Update project structure and build process

libwallet/hdprivatekey.go

@@ -0,0 +1,163 @@
+package libwallet
+
+import (
+	"crypto/sha256"
+	"errors"
+	"fmt"
+	"strings"
+
+	"github.com/muun/libwallet/hdpath"
+
+	"github.com/btcsuite/btcutil/hdkeychain"
+)
+
+// HDPrivateKey is an HD capable priv key
+type HDPrivateKey struct {
+	key     hdkeychain.ExtendedKey
+	Network *Network
+	Path    string
+}
+
+// NewHDPrivateKey builds an HD priv key from a seed for a given network
+func NewHDPrivateKey(seed []byte, network *Network) (*HDPrivateKey, error) {
+
+	key, err := hdkeychain.NewMaster(seed, network.network)
+	if err != nil {
+		return nil, err
+	}
+
+	return &HDPrivateKey{key: *key, Network: network, Path: "m"}, nil
+}
+
+// NewHDPrivateKeyFromBytes builds an HD priv key from the compress priv and chain code for a given network
+func NewHDPrivateKeyFromBytes(rawKey, chainCode []byte, network *Network) (*HDPrivateKey, error) {
+
+	parentFP := []byte{0, 0, 0, 0}
+	key := hdkeychain.NewExtendedKey(network.network.HDPrivateKeyID[:],
+		rawKey, chainCode, parentFP, 0, 0, true)
+
+	return &HDPrivateKey{key: *key, Network: network, Path: "m"}, nil
+}
+
+// NewHDPrivateKeyFromString creates an HD priv key from a base58-encoded string
+// If the parsed key is public, it returns an error
+func NewHDPrivateKeyFromString(str, path string, network *Network) (*HDPrivateKey, error) {
+
+	key, err := hdkeychain.NewKeyFromString(str)
+	if err != nil {
+		return nil, err
+	}
+
+	if !key.IsPrivate() {
+		return nil, errors.New("encoded key was not a private key")
+	}
+
+	return &HDPrivateKey{key: *key, Network: network, Path: path}, nil
+}
+
+// PublicKey returns the matching pub key
+func (p *HDPrivateKey) PublicKey() *HDPublicKey {
+
+	key, err := p.key.Neuter()
+	if err != nil {
+		panic("original key was invalid")
+	}
+
+	return &HDPublicKey{key: *key, Network: p.Network, Path: p.Path}
+}
+
+// String return the key base58-encoded
+func (p *HDPrivateKey) String() string {
+	return p.key.String()
+}
+
+// DerivedAt derives a new child priv key, which may be hardened
+// index should be uint32 but for java compat we use int64
+func (p *HDPrivateKey) DerivedAt(index int64, hardened bool) (*HDPrivateKey, error) {
+	var modifier uint32
+	if hardened {
+		modifier = hdkeychain.HardenedKeyStart
+	}
+
+	child, err := p.key.Child(uint32(index) | modifier)
+	if err != nil {
+		return nil, err
+	}
+
+	parentPath, err := hdpath.Parse(p.Path)
+	if err != nil {
+		return nil, err
+	}
+	path := parentPath.Child(uint32(index) | modifier)
+
+	return &HDPrivateKey{key: *child, Network: p.Network, Path: path.String()}, nil
+}
+
+func (p *HDPrivateKey) DeriveTo(path string) (*HDPrivateKey, error) {
+
+	if !strings.HasPrefix(path, p.Path) {
+		return nil, fmt.Errorf("derivation path %v is not prefix of the keys path %v", path, p.Path)
+	}
+
+	firstPath, err := hdpath.Parse(p.Path)
+	if err != nil {
+		return nil, fmt.Errorf("couldn't parse derivation path %v: %w", p.Path, err)
+	}
+
+	secondPath, err := hdpath.Parse(path)
+	if err != nil {
+		return nil, fmt.Errorf("couldn't parse derivation path %v: %w", path, err)
+	}
+
+	indexes := secondPath.IndexesFrom(firstPath)
+	derivedKey := p
+	for depth, index := range indexes {
+		derivedKey, err = derivedKey.DerivedAt(int64(index.Index), index.Hardened)
+		if err != nil {
+			return nil, fmt.Errorf("failed to derive key at path %v on depth %v: %w", path, depth, err)
+		}
+	}
+	// The generated path has no names in it, so replace it
+	derivedKey.Path = path
+
+	return derivedKey, nil
+}
+
+// Sign a payload using the backing EC key
+func (p *HDPrivateKey) Sign(data []byte) ([]byte, error) {
+
+	signingKey, err := p.key.ECPrivKey()
+	if err != nil {
+		return nil, err
+	}
+
+	hash := sha256.Sum256(data)
+	sig, err := signingKey.Sign(hash[:])
+	if err != nil {
+		return nil, err
+	}
+
+	return sig.Serialize(), nil
+}
+
+func (p *HDPrivateKey) Decrypter() Decrypter {
+	return &hdPrivKeyDecrypter{p, nil, true}
+}
+
+func (p *HDPrivateKey) DecrypterFrom(senderKey *PublicKey) Decrypter {
+	return &hdPrivKeyDecrypter{p, senderKey, false}
+}
+
+func (p *HDPrivateKey) Encrypter() Encrypter {
+	return &hdPubKeyEncrypter{p.PublicKey(), p}
+}
+
+func (p *HDPrivateKey) EncrypterTo(receiver *HDPublicKey) Encrypter {
+	return &hdPubKeyEncrypter{receiver, p}
+}
+
+// What follows is a workaround for https://github.com/golang/go/issues/46893
+
+func SignWithPrivateKey(key *HDPrivateKey, data []byte) ([]byte, error) {
+	return key.Sign(data)
+}