Trust of System Event Data

Description

Events are a messaging system which may provide control data to programs listening for events. Events often do not have any type of authentication framework to allow them to be verified from a trusted source. Any application, in Windows, on a given desktop can send a message to any window on the same desktop. There is no authentication framework for these messages. Therefore, any message can be used to manipulate any process on the desktop if the process does not check the validity and safeness of those messages.

Demonstrations

The following examples help to illustrate the nature of this weakness and describe methods or techniques which can be used to mitigate the risk.

Note that the examples here are by no means exhaustive and any given weakness may have many subtle varieties, each of which may require different detection methods or runtime controls.

Example One

This example code prints out secret information when an authorized user activates a button:

public void actionPerformed(ActionEvent e) {
  if (e.getSource() == button) {
    System.out.println("print out secret information");
  }
}

This code does not attempt to prevent unauthorized users from activating the button. Even if the button is rendered non-functional to unauthorized users in the application UI, an attacker can easily send a false button press event to the application window and expose the secret information.

See Also