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Hacking The World With Flash
 

Hacking The World With Flash

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    Hacking The World With Flash Hacking The World With Flash Presentation Transcript

    • Hacking The World With Flash: Analyzing Vulnerabilities in Flash and the Risk of Exploitation
              • OWASP 29/2008
              • Paul Craig
              • Security-Assessment.com
      • Who Am I?
        • Paul Craig, Principal Security Consultant - Security-Assessment.com
        • Author, hacker, active security researcher.
      • My Role
        • Application Penetration Tester
        • “ I break the crack-headed ideas of developers..”
      • Comments, Questions, Feedback?
        • Email: [email_address]
      • “ Wow, Macromedia/Adobe Flash is everywhere on the internet!”
        • YouTube, FaceBook, MySpace, CNN, Ebay, etc
        • I Wonder, do internet users implicitly trust Flash content?
      • The Litmus Test: My Wife, Kim.
        • If I sent you a link to funnygame.exe, would you run it? “Nope.”
        • How about funnygame.swf “I would probably open that”
        • Flash is considered harmless, “It’s a funny game or joke”
      • My Question:
        • What are the incurred risks of running Flash content?
        • How easily can Flash be used as an attack vector?
        • Probability of getting pwned through a malicious SWF??
      Overview
    • Who Why How What of Flash
      • Everything you wanted to know about Flash:
        • Originally developed by Macromedia in early 2000’s.
        • Macromedia was purchased by Adobe in 2005 ($3.4 billion!)
      • Flash logic is developed in ActionScript
        • Originally based on ECMAScript/JavaScript.
      • ActionScript API is segregated into two streams.
        • Web Flash Content:
          • ActionScript executed by a browser plug-in/ActiveX control.
          • Reduced functionality API, no access no host functionality.
        • Standalone Flash:
          • Compiled PE executables with embedded ActionScript player
          • .SWF played from local flash player.
          • Larger more complete API, access to host functionality.
    • Who Why How What of Flash
      • ActionScript was developed from a feature in Flash 4, 7 years ago.
      • Flash 4 ‘Actions’ (Macros) expanded into ActionScript v1 in Flash 5.
        • JavaScript like language with simple functionality.
        • Un-enforced variable type system.
        • Simple API for graphical manipulation.
        • Prototype-oriented programming (No class support).
        • Only 60% of API documented.
      • ActionScript v2, 2003-2006
        • Flash is being used for complex applications!
        • Developers demanded more functionality.
        • Compile-time type checking implemented, strict variable typing.
        • Object-oriented programming support.
        • Flash begins to appear ‘everywhere’
    • Who Why How What of Flash
      • ActionScript v3, 2006-Today
        • Compile-time and runtime type validation
        • Support for packages, namespaces and regular expressions.
        • JIT compilation for new Flash Virtual Machine (AMV2)
        • Binary sockets (Connect to a port, send/retrieve data)
        • 10% of API is still undocumented!
      • ActionScript has matured into a flexible/powerful language.
        • Supported by 850 million internet connected desktops.
        • Cross-platform (Windows, OSX, Linux, HP-UX, PPC)
      • “ I would probably open that”
        • “ I probally shouldn’t, aye”
    • Who Why How What of Flash
      • Flash is a Powerful Attack Vector.
        • 850 million devices which support a language (ActionScript)
        • Language first developed by Macromedia, and now Adobe.
          • Vast history of Adobe/Macromedia security issues.
          • Adobe Acrobat exploit anyone?
      • ActionScript is complex.
        • Grown immensely, very quickly.
        • Quickly implemented features tend to contain bugs, exploits.
        • Do Adobe follow a decent secure coding methodology?
        • Adobe make apps like Photoshop do they take internet security seriously?
      • Flash Plug-in is Critical Browser Infrastructure.
        • One zero day in Flash, 850 million exploitable devices.
    • Exploits in Flash
      • Golden Rules of Security:
        • #1 – Software Developers Always Make Mistakes.
        • #2 – Mistakes Get Exploited.
        • #3 – Developers tend to make the SAME mistake more than once.
        • #4 – See #1
        • A History of Flash Exploits (2001-2008)
          • Look for common trends in Flash exploits over the last 7 years.
          • Predict the future of Flash security, what will 2008 bring?
          • Likelihood of malicious Flash content.
          • Find new vulnerabilities in Flash.
            • Same bug, different section of Flash.
    • Exploits in Flash
      • 2002: First Major Flash Security Advisory’s
        • Standalone Macromedia Flash Player 5.0 allows remote attackers to save arbitrary files and programs via a .SWF file containing the undocumented "save" FSCommand. (CVE-2002-0476)
        • Standalone Macromedia Flash Player 5.0 before 5,0,30,2 allows remote attackers to execute arbitrary programs via a .SWF file containing the "exec" FSCommand. (CVE-2002-0477)
        • Undocumented API functionality to write, or execute a file.
          • FSCommand("exec","rundll user.exe,exitwindows");
          • FSCommand("save",“C:ilename.txt")
        • FSCommand function only present in the standalone player API.
        • Web browser unaffected.
    • Exploits in Flash
      • Flash ActiveX v6.0.23 Parameter Stack Overflow (CVE-2002-0605)
        • Long ‘movie’ tag parameter.
        • <param name=movie value=“AAAAAAAAAAAAAAAAAAAA....&quot;>
      • Heap Overflow in malformed ‘length’ SWF header. (CVE-2002-0846)
        • SWF header contains a ‘length’ value of the .SWF file.
        • Define length shorter than the .SWF file, Malloc() overflow.
        • User supplied value un-validated and used directly in memory allocation!
      • Multiple overflows Through Malformed SWF Headers (CVE-2002-1382)
        • Three SWF header values vulnerable to memory corruption.
        • Same bug, different variable, three months later.
        • Flash appears to rely on user supplied values for memory length calculations.
    • Exploits in Flash
      • Bypass Same Domain Policy (CVE-2002-1467)
        • Read arbitrary files from disk using Flash.
        • Flash security prohibits .SWF content from one site, accessing content from another.
          • Flash will follow a 302 HTTP redirect to file://
          • &quot;file://&quot; base in a web document
      • Flash Denial of Service (CVE-2002-1625)
        • Flash Player 6 never terminates a connection to a remote website when using.
          • loadMovie()
          • loadSound ()
        • First Flash DOS tool. loadMovie(“http://www.blah.com”) Loop.
        • Dumb mistakes…
    • Exploits in Flash
      • 2003: First Flash Cross-Site Scripting Bug
        • XSS vulnerability in Macromedia Flash ad user tracking capability
        • Allows remote attackers to insert arbitrary Javascript via the ClickTAG field.
        • ClickTAG used to notify a website prior to Flash execution.
        • http://www.example.com/victim.swf?clickTag=http://adnetwork.com/tracking?example.com
        • http://www.example.com/victim.swf?clickTag=javascript:alert('aaa');
        • Flash developers appear to be unaware of Cross Site Scripting
        • Basic XSS attack vector, nothing fancy here..
        • Quick pre-release code analysis would have found this.
        • Or a secure coding methodology…
    • Exploits in Flash
      • Flash v6 ActiveX Malformed SWF Header (CVE-2005-2628)
        • Malformed SWF header with a modified frame type identifier.
        • Flash still fails to validate SWF file format.
        • Now 3 years after original .SWF file format bug found.
      • Multiple unspecified vulnerabilities in Adobe Flash Player 8.0.22.0 (CVE-2006-0024)
        • ‘ Remote attackers able to execute arbitrary code via a specially crafted SWF file.’.. And again..
      • Stack overflow in Adobe Flash Player 8.0.24.0 and earlier (CVE-2006-3311)
        • Execute arbitrary code via a long, dynamically created string in a SWF movie.
        • Stack overflow in the ActionScript 2 API.
    • Exploits in Flash
      • Malformed SWF File in Flash 8.0.24 (CVE-2006-3587)
        • Malformed .SWF file causes memory access violations.
        • More malformed flash..
      • Malformed SWF file vulnerability in Flash 8.0.24.0 (CVE-2006-3588)
        • Allows remote attackers to cause a browser crash via a malformed, compressed .SWF file.
      • Flash ActiveX Flash8b.ocx Browse Crash
        • Long string in the Flash8b.AllowScriptAccess method.
        • Second Flash ActiveX method to contain a stack overflow.
    • Exploits in Flash
      • CRLF injection vulnerability in Flash Player 9.0.16(CVE-2006-5330)
        • Remote attackers can modify HTTP headers of client requests and conduct HTTP Request Splitting attacks via CRLF injection in ActionScript functions.
          • XML.addRequestHeader(“aa%0D%0AFoo: bar”) ; Adds header Foo: bar
          • XML.contentType(“aa%0D%0AFoo: bar”); Adds header Foo: bar
        • Flash does not validate user supplied content for CRLF.
        • Flash does not have any special character blacklist
        • Special chars and binary data are often accepted.
      • Malformed SWF File (CVE-2007-0071) Adobe Flash Player 9.0.115.0
        • Allows remote attackers to execute arbitrary code via unknown vectors related to &quot;input validation errors.“
        • Another SWF with a modified header value.
    • Exploits in Flash
      • Insufficient Input Validation Allows CSRF (CVE-2007-3457)
          • Flash insufficiently validates HTTP Referrer headers for CRLF. (AGAIN!)
          • Allow remote attackers to conduct a CSRF attack via a crafted SWF file.
          • 2 nd CRLF bug, 2 nd HTTP Referrer bug!
        • Flash Player 9.0.48 HTTP Request Splitting Attack (CVE-2007-6245)
          • Remote attackers can modify HTTP headers for client requests and conduct HTTP Request Splitting attacks.
          • 3 rd CRLF bug, 3 rd Header bug.
        • Flash Player Malformed SWF File (CVE-2007-6019)
          • Improper object instantiation allows remote code execution.
          • Modified DeclareFunction2 ActionScript tag.
          • Access an object before it was properly instantiated.
    • Exploits in Flash
        • Multiple Cross Site Scripting Vulnerabilities in Flash ActiveX 9
          • Remote attackers can inject arbitrary web script or HTML via:
            • navigateToURL(), asFunction()
          • NavigateToURL, takes two arguments, URL, browser frame.
          • NavigateToURL accepts javascript: URI’s and arbitrary browser frames.
          • JavaScript executes in security context of named frame!
          • Should execute in the security context of the page that embedded the SWF!
            • Evil.swf advert located on myadverts.co.nz is served on mybank.co.nz
            • JavaScript within evil.swf can execute in the context of MyBank.co.nz
            • All your money is belong to me?
    • Exploits in Flash
        • Interaction Error Between Adobe Flash and UPnP Services (CVE-2008-1654)
          • Flash can be used to send SOAP XML requests to arbitrary addresses, including internal addresses. 
          • How about reconfiguring your modem, using SOAP over un-authenticated UPnP functionality?
        • Example: http://www.gnucitizen.org/blog/hacking-the-interwebs/
          • “ Exploiting the BT Home Hub with Flash”
          • Reconfiguring the BT Home hub primary DNS server remotely through the Flash player, over UPnP.
        • 2Wire Modem DDOS Virus
          • Reconfigure modem to send 10,000 ‘test’ pings to www.cnn.com
        • Flash lacks cohesive security ‘zones’ and network sandboxing.
    • Exploits in Flash
        • Mark Dowd – Weaponised Flash NULL Pointer Attack.
          • 25 page paper on exploiting Flash (worth reading, if your into it)
            • http://documents.iss.net/whitepapers/IBM_X-Force_WP_final.pdf
            • ‘ The Inhuman Flash Exploit’
          • Un-validated user supplied value used as memory allocation size.
          • NULL pointer returned when allocation size is greater than 2gig.
          • Returned value + user supplied offset used in memory write.
          • Append malicious ActionScript byte code to valid Flash byte code.
          • Bypass internal Flash verifier.
          • Native code execution inside the ActionScript VM.
          • Internet Explorer, FireFox, Vista, XP = owned.
    • Statistical Analysis of Flash
      • Brief Highlights of Flash Security Advisories.
        • Too many advisories to detail each one.
        • 54 advisories since 2001
        • 2003-2006 ActionScript 2
        • 2006-Today ActionScript 3
        • More Functionality = More Exploits
    • Statistical Analysis of Flash
      • Most Common Bugs?
        • File Format Validation = Malformed Flash Files
        • Browser Input Validation = XSS, CSRF, etc
        • ActionScript API = Native Flash Functionality
        • SandBox Violation = Escaping The Flash SandBox
    • Statistical Analysis of Flash
      • How Many Of Those Bugs Can Be Used To Execute Code?
        • 48% of Flash vulnerabilities have been exploited to gain code execution!
        • Weaponised Flash exploits not uncommon.
        • Flash is not compiled with ASLR /DYNAMICBASE support.
    • Exploits In Flash
      • Common trends:
      • Flash has poor SWF file format validation.
        • User supplied values frequently used in memory calculations.
        • Majority of vulnerabilities stem from file format validation bugs.
        • Malicious Flash is most likely to be ‘malformed’.
      • Adobe/Macromedia have a poor Security Development LifeCycle.
        • Flash contains basic vulnerabilities, XSS, CRLF, Stack Overflows
        • Vulnerabilities repeat themselves, often! Adobe do not learn.
        • ActionScript API is being used natively as an attack vector.
        • Flash security sandbox has been escaped three times!
      • Flash ActiveX plug-in has the most issues.
        • Flash security flaws have increased drastically.
        • Almost half of vulnerabilities allow code execution!
    • Exploits In Flash
      • Flash ActiveX Plug-in has the most issues.
        • Twice as many as the FireFox plugin.
      • Flash Security Flaws have Increased Drastically.
        • Almost half of vulnerabilities allow code execution!
        • New method of native Flash VM code execution (Mark Dowd’s)
      • 2008?
        • ActionScript 4 is likely 2 years away (Based on past history)
        • Flash will grow, more functionality, bigger API.
        • Competing with Silverlight (Microsoft’s Flash)
        • Expect more Flash bugs.
    • Exploits In Flash
      • Possible Exploitation Scenario.
        • Evil Hacker finds .SWF file format validation bug.
        • Stack overflow, code execution.
      • The Exploit:
        • Legitimate Flash ‘advert’ created with exploit code.
        • Exploit only triggered if(date > two weeks time)
        • Evil Hacker buys $250 of advertising for malicious SWF file.
      • You:
        • Monday morning, you visit xyznews.co.nz, Flash anner adverts.
        • Today is > two weeks since campaign launched.
        • Exploit code is served from Flash advert, remote code exec.
        • Everything looks normal, nothing crashes, but your owned.
        • Case of the Monday’s?
    • Exploits In Flash
      • Recommendations:
        • Keep Flash up to date, updates fix critical bugs.
        • Disable Flash on critical systems.
        • Implement browser virtualisation.
          • Risk mitigation.
          • FireFox/IE inside VMWare.
        • Be weary of arbitrary Flash content.
        • Flash Virus/Worm is just a matter of time.