Android Forensics

Presented By:

Mohamed Khaled

Thanks to: Ibrahim Mosaad Mohamed Shawky

Agenda• Mobile Forensic Process• Different Mobile Forensic Scenario• Acquisition Guide• Challenges of Android Forensics• How to Circumvent the Pass Code• Types Of Analyses(Logical analysis)• Types Of Analyses(Physical analysis)• Android Partition Layout• Custom Recovery Modifications• How Data are Stored In Android• Example of Useful Data extracted from Android

Image

Mobile Forensic Process

Intake

Identification

Preparation

Isolation

Processing

Verification

Documenting

Presentation

Archiving

• Receive device as evidence.• Receive request for

examination• Identify device specifications & capabilities• Identify Goals of Examination

• Prepare methods and tools to be used• Prepare media and forensic workstation

for examination• Prepare tools to most recent version

• Protect the evidence – Prevent remote data destruction

• Isolate from the Cellular network, bluetooth, and Wi-Fi• Conduct forensic acquisition

– Perform forensic analysis –Scan for malware

• Validate your acquisition –Validate your forensic findings• Keep notes about your findings

and process• Draft and finalize your forensic

reports• Prepare exhibits – Present your

findings• Keep a gold copy of data in a

safe place• Keep data in common formats

for future

Data Acquisition Types

Manual Logical Physical

scenarios

The device might be

found to be turned off

after seizure.

have internal or removable

memory

Locked

/unlocked

Have access via USB

debug mode or not

Acquisition GuideA-(Unlocked)

• Airplane Mode

• SIM ID Cloning

Isolate Device from the Network

• Remove passcode

• Enable USB debugging

• Enable “Stay Awake”

• Disable timed screen lock features

Take the necessary steps

to ensure physical device

access is possible• Acquire supporting media

• SIM card(s)

• Media cards

• Check associated media for device backups

Physical Acquisitions

A1 - Isolate Device from the Network

• Airplane Mode

• Remove the SIM card.

• Place device in a shieldedbag, box, tent, or room.

A 2-Ensure physical device access is possible

• Enable USB debugging

• Enable “Stay Awake” option

• Disable timed screen lock features

A3 - Physical Acquisitions

• Acquire supporting media

• SIM card(s)

• Media cards

• Check associated media for device backups(Connected PC or Network)

Acquisition GuideB-(Locked)

1

Physical access requires

that USB debugging mode

is enabled.

Forensic tools will use custom bootloaders to bypass the passcode if applicable.

2

Acquire supporting media

• SIM cards

• Media card(s)

3

Check associated

computers and media for

device backups

• Computers and media cards

Challenges of Android Forensics

• Access to system partitions is Restricted to The Android OS.

• Techniques for obtaining root privilege differ depending on Android version, device manufacturer and model.

• The OS has Authentication mechanisms that uses passwords, tactile patterns or biometric information

How to Circumvent thePass Code

• The smudge attack

• Flash a New Recovery Partition (Our Solution)

• Know Gmail user name andpassword for the device

• JTAG and Chip-off

Types Of Analyses(Logical analysis)

• It is possible to backup all the present data in a cell phone without rooting

– Using Android Debug Bridge (adbbackup command).• $ adb backup -apk -shared -system -all -f %1.backup

– created a backup file which was later converted to .tar archive• $ java -jar abe.jar unpack %1.backup %1.tar

Physical Analysis (Low level analysis )

• Low level analysis is based on exact, bit to bit, copy of userdata partition.

• After the copy, this partition is stored as a single file.

• which is later used as input for other analysis tools.

• Only a root user can make such a copy, so the phone must have been rooted at first.

What is rooting?

• Process of overcoming limitations imposed by manufacturers on smartphone or tablet owners.

• Gives an owner the ability toreplace and/or alter system applications and settings

• Run applications requiringadministrator-level privileges

• This includes listing active mounted partitions and cloning them

Physical analysis(Recovery Mode)

• Another Way to Do Physical Analysis is by using Recovery Rom

• But first We Are Going to Talk About the Android Partition Layout

Android Partition Layout

• boot loader

• Splash

• Boot

• Recovery

• System

• Userdata or Data

• Cache

• Radio

Android Partition Layout (Cont.)• boot loader: Stores the phone’s boot loader

program, which takes care of :

– Initializing the hardware when the phone boots

– Booting the Android kernel

– Implementing alternative boot modes such as download mode.

• boot: Stores the Android boot image, which consists of :

– Linux kernel(zImage)

– and the root file system ram disk (initrd).

• splash: Stores the first splash screen image seen right after

powering on the device.

Android Partition Layout (Cont.)

• userdata (data): this is the device’s internal storage for– Application data

– User files such as: pictures, videos, audio, downloads.

– This is mounted as /data on a booted system.

• system: Stores the Android system image that is mounted as /system on a device. Contains– the Android framework.

– Libraries.

– system binaries.

– pre-installed applications.

Android Partition Layout (Cont.)

• cache: Used to store various utility files such as :

– recovery logs and update packages downloaded over-the-air. On devices with applications installed on an SD card

– it may also contain the dalvik-cache folder, which stores the Dalvik Virtual Machine (VM) cache.

Physical analysis(Recovery Mode)

• It is an operating designed to

– apply updates

– format the device

– perform other maintenance on the devices.

• The stock recovery mode on most devices is very basic

– Only provides a number of limited functions

– Does not provide root privileges in a shell.

Physical analysis(Recovery Mode)

• Should use extreme caution when installing a custom recovery partition as the process often contains kernel and radio updates

• Could render the device unusable “bricked”.

• Extensive testing must be performed on a lab device first to ensure no issues occur.

• Examiners should understand what is being modified on the device during the installation of a custom recovery firmware.

Custom Recovery RomExamples

• Cyanogenmod Recovery(clockworkmod)

• TeamWin (TWRP)

Custom Recovery Modifications

• We are going to modify in the Cyanogenmodsource code

• The source code is writen in C Programming language.

Custom Recovery ModificationsRemove Security Pattern

• The pattern file is at – /data/system/gesture.key

• Other security pattern are in file – /data/system/password.key

• We will also use the pre defined function”__system”.– Which will enable us to run Linux commands like ls,rm,…etc

– __system("rm /data/system/gesture.key"); //remove the pattern

– __system("rm /data/system/password.key"); // remove any other lock like face or voice or password.

• In order to do physical imaging you have to run command like– dd if = /dev/sda1 of =/media/pc/file.dd

– Where if is the source(the media whci we want to image).

– The of is the destination

• So We have to know:– the name of the driver of the source partition (i.e

/data or /system)

– The name of the destination driver (USB Flash for example)

Custom Recovery ModificationPhysical imaging

How To Know The Name Of The Driver For The Source Partition

• Using the file

– /etc/recovery.fstab

• We will search in the /etc/recovery.fstab till we find the driver name equivalent to the partition we want to image

Who to Know The name Of The Destination Driver (USB Flash for example)

• Vold: The volume manager daemon.

• Automatically Mount Sdcard and USB Flash memory (If connected)– When Device Startup

– OR When Connected

• We are going to search in the Vold till we find USB or SdCard.

How Data are Stored In Android

• Android provides developers with five methods for storing data to a device.

1. Shared preferences

2. Internal storage

3. External storage

4. SQLite

5. Network

How Data are Stored In Android(Shared preferences)

• Allow a developer to store key-value pairs of primitive data types in a lightweight XML format.

– /data/data/<com.android.contacts>/shared_prefs

• Used to set the programs configuartion

How Data are Stored In Android(Internal storage)

• Contain more complicated data structures.

• The files are stored in the application’s /data/data subdirectory.

• Files can only be read by the application.

• Indicate data that may be of interest to a forensic analyst

How Data are Stored In Android(External storage)

• Files stored on the internal device’s storage have strict security and location parameters.

• Files on the various external storage devices have far fewer constraints.

• Emulated SdCard and Actual SdCard

• Examples– Pictures,Videos,…,etc

How Data are Stored In Android(SQLite)

• Databases are used for structured data storage – SQLite is a popular database format appearing in

– many mobile systems

– traditional operating systems.

– /data/data/<packageName>/databases.

• SQLite databases are a rich source of forensic data.

How Data are Stored In Android(Network)

• Very few applications took advantage of the network as a storage option.

• The Android Developer web site provides very few details for those interested in network storage.

• You can use the network (when it is available) to store and retrieve data on your own web-based services.

– Dropbox

– Google Drive

– Onedrive

Example of Useful Data extracted from Android Image

• Android Browser Password– /data/data/com.android.browser/databases/webv

iew.db• .table

• select * from password;

– data/com.android.chrome/app_chrome/Default/Login• Open Login Data file using txt viewer

– /data/misc/wifi/ • Open wpa_supplicant.conf file using txt viewer.

References

• Android Forensics

– by Andrew Hoog

• Android Hacker's Handbook– Joshua J. Drake,Pau Oliva Fora,Zach Lanier,Collin Mulliner,Stephen A. Ridley andGeorg

Wicherski

• Developing Process for Mobile Device Forensics– Det. Cynthia A. Murphy

• Android Forensics, Part 1: How we recovered (supposedly) erased data– https://blog.avast.com/2014/07/09/android-foreniscs-pt-2-how-we-recovered-erased-data/

• http://www.cclgroupltd.com/mobile-device-forensics-data-acquisition-types/

• http://www.cclgroupltd.com/mobile-device-forensics-data-acquisition-types/

• http://forum.xda-developers.com/galaxy-nexus/general/guide-phone-backup-unlock-root-t1420351