Where he breaks out some of the other tools that are always handy on a breakout job, the amount of times that the dsquery line has come in handy on everything from breakouts to redteam engagements is insane.
What is new however is me losing my damn notes file on them, thankfully it seems Microsoft has published their own notes so for those of us with rubbish memories…
I recently put together a presentation for work to try and instil some more intelligence into folks hashcracking attempts beyond just throwing the largest dictionary possible with a massive ruleset against it and calling it done.
As part of that talk I raised the point that installing the Intel OpenCL runtimes for your CPU doesn’t have to be the be all and end all. If you don’t mind a bit of kernel module compilation, you can also have your intel hd graphics do the heavy lifting and you’ll notice some performance gains above your CPU.
I last did this a year or two ago and it was incredibly mandraulic and painful, but it turns out there is now a script (or i just plain missed it the first time around) available by intel that providing you’re using one of their “supported” platforms you can run and it’ll handle the dependency hell and installation of the custom kernel.
You should note, Hashcat considers the intel gpu runtime to be broken and while booted into the 4.7 kernel I don’t appear to be able to force the selection of my CPU for cracking, though it is listed as an opencl device so whether you still want to go ahead with this is up to you.
First… holy balls I have a blog still. No posts in ages (well 2016 but that post was written originally in 2013)!? crikey! Thing is life got in the way and information got shared and noted via other means. This doesn’t mean I wanted to leave me blog in the dust but it did mean that a quick message to a WhatsApp group or email to work colleagues was probably easier to share information than sitting down and penning a blog post.
Anyway lets get to it…
So this originally stemmed from questions from a colleague regarding a kiosk breakout he was doing and me talking about abusing popup bubbles and boxes to attempt to break out of restrictive environments. What causes a popup bubble? well many things, including that of a CD-Rom being inserted.
So an idea formed in my head, maybe we can abuse autorun.inf still to help us in a bid to breakout of a lockdown. Turns out it lead me down a bit of a rabbit hole and I think I now have a “thing”.
Thing? or not a Thing?
So this is the question, I’m interested in your opinions if you read this at all. Is this a thing? should I be considering this a thing? Because it just doesn’t really sit right with me, I can’t help thinking that “this is by design” but if it is then I think the design needs refinement.
Have a read of what follows and see what you think.
AutoPlay vs AutoRun
This probably isn’t news to anyone but back in the day (prior to 2010) you used to be able to write yourself a lovely little autorun.inf file that could specify a few items and you’d have yourself a USB key for example that would execute a malicious payload the moment it was mounted.
Microsoft got wise to it and disabled autorun on devices with a device type of removable_drive(1) via a patch on Windows XP.
To enumerate device types use the following powershell command:
Fixed, Removable and CD-ROM device types will be listed.
It replaced it with a feature called “AutoPlay” which instead of automatically executing whatever file was specified within the autorun.inf the operating system would present a menu to you in order to choose your action.
Now you can set a default action for a particular type of media but generally the menu always appeared.
Type of media? what do you mean?
So AutoPlay would categorise media based on the files contained within the media itself. There are 3 main types:
and a fourth special primary type of “mixed”.
If media matched any of the first 3 types, a default set of menu options would be presented, generally “view photos”, “play audio via …”, or “play video via …”. If the fourth special type matched a menu would present itself offering the user to open the folder to view the files in windows explorer or do nothing.
There are other “types” including the ability to define other types within the registry but this article is taking place from the perspective of not having prior access to the devices.
Essentially it seems windows attempts to do content-sniffing of media content and acts appropriately. however that doesn’t lend itself well to people who produce software installations via CD, they still wanted to be able to make installation an easy process for any user so Microsoft catered for it.
On a USB key you’re by default presented with a fixed menu that is wholly determined by the media type and I don’t believe you can change this (aside from a little trickery that others have done using U3 style devices) On a CD however, things change, you can specify custom actions
So Microsoft offers folk the ability to customise the actions that can be performed when a CD-Rom is inserted, these options are still defined using the autorun.inf file and even makes use of the same terminology, retaining backwards compatibility with older CDs. So you have two basic options.
Open – specify an executable to run on insertion of CD
ShellExecute – Specify a file to open on insertion of CD, relying upon the OS to determine the default file handling application.
We’re particularly interested in Open in this case but i’m sure ShellExecute could prove useful in some cases.
First Attempt at Weaponisation
With the basics of autorun.inf understood. i’m curious what can we do with this that may be different to traditional use of autorun.inf? From reviewing the autorun.inf documentation on technet it became apparent that the Open command will happily take a filepath, not a relative one but a full filepath, allowing you to specify any executable on the host to run.
Wait, a CD-Rom can run any executable it likes on the OS as part of the autoplay feature?
Well that’s useful if we’re trying to pop out of a restricted environment and being unable to browse say the local filesystem, if we can get autoplay to pop, a click later we could be running powershell, iexplore.exe or any other exe that will enable us to breakout, depending on GPO obviously.
Okay, chances are if autoplay can run it, we could find other ways of calling those apps but hey, it could result in a quick and easy insert cd and pop out of the restriction.
Back to reading technet and this gem stuck out from within the Open parameter description:
You can also include one or more command-line parameters to pass to the startup application.
So as a default thing, I can get a menu entry on autoplay to attempt to execute any OS executable complete with a nice list of arguments and my CD doesn’t even need any content beyond an autorun.inf file?
This sounds ripe for abuse and this is where a bit of inside-the-box thinking comes into play.
Subtee – A man who has gone to town on windows executables and bypassing DG/Applocker/SRP has a few tasty ways of getting scripting languages to pop on a box. Let’s take what he’s taught us over the last few years and put a little something together.
Okay so we’ve got something here, problem is, it looks dodge as hell as it comes up as mshta.exe, the “Published by Microsoft Windows” bit is a nice touch however, adds some legitimacy to the whole affair and I guess its a consequence of using a signed binary.
Lets see what we can do to make it look a little better.
Keeping up Appearances
Using the same technet resource as before we can see a few other options available for us.
We can customise the “action” text associated with an autoplay entry.
So “Execute mshta.exe” can be changed to say “CLICK HERE FOR FUNTIMES!” or more usefully, “Open folder to view files”.
We can also customise the icon displayed associated with that default action and this is where a little bit of recon for your targets may come in handy as the icon associated with the “Open folder to view files” action varies based on OS.
So a few changes later, our autorun.inf file looks like this:
action=Open folder to view files
and we’ve for argument sake included the icon file on the CD itself, its not malicious it should never be flagged.
I’ve set up a nice internet hosted script that will be grabbed by the exploit code (yay for proxy aware executables!) and now for the final reveal.
Final bit of dressing up is asking explorer.exe to pop open and display the CD Drive, luckily because the working folder is in fact the CD drive itself we can easily do this by just appending explorer.exe to the end of our payload.
With a little bit of luck (we can make it through the night) and a little recon via email and monitoring user agents we can develop a completely benign CD targeted against our specific client infrastructure that if scanned won’t flag to AV because autoruns.inf isn’t executable right? that actually runs malicious code should the user click the default action associated with the CD (This was tested against windows defender, your mileage may vary).
If the user chooses not to answer the popup, and double clicks the CD instead, it’ll also run the action.
Final video of exploitation is here.
I also noticed a few things I forgot to point out at the end of the last vid so here’s an addendum 🙂
So this is the awkward thing, anyone in the UK doing red team engagements is probably aware of the dangers of the traditional “USB DROP” in the car park. It’s dangerous, can result in malicious code being executed on non-target PCs and generally iffy.
Also most people these days undergoing security awareness training have it drilled into them that USB devices are bad and shouldn’t be plugged into corporate machines.
Then there is the disabling of USB devices, no USB Mass Storage Drivers, etc. DLP technologies.
The beauty of a non-writable CD-Rom it’s seen as benign, okay sure i’ve worked in places where executables hosted on a CD-Rom are deliberately prevented from executing, but this isn’t hosting any executables. This attack method doesn’t introduce anything into the environment via CD-Rom beyond a little one-line script/shortcut execution.
Yes CD-Rom’s these days are falling out of favour, Yes you can use this with other techniques that turn USB keys into CD-Rom appearing drives (2), but this is targeting the Receptionist’s PC.
We’ve established carpark drops are iffy, what can we do as a red teamer or SE person to ensure our payload gets delivered to a less iffy location?
Why not just walk in and hand it to someone?
Me: “Hi, er I think this CD may have come from one of your staff members. I found it in the car park”
*hands CD to receptionist*
Me: “Looks like it’s wedding photos, i’d be devastated if I lost mine so thought I’d try and get it back to them”
Receptionist/Security: “Sure! Thanks, no worries i’ll see if it’s any of our employees”
CDs weren’t covered in their last e-learning on Security Awareness Training
You’ve given the CD directly to an employee of the company
You’ve given a back story that encourages the employee to view the wedding photos to identify a staff member.
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!
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 🙂
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 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.
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.
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 post this is no longer a problem.
Problems always come in threes so what is problem 3 you ask?
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:
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.
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 😉
and hit enter.
And finally, do what the message says, click continue…
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.