NFAL: Episode Two (Point 5) – Breaking out of the Jail

Foreword:

I started writing this blog post a long time ago (October 2013 wordpress tells me) and figured it was about time I published it just to clear my decks of “draft” posts as it were. I intend to publish things more often but maybe not all Pentest based, some ham radio and electronics gumpf may filter into it as those are also hobbies of mine.

With that and the slight addition that this was going to be NFAL Episode Two on it’s own so its now kind of NFAL Episode 2.5 The continuing adventures of noddy testing… on with the original post!


Background

Forgive me if this comes across as teaching all 1 of my readers to suck eggs but this is just a dump of common ways I often find useful for breaking out of kiosk jails.If you’re a penetration tester or even a savvy user, chances are you already know of these methods but this is noddy stuff, purely because I thought it made for a fun blogpost, it was fun playing with it on client systems at least.

I did this as a talk at an internal company training day and titled it “Smashing Windows” slides for the talk will be attached at the bottom of the blogpost for what it’s worth but I’ve no recording of it and this blog post is essentially just it regurgitated from memory ๐Ÿ™‚

Recently I did some testing involving the “Remote Application” features of terminal services through a terminal services web gateway.

Initially logging in using AD credentials on the front page you’ll be presented with a few icons on the webpage which in turn launches applications. (Similar to CITRIX stuff i’ve seen in the past). You get presented with a full application as if it is on your desktop, similar in the way VMWare Fusion works on the Mac, its not a full “session” but rather an “application session”.

The beauty with it (at least from our point of view) is that File – Open, will open files on the remote server (providing they haven’t GPO’d paths out of the address bar, etc).

Spawning any processes will spawn them on the remote server and present them to you over terminal services. So if you get an external link to click, it’ll spawn IE which again will be on the remote server.

Another thing to note is that the processes you’re spawning will be on the application server serving that particular application not the web host that is just presenting the applications.

For a recent client I had access to about 6 different applications each one hosted by a pair of load balancing application servers. So breaking the jail on one, got me MSTSC and I just logged in using that into the other application servers/etc that made up the network (having a nice portable portscanner/discovery tool is very useful at this point).

Method #1 – Open Sesame

The File Open and File Save dialogs are king. If you have access to one of these you’ve basically got a mini explorer.exe. There are several avenues of attack.

The File Open dialog box, a veritable feast of juicy jail breaking goodness.
The File Open dialog box, a veritable feast of juicy jail breaking goodness.

The Orange Box – Known as the breadcrumb, this little thing normally is affected by some GPO and is limited in use but can be handy hopping back up the directory structure.

The Yellow Box – Filename box, Unlike the breadcrumb this one appears to be affected by different GPO policies and is not always locked down. I have been able to browse to C:\windows\system32\cmd.exe in here when the breadcrumb wouldn’t let me out of my own profile. Try typing exact paths to existing files and you may find yourself lucky.

The Red Box – Search and Help. Two great ways of breaking out of the jail. Search can often get you files, providing your “high” enough up the tree. Help can find you ways of popping Internet Explorer open. So can search if its unsuccessful finding files, it’ll often prompt you for “search online” which will likely result in IE spawning.

The rest… it’s unlikely you’ll get a nice folder pane on the left hand side, normally you’ll end up with some basic folders available but no ability to browse out of your user profile if its locked down, but its worth a quick look and the file type box, that will limit you when writing a file or saving one. If it has an “all files” option, that’s better.

Finally right click! try it… if you’re lucky you’ll be able to write a file, rename it to .bat or .vbs, get some script running commands for you, its a long shot but hey it might work.

Method Two: IExplore.exe your hard drive

Aside from the usual address bar file://c:\ or browsing to your own metasploit browser autopwn. There are also ways and means of breaking out of this that aren’t so obvious.

File – Open… Or the address bar, IE can open any files. It’s not limited by file filter, it can also open network resources just fine and view folders. Great for accessing hack armoury resources.

Drag and drop… Want to exploit the file “open with” dialog? Drag and drop an unknown file extension onto it and it’ll pop it right up after you hit “open”.

Working on an embedded windows client (*Cough* Embedded XP Wyse Terminals*cough*) and have no access to the file system? That sucks. Try tools – Internet options, open objects and open files will often net you two different drives, the first being the system ram drive, the second being your user profile area.

IE-objects-files-jailbreak

Finally, have access to the file system but still can’t spawn anything interesting? Try firing up word or any of the office suites, how?… Look for “read me” and licence files.

You may get lucky and find some .doc style terms of service links or be able to create your own .doc. Once you’re in word go for macro execution and you’re winning.

Method 3: If in doubt… give it a clout!

Also consider the windows error reporting dialog, on one particular job I couldn’t access notepad.exe myself and the file open dialog I had access to could only see *.acme files, so was pretty useless.

Help and support was disabled so help got me nothing, however entering in a string instead of a number into an input field of the application would cause the application to crash and the windows error reporting window to pop up from there I viewed the microsoft privacy policy and pow… Internet explorer! which lead me onto bigger and better things ๐Ÿ˜‰


Powerpoint Presentation: Smashing Windows

NFAL – Episode Three: Testing websites while on locked down clients

Or… Yet Another GPO Bypass Technique.

On occasion I get given the task of testing a client’s website using the terminal provided by said client in order to in the client’s words “Prove what a malicious user can do with the tools we give them”.

So in order to not drive myself mental trying to pentest a web app manually in IE, without being able to change any settings. I work out a way to get burpsuite on the box.

The beautiful thing about burpsuite being that it’s JAVA and java.exe happens to be one chuffing huge hole with endpoint protection mechanisms and application whitelisting.

Okay so problem 1 solved.

Onto problem 2 now, they lock down their “connections” tab in internet settings but as we already know how to bypass whatever pre-existing proxy connection they have and replace it with our own burpsuite details using a little VBA and the techniques given in this postย this is no longer a problem.

Problems always come in threes so what is problem 3 you ask?

This:

IE: "You Shall Not Pass!!!" Me: O RLY?
IE: “You Shall Not Pass!!!”
Me: O RLY?

Or more specifically, the distinct lack of a “continue” link to allow us to ignore the self signed cert warning and continue with our traffic being intercepted by our burpsuite proxy.

This situation is actually a product of the following GPO setting:

It took me far too long to find this damn setting in GPO :)
It took me far too long to find this damn setting in GPO ๐Ÿ™‚

Anyone who’s been around any length of time with IE probably already knows that this error page is a resource loaded from a local dll. This is true for every “friendly http error” message you get in IE.

Question is, how does the DLL know not to show the “continue” message?

It does it by a variable within the URI, what variable? the “PreventIgnoreCertErrors” variable. This variable is usually not shown with the error message unless the GPO setting is set to enabled.

IE: YA RLY!
IE: YA RLY!

So you know what is coming next, yup. Copy Pasta my friends, So copy & paste and remember to change the damn variable to 0 before taking a screenshot ๐Ÿ˜‰

WHAAARRRGARBBBBLLL!
WHAAARRRGARBBBBLLL!

and hit enter.

Open Sesame
My mind’s telling me no, but my body, my body is telling me yessss!!!

And finally, do what the message says, click continue…

IE: NO WAI!!!! Me: Ya... Wai.
IE: NO WAI!!!!
Me: Ya… Wai.

Voila! Now you can test with your self-signed burp certificates or bypass yet another security control (that is actually a fairly wise one to have) on your network.

SteelCon 2015

So its the day after the conference and I sit here in bits. Unfortunately since friday i’ve been struck down with an attack of sciatica however I downed my ibuprofen along with a few paracetamol for good measure and drove the many hours up’t north and found myself in Sheffield at the best conference I have had the pleasure of attending thus far.

Robin (@digininja) appears to have taken all of the best bits from every conference out there and packaged them into one incredibly affordable weekend.

It started on the friday when arriving up in sheffield, the actual real conference starts on the saturday but there is a well publicised “pre-con” meet up in a local tavern. The best bit about this being a relatively new to the field (4ish years now) and shy as hell i’m not exactly known to anyone. I’m not in the league of sausages, I know a few testers and I can now recognise a few of the twitter legends I follow, but I’m not exactly on any invite lists for pre-con meetups or beers.

All of that doesn’t matter here, as its a publicised meet up, everyone rocks up and all of a sudden I’m talking to folk such as digininja, Finux DaveHardy20, FreakyClown, etc… people i’ve followed since starting out in the world of infosec, over a few beers and shooting some pool.ย  There are no barriers and for someone who suffers from extreme social anxiety usually, I found it brilliant.

Saturday came and wow… again a brilliant setup. Breakfast provided for the attendees, a kids track that resulted in some AWESOME lego robotic RUBIK cube solvers, fantastic conference loot (loving the lockpicks from Mad.Bob) and a keynote by the one and only Campbell Murray (@xyz2k). Refreshingly a well balanced technical talk but also not too heavy for the first talk, opened the conference with a good few laughs #blindslided and left me nodding my head excessively at everything he had to say.

The Gist: Penetration Testing was never meant to be a test of compliance. (Checkbox Pentesting) and Red Teaming as we (the industry) call it is NOT Red Teaming…

Analogy: Red Teaming is taking a block of thermite to the hinges of a safe door and smashing it in with a sledgehammer

it’s how penetration testing should and used to be with a wide scope, a definition of the client’s crown jewels and an allowance for the testers to make use of their imagination, not for them to be constrained to arbitrary compliance objectives, low costs and unrealistic timelines.

Following up that talk I watched an exceedingly knowledgable Darren Martyn (@infodox –ย http://insecurety.net/) give a bloody blinder of a talk on hacking embedded devices. Not a talk aimed at those of you with exceptional hardware hacking experience but rather aimed at the low hanging fruit, throughย  a series of examples and a detailed case study he illustrated just how easy it is to find these flaws and then to exploit them. If you run a home router, chances are it’s part of someone’s botnet, this stuff was ridiculously easy to do and has made it firmly onto my “to-do” research list.

A few more talks and a lunch that had more than enough food to share amongst the numerous attendees the next talk worthy of particular mention for me was Dave Hardy’s and Ben Turner’s talk on powershell and their work with the metasploit framework. These chaps have taken metasploit’s capabilities with powershell and made it bloody brilliant.

Gone are the days of running a single script and bodging scripts to work. They have created a full blown new “payload” type which returns you a full powershell session with backgrounding, the ability to actually interact with the objects returned as and when you require them and a whole series of utility post modules/scripts that make life even easier.

Evading AV? Powershell is easy mode right now for doing that, these chaps have modified inveigh (read: responder using powershell) in order to work appropriately with the new payload type, you can now invoke-mimikatz within a powershell session and essentially given the armoury of powershell scripts out there, you basically never have a reason to touch disk and therefore never get caught by AV.

Seriously, I can’t do their work justice with a simple write up as part of a post here but check out their websites and get the info.

http://www.hackwhackandsmack.com/
https://pentestn00b.wordpress.com/
https://www.nettitude.co.uk/interactive-powershell-session-via-metasploit

So that brings us to the closer where Harold and Kumar (FreakyClown and Dr Jessica Barker) went to White Castle and taught us to burn the motherf…ker down #pookie. Or rather gave us a disturbing account of how the infosec world could go. The issue we have as an industry is trying to sell what is basically ineffective, we scare-monger users and our sales staff promote new shiny bleeping blinky products until they are blue in the face but people don’t appear to respond as we believe they should and we say that it’s their problem. It isn’t, it’s ours and we as an industry need to drive a new approach.

Roll on to the evening party where netitude placed ยฃ3k behind the bar, I believe we achieved the goal of drinking the bar dry by about midnight. It was a brilliant evening, starting with a scavenger hunt, Dr Jessica Barker (@drjessicabarker) and FreakyClown (@__freakyclown__) led us all once again only this time into a quiz that proved I do not know my game consoles anywhere near as good as I thought I did but oddly I do know that Coco Chanel was the inventor of the Trouser Suit and “purdy” is a haircut. ๐Ÿ™‚

Throw in some copious amounts of drinking with a few chaps from Prospective Risk, Netitude and others while being expertly chaperoned by a member of the SteelCon day staff who’s only name I remember is “Laura” and “Woody”.

"The FlatCappers"

The “Flatcappers” (the conference badge was a traditional flat cap) partied the night away and it all ended for me in the early hours of the sunday morning where I was left wondering “wtf!?” as we emerged to bright sunlight.

05:10am… bedtime, thank goodness for late checkout ๐Ÿ˜‰

A truely fantastic conference with the right mix of tracks, talks and one that doesn’t just focus on the 9-6pm conference but one that really put the effort in around the sides to provide a cracking experience that will have me smashing that F5 key once again to grab a ticket next year.

For those of you that want more, on the Sunday they also had laser tag/quasar activities and pizza lunch planned out, I myself opted to sleep and neck paracetamol ๐Ÿ˜‰

After a weekend of activity, my sciatica attack never did end and I was left crawling out of my car this evening poking at my medicine cabinet unable to stand up properly, trying to knock the dihydrocodine off the shelf so I may get some relief.

I may be in agony but every minute was worth it. I learned so much in the company of so many excellent people, it was worth every wimper.

Quickie #3 – An Update of sorts

Bandwidth Exceeded

So if you’ve recently tried browsing to my site in the last 30 days or so you may have been presented with a not so helpful error message showing that my bandwidth had been exceeded.

Turns out my site was the victim of a dDoS attack/bruteforce at the end of May/Beginning of June and initially while my hosting provider noticed it and informed me of the attack, the “fix” I implemented which was to eliminate xml-rpc.php from my wordpress site initially showed a huge drop in CPU cycles from the hosting PoV, what I didn’t appreciate is that error pages come out of your monthly bandwidth entitlement.

So… 12 hours later a grand total of 5GB of “404 – page not found” texts were downloaded and pow, site was down.

Hosting provider has been a great help throughout the attack and while there were some false starts and confusing conversations going on I finally got through to their support ninja’s had my “fix” confirmed as working and my site is now up and running, at least until someone takes it upon themselves to burn it down or have another go at logging in.

The fix…not using .htaccess to deny (that results in burning your data allowance, but does reduce CPU load) but rather use .htaccess to perform a 302 to http://0.0.0.0 for any matching request.

MWR HackFu 2015

I was invited along to HackFu this year and spent a hugely enjoyable 3 days. MWR Infosecurity definitely know how to run a major cybersecurity event and while a majority of us were penetration testers or security researchers teams were mixed with software developers, mathematicians, etc… even those who did not have a technical skillset could learn new skills such as lockpicking or use their powers of deduction to discover clues and work out who were the moles and the mastermind behind it all.

Incredibly well structured and the challenges I took part in were so well thought out they’ve given me a few good ideas to put together one of my own. From interfacing with game AI to produce “real world” effects from associated hacks to emulating ICS systems having to hack a water pump to retrieve a usb key.

Honestly, if ever you get the opportunity to participate in it, leap for it and go expecting the unexpected ๐Ÿ™‚ Genuinely a fantastic time.

Press Article:ย SC-Magazine Write Up

Quickie #2: Virtualbox VRDP & CTRL-ALT-DEL

I run a headless install of virtualbox with phpvirtualbox as the front end to it at home on an old N54L microserver (16GB ECC RAM, 2TB Raid 5 Array, Ubuntu Server LTS), it runs beautifully aside from one thing.

It uses VRDP (which is a bloody neat solution, I love it) to show the consoles and CTRL-ALT-DEL doesn’t actually get sent to the host.

Instead, use CTRL-ALT-END and that’ll see you right.

That took a keyboard mash and a bit of googling to find that one.