frostfs-sdk-go/util/signature/options.go

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package signature
import (
"crypto/ecdsa"
"crypto/elliptic"
"crypto/rand"
"crypto/sha256"
"crypto/sha512"
"fmt"
"math/big"
"github.com/nspcc-dev/neo-go/pkg/crypto/keys"
"github.com/nspcc-dev/neofs-sdk-go/signature"
)
var curve = elliptic.P256()
type cfg struct {
schemeFixed bool
scheme signature.Scheme
}
func getConfig(opts ...SignOption) *cfg {
cfg := &cfg{
scheme: signature.ECDSAWithSHA512,
}
for i := range opts {
opts[i](cfg)
}
return cfg
}
func sign(scheme signature.Scheme, key *ecdsa.PrivateKey, msg []byte) ([]byte, error) {
switch scheme {
case signature.ECDSAWithSHA512:
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
case signature.RFC6979WithSHA256:
p := &keys.PrivateKey{PrivateKey: *key}
return p.Sign(msg), nil
default:
panic(fmt.Sprintf("unsupported scheme %s", scheme))
}
}
func verify(cfg *cfg, msg []byte, f func() (key, sign []byte, scheme signature.Scheme)) error {
key, sign, scheme := f()
pub, err := keys.NewPublicKeyFromBytes(key, elliptic.P256())
if err != nil {
return fmt.Errorf("%w: %v", ErrInvalidPublicKey, err)
}
if !cfg.schemeFixed {
cfg.scheme = scheme
}
switch cfg.scheme {
case signature.ECDSAWithSHA512:
h := sha512.Sum512(msg)
r, s := unmarshalXY(sign)
if r != nil && s != nil && ecdsa.Verify((*ecdsa.PublicKey)(pub), h[:], r, s) {
return nil
}
return ErrInvalidSignature
case signature.RFC6979WithSHA256:
h := sha256.Sum256(msg)
if pub.Verify(sign, h[:]) {
return nil
}
return ErrInvalidSignature
default:
return fmt.Errorf("unsupported signature scheme %s", cfg.scheme)
}
}
// 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.schemeFixed = true
c.scheme = signature.RFC6979WithSHA256
}
}