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// Copyright 2018 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package ecdsa
import (
"crypto/ecdsa"
"crypto/rand"
"errors"
"fmt"
"google.golang.org/protobuf/proto"
"github.com/tink-crypto/tink-go/v2/internal/internalapi"
"github.com/tink-crypto/tink-go/v2/internal/protoserialization"
"github.com/tink-crypto/tink-go/v2/keyset"
subtleSignature "github.com/tink-crypto/tink-go/v2/signature/subtle"
"github.com/tink-crypto/tink-go/v2/subtle"
commonpb "github.com/tink-crypto/tink-go/v2/proto/common_go_proto"
ecdsapb "github.com/tink-crypto/tink-go/v2/proto/ecdsa_go_proto"
tinkpb "github.com/tink-crypto/tink-go/v2/proto/tink_go_proto"
)
const (
signerKeyVersion = 0
signerTypeURL = "type.googleapis.com/google.crypto.tink.EcdsaPrivateKey"
)
// common errors
var errInvalidSignKey = errors.New("ecdsa_signer_key_manager: invalid key")
var errInvalidSignKeyFormat = errors.New("ecdsa_signer_key_manager: invalid key format")
// signerKeyManager is an implementation of KeyManager interface.
// It generates new ECDSA private keys and produces new instances of
// [subtleSignature.ECDSASigner].
type signerKeyManager struct{}
// Primitive creates an [subtleSignature.ECDSASigner] for the given serialized
// [ecdsapb.EcdsaPrivateKey] proto.
func (km *signerKeyManager) Primitive(serializedKey []byte) (any, error) {
keySerialization, err := protoserialization.NewKeySerialization(&tinkpb.KeyData{
TypeUrl: signerTypeURL,
Value: serializedKey,
KeyMaterialType: tinkpb.KeyData_ASYMMETRIC_PRIVATE,
}, tinkpb.OutputPrefixType_RAW, 0)
if err != nil {
return nil, err
}
key, err := protoserialization.ParseKey(keySerialization)
if err != nil {
return nil, err
}
signerKey, ok := key.(*PrivateKey)
if !ok {
return nil, fmt.Errorf("ecdsa_signer_key_manager: invalid key type: got %T, want %T", key, (*PrivateKey)(nil))
}
return NewSigner(signerKey, internalapi.Token{})
}
// NewKey creates a new [ecdsapb.EcdsaPrivateKey] according to specification
// the given serialized [ecdsapb.EcdsaKeyFormat].
func (km *signerKeyManager) NewKey(serializedKeyFormat []byte) (proto.Message, error) {
if len(serializedKeyFormat) == 0 {
return nil, errInvalidSignKeyFormat
}
keyFormat := new(ecdsapb.EcdsaKeyFormat)
if err := proto.Unmarshal(serializedKeyFormat, keyFormat); err != nil {
return nil, fmt.Errorf("ecdsa_signer_key_manager: invalid proto: %s", err)
}
if err := km.validateKeyFormat(keyFormat); err != nil {
return nil, fmt.Errorf("ecdsa_signer_key_manager: invalid key format: %s", err)
}
// generate key
params := keyFormat.GetParams()
curve := commonpb.EllipticCurveType_name[int32(params.Curve)]
tmpKey, err := ecdsa.GenerateKey(subtle.GetCurve(curve), rand.Reader)
if err != nil {
return nil, fmt.Errorf("ecdsa_signer_key_manager: cannot generate ECDSA key: %s", err)
}
keyValue := tmpKey.D.Bytes()
priv := &ecdsapb.EcdsaPrivateKey{
Version: signerKeyVersion,
PublicKey: &ecdsapb.EcdsaPublicKey{
Version: signerKeyVersion,
Params: params,
X: tmpKey.X.Bytes(),
Y: tmpKey.Y.Bytes(),
},
KeyValue: keyValue,
}
return priv, nil
}
// NewKeyData creates a new [tinkpb.KeyData] according to specification in then
// give serialized [ecdsapb.EcdsaKeyFormat]. It should be used solely by the
// key management API.
func (km *signerKeyManager) NewKeyData(serializedKeyFormat []byte) (*tinkpb.KeyData, error) {
key, err := km.NewKey(serializedKeyFormat)
if err != nil {
return nil, err
}
serializedKey, err := proto.Marshal(key)
if err != nil {
return nil, errInvalidSignKeyFormat
}
return &tinkpb.KeyData{
TypeUrl: signerTypeURL,
Value: serializedKey,
KeyMaterialType: tinkpb.KeyData_ASYMMETRIC_PRIVATE,
}, nil
}
// PublicKeyData extracts the public key as [tinkpb.KeyData] from the private
// key.
func (km *signerKeyManager) PublicKeyData(serializedPrivKey []byte) (*tinkpb.KeyData, error) {
privKey := new(ecdsapb.EcdsaPrivateKey)
if err := proto.Unmarshal(serializedPrivKey, privKey); err != nil {
return nil, errInvalidSignKey
}
if err := km.validateKey(privKey); err != nil {
return nil, err
}
serializedPubKey, err := proto.Marshal(privKey.PublicKey)
if err != nil {
return nil, errInvalidSignKey
}
return &tinkpb.KeyData{
TypeUrl: verifierTypeURL,
Value: serializedPubKey,
KeyMaterialType: tinkpb.KeyData_ASYMMETRIC_PUBLIC,
}, nil
}
// DoesSupport indicates if this key manager supports the given key type.
func (km *signerKeyManager) DoesSupport(typeURL string) bool {
return typeURL == signerTypeURL
}
// TypeURL returns the key type of keys managed by this key manager.
func (km *signerKeyManager) TypeURL() string { return signerTypeURL }
// validateKey validates the given [ecdsapb.EcdsaPrivateKey].
func (km *signerKeyManager) validateKey(key *ecdsapb.EcdsaPrivateKey) error {
if err := keyset.ValidateKeyVersion(key.Version, signerKeyVersion); err != nil {
return fmt.Errorf("invalid key version in key: %s", err)
}
if err := keyset.ValidateKeyVersion(key.GetPublicKey().GetVersion(), signerKeyVersion); err != nil {
return fmt.Errorf("invalid public version in key: %s", err)
}
hash, curve, encoding := paramNames(key.GetPublicKey().GetParams())
return subtleSignature.ValidateECDSAParams(hash, curve, encoding)
}
// validateKeyFormat validates the given [ecdsapb.EcdsaKeyFormat].
func (km *signerKeyManager) validateKeyFormat(format *ecdsapb.EcdsaKeyFormat) error {
hash, curve, encoding := paramNames(format.GetParams())
return subtleSignature.ValidateECDSAParams(hash, curve, encoding)
}
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