...stuff I do and things I like...

Tuesday, November 27 2018

Android InfoPanel aka Home InfoPanel Redux

In 2007/2008 I built a InfoPanel for my apartment to show me news, the weather and other interesting and fun things. The original InfoPanel was built using a VIA x86 micro ITX board and a 17" touchscreen all fitted in a self made wooden case. The InfoPanel survived until 2012 when I moved to the U.S. It was too old and too big to bring so I dismantled it.

I always missed it and thought about brining it back. For a brief time I used an old Samsung Galaxy Tab 10" but the device was just not right. Starting with a proprietary Samsung USB connecter that didn't allow for nice looking cabling, the device was black and silver so it didn't look too nice on the wall and finally the device was just old and slow. Long story short it only stayed on the wall for a couple of weeks and I just ran a full screened web browser.

The new InfoPanel

Hardware: Android 10" tablet in a white case with a USB connector on the long side.
Software: custom Android app that hides the Android navigation elements and status bar.

    I chose a Yellyouth Android 10" tablet, those tablets are damn cheap (just under $100) but also kinda tricky. The good parts: 4GB ram and a fast processor. The tricky parts: The product description says the resolution is 2560x1600 my device reports that resolution in the system infos but the screen reports 1216x800 pixels. The device does not contain any sensors such as a light or proximity sensor (you will see why that matters later). The GSM modem does not support T-Mobile/AT&T SIM cards, I thought this was a joke but I tried a Google Fi data-only SIM (T-mobile) and the device couldn't connect to any network (this is fine since I only use WiFi).

    I wrote a small Android application that basically shows a full screen webview. I've added a back and reload button to allow returning to the main page from links I clicked. The application hides all system UI (navigation and status bar). The user can swipe from bottom to top or top to bottom to reveal the back and reload buttons. The buttons auto hide after a short timeout. A really basic Android app!

    I wanted to conserve power and turn of the screen when I'm not using the InfoPanel. Luckily saving power is a default function of Android (you can just set the inactivity timeout after which the screen will be dimmed and eventually turned off).

    The catch: how do I turn the screen back on (without pressing the power button - since that is not super practical!)?

    • Motion detection using the camera: several projects exist and I've got it integrated but was not able to get it working while the screen was off (I also didn't want so spent a lot of time on this part)
    • Motion detection using the light sensor: I implemented this using a Nexus 7 tablet, a background service monitors the sensor and wakes up the device once it detects a significant change in brightness - sadly the Yellyouth device does not have a light sensor.
    • Audio activation: the idea is to monitor the ambient noise and wake up the tablet when there is a loud noise (finger snap or clap), I implemented this using a background task that records audio and discards the content and only monitors the amplitude (there is a built-in method in the SDK to query the amplitude!)

All in all a fun weekend/evening project of a few hours.

Saturday, June 23 2018

USB Mass Storage with Network Access

I finally had time and a use case to build this idea that I had some years ago. The idea is pretty simple. I wanted to have a USB flash drive that is network connected to allow adding files remotely while the drive is connected to a device such as a SmartTV. Basically this would allow any device that is capable of reading files from USB flash drive to have access to data stored on the network.

For the first version of this project I used a Raspberry Pi Zero W. The PiZW comes with a USB OTG port, Wifi, and runs of a mini SDcard. So we have USB client (to emulate a USB mass storage device), Wifi (for network connectivity), and the SDcard for the actual storage.

The current implementation basically is a small linux system that takes up a tiny part of the SD card, the rest of the SD card is used to emulate the USB flash drive. The linux system automatically connects to my WiFi network. You can transfer files to the SD card via SCP. The trick of the system is that you can soft plug and un-plug the USB drive via SSH. This means you simply run a command to enable or disable the mass storage emulation, this will look like an plug or un-plug event to the device the PiZW is connected to.

I used Buildroot for this project, I created a repository that allows you to build this entire device for yourself. My Buildroot repository contains all the scripts and settings to enable USB OTG and device switching. The repository can be found here: github.com/crmulliner/usbnetstore.

After finishing this project I found the SanDisk Wireless Stick basically a USB flash drive with built-in Wifi. Sadly it turns out you can't switch between WiFi and USB using their app (it comes with a mobile app). This means as long as it detects a USB connection it will not allow Wifi Access. Therefore, the SanDisk device is not sufficient for my use case.

My SanDisk Wireless Stick also stopped charging after a week or so (and thus became a brick). I disassembled it and found that the storage is provided by a SD card. The device is actually made by AirStash and sadly does NOT run Linux and therefore is not easily modifiable.

Below some pictures of this project:

One USB connector for power and one USB connector for the flash drive.

I'm now working on the second version of this project.

Sunday, April 15 2018

Taking a Break from Blogging

It has been a while since I wrote anything on this blog (October 2017 to be specific) and it will be a bit until I start doing blog posts on a regular basis again. This has multiple reasons. First, I'm not doing the mobile security update anymore since I have kinda stopped working in mobile security space. Second, I'm working on super fun things at the moment and therefore don't have time or energy to work on side projects. Some in progress long term projects will be continued. Third, I will likely attend fewer conferences this year since I'm spending time on different aspects of security research.

I will likely blog about random things every now and then.


Friday, January 26 2018

Third Party Android App Stores

I wrote an article for the Parallax about the security of third party Android app stores.

Tuesday, October 24 2017

Mobile Security News Update October 2017

    PacSec Nov 1-2, Tokyo, Japan. Grandma's old bag, how outdated libraries spoil Android app security by Marc Schoenefeld. When encryption is not enough: Attacking Wearable - Mobile communication over BLE by Kavya Racharla. The Art of Exploiting Unconventional Use- after-free Bugs in Android Kernel by Di Shen.

    DeepSec Nov 14-17, Vienna, Austria. Normal Permissions In Android: An Audiovisual Deception by Constantinos Patsakis.


Quick conference review: both 44con and ekoparty were great. Ekoparty was especially awesome since I got to check the last continent off my list. Also the size of ekoparty was way beyond what I was expecting. They managed to have a really good conference that is professionally run while stilling maintaining the vibe of a hacker / underground con <3

Two weeks ago there was a post on Medium about two companies that provide a mobile identification service. That service basically can be used to convert your phone's IP address into real information about the owner of the phone (the contract owner). This is done via APIs that are provided by multiple Mobile Network Operators (such as AT&T). The medium article linked to demo pages of those two service providers (payfone and danal inc) that show not only your phone number but also your operator's name, your name and address.

I played with the two demo sites for a bit (while they were still online - offline now). I'm on Google Fi with a number proted from T-Mobile (pre-paid). Payfone only had my phonenumber and old carrier (T-Mobile) while Danal inc showed no data at all. I never provided any data to T-Mobile since it is not required for a pre-paid card. Google has all the data but likely does not share it with 3rd parties.

Overall this is a service that I really don't want to exist. I don't want an abritary company to be able to identify me while visiting their website from my mobile phone. I hope those companies don't just sell their services to anybody. Read the Medium article again: AT&T consumer choice opt-out doesn't affect this!

iOS 11 the tragedy continues: 11.0 had a bunch of flaws that were annyoing. Now 11.0.3 randomly frezzes my phone for minutes. Also I have some issues with voice call audio not working sometimes. Highly disaspointing!

Pictures of the month:


Monday, September 25 2017

Biometrics and Smartphones

since I always rant about how I don't like biometrics in smartphones some people have asked me to formulate what I actually would like to see to happen in this area.

My dislike for biometrics is that you cannot change your password anymore because your password is your finger, eye (iris), or face. That means you basically show you password to everybody. A good example of this is here: Politician's fingerprint 'cloned from photos' by hacker.

The second part of the problem is that many biometric systems can be easily bypassed, some face recognition systems even with a picture shown on a smartphone screen.

My main issue is that biometric systems can be bypassed by forcing the owner of the device to unlock it. This can be done without leaving evidence, a funny example of this issue: 7-Year-Old Boy Uses Sleeping Dad's Finger To Unlock iPhone. Also see this interesting case: Court rules against man who was forced to fingerprint-unlock his phone.

The main argument I always hear is that people who wouldn't set a password (or use just a simple PIN) are using biometrics and therefore are more secure now with the help of biometrics. The kid from the previous story wasn't stopped by biometrics it was just as good as not having a password.

What would have stopped the kid from unlocking his dad's phone? A simple timeout! Basically what I want to see is a timeout for your biometrics. Once you entered your password you can unlock your phone using biometrics, after a specific amount of time you have to re-enter your password and cannot unlock the device using biometrics. With a timeout of say 30 minutes to one hour you can prevent simple attacks while still being able to use the convenience of biometrics. Apple recently introduced the SOS mode that will also disable biometric authentication until you enter your password. I wish this was taken one step further and let you set a timeout.

I personally see biometrics on a smartphone as a pure convenience feature and treat it as a weak security feature. I only use it for ApplePay.

I think it is pretty bad to get people used to biometric authentication, Apple may get it right but other companies wont. Normal users can't determine this easily. Also how much did the additional hardware components cost to implement fingerprint authentication or face recognition. FaceID doesn't use a normal camera so there are definitely additional costs that you as the user have to pay for this convenience feature.

Face recognition in consumer products also gets people to accept this as an normal everyday thing and thus helps the argument for face recognition being used in surveillance.



Tuesday, September 19 2017

Mobile Security News Update September 2017

    ekoparty Sep 27-29, Buenos Aires. Blue Pill for your phone by Oleksandr Bazhaniuk. Unbox Your Phone - Exploring and Breaking Samsung's TrustZone Sandboxes by Daniel Komaromy. Inside Android's SafetyNet Attestation: Attack and Defense by Collin Mulliner. How to cook Cisco: Exploit Development for Cisco IOS by George Nosenko. Bypass Android Hack by Marcelo Romero.

    Virus Bulletin 4-6 Oct, Madrid Span. Last-minute paper: Publishing our malware stats by Jason Woloz (Google) [This is about Android Malware]. Android reverse engineering tools: not the usual suspects by Axelle Apvrille.
Some comments on BlueBorne: I've been involved with Bluetooth security since like forever (not active in the last 10+ years). The early Bluetooth vulnerabilities were mostly logic bugs and issues such as missing authentication. Bluetooth devices could not be set to hidden and would always show up when scanning for devices. Stuff like that. BlueBorne is different as it is a remote exploitable memory corruption vulnerability in Linux, Android, and Windows. This is quite a novelty since we haven't seen a bug that is more ore less the same on two platforms. Even more interesting is that this bug is pre-authentication and gives you kernel privileges (code exec in the kernel).

In theory this set of vulnerabilities can be bad, bad. In practice the issue is much less of an issue. Exploit mitigations and built variances help mitigating the risk. Devices are not always visible therefore the attacker cannot easily find your device and attack it.

Also see: Hackers Could Silently Hack Your Cellphone And Computers Over Bluetooth.

FaceID: I think it is a really horrible idea! Do not put biometric systems in to consumer products ever! I will not buy products with mandatory biometrics so far iOS allows me to turn it off and use a passphrase - thats why I even consider buying iOS devices. I hate this change -- biometrics are bad.


I agree ^^^