From 6868190fff9da9c40871e40d023e02a1698dc7f4 Mon Sep 17 00:00:00 2001 From: Mariano Cano Date: Thu, 7 May 2020 18:22:09 -0700 Subject: [PATCH] Add initial support for yubikey. --- cmd/step-yubikey-init/main.go | 289 ++++++++++++++++++++++++++++++++++ go.mod | 1 + go.sum | 2 + kms/apiv1/options.go | 3 + kms/apiv1/requests.go | 14 ++ kms/kms.go | 10 ++ kms/yubikey/yubikey.go | 244 ++++++++++++++++++++++++++++ 7 files changed, 563 insertions(+) create mode 100644 cmd/step-yubikey-init/main.go create mode 100644 kms/yubikey/yubikey.go diff --git a/cmd/step-yubikey-init/main.go b/cmd/step-yubikey-init/main.go new file mode 100644 index 00000000..9a5370c0 --- /dev/null +++ b/cmd/step-yubikey-init/main.go @@ -0,0 +1,289 @@ +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/apiv1" + "github.com/smallstep/certificates/kms/yubikey" + "github.com/smallstep/cli/crypto/pemutil" + "github.com/smallstep/cli/ui" + "github.com/smallstep/cli/utils" +) + +type Config struct { + RootOnly bool + RootSlot string + CrtSlot string + RootFile string + KeyFile string + Pin string +} + +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("flat `--root-slot` and flag `--crt-slot` cannot be the same") + default: + 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.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 := yubikey.New(context.Background(), apiv1.Options{ + Type: string(apiv1.YubiKey), + Pin: c.Pin, + }) + if err != nil { + fatal(err) + } + + 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 createPKI(k *yubikey.YubiKey, 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), + } + + 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 err = k.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", "yubikey:slot-id="+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 public 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 err = k.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", "yubikey:slot-id="+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[:] +} diff --git a/go.mod b/go.mod index 9cbf1418..c81244cf 100644 --- a/go.mod +++ b/go.mod @@ -6,6 +6,7 @@ require ( cloud.google.com/go v0.51.0 github.com/Masterminds/sprig/v3 v3.0.0 github.com/go-chi/chi v4.0.2+incompatible + github.com/go-piv/piv-go v1.5.0 github.com/googleapis/gax-go/v2 v2.0.5 github.com/juju/ansiterm v0.0.0-20180109212912-720a0952cc2a // indirect github.com/lunixbochs/vtclean v1.0.0 // indirect diff --git a/go.sum b/go.sum index 8bb4b771..7a9caaef 100644 --- a/go.sum +++ b/go.sum @@ -124,6 +124,8 @@ github.com/go-lintpack/lintpack v0.5.2/go.mod h1:NwZuYi2nUHho8XEIZ6SIxihrnPoqBTD github.com/go-logfmt/logfmt v0.3.0/go.mod h1:Qt1PoO58o5twSAckw1HlFXLmHsOX5/0LbT9GBnD5lWE= github.com/go-logfmt/logfmt v0.4.0/go.mod h1:3RMwSq7FuexP4Kalkev3ejPJsZTpXXBr9+V4qmtdjCk= github.com/go-ole/go-ole v1.2.1/go.mod h1:7FAglXiTm7HKlQRDeOQ6ZNUHidzCWXuZWq/1dTyBNF8= +github.com/go-piv/piv-go v1.5.0 h1:UtHPfrJsZKY+Z3UIjmJLh6DY+KtmNOl/9b/zt4N81pM= +github.com/go-piv/piv-go v1.5.0/go.mod h1:ON2WvQncm7dIkCQ7kYJs+nc3V4jHGfrrJnSF8HKy7Gk= github.com/go-sql-driver/mysql v1.4.1 h1:g24URVg0OFbNUTx9qqY1IRZ9D9z3iPyi5zKhQZpNwpA= github.com/go-sql-driver/mysql v1.4.1/go.mod h1:zAC/RDZ24gD3HViQzih4MyKcchzm+sOG5ZlKdlhCg5w= github.com/go-stack/stack v1.8.0/go.mod h1:v0f6uXyyMGvRgIKkXu+yp6POWl0qKG85gN/melR3HDY= diff --git a/kms/apiv1/options.go b/kms/apiv1/options.go index a46db037..62ca97e9 100644 --- a/kms/apiv1/options.go +++ b/kms/apiv1/options.go @@ -32,6 +32,8 @@ const ( AmazonKMS Type = "awskms" // PKCS11 is a KMS implementation using the PKCS11 standard. PKCS11 Type = "pkcs11" + // YubiKey is a KMS implementation using a YubiKey PIV. + YubiKey Type = "yubikey" ) type Options struct { @@ -56,6 +58,7 @@ func (o *Options) Validate() error { switch Type(strings.ToLower(o.Type)) { case DefaultKMS, SoftKMS, CloudKMS: + case YubiKey: case AmazonKMS: return ErrNotImplemented{"support for AmazonKMS is not yet implemented"} case PKCS11: diff --git a/kms/apiv1/requests.go b/kms/apiv1/requests.go index 35c2fcae..bbee4cfc 100644 --- a/kms/apiv1/requests.go +++ b/kms/apiv1/requests.go @@ -2,6 +2,7 @@ package apiv1 import ( "crypto" + "crypto/x509" "fmt" ) @@ -124,3 +125,16 @@ type CreateSignerRequest struct { PublicKeyPEM []byte Password []byte } + +// LoadCertificateRequest is the parameter used in the LoadCertificate method of +// a CertificateManager. +type LoadCertificateRequest struct { + Name string +} + +// StoreCertificateRequest is the parameter used in the StoreCertificate method +// of a CertificateManager. +type StoreCertificateRequest struct { + Name string + Certificate *x509.Certificate +} diff --git a/kms/kms.go b/kms/kms.go index 209783e5..880bb9df 100644 --- a/kms/kms.go +++ b/kms/kms.go @@ -3,12 +3,14 @@ package kms import ( "context" "crypto" + "crypto/x509" "strings" "github.com/pkg/errors" "github.com/smallstep/certificates/kms/apiv1" "github.com/smallstep/certificates/kms/cloudkms" "github.com/smallstep/certificates/kms/softkms" + "github.com/smallstep/certificates/kms/yubikey" ) // KeyManager is the interface implemented by all the KMS. @@ -19,6 +21,12 @@ type KeyManager interface { Close() error } +// CertificateManager is the interface implemented by the KMS that can load and store x509.Certificates. +type CertificateManager interface { + LoadCerticate(req *apiv1.LoadCertificateRequest) (*x509.Certificate, error) + StoreCertificate(req *apiv1.StoreCertificateRequest) error +} + // New initializes a new KMS from the given type. func New(ctx context.Context, opts apiv1.Options) (KeyManager, error) { if err := opts.Validate(); err != nil { @@ -30,6 +38,8 @@ func New(ctx context.Context, opts apiv1.Options) (KeyManager, error) { return softkms.New(ctx, opts) case apiv1.CloudKMS: return cloudkms.New(ctx, opts) + case apiv1.YubiKey: + return yubikey.New(ctx, opts) default: return nil, errors.Errorf("unsupported kms type '%s'", opts.Type) } diff --git a/kms/yubikey/yubikey.go b/kms/yubikey/yubikey.go new file mode 100644 index 00000000..c435f676 --- /dev/null +++ b/kms/yubikey/yubikey.go @@ -0,0 +1,244 @@ +package yubikey + +import ( + "context" + "crypto" + "crypto/x509" + "net/url" + "strings" + + "github.com/go-piv/piv-go/piv" + "github.com/pkg/errors" + "github.com/smallstep/certificates/kms/apiv1" +) + +// YubiKey implements the KMS interface on a YubiKey. +type YubiKey struct { + yk *piv.YubiKey + pin string +} + +// New initializes a new YubiKey. +// TODO(mariano): only one card is currently supported. +func New(ctx context.Context, opts apiv1.Options) (*YubiKey, error) { + cards, err := piv.Cards() + if err != nil { + return nil, err + } + if len(cards) == 0 { + return nil, errors.New("error detecting yubikey") + } + + yk, err := piv.Open(cards[0]) + if err != nil { + return nil, errors.Wrap(err, "error opening yubikey") + } + + return &YubiKey{ + yk: yk, + pin: opts.Pin, + }, nil +} + +// LoadCertificate implements kms.CertificateManager and loads a certificate +// from the YubiKey. +func (k *YubiKey) LoadCertificate(req *apiv1.LoadCertificateRequest) (*x509.Certificate, error) { + slot, err := getSlot(req.Name) + if err != nil { + return nil, err + } + + cert, err := k.yk.Certificate(slot) + if err != nil { + return nil, errors.Wrap(err, "error retrieving certificate") + } + + return cert, nil +} + +// StoreCertificate implements kms.CertificateManager and stores a certificate +// in the YubiKey. +func (k *YubiKey) StoreCertificate(req *apiv1.StoreCertificateRequest) error { + if req.Certificate == nil { + return errors.New("storeCertificateRequest 'Certificate' cannot be nil") + } + + slot, err := getSlot(req.Name) + if err != nil { + return err + } + + err = k.yk.SetCertificate(piv.DefaultManagementKey, slot, req.Certificate) + if err != nil { + return errors.Wrap(err, "error storing certificate") + } + + return nil +} + +// GetPublicKey returns the public key present in the YubiKey signature slot. +func (k *YubiKey) GetPublicKey(req *apiv1.GetPublicKeyRequest) (crypto.PublicKey, error) { + slot, err := getSlot(req.Name) + if err != nil { + return nil, err + } + + cert, err := k.yk.Certificate(slot) + if err != nil { + return nil, errors.Wrap(err, "error retrieving certificate") + } + + return cert.PublicKey, nil +} + +// CreateKey generates a new key in the YubiKey and returns the public key. +func (k *YubiKey) CreateKey(req *apiv1.CreateKeyRequest) (*apiv1.CreateKeyResponse, error) { + alg, err := getSignatureAlgorithm(req.SignatureAlgorithm, req.Bits) + if err != nil { + return nil, err + } + slot, name, err := getSlotAndName(req.Name) + if err != nil { + return nil, err + } + + pub, err := k.yk.GenerateKey(piv.DefaultManagementKey, slot, piv.Key{ + Algorithm: alg, + PINPolicy: piv.PINPolicyAlways, + TouchPolicy: piv.TouchPolicyNever, + }) + if err != nil { + return nil, errors.Wrap(err, "error generating key") + } + return &apiv1.CreateKeyResponse{ + Name: name, + PublicKey: pub, + CreateSignerRequest: apiv1.CreateSignerRequest{ + SigningKey: name, + }, + }, nil +} + +// CreateSigner creates a signer using the key present in the YubiKey signature +// slot. +func (k *YubiKey) CreateSigner(req *apiv1.CreateSignerRequest) (crypto.Signer, error) { + slot, err := getSlot(req.SigningKey) + if err != nil { + return nil, err + } + + cert, err := k.yk.Certificate(slot) + if err != nil { + return nil, errors.Wrap(err, "error retrieving certificate") + } + + priv, err := k.yk.PrivateKey(slot, cert.PublicKey, piv.KeyAuth{ + PIN: k.pin, + }) + if err != nil { + return nil, errors.Wrap(err, "error retrieving private key") + } + + signer, ok := priv.(crypto.Signer) + if !ok { + return nil, errors.New("private key is not a crypto.Signer") + } + return signer, nil +} + +// Close releases the connection to the YubiKey. +func (k *YubiKey) Close() error { + return errors.Wrap(k.yk.Close(), "error closing yubikey") +} + +// signatureAlgorithmMapping is a mapping between the step signature algorithm, +// and bits for RSA keys, with yubikey ones. +var signatureAlgorithmMapping = map[apiv1.SignatureAlgorithm]interface{}{ + apiv1.UnspecifiedSignAlgorithm: piv.AlgorithmEC256, + apiv1.SHA256WithRSA: map[int]piv.Algorithm{ + 0: piv.AlgorithmRSA2048, + 1024: piv.AlgorithmRSA1024, + 2048: piv.AlgorithmRSA2048, + }, + apiv1.SHA512WithRSA: map[int]piv.Algorithm{ + 0: piv.AlgorithmRSA2048, + 1024: piv.AlgorithmRSA1024, + 2048: piv.AlgorithmRSA2048, + }, + apiv1.SHA256WithRSAPSS: map[int]piv.Algorithm{ + 0: piv.AlgorithmRSA2048, + 1024: piv.AlgorithmRSA1024, + 2048: piv.AlgorithmRSA2048, + }, + apiv1.SHA512WithRSAPSS: map[int]piv.Algorithm{ + 0: piv.AlgorithmRSA2048, + 1024: piv.AlgorithmRSA1024, + 2048: piv.AlgorithmRSA2048, + }, + apiv1.ECDSAWithSHA256: piv.AlgorithmEC256, + apiv1.ECDSAWithSHA384: piv.AlgorithmEC384, +} + +func getSignatureAlgorithm(alg apiv1.SignatureAlgorithm, bits int) (piv.Algorithm, error) { + v, ok := signatureAlgorithmMapping[alg] + if !ok { + return 0, errors.Errorf("YubiKey does not support signature algorithm '%s'", alg) + } + + switch v := v.(type) { + case piv.Algorithm: + return v, nil + case map[int]piv.Algorithm: + signatureAlgorithm, ok := v[bits] + if !ok { + return 0, errors.Errorf("YubiKey does not support signature algorithm '%s' with '%d' bits", alg, bits) + } + return signatureAlgorithm, nil + default: + return 0, errors.Errorf("unexpected error: this should not happen") + } +} + +var slotMapping = map[string]piv.Slot{ + "9a": piv.SlotAuthentication, + "9c": piv.SlotSignature, + "9e": piv.SlotCardAuthentication, + "9d": piv.SlotKeyManagement, +} + +func getSlot(name string) (piv.Slot, error) { + slot, _, err := getSlotAndName(name) + return slot, err +} + +func getSlotAndName(name string) (piv.Slot, string, error) { + if name == "" { + return piv.SlotSignature, "yubikey:slot-id=9c", nil + } + + var slotID string + name = strings.ToLower(name) + if strings.HasPrefix(name, "yubikey:") { + u, err := url.Parse(name) + if err != nil { + return piv.Slot{}, "", errors.Wrapf(err, "error parsing '%s'", name) + } + v, err := url.ParseQuery(u.Opaque) + if err != nil { + return piv.Slot{}, "", errors.Wrapf(err, "error parsing '%s'", name) + } + if slotID = v.Get("slot-id"); slotID == "" { + return piv.Slot{}, "", errors.Wrapf(err, "error parsing '%s': slot-id is missing", name) + } + } else { + slotID = name + } + + s, ok := slotMapping[slotID] + if !ok { + return piv.Slot{}, "", errors.Errorf("usupported slot-id '%s'", name) + } + + name = "yubikey:slot-id=" + url.QueryEscape(slotID) + return s, name, nil +}