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| + | #REDIRECT [[HTTP_Strict_Transport_Security_Cheat_Sheet]] |
| − | == Description ==
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| − | HTTP Strict Transport Security (HSTS) is an opt-in security enhancement that is specified by a web application through the use of a special response header. Once a supported browser receives this header that browser will prevent any communications from being sent over HTTP to the specified domain and will instead send all communications over HTTPS. It also prevents HTTPS click through prompts on browsers.
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| − | The specification has been released and published end of 2012 as RFC 6797 (HTTP Strict Transport Security (HSTS)) by the IETF. (Reference see in the links at the bottom.)
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| − | == Examples ==
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| − | | |
| − | Simple example, using a long (1 year) max-age:
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| − | Strict-Transport-Security: max-age=31536000
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| − | If all present and future subdomains will be HTTPS:
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| − | Strict-Transport-Security: max-age=31536000; includeSubDomains
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| − | '''Recommended:''' If the site owner would like their domain to be included in the [https://hstspreload.appspot.com/ HSTS preload list] maintained by Chrome (and used by Firefox and Safari), then use:
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| − | Strict-Transport-Security: max-age=31536000; includeSubDomains; preload
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| − | | |
| − | The `preload` flag indicates the site owner's consent to have their domain preloaded. The site owner still needs to then go and submit the domain to the list.
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| − | == Excessively Strict STS ==
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| − | Use caution when setting excessively strict STS policies. Including subdomains should only be used in environments where all sites within your organization for the given domain name require ssl. Max-age limits should be carefully considered as infrequent visitors may find your site inaccessible if you relax your policy.
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| − | Before enabling includeSubDomains, also consider the impact of any existing DNS CNAME records for CDNs, email services, or other 3rd party services. Since includeSubDomains will force such CNAME subdomains to https:// it's likely the browser will throw a domain-mismatch error, which is hard to reverse because of the browser caching nature of HSTS.
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| − | == Browser Support ==
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| − | {| width="400" cellspacing="1" cellpadding="1" border="1"
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| − | |-
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| − | | '''Browser'''<br>
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| − | | '''Support Introduced'''<br>
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| − | | Internet Explorer <br>
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| − | | Internet Explorer 11 on Windows 8.1 and Windows 7[http://blogs.windows.com/msedgedev/2015/06/09/http-strict-transport-security-comes-to-internet-explorer-11-on-windows-8-1-and-windows-7/]<br>
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| − | |-
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| − | | Firefox<br>
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| − | | 4<br>
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| − | |-
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| − | | Opera<br>
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| − | | 12<br>
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| − | |-
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| − | | Safari<br>
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| − | | Mavericks (Mac OS X 10.9)<br>
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| − | |-
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| − | | Chrome<br>
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| − | | 4.0.211.0<br>
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| − | |}
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| − | <br>
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| − | A detailed overview of supporting browsers can be found at [http://caniuse.com/#feat=stricttransportsecurity caniuse.com].
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| − | == Server Side ==
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| − | The web server side needs to inject the HSTS header.
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| − | For HTTP sites on the same domain it is [http://tools.ietf.org/html/draft-ietf-websec-strict-transport-sec#section-6.1 not recommended] to add a HSTS header but to do a permanent redirect (301 status code) to the HTTPS site.
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| − | An Apache HTTPd example that will permanently redirect a URL to the identical URL with a HTTPS scheme, is as follows:
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| − | <VirtualHost *:80>
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| − | ServerAlias *
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| − | RewriteEngine On
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| − | RewriteRule ^(.*)$ https://%{HTTP_HOST}$1 [redirect=301]
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| − | </VirtualHost>
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| − | On the HTTPS site configuration the following is needed to add the header as [http://tools.ietf.org/html/draft-ietf-websec-strict-transport-sec#section-6.1 recommended by the standard]:
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| − | Header always set Strict-Transport-Security "max-age=31536000; includeSubDomains"
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| − | The following links show how to set response headers in other web servers:
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| − | * [http://wiki.nginx.org/HttpHeadersModule NGINX]
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| − | * [http://redmine.lighttpd.net/wiki/lighttpd/Docs:ModSetEnv#Options Lighttpd]
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| − | * [http://httpd.apache.org/docs/2.2/mod/mod_headers.html HTTPd]
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| − | ==== IIS ====
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| − | Whilst [http://technet.microsoft.com/en-us/library/cc753133(WS.10).aspx custom headers] can be configured in IIS without any extensions, it is not possible to restrict these headers to secure transport channels [http://tools.ietf.org/html/rfc6797#section-7.2 as per the HSTS specification]. This leaves the following options.
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| − | | |
| − | ===== Custom Module =====
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| − | HSTS has been implemented, per the specification, as an [http://hstsiis.codeplex.com/ open source IIS module].
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| − | | |
| − | ===== URL Rewrite =====
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| − | Install [http://www.iis.net/downloads/microsoft/url-rewrite Microsoft URL Rewrite] and use following rewrite rules.
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| − | | |
| − | <configuration>
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| − | <system.webServer>
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| − | <rewrite>
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| − | <rules>
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| − | <rule name="HTTPS_301_Redirect" stopProcessing="true">
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| − | <match url="(.*)" />
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| − | <conditions>
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| − | <add input="{HTTPS}" pattern="^OFF$" />
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| − | </conditions>
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| − | <action type="Redirect" url="https://{HTTP_HOST}{REQUEST_URI}" appendQueryString="false" redirectType="Permanent" />
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| − | </rule>
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| − | </rules>
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| − | <outboundRules>
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| − | <rule name="Add_HSTS_Header" preCondition="USING_HTTPS" patternSyntax="Wildcard">
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| − | <match serverVariable="RESPONSE_Strict-Transport-Security" pattern="*" />
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| − | <action type="Rewrite" value="max-age=31536000" />
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| − | </rule>
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| − | <preConditions>
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| − | <preCondition name="USING_HTTPS">
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| − | <add input="{HTTPS}" pattern="^ON$" />
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| − | </preCondition>
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| − | </preConditions>
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| − | </outboundRules>
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| − | </rewrite>
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| − | </system.webServer>
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| − | </configuration>
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| − | == Threats ==
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| − | HSTS addresses the following threats:
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| − | * User bookmarks or manually types http://example.com and is subject to a man-in-the-middle attacker
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| − | ** HSTS automatically redirects HTTP requests to HTTPS for the target domain
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| − | * Web application that is intended to be purely HTTPS inadvertently contains HTTP links or serves content over HTTP
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| − | ** HSTS automatically redirects HTTP requests to HTTPS for the target domain
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| − | * A man-in-the-middle attacker attempts to intercept traffic from a victim user using an invalid certificate and hopes the user will accept the bad certificate
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| − | ** HSTS does not allow a user to override the invalid certificate message
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| − | == Links ==
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| − | * [http://www.youtube.com/watch?v=zEV3HOuM_Vw&feature=youtube_gdata AppSecTutorial Series - Episode 4]
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| − | * [http://dev.chromium.org/sts Chromium Projects/HSTS]
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| − | * [http://tools.ietf.org/html/rfc6797 HSTS Spec]
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| − | * [http://en.wikipedia.org/wiki/HTTP_Strict_Transport_Security Wikipedia]
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| − | * [https://developer.mozilla.org/en/Security/HTTP_Strict_Transport_Security Mozilla Developer Network]
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| − | * [https://www.owasp.org/index.php/Transport_Layer_Protection_Cheat_Sheet OWASP TLS Protection Cheat Sheet]
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| − | * [https://developer.mozilla.org/en/Security/HTTP_Strict_Transport_Security Firefox STS Support]
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| − | * [http://lists.w3.org/Archives/Public/public-webapps/2009JulSep/1148.html Google Chrome STS Support]
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| − | * [http://www.thoughtcrime.org/software/sslstrip/ Moxie Marlinspike's Black Hat 2009 talk on sslstrip, that demonstrates why you need HSTS]
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| − | [[Category:Control|Control]] | |
