| // 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 hybrid |
| |
| import ( |
| "errors" |
| "fmt" |
| "strings" |
| |
| "github.com/golang/protobuf/proto" |
| "github.com/google/tink/go/core/registry" |
| subtle "github.com/google/tink/go/subtle/hybrid" |
| "github.com/google/tink/go/tink" |
| ctrhmacpb "github.com/google/tink/proto/aes_ctr_hmac_aead_go_proto" |
| gcmpb "github.com/google/tink/proto/aes_gcm_go_proto" |
| tinkpb "github.com/google/tink/proto/tink_go_proto" |
| ) |
| |
| const ( |
| aesGCMTypeURL = "type.googleapis.com/google.crypto.tink.AesGcmKey" |
| aesCTRHMACAEADTypeURL = "type.googleapis.com/google.crypto.tink.AesCtrHmacAeadKey" |
| ) |
| |
| // registerECIESAEADHKDFDemHelper registers a DEM helper. |
| type registerECIESAEADHKDFDemHelper struct { |
| demKeyURL string |
| keyData []byte |
| symmetricKeySize uint32 |
| aesCTRSize uint32 |
| } |
| |
| var _ subtle.EciesAEADHKDFDEMHelper = (*registerECIESAEADHKDFDemHelper)(nil) |
| |
| // newRegisterECIESAEADHKDFDemHelper initializes and returns a RegisterECIESAEADHKDFDemHelper |
| func newRegisterECIESAEADHKDFDemHelper(k *tinkpb.KeyTemplate) (*registerECIESAEADHKDFDemHelper, error) { |
| var len uint32 |
| var a uint32 |
| var skf []byte |
| var err error |
| u := k.TypeUrl |
| |
| if strings.Compare(u, aesGCMTypeURL) == 0 { |
| gcmKeyFormat := new(gcmpb.AesGcmKeyFormat) |
| if err := proto.Unmarshal(k.Value, gcmKeyFormat); err != nil { |
| return nil, err |
| } |
| len = gcmKeyFormat.KeySize |
| a = 0 |
| skf, err = proto.Marshal(gcmKeyFormat) |
| if err != nil { |
| return nil, fmt.Errorf("failed to serialize key format, error :%v", err) |
| } |
| } else if strings.Compare(u, aesCTRHMACAEADTypeURL) == 0 { |
| aeadKeyFormat := new(ctrhmacpb.AesCtrHmacAeadKeyFormat) |
| if err := proto.Unmarshal(k.Value, aeadKeyFormat); err != nil { |
| return nil, err |
| } |
| if aeadKeyFormat.AesCtrKeyFormat == nil || aeadKeyFormat.HmacKeyFormat == nil { |
| return nil, fmt.Errorf("failed to deserialize key format") |
| } |
| a = aeadKeyFormat.AesCtrKeyFormat.KeySize |
| len = a + aeadKeyFormat.HmacKeyFormat.KeySize |
| skf, err = proto.Marshal(aeadKeyFormat) |
| if err != nil { |
| return nil, fmt.Errorf("failed to serialize key format, error :%v", err) |
| } |
| } else { |
| return nil, fmt.Errorf("unsupported AEAD DEM key type: %s", u) |
| } |
| km, err := registry.GetKeyManager(k.TypeUrl) |
| if err != nil { |
| return nil, fmt.Errorf("failed to fetch KeyManager, error: %v", err) |
| } |
| |
| key, err := km.NewKey(skf) |
| if err != nil { |
| return nil, fmt.Errorf("failed to fetch key, error: %v", err) |
| } |
| sk, err := proto.Marshal(key) |
| if err != nil { |
| return nil, fmt.Errorf("failed to serialize key, error: %v", err) |
| } |
| |
| return ®isterECIESAEADHKDFDemHelper{ |
| demKeyURL: u, |
| keyData: sk, |
| symmetricKeySize: len, |
| aesCTRSize: a, |
| }, nil |
| } |
| |
| // GetSymmetricKeySize returns the symmetric key size |
| func (r *registerECIESAEADHKDFDemHelper) GetSymmetricKeySize() uint32 { |
| return r.symmetricKeySize |
| |
| } |
| |
| // GetAEAD returns the AEAD primitive from the DEM |
| func (r *registerECIESAEADHKDFDemHelper) GetAEAD(symmetricKeyValue []byte) (tink.AEAD, error) { |
| var sk []byte |
| var pErr error |
| if uint32(len(symmetricKeyValue)) != r.GetSymmetricKeySize() { |
| return nil, errors.New("symmetric key has incorrect length") |
| } |
| if strings.Compare(r.demKeyURL, aesGCMTypeURL) == 0 { |
| gcmKey := new(gcmpb.AesGcmKey) |
| if err := proto.Unmarshal(r.keyData, gcmKey); err != nil { |
| return nil, err |
| } |
| gcmKey.KeyValue = symmetricKeyValue |
| sk, pErr = proto.Marshal(gcmKey) |
| if pErr != nil { |
| return nil, fmt.Errorf("failed to serialize key, error: %v", pErr) |
| } |
| |
| } else if strings.Compare(r.demKeyURL, aesCTRHMACAEADTypeURL) == 0 { |
| aesCTR := new(ctrhmacpb.AesCtrHmacAeadKey) |
| if err := proto.Unmarshal(r.keyData, aesCTR); err != nil { |
| return nil, err |
| } |
| aesCTR.AesCtrKey.KeyValue = symmetricKeyValue[:r.aesCTRSize] |
| aesCTR.HmacKey.KeyValue = symmetricKeyValue[r.aesCTRSize:] |
| sk, pErr = proto.Marshal(aesCTR) |
| if pErr != nil { |
| return nil, fmt.Errorf("failed to serialize key, error: %v", pErr) |
| } |
| |
| } else { |
| return nil, fmt.Errorf("unsupported AEAD DEM key type: %s", r.demKeyURL) |
| } |
| |
| p, err := registry.Primitive(r.demKeyURL, sk) |
| if err != nil { |
| return nil, err |
| } |
| g := p.(tink.AEAD) |
| return g, nil |
| } |