117 lines
2.8 KiB
Go
117 lines
2.8 KiB
Go
package signature
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import (
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"crypto/ecdsa"
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"crypto/elliptic"
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"crypto/rand"
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"crypto/sha256"
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"crypto/sha512"
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"fmt"
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"math/big"
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"github.com/nspcc-dev/neo-go/pkg/crypto/keys"
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"github.com/nspcc-dev/neofs-sdk-go/signature"
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)
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var curve = elliptic.P256()
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type cfg struct {
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defaultScheme signature.Scheme
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restrictScheme signature.Scheme
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}
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func getConfig(opts ...SignOption) *cfg {
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cfg := &cfg{
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defaultScheme: signature.ECDSAWithSHA512,
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restrictScheme: signature.Unspecified,
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}
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for i := range opts {
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opts[i](cfg)
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}
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return cfg
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}
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func sign(scheme signature.Scheme, key *ecdsa.PrivateKey, msg []byte) ([]byte, error) {
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switch scheme {
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case signature.ECDSAWithSHA512:
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h := sha512.Sum512(msg)
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x, y, err := ecdsa.Sign(rand.Reader, key, h[:])
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if err != nil {
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return nil, err
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}
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return elliptic.Marshal(elliptic.P256(), x, y), nil
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case signature.RFC6979WithSHA256:
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p := &keys.PrivateKey{PrivateKey: *key}
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return p.Sign(msg), nil
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default:
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panic("unsupported scheme")
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}
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}
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func verify(cfg *cfg, msg []byte, sig *signature.Signature) error {
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pub, err := keys.NewPublicKeyFromBytes(sig.Key(), elliptic.P256())
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if err != nil {
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return fmt.Errorf("%w: %v", ErrInvalidPublicKey, err)
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}
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scheme := sig.Scheme()
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if scheme == signature.Unspecified {
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scheme = cfg.defaultScheme
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}
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if cfg.restrictScheme != signature.Unspecified && scheme != cfg.restrictScheme {
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return fmt.Errorf("%w: unexpected signature scheme", ErrInvalidSignature)
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}
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switch scheme {
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case signature.ECDSAWithSHA512:
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h := sha512.Sum512(msg)
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r, s := unmarshalXY(sig.Sign())
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if r != nil && s != nil && ecdsa.Verify((*ecdsa.PublicKey)(pub), h[:], r, s) {
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return nil
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}
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return ErrInvalidSignature
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case signature.RFC6979WithSHA256:
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h := sha256.Sum256(msg)
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if pub.Verify(sig.Sign(), h[:]) {
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return nil
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}
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return ErrInvalidSignature
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default:
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return ErrInvalidSignature
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}
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}
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// unmarshalXY converts a point, serialized by Marshal, into an x, y pair.
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// It is an error if the point is not in uncompressed form.
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// On error, x,y = nil.
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// Unlike the original version of the code, we ignore that x or y not on the curve
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// --------------
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// It's copy-paste elliptic.Unmarshal(curve, data) stdlib function, without last line
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// of code.
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// Link - https://golang.org/pkg/crypto/elliptic/#Unmarshal
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func unmarshalXY(data []byte) (x *big.Int, y *big.Int) {
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if len(data) != PublicKeyUncompressedSize {
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return
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} else if data[0] != 4 { // uncompressed form
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return
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}
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p := curve.Params().P
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x = new(big.Int).SetBytes(data[1:PublicKeyCompressedSize])
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y = new(big.Int).SetBytes(data[PublicKeyCompressedSize:])
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if x.Cmp(p) >= 0 || y.Cmp(p) >= 0 {
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x, y = nil, nil
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}
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return
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}
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func SignWithRFC6979() SignOption {
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return func(c *cfg) {
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c.defaultScheme = signature.RFC6979WithSHA256
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c.restrictScheme = signature.RFC6979WithSHA256
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}
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}
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