libinjection: from SQLi to XSS  by Nick Galbreath


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libinjection was introduced at Black Hat USA 2012 to quickly and accurately detect SQLi attacks from user inputs. Two years later the algorithm has been used by a number of open-source and proprietary WAFs and honeypots. This talk will introduce a new algorithm for detecting XSS. Like the SQLi libinjection algorithm, this does not use regular expressions, is very fast, and has a low false positive rate. Also like the original libinjection algorithm, this is available on GitHub with free license.

Nick Galbreath

Nick Galbreath is Vice President of Engineering at IPONWEB, a world leader in the development of online advertising exchanges. Prior to IPONWEB, his role was Director of Engineering at Etsy, overseeing groups handling security, fraud, security, authentication and other enterprise features. Prior to Etsy, Nick has held leadership positions in number of social and e-commerce companies, including Right Media, UPromise, Friendster, and Open Market. He is the author of ""Cryptography for Internet and Database Applications"" (Wiley). Previous speaking engagements have been at Black Hat, Def Con, DevOpsDays and other OWASP events. He holds a master's degree in mathematics from Boston University and currently resides in Tokyo, Japan.

In 2013
- LASCON, Keynote Speaker Austin, Texas USA
- DevOpsDays Tokyo, Japan
- Security Development Conference (Microsoft)  San Francisco, CA, USA
- DevOpsDays Austin, Texas, USA
- Positive Hack Days, Moscow Russia
- RSA USA, San Francisco, CA, speaker and panelist

In 2012
- DefCon
- BlackHat USA
- Others

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libinjection: from SQLi to XSS  by Nick Galbreath

  1. 1. libinjectionFrom SQLi to XSS Nick Galbreath @ngalbreath! Signal Sciences Corp! Code Blue ∙ Tokyo ∙ 2014-02-17
  2. 2. Nick Galbreath
 @ngalbreath • Founder/CTO of Signal Sciences Corp • Before: IponWeb (Moscow, Tokyo) • Before: Etsy (New York City)
  3. 3. What is libinjection? • A small C-library to detect SQLi attacks in user- input • With API in python, lua and php • Introduced at Black Hat USA 2012 • Open source with BSD license •
  4. 4. Why libinjection? • Existing detection is mostly done with regular expressions • No unit tests • No performance (speed) tests • No coverage tests • No accuracy or precision tests • No false positive tests • “what are they actually doing?”
  5. 5. libinjection SQLi Today • Version 3.9.1 • 8000 unique SQLi fingerprints • 400+ unit tests • 85,000+ SQLi samples
  6. 6. In Use At • mod_security WAF - • ironbee WAF - • glastopf honeypot - • proprietary WAFs • internally at many companies • partial pure-java port
  7. 7. XSS
  8. 8. Similar to SQLi • No standard detection library • Few if any have tests • Regular expression based detection • Can we do better?
  9. 9. Two Types of XSS • HTML injection attacks • Javascript injection attacks
  10. 10. XSS Javascript Injection • Includes DOM-style attacks • Attacks existing javascript code. • Detection can truly be done on client • A very hard problem
  11. 11. HTML Injection • HTML injection are attacks against the HTML tokenization algorithm 
 (text “<b>foo</b>” to tags <b>, foo, </b>) • The goal is to change the context to ‘javascript’ and execute arbitrary code. • This seems detectable.
  12. 12. HTML Injection Samples <b>XSS</b> (raw HTML) <foo XSS> (tag attribute from user input) <foo name=XSS> (tag value from user input) <foo name='XSS'> (quoted value) <foo name="XSS"> (quoted value) <foo name=`XSS`> (IE only!)
  13. 13. Browser HTML Tokenization • Previously every browser parsed or tokenised HTML differently. • This lead to a number of different attacks using broken html tags, special characters or encodings. • Now, most browsers now use the same algorithm specified by HTML5.
  14. 14. > 65% are HTML5
  15. 15. Every Tokenization Step
  16. 16. Is Clearly Defined
  17. 17. The remainder are IE • And IE only has a few versions • And has some well-known exceptions to the HTML5 parsing rules.
  18. 18. IE6 and IE7 • IE7 has only 2% of market share • IE6 will, in time, go away. • Both are likely running on 10 year old machine.
  19. 19. IE8 • Somewhere between 10-20% marketshare • The most modern MS browser on Windows XP • Marketshare can only go down.
  20. 20. Opera • 1.33% Global Market Share • But maybe 40% of that is ‘Opera Mini’ for phone or embedded systems • Opera has a lot of oddities in HTML functionality and parsing • Ignoring
  21. 21. libinjection XSS
  22. 22. HTML injection attacks
 in HTML5 clients. • No: XML / XSLT injection • No: Any injection for IE6, IE7, Opera, FF and Chrome older than a year. • No: DOM style attacks (need a client solution)
  23. 23. libinjection html5 • Full HTML5 Tokenizer. • Does not build a tree or DOMs • Just emits tokenizer events. • Zero copying of data
  24. 24. Tokenization Sample TAG_NAME_OPEN img ATTR_NAME src ATTR_VALUE junk ATTR_NAME onerror ATTR_VALUE alert(1); TAG_NAME_CLOSE > <img src=“junk” onerror=alert(1);>
  25. 25. Check in each Context Each input is parsed in at least 6 different HTML contexts, because thats how XSS works! <b>XSS</b> (raw HTML) <foo XSS> (tag attribute from user input) <foo name=XSS> (tag value from user input) <foo name='XSS'> (quoted value) <foo name="XSS"> (quoted value) <foo name=`XSS`> (IE only!)
  26. 26. Ban Problematic Tokens • Problematic tags, attributes, and values are cataloged. • Tags: <script>, anything XML or SVG related • Attributes: on*, etc • Values: javascript URLs in various formats • and more…
  27. 27. Training Sources
  28. 28. XSS Cheat sheets • Most are outdated (exploits for Firefox 3! ) • sorry OWASP :-( • Each entry validated to make sure they are valid for HTML5 browsers.
  29. 29. • Fantastic resource • But lists many examples for Firefox 3 and/or obsolete Opera versions • Pruned to focus on HTML5 browsers
  30. 30. @soaj1664ashar • Produces interesting new XSS regularly • If you like XSS you should follow him on Twitter
  31. 31. Attack / Scanners • Integrate one scanner’s test cases • Using Shazzer fuzz databases -
  32. 32. Current Status
  33. 33. Available Now • Available on github • • but… still alpha
  34. 34. $ make test-xss ./reader -t -i -x -m 10 ../data/xss* ../data/xss-html5secorg.txt 149 False test 62_1 <x '="foo"><x foo='><img src=x onerror=alert(1)//'> ../data/xss-html5secorg.txt 151 False test 62_2 <! '="foo"><x foo='><img src=x onerror=alert(2)//'> ../data/xss-html5secorg.txt 153 False test 62_3 <? '="foo"><x foo='><img src=x onerror=alert(3)//'> ../data/xss-html5secorg.txt 352 False test 102 <img src="x` `<script>alert(1)</script>"` `> ../data/xss-soaj1664ashar-pastebin-u6FY1xDA.txt 96 False 92) <--`<img/src=` onerror=alert(1)> --!> ../data/xss-soaj1664ashar.txt21 False <form/action=ja&Tab;vascr&Tab;ipt&colon;confirm(document.cookie)> <button/type=submit> ../data/xss-xenotix.txt 17 False "'`><?img src=xxx:x onerror=javascript:alert(1)> ../data/xss-xenotix.txt 19 False '`"><?script>javascript:alert(1)</script> ../data/xss-xenotix.txt 610 False `"'><img src=xxx:x ?onerror=javascript:alert(1)> ../data/xss-xenotix.txt 613 False `"'><img src=xxx:x ?onerror=javascript:alert(1)> ../data/xss-xenotix.txt 615 False `"'><img src=xxx:x ?onerror=javascript:alert(1)> ! XSS : 1628 SAFE : 11 TOTAL : 1639 ! Threshold is 10, got 11, failing. 1639 Total Samples 1628 Detected as XSS 11 False Negatives
  35. 35. IE Unbalanced Quotes • IE 8+ has strange behaviour with ‘unbalanced quotes’ inside comments and attribute values. • Work in progress
  36. 36. Performance 500,000+ 
 checks per second
  37. 37. TODO 2014-02-17 • It’s alpha — so it’s likely to have some spectacular failures (bypasses) • False-positive QA not completed. • Currently does not handle some IE injections • Does not have a test-bed for experimenting 
 (maybe later this week). • More QA, code-coverage needed • No bindings for scripting languages (soon).
  38. 38.