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aead_factory.go
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/
aead_factory.go
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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 aead
import (
"fmt"
"github.com/tink-crypto/tink-go/v2/core/cryptofmt"
"github.com/tink-crypto/tink-go/v2/core/primitiveset"
"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/keyset"
"github.com/tink-crypto/tink-go/v2/monitoring"
"github.com/tink-crypto/tink-go/v2/tink"
)
// New returns an AEAD primitive from the given keyset handle.
func New(handle *keyset.Handle) (tink.AEAD, error) {
ps, err := handle.Primitives()
if err != nil {
return nil, fmt.Errorf("aead_factory: cannot obtain primitive set: %s", err)
}
return newWrappedAead(ps)
}
// wrappedAead is an AEAD implementation that uses the underlying primitive set for encryption
// and decryption.
type wrappedAead struct {
ps *primitiveset.PrimitiveSet
encLogger monitoring.Logger
decLogger monitoring.Logger
}
func newWrappedAead(ps *primitiveset.PrimitiveSet) (*wrappedAead, error) {
if _, ok := (ps.Primary.Primitive).(tink.AEAD); !ok {
return nil, fmt.Errorf("aead_factory: not an AEAD primitive")
}
for _, primitives := range ps.Entries {
for _, p := range primitives {
if _, ok := (p.Primitive).(tink.AEAD); !ok {
return nil, fmt.Errorf("aead_factory: not an AEAD primitive")
}
}
}
encLogger, decLogger, err := createLoggers(ps)
if err != nil {
return nil, err
}
return &wrappedAead{
ps: ps,
encLogger: encLogger,
decLogger: decLogger,
}, nil
}
func createLoggers(ps *primitiveset.PrimitiveSet) (monitoring.Logger, monitoring.Logger, error) {
if len(ps.Annotations) == 0 {
return &monitoringutil.DoNothingLogger{}, &monitoringutil.DoNothingLogger{}, nil
}
client := internalregistry.GetMonitoringClient()
keysetInfo, err := monitoringutil.KeysetInfoFromPrimitiveSet(ps)
if err != nil {
return nil, nil, err
}
encLogger, err := client.NewLogger(&monitoring.Context{
Primitive: "aead",
APIFunction: "encrypt",
KeysetInfo: keysetInfo,
})
if err != nil {
return nil, nil, err
}
decLogger, err := client.NewLogger(&monitoring.Context{
Primitive: "aead",
APIFunction: "decrypt",
KeysetInfo: keysetInfo,
})
if err != nil {
return nil, nil, err
}
return encLogger, decLogger, nil
}
// Encrypt encrypts the given plaintext with the given associatedData.
// It returns the concatenation of the primary's identifier and the ciphertext.
func (a *wrappedAead) Encrypt(plaintext, associatedData []byte) ([]byte, error) {
primary := a.ps.Primary
p, ok := (primary.Primitive).(tink.AEAD)
if !ok {
return nil, fmt.Errorf("aead_factory: not an AEAD primitive")
}
ct, err := p.Encrypt(plaintext, associatedData)
if err != nil {
a.encLogger.LogFailure()
return nil, err
}
a.encLogger.Log(primary.KeyID, len(plaintext))
if len(primary.Prefix) == 0 {
return ct, nil
}
output := make([]byte, 0, len(primary.Prefix)+len(ct))
output = append(output, primary.Prefix...)
output = append(output, ct...)
return output, nil
}
// Decrypt decrypts the given ciphertext and authenticates it with the given
// associatedData. It returns the corresponding plaintext if the
// ciphertext is authenticated.
func (a *wrappedAead) Decrypt(ciphertext, associatedData []byte) ([]byte, error) {
// try non-raw keys
prefixSize := cryptofmt.NonRawPrefixSize
if len(ciphertext) > prefixSize {
prefix := ciphertext[:prefixSize]
ctNoPrefix := ciphertext[prefixSize:]
entries, err := a.ps.EntriesForPrefix(string(prefix))
if err == nil {
for i := 0; i < len(entries); i++ {
p, ok := (entries[i].Primitive).(tink.AEAD)
if !ok {
return nil, fmt.Errorf("aead_factory: not an AEAD primitive")
}
pt, err := p.Decrypt(ctNoPrefix, associatedData)
if err == nil {
a.decLogger.Log(entries[i].KeyID, len(ctNoPrefix))
return pt, nil
}
}
}
}
// try raw keys
entries, err := a.ps.RawEntries()
if err == nil {
for i := 0; i < len(entries); i++ {
p, ok := (entries[i].Primitive).(tink.AEAD)
if !ok {
return nil, fmt.Errorf("aead_factory: not an AEAD primitive")
}
pt, err := p.Decrypt(ciphertext, associatedData)
if err == nil {
a.decLogger.Log(entries[i].KeyID, len(ciphertext))
return pt, nil
}
}
}
// nothing worked
a.decLogger.LogFailure()
return nil, fmt.Errorf("aead_factory: decryption failed")
}