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aes_cmac_prf_key_manager.go
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aes_cmac_prf_key_manager.go
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// Copyright 2020 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 prf
import (
"errors"
"fmt"
"google.golang.org/protobuf/proto"
"github.com/tink-crypto/tink-go/v2/keyset"
"github.com/tink-crypto/tink-go/v2/prf/subtle"
"github.com/tink-crypto/tink-go/v2/subtle/random"
cmacpb "github.com/tink-crypto/tink-go/v2/proto/aes_cmac_prf_go_proto"
tinkpb "github.com/tink-crypto/tink-go/v2/proto/tink_go_proto"
)
const (
aescmacprfKeyVersion = 0
aescmacprfTypeURL = "type.googleapis.com/google.crypto.tink.AesCmacPrfKey"
)
var errInvalidAESCMACPRFKey = errors.New("aes_cmac_prf_key_manager: invalid key")
var errInvalidAESCMACPRFKeyFormat = errors.New("aes_cmac_prf_key_manager: invalid key format")
// aescmacprfKeyManager generates new AES-CMAC keys and produces new instances of AES-CMAC.
type aescmacprfKeyManager struct{}
// Primitive constructs a AES-CMAC instance for the given serialized AESCMACPRFKey.
func (km *aescmacprfKeyManager) Primitive(serializedKey []byte) (any, error) {
if len(serializedKey) == 0 {
return nil, errInvalidAESCMACPRFKey
}
key := new(cmacpb.AesCmacPrfKey)
if err := proto.Unmarshal(serializedKey, key); err != nil {
return nil, errInvalidAESCMACPRFKey
}
if err := km.validateKey(key); err != nil {
return nil, err
}
return subtle.NewAESCMACPRF(key.KeyValue)
}
// NewKey generates a new AESCMACPRFKey according to specification in the given AESCMACPRFKeyFormat.
func (km *aescmacprfKeyManager) NewKey(serializedKeyFormat []byte) (proto.Message, error) {
if len(serializedKeyFormat) == 0 {
return nil, errInvalidAESCMACPRFKeyFormat
}
keyFormat := new(cmacpb.AesCmacPrfKeyFormat)
if err := proto.Unmarshal(serializedKeyFormat, keyFormat); err != nil {
return nil, errInvalidAESCMACPRFKeyFormat
}
if err := km.validateKeyFormat(keyFormat); err != nil {
return nil, fmt.Errorf("aes_cmac_prf_key_manager: invalid key format: %s", err)
}
keyValue := random.GetRandomBytes(keyFormat.KeySize)
return &cmacpb.AesCmacPrfKey{
Version: aescmacprfKeyVersion,
KeyValue: keyValue,
}, nil
}
// NewKeyData generates a new KeyData according to specification in the given
// serialized AESCMACPRFKeyFormat. This should be used solely by the key management API.
func (km *aescmacprfKeyManager) 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, errInvalidAESCMACPRFKeyFormat
}
return &tinkpb.KeyData{
TypeUrl: aescmacprfTypeURL,
Value: serializedKey,
KeyMaterialType: tinkpb.KeyData_SYMMETRIC,
}, nil
}
// DoesSupport checks whether this KeyManager supports the given key type.
func (km *aescmacprfKeyManager) DoesSupport(typeURL string) bool {
return typeURL == aescmacprfTypeURL
}
// TypeURL returns the type URL of keys managed by this KeyManager.
func (km *aescmacprfKeyManager) TypeURL() string {
return aescmacprfTypeURL
}
// validateKey validates the given AESCMACPRFKey. It only validates the version of the
// key because other parameters will be validated in primitive construction.
func (km *aescmacprfKeyManager) validateKey(key *cmacpb.AesCmacPrfKey) error {
err := keyset.ValidateKeyVersion(key.Version, aescmacprfKeyVersion)
if err != nil {
return fmt.Errorf("aes_cmac_prf_key_manager: invalid version: %s", err)
}
keySize := uint32(len(key.KeyValue))
return subtle.ValidateAESCMACPRFParams(keySize)
}
// validateKeyFormat validates the given HMACKeyFormat
func (km *aescmacprfKeyManager) validateKeyFormat(format *cmacpb.AesCmacPrfKeyFormat) error {
return subtle.ValidateAESCMACPRFParams(format.KeySize)
}