Summary of my Windows Store App security BlackHat talk

 

Last week, I spoke on the security implications of Windows Store apps for Windows 8 at BlackHat Europe. Running the risk of ruining the suspense for later listeners, I decided to take the advice of several of my attendees and summarize my main points here.

Remember, this is just a summary. I am boiling down a 60 minute talk into 12 or so talking points. If you have questions about specifics, ping me in the comments or via the contact form.

Some of this is original research, some of it is just from the documentation, but all of it applies to the security or privacy of Windows Store apps on Windows 8. Doesn’t matter what you think of Windows 8, you will have to deal with it eventually. It is growing faster than XP or 7 did. The store is selling stuff. It is out there. You will have to either scan an app for your company, or deal with BYOD.

This is all about helping you out.

Features with a risk component

  • You log into a Windows 8 machine with your Microsoft Account. Apps have access to the account information with only a request at install time. Are your users logging in with personal accounts? Company accounts?
  • Capabilities need to be used sparingly. Least Privilege is the rule, not the exception.
  • Remote Settings stores the data saved to it somewhere in the cloud.
  • Local Settings are saved in an unencrypted XML file.
  • The applications themselves are saved locally with source code available or easily obtainable. Code defensively!

 

 

 

 

Testing Windows Store Apps

  • Test backend services with Burp or ZAP.
  • Test for the same vulnerabilities you test your web apps for, manually for now.
  • Do a code review.

 

 

Countermeasures provided by WinRT

  •  Hashing and encryption are in Windows.Security, but are sloowwww.
  •  Instead of Microsoft Account, use OAuth for auth-n
  •  Apps that come across an unexpected error, don’t leak information. They just die!!

 

 

There you go. If you didn’t make it to my talk, you don’t need to go to a later rendition (although the demos are pretty awesome). I just want to make sure that people understand what they are getting into with Windows 8 apps.

Are you doing Windows Store app research? If so, drop me a line. You can find me @sempf on Twitter, or use the contact for on the blog here – it works good.

 

Why I went back to Android from WP8

At BUILD 2012 Microsoft gave me a Nokia 920 Windows Phone.  Ever since then I’ve been using as my primary cell phone.  It has had ups and downs, but in general I enjoyed very much.

Originally, I was using a Samsung Galaxy Nexus.  That phone had served me well for many months before I switched to the Nokia.  I wanted to give the Nokia a fair shot, because I really believe that Windows Phone can succeed.  Although it was a good run, there were several things that made the switch back necessary.  Let’s start with the good things first.

The good

First, the phone is truly beautiful.  I don’t just mean well-built. I mean everything about it is truly amazingly beautiful.  The device itself, the screen, the applications, the start screen.  Everything.  It’s a joy to use.

Second, the integration with Microsoft products is a very impressive.  The office tools work very well.  Skype and Messenger are very good.  The Xbox integration is truly incredible.  Microsoft has done a very nice job of making the Windows Phone platform part of the full Windows suite of products.

Third, despite what people say, the selection of applications is very impressive.  I have yet to find more than one significant application but I need that isn’t in the window store.  The only thing I ever found that was missing was Wuala, but with the weaknesses in Java I switched to SkyDrive anyway.

The bad

Despite the fact that the user interface is very smooth, the whole phone updates very slowly.  It takes a long time to update the applications.  Text messages come in the wrong order.  E-mail takes a long time to synchronize.  In general, network activity is less than wonderful.  When the phone goes to sleep, it forgets a lot.  A lot more than it should.  Every time I wake it to use it have to wait for it to remember what network it’s on, what wifi I was using and what I was doing last.

All of those same lines, and synchronization is very weak.  Trying to get service driven applications to get new data and refresh the cache is very difficult.  If the application developer fails to give you an explicit synchronization option, you’re often out of luck. Often, I had to restart the phone to get things updated.

While there are no lack of applications in the store, developers are not keeping up with new trends.  For instance, there’s no Pebble app for the windows phone.  Windows Phone is still the last in line to get an app for a new online tool, if it ever gets one at all.  I’m not really an early adopter so this isn’t a huge deal for me, but occasionally I’d like to see some of the new stuff that’s out there.  It’s frustrating that I never seem to be able to.

One more thing.  The phone is absurdly heavy.  I know that’s a small thing but after a while it gets to you.  It’s amazing how six ounces matters. Makes my pants fall down.  Nobody needs to see that.

The ugly

The phone reboots 10 times a day.  This is a not the huge problem for me it is for some people because I am not a heavy phone user.  It can get frustrating when I sit down for short ‘break’ (you know what I mean), launch Angry Birds, and immediately get to watch the phone reboot.  Where it really becomes a problem is when some call comes in, and the phone reboots.  This happens to me least once a day.  I have more than a few uncomfortable moments having to call somebody back and explain that my phone reset.

A huge problem is the lack of S/MIME support.  There is just simply is no way to send secure email using Windows Phone.  Yes I’m aware that I could write an application for S/MIME.  But that’s not really my area of specialty in programming, and I have other things I need to write more.  It seems like S/MIME is something that should be supported out of the box on any platform these days.  I mean come on, even Windows Mobile 5 supported S/MIME.

The real nail in the coffin for me is the lack of integration with other e-mail platforms.  Many moons ago I used Microsoft’s online office tools for my business.  The product flopped, and I went to Google Apps.  I very much enjoyed using the Google product since then.  I don’t mind paying for Google Apps, I think Gmail is a fantastic product.  The spam filtering, certainly, and threaded messaging are just too good to leave.  The domain level integration, document storage, search and sharing, and ease of use are just better than anything else out there. Plus, it supports two-factor authentication.

For whatever reason, Windows Phone 8 is horrible running Google Apps. Email synchronization is awful.  Google Talk barely works at all. Notifications don’t work. None of the other applications are available.  Google has decided that they are going to beat Microsoft on at least this one thing, and this is a pretty successful way to do it.  They have not wanted to make their tools available on the windows platform and I can’t blame them.  Microsoft on the other hand has made most of the tools available on Android.  Thus if I want to use a Microsoft tool, it is probably available on the Android platform.  The reverse is not true.

Conclusion

So there you have it.  The problem is not the app store.  The problem is not the lack of the phone’s popularity.  The problem is that in making the phone easy to use and easy to develop for, they have closed the door to too much innovation and integration. It’s really easy to do the things we wanted to do yesterday, and really hard to do the things we need to do tomorrow.

I still think the Windows Phone is an excellent consumer device.  I would recommend it to anybody.  Not too many people worry about A/MIME support, or integration with their business’s Google Apps.  The application selection, games, and Microsoft integration is really very good.  The phone draws stares everywhere I use it.  But it just isn’t right for me, and I can’t make it right for me.  Therein lies the rub.

I’ll still develop for the windows phone.  I’ll still use it as a standalone device.  It just doesn’t work for me as a primary phone, and I can’t imagine that it does for anyone else with specialized needs.  Microsoft has made their decision, and they’re shooting for the 80%. Unfortunately, the 20% are the folk with loud voices.  That might be the platform’s downfall.

Bill Sempf

Husband. Father. Pentester. Secure software composer. Brewer. Lockpicker. Ninja. Insurrectionist. Lumberjack. All words that have been used to describe me recently. I help people write more secure software.

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