内容安全策略 (CSP) 是一个额外的安全层,用于检测并削弱某些特定类型的攻击,包括跨站脚本 (XSS) 和数据注入攻击等。无论是数据盗取、网站内容污染还是散发恶意软件,这些攻击都是主要的手段。
内容源
大多数策略指令需要一个或多个内容源。内容源是一串表明内容可能从哪里加载的字符串。
源列表
源列表是一个字符串,指定了一个或多个互联网主机(通过主机名或 IP 地址),和可选的 URL 协议和/或端口号。站点地址可以包含可选的通配符前缀 (星号, '*'
),端口号也可以使用通配符 (同样是 '*'
) 来表明所有合法端口都是有效来源。主机通过空格分隔。
有效的主机表达式包括:
-
http://*.foo.com
-
匹配所有使用
http:
协议加载 foo.com 任何子域名的尝试。
mail.foo.com:443
- 匹配所有访问 mail.foo.com 的 443 端口 的尝试。 https://store.foo.com
-
匹配所有使用
https:
协议访问 store.foo.com 的尝试。
如果端口号没有被指定,浏览器会使用指定协议的默认端口号。如果协议没有被指定,浏览器会使用访问该文档时的协议。
关键字
有一些关键字可以用来描述某类特别的内容源。它们是:
- 代表空集;即不匹配任何 URL。两侧单引号是必须的。
- 代表和文档同源,包括相同的 URL 协议和端口号。两侧单引号是必须的。
-
允许使用内联资源,如内联的
<script>
元素、javascript:
URL、内联的事件处理函数和内联的<style>
元素。两侧单引号是必须的。 -
允许使用
eval()
等通过字符串创建代码的方法。两侧单引号是必须的。
'none'
'self'
'unsafe-inline'
'unsafe-eval'
例如,您可以指定内容能从文档源和 trustedscripts.foo.com 加载:
Content-Security-Policy: default-src 'self' trustedscripts.foo.com
数据
data:
URI 是不安全的,如果它们被允许成为脚本来源,则会使您的网站有跨站脚本攻击风险。
-
data:
-
允许
data:
URI 作为内容来源。这是不安全的,因为攻击者可以精心构造 data: URI 来攻击。请谨慎地使用这个源,并确保不要用于脚本。
mediastream:
-
允许
mediastream:
URI 作为内容源。
Content-Security-Policy: default-src 'self'; img-src 'self' data:; media-src mediastream:
CSP 被设计成完全向后兼容(除CSP2 在向后兼容有明确提及的不一致; 更多细节查看这里 章节1.1)。不支持CSP的浏览器也能与实现了CSP的服务器正常合作,反之亦然:不支持 CSP 的浏览器只会忽略它,如常运行,默认为网页内容使用标准的同源策略。如果网站不提供 CSP 头部,浏览器也使用标准的同源策略。
为使CSP可用, 你需要配置你的网络服务器返回 Content-Security-Policy
HTTP头部 ( 有时你会看到一些关于X-Content-Security-Policy
头部的提法, 那是旧版本,你无须再如此指定它)。
除此之外, <meta>
元素也可以被用来配置该策略, 例如
<meta http-equiv="Content-Security-Policy" content="default-src 'self'; img-src https://*; child-src 'none';">
示例:常见用例
这一部分提供了一些常用的安全策略方案示例。
示例 1
一个网站管理者想要所有内容均来自站点的同一个源 (不包括其子域名)
Content-Security-Policy: default-src 'self'
示例 2
一个网站管理者允许内容来自信任的域名及其子域名 (域名不必须与CSP设置所在的域名相同)
Content-Security-Policy: default-src 'self' *.trusted.com
示例 3
一个网站管理者允许网页应用的用户在他们自己的内容中包含来自任何源的图片, 但是限制音频或视频需从信任的资源提供者(获得),所有脚本必须从特定主机服务器获取可信的代码.
Content-Security-Policy: default-src 'self'; img-src *; media-src media1.com media2.com; script-src userscripts.example.com
在这里,各种内容默认仅允许从文档所在的源获取, 但存在如下例外:
- 图片可以从任何地方加载(注意 "*" 通配符)。
- 多媒体文件仅允许从 media1.com 和 media2.com 加载(不允许从这些站点的子域名)。
- 可运行脚本仅允许来自于userscripts.example.com。
示例 4
一个线上银行网站的管理者想要确保网站的所有内容都要通过SSL方式获取,以避免攻击者窃听用户发出的请求。
Content-Security-Policy: default-src https://onlinebanking.jumbobank.com
该服务器仅允许通过HTTPS方式并仅从onlinebanking.jumbobank.com域名来访问文档。
示例 5
一个在线邮箱的管理者想要允许在邮件里包含HTML,同样图片允许从任何地方加载,但不允许JavaScript或者其他潜在的危险内容(从任意位置加载)。
Content-Security-Policy: default-src 'self' *.mailsite.com; img-src *
注意这个示例并未指定script-src
。在此CSP示例中,站点通过 default-src
指令的对其进行配置,这也同样意味着脚本文件仅允许从原始服务器获取。
浏览器兼容性
Desktop | Mobile | ||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Chrome | Edge | Firefox | Internet Explorer | Opera | Safari | Android webview | Chrome for Android | Edge Mobile | Firefox for Android | Opera for Android | iOS Safari | Samsung Internet | |
Content-Security-Policy | Full support25 打开 | Full support14 | Full support23 打开 | Full support10 打开 | Full support15 | Full support7 打开 | Full supportYes | Full supportYes | Full supportYes | Full support23 | ? | Full support7.1 打开 | Full supportYes |
base-uri | Full support40 | No supportNo | Full support35 | No supportNo | Full support27 | Full support10 | Full supportYes | Full supportYes | No supportNo | Full support35 | ? | Full support9.3 | Full supportYes |
block-all-mixed-content | Full supportYes | ? | Full support48 | No supportNo | Full supportYes | ? | Full supportYes | Full supportYes | ? | Full support48 | ? | ? | Full supportYes |
child-src
| Full support40 | Full support15 | Full support45 | No supportNo | Full support27 | Full support10 | Full supportYes | Full supportYes | No supportNo | Full support45 | ? | Full support9.3 | Full supportYes |
connect-src | Full support25 | Full support14 | Full support23 打开 | No supportNo | Full support15 | Full support7 | Full supportYes | Full supportYes | ? | Full support23 | ? | Full support7.1 | Full supportYes |
default-src | Full support25 | Full support14 | Full support23 | No supportNo | Full support15 | Full support7 | Full supportYes | Full supportYes | ? | Full support23 | ? | Full support7.1 | Full supportYes |
disown-opener
| No supportNo | No supportNo | No supportNo | No supportNo | No supportNo | No supportNo | No supportNo | No supportNo | No supportNo | No supportNo | No supportNo | No supportNo | No supportNo |
font-src | Full support25 | Full support14 | Full support23 | No supportNo | Full support15 | Full support7 | Full supportYes | Full supportYes | ? | Full support23 | ? | Full support7.1 | Full supportYes |
form-action | Full support40 | Full support15 | Full support36 | No supportNo | Full support27 | Full support10 | Full supportYes | Full supportYes | No supportNo | Full support36 | ? | Full support9.3 | Full supportYes |
frame-ancestors | Full support40 | Full support15 | Full support33 打开 | No supportNo | Full support26 | Full support10 | ? | Full supportYes | No supportNo | Full support33 打开 | ? | Full support9.3 | Full supportYes |
frame-src | Full support25 | Full support14 | Full support23 | No supportNo | Full support15 | Full support7 | Full supportYes | Full supportYes | ? | Full support23 | ? | Full support7.1 | Full supportYes |
img-src | Full support25 | Full support14 | Full support23 | No supportNo | Full support15 | Full support7 | Full supportYes | Full supportYes | ? | Full support23 | ? | Full support7.1 | Full supportYes |
manifest-src | Full supportYes | No supportNo | Full support41 | No supportNo | Full supportYes | No supportNo | Full supportYes | Full supportYes | No supportNo | Full support41 | ? | No supportNo | Full supportYes |
media-src | Full support25 | Full support14 | Full support23 | No supportNo | Full support15 | Full support7 | Full supportYes | Full supportYes | ? | Full support23 | ? | Full support7.1 | Full supportYes |
navigation-to
| No supportNo | No supportNo | No supportNo | No supportNo | No supportNo | No supportNo | No supportNo | No supportNo | No supportNo | No supportNo | No supportNo | No supportNo | No supportNo |
object-src | Full support25 | Full support14 | Full support23 | No supportNo | Full support15 | Full support7 | Full supportYes | Full supportYes | ? | Full support23 | ? | Full support7.1 | Full supportYes |
plugin-types | Full support40 | Full support15 | No supportNo 打开 | No supportNo | Full support27 | Full support10 | Full supportYes | Full supportYes | No supportNo | No supportNo | ? | Full support9.3 | Full supportYes |
referrer
| No support33 — 56 | No supportNo | Full support37 打开 | No supportNo | No support? — 43 | No supportNo | No support33 — 56 | No support33 — 56 | No supportNo | Full support37 打开 | No support? — 43 | No supportNo | Full supportYes |
report-sample
| Full support59 | ? | ? | ? | Full support46 | ? | Full support59 | Full support59 | ? | ? | Full support46 | ? | Full support7.0 |
report-to | No supportNo | No supportNo | No supportNo | No supportNo | No supportNo | No supportNo | No supportNo | No supportNo | No supportNo | No supportNo | No supportNo | No supportNo | No supportNo |
report-uri
| Full support25 | Full support14 | Full support23 | No supportNo | Full support15 | Full support7 | Full supportYes | Full supportYes | ? | Full support23 | ? | Full support7.1 | Full supportYes |
require-sri-for
| Full support54 | No supportNo | Full support49 打开 | No supportNo | Full support41 | No supportNo | Full support54 | Full support54 | No supportNo | Full support49 打开 | Full support41 | No supportNo | Full support6.0 |
sandbox | Full support25 | Full support14 | Full support50 | Full support10 | Full support15 | Full support7 | Full supportYes | Full supportYes | ? | Full support50 | ? | Full support7.1 | Full supportYes |
script-src | Full support25 | Full support14 | Full support23 | No supportNo | Full support15 | Full support7 | Full supportYes | Full supportYes | ? | Full support23 | ? | Full support7.1 | Full supportYes |
strict-dynamic | Full support52 | No supportNo | Full support52 | No supportNo | Full support39 | No supportNo | Full support52 | Full support52 | No supportNo | No supportNo | Full support39 | No supportNo | Full support6.0 |
style-src | Full support25 | Full support14 | Full support23 | No supportNo | Full support15 | Full support7 | Full supportYes | Full supportYes | ? | Full support23 | ? | Full support7.1 | Full supportYes |
upgrade-insecure-requests | Full support43 | No supportNo 打开 | Full support42 | No supportNo | Full support30 | No supportNo | Full support43 | Full support43 | No supportNo | Full support42 | Full support30 | No supportNo | Full support4.0 |
worker-src | Full support59 打开 | No supportNo | Full support58 | No supportNo | Full support48 | No supportNo | Full support59 打开 | Full support59 打开 | No supportNo | Full support58 | Full support48 | No supportNo | Full support7.0 |