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// Copyright (c) 2019, Grégoire Duchêne <gduchene@awhk.org>
//
// Use of this source code is governed by the ISC license that can be
// found in the LICENSE file.
package main
import (
"crypto/ecdsa"
"crypto/elliptic"
"crypto/rand"
"crypto/x509"
"crypto/x509/pkix"
"encoding/pem"
"errors"
"flag"
"fmt"
"io/ioutil"
"log"
"math/big"
"net"
"os"
"time"
)
type IPListFlag []net.IP
func (f *IPListFlag) String() string {
var l []net.IP = *f
return fmt.Sprintf("%s", l)
}
func (f *IPListFlag) Set(s string) error {
ip := net.ParseIP(s)
if ip == nil {
return errors.New("could not parse IP")
}
*f = append(*f, ip)
return nil
}
type StringListFlag []string
func (f *StringListFlag) String() string {
var l []string = *f
return fmt.Sprintf("%s", l)
}
func (f *StringListFlag) Set(s string) error {
*f = append(*f, s)
return nil
}
type TimeFlag struct {
t time.Time
}
func (f *TimeFlag) String() string {
return f.t.String()
}
func (f *TimeFlag) Set(s string) (err error) {
f.t, err = time.Parse(time.RFC3339, s)
return
}
var (
caName = flag.String("ca", "", "base name for the CA files")
commonName = flag.String("cn", "", "common name")
country = flag.String("c", "", "country code")
dnsNames StringListFlag
duration = flag.Duration("d", 0, "certificate duration")
from TimeFlag
ips IPListFlag
org StringListFlag
out = flag.String("out", "", "base name for the output")
unit StringListFlag
until TimeFlag
)
func init() {
flag.Var(&dnsNames, "dns", "DNS name")
flag.Var(&from, "start-date", "certificate start date")
flag.Var(&ips, "ip", "IP address")
flag.Var(&org, "o", "organization")
flag.Var(&unit, "ou", "organization unit")
flag.Var(&until, "end-date", "certificate end date")
}
func newSerial() *big.Int {
// Bound the number generation so the serial number does not take
// up more than 20 octets. See Section 4.1.2.2 of RFC 5280 for more
// details (https://tools.ietf.org/html/rfc5280#section-4.1.2.2).
max := big.NewInt(2)
max = max.Lsh(max, 159)
max = max.Sub(max, big.NewInt(1))
x, err := rand.Int(rand.Reader, max)
if err != nil {
panic(err)
}
// We generated a random number between between [0, 2^160 - 1), so we
// increment the result to get a serial number between [1, 2^160) as
// serial numbers must be positive non-zero integers. See Erratum 3200
// for more details (https://www.rfc-editor.org/errata/eid3200).
return x.Add(x, big.NewInt(1))
}
func main() {
flag.Parse()
log.SetFlags(0)
if *commonName == "" {
log.Fatalln("error: -cn is required")
}
if *country == "" {
log.Fatalln("error: -c is required")
}
if from.t.IsZero() {
from.t = time.Now()
}
if *out == "" {
log.Fatalln("error: -out is required")
}
if len(org) == 0 {
log.Fatalln("error: -o is required")
}
if until.t.IsZero() {
if *duration == 0 {
log.Fatalln("error: -end-date is required when no -d is passed")
}
until.t = from.t.Add(*duration)
} else if *duration != 0 {
log.Println("warning: ignored -d as -end-date was passed")
}
if until.t.Before(from.t) {
log.Fatalln("error: end date is before the start date")
}
key, err := ecdsa.GenerateKey(elliptic.P384(), rand.Reader)
if err != nil {
log.Fatalln("error: could not generate the certificate key:", err)
}
var (
keyUsage x509.KeyUsage
extKeyUsage []x509.ExtKeyUsage
)
if *caName == "" {
keyUsage = x509.KeyUsageCertSign
} else {
keyUsage = x509.KeyUsageDigitalSignature
extKeyUsage = append(extKeyUsage, x509.ExtKeyUsageServerAuth)
}
tmpl := &x509.Certificate{
BasicConstraintsValid: *caName == "",
DNSNames: dnsNames,
ExtKeyUsage: extKeyUsage,
IPAddresses: ips,
IsCA: *caName == "",
KeyUsage: keyUsage,
NotBefore: from.t,
NotAfter: until.t,
SerialNumber: newSerial(),
Subject: pkix.Name{
CommonName: *commonName,
Country: []string{*country},
Organization: org,
OrganizationalUnit: unit,
},
}
parentKey := key
parentCert := tmpl
if *caName != "" {
buf, err := ioutil.ReadFile(fmt.Sprintf("%s.key", *caName))
if err != nil {
log.Fatalln("error: could not read the CA private key:", err)
}
block, _ := pem.Decode(buf)
parentKey, err = x509.ParseECPrivateKey(block.Bytes)
if err != nil {
log.Fatalln("error: could not parse the CA private key:", err)
}
buf, err = ioutil.ReadFile(fmt.Sprintf("%s.crt", *caName))
if err != nil {
log.Fatalln("error: could not read the CA certificate:", err)
}
block, _ = pem.Decode(buf)
parentCert, err = x509.ParseCertificate(block.Bytes)
if err != nil {
log.Fatalln("error: could not parse the CA certificate:", err)
}
}
cert, err := x509.CreateCertificate(rand.Reader, tmpl, parentCert, &key.PublicKey, parentKey)
if err != nil {
log.Fatalln("error: could not generate the certificate:", err)
}
keyOut, err := os.OpenFile(fmt.Sprintf("%s.key", *out), os.O_CREATE|os.O_EXCL|os.O_WRONLY, 0600)
if err != nil {
log.Fatalln("error: could not create the private key:", err)
}
defer keyOut.Close()
certOut, err := os.OpenFile(fmt.Sprintf("%s.crt", *out), os.O_CREATE|os.O_EXCL|os.O_WRONLY, 0644)
if err != nil {
log.Fatalln("error: could not create the certificate:", err)
}
defer certOut.Close()
keyBytes, err := x509.MarshalECPrivateKey(key)
if err != nil {
log.Fatalln("error: could not serialize the private key:", err)
}
if err := pem.Encode(keyOut, &pem.Block{
Type: "EC PRIVATE KEY",
Bytes: keyBytes,
}); err != nil {
log.Fatalln("error: could not encode the private key:", err)
}
if err := pem.Encode(certOut, &pem.Block{
Type: "CERTIFICATE",
Bytes: cert,
}); err != nil {
log.Fatalln("error: could not encode the certificate:", err)
}
}
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