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133 lines
4.8 KiB
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=======================
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nginx: Header Hardening
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=======================
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.. Note::
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Except for some specific configuration directives, this is **NOT**
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specific to the nginx plugin. Please note that you can also debug your
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frontend code this way.
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Background Information
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======================
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HTTP headers can control what a web application is allowed to do and what it is
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not. This can be used to harden the web application against some **client side risks**.
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Testing Web Applications Using A Local Proxy
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============================================
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Configuration of Firefox
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------------------------
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For this tests, you should install and configure FoxyProxy_.
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.. _FoxyProxy: https://addons.mozilla.org/de/firefox/addon/foxyproxy-standard/
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After it is installed, click on the proxy settings and add a new one:
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.. image:: images/zap_foxyproxy.png
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As a proxy, enter localhost (or 127.0.0.1 in case localhost does not work) and
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the port 8080. Save the settings.
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Downloading A Proxy Software For Testing
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----------------------------------------
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Well known Test tools are:
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* OWASP ZAP (https://github.com/zaproxy/zaproxy)
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* Burp (https://portswigger.net/burp)
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* mitmproxy (https://mitmproxy.org/)
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When it is downloaded, you usually have to unpack it into a fitting directory.``
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When it is unpacked, you need to run it. In case of ZAP, doubleclick the
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``zap.sh`` or ``zap.bat`` depending on your operating system.
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Next regenerate and export the certificate under
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:menuselection:`Tools --> Options --> Dynamic SSL certificates` and import it into the Firefox
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key store (:menuselection:`Preferences --> Data Protection & Security --> Show Certificates`) with
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full trust.
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Start Testing
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-------------
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Click on the FoxyProxy icon and select the localhost proxy defined first.
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Next just use the application as usual. If you click the red button,
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can stop the request in ZAP and it allows you to edit it:
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.. image:: images/zap_request.png
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When you are done, just click one of the play buttons to disable halting or wait
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for the next request / response to edit that as well. For example the response
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could look like this one:
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.. image:: images/zap_response.png
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You can see a lot of important information here like the used protocol (HTTP/1.1),
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the status code 200 (which means it was successful) and a lot of headers.
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Some of those headers impact security and ZAP will try to make a recommendation,
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which may not be always correct but it may help you to find some (forgotten)
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issues:
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.. image:: images/zap_warnings.png
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The colors of the flags show how high the risk is rated so the redder it is,
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the more impact it has on security. The left view contains a list of the
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findings, the right view contains a detailed description of them.
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Based on this information, you have to decide your further actions.
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Testing Web Applications Using Developer Tools
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==============================================
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When you right click on the web site, you can inspect the element but the
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opening tools also have a tab for networking.
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.. image:: images/firefox_devtools_network.png
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The network tab works like the main view of the proxy.
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You can see which headers are sent and which ones are received.
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The advantage here is that you get some errors on the console tab (for example
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if the CSP has an error). The disadvantage of the console is, that is is not so
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easy to intercept and modify data.
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Inject Missing Headers Via The nginx Plugin
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===========================================
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Security headers in the nginx plugin can be injected by creating a new security
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header configuration:
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.. Image:: images/nginx_security_headers.png
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If you set a setting here, it will override what the webserver sets.
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You can inject this security setting into a location or HTTP server.
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You can read about the headers in the `Mozilla Wiki <https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers>`_ or in the RFCs.
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.. Warning::
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Not all headers are supported by all browsers.
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In short, the headers are:
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========================= ======================================================================
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Referrer Control what a page sees when you link on it
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XSS Protection Enable or disable the detection for (reflected) XSS
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Don't Sniff Content Type Disable content type detection when the original is incorrect
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Strict Transport Security TLS only and enforce valid certificate
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HPKP Pin the public key, not widely used and dangerous [1]_ if misconfigured
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Content Security Policy Controls resources and JS functions
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========================= ======================================================================
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.. [1] If you switch the certificate without announcing its public key first
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via this header in a rollover time span, you will lock this clients out
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because they expect being targetted by a MITM attack and refuse the connection
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and it is hard to reset this pin in the browser.
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