| // 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" |
| |
| "github.com/golang/protobuf/proto" |
| "github.com/google/tink/go/keyset" |
| "github.com/google/tink/go/prf/subtle" |
| "github.com/google/tink/go/subtle/random" |
| commonpb "github.com/google/tink/go/proto/common_go_proto" |
| hmacpb "github.com/google/tink/go/proto/hmac_prf_go_proto" |
| tinkpb "github.com/google/tink/go/proto/tink_go_proto" |
| ) |
| |
| const ( |
| hmacprfKeyVersion = 0 |
| hmacprfTypeURL = "type.googleapis.com/google.crypto.tink.HmacPrfKey" |
| ) |
| |
| var errInvalidHMACPRFKey = errors.New("hmac_prf_key_manager: invalid key") |
| var errInvalidHMACPRFKeyFormat = errors.New("hmac_prf_key_manager: invalid key format") |
| |
| // hmacprfKeyManager generates new HMAC PRF keys and produces new instances of HMAC. |
| type hmacprfKeyManager struct{} |
| |
| // newHMACPRFKeyManager returns a new hmacprfKeyManager. |
| func newHMACPRFKeyManager() *hmacprfKeyManager { |
| return new(hmacprfKeyManager) |
| } |
| |
| // Primitive constructs a HMAC instance for the given serialized HMACKey. |
| func (km *hmacprfKeyManager) Primitive(serializedKey []byte) (interface{}, error) { |
| if len(serializedKey) == 0 { |
| return nil, errInvalidHMACPRFKey |
| } |
| key := new(hmacpb.HmacPrfKey) |
| if err := proto.Unmarshal(serializedKey, key); err != nil { |
| return nil, errInvalidHMACPRFKey |
| } |
| if err := km.validateKey(key); err != nil { |
| return nil, err |
| } |
| hash := commonpb.HashType_name[int32(key.Params.Hash)] |
| hmac, err := subtle.NewHMACPRF(hash, key.KeyValue) |
| if err != nil { |
| return nil, err |
| } |
| return hmac, nil |
| } |
| |
| // NewKey generates a new HMACPRFKey according to specification in the given HMACPRFKeyFormat. |
| func (km *hmacprfKeyManager) NewKey(serializedKeyFormat []byte) (proto.Message, error) { |
| if len(serializedKeyFormat) == 0 { |
| return nil, errInvalidHMACPRFKeyFormat |
| } |
| keyFormat := new(hmacpb.HmacPrfKeyFormat) |
| if err := proto.Unmarshal(serializedKeyFormat, keyFormat); err != nil { |
| return nil, errInvalidHMACPRFKeyFormat |
| } |
| if err := km.validateKeyFormat(keyFormat); err != nil { |
| return nil, fmt.Errorf("hmac_prf_key_manager: invalid key format: %s", err) |
| } |
| keyValue := random.GetRandomBytes(keyFormat.KeySize) |
| return &hmacpb.HmacPrfKey{ |
| Version: hmacprfKeyVersion, |
| Params: keyFormat.Params, |
| KeyValue: keyValue, |
| }, nil |
| } |
| |
| // NewKeyData generates a new KeyData according to specification in the given |
| // serialized HMACPRFKeyFormat. This should be used solely by the key management API. |
| func (km *hmacprfKeyManager) 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, errInvalidHMACPRFKeyFormat |
| } |
| |
| return &tinkpb.KeyData{ |
| TypeUrl: hmacprfTypeURL, |
| Value: serializedKey, |
| KeyMaterialType: tinkpb.KeyData_SYMMETRIC, |
| }, nil |
| } |
| |
| // DoesSupport checks whether this KeyManager supports the given key type. |
| func (km *hmacprfKeyManager) DoesSupport(typeURL string) bool { |
| return typeURL == hmacprfTypeURL |
| } |
| |
| // TypeURL returns the type URL of keys managed by this KeyManager. |
| func (km *hmacprfKeyManager) TypeURL() string { |
| return hmacprfTypeURL |
| } |
| |
| // validateKey validates the given HMACPRFKey. It only validates the version of the |
| // key because other parameters will be validated in primitive construction. |
| func (km *hmacprfKeyManager) validateKey(key *hmacpb.HmacPrfKey) error { |
| err := keyset.ValidateKeyVersion(key.Version, hmacprfKeyVersion) |
| if err != nil { |
| return fmt.Errorf("hmac_prf_key_manager: invalid version: %s", err) |
| } |
| keySize := uint32(len(key.KeyValue)) |
| hash := commonpb.HashType_name[int32(key.Params.Hash)] |
| return subtle.ValidateHMACPRFParams(hash, keySize) |
| } |
| |
| // validateKeyFormat validates the given HMACKeyFormat |
| func (km *hmacprfKeyManager) validateKeyFormat(format *hmacpb.HmacPrfKeyFormat) error { |
| if format.Params == nil { |
| return fmt.Errorf("null HMAC params") |
| } |
| hash := commonpb.HashType_name[int32(format.Params.Hash)] |
| return subtle.ValidateHMACPRFParams(hash, format.KeySize) |
| } |