Devoxx 2013 - Cryptographic operations in the browser

Nick Van den Bleeken

why

• easy and secure authentication
• sign/verify messages & docs
• encrypt docs

existing crypto frameworks (Dojo, CryptoJS, etc.)

• completely implemented in JavaScript
• hard to protect against timing attacks (optimizations in JS engine change)
• Math.random() is not secure
• hard to get correct
• performance issues (e.g. number is 64bit float)

alternatives:

• java plugins
  • disabled in many browsers (recommendation US DHS)
  • not on mobile
• native extensions
  • separate install
  • browser specific (some browsers drop support for extension!)
  • not on mobile

solution: Web Cryptography API

• W3C standard: http://www.w3.org/TR/WebCryptoAPI/ (under construction...)
• JS API for web developers
• still requires TLS to prevent sniffing communication
• still relatively complex (requires correct usage of encryption algorithms)

low level API

• Basic building block: window.crypto.subtle
  • .generateKey(algorithmKeyGen ...)
    • callback when key is generated
  • importKey: add existing keys (e.g. public key of bank)
  • verify() signature
  • decrypt() message
  • sign() message
  • ...
• use and combine it for more complex operation

high level API:

• what framework to choose NaCl, KeyCzar, SJCL or ...
• hard to define
• existing APIs should address this: JQuery, Dojo, Prototype etc.
• -> Not for now...

implemented by

• MS IE11 (old version of spec)
• chromium (flags)
• mozilla (under development)
• missing: Safari...
• polycrypt (old version of spec)
• Netflix: webcrypto key discovery

 future need: smartcard support (but: not a focus for US-based companies...)

OWASP BeNeLux 2012: Sandboxing Javascript - Lieven Desmet

'Standard' webpage composition patterns:

• script tag: full 3rd party integration
• iframe tag: more robust (+ sandboxed keyword)

Solutions for security:

• use a secure subset of Javascript (e.g. ADSafe, Facebook JS, etc.)
• browser sandboxing (e.g. WebJail)
• Serverside Tranformation of scripts (Google Caja, BrowserShield, etc.)

Risk examples of 3rd party integrations: (research)

• stale domain names -> re-register & abuse
• typo squatting: e.g. googlesyndicatio.com (without the 'n') triggered a lot of hits

JSand presentation:

• prototype
• aims
  • complete JS mediation
  • backwards compatibility
  • reasonable performance
• components:
  • policies for 3rd party scripts
  • isolate JS through Google Secure EcmaScript library ("use strict" directive)
  • Proxy wrapper for domain access
  • AST transformations through Uglify lib
  • CORS / UMP headers
  • Serversside JS Proxy
• nice demo, very early preview.