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certgen.go
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certgen.go
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package tlsaudit
import (
"crypto/ecdsa"
"crypto/elliptic"
"crypto/rand"
"crypto/x509"
"crypto/x509/pkix"
"encoding/pem"
"math/big"
"os"
"path/filepath"
"time"
"github.com/mitchellh/go-homedir"
log "github.com/sirupsen/logrus"
)
var (
certsPath = ".tlsaudit/certs"
)
func init() {
home, err := homedir.Expand(filepath.FromSlash("~/.tlsaudit/certs"))
if err == nil {
certsPath = home
}
//create certificates directory if it doesn't exist
if _, err := os.Stat(certsPath); os.IsNotExist(err) {
if err2 := os.MkdirAll(certsPath, 0755); err2 != nil {
log.Errorln("Could not create the path ", certsPath)
}
}
}
func genRootCert() (x509.Certificate, *ecdsa.PrivateKey, error) {
notBefore := time.Now()
notAfter := notBefore.AddDate(10, 0, 0)
serialNo, err := rand.Int(rand.Reader, new(big.Int).Lsh(big.NewInt(1), 128))
key, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
_, err = saveKey("rootCAKey.key", key)
if err != nil {
return x509.Certificate{}, key, err
}
cert := x509.Certificate{
SerialNumber: serialNo,
NotBefore: notBefore,
NotAfter: notAfter,
IsCA: true,
BasicConstraintsValid: true,
KeyUsage: x509.KeyUsageCertSign,
ExtKeyUsage: []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},
Subject: pkix.Name{
Organization: []string{"TLS Audit Root"},
CommonName: "TLS Audit Root CA",
},
}
der, err := x509.CreateCertificate(rand.Reader, &cert, &cert, &key.PublicKey, key)
if err != nil {
return x509.Certificate{}, key, err
}
if _, err = saveCert("rootCACert.pem", der); err != nil {
return x509.Certificate{}, key, err
}
return cert, key, nil
}
func genCerts() (certFile, keyFile string, err error) {
//names of certificate and key files for the TLSAudit API service endpoint
suppliedCert := filepath.Join(certsPath, "tlsaudit.pem")
suppliedKey := filepath.Join(certsPath, "tlsaudit.key")
//if certificate and key are provided, attempt to use them, otherwise generate self-signed ones
if _, err := os.Stat(suppliedCert); !os.IsNotExist(err) {
if _, err := os.Stat(suppliedKey); !os.IsNotExist(err) {
return suppliedCert, suppliedKey, nil
}
}
rootCert, rootKey, err := genRootCert()
if err != nil {
return certFile, keyFile, err
}
key, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
if err != nil {
return certFile, keyFile, err
}
keyFile, err = saveKey("tlsaudit-self-signed.key", key)
if err != nil {
return certFile, keyFile, err
}
serialNo, err := rand.Int(rand.Reader, new(big.Int).Lsh(big.NewInt(1), 128))
if err != nil {
return certFile, keyFile, err
}
notBefore := time.Now()
notAfter := notBefore.AddDate(0, 6, 0)
cert := x509.Certificate{
SerialNumber: serialNo,
NotBefore: notBefore,
NotAfter: notAfter,
IsCA: false,
BasicConstraintsValid: true,
KeyUsage: x509.KeyUsageKeyEncipherment | x509.KeyUsageDigitalSignature,
ExtKeyUsage: []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},
Subject: pkix.Name{
Organization: []string{"TLS Audit organisation"},
CommonName: "TLS Audit Organisation certificate",
},
DNSNames: []string{"localhost"},
}
der, err := x509.CreateCertificate(rand.Reader, &cert, &rootCert, &key.PublicKey, rootKey)
if err != nil {
return certFile, keyFile, err
}
certFile, err = saveCert("tlsaudit-self-signed-cert.pem", der)
if err != nil {
return certFile, keyFile, err
}
return certFile, keyFile, nil
}
func saveKey(fileName string, key *ecdsa.PrivateKey) (string, error) {
fileName = filepath.Join(certsPath, fileName)
file, err := os.Create(fileName)
if err != nil {
return fileName, err
}
defer file.Close()
kb, err := x509.MarshalECPrivateKey(key)
if err != nil {
return fileName, err
}
if err = pem.Encode(file, &pem.Block{Type: "EC PRIVATE KEY", Bytes: kb}); err != nil {
return fileName, err
}
return fileName, nil
}
func saveCert(fileName string, der []byte) (string, error) {
fileName = filepath.Join(certsPath, fileName)
file, err := os.Create(fileName)
if err != nil {
return fileName, err
}
defer file.Close()
if err = pem.Encode(file, &pem.Block{Type: "CERTIFICATE", Bytes: der}); err != nil {
return fileName, err
}
return fileName, nil
}