csr.go

Documentation: k8s.io/client-go/util/cert

     1  /*
     2  Copyright 2016 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 cert
    18  
    19  import (
    20  	cryptorand "crypto/rand"
    21  	"crypto/rsa"
    22  	"crypto/x509"
    23  	"crypto/x509/pkix"
    24  	"encoding/pem"
    25  	"net"
    26  )
    27  
    28  // MakeCSR generates a PEM-encoded CSR using the supplied private key, subject, and SANs.
    29  // All key types that are implemented via crypto.Signer are supported (This includes *rsa.PrivateKey and *ecdsa.PrivateKey.)
    30  func MakeCSR(privateKey interface{}, subject *pkix.Name, dnsSANs []string, ipSANs []net.IP) (csr []byte, err error) {
    31  	template := &x509.CertificateRequest{
    32  		Subject:     *subject,
    33  		DNSNames:    dnsSANs,
    34  		IPAddresses: ipSANs,
    35  	}
    36  
    37  	return MakeCSRFromTemplate(privateKey, template)
    38  }
    39  
    40  // MakeCSRFromTemplate generates a PEM-encoded CSR using the supplied private
    41  // key and certificate request as a template. All key types that are
    42  // implemented via crypto.Signer are supported (This includes *rsa.PrivateKey
    43  // and *ecdsa.PrivateKey.)
    44  func MakeCSRFromTemplate(privateKey interface{}, template *x509.CertificateRequest) ([]byte, error) {
    45  	t := *template
    46  	t.SignatureAlgorithm = sigType(privateKey)
    47  
    48  	csrDER, err := x509.CreateCertificateRequest(cryptorand.Reader, &t, privateKey)
    49  	if err != nil {
    50  		return nil, err
    51  	}
    52  
    53  	csrPemBlock := &pem.Block{
    54  		Type:  CertificateRequestBlockType,
    55  		Bytes: csrDER,
    56  	}
    57  
    58  	return pem.EncodeToMemory(csrPemBlock), nil
    59  }
    60  
    61  func sigType(privateKey interface{}) x509.SignatureAlgorithm {
    62  	// Customize the signature for RSA keys, depending on the key size
    63  	if privateKey, ok := privateKey.(*rsa.PrivateKey); ok {
    64  		keySize := privateKey.N.BitLen()
    65  		switch {
    66  		case keySize >= 4096:
    67  			return x509.SHA512WithRSA
    68  		case keySize >= 3072:
    69  			return x509.SHA384WithRSA
    70  		default:
    71  			return x509.SHA256WithRSA
    72  		}
    73  	}
    74  	return x509.UnknownSignatureAlgorithm
    75  }
    76
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