This site is the archived OWASP Foundation Wiki and is no longer accepting Account Requests.
To view the new OWASP Foundation website, please visit https://owasp.org

Difference between revisions of "Mass Assignment Cheat Sheet"

From OWASP
Jump to: navigation, search
m
Line 6: Line 6:
 
Last revision (mm/dd/yy): '''{{REVISIONMONTH}}/{{REVISIONDAY}}/{{REVISIONYEAR}}'''  
 
Last revision (mm/dd/yy): '''{{REVISIONMONTH}}/{{REVISIONDAY}}/{{REVISIONYEAR}}'''  
 
<div class="noautonum">__TOC__{{TOC hidden}}</div>
 
<div class="noautonum">__TOC__{{TOC hidden}}</div>
 
  
 
= Introduction =
 
= Introduction =
 
=== Definition ===
 
=== Definition ===
 
"Modern frameworks allow developers to automatically bind HTTP request parameters from both request query and body into model objects for ease of development and increased productivity. If the binder is not correctly configured to control which HTTP request parameters are bound to which model attributes, an attacker may be able to abuse the model binding process and set any other attributes that should not be exposed to user control. This binding is possible even if the model attributes do not appear in the web forms or API contracts." - [http://www.hpenterprisesecurity.com/vulncat/en/vulncat/java/mass_assignment_sensitive_field_exposure.html Mass Assignment: Sensitive Field Exposure]
 
"Modern frameworks allow developers to automatically bind HTTP request parameters from both request query and body into model objects for ease of development and increased productivity. If the binder is not correctly configured to control which HTTP request parameters are bound to which model attributes, an attacker may be able to abuse the model binding process and set any other attributes that should not be exposed to user control. This binding is possible even if the model attributes do not appear in the web forms or API contracts." - [http://www.hpenterprisesecurity.com/vulncat/en/vulncat/java/mass_assignment_sensitive_field_exposure.html Mass Assignment: Sensitive Field Exposure]
 
  
 
=== Alternative Names ===
 
=== Alternative Names ===
Line 18: Line 16:
 
* Autobinding: Spring MVC, ASP.NET MVC
 
* Autobinding: Spring MVC, ASP.NET MVC
 
* Object injection: PHP
 
* Object injection: PHP
 
  
 
=== Example ===
 
=== Example ===

Revision as of 01:25, 21 February 2016

Cheatsheets-header.jpg

Last revision (mm/dd/yy): 02/21/2016

Introduction

Definition

"Modern frameworks allow developers to automatically bind HTTP request parameters from both request query and body into model objects for ease of development and increased productivity. If the binder is not correctly configured to control which HTTP request parameters are bound to which model attributes, an attacker may be able to abuse the model binding process and set any other attributes that should not be exposed to user control. This binding is possible even if the model attributes do not appear in the web forms or API contracts." - Mass Assignment: Sensitive Field Exposure

Alternative Names

Depending on the language/framework in question, this vulnerability can have several alternative names

  • Mass Assignment: Ruby on Rails, NodeJS
  • Autobinding: Spring MVC, ASP.NET MVC
  • Object injection: PHP

Example

Suppose there is a form for editing a user's account information:

  <form>
     <input name=userid type=text>
     <input name=password type=text>
     <input name=email text=text>
     <input type=submit>
  </form>

Here is the object that the form is binding to:

  public class User {
     private String userid;
     private String password;
     private String email;
     private boolean isAdmin;
   
     //Getters & Setters
   }

Here is the controller handling the request:

  @RequestMapping(value = "/addUser, method = RequestMethod.POST)
  public String submit(User user) {
     
     userService.add(user);
  
     return "successPage";
  }

Here is the typical request:

  POST /addUser
  
  userid=bobbytables&password=hashedpass&[email protected]

And here is the exploit:

  POST /addUser
  
  userid=bobbytables&password=hashedpass&[email protected]&isAdmin=true


Exploitability

This functionality becomes exploitable when:

  • Attacker can guess common sensitive fields
  • Attacker has access to source code and can review the models for sensitive fields
  • The object with sensitive fields has an empty constructor


Case Studies

GitHub

In 2012, GitHub was hacked using mass assignment. A user was able to upload his public key to any organization and thus make any subsequent changes in their repositories. GitHub's Blog Post


Solutions

  • Whitelist the bindable, non-sensitive fields
  • Blacklist the non-bindable, sensitive fields
  • Use Data Transfer Objects (DTOs)


General Solutions

Data Transfer Objects (DTOs)

An architectural approach is to create Data Transfer Objects and avoid binding input directly to domain objects. Only the fields that are meant to be editable by the user are included in the DTO.

  public class UserRegistrationFormDTO {
     private String userid;
     private String password;
     private String email;
  
     //private boolean isAdmin;
   
     //Getters & Setters
   }


Language & Framework Specific Solutions

Spring MVC

Whitelisting

  @Controller
  public class UserController
  {
     @InitBinder
     public void initBinder(WebDataBinder binder, WebRequest request)
     {
        binder.setAllowedFields(["userid","password","email"]);
     }
  
     ...
  }

Reference

Blacklisting

  @Controller
  public class UserController
  {
     @InitBinder
     public void initBinder(WebDataBinder binder, WebRequest request)
     {
        binder.setDisallowedFields(["isAdmin"]);
     }
  
     ...
  }

Reference


NodeJS + Mongoose

Reference


Ruby On Rails

Reference


Django

Reference


ASP.NET

Reference


PHP Laravel + Eloquent

Whitelisting

  <?php
  
  namespace App;
  
  use Illuminate\Database\Eloquent\Model;
  
  class User extends Model
  {
     private $userid;
     private $password;
     private $email;
     private $isAdmin;
  
     protected $fillable = array('userid','password','email');
  
  }

Reference

Blacklisting

  <?php
  
  namespace App;
  
  use Illuminate\Database\Eloquent\Model;
  
  class User extends Model
  {
     private $userid;
     private $password;
     private $email;
     private $isAdmin;
  
     protected $guarded = array('isAdmin');
  
  }

Reference


Grails

Reference


Play

Reference


Jackson (JSON Object Mapper)

Reference Reference


GSON (JSON Object Mapper)

Reference Reference


JSON-Lib (JSON Object Mapper)

Reference


Flexjson (JSON Object Mapper)

Reference


Authors and Primary Editors

References and future reading

Other Cheatsheets