDLqkBTpCHuJHxtU=
 go.etcd.io/bbolt v1.3.3/go.mod h1:IbVyRI1SCnLcuJnV2u8VeU0CEYM7e686BmAb1XKL+uU=
 go.etcd.io/etcd v0.0.0-20191023171146-3cf2f69b5738/go.mod h1:dnLIgRNXwCJa5e+c6mIZCrds/GIG4ncV9HhK5PX7jPg=