CSP: connect-src

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HTTP协议头部Content-Security-Policy (CSP)的connect-src 指令用于控制允许通过脚本接口加载的链接地址。其中受到影响的API如下: 

CSP version 1
Directive type Fetch directive
default-src fallback Yes. If this directive is absent, the user agent will look for the default-src directive.

Syntax

connect-src 可以设置一个或者多个源地址: 

Content-Security-Policy: connect-src <source>;
Content-Security-Policy: connect-src <source> <source>;

Sources

<source> can be one of the following:

<host-source>
Internet hosts by name or IP address, as well as an optional URL scheme and/or port number. The site's address may include an optional leading wildcard (the asterisk character, '*'), and you may use a wildcard (again, '*') as the port number, indicating that all legal ports are valid for the source.
Examples:
  • http://*.example.com: Matches all attempts to load from any subdomain of example.com using the http: URL scheme.
  • mail.example.com:443: Matches all attempts to access port 443 on mail.example.com.
  • https://store.example.com: Matches all attempts to access store.example.com using https:.
<scheme-source>
A schema such as 'http:' or 'https:'. The colon is required, single quotes shouldn't be used. You can also specify data schemas (not recommended).
  • data: Allows data: URIs to be used as a content source. This is insecure; an attacker can also inject arbitrary data: URIs. Use this sparingly and definitely not for scripts.
  • mediastream: Allows mediastream: URIs to be used as a content source.
  • blob: Allows blob: URIs to be used as a content source.
  • filesystem: Allows filesystem: URIs to be used as a content source.
'self'
Refers to the origin from which the protected document is being served, including the same URL scheme and port number. You must include the single quotes. Some browsers specifically exclude blob and filesystem from source directives. Sites needing to allow these content types can specify them using the Data attribute.
'unsafe-inline'
Allows the use of inline resources, such as inline <script> elements, javascript: URLs, inline event handlers, and inline <style> elements. You must include the single quotes.
'unsafe-eval'
Allows the use of eval() and similar methods for creating code from strings. You must include the single quotes.
'none'
Refers to the empty set; that is, no URLs match. The single quotes are required.
'nonce-<base64-value>'
A whitelist for specific inline scripts using a cryptographic nonce (number used once). The server must generate a unique nonce value each time it transmits a policy. It is critical to provide an unguessable nonce, as bypassing a resource’s policy is otherwise trivial. See unsafe inline script for an example. Specifying nonce makes a modern browser ignore 'unsafe-inline' which could still be set for older browsers without nonce support.
'<hash-algorithm>-<base64-value>'
A sha256, sha384 or sha512 hash of scripts or styles. The use of this source consists of two portions separated by a dash: the encryption algorithm used to create the hash and the base64-encoded hash of the script or style. When generating the hash, don't include the <script> or <style> tags and note that capitalization and whitespace matter, including leading or trailing whitespace. See unsafe inline script for an example. In CSP 2.0 this applied only to inline scripts. CSP 3.0 allows it in the case of script-src for external scripts.
'strict-dynamic'
The strict-dynamic source expression specifies that the trust explicitly given to a script present in the markup, by accompanying it with a nonce or a hash, shall be propagated to all the scripts loaded by that root script. At the same time, any whitelist or source expressions such as 'self' or 'unsafe-inline' will be ignored. See script-src for an example.

Examples

Violation cases

给定如下CSP头部: 

Content-Security-Policy: connect-src https://example.com/

如下的连接请求会被阻塞且不会加载: 

<a ping="https://not-example.com">

<script>
  var xhr = new XMLHttpRequest(); 
  xhr.open('GET', 'https://not-example.com/'); 
  xhr.send();

  var ws = new WebSocket("https://not-example.com/");

  var es = new EventSource("https://not-example.com/"); 

  navigator.sendBeacon("https://not-example.com/", { ... });
</script>

Specifications

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

Browser compatibility

FeatureChromeEdgeFirefoxInternet ExplorerOperaSafari
Basic support2514231 No157
FeatureAndroid webviewChrome for AndroidEdge mobileFirefox for AndroidOpera AndroidiOS SafariSamsung Internet
Basic support Yes Yes ?23 ?7.1 Yes

1. Prior to Firefox 50, ping attributes of <a> elements weren't covered by connect-src.

Compatibility notes

  • Prior to Firefox 23, xhr-src was used in place of the connect-src directive and only restricted the use of XMLHttpRequest.

See also

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