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| − | Content Security Policy (CSP) is an important standard by the W3C that is aimed to prevent a broad range of content injection attacks such as cross-site scripting (XSS).
| + | __NOTOC__ |
| | + | <div style="width:100%;height:160px;border:0,margin:0;overflow: hidden;">[[File:Cheatsheets-header.jpg|link=]]</div> |
| | | | |
| − | = Introduction =
| + | The Cheat Sheet Series project has been moved to [https://github.com/OWASP/CheatSheetSeries GitHub]! |
| | | | |
| − | Content Security Policy (CSP) is an effective "defense in depth" technique to be used against content injection attacks. It is a declarative policy that informs the user agent what are valid sources to load from.
| + | Please visit [https://cheatsheetseries.owasp.org/cheatsheets/Content_Security_Policy_Cheat_Sheet.html Content Security Policy Cheat Sheet] to see the latest version of the cheat sheet. |
| − | | |
| − | Since, it was introduced in Firefox version 4 by Mozilla, it has been adopted as a standard, and grown in adoption and capabilities.
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| − | | |
| − | This document is meant to provide guidance on how to utilize CSP under a variety of situations to address a variety of concerns.
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| − | | |
| − | = References =
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| − | | |
| − | Specifications of the CSP standard can be found the following locations:
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| − | * Latest Revision - https://w3c.github.io/webappsec/specs/content-security-policy/
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| − | * Latest Version (CSP2) - http://www.w3.org/TR/CSP2/
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| − | * CSP 1.0 - http://www.w3.org/TR/2012/CR-CSP-20121115/
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| − | | |
| − | = CSP Basics =
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| − | | |
| − | CSP consists of a series of directives. CSP has also evolved over two major revisions. Most browsers support 1.0, and adoption of CSP2 has been incremental.
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| − | | |
| − | == HTTP Headers ==
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| − | | |
| − | The following are headers for CSP.
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| − | | |
| − | * '''Content-Security-Policy''' : W3C Spec standard header. Supported by Firefox 23+, Chrome 25+ and Opera 19+
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| − | * '''Content-Security-Policy-Report-Only''' : W3C Spec standard header. Supported by Firefox 23+, Chrome 25+ and Opera 19+, whereby the policy is non-blocking ("fail open") and a report is sent to the URL designated by the '''report-uri''' directive. This is often used as a precursor to utilizing CSP in blocking mode ("fail closed")
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| − | * '''DO NOT''' use X-Content-Security-Policy or X-WebKit-CSP. Their implementations are obsolete (since Firefox 23, Chrome 25), limited, inconsistent, and incredibly buggy.
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| − | | |
| − | == Directives ==
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| − | | |
| − | The following is a listing of directives, and a brief description.
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| − | | |
| − | === CSP 1.0 Spec ===
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| − | * '''connect-src''' (d) - restricts which URLs the protected resource can load using script interfaces. (e.g. send() method of an XMLHttpRequest object)
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| − | * '''font-src''' (d) - restricts from where the protected resource can load fonts
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| − | * '''img-src''' (d) - restricts from where the protected resource can load images
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| − | * '''media-src''' (d) - restricts from where the protected resource can load video, audio, and associated text tracks
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| − | * '''object-src''' (d) - restricts from where the protected resource can load plugins
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| − | * '''script-src''' (d) - restricts which scripts the protected resource can execute. Additional restrictions against, inline scripts, and eval. Additional directives in CSP2 for hash and nonce support
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| − | * '''style-src''' (d) - restricts which styles the user may applies to the protected resource. Additional restrictions against inline and eval.
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| − | * '''default-src''' - Covers any directive with ''(d)''
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| − | * '''frame-src''' - restricts from where the protected resource can embed frames. Note, deprecated in CSP2
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| − | * '''report-uri''' - specifies a URL to which the user agent sends reports about policy violation
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| − | * '''sandbox''' - specifies an HTML sandbox policy that the user agent applies to the protected resource. Optional in 1.0
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| − | | |
| − | === New in CSP2 ===
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| − | * '''form-action''' - retricts which URLs can be used as the action of HTML form elements
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| − | * '''frame-ancestors''' - indicates whether the user agent should allow embedding the resource using a frame, iframe, object, embed or applet element, or equivalent functionality in non-HTML resources
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| − | * '''plugin-types''' - restricts the set of plugins that can be invoked by the protected resource by limiting the types of resources that can be embedded
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| − | * '''base-uri''' - restricts the URLs that can be used to specify the document base URL
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| − | * '''child-src''' (d) - governs the creation of nested browsing contexts as well as Worker execution contexts
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| − | | |
| − | = CSP Sample Policies =
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| − | | |
| − | == Basic CSP Policy ==
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| − | | |
| − | This policy will only allow resources from the originating domain for all the default level directives, and will not allow inline scripts/styles to execute. If your application and function with these restrictions, it drastically reduces your attack surface having this policy in place, and will work with most modern browsers.
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| − | | |
| − | The most basic policy assumes:
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| − | * all resources are hosted by the same domain of the document
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| − | * there are no inlines or evals for scripts and style resources
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| − | | |
| − | Content-Security-Policy: default-src 'self'
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| − | | |
| − | To tighten further, one can do the following:
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| − | | |
| − | Content-Security-Policy: default-src 'none'; script-src 'self'; connect-src 'self'; img-src 'self'; style-src 'self';
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| − | | |
| − | This policy allows images, scripts, AJAX, and CSS from the same origin, and does not allow any other resources to load (eg. object, frame, media, etc). (see http://content-security-policy.com/)
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| − | | |
| − | == Mixed Content Policy ==
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| − | | |
| − | In order to prevent mixed content (resources being loaded over http, from a document loaded over https), one can use the value "https:" as a directive value.
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| − | | |
| − | For instance:
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| − | | |
| − | Content-Security-Policy: default-src https:; connect-src https:; font-src https: data:; frame-src https:;
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| − | img-src https: data:; media-src https:; object-src https:; script-src 'unsafe-inline' 'unsafe-eval' https:;
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| − | style-src 'unsafe-inline' https:;
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| − | | |
| − | This is what was used at Twitter, Oct 2014. The policy prevents mixed content, allows for scheme "data:" in font-src and img-src, allows for unsafe-inline and unsafe-eval for script-src, and unsafe-inline for style-src. (see: https://twittercommunity.com/t/blocking-mixed-content-with-content-security-policy/26375)
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| − | | |
| − | Mixed Content has two categories: Active and Passive. Passive content consists of "resources which cannot directly interact with or modify other resources on a page: images, fonts, audio, and video for example", whereas active content is "content which can in some way directly manipulate the resource with which a user is interacting." (http://www.w3.org/TR/2014/WD-mixed-content-20140722)
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| − | | |
| − | Content-Security-Policy: img-src https: data:; font-src https: data:; media-src https:;
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| − | | |
| − | This is an example to block only passive mixed content.
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| − | | |
| − | Content-Security-Policy: script-src https:; style-src https:; object-src https:; connect-src https:; frame-src https:;
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| − | | |
| − | This is an example to block only active mixed content.
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| − | | |
| − | = CSP Cheat Sheet - Guide for main technologies =
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| − | | |
| − | This section summarizes the implementation and/or support for CSP in different technologies (either acting as Client or Server).
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| − | See below the details.
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| − | '''Google Chrome'''
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| − | Google Chrome based web applications and theme uses a manifest file named manifest.json.
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| − | There is a section in the manifest file where the developer can declare the CSP directives.
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| − | For further details, please refer to Content Security Police for Google Chrome.
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| − | | |
| − | {
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| − | ''// Required''
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| − | "manifest_version": 2,
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| − | "name": "My Extension",
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| − | "version": "versionString",
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| − | | |
| − | ''// Recommended''
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| − | "default_locale": "en",
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| − | "description": "A plain text description",
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| − | "icons": {...},
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| − | | |
| − | ''// Pick one (or none)''
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| − | "browser_action": {...},
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| − | "page_action": {...},
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| − | | |
| − | ''// Optional''
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| − | "author": ...,
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| − | "automation": ...,
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| − | "background": {
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| − | // Recommended
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| − | "persistent": false
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| − | },
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| − | "background_page": ...,
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| − | "chrome_settings_overrides": {...},
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| − | "chrome_ui_overrides": {
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| − | "bookmarks_ui": {
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| − | "remove_bookmark_shortcut": true,
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| − | "remove_button": true
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| − | }
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| − | },
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| − | "chrome_url_overrides": {...},
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| − | "commands": ...,
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| − | "content_pack": ...,
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| − | "content_scripts": [{...}],
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| − | "content_security_policy": "policyString",
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| − | "converted_from_user_script": ...,
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| − | "current_locale": ...,
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| − | "devtools_page": ...,
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| − | "externally_connectable": {
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| − | "matches": ["*://*.example.com/*"]
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| − | },
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| − | "file_browser_handlers": [...],
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| − | "homepage_url": "http://path/to/homepage",
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| − | "import": ...,
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| − | "incognito": "spanning or split",
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| − | "input_components": ...,
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| − | "key": "publicKey",
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| − | "minimum_chrome_version": "versionString",
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| − | "nacl_modules": [...],
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| − | "oauth2": ...,
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| − | "offline_enabled": true,
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| − | "omnibox": {
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| − | "keyword": "aString"
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| − | },
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| − | "optional_permissions": ...,
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| − | "options_page": "aFile.html",
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| − | "options_ui": ...,
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| − | "page_actions": ...,
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| − | "permissions": [...],
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| − | "platforms": ...,
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| − | "plugins": [...],
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| − | "requirements": {...},
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| − | "sandbox": [...],
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| − | "script_badge": ...,
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| − | "short_name": "Short Name",
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| − | "signature": ...,
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| − | "spellcheck": ...,
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| − | "storage": {
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| − | "managed_schema": "schema.json"
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| − | },
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| − | "system_indicator": ...,
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| − | "tts_engine": ...,
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| − | "update_url": "http://path/to/updateInfo.xml",
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| − | "web_accessible_resources": [...]}
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| − | '''Apache'''
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| − | It is required to add lines to the httpd.conf configuration file, or inside .htaccess files or virtual host sections.
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| − | Also, it is required to enable mod_headers, and after inserting the lines according to your specific needs, restart Apache.
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| − | The headers below are good examples to add in the files (change/modify it properly):
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| − | Header unset Content-Security-Policy
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| − | Header add Content-Security-Policy "default-src 'self'"
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| − | Header unset X-Content-Security-Policy
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| − | Header add X-Content-Security-Policy "default-src 'self'"
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| − | Header unset X-WebKit-CSP Header add X-WebKit-CSP "default-src 'self'"
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| − | | |
| − | | |
| − | '''WordPress'''
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| − | | |
| − | Most of the configuration can be done in Apache, however, Wordpress has a plugin that allows developers/administrator to set up their own custom policies. The plugin however is not update for 2 years. Use it carefully.
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| − | A workaround can be the creation or modification of the file htaccess under wp-admin directory.
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| − | | |
| − | An example:
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| − | | |
| − | <IfModule mod_headers.c>
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| − | Header set Content-Security-Policy "default-src 'self';
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| − | img-src 'self' data: http: https: *.gravatar.com;
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| − | script-src 'self' 'unsafe-inline' 'unsafe-eval';
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| − | style-src 'self' 'unsafe-inline' http: https: fonts.googleapis.com;
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| − | font-src 'self' data: http: https: fonts.googleapis.com themes.googleusercontent.com;"
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| − | </IfModule>
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| − | | |
| − | '''nginx'''
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| − | | |
| − | <nowiki>For nginx, it is required to edit the nginx.conf file.
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| − | | |
| − | | |
| − | # config to don't allow the browser to render the page inside an frame or iframe
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| − | | |
| − | # and avoid clickjacking http://en.wikipedia.org/wiki/Clickjacking
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| − | | |
| − | # if you need to allow [i]frames, you can use SAMEORIGIN or even set an uri with ALLOW-FROM uri # https://developer.mozilla.org/en-US/docs/HTTP/X-Frame-Options
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| − | add_header X-Frame-Options SAMEORIGIN;
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| − | | |
| − | | |
| − | # when serving user-supplied content, include a X-Content-Type-Options: nosniff header along with the Content-Type: header,
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| − | | |
| − | # to disable content-type sniffing on some browsers.
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| − | | |
| − | # https://www.owasp.org/index.php/List_of_useful_HTTP_headers
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| − | | |
| − | # currently suppoorted in IE > 8 http://blogs.msdn.com/b/ie/archive/2008/09/02/ie8-security-part-vi-beta-2-update.aspx
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| − | | |
| − | # http://msdn.microsoft.com/en-us/library/ie/gg622941(v=vs.85).aspx
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| − | | |
| − | # 'soon' on Firefox https://bugzilla.mozilla.org/show_bug.cgi?id=471020
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| − | add_header X-Content-Type-Options nosniff;
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| − | | |
| − | # This header enables the Cross-site scripting (XSS) filter built into most recent web browsers.
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| − | | |
| − | # It's usually enabled by default anyway, so the role of this header is to re-enable the filter for
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| − | | |
| − | # this particular website if it was disabled by the user.
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| − | | |
| − | # https://www.owasp.org/index.php/List_of_useful_HTTP_headers
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| − | add_header X-XSS-Protection "1; mode=block";
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| − | | |
| − | # with Content Security Policy (CSP) enabled(and a browser that supports it(http://caniuse.com/#feat=contentsecuritypolicy),
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| − | | |
| − | # you can tell the browser that it can only download content from the domains you explicitly allow
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| − | | |
| − | # http://www.html5rocks.com/en/tutorials/security/content-security-policy/
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| − | | |
| − | # https://www.owasp.org/index.php/Content_Security_Policy
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| − | | |
| − | # I need to change our application code so we can increase security by disabling 'unsafe-inline' 'unsafe-eval'
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| − | | |
| − | # directives for css and js(if you have inline css or js, you will need to keep it too).
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| − | | |
| − | # more: http://www.html5rocks.com/en/tutorials/security/content-security-policy/#inline-code-considered-harmful
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| − | add_header Content-Security-Policy "default-src 'self'; script-src 'self' 'unsafe-inline' 'unsafe-eval' https://ssl.google-analytics.com https://assets.zendesk.com https://connect.facebook.net; img-src 'self' https://example.com https://example1.com; style-src https://example.com; font-src https://example.com; frame-src https://example.com; object-src 'none'";
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| − |
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| − | server {
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| − | listen 443 ssl default deferred;
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| − | server_name .forgott.com;
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| − |
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| − | ssl_certificate the_path_of_your_certificate.crt;
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| − | ssl_certificate_key the_path_of_your_key.key;</nowiki>
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| − | | |
| − | | |
| − | '''Django'''
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| − | | |
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| − | Django recently introduced a package with a number a collection of models, views and middlewares to aid secure Django based projects.
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| − | The installation of this model can be done through from Python packages repository:
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| − | pip install django-security
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| − | Also, the the latest development version, install from django-security repository on GitHub:
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| − | git clone https://github.com/sdelements/django-security.git
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| − | cd django-security
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| − | sudo python setup.py install
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| − | For each Djangon’s application, the settings.py file must be modified.
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| − | | |
| − | == INSTALLED_APPS = (
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| − | ...
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| − | 'security',
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| − | ...
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| − | )
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| − | ==
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| − | | |
| − | Middleware modules can be added to MIDDLEWARE_CLASSES list in settings file. Particularly, it is our interesting the ContentSecurityPolicyMiddleware. It sends Content Security Policy (CSP) header in HTTP response.:
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| − | | |
| − | | |
| − | == MIDDLEWARE_CLASSES = (
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| − | ...
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| − | 'security.middleware.DoNotTrackMiddleware',
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| − | ==
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| − | | |
| − | = Authors and Primary Editors =
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| − | | |
| − | Neil Mattatall - neil[at]owasp.org<br/>
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| − | Denis Mello - ddtaxe
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| − | | |
| − | = Other Cheatsheets =
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| − | {{Cheatsheet_Navigation}}
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| − | | |
| − | [[Category:Cheatsheets]]
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