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// Copyright 2018 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 signature
import (
"fmt"
"slices"
"github.com/tink-crypto/tink-go/v2/internal/internalapi"
"github.com/tink-crypto/tink-go/v2/internal/internalregistry"
"github.com/tink-crypto/tink-go/v2/internal/monitoringutil"
"github.com/tink-crypto/tink-go/v2/internal/primitiveset"
"github.com/tink-crypto/tink-go/v2/keyset"
"github.com/tink-crypto/tink-go/v2/monitoring"
"github.com/tink-crypto/tink-go/v2/tink"
tinkpb "github.com/tink-crypto/tink-go/v2/proto/tink_go_proto"
)
// NewSigner returns a Signer primitive from the given keyset handle.
func NewSigner(handle *keyset.Handle) (tink.Signer, error) {
ps, err := keyset.Primitives[tink.Signer](handle, internalapi.Token{})
if err != nil {
return nil, fmt.Errorf("public_key_sign_factory: cannot obtain primitive set: %s", err)
}
return newWrappedSigner(ps)
}
// wrappedSigner is an Signer implementation that uses the underlying primitive set for signing.
type wrappedSigner struct {
signer tink.Signer
signerKeyID uint32
logger monitoring.Logger
}
// Asserts that wrappedSigner implements the Signer interface.
var _ tink.Signer = (*wrappedSigner)(nil)
type fullSignerAdapter struct {
primitive tink.Signer
prefix []byte
prefixType tinkpb.OutputPrefixType
}
var _ tink.Signer = (*fullSignerAdapter)(nil)
func (a *fullSignerAdapter) Sign(data []byte) ([]byte, error) {
toSign := data
if a.prefixType == tinkpb.OutputPrefixType_LEGACY {
toSign = slices.Concat(data, []byte{0})
}
s, err := a.primitive.Sign(toSign)
if err != nil {
return nil, err
}
return slices.Concat(a.prefix, s), nil
}
// extractFullSigner returns a [tink.Signer] from the given entry as a "full"
// primitive.
//
// It wraps legacy primitives in a full primitive adapter.
func extractFullSigner(entry *primitiveset.Entry[tink.Signer]) tink.Signer {
if entry.FullPrimitive != nil {
return entry.FullPrimitive
}
return &fullSignerAdapter{
primitive: entry.Primitive,
prefix: []byte(entry.Prefix),
prefixType: entry.PrefixType,
}
}
func newWrappedSigner(ps *primitiveset.PrimitiveSet[tink.Signer]) (*wrappedSigner, error) {
signer := extractFullSigner(ps.Primary)
logger, err := createSignerLogger(ps)
if err != nil {
return nil, err
}
return &wrappedSigner{
signer: signer,
signerKeyID: ps.Primary.KeyID,
logger: logger,
}, nil
}
func createSignerLogger(ps *primitiveset.PrimitiveSet[tink.Signer]) (monitoring.Logger, error) {
// Only keysets which contain annotations are monitored.
if len(ps.Annotations) == 0 {
return &monitoringutil.DoNothingLogger{}, nil
}
keysetInfo, err := monitoringutil.KeysetInfoFromPrimitiveSet(ps)
if err != nil {
return nil, err
}
return internalregistry.GetMonitoringClient().NewLogger(&monitoring.Context{
KeysetInfo: keysetInfo,
Primitive: "public_key_sign",
APIFunction: "sign",
})
}
// Sign signs the given data using the primary key.
func (s *wrappedSigner) Sign(data []byte) ([]byte, error) {
signature, err := s.signer.Sign(data)
if err != nil {
s.logger.LogFailure()
return nil, err
}
s.logger.Log(s.signerKeyID, len(data))
return signature, nil
}
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