CSP: base-uri

HTTP 协议 Content-Security-Policy 首部字段中的 base-uri 指令限制了可以应用于一个文档的 <base> 元素的 URL。假如指令值为空，那么任何 URL 都是允许的。如果指令不存在，那么用户代理会使用 <base> 元素中的值。

CSP version	2
Directive type	Document directive
`default-src` fallback	No. Not setting this allows anything.

语法

base-uri 安全策略可以设置一个或多个源：

Content-Security-Policy: base-uri <source>;
Content-Security-Policy: base-uri <source> <source>;

源

<source> can be any one of the values listed in CSP Source Values.

Note that this same set of values can be used in all fetch directives (and a number of other directives).

示例

Meta tag 配置

<meta http-equiv="Content-Security-Policy" content="base-uri 'self'">

Apache 配置

<IfModule mod_headers.c>
Header set Content-Security-Policy "base-uri 'self';
</IfModule>

Nginx 配置

add_header Content-Security-Policy "base-uri 'self';"

违犯策略的案例

假如你的域名不是 example.com，那么将 <base> 元素的 href 属性值设置成 example.com 会违犯 CSP 策略。

<meta http-equiv="Content-Security-Policy" content="base-uri 'self'">
<base href="http://example.com/">

// Error: Refused to set the document's base URI to 'http://example.com/'
// because it violates the following Content Security Policy
// directive: "base-uri 'self'"

规范

Specification	Status	Comment
Content Security Policy Level 3 base-uri	Working Draft	No changes.
Content Security Policy Level 2 base-uri	Recommendation	Initial definition.

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