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generate_cert.go
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generate_cert.go
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// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Generate a self-signed X.509 certificate for a TLS server. Outputs to
// 'cert.pem' and 'key.pem' and will overwrite existing files.
// Based on src/crypto/tls/generate_cert.go from the Go SDK
// Modified by the Gopcua Authors for use in creating an OPC-UA compliant client certificate
package opcua_plugin
import (
"crypto/ecdsa"
"crypto/rand"
"crypto/rsa"
"crypto/x509"
"crypto/x509/pkix"
"encoding/pem"
"fmt"
"math/big"
"net"
"net/url"
"os"
"strings"
"time"
)
func GenerateCert(host string, rsaBits int, validFor time.Duration) (certPEM, keyPEM []byte, err error) {
if len(host) == 0 {
return nil, nil, fmt.Errorf("missing required host parameter")
}
if rsaBits == 0 {
rsaBits = 2048
}
priv, err := rsa.GenerateKey(rand.Reader, rsaBits)
if err != nil {
return nil, nil, fmt.Errorf("failed to generate private key: %s", err)
}
notBefore := time.Now()
notAfter := notBefore.Add(validFor)
serialNumberLimit := new(big.Int).Lsh(big.NewInt(1), 128)
serialNumber, err := rand.Int(rand.Reader, serialNumberLimit)
if err != nil {
return nil, nil, fmt.Errorf("failed to generate serial number: %s", err)
}
template := x509.Certificate{
SerialNumber: serialNumber,
Subject: pkix.Name{
CommonName: "benthos-umh",
Organization: []string{"UMH"},
},
NotBefore: notBefore,
NotAfter: notAfter,
KeyUsage: x509.KeyUsageContentCommitment | x509.KeyUsageKeyEncipherment | x509.KeyUsageDigitalSignature | x509.KeyUsageDataEncipherment | x509.KeyUsageCertSign,
ExtKeyUsage: []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth, x509.ExtKeyUsageClientAuth},
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 uri, err := url.Parse(h); err == nil {
template.URIs = append(template.URIs, uri)
}
}
derBytes, err := x509.CreateCertificate(rand.Reader, &template, &template, publicKey(priv), priv)
if err != nil {
return nil, nil, fmt.Errorf("failed to create certificate: %s", err)
}
return pem.EncodeToMemory(&pem.Block{Type: "CERTIFICATE", Bytes: derBytes}), pem.EncodeToMemory(pemBlockForKey(priv)), nil
}
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
}
}