Tizen Security

TIZEN Security
Hacking the New Mobile OS

Mark Manning
• Sr. Security Consultant with Intrepidus Group
• Mobile:
– Android
– Windows Phone
– Brew
– iOS
– Blackberry
• BSidesROC, Rochester 2600, Interlock Rochester
1/17/2017 Intrepidus Group - Confidential 2

Jason Ross
• Sr. Security Consultant
with Intrepidus Group
– Android
– Web apps
– Network
• Extra Curricular
– TOOOL.ROC, DC585, BSidesROC
– Security BSides*, Dragon Research Group
1/17/2017 Intrepidus Group - Confidential

What we are going to tell you
What Tizen is &
Where it might be going
The Tizen security model
How to perform Tizen security assessments
Predictions for the future

Tizen (/ˈtaɪzɛn/) is…
• An open source mobile operating system
– Started life as Samsung SLP (then Bada), & Intel MeeGo
– Governed by Linux Foundation
• Organized by a board of directors
– The Tizen Association
• Supported by large companies
– Intel, Samsung, Fujitsu
• Based on W3C standards for its applications
– HTML5 APIs
– Touch Events
– Web Storage
– WARP

Tizen wants to…
• Be the ubiquitous solution for “smart” consumer
devices
• Release a high end device this year
• Grab a 15% market share of smartphones
• Replace Android as the most versatile operating system
• Be installed on:
– Smart TV’s
– Cars
– Smart Phones
– Tablets
– Anything that is designed for high end user experience

Tizen Family Tree

Tizen History
• February 2010
– Nokia and Intel announce MeeGo
– Nokia drops out of MeeGo in favor of Windows Phone
• September 2011
– Intel suspends MeeGo & announces Tizen as its replacement
• January 2012
– Tizen source code and SDK released
• May 2013
– Tizen 2.1 released
• July 2013
– Tizen 2.2 released
• August 2013
– Tizen IVI 3.0 beta released

Vapor Hardware

Quick Comparison
Android iOS
Firefox
OS
Ubuntu Tizen
Web App
Support
None None Yes Yes Yes
Native App
Support
Yes Yes No Yes Yes
Primary
Application
Isolation
Mechanism
Linux UIDs
XNU /
Seatbelt
B2G /
Gecko
D-BUS /
App Armor
SMACK
labels
IDE Eclipse Xcode Good luck!
Ubuntu
SDK
Eclipse
Application
Signing
Model
Developer Distributor Distributor Developer
Distributor &
Developer

Technical Steering Group
• In charge of development and working with
OEMs (and advocacy)
• Consists of Samsung, Intel and now Huawei
• Coordinates development of the operating system

Tizen Association
• Always represented by 12 companies
• Always changing
• Current members:

HTML5 Scores

Tizen Application Stack

Types of Apps
• Web Applications:
– Written in HTML5
– JavaScript makes calls to Privileged APIs
– Supports libraries like jQuery Mobile
– Can be either “Packaged Web Apps” or “Hosted Web Apps”
• Native Applications
– C / C++
– Native APIs unrelated to web app APIs
– Focused on gaming
• Hybrid Applications
– Little bit of both

WebRT
• WebRT is to Tizen what DalvikVM is to Android
• Execution of web applications
• Each application runs its own instance
• Access to device resources via JavaScript API
• Access control of web applications

The Widget Stack

Luckily Webkit is universally secure…

WGT
• Web applications or widgets
• W3C standard way of packaging an HTML5 application
• Zip archive with .wgt extension

Application Signing
• Each application is signed with 2 signatures
– W3C Recommended way of handling widget signing
– As opposed to Android’s one
• Author signature
– The author of the application used to verify who created the app
• Distributer signature
– from the publisher, or app store verifying where the application was
distributed from

Privileged Device APIs
• Public:
– Any developer can access
– Example: Filesystem – access a location on the device
• Partner:
– Only those developers that have been verified and approved can access it.
– Partners are given a special Partner CA to sign their applications
– Example: ApplicationManager – manage application certificates
• Platform
– Reserved to OEMs and Tizen implementers
– System level access to a device
– Example: BluetoothAdapter

config.xml File
• Similar to a manifest
• Declare Features: device capabilities
• Declare Privileges: API access required by the app
• Set policy: lets you set a “content security policy” for the application
– White list the sites it should be connecting to
– Based on W3C’s WARP

config.xml Example

Install Directory == Package Name

Installation Directory Structure
bin
APPID.AppName
res
wgt
shared
data
res
trusted
tmp
tmp

Encryption Support
• Web apps support encryption of Javascript,
HTML, CSS, etc
• Install-time encryption only
• Key configuration is located in /usr/share/secure-storage/config
– Usually points to /csa/.seckey
• Magic(key, wgt) = encryption

SMACK - Introduction
• Linux Kernel Module
• Basis of the Tizen security sandbox model
• “Labels” are the metaphor
– similar to how Android uses UIDs
• Tizen 2.1 has 41,000 SMACK rules
– Tizen 3 is looking to reduce these

Smack - Control Mechanisms
• File control
– Extended attributes (xattrs) give filesystem objects a label
– The label corresponds to a SMACK rule
• IPC traffic
• Network traffic
– A CIPSO header is attached to each network packet
• Processes
– Can read /proc/self/attr/current to discover what SMACK labels they are running under

SMACK - Definitions
• Subject
• Object
• Access
• Label

SMACK - Access Rule Format
<subject-label> <object-label> <access-rule>

SMACK - Access Rule Examples
contacts-service _ arwxt
com.Intrepidus.pwn * arwx-
org.tizen.setting miracast-server rwx--
/opt/usr/apps/3FRIz5CoAw.Test = testApp
/tmp/file.txt = myFile
testApp myFile r

SMACK – Access Request Process

Content Security Framework
• McAfee contributed solution to a problem
first noticed in Android
– How does an app get access to the system to perform effective
scans?
• Provides API for anti-virus vendors
– Low-level hooks into the system to bypass usual application
restrictions

Tizen Push Service
• Functionally similar to
GCM on Android
• Messages limited to text
data of 1024 bytes

ASLR
• “Fully implemented" in the Linux Kernel but some additional
security measures are not currently implemented
Securiy protection Purpose
fstack-protector-all adds canary based buffer overflow
checks on the stack and shuts down if
it's corrupt
D_FORTIFY_SOURCE=2 replaces unbouncd string function calls
with bounded ones. Done where GCC
can determine the buffer size.
fpic, fpie position independent code for libraries
(fpic) and executables (fpie). Protects
against return to libc attacks
NX Bit No Execute bit

Weirdness
• Zypper is on the device
• Install all the things!
• OpenSSH: Running by default
on the device
• Root login is permitted

Attackers we are emulating
• A malicious application
on the device
• A remote attacker that
has hijacked another
application’s backend
• Lost or stolen devices
Props to Katy Levinson/HackerDojo for this image

Attack Vectors
• Malicious application store / third party store
– Helped out by the distributor signing model
• SMishing, phishing to install an application
• “Drive by” content (malicious ad networks)
– Helped by defining WARP access tags or setting the
content-security-policy correctly

Tools
• Tizen SDK – Eclipse IDE
• Web simulator
• Tizen Device Emulator
• SDB

Tools - Tizen SDK IDE
• Eclipse
based
• Comes with the
Tizen device
emulator
• And the web
simulator

Tools - Web Simulator
• Lets you run a
WGT inside of
Google Chrome
• App assessment tool

Tools - Web Simulator Controls
• Allows you to manipulate the web
simulator environment
• Contains functions to simulate
device events
• Incoming calls / messages
• Push messages
• Orientation change
• GeoLocation

Tools - Device Emulator
• Very similar to Android
Emulator
• Create virtual devices and run
them
• Devices are qemu VMs,
– qcow format disk images

Tools - Device Emulator Configuration
• Change skin
• Phone
• General Purpose
• Configure RAM
• Control hardware
acceleration

Tools - SDB
• Smart
Development
Bridge
• AKA:
“It’s not ADB, we swear”

Definitely not ADB…

Using SDB + WRT to install apps

Assessment Methodology
• Static Analysis
• File System Analysis
• Dynamic Analysis
• Network Analysis

Static Analysis
• Improper permission requests
– Overprivileged applications are a greater threat
• Unprotected shared content
– SQLite databases
– Temporary files with 777 access
• Encryption used
– Custom encryption or built-in APIs?
– Static keys saved in the application
• Cross origin access restrictions
– Which domains are restricted

File System Analysis
• Storing information on the SDCARD
• Unrestrictive file permissions
• Temporary files with 777 permissions

Dynamic Analysis
• Sensitive file storage
• Overly permissive content sharing
– Inter-application messaging
– Shared SQLite database
– Sensitive temp files

Network Analysis
• XSS means a privilege leakage
– Similar to an Android permission hijack but with JavaScript
• Cross origin attacks
– Can we evade the network restrictions
• SQLi (client side and server)
– Parameterized queries are not used
• Handling untrusted server input
– Testing both the web server and the web client in this model
• Secure data transport
– SSL used throughout

Network MiTM Setup
• Set up a proxy in the WiFi Settings
• IPTables configuration
• Add CA certificates to the trusted system store

Trusted root certificate store
• Anything in /etc/ssl/certs that’s in PEM format and is named
<8hexChars>.0 is considered a trusted cert
• So…
openssl x509 -in burpCA.der
-inform DER -out burpCA.pem
-outform PEM
sdb push burpCA.pem /tmp/
sdb shell
su
mv /tmp/burpCA.pem /etc/ssl/certs/ffffffff.0

Verification of Certificates
• Use the certificate viewer from
to verify the certificate was
“installed” correctly.

Review
• Applications
– HTML5 / WebRT / Webkit
– Privileged APIs
• SMACK
– Subject / Object / Labels
– 41K rules
• Assessments
– IDE / SDK / Emulator / Simulator
– Network MiTM

Predictions
• A Tizen phone will be released next year &
adoption will be slow
– It will be rooted within the first week
• Smart devices like cars, TV’s, and refrigerators will be pushed by Samsung
• A webkit exploit affecting Tizen will break their security model
– This will cause devastating results to the platform, unlike any other mobile vulnerability
• Tizen will be adopted faster in non-American countries as a low cost, feature rich,
alternative to Android

Questions

Contact
• mark.manning@intrepidusgroup.com
• jason.ross@intrepidusgroup.com
• http://intrepidusgroup.com/insight

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