authority.go

Documentation: k8s.io/kubernetes/pkg/controller/certificates/authority

     1  /*
     2  Copyright 2019 The Kubernetes Authors.
     3  
     4  Licensed under the Apache License, Version 2.0 (the "License");
     5  you may not use this file except in compliance with the License.
     6  You may obtain a copy of the License at
     7  
     8      http://www.apache.org/licenses/LICENSE-2.0
     9  
    10  Unless required by applicable law or agreed to in writing, software
    11  distributed under the License is distributed on an "AS IS" BASIS,
    12  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    13  See the License for the specific language governing permissions and
    14  limitations under the License.
    15  */
    16  
    17  package authority
    18  
    19  import (
    20  	"crypto"
    21  	"crypto/rand"
    22  	"crypto/x509"
    23  	"fmt"
    24  	"math/big"
    25  )
    26  
    27  var serialNumberLimit = new(big.Int).Lsh(big.NewInt(1), 128)
    28  
    29  // CertificateAuthority implements a certificate authority that supports policy
    30  // based signing. It's used by the signing controller.
    31  type CertificateAuthority struct {
    32  	// RawCert is an optional field to determine if signing cert/key pairs have changed
    33  	RawCert []byte
    34  	// RawKey is an optional field to determine if signing cert/key pairs have changed
    35  	RawKey []byte
    36  
    37  	Certificate *x509.Certificate
    38  	PrivateKey  crypto.Signer
    39  }
    40  
    41  // Sign signs a certificate request, applying a SigningPolicy and returns a DER
    42  // encoded x509 certificate.
    43  func (ca *CertificateAuthority) Sign(crDER []byte, policy SigningPolicy) ([]byte, error) {
    44  	cr, err := x509.ParseCertificateRequest(crDER)
    45  	if err != nil {
    46  		return nil, fmt.Errorf("unable to parse certificate request: %v", err)
    47  	}
    48  	if err := cr.CheckSignature(); err != nil {
    49  		return nil, fmt.Errorf("unable to verify certificate request signature: %v", err)
    50  	}
    51  
    52  	serialNumber, err := rand.Int(rand.Reader, serialNumberLimit)
    53  	if err != nil {
    54  		return nil, fmt.Errorf("unable to generate a serial number for %s: %v", cr.Subject.CommonName, err)
    55  	}
    56  
    57  	tmpl := &x509.Certificate{
    58  		SerialNumber:       serialNumber,
    59  		Subject:            cr.Subject,
    60  		DNSNames:           cr.DNSNames,
    61  		IPAddresses:        cr.IPAddresses,
    62  		EmailAddresses:     cr.EmailAddresses,
    63  		URIs:               cr.URIs,
    64  		PublicKeyAlgorithm: cr.PublicKeyAlgorithm,
    65  		PublicKey:          cr.PublicKey,
    66  		Extensions:         cr.Extensions,
    67  		ExtraExtensions:    cr.ExtraExtensions,
    68  	}
    69  	if err := policy.apply(tmpl, ca.Certificate.NotAfter); err != nil {
    70  		return nil, err
    71  	}
    72  
    73  	der, err := x509.CreateCertificate(rand.Reader, tmpl, ca.Certificate, cr.PublicKey, ca.PrivateKey)
    74  	if err != nil {
    75  		return nil, fmt.Errorf("failed to sign certificate: %v", err)
    76  	}
    77  	return der, nil
    78  }
    79
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