| // 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 daead |
| |
| import ( |
| "errors" |
| "fmt" |
| "io" |
| |
| "google.golang.org/protobuf/proto" |
| "github.com/google/tink/go/core/registry" |
| "github.com/google/tink/go/daead/subtle" |
| "github.com/google/tink/go/keyset" |
| "github.com/google/tink/go/subtle/random" |
| |
| aspb "github.com/google/tink/go/proto/aes_siv_go_proto" |
| tpb "github.com/google/tink/go/proto/tink_go_proto" |
| ) |
| |
| const ( |
| aesSIVKeyVersion = 0 |
| aesSIVTypeURL = "type.googleapis.com/google.crypto.tink.AesSivKey" |
| ) |
| |
| var ( |
| errInvalidAESSIVKeyFormat = errors.New("aes_siv_key_manager: invalid key format") |
| errInvalidAESSIVKeySize = fmt.Errorf("aes_siv_key_manager: key size != %d", subtle.AESSIVKeySize) |
| ) |
| |
| // aesSIVKeyManager generates AES-SIV keys and produces instances of AES-SIV. |
| type aesSIVKeyManager struct{} |
| |
| // Assert that aesSIVKeyManager implements the KeyManager interface. |
| var _ registry.KeyManager = (*aesSIVKeyManager)(nil) |
| |
| // Primitive constructs an AES-SIV for the given serialized AesSivKey. |
| func (km *aesSIVKeyManager) Primitive(serializedKey []byte) (interface{}, error) { |
| if len(serializedKey) == 0 { |
| return nil, errors.New("aes_siv_key_manager: invalid key") |
| } |
| key := new(aspb.AesSivKey) |
| if err := proto.Unmarshal(serializedKey, key); err != nil { |
| return nil, err |
| } |
| if err := km.validateKey(key); err != nil { |
| return nil, err |
| } |
| ret, err := subtle.NewAESSIV(key.KeyValue) |
| if err != nil { |
| return nil, fmt.Errorf("aes_siv_key_manager: cannot create new primitive: %v", err) |
| } |
| return ret, nil |
| } |
| |
| // NewKey generates a new AesSivKey. serializedKeyFormat is optional because |
| // there is only one valid key format. |
| func (km *aesSIVKeyManager) NewKey(serializedKeyFormat []byte) (proto.Message, error) { |
| // A nil serializedKeyFormat is acceptable. If specified, validate. |
| if serializedKeyFormat != nil { |
| keyFormat := new(aspb.AesSivKeyFormat) |
| if err := proto.Unmarshal(serializedKeyFormat, keyFormat); err != nil { |
| return nil, errInvalidAESSIVKeyFormat |
| } |
| if keyFormat.KeySize != subtle.AESSIVKeySize { |
| return nil, errInvalidAESSIVKeySize |
| } |
| } |
| return &aspb.AesSivKey{ |
| Version: aesSIVKeyVersion, |
| KeyValue: random.GetRandomBytes(subtle.AESSIVKeySize), |
| }, nil |
| } |
| |
| // NewKeyData generates a new KeyData. serializedKeyFormat is optional because |
| // there is only one valid key format. This should be used solely by the key |
| // management API. |
| func (km *aesSIVKeyManager) NewKeyData(serializedKeyFormat []byte) (*tpb.KeyData, error) { |
| key, err := km.NewKey(serializedKeyFormat) |
| if err != nil { |
| return nil, err |
| } |
| serializedKey, err := proto.Marshal(key) |
| if err != nil { |
| return nil, fmt.Errorf("aes_siv_key_manager: %v", err) |
| } |
| return &tpb.KeyData{ |
| TypeUrl: aesSIVTypeURL, |
| Value: serializedKey, |
| KeyMaterialType: km.KeyMaterialType(), |
| }, nil |
| } |
| |
| // DoesSupport checks whether this key manager supports the given key type. |
| func (km *aesSIVKeyManager) DoesSupport(typeURL string) bool { |
| return typeURL == aesSIVTypeURL |
| } |
| |
| // TypeURL returns the type URL of keys managed by this key manager. |
| func (km *aesSIVKeyManager) TypeURL() string { |
| return aesSIVTypeURL |
| } |
| |
| // KeyMaterialType returns the key material type of this key manager. |
| func (km *aesSIVKeyManager) KeyMaterialType() tpb.KeyData_KeyMaterialType { |
| return tpb.KeyData_SYMMETRIC |
| } |
| |
| // DeriveKey derives a new key from serializedKeyFormat and pseudorandomness. |
| // Unlike NewKey, DeriveKey validates serializedKeyFormat. |
| func (km *aesSIVKeyManager) DeriveKey(serializedKeyFormat []byte, pseudorandomness io.Reader) (proto.Message, error) { |
| keyFormat := new(aspb.AesSivKeyFormat) |
| if err := proto.Unmarshal(serializedKeyFormat, keyFormat); err != nil { |
| return nil, errInvalidAESSIVKeyFormat |
| } |
| if keyFormat.GetKeySize() != subtle.AESSIVKeySize { |
| return nil, errInvalidAESSIVKeySize |
| } |
| if err := keyset.ValidateKeyVersion(keyFormat.GetVersion(), aesSIVKeyVersion); err != nil { |
| return nil, fmt.Errorf("aes_siv_key_manager: invalid key version: %s", err) |
| } |
| |
| keyValue := make([]byte, subtle.AESSIVKeySize) |
| if _, err := io.ReadFull(pseudorandomness, keyValue); err != nil { |
| return nil, fmt.Errorf("aes_siv_key_manager: not enough pseudorandomness given") |
| } |
| return &aspb.AesSivKey{ |
| Version: aesSIVKeyVersion, |
| KeyValue: keyValue, |
| }, nil |
| } |
| |
| // validateKey validates the given AesSivKey. |
| func (km *aesSIVKeyManager) validateKey(key *aspb.AesSivKey) error { |
| err := keyset.ValidateKeyVersion(key.Version, aesSIVKeyVersion) |
| if err != nil { |
| return fmt.Errorf("aes_siv_key_manager: %v", err) |
| } |
| keySize := uint32(len(key.KeyValue)) |
| if keySize != subtle.AESSIVKeySize { |
| return errInvalidAESSIVKeySize |
| } |
| return nil |
| } |