fix(api): check if admin user already exists when calling the /users/admin/init endpoint (#494)

api/errors.go

@@ -8,6 +8,7 @@ const (
 // User errors.
 const (
 	ErrUserNotFound            = Error("User not found")
+	ErrAdminAlreadyInitialized = Error("Admin user already initialized")
 )
 
 // Endpoint errors.

api/http/user_handler.go

@@ -227,6 +227,8 @@ func (handler *UserHandler) handlePostAdminInit(w http.ResponseWriter, r *http.R
 		return
 	}
 
+	user, err := handler.UserService.User("admin")
+	if err == portainer.ErrUserNotFound {
 		user := &portainer.User{
 			Username: "admin",
 		}
@@ -241,6 +243,14 @@ func (handler *UserHandler) handlePostAdminInit(w http.ResponseWriter, r *http.R
 			Error(w, err, http.StatusInternalServerError, handler.Logger)
 			return
 		}
+	} else if err != nil {
+		Error(w, err, http.StatusInternalServerError, handler.Logger)
+		return
+	}
+	if user != nil {
+		Error(w, portainer.ErrAdminAlreadyInitialized, http.StatusForbidden, handler.Logger)
+		return
+	}
 }
 
 type postAdminInitRequest struct {