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zts-svccert.go
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zts-svccert.go
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package main
import (
"bytes"
"crypto"
"crypto/rand"
"crypto/tls"
"crypto/x509"
"crypto/x509/pkix"
"encoding/pem"
"flag"
"fmt"
"io/ioutil"
"log"
"net/http"
"strings"
"time"
"github.com/yahoo/athenz/clients/go/zts"
"github.com/yahoo/athenz/libs/go/zmssvctoken"
)
type signer struct {
key crypto.Signer
algorithm x509.SignatureAlgorithm
}
func main() {
var ztsURL, serviceKey, serviceCert, domain, service, keyID string
var caCertFile, certFile, signerCertFile, dnsDomain, hdr string
var csr bool
flag.BoolVar(&csr, "csr", false, "request csr only")
flag.StringVar(&certFile, "cert-file", "", "output certificate file")
flag.StringVar(&signerCertFile, "signer-cert-file", "", "output signer certificate file")
flag.StringVar(&caCertFile, "cacert", "", "CA certificate file")
flag.StringVar(&serviceKey, "private-key", "", "private key file")
flag.StringVar(&serviceCert, "service-cert", "", "service certificate file")
flag.StringVar(&domain, "domain", "", "domain of service")
flag.StringVar(&service, "service", "", "name of service")
flag.StringVar(&keyID, "key-version", "", "key version")
flag.StringVar(&ztsURL, "zts", "", "url of the ZTS Service")
flag.StringVar(&dnsDomain, "dns-domain", "", "dns domain suffix to be included in the csr")
flag.StringVar(&hdr, "hdr", "Athenz-Principal-Auth", "Header name")
flag.Parse()
if serviceKey == "" || domain == "" || service == "" ||
keyID == "" || dnsDomain == "" {
fmt.Println("Error: missing required attributes")
usage()
}
// load private key
keyBytes, err := ioutil.ReadFile(serviceKey)
if err != nil {
log.Fatalln(err)
}
// get our private key signer for csr
pkSigner, err := newSigner(keyBytes)
if err != nil {
log.Fatalln(err)
}
// generate a csr for this service
hyphenDomain := strings.Replace(domain, ".", "-", -1)
host := fmt.Sprintf("%s.%s.%s", service, hyphenDomain, dnsDomain)
commonName := fmt.Sprintf("%s.%s", domain, service)
csrData, err := generateCSR(pkSigner, commonName, host)
if err != nil {
log.Fatalln(err)
}
// if we're provided the csr flag then we're going to display
// it and return right away
if csr {
fmt.Println(csrData)
return
}
// for all other operations we need to have ZTS Server url
if ztsURL == "" {
fmt.Println("Error: missing ZTS Server url")
usage()
}
// if we're given a certficate then we'll use that otherwise
// we're going to generate a ntoken for our request
var client *zts.ZTSClient
if serviceCert == "" {
client, err = ntokenClient(ztsURL, domain, service, keyID, caCertFile, hdr, keyBytes)
} else {
client, err = certClient(ztsURL, keyBytes, serviceCert, caCertFile)
}
if err != nil {
log.Fatalln(err)
}
req := &zts.InstanceRefreshRequest{Csr: csrData, KeyId: keyID}
// request a tls certificate for this service
identity, err := client.PostInstanceRefreshRequest(zts.CompoundName(domain), zts.SimpleName(service), req)
if err != nil {
log.Fatalln(err)
}
if certFile != "" {
err = ioutil.WriteFile(certFile, []byte(identity.Certificate), 0444)
if err != nil {
log.Fatalln(err)
}
} else {
fmt.Println(identity.Certificate)
}
if signerCertFile != "" {
err = ioutil.WriteFile(signerCertFile, []byte(identity.CaCertBundle), 0444)
if err != nil {
log.Fatalln(err)
}
}
}
func usage() {
log.Fatalln("usage: zts-svccert [-csr] -domain <domain> -service <service> -private-key <key-file> -key-version <version> -zts <zts-server-url> -dns-domain <dns-domain> [-cert-file <output-cert-file>] [-signer-cert-file <output-signer-file>] [-cacert <ca-certificate-file>] [-hdr <auth-header-name>]")
}
func newSigner(privateKeyPEM []byte) (*signer, error) {
block, _ := pem.Decode(privateKeyPEM)
if block == nil {
return nil, fmt.Errorf("Unable to load private key")
}
switch block.Type {
case "EC PRIVATE KEY":
key, err := x509.ParseECPrivateKey(block.Bytes)
if err != nil {
return nil, err
}
return &signer{key: key, algorithm: x509.ECDSAWithSHA256}, nil
case "RSA PRIVATE KEY":
key, err := x509.ParsePKCS1PrivateKey(block.Bytes)
if err != nil {
return nil, err
}
return &signer{key: key, algorithm: x509.SHA256WithRSA}, nil
default:
return nil, fmt.Errorf("Unsupported private key type: %s", block.Type)
}
}
func generateCSR(keySigner *signer, commonName, host string) (string, error) {
// note: RFC 6125 states that if the SAN (Subject Alternative Name) exists,
// it is used, not the CA. So, we will always put the Athenz name in the CN
// (it is *not* a DNS domain name), and put the host name into the SAN.
subj := pkix.Name{CommonName: commonName}
subj.OrganizationalUnit = []string{"Athenz"}
subj.Country = []string{"US"}
subj.Organization = []string{"Oath Inc."}
template := x509.CertificateRequest{
Subject: subj,
SignatureAlgorithm: keySigner.algorithm,
}
if host != "" {
template.DNSNames = []string{host}
}
csr, err := x509.CreateCertificateRequest(rand.Reader, &template, keySigner.key)
if err != nil {
return "", fmt.Errorf("Cannot create CSR: %v", err)
}
block := &pem.Block{
Type: "CERTIFICATE REQUEST",
Bytes: csr,
}
var buf bytes.Buffer
err = pem.Encode(&buf, block)
if err != nil {
return "", fmt.Errorf("Cannot encode CSR to PEM: %v", err)
}
return buf.String(), nil
}
func ntokenClient(ztsURL, domain, service, keyID, caCertFile, hdr string, keyBytes []byte) (*zts.ZTSClient, error) {
// get token builder instance
builder, err := zmssvctoken.NewTokenBuilder(domain, service, keyBytes, keyID)
if err != nil {
return nil, err
}
// set optional attributes
builder.SetExpiration(10 * time.Minute)
// get a token instance that always gives you unexpired tokens values
// safe for concurrent use
tok := builder.Token()
// get a token for use
ntoken, err := tok.Value()
if err != nil {
return nil, err
}
transport := &http.Transport{
ResponseHeaderTimeout: 30 * time.Second,
}
if caCertFile != "" {
config := &tls.Config{}
certPool := x509.NewCertPool()
caCert, err := ioutil.ReadFile(caCertFile)
if err != nil {
return nil, err
}
certPool.AppendCertsFromPEM(caCert)
config.RootCAs = certPool
transport.TLSClientConfig = config
}
// use the ntoken to talk to Athenz
client := zts.NewClient(ztsURL, transport)
client.AddCredentials(hdr, ntoken)
return &client, nil
}
func certClient(ztsURL string, keyBytes []byte, certfile, caCertFile string) (*zts.ZTSClient, error) {
certpem, err := ioutil.ReadFile(certfile)
if err != nil {
return nil, err
}
var cacertpem []byte
if caCertFile != "" {
cacertpem, err = ioutil.ReadFile(caCertFile)
if err != nil {
return nil, err
}
}
config, err := tlsConfiguration(keyBytes, certpem, cacertpem)
if err != nil {
return nil, err
}
transport := &http.Transport{
TLSClientConfig: config,
}
client := zts.NewClient(ztsURL, transport)
return &client, nil
}
func tlsConfiguration(keypem, certpem, cacertpem []byte) (*tls.Config, error) {
config := &tls.Config{}
if certpem != nil && keypem != nil {
mycert, err := tls.X509KeyPair(certpem, keypem)
if err != nil {
return nil, err
}
config.Certificates = make([]tls.Certificate, 1)
config.Certificates[0] = mycert
}
if cacertpem != nil {
certPool := x509.NewCertPool()
certPool.AppendCertsFromPEM(cacertpem)
config.RootCAs = certPool
}
return config, nil
}