package main import ( "context" "crypto" "crypto/ecdsa" "crypto/elliptic" "crypto/rand" "crypto/sha1" "crypto/x509" "crypto/x509/pkix" "encoding/pem" "flag" "fmt" "math/big" "os" "time" "github.com/pkg/errors" "github.com/smallstep/certificates/kms" "github.com/smallstep/certificates/kms/apiv1" "github.com/smallstep/cli/ui" "github.com/smallstep/cli/utils" "go.step.sm/crypto/pemutil" // Enable yubikey. _ "github.com/smallstep/certificates/kms/yubikey" ) type Config struct { RootOnly bool RootSlot string CrtSlot string RootFile string KeyFile string Pin string Force bool } func (c *Config) Validate() error { switch { 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 = "" } return nil } } func main() { var c Config 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, }) 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) { 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 = utils.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 = utils.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[:] }