An Introduction to Android Development and SecurityKun Yangkelwya@gmail.com
Android & Me• I’m a first-year graduate student.• I developed my first Android APP——BloGeo two years ago.• I’ve been an Android user for two years.• Now I’ve just started to learn Android security.
Outline• Introduction to Android – Brief history – Architecture• Android Development – Environment – Programming framework – Building and running process – Case Study• Overview of Android Security Feature• Android Security Lab (by Security Compass)• My Future Study
Brief History• Written by Andy Rubin(founder of Android Inc.)• Acquired by Google in 2005• Android 1.0 released in 2007• Android 4.0 released in 2011• 52.5% of global mobile users
Brief Introduction• First complete, open and free mobile platform• Operating System – Mobile device optimized Linux kernel 2.6• Application framework – Mainly Java-based – Running on Dalvik virtual machine featuring JIT compilation• Key applications – Gmail, Maps, Contacts, Market and etc.
Views• Views are GUI controls(E.g. TextView, EditText, Button)• Activity windows consist of views and viewgroups• Organized as trees to build up GUIs• Operations we can perform on views – Set properties: Use function or define in the XML layout files to load. – Set focus – Set up listener – Set visibility – Draw anything we like• We can use Layout to help place views – E.g. LinearLayout, TableLayout, AbsoluteLayout – Use function or define in the XML layout files
Intents• Intents are used to exchange data between Activities or Applications• Think of Intents as a verb and object; a description of what you want done – E.g. VIEW, CALL, PLAY etc..• Describes what the application wants• Provides late runtime binding
Services• Services run in the background• Don’t interact with the user• Run on the main thread of the process
Content Providers• Content providers store and retrieve data and make it accessible to all applications• It is the only way to share data across packages• The backend is SQLite• They are linked to clients• Data exposed as a unique URI
Resources• Resources are images , strings and etc.• Externalize resources from application code• SDK will generate codes to map a resource to an id, we can use static class R to get resources• Layout xml files are also resources
Manifest File• Control file that tells the system what to do and how the top-level components are related• It’s the “glue” that actually specifies which intents your activities receive• Specifies permissions
Building and Running• Android package format – Bundle a few files into a file(.apk) – Just a zip file – Classes.dex is core file – compiled java classes – Use ‘DX’ tool to convert Java *.class to Dalvik bytecode *.dex
Android Security Overview• Goals – Protect user data – Protect system resources (including the network) – Provide application isolation• Android security features provided – Robust security at the OS level through the Linux kernel – Mandatory application sandbox for all applications – Secure interprocess communication – Application signing – Application-defined and user-granted permissions
Android Security Overview(cont.)• Application Sandbox: Kernel Level – Each Application has a user ID(UID) to run• Interprocess Communication – Binder • A lightweight capability-based remote procedure call mechanism designed for high performance when performing in-process and cross-process calls. – Intents – ContentProviders• Application signing
Android Security Overview(cont.)• Application-defined and user-granted permissions – Camera functions – Location data (GPS) – Bluetooth functions – Telephony functions – SMS/MMS functions – Network
ExploitMe Mobile Android Labs• By Security Compass – information security consulting firm – specializing in secure software development and training• An open source project demonstrating Android mobile hacking• A bank transfer mobile client• Server written in python(http/https)• 8 Labs
Lab 6 - Advanced Encryption• apktool – It is a tool for reengineering 3rd party, closed, binary Android apps. – It can decode resources to nearly original form and rebuild them after making some modifications.
Lab 6 - Advanced Encryption(cont.)• apktool d BasicEncryptionSolution.apk export