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gencerts.go
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gencerts.go
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package main
import (
"bytes"
"crypto"
"crypto/ecdsa"
"crypto/elliptic"
"crypto/rand"
"crypto/x509"
"crypto/x509/pkix"
"encoding/pem"
"fmt"
"math/big"
"os"
"path/filepath"
"time"
)
func main() {
if len(os.Args) < 3 {
fmt.Fprintln(os.Stderr, "usage: gencerts SERVERDIR AGENTDIR [AGENTDIR...]")
os.Exit(1)
}
notAfter := time.Now().Add(time.Hour)
caKey := generateKey()
caCert := createRootCertificate(caKey, &x509.Certificate{
SerialNumber: big.NewInt(1),
BasicConstraintsValid: true,
IsCA: true,
NotAfter: notAfter,
Subject: pkix.Name{CommonName: "Agent CA"},
})
writeCerts(filepath.Join(os.Args[1], "agent-cacert.pem"), caCert)
for i, dir := range os.Args[2:] {
agentKey := generateKey()
agentCert := createCertificate(agentKey, &x509.Certificate{
SerialNumber: big.NewInt(int64(i)),
KeyUsage: x509.KeyUsageDigitalSignature,
NotAfter: notAfter,
Subject: pkix.Name{CommonName: filepath.Base(dir)},
}, caKey, caCert)
writeKey(filepath.Join(dir, "agent.key.pem"), agentKey)
writeCerts(filepath.Join(dir, "agent.crt.pem"), agentCert)
}
}
func createRootCertificate(key crypto.Signer, tmpl *x509.Certificate) *x509.Certificate {
return createCertificate(key, tmpl, key, tmpl)
}
func createCertificate(key crypto.Signer, tmpl *x509.Certificate, parentKey crypto.Signer, parent *x509.Certificate) *x509.Certificate {
certDER, err := x509.CreateCertificate(rand.Reader, tmpl, parent, key.Public(), parentKey)
checkErr(err)
cert, err := x509.ParseCertificate(certDER)
checkErr(err)
return cert
}
func generateKey() crypto.Signer {
key, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
checkErr(err)
return key
}
func writeKey(path string, key crypto.Signer) {
keyBytes, err := x509.MarshalPKCS8PrivateKey(key)
checkErr(err)
pemBytes := pem.EncodeToMemory(&pem.Block{
Type: "PRIVATE KEY",
Bytes: keyBytes,
})
writeFile(path, pemBytes, 0o600)
}
func writeCerts(path string, certs ...*x509.Certificate) {
data := new(bytes.Buffer)
for _, cert := range certs {
err := pem.Encode(data, &pem.Block{
Type: "CERTIFICATE",
Bytes: cert.Raw,
})
checkErr(err)
}
writeFile(path, data.Bytes(), 0o644)
}
func writeFile(path string, data []byte, mode os.FileMode) {
err := os.WriteFile(path, data, mode)
checkErr(err)
}
func checkErr(err error) {
if err != nil {
panic(err)
}
}