CWE-650: Trusting HTTP Permission Methods on the Server Side
Trusting HTTP Permission Methods on the Server Side
Weakness ID: 650 (Weakness Variant)
Status: Incomplete
Description
Description Summary
The server contains a protection mechanism that assumes that any URI that is accessed using HTTP GET will not cause a state change to the associated resource. This might allow attackers to bypass intended access restrictions and conduct resource modification and deletion attacks, since some applications allow GET to modify state.
Extended Description
An application may disallow the HTTP requests to perform DELETE, PUT and POST operations on the resource representation, believing that it will be enough to prevent unintended resource alterations. Even though the HTTP GET specification requires that GET requests should not have side effects, there is nothing in the HTTP protocol itself that prevents the HTTP GET method from performing more than just query of the data. For instance, it is a common practice with REST based Web Services to have HTTP GET requests modifying resources on the server side. Whenever that happens however, the access control needs to be properly enforced in the application. No assumptions should be made that only HTTP DELETE, PUT, and POST methods have the power to alter the representation of the resource being accessed in the request.
Time of Introduction
Architecture and Design
Implementation
Operation
Applicable Platforms
Languages
All
Common Consequences
Scope
Effect
Access Control
Technical Impact: Gain privileges / assume
identity
An attacker could escalate privileges.
Integrity
Technical Impact: Modify application
data
An attacker could modify resources.
Confidentiality
Technical Impact: Read application
data
An attacker could obtain sensitive information.
Likelihood of Exploit
High
Enabling Factors for Exploitation
The application allows HTTP access to resources.
The application is not properly configured to enforce access controls
around the resources accessible via HTTP.
Observed Examples
Reference
Description
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.
Potential Mitigations
Configure ACLs on the server side to ensure that proper level of
access control is defined for each accessible resource representation.
Do not make an assumption that only HTTP PUT, DELETE or POST methods
can modify resources, since HTTP GET method may do the same.
Description
