1// Copyright 2018 Google LLC 2// 3// Licensed under the Apache License, Version 2.0 (the "License"); 4// you may not use this file except in compliance with the License. 5// You may obtain a copy of the License at 6// 7// http://www.apache.org/licenses/LICENSE-2.0 8// 9// Unless required by applicable law or agreed to in writing, software 10// distributed under the License is distributed on an "AS IS" BASIS, 11// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12// See the License for the specific language governing permissions and 13// limitations under the License. 14// 15//////////////////////////////////////////////////////////////////////////////// 16 17package aead 18 19import ( 20 "fmt" 21 22 "google.golang.org/protobuf/proto" 23 "github.com/google/tink/go/aead/subtle" 24 "github.com/google/tink/go/core/registry" 25 "github.com/google/tink/go/keyset" 26 "github.com/google/tink/go/subtle/random" 27 gcmsivpb "github.com/google/tink/go/proto/aes_gcm_siv_go_proto" 28 tinkpb "github.com/google/tink/go/proto/tink_go_proto" 29) 30 31const ( 32 aesGCMSIVKeyVersion = 0 33 aesGCMSIVTypeURL = "type.googleapis.com/google.crypto.tink.AesGcmSivKey" 34) 35 36// common errors 37var errInvalidAESGCMSIVKey = fmt.Errorf("aes_gcm_siv_key_manager: invalid key") 38var errInvalidAESGCMSIVKeyFormat = fmt.Errorf("aes_gcm_siv_key_manager: invalid key format") 39 40// aesGCMSIVKeyManager is an implementation of KeyManager interface. 41// It generates new AESGCMSIVKey keys and produces new instances of AESGCMSIV subtle. 42type aesGCMSIVKeyManager struct{} 43 44// Assert that aesGCMSIVKeyManager implements the KeyManager interface. 45var _ registry.KeyManager = (*aesGCMSIVKeyManager)(nil) 46 47// Primitive creates an AESGCMSIV subtle for the given serialized AESGCMSIVKey proto. 48func (km *aesGCMSIVKeyManager) Primitive(serializedKey []byte) (interface{}, error) { 49 if len(serializedKey) == 0 { 50 return nil, errInvalidAESGCMSIVKey 51 } 52 key := new(gcmsivpb.AesGcmSivKey) 53 if err := proto.Unmarshal(serializedKey, key); err != nil { 54 return nil, errInvalidAESGCMSIVKey 55 } 56 if err := km.validateKey(key); err != nil { 57 return nil, err 58 } 59 ret, err := subtle.NewAESGCMSIV(key.KeyValue) 60 if err != nil { 61 return nil, fmt.Errorf("aes_gcm_siv_key_manager: cannot create new primitive: %s", err) 62 } 63 return ret, nil 64} 65 66// NewKey creates a new key according to specification the given serialized AESGCMSIVKeyFormat. 67func (km *aesGCMSIVKeyManager) NewKey(serializedKeyFormat []byte) (proto.Message, error) { 68 if len(serializedKeyFormat) == 0 { 69 return nil, errInvalidAESGCMSIVKeyFormat 70 } 71 keyFormat := new(gcmsivpb.AesGcmSivKeyFormat) 72 if err := proto.Unmarshal(serializedKeyFormat, keyFormat); err != nil { 73 return nil, errInvalidAESGCMSIVKeyFormat 74 } 75 if err := km.validateKeyFormat(keyFormat); err != nil { 76 return nil, fmt.Errorf("aes_gcm_siv_key_manager: invalid key format: %s", err) 77 } 78 keyValue := random.GetRandomBytes(keyFormat.KeySize) 79 return &gcmsivpb.AesGcmSivKey{ 80 Version: aesGCMSIVKeyVersion, 81 KeyValue: keyValue, 82 }, nil 83} 84 85// NewKeyData creates a new KeyData according to specification in the given serialized 86// AESGCMSIVKeyFormat. 87// It should be used solely by the key management API. 88func (km *aesGCMSIVKeyManager) NewKeyData(serializedKeyFormat []byte) (*tinkpb.KeyData, error) { 89 key, err := km.NewKey(serializedKeyFormat) 90 if err != nil { 91 return nil, err 92 } 93 serializedKey, err := proto.Marshal(key) 94 if err != nil { 95 return nil, err 96 } 97 return &tinkpb.KeyData{ 98 TypeUrl: aesGCMSIVTypeURL, 99 Value: serializedKey, 100 KeyMaterialType: tinkpb.KeyData_SYMMETRIC, 101 }, nil 102} 103 104// DoesSupport indicates if this key manager supports the given key type. 105func (km *aesGCMSIVKeyManager) DoesSupport(typeURL string) bool { 106 return typeURL == aesGCMSIVTypeURL 107} 108 109// TypeURL returns the key type of keys managed by this key manager. 110func (km *aesGCMSIVKeyManager) TypeURL() string { 111 return aesGCMSIVTypeURL 112} 113 114// validateKey validates the given AESGCMSIVKey. 115func (km *aesGCMSIVKeyManager) validateKey(key *gcmsivpb.AesGcmSivKey) error { 116 err := keyset.ValidateKeyVersion(key.Version, aesGCMSIVKeyVersion) 117 if err != nil { 118 return fmt.Errorf("aes_gcm_siv_key_manager: %s", err) 119 } 120 keySize := uint32(len(key.KeyValue)) 121 if err := subtle.ValidateAESKeySize(keySize); err != nil { 122 return fmt.Errorf("aes_gcm_siv_key_manager: %s", err) 123 } 124 return nil 125} 126 127// validateKeyFormat validates the given AESGCMSIVKeyFormat. 128func (km *aesGCMSIVKeyManager) validateKeyFormat(format *gcmsivpb.AesGcmSivKeyFormat) error { 129 if err := subtle.ValidateAESKeySize(format.KeySize); err != nil { 130 return fmt.Errorf("aes_gcm_siv_key_manager: %s", err) 131 } 132 return nil 133} 134