[#53] util: move signature package from neofs-api-go

Signed-off-by: Evgenii Stratonikov <evgeniy@nspcc.ru>

util/signature/data.go

@@ -0,0 +1,120 @@
+package signature
+
+import (
+	"crypto/ecdsa"
+	"crypto/elliptic"
+	"errors"
+	"fmt"
+
+	"github.com/nspcc-dev/neo-go/pkg/crypto/keys"
+)
+
+type DataSource interface {
+	ReadSignedData([]byte) ([]byte, error)
+	SignedDataSize() int
+}
+
+type DataWithSignature interface {
+	DataSource
+	GetSignatureWithKey() (key, sig []byte)
+	SetSignatureWithKey(key, sig []byte)
+}
+
+type SignOption func(*cfg)
+
+type KeySignatureHandler func(key []byte, sig []byte)
+
+type KeySignatureSource func() (key, sig []byte)
+
+const (
+	// PrivateKeyCompressedSize is constant with compressed size of private key (SK).
+	// D coordinate stored, recover PK by formula x, y = curve.ScalarBaseMul(d,bytes).
+	PrivateKeyCompressedSize = 32
+
+	// PublicKeyCompressedSize is constant with compressed size of public key (PK).
+	PublicKeyCompressedSize = 33
+
+	// PublicKeyUncompressedSize is constant with uncompressed size of public key (PK).
+	// First byte always should be 0x4 other 64 bytes is X and Y (32 bytes per coordinate).
+	// 2 * 32 + 1.
+	PublicKeyUncompressedSize = 65
+)
+
+var (
+	// ErrEmptyPrivateKey is returned when used private key is empty.
+	ErrEmptyPrivateKey = errors.New("empty private key")
+	// ErrInvalidPublicKey is returned when public key cannot be unmarshalled.
+	ErrInvalidPublicKey = errors.New("invalid public key")
+	// ErrInvalidSignature is returned if signature cannot be verified.
+	ErrInvalidSignature = errors.New("invalid signature")
+)
+
+func DataSignature(key *ecdsa.PrivateKey, src DataSource, opts ...SignOption) ([]byte, error) {
+	if key == nil {
+		return nil, ErrEmptyPrivateKey
+	}
+
+	data, err := dataForSignature(src)
+	if err != nil {
+		return nil, err
+	}
+	defer bytesPool.Put(&data)
+
+	cfg := defaultCfg()
+
+	for i := range opts {
+		opts[i](cfg)
+	}
+
+	return cfg.signFunc(key, data)
+}
+
+func SignDataWithHandler(key *ecdsa.PrivateKey, src DataSource, handler KeySignatureHandler, opts ...SignOption) error {
+	sig, err := DataSignature(key, src, opts...)
+	if err != nil {
+		return err
+	}
+
+	pub := (*keys.PublicKey)(&key.PublicKey)
+	handler(pub.Bytes(), sig)
+
+	return nil
+}
+
+func VerifyDataWithSource(dataSrc DataSource, sigSrc KeySignatureSource, opts ...SignOption) error {
+	data, err := dataForSignature(dataSrc)
+	if err != nil {
+		return err
+	}
+	defer bytesPool.Put(&data)
+
+	cfg := defaultCfg()
+
+	for i := range opts {
+		opts[i](cfg)
+	}
+
+	key, sig := sigSrc()
+
+	var pub *keys.PublicKey
+	if len(key) != 0 {
+		pub, err = keys.NewPublicKeyFromBytes(key, elliptic.P256())
+		if err != nil {
+			return fmt.Errorf("%w: %v", ErrInvalidPublicKey, err)
+		}
+	}
+
+	return cfg.verifyFunc(
+		(*ecdsa.PublicKey)(pub),
+		data,
+		sig,
+	)
+}
+
+func SignData(key *ecdsa.PrivateKey, v DataWithSignature, opts ...SignOption) error {
+	return SignDataWithHandler(key, v, v.SetSignatureWithKey, opts...)
+}
+
+func VerifyData(src DataWithSignature, opts ...SignOption) error {
+	return VerifyDataWithSource(src, src.GetSignatureWithKey, opts...)
+}

util/signature/options.go

@@ -0,0 +1,91 @@
+package signature
+
+import (
+	"crypto/ecdsa"
+	"crypto/elliptic"
+	"crypto/rand"
+	"crypto/sha256"
+	"crypto/sha512"
+	"math/big"
+
+	"github.com/nspcc-dev/neo-go/pkg/crypto/keys"
+)
+
+var curve = elliptic.P256()
+
+type cfg struct {
+	signFunc   func(key *ecdsa.PrivateKey, msg []byte) ([]byte, error)
+	verifyFunc func(key *ecdsa.PublicKey, msg []byte, sig []byte) error
+}
+
+func defaultCfg() *cfg {
+	return &cfg{
+		signFunc:   sign,
+		verifyFunc: verify,
+	}
+}
+
+func sign(key *ecdsa.PrivateKey, msg []byte) ([]byte, error) {
+	h := sha512.Sum512(msg)
+	x, y, err := ecdsa.Sign(rand.Reader, key, h[:])
+	if err != nil {
+		return nil, err
+	}
+	return elliptic.Marshal(elliptic.P256(), x, y), nil
+}
+
+func verify(key *ecdsa.PublicKey, msg []byte, sig []byte) error {
+	h := sha512.Sum512(msg)
+	r, s := unmarshalXY(sig)
+	if r != nil && s != nil && ecdsa.Verify(key, h[:], r, s) {
+		return nil
+	}
+	return ErrInvalidSignature
+}
+
+// unmarshalXY converts a point, serialized by Marshal, into an x, y pair.
+// It is an error if the point is not in uncompressed form.
+// On error, x,y = nil.
+// Unlike the original version of the code, we ignore that x or y not on the curve
+// --------------
+// It's copy-paste elliptic.Unmarshal(curve, data) stdlib function, without last line
+// of code.
+// Link - https://golang.org/pkg/crypto/elliptic/#Unmarshal
+func unmarshalXY(data []byte) (x *big.Int, y *big.Int) {
+	if len(data) != PublicKeyUncompressedSize {
+		return
+	} else if data[0] != 4 { // uncompressed form
+		return
+	}
+
+	p := curve.Params().P
+	x = new(big.Int).SetBytes(data[1:PublicKeyCompressedSize])
+	y = new(big.Int).SetBytes(data[PublicKeyCompressedSize:])
+
+	if x.Cmp(p) >= 0 || y.Cmp(p) >= 0 {
+		x, y = nil, nil
+	}
+
+	return
+}
+
+func SignWithRFC6979() SignOption {
+	return func(c *cfg) {
+		c.signFunc = signRFC6979
+		c.verifyFunc = verifyRFC6979
+	}
+}
+
+func signRFC6979(key *ecdsa.PrivateKey, msg []byte) ([]byte, error) {
+	p := &keys.PrivateKey{PrivateKey: *key}
+	return p.Sign(msg), nil
+}
+
+func verifyRFC6979(key *ecdsa.PublicKey, msg []byte, sig []byte) error {
+	p := (*keys.PublicKey)(key)
+	h := sha256.Sum256(msg)
+	if p.Verify(sig, h[:]) {
+		return nil
+	}
+	return ErrInvalidSignature
+}

util/signature/util.go

@@ -0,0 +1,31 @@
+package signature
+
+import (
+	"errors"
+	"sync"
+)
+
+var bytesPool = sync.Pool{
+	New: func() interface{} {
+		b := make([]byte, 5<<20)
+		return &b
+	},
+}
+
+func dataForSignature(src DataSource) ([]byte, error) {
+	if src == nil {
+		return nil, errors.New("nil source")
+	}
+
+	buf := *bytesPool.Get().(*[]byte)
+
+	if size := src.SignedDataSize(); size < 0 {
+		return nil, errors.New("negative length")
+	} else if size <= cap(buf) {
+		buf = buf[:size]
+	} else {
+		buf = make([]byte, size)
+	}
+
+	return src.ReadSignedData(buf)
+}