Add initial implementation of ssh config.

api/ssh.go

@@ -7,6 +7,7 @@ import (
 	"net/http"
 
 	"github.com/pkg/errors"
+	"github.com/smallstep/certificates/authority"
 	"github.com/smallstep/certificates/authority/provisioner"
 	"golang.org/x/crypto/ssh"
 )
@@ -15,6 +16,7 @@ import (
 type SSHAuthority interface {
 	SignSSH(key ssh.PublicKey, opts provisioner.SSHOptions, signOpts ...provisioner.SignOption) (*ssh.Certificate, error)
 	SignSSHAddUser(key ssh.PublicKey, cert *ssh.Certificate) (*ssh.Certificate, error)
+	SSHConfig() (*authority.SSHConfiguration, error)
 }
 
 // SignSSHRequest is the request body of an SSH certificate request.
@@ -34,6 +36,13 @@ type SignSSHResponse struct {
 	AddUserCertificate *SSHCertificate `json:"addUserCrt,omitempty"`
 }
 
+// SSHConfigResponse represents the response object that returns the SSH user
+// and host keys.
+type SSHConfigResponse struct {
+	UserKey *SSHPublicKey `json:"userKey,omitempty"`
+	HostKey *SSHPublicKey `json:"hostKey,omitempty"`
+}
+
 // SSHCertificate represents the response SSH certificate.
 type SSHCertificate struct {
 	*ssh.Certificate `json:"omitempty"`
@@ -49,6 +58,21 @@ func (c SSHCertificate) MarshalJSON() ([]byte, error) {
 	return []byte(`"` + s + `"`), nil
 }
 
+// SSHPublicKey represents a public key in a response object.
+type SSHPublicKey struct {
+	ssh.PublicKey
+}
+
+// MarshalJSON implements the json.Marshaler interface. Returns a quoted,
+// base64 encoded, openssh wire format version of the public key.
+func (p *SSHPublicKey) MarshalJSON() ([]byte, error) {
+	if p == nil || p.PublicKey == nil {
+		return []byte("null"), nil
+	}
+	s := base64.StdEncoding.EncodeToString(p.PublicKey.Marshal())
+	return []byte(`"` + s + `"`), nil
+}
+
 // UnmarshalJSON implements the json.Unmarshaler interface. The certificate is
 // expected to be a quoted, base64 encoded, openssh wire formatted block of bytes.
 func (c *SSHCertificate) UnmarshalJSON(data []byte) error {
@@ -157,3 +181,26 @@ func (h *caHandler) SignSSH(w http.ResponseWriter, r *http.Request) {
 		AddUserCertificate: addUserCertificate,
 	})
 }
+
+// SSHConfig is an HTTP handler that returns the SSH public keys for user and
+// host certificates.
+func (h *caHandler) SSHConfig(w http.ResponseWriter, r *http.Request) {
+	config, err := h.Authority.SSHConfig()
+	if err != nil {
+		WriteError(w, NotFound(err))
+		return
+	}
+
+	var host, user *SSHPublicKey
+	if config.HostKey != nil {
+		host = &SSHPublicKey{config.HostKey}
+	}
+	if config.UserKey != nil {
+		user = &SSHPublicKey{config.UserKey}
+	}
+
+	JSON(w, &SSHConfigResponse{
+		HostKey: host,
+		UserKey: user,
+	})
+}

authority/authority.go

@@ -13,6 +13,7 @@ import (
 	"github.com/smallstep/certificates/db"
 	"github.com/smallstep/cli/crypto/pemutil"
 	"github.com/smallstep/cli/crypto/x509util"
+	"golang.org/x/crypto/ssh"
 )
 
 const (
@@ -24,8 +25,8 @@ type Authority struct {
 	config               *Config
 	rootX509Certs        []*x509.Certificate
 	intermediateIdentity *x509util.Identity
-	sshCAUserCertSignKey crypto.Signer
-	sshCAHostCertSignKey crypto.Signer
+	sshCAUserCertSignKey ssh.Signer
+	sshCAHostCertSignKey ssh.Signer
 	certificates         *sync.Map
 	startTime            time.Time
 	provisioners         *provisioner.Collection
@@ -125,16 +126,24 @@ func (a *Authority) init() error {
 	// 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)
+			signer, err := parseCryptoSigner(a.config.SSH.HostKey, a.config.Password)
 			if err != nil {
 				return err
 			}
+			a.sshCAHostCertSignKey, err = ssh.NewSignerFromSigner(signer)
+			if err != nil {
+				return errors.Wrap(err, "error creating ssh signer")
+			}
 		}
 		if a.config.SSH.UserKey != "" {
-			a.sshCAUserCertSignKey, err = parseCryptoSigner(a.config.SSH.UserKey, a.config.Password)
+			signer, err := parseCryptoSigner(a.config.SSH.UserKey, a.config.Password)
 			if err != nil {
 				return err
 			}
+			a.sshCAUserCertSignKey, err = ssh.NewSignerFromSigner(signer)
+			if err != nil {
+				return errors.Wrap(err, "error creating ssh signer")
+			}
 		}
 	}
 

authority/ssh.go

@@ -24,6 +24,30 @@ const (
 	SSHAddUserCommand = "sudo useradd -m <principal>; nc -q0 localhost 22"
 )
 
+// SSHConfiguration is the return type for SSHConfig.
+type SSHConfiguration struct {
+	UserKey ssh.PublicKey
+	HostKey ssh.PublicKey
+}
+
+// SSHConfig returns the SSH User and Host public keys.
+func (a *Authority) SSHConfig() (*SSHConfiguration, error) {
+	var config SSHConfiguration
+	if a.sshCAUserCertSignKey != nil {
+		config.UserKey = a.sshCAUserCertSignKey.PublicKey()
+	}
+	if a.sshCAHostCertSignKey != nil {
+		config.HostKey = a.sshCAHostCertSignKey.PublicKey()
+	}
+	if config.UserKey == nil && config.HostKey == nil {
+		return nil, &apiError{
+			err:  errors.New("sshConfig: ssh is not configured"),
+			code: http.StatusNotFound,
+		}
+	}
+	return &config, nil
+}
+
 // SignSSH creates a signed SSH certificate with the given public key and options.
 func (a *Authority) SignSSH(key ssh.PublicKey, opts provisioner.SSHOptions, signOpts ...provisioner.SignOption) (*ssh.Certificate, error) {
 	var mods []provisioner.SSHCertificateModifier
@@ -95,12 +119,7 @@ func (a *Authority) SignSSH(key ssh.PublicKey, opts provisioner.SSHOptions, sign
 				code: http.StatusNotImplemented,
 			}
 		}
-		if signer, err = ssh.NewSignerFromSigner(a.sshCAUserCertSignKey); err != nil {
-			return nil, &apiError{
-				err:  errors.Wrap(err, "signSSH: error creating signer"),
-				code: http.StatusInternalServerError,
-			}
-		}
+		signer = a.sshCAUserCertSignKey
 	case ssh.HostCert:
 		if a.sshCAHostCertSignKey == nil {
 			return nil, &apiError{
@@ -108,12 +127,7 @@ func (a *Authority) SignSSH(key ssh.PublicKey, opts provisioner.SSHOptions, sign
 				code: http.StatusNotImplemented,
 			}
 		}
-		if signer, err = ssh.NewSignerFromSigner(a.sshCAHostCertSignKey); err != nil {
-			return nil, &apiError{
-				err:  errors.Wrap(err, "signSSH: error creating signer"),
-				code: http.StatusInternalServerError,
-			}
-		}
+		signer = a.sshCAHostCertSignKey
 	default:
 		return nil, &apiError{
 			err:  errors.Errorf("signSSH: unexpected ssh certificate type: %d", cert.CertType),
@@ -180,14 +194,7 @@ func (a *Authority) SignSSHAddUser(key ssh.PublicKey, subject *ssh.Certificate)
 		}
 	}
 
-	signer, err := ssh.NewSignerFromSigner(a.sshCAUserCertSignKey)
-	if err != nil {
-		return nil, &apiError{
-			err:  errors.Wrap(err, "signSSHProxy: error creating signer"),
-			code: http.StatusInternalServerError,
-		}
-	}
-
+	signer := a.sshCAUserCertSignKey
 	principal := subject.ValidPrincipals[0]
 	addUserPrincipal := a.getAddUserPrincipal()