feat: allow using a local RSA key for machine keys (#7671)

* Allow using a local RSA key for machine keys

* Add check for key validity

* Fix naming error

* docs: provide translations of invalid key

---------

Co-authored-by: Livio Spring <livio.a@gmail.com>

internal/api/grpc/management/user.go

@@ -774,13 +774,22 @@ func (s *Server) ListMachineKeys(ctx context.Context, req *mgmt_pb.ListMachineKe
 
 func (s *Server) AddMachineKey(ctx context.Context, req *mgmt_pb.AddMachineKeyRequest) (*mgmt_pb.AddMachineKeyResponse, error) {
 	machineKey := AddMachineKeyRequestToCommand(req, authz.GetCtxData(ctx).OrgID)
+	// If there is no pubkey supplied, then AddUserMachineKey will generate a new one
+	pubkeySupplied := len(machineKey.PublicKey) > 0
 	details, err := s.command.AddUserMachineKey(ctx, machineKey)
 	if err != nil {
 		return nil, err
 	}
-	keyDetails, err := machineKey.Detail()
-	if err != nil {
-		return nil, err
+
+	// Return key details only if the pubkey wasn't supplied, otherwise the user already has
+	// private key locally
+	var keyDetails []byte
+	if !pubkeySupplied {
+		var err error
+		keyDetails, err = machineKey.Detail()
+		if err != nil {
+			return nil, err
+		}
 	}
 	return &mgmt_pb.AddMachineKeyResponse{
 		KeyId:      machineKey.KeyID,

internal/api/grpc/management/user_converter.go

@@ -237,6 +237,7 @@ func AddMachineKeyRequestToCommand(req *mgmt_pb.AddMachineKeyRequest, resourceOw
 		},
 		ExpirationDate: expDate,
 		Type:           authn.KeyTypeToDomain(req.Type),
+		PublicKey:      req.PublicKey,
 	}
 }