CWE-942 过度许可的跨域白名单

Overly Permissive Cross-domain Whitelist

结构: Simple

Abstraction: Variant

状态: Incomplete

被利用可能性: unkown

基本描述

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

扩展描述

A cross-domain policy file ("crossdomain.xml" in Flash and "clientaccesspolicy.xml" in Silverlight) defines a whitelist 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.

相关缺陷

• cwe_Nature: ChildOf cwe_CWE_ID: 284 cwe_View_ID: 1000 cwe_Ordinal: Primary

• cwe_Nature: ChildOf cwe_CWE_ID: 284 cwe_View_ID: 699 cwe_Ordinal: Primary

• cwe_Nature: ChildOf cwe_CWE_ID: 183 cwe_View_ID: 1000

• cwe_Nature: CanPrecede cwe_CWE_ID: 668 cwe_View_ID: 1000

适用平台

Language: {'cwe_Class': 'Language-Independent', 'cwe_Prevalence': 'Undetermined'}

Paradigm: {'cwe_Name': 'Web Based', 'cwe_Prevalence': 'Undetermined'}

常见的影响

范围	影响	注释
['Confidentiality', 'Integrity', 'Availability', 'Access Control']	['Execute Unauthorized Code or Commands', 'Bypass Protection Mechanism', 'Read Application Data', 'Varies by Context']	An attacker may be able to bypass the web browser's same-origin policy. An attacker can exploit the weakness to manipulate or steal cookies, create requests that can be mistaken for those of a valid user, compromise confidential information, or execute malicious code on the end user systems for a variety of nefarious purposes. Other damaging attacks include the disclosure of end user files, installation of Trojan horse programs, redirecting the user to some other page or site, running ActiveX controls (under Microsoft Internet Explorer) from sites that a user perceives as trustworthy, and modifying presentation of content.

可能的缓解方案

Architecture and Design

策略: Attack Surface Reduction

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.

['Architecture and Design', 'Operation']

策略: Environment Hardening

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.

['Architecture and Design', 'Operation']

策略: Attack Surface Reduction

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.

示例代码

例

These cross-domain policy files mean to allow Flash and Silverlight applications hosted on other domains to access its data:

Flash crossdomain.xml :

bad XML

Silverlight clientaccesspolicy.xml :

bad XML

These entries are far too permissive, allowing any Flash or Silverlight application to send requests. A malicious application hosted on any other web site will be able to send requests on behalf of any user tricked into executing it.

分析过的案例

标识	说明	链接
CVE-2012-2292	Product has a Silverlight cross-domain policy that does not restrict access to another application, which allows remote attackers to bypass the Same Origin Policy.	https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2012-2292
CVE-2014-2049	The default Flash Cross Domain policies in a product allows remote attackers to access user files.	https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2014-2049
CVE-2007-6243	Chain: Adobe Flash Player does not sufficiently restrict the interpretation and usage of cross-domain policy files, which makes it easier for remote attackers to conduct cross-domain and cross-site scripting (XSS) attacks.	https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2007-6243
CVE-2008-4822	Chain: Adobe Flash Player and earlier does not properly interpret policy files, which allows remote attackers to bypass a non-root domain policy.	https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2008-4822
CVE-2010-3636	Chain: Adobe Flash Player does not properly handle unspecified encodings during the parsing of a cross-domain policy file, which allows remote web servers to bypass intended access restrictions via unknown vectors.	https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2010-3636

引用

• REF-943 Setting a crossdomain.xml file for HTTP streaming

• REF-944 Cross-domain policy for Flash movies

• REF-945 HTTP Communication and Security with Silverlight

• REF-946 Network Security Access Restrictions in Silverlight

• REF-947 Analyzing the Crossdomain Policies of Flash Applications

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