Allow to use custom SSH user/host key files.

authority/authority.go

@@ -8,6 +8,7 @@ import (
 	"sync"
 	"time"
 
+	"github.com/pkg/errors"
 	"github.com/smallstep/certificates/authority/provisioner"
 	"github.com/smallstep/certificates/db"
 	"github.com/smallstep/cli/crypto/pemutil"
@@ -120,8 +121,21 @@ func (a *Authority) init() error {
 		}
 	}
 
-	a.sshCAHostCertSignKey = a.intermediateIdentity.Key.(crypto.Signer)
-	a.sshCAUserCertSignKey = a.intermediateIdentity.Key.(crypto.Signer)
+	// Decrypt and load SSH keys
+	if a.config.SSH != nil {
+		if a.config.SSH.HostKey != "" {
+			a.sshCAHostCertSignKey, err = parseCryptoSigner(a.config.SSH.HostKey, a.config.Password)
+			if err != nil {
+				return err
+			}
+		}
+		if a.config.SSH.UserKey != "" {
+			a.sshCAUserCertSignKey, err = parseCryptoSigner(a.config.SSH.UserKey, a.config.Password)
+			if err != nil {
+				return err
+			}
+		}
+	}
 
 	// Store all the provisioners
 	for _, p := range a.config.AuthorityConfig.Provisioners {
@@ -149,3 +163,19 @@ func (a *Authority) GetDatabase() db.AuthDB {
 func (a *Authority) Shutdown() error {
 	return a.db.Shutdown()
 }
+
+func parseCryptoSigner(filename, password string) (crypto.Signer, error) {
+	var opts []pemutil.Options
+	if password != "" {
+		opts = append(opts, pemutil.WithPassword([]byte(password)))
+	}
+	key, err := pemutil.Read(filename, opts...)
+	if err != nil {
+		return nil, err
+	}
+	signer, ok := key.(crypto.Signer)
+	if !ok {
+		return nil, errors.Errorf("key %s of type %T cannot be used for signing operations", filename, key)
+	}
+	return signer, nil
+}

authority/authorize.go

@@ -78,20 +78,13 @@ func (a *Authority) authorizeToken(ott string) (provisioner.Interface, error) {
 func (a *Authority) Authorize(ctx context.Context, ott string) ([]provisioner.SignOption, error) {
 	var errContext = apiCtx{"ott": ott}
 	switch m := provisioner.MethodFromContext(ctx); m {
-	case provisioner.SignMethod, provisioner.SignSSHMethod:
-		p, err := a.authorizeToken(ott)
-		if err != nil {
-			return nil, &apiError{errors.Wrap(err, "authorizeSign"), http.StatusUnauthorized, errContext}
-		}
-
-		// Call the provisioner AuthorizeSign method to apply provisioner specific
-		// auth claims and get the signing options.
-		opts, err := p.AuthorizeSign(ctx, ott)
-		if err != nil {
-			return nil, &apiError{errors.Wrap(err, "authorizeSign"), http.StatusUnauthorized, errContext}
+	case provisioner.SignMethod:
+		return a.authorizeSign(ctx, ott)
+	case provisioner.SignSSHMethod:
+		if a.sshCAHostCertSignKey == nil && a.sshCAUserCertSignKey == nil {
+			return nil, &apiError{errors.New("authorize: ssh signing is not enabled"), http.StatusNotImplemented, errContext}
 		}
-
-		return opts, nil
+		return a.authorizeSign(ctx, ott)
 	case provisioner.RevokeMethod:
 		return nil, &apiError{errors.New("authorize: revoke method is not supported"), http.StatusInternalServerError, errContext}
 	default:
@@ -99,6 +92,22 @@ func (a *Authority) Authorize(ctx context.Context, ott string) ([]provisioner.Si
 	}
 }
 
+// authorizeSign loads the provisioner from the token, checks that it has not
+// been used again and calls the provisioner AuthorizeSign method. returns a
+// list of methods to apply to the signing flow.
+func (a *Authority) authorizeSign(ctx context.Context, ott string) ([]provisioner.SignOption, error) {
+	var errContext = apiCtx{"ott": ott}
+	p, err := a.authorizeToken(ott)
+	if err != nil {
+		return nil, &apiError{errors.Wrap(err, "authorizeSign"), http.StatusUnauthorized, errContext}
+	}
+	opts, err := p.AuthorizeSign(ctx, ott)
+	if err != nil {
+		return nil, &apiError{errors.Wrap(err, "authorizeSign"), http.StatusUnauthorized, errContext}
+	}
+	return opts, nil
+}
+
 // AuthorizeSign authorizes a signature request by validating and authenticating
 // a OTT that must be sent w/ the request.
 func (a *Authority) AuthorizeSign(ott string) ([]provisioner.SignOption, error) {

authority/config.go

@@ -50,6 +50,7 @@ type Config struct {
 	IntermediateKey  string              `json:"key"`
 	Address          string              `json:"address"`
 	DNSNames         []string            `json:"dnsNames"`
+	SSH              *SSHConfig          `json:"ssh,omitempty"`
 	Logger           json.RawMessage     `json:"logger,omitempty"`
 	DB               *db.Config          `json:"db,omitempty"`
 	Monitoring       json.RawMessage     `json:"monitoring,omitempty"`
@@ -98,6 +99,12 @@ func (c *AuthConfig) Validate(audiences provisioner.Audiences) error {
 	return nil
 }
 
+// SSHConfig contains the user and host keys.
+type SSHConfig struct {
+	HostKey string `json:"hostKey"`
+	UserKey string `json:"userKey"`
+}
+
 // LoadConfiguration parses the given filename in JSON format and returns the
 // configuration struct.
 func LoadConfiguration(filename string) (*Config, error) {

authority/ssh.go

@@ -81,8 +81,20 @@ func (a *Authority) SignSSH(key ssh.PublicKey, opts provisioner.SSHOptions, sign
 	var signer ssh.Signer
 	switch cert.CertType {
 	case ssh.UserCert:
+		if a.sshCAUserCertSignKey == nil {
+			return nil, &apiError{
+				err:  errors.New("signSSH: user certificate signing is not enabled"),
+				code: http.StatusNotImplemented,
+			}
+		}
 		signer, err = ssh.NewSignerFromSigner(a.sshCAUserCertSignKey)
 	case ssh.HostCert:
+		if a.sshCAHostCertSignKey == nil {
+			return nil, &apiError{
+				err:  errors.New("signSSH: host certificate signing is not enabled"),
+				code: http.StatusNotImplemented,
+			}
+		}
 		signer, err = ssh.NewSignerFromSigner(a.sshCAHostCertSignKey)
 	default:
 		return nil, &apiError{