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main.go
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main.go
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package main
import (
"context"
"crypto"
"crypto/ecdsa"
"crypto/elliptic"
"crypto/rand"
"crypto/sha1"
"crypto/x509"
"crypto/x509/pkix"
"encoding/hex"
"encoding/pem"
"flag"
"fmt"
"math/big"
"os"
"time"
"github.com/pkg/errors"
"github.com/smallstep/certificates/kms"
"github.com/smallstep/certificates/kms/apiv1"
"go.step.sm/cli-utils/fileutil"
"go.step.sm/cli-utils/ui"
"go.step.sm/crypto/pemutil"
// Enable yubikey.
_ "github.com/smallstep/certificates/kms/yubikey"
)
// Config is a mapping of the cli flags.
type Config struct {
RootOnly bool
RootSlot string
CrtSlot string
RootFile string
KeyFile string
Pin string
ManagementKey string
Force bool
}
// Validate checks the flags in the config.
func (c *Config) Validate() error {
switch {
case c.ManagementKey != "" && len(c.ManagementKey) != 48:
return errors.New("flag `--management-key` must be 48 hexadecimal characters (24 bytes)")
case c.RootFile != "" && c.KeyFile == "":
return errors.New("flag `--root` requires flag `--key`")
case c.KeyFile != "" && c.RootFile == "":
return errors.New("flag `--key` requires flag `--root`")
case c.RootOnly && c.RootFile != "":
return errors.New("flag `--root-only` is incompatible with flag `--root`")
case c.RootSlot == c.CrtSlot:
return errors.New("flag `--root-slot` and flag `--crt-slot` cannot be the same")
case c.RootFile == "" && c.RootSlot == "":
return errors.New("one of flag `--root` or `--root-slot` is required")
default:
if c.RootFile != "" {
c.RootSlot = ""
}
if c.RootOnly {
c.CrtSlot = ""
}
if c.ManagementKey != "" {
if _, err := hex.DecodeString(c.ManagementKey); err != nil {
return errors.Wrap(err, "flag `--management-key` is not valid")
}
}
return nil
}
}
func main() {
var c Config
flag.StringVar(&c.ManagementKey, "management-key", "", `Management key to use in hexadecimal format. (default "010203040506070801020304050607080102030405060708")`)
flag.BoolVar(&c.RootOnly, "root-only", false, "Slot only the root certificate and sign and intermediate.")
flag.StringVar(&c.RootSlot, "root-slot", "9a", "Slot to store the root certificate.")
flag.StringVar(&c.CrtSlot, "crt-slot", "9c", "Slot to store the intermediate certificate.")
flag.StringVar(&c.RootFile, "root", "", "Path to the root certificate to use.")
flag.StringVar(&c.KeyFile, "key", "", "Path to the root key to use.")
flag.BoolVar(&c.Force, "force", false, "Force the delete of previous keys.")
flag.Usage = usage
flag.Parse()
if err := c.Validate(); err != nil {
fatal(err)
}
pin, err := ui.PromptPassword("What is the YubiKey PIN?")
if err != nil {
fatal(err)
}
c.Pin = string(pin)
k, err := kms.New(context.Background(), apiv1.Options{
Type: string(apiv1.YubiKey),
Pin: c.Pin,
ManagementKey: c.ManagementKey,
})
if err != nil {
fatal(err)
}
// Check if the slots are empty, fail if they are not
if !c.Force {
switch {
case c.RootSlot != "":
checkSlot(k, c.RootSlot)
case c.CrtSlot != "":
checkSlot(k, c.CrtSlot)
}
}
if err := createPKI(k, c); err != nil {
fatal(err)
}
defer func() {
_ = k.Close()
}()
}
func fatal(err error) {
if os.Getenv("STEPDEBUG") == "1" {
fmt.Fprintf(os.Stderr, "%+v\n", err)
} else {
fmt.Fprintln(os.Stderr, err)
}
os.Exit(1)
}
func usage() {
fmt.Fprintln(os.Stderr, "Usage: step-yubikey-init")
fmt.Fprintln(os.Stderr, `
The step-yubikey-init command initializes a public key infrastructure (PKI)
to be used by step-ca.
This tool is experimental and in the future it will be integrated in step cli.
OPTIONS`)
fmt.Fprintln(os.Stderr)
flag.PrintDefaults()
fmt.Fprintln(os.Stderr, `
COPYRIGHT
(c) 2018-2020 Smallstep Labs, Inc.`)
os.Exit(1)
}
func checkSlot(k kms.KeyManager, slot string) {
if _, err := k.GetPublicKey(&apiv1.GetPublicKeyRequest{
Name: slot,
}); err == nil {
fmt.Fprintf(os.Stderr, "⚠️ Your YubiKey already has a key in the slot %s.\n", slot)
fmt.Fprintln(os.Stderr, " If you want to delete it and start fresh, use `--force`.")
os.Exit(1)
}
}
func createPKI(k kms.KeyManager, c Config) error {
var err error
ui.Println("Creating PKI ...")
now := time.Now()
// Root Certificate
var signer crypto.Signer
var root *x509.Certificate
if c.RootFile != "" && c.KeyFile != "" {
root, err = pemutil.ReadCertificate(c.RootFile)
if err != nil {
return err
}
key, err := pemutil.Read(c.KeyFile)
if err != nil {
return err
}
var ok bool
if signer, ok = key.(crypto.Signer); !ok {
return errors.Errorf("key type '%T' does not implement a signer", key)
}
} else {
resp, err := k.CreateKey(&apiv1.CreateKeyRequest{
Name: c.RootSlot,
SignatureAlgorithm: apiv1.ECDSAWithSHA256,
})
if err != nil {
return err
}
signer, err = k.CreateSigner(&resp.CreateSignerRequest)
if err != nil {
return err
}
template := &x509.Certificate{
IsCA: true,
NotBefore: now,
NotAfter: now.Add(time.Hour * 24 * 365 * 10),
KeyUsage: x509.KeyUsageCertSign | x509.KeyUsageCRLSign,
BasicConstraintsValid: true,
MaxPathLen: 1,
MaxPathLenZero: false,
Issuer: pkix.Name{CommonName: "YubiKey Smallstep Root"},
Subject: pkix.Name{CommonName: "YubiKey Smallstep Root"},
SerialNumber: mustSerialNumber(),
SubjectKeyId: mustSubjectKeyID(resp.PublicKey),
AuthorityKeyId: mustSubjectKeyID(resp.PublicKey),
}
b, err := x509.CreateCertificate(rand.Reader, template, template, resp.PublicKey, signer)
if err != nil {
return err
}
root, err = x509.ParseCertificate(b)
if err != nil {
return errors.Wrap(err, "error parsing root certificate")
}
if cm, ok := k.(kms.CertificateManager); ok {
if err = cm.StoreCertificate(&apiv1.StoreCertificateRequest{
Name: c.RootSlot,
Certificate: root,
}); err != nil {
return err
}
}
if err = fileutil.WriteFile("root_ca.crt", pem.EncodeToMemory(&pem.Block{
Type: "CERTIFICATE",
Bytes: b,
}), 0600); err != nil {
return err
}
ui.PrintSelected("Root Key", resp.Name)
ui.PrintSelected("Root Certificate", "root_ca.crt")
}
// Intermediate Certificate
var keyName string
var publicKey crypto.PublicKey
if c.RootOnly {
priv, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
if err != nil {
return errors.Wrap(err, "error creating intermediate key")
}
pass, err := ui.PromptPasswordGenerate("What do you want your password to be? [leave empty and we'll generate one]",
ui.WithRichPrompt())
if err != nil {
return err
}
_, err = pemutil.Serialize(priv, pemutil.WithPassword(pass), pemutil.ToFile("intermediate_ca_key", 0600))
if err != nil {
return err
}
publicKey = priv.Public()
} else {
resp, err := k.CreateKey(&apiv1.CreateKeyRequest{
Name: c.CrtSlot,
SignatureAlgorithm: apiv1.ECDSAWithSHA256,
})
if err != nil {
return err
}
publicKey = resp.PublicKey
keyName = resp.Name
}
template := &x509.Certificate{
IsCA: true,
NotBefore: now,
NotAfter: now.Add(time.Hour * 24 * 365 * 10),
KeyUsage: x509.KeyUsageCertSign | x509.KeyUsageCRLSign,
BasicConstraintsValid: true,
MaxPathLen: 0,
MaxPathLenZero: true,
Issuer: root.Subject,
Subject: pkix.Name{CommonName: "YubiKey Smallstep Intermediate"},
SerialNumber: mustSerialNumber(),
SubjectKeyId: mustSubjectKeyID(publicKey),
}
b, err := x509.CreateCertificate(rand.Reader, template, root, publicKey, signer)
if err != nil {
return err
}
intermediate, err := x509.ParseCertificate(b)
if err != nil {
return errors.Wrap(err, "error parsing intermediate certificate")
}
if cm, ok := k.(kms.CertificateManager); ok {
if err = cm.StoreCertificate(&apiv1.StoreCertificateRequest{
Name: c.CrtSlot,
Certificate: intermediate,
}); err != nil {
return err
}
}
if err = fileutil.WriteFile("intermediate_ca.crt", pem.EncodeToMemory(&pem.Block{
Type: "CERTIFICATE",
Bytes: b,
}), 0600); err != nil {
return err
}
if c.RootOnly {
ui.PrintSelected("Intermediate Key", "intermediate_ca_key")
} else {
ui.PrintSelected("Intermediate Key", keyName)
}
ui.PrintSelected("Intermediate Certificate", "intermediate_ca.crt")
return nil
}
func mustSerialNumber() *big.Int {
serialNumberLimit := new(big.Int).Lsh(big.NewInt(1), 128)
sn, err := rand.Int(rand.Reader, serialNumberLimit)
if err != nil {
panic(err)
}
return sn
}
func mustSubjectKeyID(key crypto.PublicKey) []byte {
b, err := x509.MarshalPKIXPublicKey(key)
if err != nil {
panic(err)
}
hash := sha1.Sum(b)
return hash[:]
}