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// Copyright 2022 Northern.tech AS
//
// 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.
//go:build linux
// +build linux
package artifact
import (
"encoding/base64"
"strings"
"github.com/mendersoftware/openssl"
"github.com/pkg/errors"
)
const (
pkcs11URIPrefix = "pkcs11:"
pkcsEngineId = "pkcs11"
)
type PKCS11Signer struct {
Key openssl.PrivateKey
}
func NewPKCS11Signer(pkcsKey string) (*PKCS11Signer, error) {
if len(pkcsKey) == 0 {
return nil, errors.New("PKCS#11 signer: missing key")
}
key, err := loadPrivateKey(pkcsKey, pkcsEngineId)
if err != nil {
return nil, errors.Wrap(err, "PKCS#11: failed to load private key")
}
return &PKCS11Signer{
Key: key,
}, nil
}
func (s *PKCS11Signer) Sign(message []byte) ([]byte, error) {
sig, err := s.Key.SignPKCS1v15(openssl.SHA256_Method, message[:])
if err != nil {
return nil, errors.Wrap(err, "PKCS#11 signer: error signing image")
}
enc := make([]byte, base64.StdEncoding.EncodedLen(len(sig)))
base64.StdEncoding.Encode(enc, sig)
return enc, nil
}
func (s *PKCS11Signer) Verify(message, sig []byte) error {
dec := make([]byte, base64.StdEncoding.DecodedLen(len(sig)))
decLen, err := base64.StdEncoding.Decode(dec, sig)
if err != nil {
return errors.Wrap(err, "signer: error decoding signature")
}
err = s.Key.VerifyPKCS1v15(openssl.SHA256_Method, message[:], dec[:decLen])
return errors.Wrap(err, "failed to verify PKCS#11 signature")
}
var engineLoadPrivateKeyFunc = openssl.EngineLoadPrivateKey
func loadPrivateKey(keyFile string, engineId string) (key openssl.PrivateKey, err error) {
if strings.HasPrefix(keyFile, pkcs11URIPrefix) {
engine, err := openssl.EngineById(engineId)
if err != nil {
return nil, err
}
key, err = engineLoadPrivateKeyFunc(engine, keyFile)
if err != nil {
return nil, err
}
} else {
return nil, errors.New("PKCS#11 URI prefix not found")
}
return key, nil
}
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