Created
September 8, 2021 20:17
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Generate a self-signed certificate in Go
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package main | |
import ( | |
"bytes" | |
"crypto/ecdsa" | |
"crypto/elliptic" | |
"crypto/rand" | |
"crypto/rsa" | |
"crypto/x509" | |
"crypto/x509/pkix" | |
"encoding/pem" | |
"fmt" | |
"log" | |
"math/big" | |
"os" | |
"time" | |
) | |
func publicKey(priv interface{}) interface{} { | |
switch k := priv.(type) { | |
case *rsa.PrivateKey: | |
return &k.PublicKey | |
case *ecdsa.PrivateKey: | |
return &k.PublicKey | |
default: | |
return nil | |
} | |
} | |
func pemBlockForKey(priv interface{}) *pem.Block { | |
switch k := priv.(type) { | |
case *rsa.PrivateKey: | |
return &pem.Block{Type: "RSA PRIVATE KEY", Bytes: x509.MarshalPKCS1PrivateKey(k)} | |
case *ecdsa.PrivateKey: | |
b, err := x509.MarshalECPrivateKey(k) | |
if err != nil { | |
fmt.Fprintf(os.Stderr, "Unable to marshal ECDSA private key: %v", err) | |
os.Exit(2) | |
} | |
return &pem.Block{Type: "EC PRIVATE KEY", Bytes: b} | |
default: | |
return nil | |
} | |
} | |
func main() { | |
// priv, err := rsa.GenerateKey(rand.Reader, *rsaBits) | |
priv, err := ecdsa.GenerateKey(elliptic.P521(), rand.Reader) | |
if err != nil { | |
log.Fatal(err) | |
} | |
template := x509.Certificate{ | |
SerialNumber: big.NewInt(1), | |
Subject: pkix.Name{ | |
Organization: []string{"Acme Co"}, | |
}, | |
NotBefore: time.Now(), | |
NotAfter: time.Now().Add(time.Hour * 24 * 180), | |
KeyUsage: x509.KeyUsageKeyEncipherment | x509.KeyUsageDigitalSignature, | |
ExtKeyUsage: []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth}, | |
BasicConstraintsValid: true, | |
} | |
/* | |
hosts := strings.Split(*host, ",") | |
for _, h := range hosts { | |
if ip := net.ParseIP(h); ip != nil { | |
template.IPAddresses = append(template.IPAddresses, ip) | |
} else { | |
template.DNSNames = append(template.DNSNames, h) | |
} | |
} | |
if *isCA { | |
template.IsCA = true | |
template.KeyUsage |= x509.KeyUsageCertSign | |
} | |
*/ | |
derBytes, err := x509.CreateCertificate(rand.Reader, &template, &template, publicKey(priv), priv) | |
if err != nil { | |
log.Fatalf("Failed to create certificate: %s", err) | |
} | |
out := &bytes.Buffer{} | |
pem.Encode(out, &pem.Block{Type: "CERTIFICATE", Bytes: derBytes}) | |
fmt.Println(out.String()) | |
out.Reset() | |
pem.Encode(out, pemBlockForKey(priv)) | |
fmt.Println(out.String()) | |
} |
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