Wednesday, March 20, 2013

How to Hack Samsung Phone Screen Lock


I have discovered another security flaw in Samsung Android phones. It is possible to completely disable the lock screen and get access to any app - even when the phone is "securely" locked with a pattern, PIN, password, or face detection. Unlike another recently released flaw, this doesn't rely quite so heavily on ultra-precise timing.

Of course, if you are unable to download a screen unlocker, this security vulnerability still allows you to dial any phone number and run any app!

HOWTO

  1. From the lock screen, hit the emergency call button.
  2. Dial a non-existent emergency services number - e.g. 0.
  3. Press the green dial icon.
  4. Dismiss the error message.
  5. Press the phone's back button.
  6. The app's screen will be briefly displayed.
  7. This is just about long enough to interact with the app.
  8. Using this, you can run and interact with any app / widget / settings menu.
  9. You can also use this to launch the dialler.
  10. From there, you can dial any phone number (one digit at a time) and place a phone call.
  11. With Google Play, you can search for apps using the voice interface.
  12. You can download apps from the app store which will disable the screen lock.

Impact

This does not occur on stock Android from Google. This flaw only seems to be present on Samsung's version of Android. I have only tested it on a Galaxy Note II running 4.1.2 - I believe it should work on Samsung Galaxy SIII. It may work on other devices from Samsung.
My test phone was running 4.1.2 with the Touchwiz launcher from Samsung.

Defending Against This Attack

Until Samsung release a patch, the only way this can be defended against is by completely removing the Samsung firmware and replacing it with a 3rd party ROM.
This ROM for the Galaxy S III claims to have fixed the problem.
I'm sure there will be ROMs for other Galaxy devices in due course.

Responsible Disclosure

I reported this flaw to Samsung in late February. They are working on a patch which they assure me will be released shortly.
I have delayed public disclosure of this vulnerability. I also asked if they wanted me to delay publication until a patch was ready - however they declined this offer.
If you discover a security issue with Samsung's mobile products, I strongly encourage you to email m.security AT samsung.com
They will provide their PGP public key if you wish to ensure your communications with them are secure.

Thanks

My thanks to Thang Chien of Vietnam, who first demonstrated a variant of this flaw in January.
Thanks also to David RogersMarc RogersAlec Muffett, andGlyn Wintle for their wisdom and advice around the subject of responsible disclosure. Any faults with this disclosure are mine and mine alone.

2 comments:

  1. Anonymous9:21 PM

    I selected voice command to unlock the screenlock of my Samsung Galaxy S3. I tried voice command to open the phone's camera and is working perfectly fine. When I lock my screen to try the voice command to unlock it, it is prompting that it failed to recognize my voice.

    I tried this post's advice here but it is saying that there is no network selected and I can't even make an emergency call. Also, my phone doesn't flash that home screen for a split seconds.

    I have been splitting my hairs scouring the Internet how to unlock my phone.

    ReplyDelete