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Security for javascript
- 2. Security Thenumber 1 biggest problem with thewholeWorld WideWeb.
- 3. Thebrowser isnot asafe programming environment. It isinherently insecure.
- 4. What can an attacker do if he getssomescript into your page?
- 5. An attacker can request additional scriptsfrom any server in theworld. Onceit getsafoothold, it can obtain all of thescriptsit needs.
- 6. An attacker can makerequestsof your server. Your server cannot detect that the request did not originatewith your application.
- 7. An attacker can read the document. Theattacker can seeeverything the user sees.
- 8. An attacker hascontrol over the display and can request information from theuser. Theuser cannot detect that the request did not originatewith your application.
- 9. An attacker can send information to serversanywherein theworld.
- 10. Thebrowser doesnot prevent any of these. That'swhy they happen.
- 11. Theconsequencesof asuccessful attack arehorrible. Harm to customers. Lossof trust. Legal liabilities. Possiblecriminal penalties.
- 12. Thisisnot aWeb 2.0 problem. All of theseproblemscamewith Netscape2 in 1995.
- 13. TheTurducken Problem • Many Languages: HTTP, HTML, URL, CSS, JavaScript, XML, JSON, plaintext, SQL... • Each languagehasdifferent quoting and commenting conventions. • Thelanguagescan benested insideeach other.
- 14. A text that isbenign in onecontext might bedangerousin another. Sloppy encoding allowsinjection of evil scripts
- 15. A SimpleAttack http://yourdomain.com/ <script>alert("XSS");</script> <html><body> <p>File not found: <script>alert("XSS");</script> </p></body></html> • Thescript runswith theauthority of your site.
- 16. A SimpleAttack http://yourdomain.com/ <script>alert("XSS");</script> <html><body> <p>File not found: <script>alert("XSS");</script> </p></body></html> • Proper escapement providessomesafety.
- 17. Another Example • Bad text " + alert("XSS") + " • Bad encoding {"json": "" + alert("XSS") + ""} • Good encoding {"json": "" + alert("XSS") + ""}
- 18. Coding hygieneiscritical for avoiding turducken attacks. Usegood encoders. json.org/json2.js Do not usesimpleconcatenation. Never trust thebrowser. Validateall input.
- 19. CrossSiteDataAccess It isextremely useful to obtain datafrom other sitesand mash it up.
- 21. Script Tag Hack • Scripts(strangely) areexempt from Same Origin Policy. • A dynamic script tag can makeaGET request from aserver. receiver(jsontext); • Extremely dangerous. It isimpossibleto assurethat theserver did not send an evil script.
- 22. JavaScript'sGlobal Object Theroot causeof XSSattacks. All scriptsrun with thesame authority.
- 23. JavaScript isan insecure language. TheES4 Proposal iseven worse. It should beabandoned.
- 24. Document Object Model All nodesarelinked to all other nodes and to thenetwork.
- 25. Cookies Ambient authority leadsto confusion and impersonation (XSRF)
- 26. Remedy: Crumbs An explicit secret should besent with theambient cookie. FrustratesXSRF attacks. Not effectiveagainst XSSattacks.
- 27. Excellent CodeQuality If codeisclean and readable, it isless likely to contain insecurities.
- 28. JSLint • JSLint definesaprofessional subset of JavaScript. • It imposesaprogramming disciplinethat makesmemuch moreconfident in adynamic, loosely-typed environment. http://www.JSLint.com/
- 29. Warning! JSLint will hurt your feelings.
- 30. If theweb asbeen totally screwed up from thebeginning, why should we worry about it now? 1. Escalating legal penalties 2. Mashups 3. Competition
- 31. Mashups Themost interesting innovation in softwaredevelopment in 20 years.
- 32. Mashupsareinsecure. Mashupsmust not haveaccessto any confidential information.
- 33. If thereisscript from two or more sources, theapplication isnot secure. Period.
- 36. That wouldn't betheend of the world. It would just betheend of theWWW.
- 37. A ThreeProng Strategy to Fix theWeb 1. SafeJavaScript subsets. 2. Small browser improvements. 3. Massivebrowser improvements. Thiscould takeawhile, so weshould proceed on all threeimmediately.
- 38. 1. SafeJavaScript Subsets. Theeasiest way to improve JavaScript isto makeit smaller.
- 39. ADsafe • A JSLint option. • It definesasafeHTML/JavaScript subset. • Removesfrom JavaScript all featuresthat are unsafeor suspect. • Allowsforeign adsand widgetsto safely interact.
- 40. ADsafe • No global variablesor functionsmay be defined. • No global variablesor functionscan be accessed except theADSAFE object. • The[] subscript operator may not beused. • Thesewordscannot beused: apply call callee caller constructor eval new prototype this watch • Wordsstarting with _ cannot beused.
- 41. Dangers • Theremay still beundiscovered weaknessesin ECMAScript and itsmany implementations. • Browser implementationsarechanging, introducing new weaknesses. • TheDOM wrappersmust beflawless. • Wearestill subject to XSSattacks.
- 42. 2. Add SimpleFeatures to theBrowsers. Even simpleimprovementscan takea long timeto distribute.
- 44. Vats Communicating computational containment vessels
- 45. HTML ProvidesNo Modules • It wasconceived to beadocument format. • Weareusing it asan application format. • Applicationsrequiresmodules. • Modulesprotect their contents. • Modulescommunicateby exposing clean interfaces.
- 46. Vats • Adapting Google'sGearsor Adobe'sAIR to providecommunicating containment. • Providescooperation under mutual suspicion. • Heavyweight. • Distribution isdifficult. • Still subject to XSSattacks.
- 47. 3. Weneed to replaceJavaScript and theDOM. Aslong asweareusing insecure languages, wewill besubject to XSS attacks.
- 48. Start with theADsafesubset, and then carefully add featuresto enhanceexpressiveness.
- 49. A isan Object. Object A hasstate and behavior.
- 50. Object A hasa referenceto Object B. An object can have referencesto other objects. has-a
- 51. ...becauseit hasa referenceto Object B. Object A can communicatewith Object B...
- 52. Object B provides an interfacethat constrainsaccess to itsown state and references. Every object isamicro vat.
- 53. Object A doesnot haveareferenceto Object C, so Object A cannot communicatewith Object C. In an Object Capability System, an object can only communicatewith objects that it hasreferencesto.
- 54. An Object Capability System is produced by constraining theways that referencesareobtained. A referencecannot beobtained simply by knowing thenameof a global variableor apublic class.
- 55. Thereareexactly threewaysto obtain areference. 1. By Creation. 2. By Construction. 3. By Introduction.
- 56. 1. By Creation If afunction createsan object, it gets areferenceto that object.
- 57. 2. By Construction An object may beendowed by itsconstructor with references. Thiscan includereferencesin theconstructor's context and inherited references.
- 58. 3. By Introduction A hasareferencesto B and C. B hasno references, so it cannot communicatewith A or C. C hasno references, so it cannot communicatewith A or B.
- 59. 3. By Introduction A callsB, passing areferenceto C.
- 60. 3. By Introduction B isnow ableto communicatewith C. It hasthecapability.
- 61. Weaknessesto avoid include 1. Arrogation. 2. Corruption. 3. Confusion. 4. Collusion.
- 62. Thereisno security in obscurity Tricksand puzzlesarenot effective. Speed bumpsarenot effective.
- 64. Thesecurity problemsarenot new. Theproblemsaregetting harder to ignore.
- 65. Ultimately • Weneed to replaceJavaScript with asecure language. • Thecurrent ES4 proposal isnot that language. • Weneed to replaceHTML and theDOM with asecureapplication delivery system. • Thecurrent HTML5 proposal isnot that either.
- 66. Ultimately • Secureprogramming languageto replace JavaScript. • A modular application framework to replace theDOM and CSS. • A common text representation and protocol to replaceHTTPand theAjax stack. • Otherwise, theweb may fall to newer proprietary systems.
- 67. Meanwhile • Never trust thebrowser. • Formally validateeverything you receivefrom the browser. • Properly encodeeverything you send to thebrowser or database. • Do not circumvent what littlesecurity thebrowser offers. • Never put dataon thewireunlessyou want it to be delivered. • Don't takeineffectivemeasures.
- 68. BeRigorous • SloppinessaidstheEnemy. • Neatnesscounts. • Usegood encoders. • Avoid concatenation. • Beparanoid.
- 69. Turducken