Refactor the initialization of KeyManagers.

kms/apiv1/options.go

@@ -1,11 +1,28 @@
 package apiv1
 
 import (
+	"crypto"
+	"crypto/x509"
 	"strings"
 
 	"github.com/pkg/errors"
 )
 
+// KeyManager is the interface implemented by all the KMS.
+type KeyManager interface {
+	GetPublicKey(req *GetPublicKeyRequest) (crypto.PublicKey, error)
+	CreateKey(req *CreateKeyRequest) (*CreateKeyResponse, error)
+	CreateSigner(req *CreateSignerRequest) (crypto.Signer, error)
+	Close() error
+}
+
+// CertificateManager is the interface implemented by the KMS that can load and
+// store x509.Certificates.
+type CertificateManager interface {
+	LoadCerticate(req *LoadCertificateRequest) (*x509.Certificate, error)
+	StoreCertificate(req *StoreCertificateRequest) error
+}
+
 // ErrNotImplemented
 type ErrNotImplemented struct {
 	msg string

kms/apiv1/registry.go

@@ -0,0 +1,27 @@
+package apiv1
+
+import (
+	"context"
+	"sync"
+)
+
+var registry = new(sync.Map)
+
+// KeyManagerNewFunc is the type that represents the method to initialize a new
+// KeyManager.
+type KeyManagerNewFunc func(ctx context.Context, opts Options) (KeyManager, error)
+
+// Register adds to the registry a method to create a KeyManager of type t.
+func Register(t Type, fn KeyManagerNewFunc) {
+	registry.Store(t, fn)
+}
+
+// LoadKeyManagerNewFunc returns the function initialize a KayManager.
+func LoadKeyManagerNewFunc(t Type) (KeyManagerNewFunc, bool) {
+	v, ok := registry.Load(t)
+	if !ok {
+		return nil, false
+	}
+	fn, ok := v.(KeyManagerNewFunc)
+	return fn, ok
+}

kms/cloudkms/cloudkms.go

@@ -93,6 +93,12 @@ func New(ctx context.Context, opts apiv1.Options) (*CloudKMS, error) {
 	}, nil
 }
 
+func init() {
+	apiv1.Register(apiv1.CloudKMS, func(ctx context.Context, opts apiv1.Options) (apiv1.KeyManager, error) {
+		return New(ctx, opts)
+	})
+}
+
 // NewCloudKMS creates a CloudKMS with a given client.
 func NewCloudKMS(client KeyManagementClient) *CloudKMS {
 	return &CloudKMS{

kms/kms.go

@@ -2,30 +2,18 @@ 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.
-type KeyManager interface {
-	GetPublicKey(req *apiv1.GetPublicKeyRequest) (crypto.PublicKey, error)
-	CreateKey(req *apiv1.CreateKeyRequest) (*apiv1.CreateKeyResponse, error)
-	CreateSigner(req *apiv1.CreateSignerRequest) (crypto.Signer, error)
-	Close() error
-}
+type KeyManager = apiv1.KeyManager
 
-// 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
-}
+// CertificateManager is the interface implemented by the KMS that can load and
+// store x509.Certificates.
+type CertificateManager = apiv1.CertificateManager
 
 // New initializes a new KMS from the given type.
 func New(ctx context.Context, opts apiv1.Options) (KeyManager, error) {
@@ -33,14 +21,14 @@ func New(ctx context.Context, opts apiv1.Options) (KeyManager, error) {
 		return nil, err
 	}
 
-	switch apiv1.Type(strings.ToLower(opts.Type)) {
-	case apiv1.DefaultKMS, apiv1.SoftKMS:
-		return softkms.New(ctx, opts)
-	case apiv1.CloudKMS:
-		return cloudkms.New(ctx, opts)
-	case apiv1.YubiKey:
-		return yubikey.New(ctx, opts)
-	default:
+	t := apiv1.Type(strings.ToLower(opts.Type))
+	if t == apiv1.DefaultKMS {
+		t = apiv1.SoftKMS
+	}
+
+	fn, ok := apiv1.LoadKeyManagerNewFunc(t)
+	if !ok {
 		return nil, errors.Errorf("unsupported kms type '%s'", opts.Type)
 	}
+	return fn(ctx, opts)
 }

kms/softkms/softkms.go

@@ -52,6 +52,12 @@ func New(ctx context.Context, opts apiv1.Options) (*SoftKMS, error) {
 	return &SoftKMS{}, nil
 }
 
+func init() {
+	apiv1.Register(apiv1.SoftKMS, func(ctx context.Context, opts apiv1.Options) (apiv1.KeyManager, error) {
+		return New(ctx, opts)
+	})
+}
+
 // Close is a noop that just returns nil.
 func (k *SoftKMS) Close() error {
 	return nil

kms/yubikey/yubikey.go

@@ -42,6 +42,12 @@ func New(ctx context.Context, opts apiv1.Options) (*YubiKey, error) {
 	}, nil
 }
 
+func init() {
+	apiv1.Register(apiv1.YubiKey, func(ctx context.Context, opts apiv1.Options) (apiv1.KeyManager, error) {
+		return New(ctx, opts)
+	})
+}
+
 // LoadCertificate implements kms.CertificateManager and loads a certificate
 // from the YubiKey.
 func (k *YubiKey) LoadCertificate(req *apiv1.LoadCertificateRequest) (*x509.Certificate, error) {

kms/yubikey/yubikey_no_cgo.go

@@ -4,47 +4,16 @@ package yubikey
 
 import (
 	"context"
-	"crypto"
-	"crypto/x509"
+	"os"
+	"path/filepath"
 
 	"github.com/pkg/errors"
 	"github.com/smallstep/certificates/kms/apiv1"
 )
 
-// YubiKey implements the KMS interface on a YubiKey.
-type YubiKey struct{}
-
-// New always fails without CGO.
-func New(ctx context.Context, opts apiv1.Options) (*YubiKey, error) {
-	return nil, errors.New("YubiKey is not supported without cgo")
-}
-
-// LoadCertificate always fails without CGO.
-func (k *YubiKey) LoadCertificate(req *apiv1.LoadCertificateRequest) (*x509.Certificate, error) {
-	return nil, errors.New("YubiKey is not supported without cgo")
-}
-
-// StoreCertificate always fails without CGO.
-func (k *YubiKey) StoreCertificate(req *apiv1.StoreCertificateRequest) error {
-	return errors.New("YubiKey is not supported without cgo")
-}
-
-// GetPublicKey always fails without CGO.
-func (k *YubiKey) GetPublicKey(req *apiv1.GetPublicKeyRequest) (crypto.PublicKey, error) {
-	return nil, errors.New("YubiKey is not supported without cgo")
-}
-
-// CreateKey always fails without CGO.
-func (k *YubiKey) CreateKey(req *apiv1.CreateKeyRequest) (*apiv1.CreateKeyResponse, error) {
-	return nil, errors.New("YubiKey is not supported without cgo")
-}
-
-// CreateSigner always fails without CGO.
-func (k *YubiKey) CreateSigner(req *apiv1.CreateSignerRequest) (crypto.Signer, error) {
-	return nil, errors.New("YubiKey is not supported without cgo")
-}
-
-// Close always fails without CGO.
-func (k *YubiKey) Close() error {
-	return errors.New("YubiKey is not supported without cgo")
+func init() {
+	apiv1.Register(apiv1.YubiKey, func(ctx context.Context, opts apiv1.Options) (apiv1.KeyManager, error) {
+		name := filepath.Base(os.Args[0])
+		return nil, errors.Errorf("unsupported kms type 'yubikey': %s is compiled without cgo support", name)
+	})
 }