CSP: form-action

HTTP Content-Security-Policy (CSP) 的 form-action 指令能够限定当前页面中表单的提交地址。

在表单提交之后， form-action 指令是否应该阻止重定向仍有待讨论，各个浏览器对于此行为的实现也不尽相同（例如，Chrome 63会阻止重定向，而Firefox 57则不会）。

CSP version 2
Directive type Navigation directive
default-src fallback No. 未设定时允许任何值.

语法

form-action 策略允许设定一个或多个源：

Content-Security-Policy: form-action <source>;
Content-Security-Policy: form-action <source> <source>;

示例

meta标签配置

<meta http-equiv="Content-Security-Policy" content="form-action 'none'">

Apache服务器配置

<IfModule mod_headers.c>
Header set Content-Security-Policy "form-action 'none';
</IfModule>

Nginx配置

add_header Content-Security-Policy "form-action 'none';"

反例

将 <form> 元素的action设置为内联 JavaScript 会违反CSP规则。

<meta http-equiv="Content-Security-Policy" content="form-action 'none'">

<form action="javascript:alert('Foo')" id="form1" method="post">
  <input type="text" name="fieldName" value="fieldValue">
  <input type="submit" id="submit" value="submit">
</form>

// Error: Refused to send form data because it violates the following
// Content Security Policy directive: "form-action 'none'".

规范

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

参见