| // 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 aead |
| |
| import ( |
| "fmt" |
| |
| "golang.org/x/crypto/chacha20poly1305" |
| "google.golang.org/protobuf/proto" |
| "github.com/google/tink/go/aead/subtle" |
| "github.com/google/tink/go/keyset" |
| "github.com/google/tink/go/subtle/random" |
| |
| cppb "github.com/google/tink/go/proto/chacha20_poly1305_go_proto" |
| tinkpb "github.com/google/tink/go/proto/tink_go_proto" |
| ) |
| |
| const ( |
| chaCha20Poly1305KeyVersion = 0 |
| chaCha20Poly1305TypeURL = "type.googleapis.com/google.crypto.tink.ChaCha20Poly1305Key" |
| ) |
| |
| // Common errors. |
| var errInvalidChaCha20Poly1305Key = fmt.Errorf("chacha20poly1305_key_manager: invalid key") |
| var errInvalidChaCha20Poly1305KeyFormat = fmt.Errorf("chacha20poly1305_key_manager: invalid key format") |
| |
| // chaCha20Poly1305KeyManager is an implementation of KeyManager interface. |
| // It generates new ChaCha20Poly1305Key keys and produces new instances of ChaCha20Poly1305 subtle. |
| type chaCha20Poly1305KeyManager struct{} |
| |
| // Primitive creates an ChaCha20Poly1305 subtle for the given serialized ChaCha20Poly1305Key proto. |
| func (km *chaCha20Poly1305KeyManager) Primitive(serializedKey []byte) (any, error) { |
| if len(serializedKey) == 0 { |
| return nil, errInvalidChaCha20Poly1305Key |
| } |
| key := new(cppb.ChaCha20Poly1305Key) |
| if err := proto.Unmarshal(serializedKey, key); err != nil { |
| return nil, errInvalidChaCha20Poly1305Key |
| } |
| if err := km.validateKey(key); err != nil { |
| return nil, err |
| } |
| ret, err := subtle.NewChaCha20Poly1305(key.KeyValue) |
| if err != nil { |
| return nil, fmt.Errorf("chacha20poly1305_key_manager: cannot create new primitive: %s", 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 *chaCha20Poly1305KeyManager) 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 *chaCha20Poly1305KeyManager) NewKeyData(serializedKeyFormat []byte) (*tinkpb.KeyData, error) { |
| key := km.newChaCha20Poly1305Key() |
| serializedKey, err := proto.Marshal(key) |
| if err != nil { |
| return nil, err |
| } |
| return &tinkpb.KeyData{ |
| TypeUrl: chaCha20Poly1305TypeURL, |
| Value: serializedKey, |
| KeyMaterialType: tinkpb.KeyData_SYMMETRIC, |
| }, nil |
| } |
| |
| // DoesSupport indicates if this key manager supports the given key type. |
| func (km *chaCha20Poly1305KeyManager) DoesSupport(typeURL string) bool { |
| return typeURL == chaCha20Poly1305TypeURL |
| } |
| |
| // TypeURL returns the key type of keys managed by this key manager. |
| func (km *chaCha20Poly1305KeyManager) TypeURL() string { |
| return chaCha20Poly1305TypeURL |
| } |
| |
| func (km *chaCha20Poly1305KeyManager) newChaCha20Poly1305Key() *cppb.ChaCha20Poly1305Key { |
| keyValue := random.GetRandomBytes(chacha20poly1305.KeySize) |
| return &cppb.ChaCha20Poly1305Key{ |
| Version: chaCha20Poly1305KeyVersion, |
| KeyValue: keyValue, |
| } |
| } |
| |
| // validateKey validates the given ChaCha20Poly1305Key. |
| func (km *chaCha20Poly1305KeyManager) validateKey(key *cppb.ChaCha20Poly1305Key) error { |
| err := keyset.ValidateKeyVersion(key.Version, chaCha20Poly1305KeyVersion) |
| 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 |
| } |