Mitigate MaliciousnessMike West

https://mikewest.org/G+: https://mkw.st/+Twitter: @mikewest

<script> doAstoundinglyAwesomeThing();</script>

<script> sneakilyExfiltrateUserData();</script>

XSS is scary.

scheme://host:port

https://www.owasp.org/index.php/XSS_Filter_Evasion_Cheat_Sheet

<style> p { color: {{USER_COLOR}}; }</style><p> Hello {{USER_NAME}}, view your <a href="{{USER_URL}}">Account</a>.</p><script> var id = {{USER_ID}};</script><!-- DEBUG: {{INFO}} -->

[][(![]+[])[+[[+[]]]]+([][[]]+[])[+[[!+[]+!+[]+!+[]+!+[]+!+[]]]]+(![]+[])[+[[!+[]+!+[]]]]+(!![]+[])[+[[+[]]]]+(!![]+[])[+[[!+[]+!+[]+!+[]]]]+(!![]+[])[+[[+!+[]]]]][([][(![]+[])[+[[+[]]]]+([][[]]+[])[+[[!+[]+!+[]+!+[]+!+[]+!+[]]]]+(![]+[])[+[[!+[]+!+[]]]]+(!![]+[])[+[[+[]]]]+(!![]+[])[+[[!+[]+!+[]+!+[]]]]+(!![]+[])[+[[+!+[]]]]]+[])[+[[!+[]+!+[]+!+[]]]]+([][(![]+[])[+[[+[]]]]+([][[]]+[])[+[[!+[]+!+[]+!+[]+!+[]+!+[]]]]+(![]+[])[+[[!+[]+!+[]]]]+(!![]+[])[+[[+[]]]]+(!![]+[])[+[[!+[]+!+[]+!+[]]]]+(!![]+[])[+[[+!+[]]]]]+[])[+[[!+[]+!+[]+!+[]+!+[]+!+[]+!+[]]]]+([][[]]+[])[+[[+!+[]]]]+(![]+[])[+[[!+[]+!+[]+!+[]]]]+(!![]+[])[+[[+[]]]]+(!![]+[])[+[[+!+[]]]]+([][[]]+[])[+[[+[]]]]+([][(![]+[])[+[[+[]]]]+([][[]]+[])[+[[!+[]+!+[]+!+[]+!+[]+!+[]]]]+(![]+[])[+[[!+[]+!+[]]]]+(!![]+[])[+[[+[]]]]+(!![]+[])[+[[!+[]+!+[]+!+[]]]]+(!![]+[])[+[[+!+[]]]]]+[])[+[[!+[]+!+[]+!+[]]]]+(!![]+[])[+[[+[]]]]+([][(![]+[])[+[[+[]]]]+([][[]]+[])[+[[!+[]+!+[]+!+[]+!+[]+!+[]]]]+(![]+[])[+[[!+[]+!+[]]]]+(!![]+[])[+[[+[]]]]+(!![]+[])[+[[!+[]+!+[]+!+[]]]]+(!![]+[])[+[[+!+[]]]]]+[])[+[[!+[]+!+[]+!+[]+!+[]+!+[]+!+[]]]]+(!![]+[])[+[[+!+[]]]]]((![]+[])[+[[+!+[]]]]+(![]+[])[+[[!+[]+!+[]]]]+(!![]+[])[+[[!+[]+!+[]+!+[]]]]+(!![]+[])[+[[+!+[]]]]+(!![]+[])[+[[+[]]]]+([][(![]+[])[+[[+[]]]]+([][[]]+[])[+[[!+[]+!+[]+!+[]+!+[]+!+[]]]]+(![]+[])[+[[!+[]+!+[]]]]+(!![]+[])[+[[+[]]]]+(!![]+[])[+[[!+[]+!+[]+!+[]]]]+(!![]+[])[+[[+!+[]]]]]+[])[+[[+!+[]]]+[[!+[]+!+[]+!+[]+!+[]+!+[]]]]+[+!+[]]+([][(![]+[])[+[[+[]]]]+([][[]]+[])[+[[!+[]+!+[]+!+[]+!+[]+!+[]]]]+(![]+[])[+[[!+[]+!+[]]]]+(!![]+[])[+[[+[]]]]+(!![]+[])[+[[!+[]+!+[]+!+[]]]]+(!![]+[])[+[[+!+[]]]]]+[])[+[[+!+[]]]+[[!+[]+!+[]+!+[]+!+[]+!+[]+!+[]]]])()

[][(![]+[])[+[[+[]]]]+([][[]]+[])[+[[!+[]+!+[]+!+[]+!+[]+!+[]]]]+(![]+[])[+[[!+[]+!+[]]]]+(!![]+[])[+[[+[]]]]+(!![]+[])[+[[!+[]+!+[]+!+[]]]]+(!![]+[])[+[[+!+[]]]]][([][(![]+[])[+[[+[]]]]+([][[]]+[])[+[[!+[]+!+[]+!+[]+!+[]+!+[]]]]+(![]+[])[+[[!+[]+!+[]]]]+(!![]+[])[+[[+[]]]]+(!![]+[])[+[[!+[]+!+[]+!+[]]]]+(!![]+[])[+[[+!+[]]]]]+[])[+[[!+[]+!+[]+!+[]]]]+([][(![]+[])[+[[+[]]]]+([][[]]+[])[+[[!+[]+!+[]+!+[]+!+[]+!+[]]]]+(![]+[])[+[[!+[]+!+[]]]]+(!![]+[])[+[[+[]]]]+(!![]+[])[+[[!+[]+!+[]+!+[]]]]+(!![]+[])[+[[+!+[]]]]]+[])[+[[!+[]+!+[]+!+[]+!+[]+!+[]+!+[]]]]+([][[]]+[])[+[[+!+[]]]]+(![]+[])[+[[!+[]+!+[]+!+[]]]]+(!![]+[])[+[[+[]]]]+(!![]+[])[+[[+!+[]]]]+([][[]]+[])[+[[+[]]]]+([][(![]+[])[+[[+[]]]]+([][[]]+[])[+[[!+[]+!+[]+!+[]+!+[]+!+[]]]]+(![]+[])[+[[!+[]+!+[]]]]+(!![]+[])[+[[+[]]]]+(!![]+[])[+[[!+[]+!+[]+!+[]]]]+(!![]+[])[+[[+!+[]]]]]+[])[+[[!+[]+!+[]+!+[]]]]+(!![]+[])[+[[+[]]]]+([][(![]+[])[+[[+[]]]]+([][[]]+[])[+[[!+[]+!+[]+!+[]+!+[]+!+[]]]]+(![]+[])[+[[!+[]+!+[]]]]+(!![]+[])[+[[+[]]]]+(!![]+[])[+[[!+[]+!+[]+!+[]]]]+(!![]+[])[+[[+!+[]]]]]+[])[+[[!+[]+!+[]+!+[]+!+[]+!+[]+!+[]]]]+(!![]+[])[+[[+!+[]]]]]((![]+[])[+[[+!+[]]]]+(![]+[])[+[[!+[]+!+[]]]]+(!![]+[])[+[[!+[]+!+[]+!+[]]]]+(!![]+[])[+[[+!+[]]]]+(!![]+[])[+[[+[]]]]+([][(![]+[])[+[[+[]]]]+([][[]]+[])[+[[!+[]+!+[]+!+[]+!+[]+!+[]]]]+(![]+[])[+[[!+[]+!+[]]]]+(!![]+[])[+[[+[]]]]+(!![]+[])[+[[!+[]+!+[]+!+[]]]]+(!![]+[])[+[[+!+[]]]]]+[])[+[[+!+[]]]+[[!+[]+!+[]+!+[]+!+[]+!+[]]]]+[+!+[]]+([][(![]+[])[+[[+[]]]]+([][[]]+[])[+[[!+[]+!+[]+!+[]+!+[]+!+[]]]]+(![]+[])[+[[!+[]+!+[]]]]+(!![]+[])[+[[+[]]]]+(!![]+[])[+[[!+[]+!+[]+!+[]]]]+(!![]+[])[+[[+!+[]]]]]+[])[+[[+!+[]]]+[[!+[]+!+[]+!+[]+!+[]+!+[]+!+[]]]])()

alert(1)

“I discount theprobability

of perfection.” -Alex Russell

Not “if”, but “when”.

Before all else, send data securely

$ curl -I http://mkw.st/HTTP/1.1 301 Moved PermanentlyServer: nginx/1.3.7Date: Sun, 11 Nov 2012 19:36:15 GMTContent-Type: text/htmlContent-Length: 184Connection: keep-aliveKeep-Alive: timeout=20Location: https://mkw.st/

Set-Cookie: ...; secure; HttpOnly

Strict-Transport-Security: max-age=2592000; includeSubDomains

Public-Key-Pins: max-age=2592000; pin-sha1="4n972H…60yw4uqe/baXc="; pin-sha1="IvGeLsbqzP…j2xVTdXgc="

http://tools.ietf.org/html/draft-ietf-websec-key-pinning

http://www.html5rocks.com/en/tutorials/security/transport-layer-security/

Limit the browser’s capabilities

“Every program and every privileged user of the system should operate using the least amount of privilege necessary to complete the job.”

Jerome H. Saltzer, "Protection and the control of information sharing in multics"

http://traumwerk.stanford.edu/philolog/2009/10/homers_odyssey_in_art_sirens_f.html

http://w3.org/TR/CSP11

Content-Security-Policy: default-src 'none'; style-src https://mikewestdotorg.hasacdn.net; frame-src https://www.youtube.com http://www.slideshare.net; script-src https://mikewestdotorg.hasacdn.net https://ssl.google-analytics.com; img-src 'self' https://mikewestdotorg.hasacdn.net https://ssl.google-analytics.com data:; font-src https://mikewestdotorg.hasacdn.net

Content-Security-Policy: default-src ...; script-src ...; object-src ...; style-src ...; img-src ...; media-src ...; frame-src ...; font-src ...; connect-src ...; sandbox ...; report-uri https://example.com/reporter.cgi

<script> function handleClick() { ... }</script><button onclick="handleClick()">Click me!</button><a href="javascript:handleClick()">Click me!</a>

<!-- index.html --><script src="clickHandler.js"></script><button class="clickable">Click me!</button><a href="#" class="clickable">Click me!</a>

<!-- clickHandler.js -->function handleClick() { ...}

document.addEventListener('DOMContentLoader', function() { for (var e in document.querySelectorAll('.clickable')) e.addEventListener('click', clickHandler);});

Content-Security-Policy-Report-Only: default-src https:; report-uri https://example.com/csp-violations { "csp-report": { "document-uri": "http://example.org/page.html", "referrer": "http://evil.example.com/haxor.html", "blocked-uri": "http://evil.example.com/image.png", "violated-directive": "default-src 'self'", "original-policy": "...", "line-number": "10" }}

http://www.html5rocks.com/en/tutorials/security/content-security-policy/

Remember two things:HTTPS: http://goo.gl/Pw6wU

CSP: http://goo.gl/QcuaK

Questions?mkwst@google.com

mkw.st/+ @mikewest

Even fewer privileges!

<iframe src="page.html" sandbox></iframe><!-- * Unique origin * No plugins. * No script. * No form submissions. * No top-level navigation. * No popups. * No autoplay. * No pointer lock. * No seamless iframes.-->

<iframe src="page.html" sandbox="allow-forms allow-pointer-lock allow-popups allow-same-origin allow-scripts allow-top-navigation"></iframe><!-- * No plugins. * No seamless iframes.-->

<!-- User-generated content? (in The Near Future™) --><iframe seamless srcdoc="<p>This is a comment!</p>" sandbox></iframe>

http://www.html5rocks.com/en/tutorials/security/sandboxed-iframes/