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// Copyright 2022 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 keyderivation
import (
"errors"
"fmt"
"google.golang.org/protobuf/proto"
"github.com/tink-crypto/tink-go/v2/core/registry"
"github.com/tink-crypto/tink-go/v2/keyset"
prfderpb "github.com/tink-crypto/tink-go/v2/proto/prf_based_deriver_go_proto"
tinkpb "github.com/tink-crypto/tink-go/v2/proto/tink_go_proto"
)
const (
prfBasedDeriverKeyVersion = 0
prfBasedDeriverTypeURL = "type.googleapis.com/google.crypto.tink.PrfBasedDeriverKey"
)
var (
errInvalidPRFBasedDeriverKey = errors.New("prf_based_deriver_key_manager: invalid key")
errInvalidPRFBasedDeriverKeyFormat = errors.New("prf_based_deriver_key_manager: invalid key format")
)
type prfBasedDeriverKeyManager struct{}
var _ registry.KeyManager = (*prfBasedDeriverKeyManager)(nil)
func (km *prfBasedDeriverKeyManager) Primitive(serializedKey []byte) (any, error) {
if len(serializedKey) == 0 {
return nil, errInvalidPRFBasedDeriverKey
}
key := &prfderpb.PrfBasedDeriverKey{}
if err := proto.Unmarshal(serializedKey, key); err != nil {
return nil, errInvalidPRFBasedDeriverKey
}
if keyset.ValidateKeyVersion(key.GetVersion(), prfBasedDeriverKeyVersion) != nil {
return nil, errInvalidPRFBasedDeriverKey
}
return newPRFBasedDeriver(key.GetPrfKey(), key.GetParams().GetDerivedKeyTemplate())
}
func (km *prfBasedDeriverKeyManager) NewKey(serializedKeyFormat []byte) (proto.Message, error) {
if len(serializedKeyFormat) == 0 {
return nil, errInvalidPRFBasedDeriverKeyFormat
}
keyFormat := &prfderpb.PrfBasedDeriverKeyFormat{}
if err := proto.Unmarshal(serializedKeyFormat, keyFormat); err != nil {
return nil, errInvalidPRFBasedDeriverKeyFormat
}
if keyFormat.GetParams() == nil {
return nil, errors.New("prf_based_deriver_key_manager: nil PRF-Based Deriver params")
}
prfKey, err := registry.NewKeyData(keyFormat.GetPrfKeyTemplate())
if err != nil {
return nil, errors.New("prf_based_deriver_key_manager: failed to generate key from PRF key template")
}
// Validate PRF key data and derived key template.
if _, err := newPRFBasedDeriver(prfKey, keyFormat.GetParams().GetDerivedKeyTemplate()); err != nil {
return nil, fmt.Errorf("prf_based_deriver_key_manager: %v", err)
}
return &prfderpb.PrfBasedDeriverKey{
Version: prfBasedDeriverKeyVersion,
PrfKey: prfKey,
Params: keyFormat.GetParams(),
}, nil
}
func (km *prfBasedDeriverKeyManager) 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, errInvalidPRFBasedDeriverKeyFormat
}
return &tinkpb.KeyData{
TypeUrl: prfBasedDeriverTypeURL,
Value: serializedKey,
KeyMaterialType: tinkpb.KeyData_SYMMETRIC,
}, nil
}
func (km *prfBasedDeriverKeyManager) DoesSupport(typeURL string) bool {
return typeURL == prfBasedDeriverTypeURL
}
func (km *prfBasedDeriverKeyManager) TypeURL() string {
return prfBasedDeriverTypeURL
}
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