Testing for Privilege escalation (OWASP-AZ-003)
This article is part of the OWASP Testing Guide v3. The entire OWASP Testing Guide v3 can be downloaded here.
This is a draft of a section of the new Testing Guide v3
This section describes the issue of escalating privileges from one stage to another. During this phase the tester should verify that is not possible for a user to modify his privileges/roles inside the application that could allow a privilege escalation.
Description of the Issue
Privilege escalation occurs when a user gets to access more resources than is normally allowed when it should have been protected from the application. This is usually conducted from a flaw in the application. The result is that the application performs actions with more privileges than intended by the application developer or system administrator.
The degree of the escalation depends on which privileges the attacker is authorized to possess and which privileges can be obtained in a successful attack. For example, a programming error that permits a user to gain extra privilege after successful authentication limits the degree of escalation because the user is already authorized to hold some privilege. Likewise, a remote attacker gaining superuser privilege without any authentication presents a greater degree of escalation.
Black Box testing and example
Testing for role/privilege manipulation
In every point of the application where a user can create information in the DB ( a payment, add a contact, send a message), to receive information (statement of account, order details, etc.) o delete information (drop users, messages, etc.), it is necessary to record that functionality. The tester should try to access as another user to verify for example if it is possible to access a functionality that should not permicted by the user's role.
The following HTTP POST permits to the user that belongs to grp001 to access to order #0001:
POST /path/viewMyOrder.jsp HTTP/1.1 Host: www.example.com [others HTTP Headers]
Verify if a user that not belongs to grp001 can modify the value of the parameters ‘gruppoID’ and ‘ordineID’ to gain the access to that reserrved data.
The following server's answer shows an Hidden field in the HTML released to the user after a successful authentication.
HTTP/1.1 200 OK Server: Netscape-Enterprise/6.0 Date: Wed, 1 Apr 2006 13:51:20 GMT Set-Cookie: USER=aW78ryrGrTWs4MnOd32Fs51yDqp; path=/; domain=www.example.com Set-Cookie: SESSION=k+KmKeHXTgDi1J5fT7Zz; path=/; domain= www.example.com Cache-Control: no-cache Pragma: No-cache Content-length: 247 Content-Type: text/html Expires: Thu, 01 Jan 1970 00:00:00 GMT Connection: close <form name=“autoriz" method="POST" action = “visual.jsp"> <input type="hidden" name="profilo" value="SistemiInf1"> <body onload="document.forms.autoriz.submit()"> </td> </tr>
What if the tester modifies the value of the variable "profilo" with “SistemiInf9”? It is possible to become administrator?
In an environment in which the server sends an error message contained as value in a specific parameter in a set of answer's codes, as the following:
@0`1`3`3``0`UC`1`Status`OK`SEC`5`1`0`ResultSet`0`PVValido`-1`0`0` Notifications`0`0`3`Command Manager`0`0`0` StateToolsBar`0`0`0` StateExecToolBar`0`0`0`FlagsToolBar`0
The server gives an implicit trust to the user. It belives that the user will answer with the above message closing the session. In this condition, verify that modifying the parameters value it is not possible to escalate privileges. For example modifying the `PVValido` value from '-1' to '0' (no error conditions) it is possible to authenticate as administrator to the server.
The tester should verifies to execute a successfull privilege escalation
Gray Box testing and example
Testing for Topic X vulnerabilities:
- OWASP WebScarab