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// Copyright 2025 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 aesgcmhkdf
import (
"fmt"
"google.golang.org/protobuf/proto"
"github.com/tink-crypto/tink-go/v2/insecuresecretdataaccess"
"github.com/tink-crypto/tink-go/v2/internal/protoserialization"
"github.com/tink-crypto/tink-go/v2/key"
"github.com/tink-crypto/tink-go/v2/secretdata"
streamaeadpb "github.com/tink-crypto/tink-go/v2/proto/aes_gcm_hkdf_streaming_go_proto"
commonpb "github.com/tink-crypto/tink-go/v2/proto/common_go_proto"
tinkpb "github.com/tink-crypto/tink-go/v2/proto/tink_go_proto"
)
const typeURL = "type.googleapis.com/google.crypto.tink.AesGcmHkdfStreamingKey"
type keySerializer struct{}
var _ protoserialization.KeySerializer = (*keySerializer)(nil)
func hashTypeToProto(ht HashType) (commonpb.HashType, error) {
switch ht {
case SHA1:
return commonpb.HashType_SHA1, nil
case SHA256:
return commonpb.HashType_SHA256, nil
case SHA512:
return commonpb.HashType_SHA512, nil
default:
return commonpb.HashType_UNKNOWN_HASH, fmt.Errorf("unknown hash type: %v", ht)
}
}
func (s *keySerializer) SerializeKey(k key.Key) (*protoserialization.KeySerialization, error) {
actualKey, ok := k.(*Key)
if !ok {
return nil, fmt.Errorf("invalid key type: got %T, want %T", k, (*Key)(nil))
}
// Case where the key is empty.
if actualKey.KeyBytes().Len() == 0 {
return nil, fmt.Errorf("invalid key")
}
actualParameters, ok := actualKey.Parameters().(*Parameters)
if !ok {
return nil, fmt.Errorf("key parameters is not a aesgcmhkdf.Parameters")
}
hkdfHashType, err := hashTypeToProto(actualParameters.HKDFHashType())
if err != nil {
return nil, err
}
protoKey := &streamaeadpb.AesGcmHkdfStreamingKey{
Version: 0,
KeyValue: actualKey.KeyBytes().Data(insecuresecretdataaccess.Token{}),
Params: &streamaeadpb.AesGcmHkdfStreamingParams{
HkdfHashType: hkdfHashType,
DerivedKeySize: uint32(actualParameters.DerivedKeySizeInBytes()),
CiphertextSegmentSize: uint32(actualParameters.SegmentSizeInBytes()),
},
}
serializedKey, err := proto.Marshal(protoKey)
if err != nil {
return nil, err
}
keyData := &tinkpb.KeyData{
TypeUrl: typeURL,
Value: serializedKey,
KeyMaterialType: tinkpb.KeyData_SYMMETRIC,
}
return protoserialization.NewKeySerialization(keyData, tinkpb.OutputPrefixType_RAW, 0)
}
type keyParser struct{}
var _ protoserialization.KeyParser = (*keyParser)(nil)
func hashTypeFromProto(ht commonpb.HashType) (HashType, error) {
switch ht {
case commonpb.HashType_SHA1:
return SHA1, nil
case commonpb.HashType_SHA256:
return SHA256, nil
case commonpb.HashType_SHA512:
return SHA512, nil
default:
return HashTypeUnknown, fmt.Errorf("unknown hash type: %v", ht)
}
}
func (s *keyParser) ParseKey(keySerialization *protoserialization.KeySerialization) (key.Key, error) {
if keySerialization == nil {
return nil, fmt.Errorf("key serialization is nil")
}
keyData := keySerialization.KeyData()
if keyData.GetTypeUrl() != typeURL {
return nil, fmt.Errorf("invalid type URL: got %q, want %q", keyData.GetTypeUrl(), typeURL)
}
if keyData.GetKeyMaterialType() != tinkpb.KeyData_SYMMETRIC {
return nil, fmt.Errorf("key is not a SYMMETRIC key")
}
protoKey := new(streamaeadpb.AesGcmHkdfStreamingKey)
if err := proto.Unmarshal(keyData.GetValue(), protoKey); err != nil {
return nil, err
}
if protoKey.GetVersion() != 0 {
return nil, fmt.Errorf("unsupported key version: got %q, want %q", protoKey.GetVersion(), 0)
}
paramsProto := protoKey.GetParams()
hkdfHashType, err := hashTypeFromProto(paramsProto.GetHkdfHashType())
if err != nil {
return nil, err
}
params, err := NewParameters(ParametersOpts{
KeySizeInBytes: len(protoKey.GetKeyValue()),
DerivedKeySizeInBytes: int(paramsProto.GetDerivedKeySize()),
HKDFHashType: hkdfHashType,
SegmentSizeInBytes: int32(paramsProto.GetCiphertextSegmentSize()),
})
if err != nil {
return nil, err
}
keyBytes := secretdata.NewBytesFromData(protoKey.GetKeyValue(), insecuresecretdataaccess.Token{})
return NewKey(params, keyBytes)
}
type parametersSerializer struct{}
var _ protoserialization.ParametersSerializer = (*parametersSerializer)(nil)
func (s *parametersSerializer) Serialize(params key.Parameters) (*tinkpb.KeyTemplate, error) {
actualParams, ok := params.(*Parameters)
if !ok {
return nil, fmt.Errorf("parameters is not a %T", (*Parameters)(nil))
}
hkdfHashType, err := hashTypeToProto(actualParams.HKDFHashType())
if err != nil {
return nil, fmt.Errorf("invalid HKDF hash type: %v", err)
}
keyFormat := &streamaeadpb.AesGcmHkdfStreamingKeyFormat{
Version: 0,
Params: &streamaeadpb.AesGcmHkdfStreamingParams{
HkdfHashType: hkdfHashType,
DerivedKeySize: uint32(actualParams.DerivedKeySizeInBytes()),
CiphertextSegmentSize: uint32(actualParams.SegmentSizeInBytes()),
},
KeySize: uint32(actualParams.KeySizeInBytes()),
}
serializedParams, err := proto.Marshal(keyFormat)
if err != nil {
return nil, fmt.Errorf("failed to marshal key format: %v", err)
}
return &tinkpb.KeyTemplate{
TypeUrl: typeURL,
Value: serializedParams,
OutputPrefixType: tinkpb.OutputPrefixType_RAW,
}, nil
}
type parametersParser struct{}
var _ protoserialization.ParametersParser = (*parametersParser)(nil)
func (s *parametersParser) Parse(kt *tinkpb.KeyTemplate) (key.Parameters, error) {
if kt == nil {
return nil, fmt.Errorf("parameters serialization is nil")
}
if kt.GetTypeUrl() != typeURL {
return nil, fmt.Errorf("invalid type URL: got %q, want %q", kt.GetTypeUrl(), typeURL)
}
if kt.GetOutputPrefixType() != tinkpb.OutputPrefixType_RAW {
return nil, fmt.Errorf("output prefix type is not RAW")
}
keyFormat := new(streamaeadpb.AesGcmHkdfStreamingKeyFormat)
if err := proto.Unmarshal(kt.GetValue(), keyFormat); err != nil {
return nil, fmt.Errorf("failed to unmarshal key format: %v", err)
}
if keyFormat.GetVersion() != 0 {
return nil, fmt.Errorf("unsupported key version: got %d, want %d", keyFormat.GetVersion(), 0)
}
protoParams := keyFormat.GetParams()
hkdfHashType, err := hashTypeFromProto(protoParams.GetHkdfHashType())
if err != nil {
return nil, fmt.Errorf("invalid HKDF hash type: %v", err)
}
return NewParameters(ParametersOpts{
KeySizeInBytes: int(keyFormat.GetKeySize()),
DerivedKeySizeInBytes: int(protoParams.GetDerivedKeySize()),
HKDFHashType: hkdfHashType,
SegmentSizeInBytes: int32(protoParams.GetCiphertextSegmentSize()),
})
}
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