Android Malware in Practice Part I. Android Filesystem Layout visitor@UOA283090 ~ $ adb shell mount rootfs / rootfs ro,relatime 0 0 tmpfs /dev tmpfs rw,nosuid,relatime,mode=755.

Android Malwarein PracticePart I

Android Filesystem Layoutvisitor@UOA283090 ~ $ adb shell mountrootfs / rootfs ro,relatime 0 0tmpfs /dev tmpfs rw,nosuid,relatime,mode=755 0 0devpts /dev/pts devpts rw,relatime,mode=600 0 0proc /proc proc rw,relatime 0 0sysfs /sys sysfs rw,relatime 0 0none /acct cgroup rw,relatime,cpuacct 0 0tmpfs /mnt/asec tmpfs rw,relatime,mode=755,gid=1000 0 0tmpfs /mnt/obb tmpfs rw,relatime,mode=755,gid=1000 0 0none /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,data=ordered 0 0/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,...

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

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)

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

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

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

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

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

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: 021021021

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"

Android Startup

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

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

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

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)

dalvik (5)• Zygote has received a signal to instantiate a dalvik virtual

machine instance for the Android System Server

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

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

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

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

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.

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.

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.

Repackaging

howto: reverse engineering an application –

open the apk archive to access smali-$ apktool d com.hello out

ORrun dedexer (convert apk to jar archive)

run a java decompiler or use jdgui

http://java.decompiler.free.fr/?q=jdgui

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

Reverse Engineering Links• http://

a4apphack.com/security/sec-code/extract-androidapk-from-market-and-decompile-it-to-java-source

• http://marakana.com/s/post/1109/decompiling_an_android_app

• http://blog.apkudo.com/2012/10/16/reverse-engineeringandroid-disassembling-hello-world/

Malicious App 1: SMS

DEMO

Malicious App 2: Photo/Sdcard

DEMO

Malicious App 3: Keyswift

DEMO

Reference:http://

www.android-app-development.ie/blog/2013/03/06/inserting-keyloggercode-in-android-swiftkey-using-apktool/

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.

http://randomthoughts.greyhats.it/2013/03/owning-samsung-phones-for-fun-but-with.html

Permissions Concerns

android.permission.SEND_SMS / RECEIVE_SMSandroid.permission.SYSTEM_ALERT_WINDOWandroid.permission.READ_CONTACTS / WRITE_CONTACTS android.permission.READ_CALENDAR / WRITE_CALENDARandroid.permission.CALL_PHONEandroid.permission.READ_LOGSandroid.permission.ACCESS_FINE_LOCATIONandroid.permission.GET_TASKSandroid.permission.RECEIVE_BOOT_COMPLETEDandroid.permission.CHANGE_WIFI_STATEcom.android.browser.permission.READ_HISTORY_BOOKMARKS /WRITE_HISTORY_BOOKMARKS

Sourced from Google IO 2012 and marakana.com

References• Android: http://developer.android.com/index.html • Google IO: https://sites.google.com/site/io/ • Marakana: http://marakana.com/training/android/ • Genome project http://www.malgenomeproject.org/

Questions?