Go:如何向 x509.Certificate 添加扩展名 (subjectAltName)？

Question

我正在创建 CA 证书。我想添加带有一些值的 subjectAltName 扩展名，例如电子邮件或 crl 或公共(public)证书位置等。

package main

import (
    "crypto/rand"
    "crypto/rsa"
    "crypto/x509"
    "crypto/x509/pkix"
    "encoding/asn1"
    "encoding/pem"
    "fmt"
    "math/big"
    "os"
    "time"
    //"net"
    //"strconv"
)

func main() {
    template := x509.Certificate{}
    template.Subject = pkix.Name{
        Organization:  []string{"domain.tld", "My Name"},
        StreetAddress: []string{"Whatever. 123"},
        PostalCode:    []string{"12345"},
        Province:      []string{"Redneckville"},
        Locality:      []string{"Woods"},
        Country:       []string{"US"},
        CommonName:    "CA domain my name",
    }

    template.NotBefore = time.Now()
    template.NotAfter = template.NotBefore.Add(87658 * time.Hour)
    template.KeyUsage = x509.KeyUsageCertSign | x509.KeyUsageKeyEncipherment | x509.KeyUsageDigitalSignature | x509.KeyUsageCRLSign
    template.ExtKeyUsage = []x509.ExtKeyUsage{x509.ExtKeyUsageClientAuth, x509.ExtKeyUsageServerAuth}
    template.IsCA = true
    template.BasicConstraintsValid = true
    extSubjectAltName := pkix.Extension{}
    extSubjectAltName.Id = asn1.ObjectIdentifier{2, 5, 29, 17}
    extSubjectAltName.Critical = false
    var e error
    extSubjectAltName.Value, e = asn1.Marshal([]string{`email:mail@domain.tld`, `URI:http://ca.domain.tld/`})
    if e != nil {
        fmt.Println(e.Error())
        return
    }
    template.Extensions = []pkix.Extension{extSubjectAltName}

    priv, err := rsa.GenerateKey(rand.Reader, 4096)
    if err != nil {
        fmt.Println("Failed to generate private key:", err)
        os.Exit(1)
    }
    serialNumberLimit := new(big.Int).Lsh(big.NewInt(1), 128)
    template.SerialNumber, err = rand.Int(rand.Reader, serialNumberLimit)
    if err != nil {
        fmt.Println("Failed to generate serial number:", err)
        os.Exit(1)
    }
    derBytes, err := x509.CreateCertificate(rand.Reader, &template, &template, &priv.PublicKey, priv)
    if err != nil {
        fmt.Println("Failed to create certificate:", err)
        os.Exit(1)
    }
    certOut, err := os.Create("ca.crt")
    if err != nil {
        fmt.Println("Failed to open ca.pem for writing:", err)
        os.Exit(1)
    }
    pem.Encode(certOut, &pem.Block{Type: "CERTIFICATE", Bytes: derBytes})
    certOut.Close()
    keyOut, err := os.OpenFile("ca.key", os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0600)
    if err != nil {
        fmt.Println("failed to open ca.key for writing:", err)
        os.Exit(1)
    }
    pem.Encode(keyOut, &pem.Block{Type: "RSA PRIVATE KEY", Bytes: x509.MarshalPKCS1PrivateKey(priv)})
    keyOut.Close()
}

当我这样做时，结果是

X509v3 extensions:
    X509v3 Key Usage: critical
        Digital Signature, Key Encipherment, Certificate Sign, CRL Sign
    X509v3 Extended Key Usage: 
        TLS Web Client Authentication, TLS Web Server Authentication
    X509v3 Basic Constraints: critical
        CA:TRUE

所以，但我希望是这样的

    X509v3 Subject Alternative Name: 
        email:caoperator@disig.sk, URI:http://www.disig.sk/ca

如何添加具有这些值的扩展？

我也试过 Value: []byte(``email:my@email.com, URI:http://some.tld/uri``) < double "`"因为格式化

Answer 1

extSubjectAltName := pkix.Extension{}
extSubjectAltName.Id = asn1.ObjectIdentifier{2, 5, 29, 17}
extSubjectAltName.Critical = false
extSubjectAltName.Value = []byte(`email:my@mail.tld, URI:http://ca.dom.tld/`)
template.ExtraExtensions = []pkix.Extension{extSubjectAltName}

注意:template.ExtraExtensions 而不是 template.Extensions