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x509wrapper.go
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x509wrapper.go
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package x509wrapper
import (
"bytes"
"crypto/rand"
"crypto/rsa"
"crypto/x509"
"crypto/x509/pkix"
"encoding/pem"
"fmt"
"math/big"
"os"
"os/exec"
"path/filepath"
"regexp"
"strings"
"time"
)
const defaultCAname = "ca"
type X509CertWrapper struct {
Name string
Dir string
Cert *x509.Certificate
CertFile string
PrivateKey *rsa.PrivateKey
KeyFile string
FileName string
}
func NewCert(name string, dir string) *X509CertWrapper {
cert := &X509CertWrapper{
Name: defaultCAname,
Dir: "./",
}
defer cert.normalize()
if name != "" {
cert.Name = name
}
if dir != "" {
cert.Dir = dir
}
return cert
}
// Add a new certificate to X509CertWrapper srtuct
// and generate RSA private key with keyBits length
func (c *X509CertWrapper) AddCertAndKey(cert *x509.Certificate, keyBits int) error {
if c.ExistsAny() {
return fmt.Errorf(
"certificate '%s' already exists in directory '%s', consider to load it instead",
c.Name,
c.Dir,
)
}
privateKey, err := generateRSAKey(keyBits)
if err != nil {
return err
}
c.PrivateKey = privateKey
c.Cert = cert
return nil
}
// Check if either the certificate or the private key files exist
func (c *X509CertWrapper) ExistsAny() bool {
return fileExists(c.CertFile) || fileExists(c.KeyFile)
}
// Check if both the certificate and the private key files exist
func (c *X509CertWrapper) ExistsBoth() bool {
return fileExists(c.CertFile) && fileExists(c.KeyFile)
}
// Load certificate and private key from files
func (c *X509CertWrapper) Load() error {
certData, err := readDataFromFile(c.CertFile)
if err != nil {
return err
}
c.Cert, err = x509.ParseCertificate(certData)
if err != nil {
return fmt.Errorf(
"failed to parse certificate data from file [%s]: %w",
c.CertFile,
err,
)
}
privateKeyData, err := readDataFromFile(c.KeyFile)
if err != nil {
return err
}
c.PrivateKey, err = x509.ParsePKCS1PrivateKey(privateKeyData)
if err != nil {
return fmt.Errorf(
"failed to parse private key from file [%s]: %w",
c.KeyFile,
err,
)
}
return nil
}
// Save certificate and private key to PEM files
// Optionally, another certificate can be send as a parameter as a signer
func (c *X509CertWrapper) Save(signBy *X509CertWrapper) error {
if err := c.isReadyToSave(signBy); err != nil {
return err
}
if c.ExistsAny() {
return fmt.Errorf(
"certificate with name %s already exists in directory %s",
c.Name,
c.Dir,
)
}
if signBy == nil {
signBy = c
}
caBytes, err := x509.CreateCertificate(
rand.Reader,
c.Cert,
signBy.Cert,
&c.PrivateKey.PublicKey,
signBy.PrivateKey,
)
if err != nil {
return fmt.Errorf("failed to create CA certificate: %w", err)
}
// Save certificate
if err := writeDataToFile(c.CertFile, caBytes, "CERTIFICATE"); err != nil {
return err
}
// Save private key
if err := writeDataToFile(
c.KeyFile,
x509.MarshalPKCS1PrivateKey(c.PrivateKey),
"RSA PRIVATE KEY",
); err != nil {
os.Remove(c.CertFile)
return err
}
return nil
}
// Save certificate and private key to files in PKCS12 format
func (c *X509CertWrapper) SaveAsPKCS12(pass string) error {
if !c.ExistsBoth() {
return fmt.Errorf("certificate and private key files must exist before saving as PKCS12")
}
if _, err := exec.LookPath("openssl"); err != nil {
return fmt.Errorf("openssl is not installed")
}
if err := exec.Command(
"openssl",
"pkcs12",
"-export",
"-in", c.CertFile,
"-inkey", c.KeyFile,
"-out", filepath.Join(c.Dir, fmt.Sprintf("%s.pfx", c.FileName)),
"-password", fmt.Sprintf("pass:%s", pass),
).Run(); err != nil {
return err
}
return nil
}
func (c *X509CertWrapper) isReadyToSave(signBy *X509CertWrapper) error {
if signBy != nil {
if signBy.Cert == nil {
return fmt.Errorf("generate certificate before saving")
}
if signBy.PrivateKey == nil {
return fmt.Errorf("generate private key before saving")
}
if !signBy.ExistsBoth() {
return fmt.Errorf("need to save cert files before signing")
}
}
if c.Cert == nil {
return fmt.Errorf("need to generate certificate before saving")
}
if c.PrivateKey == nil {
return fmt.Errorf("need to generate private key before saving")
}
return nil
}
// Fill X509CertWrapper with correct data after creation
func (c *X509CertWrapper) normalize() {
absDir, err := filepath.Abs(c.Dir)
if err != nil {
panic(err)
}
c.FileName = normalizeName(c.Name)
c.Dir = absDir
c.Name = strings.Trim(c.Name, " ")
c.CertFile = filepath.Join(c.Dir, fmt.Sprintf("%s.crt", c.FileName))
c.KeyFile = filepath.Join(c.Dir, fmt.Sprintf("%s.key", c.FileName))
}
// Return CA certificate
func PrepareCA(subj pkix.Name, notBefore time.Time, notAfter time.Time) *x509.Certificate {
return &x509.Certificate{
SerialNumber: createSerialNumber(),
Subject: subj,
NotBefore: notBefore,
NotAfter: notAfter,
IsCA: true,
ExtKeyUsage: []x509.ExtKeyUsage{x509.ExtKeyUsageClientAuth, x509.ExtKeyUsageServerAuth},
KeyUsage: x509.KeyUsageDigitalSignature | x509.KeyUsageCertSign,
BasicConstraintsValid: true,
}
}
// Return X509 certificate for server or clients
// This certificate must be signed by CA certificate
func PrepareCert(subj pkix.Name, dns []string, notBefore time.Time, notAfter time.Time) *x509.Certificate {
return &x509.Certificate{
SerialNumber: createSerialNumber(),
Subject: subj,
DNSNames: dns,
NotBefore: notBefore,
NotAfter: notAfter,
SubjectKeyId: []byte{1, 2, 3, 4, 6},
ExtKeyUsage: []x509.ExtKeyUsage{x509.ExtKeyUsageClientAuth, x509.ExtKeyUsageServerAuth},
KeyUsage: x509.KeyUsageDigitalSignature,
}
}
// Return cerial number for certificate based on current timestamp
func createSerialNumber() *big.Int {
return big.NewInt(time.Now().UnixMicro())
}
// Check if file exists by its path
func fileExists(filePath string) bool {
_, err := os.Stat(filePath)
return err == nil || !os.IsNotExist(err)
}
// Generate RSA key pair of the given bit size
func generateRSAKey(bitSize int) (*rsa.PrivateKey, error) {
privateKey, err := rsa.GenerateKey(rand.Reader, bitSize)
if err != nil {
return nil, fmt.Errorf("failed to generate RSA private key: %w", err)
}
return privateKey, nil
}
// Prepare certificate file name from certificate name
func normalizeName(name string) string {
re := regexp.MustCompile(`\W+`)
res := re.ReplaceAll([]byte(name), []byte("-"))
re = regexp.MustCompile(`\-{2,}`)
res = re.ReplaceAll(res, []byte("-"))
return strings.ToLower(strings.Trim(string(res), "-"))
}
// Read data from key file and decode
func readDataFromFile(filePath string) ([]byte, error) {
data, err := os.ReadFile(filePath)
if err != nil {
return nil, fmt.Errorf("failed to read file : %w", err)
}
pemBlock, _ := pem.Decode(data)
if pemBlock == nil {
return nil, fmt.Errorf("failed to parse certificate PEM from file [%s]: %w", filePath, err)
}
return pemBlock.Bytes, nil
}
// Write key data to file
func writeDataToFile(absFilePath string, data []byte, pemType string) error {
if _, err := os.Stat(absFilePath); os.IsExist(err) {
return fmt.Errorf("file with name [%s] alredy exists", absFilePath)
}
if pemType != "" {
pemData := new(bytes.Buffer)
err := pem.Encode(pemData, &pem.Block{Type: pemType, Bytes: data})
if err != nil {
return fmt.Errorf("failed to encode PEM: %w", err)
}
data = pemData.Bytes()
}
if err := os.MkdirAll(filepath.Dir(absFilePath), 0700); err != nil {
return err
}
if err := os.WriteFile(absFilePath, data, 0600); err != nil {
return fmt.Errorf("failed to write certificate file: %w", err)
}
return nil
}