介绍内容安全策略

内容安全策略 (CSP)  是一个附加的安全层，用于帮助检测和缓解某些类型的攻击，包括跨站脚本 (XSS) 和数据注入等攻击。 这些攻击可用于实现从数据窃取到网站破坏或作为恶意软件分发版本等用途。

CSP被设计成向后兼容；不支持的浏览器依然可以运行使用了它的服务器页面，反之亦然。不支持CSP的浏览器会忽略它，像平常一样运行，默认对网页内容使用标准的同源策略。如果网站不提供CSP头部，浏览器同样会使用标准的同源策略。

Enabling CSP is as easy as configuring your web server to return the Content-Security-Policy HTTP header. (Prior to Firefox 23, the X-Content-Security-Policy header was used). See Using Content Security Policy for details on how to configure and enable CSP.

Mitigating cross site scripting

A primary goal of CSP is to mitigate and report XSS attacks. XSS attacks exploit the browser's trust of the content received from the server. Malicious scripts are executed by the victim's browser because the browser trusts the source of the content, even when it's not coming from where it seems to be coming from.

CSP makes it possible for server administrators to reduce or eliminate the vectors by which XSS can occur by specifying the domains that the browser should consider to be valid sources of executable scripts. A CSP compatible browser will then only execute scripts loaded in source files received from those whitelisted domains, ignoring all other script (including inline scripts and event-handling HTML attributes).

As an ultimate form of protection, sites that want to never allow scripts to be executed can opt to globally disallow script execution.

Mitigating packet sniffing attacks

In addition to restricting the domains from which content can be loaded, the server can specify which protocols are allowed to be used; for example (and ideally, from a security standpoint), a server can specify that all content be loaded using HTTPS.

See also

• Using Content Security Policy
• CSP policy directives
• Using CSP violation reports

Specification

• Content Security Policy 1.1 (Editor's Draft)
• Content Security Policy 1.0 (Candidate Recommendation)