1. Android Malware in Practice
Part I

2. Android Filesystem Layout
~ $ adb shell mount
rootfs / rootfs ro,relatime 0 0
tmpfs /dev tmpfs rw,nosuid,relatime,mode=
devpts /dev/pts devpts rw,relatime,mode=
proc /proc proc rw,relatime 0 0
sysfs /sys sysfs rw,relatime 0 0
none /acct cgroup rw,relatime,cpuacct 0 0
tmpfs /mnt/asec tmpfs rw,relatime,mode=755,gid=
tmpfs /mnt/obb tmpfs rw,relatime,mode=755,gid=
none /dev/cpuctl cgroup rw,relatime,cpu 0 0
/dev/block/mmcblk0p9 /system ext4 ro,noatime,barrier=1,data=ordered 0 0
/dev/block/mmcblk0p12 /data ext4 rw,nosuid,nodev,noatime,barrier=1,journal_async_commit,
data=ordered,noauto_da_alloc,discard 0 0
/dev/block/mmcblk0p8 /cache ext4 rw,nosuid,nodev,noatime,barrier=1,journal_async_commit,
data=ordered 0 0
/dev/block/mmcblk0p3 /efs ext4 rw,nosuid,nodev,noatime,barrier=1,journal_async_commit,
/sys/kernel/debug /sys/kernel/debug debugfs rw,relatime 0 0
/dev/fuse /mnt/sdcard fuse rw,nosuid,nodev,relatime,user_id=1023,group_id=1023,....
/dev/block/vold/179:17 /mnt/extSdCard vfat rw,dirsync,nosuid,nodev,noexec,noatime,nodiratime,
uid=1000,gid=1023,...

3. Android Filesystem Layout
The mounts of interest
/ - root of the filesystem hierarchy
/system - the ROM that holds all system binaries
/data - RW location for user applications
/cache - transient data space for user applications
/efs - phone specific information like IMEI number
/mnt/sdcard - fat32 filesystem with no inbuilt security

4. Application locations
System applications
/system/app/<AppName>.apk
User applications
/data/app/<AppName>.apk (preloaded)
/data/app/<AppPkgName>-1.apk (downloaded)
/mnt/secure/asec/<AppPkgName>-1.apk (sdcard)

5. App Signing
All apps are signed with a key to provide android with the ability to distinguish distributors of software
Possible to group applications in the same security context when two applications are signed with same key giving identical digital signature

6. Android Debug Bridge
Android Debug Bridge allows the developer access to the Android device connected via usb or IP
Once connected to a device, ADB provides developers an interface to interact with a rich suite of tools to manage the device

7. ADB Push / Pull
Using ADB we are able to transfer files from/to the device
Pull test.txt off the device and place in pwd
adb pull /mnt/sdcard/test.txt [local location]
Push local test.txt to sdcard on the device
adb push ./test.txt /mnt/sdcard

8. Android Manual Install
Manually install application
adb push com.myapp.hello.apk /data/app/
(Permissions need to be changed to 0644)
adb install com.myapp.hello.apk
Manually uninstall application
adb uninstall com.myapp.hello

9. Package Manager
pm is a tool that is provided to manage and provide details about applications and permissions.
List all applications
pm list packages
Find location of an application
pm path com.myapp.helloworld
List available permissions
pm list permissions -f

10. Activity Manager: Sending Intents
The activity manager provides the mechanism to start an instance of a graphic application
using adb we are able to start applications via
am start -a android.intent.action.CALL -d tel:

11. Service Manager
The service manager can also be invoked via command line to send messages
service call isms 5 s16 "+??????????" i32 0 i32 0 s16 "SMS TEXT HERE"

12. Android Startup

13. init (1)
Responsible for creating mounts and file permissions associated with mount
Reads initrc file which contains these directories, mounts and file permissions
Responsible for further starting other processes/daemons

14. daemons (2)
Native linux daemons such as the following are started by init
netd (manages network connections)
vold (manages volumes such as sdcard)
usbd (manages USB connections)
debuggerd (debug processes - coredump)
rild (manages communication with the radio)
zygote

15. zygote (3)
init launches zygote which loads classes and listen for requests to spawn new applications through an instance of a dalvik virtual machine
Utilises copy-on-write memory references when forking its process to reduce memory footprint

16. Runtime/Service Manager (4a/b)
init starts android runtime process which initialises the Service Manager
Service Manager is the context manager for binder that is responsible for service registration and lookups
Android runtime then sends a start signal for zygote to create an instance of System Service (Android Services)

17. dalvik (5)
Zygote has received a signal to instantiate a dalvik virtual machine instance for the Android System Server

18. System Server (6)
Zygote forks itself with appropriate permissions and starts the System Server instance
Its role is to bootstrap all the android services required by the android framework which provide services to applications

19. Native System Services (7)
Native System Services are services that integrate with the operating system to provide low latency and high availability services such as the audio and surface flinger
Audio Slinger provides audio management and multiplexing while Surface Flinger is the composition framework to display graphics

20. Native System Services (7) continued
Native System Services register themselves with Service Manager allowing them to be available through IPC for other applications or processes

21. Android System Services (8)
Android System Services provide high level framework services for applications
These services like Native System Services register themselves with Service Manager allowing for IPC communication from Android applications and other services

22. Android Development
Android provides users familiar with Java an easy route to build mobile applications. Google provides a SDK and NDK which enable the developer to call upon rich libraries and tools.

23. Software Development Kit (SDK)
The android Software development kit provides libraries and tools to develop standard java applications. Some of the tools allow for automatic installation of various android platforms and their associated libraries - eg. Ice Cream Sandwich.
Included in the ADT bundle is the SDK and an eclipse environment configured and setup for building/developing Android applications.

24. Native Development Kit (NDK)
Android allows for native libraries to be used with the android environment.
These libraries are C/C++ based and give developers greater performance gains for intensive hardware operations.

25. Repackaging howto: reverse engineering an application –
open the apk archive to access smali-
$ apktool d com.hello out OR
run dedexer (convert apk to jar archive)
run a java decompiler or use jdgui

26. Insert the payload Still have key signing issue
But users can be unaware of the dangers

27. Reverse Engineering Links

28. Malicious App 1: SMS
DEMO

29. Malicious App 2: Photo/Sdcard
DEMO

30. Malicious App 3: Keyswift
DEMO
Reference:

31. Notes
These attacks were aimed at Samsung devices which have been known to implement their own sdk libraries for android.
These have not been tested as vigorously as would be liked and have been proven to provide further vulnerabilities.

32. Permissions Concerns android.permission.SEND_SMS / RECEIVE_SMS
android.permission.SYSTEM_ALERT_WINDOW
android.permission.READ_CONTACTS / WRITE_CONTACTS android.
permission.READ_CALENDAR / WRITE_CALENDAR
android.permission.CALL_PHONE
android.permission.READ_LOGS
android.permission.ACCESS_FINE_LOCATION
android.permission.GET_TASKS
android.permission.RECEIVE_BOOT_COMPLETED
android.permission.CHANGE_WIFI_STATE
com.android.browser.permission.READ_HISTORY_BOOKMARKS /
WRITE_HISTORY_BOOKMARKS
Sourced from Google IO 2012 and marakana.com

33. References Android: http://developer.android.com/index.html
Google IO:
Marakana:
Genome project

34. Questions?