Restricting HTTP Access to AccessControlled Objects

Overview

Types with Jelly/Groovy views or web methods may be restricted to users with a certain permission. Some examples:

  • Item (or AbstractItem) must only be accessed by users with the Item.READ permission.

  • Run must only be accessed by users with the Item.READ permission on the owning Job.

  • AdministrativeMonitor must only be accessed by users with Overall/Administer permission.

This was typically implemented in the past by having the getters returning the object in question check the permission, as in Jenkins#getItem(String). A major downside to this approach is that every Stapler-accessible method returning an AccessControlled object needs to implement such a permission check. Otherwise, a different getter or field could be used to access the object in question, bypassing the permission check. Various security issues have resulted from this strategy, so it is not generally considered sufficient to restrict access to objects on its own.

Using StaplerProxy

A more robust approach to prevent HTTP request handling by objects is to implement StaplerProxy. While originally intended to forward request handling to a different object on certain conditions, it can also be used to just perform a permission check, and returning different values depending on the outcome of that check:

  • return this will continue routing with the current object.

  • Since Jenkins 2.147 and Jenkins LTS 2.138.3 return null will continue routing using a different approach, as the current object is not eligible for routing. This is useful if even the existence of an object should be hidden from users without the permission to access it. For Item, this is the difference between having no permissions, and having Item.DISCOVER.

  • Throwing exceptions will interrupt routing.

A good minimal example for this is AdministrativeMonitor. A more complex example is AbstractItem, as it incorporates two different permission checks, and different behaviors in each case.

If your plugin depends on Jenkins versions older than 2.147 or LTS 2.138.3, and you want to use the return null variant, please note that this behaves the same way as return this in Jenkins 2.146 and earlier. A possible alternative to achieve the same result can be seen here.