CSP: script-src

HTTP Content-Security-Policy (CSP) script-src 는 자바스크립트트에 대한 검증된 출처를 지정합니다. 여기에는 <script> 요소에서 직접 호출한 URL뿐만 아니라,  인라인 스크립트  이벤트 핸들러(onclick) 및 스크립트를 실행할 수 있는  XSLT stylesheets 가 포함됩니다.

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

하나 이상의 출처가 script-src 정책에 의해서 허용될 수 있습니다:

Content-Security-Policy: script-src <source>;
Content-Security-Policy: script-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:.
  • *.example.com: Matches all attempts to load from any subdomain of example.com using the current protocol.
<scheme-source>
A scheme such as http: or https:. The colon is required. Unlike other values below, single quotes shouldn't be used. You can also specify data schemes (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-eval'
Allows the use of eval() and similar methods for creating code from strings. You must include the single quotes.
'unsafe-hashes'
Allows enabling specific inline event handlers. If you only need to allow inline event handlers and not inline <script> elements or javascript: URLs, this is a safer method than using the unsafe-inline expression.
'unsafe-inline'
Allows the use of inline resources, such as inline <script> elements, javascript: URLs, inline event handlers, and inline <style> elements. The single quotes are required.
'none'
Refers to the empty set; that is, no URLs match. The single quotes are required.
'nonce-<base64-value>'
An allow-list 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.

Note: The CSP nonce source can only be apply nonceable elements (e.g. as the <img> element has no nonce attribute, there is no way to associate it with this CSP source).

'<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 allow-list or source expressions such as 'self' or 'unsafe-inline' are ignored. See script-src for an example.
'report-sample'
Requires a sample of the violating code to be included in the violation report.

'report-sample'
 Report에 위반 코드 샘플을 포함시키려면 이 항목을 추가 해야 합니다.

예제

Violation case

주어진 CSP 헤더:

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

아래 스크립트가 차단되어서 로드 또는 실행되지 않습니다:

<script src="https://not-example.com/js/library.js"></script>

인라인 스크립트도 실행되지 않습니다:

<button id="btn" onclick="doSomething()">

addEventListener를 호출하는 것으로 대체해야 합니다.:

document.getElementById("btn").addEventListener('click', doSomething);

안전하지 않은 인라인 스크립트

Note: 인라인 스타일 및 인라인 스크립트를 허용하지 않는 것이 CSP가 제공하는 가장 큰 보안 이점 중 하나 입니다. 그러나, 인라인 스크립트 및 스타일을 사용해야만 한다면 몇가지 방법을 제공합니다.

인라인 스크립트 및 인라인 이벤트 핸들러를 허용하려면, 'unsafe-inline',  인라인 태그에 정의한 값과 동일한 nonce-source 또는 hash-source를 지정할 수 있습니다.

Content-Security-Policy: script-src 'unsafe-inline';

위의 CSP는 <script> 태그를 허용합니다

<script>
  var inline = 1;
</script>

nonce-source를 사용하면 특정 인라인 스크립트 태그만 허용 할 수 있습니다:

Content-Security-Policy: script-src 'nonce-2726c7f26c'

<script> 태그에 동일한 nonce를 설정해야 합니다 :

<script nonce="2726c7f26c">
  var inline = 1;
</script>

또는, 인라인 스크립트에서 해시를 설정할 수 도 있습니다. CSP는 sha256, sha384 and sha512를 지원합니다.

Content-Security-Policy: script-src 'sha256-B2yPHKaXnvFWtRChIbabYmUBFZdVfKKXHbWtWidDVF8='

해시를 생성할 때에는 <script> 태그를 포함하지 말고, 대소문자, 태그의 앞뒤 공백이 포함되어야 하는 것을 유의해주십시요.

<script>var inline = 1;</script>

안전하지 않은 eval 표현식

'unsafe-eval' 출처 표현식은 문자열에서 코드를 생성하는 여러 스크립트 실행 메소드를 제어합니다.  만약'unsafe-eval' 이  script-src 에 정의되어 있지 않으면, 아래믜 명령어는 차단되며 아무런 효과가 일어나지 않습니다.

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. For example, a policy such as script-src 'strict-dynamic' 'nonce-R4nd0m' https://whitelisted.com/ would allow loading of a root script with <script nonce="R4nd0m" src="https://example.com/loader.js">  and propogate that trust to any script loaded by loader.js, but disallow loading scripts from https://whitelisted.com/ unless accompanied by a nonce or loaded from a trusted script.

script-src 'strict-dynamic' 'nonce-someNonce'

Or

script-src 'strict-dynamic' 'sha256-base64EncodedHash'

It is possible to deploy strict-dynamic in a backwards compatible way, without requiring user-agent sniffing.
The policy:

script-src 'unsafe-inline' https: 'nonce-abcdefg' 'strict-dynamic'

will act like'unsafe-inline' https: in browsers that support CSP1, https: 'nonce-abcdefg' in browsers that support CSP2, and 'nonce-abcdefg' 'strict-dynamic' in browsers that support CSP3.

Specifications

See also