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// Copyright The Notary Project Authors.
// 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 (
"crypto"
"crypto/ecdsa"
"crypto/rsa"
"crypto/x509"
"errors"
"fmt"
)
// Signer is used to sign bytes generated after signature envelope created.
type Signer interface {
// Sign signs the payload and returns the raw signature and certificates.
Sign(payload []byte) ([]byte, []*x509.Certificate, error)
// KeySpec returns the key specification.
KeySpec() (KeySpec, error)
}
// LocalSigner is only used by built-in signers to sign.
type LocalSigner interface {
Signer
// CertificateChain returns the certificate chain.
CertificateChain() ([]*x509.Certificate, error)
// PrivateKey returns the private key.
PrivateKey() crypto.PrivateKey
}
// localSigner implements LocalSigner interface.
//
// Note that localSigner only holds the signing key, keySpec and certificate
// chain. The underlying signing implementation is provided by the underlying
// crypto library for the specific signature format like go-jwt or go-cose.
type localSigner struct {
keySpec KeySpec
key crypto.PrivateKey
certs []*x509.Certificate
}
// NewLocalSigner returns a new signer with given certificates and private key.
func NewLocalSigner(certs []*x509.Certificate, key crypto.PrivateKey) (LocalSigner, error) {
if len(certs) == 0 {
return nil, &InvalidArgumentError{
Param: "certs",
Err: errors.New("empty certs"),
}
}
keySpec, err := ExtractKeySpec(certs[0])
if err != nil {
return nil, err
}
if !isKeyPair(key, certs[0].PublicKey, keySpec) {
return nil, &InvalidArgumentError{
Param: "key and certs",
Err: errors.New("key not matches certificate"),
}
}
return &localSigner{
keySpec: keySpec,
key: key,
certs: certs,
}, nil
}
// isKeyPair checks if the private key matches the provided public key.
func isKeyPair(priv crypto.PrivateKey, pub crypto.PublicKey, keySpec KeySpec) bool {
switch keySpec.Type {
case KeyTypeRSA:
privateKey, ok := priv.(*rsa.PrivateKey)
if !ok {
return false
}
return privateKey.PublicKey.Equal(pub)
case KeyTypeEC:
privateKey, ok := priv.(*ecdsa.PrivateKey)
if !ok {
return false
}
return privateKey.PublicKey.Equal(pub)
default:
return false
}
}
// Sign signs the content and returns the raw signature and certificates.
// This implementation should never be used by built-in signers.
func (s *localSigner) Sign(content []byte) ([]byte, []*x509.Certificate, error) {
return nil, nil, fmt.Errorf("local signer doesn't support sign")
}
// KeySpec returns the key specification.
func (s *localSigner) KeySpec() (KeySpec, error) {
return s.keySpec, nil
}
// CertificateChain returns the certificate chain.
func (s *localSigner) CertificateChain() ([]*x509.Certificate, error) {
return s.certs, nil
}
// PrivateKey returns the private key.
func (s *localSigner) PrivateKey() crypto.PrivateKey {
return s.key
}
// VerifyAuthenticity verifies the certificate chain in the given SignerInfo
// with one of the trusted certificates and returns a certificate that matches
// with one of the certificates in the SignerInfo.
//
// Reference: https://github.com/notaryproject/notaryproject/blob/main/specs/trust-store-trust-policy.md#steps
func VerifyAuthenticity(signerInfo *SignerInfo, trustedCerts []*x509.Certificate) (*x509.Certificate, error) {
if len(trustedCerts) == 0 {
return nil, &InvalidArgumentError{Param: "trustedCerts"}
}
if signerInfo == nil {
return nil, &InvalidArgumentError{Param: "signerInfo"}
}
for _, trust := range trustedCerts {
for _, cert := range signerInfo.CertificateChain {
if trust.Equal(cert) {
return trust, nil
}
}
}
return nil, &SignatureAuthenticityError{}
}
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