Détail du CWE-942

The product uses a cross-domain policy file that includes domains that should not be trusted.

A cross-domain policy file ("crossdomain.xml" in Flash and "clientaccesspolicy.xml" in Silverlight) defines a list of domains from which a server is allowed to make cross-domain requests. When making a cross-domain request, the Flash or Silverlight client will first look for the policy file on the target server. If it is found, and the domain hosting the application is explicitly allowed to make requests, the request is made.

Therefore, if a cross-domain policy file includes domains that should not be trusted, such as when using wildcards, then the application could be attacked by these untrusted domains.

An overly permissive policy file allows many of the same attacks seen in Cross-Site Scripting (CWE-79). Once the user has executed a malicious Flash or Silverlight application, they are vulnerable to a variety of attacks. The attacker could transfer private information, such as cookies that may include session information, from the victim's machine to the attacker. The attacker could send malicious requests to a web site on behalf of the victim, which could be especially dangerous to the site if the victim has administrator privileges to manage that site.

In many cases, the attack can be launched without the victim even being aware of it.

Modes d'introduction

Implementation
Architecture and Design : COMMISSION: This weakness refers to an incorrect design related to an architectural security tactic.

Plateformes applicables

Langue

Class: Not Language-Specific (Undetermined)

Technologies

Class: Web Based (Undetermined)

Conséquences courantes

Exemples observés

Mesures d’atténuation potentielles

Phases : Architecture and Design
Avoid using wildcards in the cross-domain policy file. Any domain matching the wildcard expression will be implicitly trusted, and can perform two-way interaction with the target server.
Phases : Architecture and Design // Operation
For Flash, modify crossdomain.xml to use meta-policy options such as 'master-only' or 'none' to reduce the possibility of an attacker planting extraneous cross-domain policy files on a server.
Phases : Architecture and Design // Operation
For Flash, modify crossdomain.xml to use meta-policy options such as 'master-only' or 'none' to reduce the possibility of an attacker planting extraneous cross-domain policy files on a server.

Méthodes de détection

Automated Static Analysis

Automated static analysis, commonly referred to as Static Application Security Testing (SAST), can find some instances of this weakness by analyzing source code (or binary/compiled code) without having to execute it. Typically, this is done by building a model of data flow and control flow, then searching for potentially-vulnerable patterns that connect "sources" (origins of input) with "sinks" (destinations where the data interacts with external components, a lower layer such as the OS, etc.)
Efficacité : High

Notes de cartographie des vulnérabilités

Justification : This CWE entry is at the Variant level of abstraction, which is a preferred level of abstraction for mapping to the root causes of vulnerabilities.
Commentaire : Carefully read both the name and description to ensure that this mapping is an appropriate fit. Do not try to 'force' a mapping to a lower-level Base/Variant simply to comply with this preferred level of abstraction.

Références

REF-943

Setting a crossdomain.xml file for HTTP streaming
Apurva Udaykumar.
https://web.archive.org/web/20121124184922/http://www.adobe.com/devnet/adobe-media-server/articles/cross-domain-xml-for-streaming.html

REF-944

Cross-domain policy for Flash movies
Adobe.
http://kb2.adobe.com/cps/142/tn_14213.html

REF-945

HTTP Communication and Security with Silverlight
Microsoft Corporation.
https://learn.microsoft.com/en-us/previous-versions/windows/silverlight/dotnet-windows-silverlight/cc838250(v=vs.95)?redirectedfrom=MSDN

REF-946

Network Security Access Restrictions in Silverlight
Microsoft Corporation.
https://learn.microsoft.com/en-us/previous-versions/windows/silverlight/dotnet-windows-silverlight/cc645032(v=vs.95)

REF-947

Analyzing the Crossdomain Policies of Flash Applications
Dongseok Jang, Aishwarya Venkataraman, G. Michael Sawka, Hovav Shacham.
http://cseweb.ucsd.edu/~hovav/dist/crossdomain.pdf

Soumission

Modifications