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// Copyright 2019 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 aead
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"
kmsepb "github.com/tink-crypto/tink-go/v2/proto/kms_envelope_go_proto"
tinkpb "github.com/tink-crypto/tink-go/v2/proto/tink_go_proto"
)
const (
kmsEnvelopeAEADKeyVersion = 0
kmsEnvelopeAEADTypeURL = "type.googleapis.com/google.crypto.tink.KmsEnvelopeAeadKey"
)
// kmsEnvelopeAEADKeyManager is an implementation of KeyManager interface.
// It generates new KMSEnvelopeAEADKey keys and produces new instances of KMSEnvelopeAEAD subtle.
type kmsEnvelopeAEADKeyManager struct{}
// Primitive creates an KMSEnvelopeAEAD subtle for the given serialized KMSEnvelopeAEADKey proto.
func (km *kmsEnvelopeAEADKeyManager) Primitive(serializedKey []byte) (any, error) {
if len(serializedKey) == 0 {
return nil, errors.New("kms_envelope_aead_key_manager: invalid key")
}
key := new(kmsepb.KmsEnvelopeAeadKey)
if err := proto.Unmarshal(serializedKey, key); err != nil {
return nil, errors.New("kms_envelope_aead_key_manager: invalid key")
}
if err := km.validateKey(key); err != nil {
return nil, fmt.Errorf("kms_envelope_aead_key_manager: %v", err)
}
uri := key.GetParams().GetKekUri()
kmsClient, err := registry.GetKMSClient(uri)
if err != nil {
return nil, err
}
backend, err := kmsClient.GetAEAD(uri)
if err != nil {
return nil, errors.New("kms_envelope_aead_key_manager: invalid aead backend")
}
return NewKMSEnvelopeAEAD2(key.GetParams().GetDekTemplate(), backend), nil
}
// NewKey creates a new key according to specification the given serialized KMSEnvelopeAEADKeyFormat.
func (km *kmsEnvelopeAEADKeyManager) NewKey(serializedKeyFormat []byte) (proto.Message, error) {
if len(serializedKeyFormat) == 0 {
return nil, errors.New("kms_envelope_aead_key_manager: invalid key format")
}
keyFormat := new(kmsepb.KmsEnvelopeAeadKeyFormat)
if err := proto.Unmarshal(serializedKeyFormat, keyFormat); err != nil {
return nil, errors.New("kms_envelope_aead_key_manager: invalid key format")
}
if err := km.validateKeyFormat(keyFormat); err != nil {
return nil, fmt.Errorf("kms_envelope_aead_key_manager: %v", err)
}
return &kmsepb.KmsEnvelopeAeadKey{
Version: kmsEnvelopeAEADKeyVersion,
Params: keyFormat,
}, nil
}
// NewKeyData creates a new KeyData according to specification in the given serialized
// KMSEnvelopeAEADKeyFormat.
// It should be used solely by the key management API.
func (km *kmsEnvelopeAEADKeyManager) 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, err
}
return &tinkpb.KeyData{
TypeUrl: kmsEnvelopeAEADTypeURL,
Value: serializedKey,
KeyMaterialType: tinkpb.KeyData_REMOTE,
}, nil
}
// DoesSupport indicates if this key manager supports the given key type.
func (km *kmsEnvelopeAEADKeyManager) DoesSupport(typeURL string) bool {
return typeURL == kmsEnvelopeAEADTypeURL
}
// TypeURL returns the key type of keys managed by this key manager.
func (km *kmsEnvelopeAEADKeyManager) TypeURL() string {
return kmsEnvelopeAEADTypeURL
}
// validateKey validates the given KmsEnvelopeAeadKey.
func (km *kmsEnvelopeAEADKeyManager) validateKey(key *kmsepb.KmsEnvelopeAeadKey) error {
if err := keyset.ValidateKeyVersion(key.Version, kmsEnvelopeAEADKeyVersion); err != nil {
return err
}
if err := km.validateKeyFormat(key.GetParams()); err != nil {
return err
}
return nil
}
func (km *kmsEnvelopeAEADKeyManager) validateKeyFormat(keyFormat *kmsepb.KmsEnvelopeAeadKeyFormat) error {
dekKeyType := keyFormat.GetDekTemplate().GetTypeUrl()
if !isSupporedKMSEnvelopeDEK(dekKeyType) {
return fmt.Errorf("unsupported DEK key type %s. Only Tink AEAD key types are supported with KMSEnvelopeAEAD", dekKeyType)
}
return nil
}
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