Rest uses standard HTTP (Get, Put, Delete) style permissions methods, but these are not necessarily correlated generally with back end programs. Strict interpretation of HTTP get methods means that these HTTP Get services should not be used to delete information on the server, but there is no access control mechanism to back up this logic. This means that unless the services are properly ACL'd and the application's service implementation are following these guidelines then an HTTP request can easily execute a delete or update on the server side. The attacker identifies a HTTP Get URL such as http://victimsite/updateOrder, which calls out to a program to update orders on a database or other resource. The URL is not idempotent so the request can be submitted multiple times by the attacker, additionally, the attacker may be able to exploit the URL published as a Get method that actually performs updates (instead of merely retrieving data). This may result in malicious or inadvertent altering of data on the server.
Likelihood Of Attack
The table(s) below shows the other attack patterns and high level categories that are related to this attack pattern. These relationships are defined as ChildOf, ParentOf, MemberOf and give insight to similar items that may exist at higher and lower levels of abstraction. In addition, relationships such as CanFollow, PeerOf, and CanAlsoBe are defined to show similar attack patterns that the user may want to explore.
Relevant to the view "Mechanisms of Attack" (CAPEC-1000)
Standard Attack Pattern - A standard level attack pattern in CAPEC is focused on a specific methodology or technique used in an attack. It is often seen as a singular piece of a fully executed attack. A standard attack pattern is meant to provide sufficient details to understand the specific technique and how it attempts to accomplish a desired goal. A standard level attack pattern is a specific type of a more abstract meta level attack pattern.
Meta Attack Pattern - A meta level attack pattern in CAPEC is a decidedly abstract characterization of a specific methodology or technique used in an attack. A meta attack pattern is often void of a specific technology or implementation and is meant to provide an understanding of a high level approach. A meta level attack pattern is a generalization of related group of standard level attack patterns. Meta level attack patterns are particularly useful for architecture and design level threat modeling exercises.
The attacker needs to be able to identify HTTP Get URLs. The Get methods must be set to call applications that perform operations other than get such as update and delete.
It is relatively straightforward to identify an HTTP Get method that changes state on the server side and executes against an over-privileged system interface
The table below specifies different individual consequences associated with the attack pattern. The Scope identifies the security property that is violated, while the Impact describes the negative technical impact that arises if an adversary succeeds in their attack. The Likelihood provides information about how likely the specific consequence is expected to be seen relative to the other consequences in the list. For example, there may be high likelihood that a pattern will be used to achieve a certain impact, but a low likelihood that it will be exploited to achieve a different impact.
Design: Enforce principle of least privilege
Implementation: Ensure that HTTP Get methods only retrieve state and do not alter state on the server side
Implementation: Ensure that HTTP methods have proper ACLs based on what the functionality they expose
The HTTP Get method is designed to retrieve resources and not to alter the state of the application or resources on the server side. However, developers can easily code programs that accept a HTTP Get request that do in fact create, update or delete data on the server. Both Flickr (http://www.flickr.com/services/api/flickr.photosets.delete.html) and del.icio.us (http://del.icio.us/api/posts/delete) have implemented delete operations using standard HTTP Get requests. These HTTP Get methods do delete data on the server side, despite being called from Get which is not supposed to alter state.
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Page Last Updated or Reviewed:
July 31, 2018
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