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// Copyright 2022 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 keyderivation
import (
"errors"
"fmt"
"github.com/tink-crypto/tink-go/v2/internal/internalapi"
"github.com/tink-crypto/tink-go/v2/internal/primitiveset"
"github.com/tink-crypto/tink-go/v2/internal/protoserialization"
"github.com/tink-crypto/tink-go/v2/keyset"
tinkpb "github.com/tink-crypto/tink-go/v2/proto/tink_go_proto"
)
var errNotKeysetDeriverPrimitive = errors.New("keyset_deriver_factory: not a Keyset Deriver primitive")
// New generates a new instance of the Keyset Deriver primitive.
func New(handle *keyset.Handle) (KeysetDeriver, error) {
ps, err := keyset.Primitives[KeysetDeriver](handle, internalapi.Token{})
if err != nil {
return nil, fmt.Errorf("keyset_deriver_factory: cannot obtain primitive set: %v", err)
}
return &wrappedKeysetDeriver{ps: ps}, nil
}
// wrappedKeysetDeriver is a Keyset Deriver implementation that uses the underlying primitive set to derive keysets.
type wrappedKeysetDeriver struct {
ps *primitiveset.PrimitiveSet[KeysetDeriver]
}
// Asserts that wrappedKeysetDeriver implements the KeysetDeriver interface.
var _ KeysetDeriver = (*wrappedKeysetDeriver)(nil)
func (w *wrappedKeysetDeriver) DeriveKeyset(salt []byte) (*keyset.Handle, error) {
keys := make([]*tinkpb.Keyset_Key, 0, len(w.ps.EntriesInKeysetOrder))
for _, e := range w.ps.EntriesInKeysetOrder {
handle, err := e.Primitive.DeriveKeyset(salt)
if err != nil {
return nil, errors.New("keyset_deriver_factory: keyset derivation failed")
}
if handle.Len() != 1 {
return nil, errors.New("keyset_deriver_factory: primitive must derive keyset handle with exactly one key")
}
entry, err := handle.Entry(0)
if err != nil {
return nil, fmt.Errorf("keyset_deriver_factory: cannot obtain entry from derived keyset: %v", err)
}
keySerialization, err := protoserialization.SerializeKey(entry.Key())
if err != nil {
return nil, fmt.Errorf("keyset_deriver_factory: cannot get proto key from entry: %v", err)
}
// Set all fields, except for KeyData, to match the Entry in the keyset.
key := &tinkpb.Keyset_Key{
KeyData: keySerialization.KeyData(),
Status: e.Status,
KeyId: e.KeyID,
OutputPrefixType: e.PrefixType,
}
keys = append(keys, key)
}
ks := &tinkpb.Keyset{
PrimaryKeyId: w.ps.Primary.KeyID,
Key: keys,
}
return keysetHandle(ks)
}
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