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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 chacha20poly1305
import (
"fmt"
"golang.org/x/crypto/chacha20poly1305"
"google.golang.org/protobuf/proto"
"github.com/tink-crypto/tink-go/v2/internal/protoserialization"
"github.com/tink-crypto/tink-go/v2/keyset"
"github.com/tink-crypto/tink-go/v2/subtle/random"
cppb "github.com/tink-crypto/tink-go/v2/proto/chacha20_poly1305_go_proto"
tinkpb "github.com/tink-crypto/tink-go/v2/proto/tink_go_proto"
)
const (
keyVersion = 0
typeURL = "type.googleapis.com/google.crypto.tink.ChaCha20Poly1305Key"
)
// Common errors.
var (
errInvalidKey = fmt.Errorf("chacha20poly1305_key_manager: invalid key")
errInvalidKeyFormat = fmt.Errorf("chacha20poly1305_key_manager: invalid key format")
)
// keyManager is an implementation of KeyManager interface.
// It generates new ChaCha20Poly1305Key keys and produces new instances of ChaCha20Poly1305 subtle.
type keyManager struct{}
// Primitive creates an ChaCha20Poly1305 subtle for the given serialized ChaCha20Poly1305Key proto.
func (km *keyManager) Primitive(serializedKey []byte) (any, error) {
keySerialization, err := protoserialization.NewKeySerialization(&tinkpb.KeyData{
TypeUrl: typeURL,
Value: serializedKey,
KeyMaterialType: tinkpb.KeyData_SYMMETRIC,
}, tinkpb.OutputPrefixType_RAW, 0)
if err != nil {
return nil, err
}
key, err := protoserialization.ParseKey(keySerialization)
if err != nil {
return nil, err
}
chaCha20Poly1305Key, ok := key.(*Key)
if !ok {
return nil, fmt.Errorf("chacha20poly1305_key_manager: invalid key type: got %T, want %T", key, (*Key)(nil))
}
ret, err := newAEAD(chaCha20Poly1305Key)
if err != nil {
return nil, fmt.Errorf("chacha20poly1305_key_manager: %v", err)
}
return ret, nil
}
// NewKey creates a new key, ignoring the specification in the given serialized key format
// because the key size and other params are fixed.
func (km *keyManager) NewKey(serializedKeyFormat []byte) (proto.Message, error) {
return km.newChaCha20Poly1305Key(), nil
}
// NewKeyData creates a new KeyData ignoring the specification in the given serialized key format
// because the key size and other params are fixed.
// It should be used solely by the key management API.
func (km *keyManager) NewKeyData(serializedKeyFormat []byte) (*tinkpb.KeyData, error) {
key := km.newChaCha20Poly1305Key()
serializedKey, err := proto.Marshal(key)
if err != nil {
return nil, err
}
return &tinkpb.KeyData{
TypeUrl: typeURL,
Value: serializedKey,
KeyMaterialType: tinkpb.KeyData_SYMMETRIC,
}, nil
}
// DoesSupport indicates if this key manager supports the given key type.
func (km *keyManager) DoesSupport(typeURL string) bool { return km.TypeURL() == typeURL }
// TypeURL returns the key type of keys managed by this key manager.
func (km *keyManager) TypeURL() string { return typeURL }
func (km *keyManager) newChaCha20Poly1305Key() *cppb.ChaCha20Poly1305Key {
keyValue := random.GetRandomBytes(chacha20poly1305.KeySize)
return &cppb.ChaCha20Poly1305Key{
Version: keyVersion,
KeyValue: keyValue,
}
}
// validateKey validates the given ChaCha20Poly1305Key.
func (km *keyManager) validateKey(key *cppb.ChaCha20Poly1305Key) error {
err := keyset.ValidateKeyVersion(key.Version, keyVersion)
if err != nil {
return fmt.Errorf("chacha20poly1305_key_manager: %s", err)
}
keySize := uint32(len(key.KeyValue))
if keySize != chacha20poly1305.KeySize {
return fmt.Errorf("chacha20poly1305_key_manager: keySize != %d", chacha20poly1305.KeySize)
}
return nil
}
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