Developing Mobile Device Management for 15 million devices (case study)

8/18/2019 Developing Mobile Device Management for 15 million devices (case study)

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developing mobile device management for 15 million device

whoami

• software architect @ btt ltd

• space technologies research institute

• Ericsson mobility world

• underwater photographer


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why am I giving this talk?

• share our research

• describe undocumented Android

• share experience


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plan of this talk

• what is MDM?

• managing Android:

• using API functions

• rooted

• with vendor support

• optimization


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Mobile Device Management system

• purpose: controlling device(s)

• typical features:

• profile delivery: wifi pass, b/w list, email, vp• policy: password strength, camera disabled

• application control


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in two words:

• restricts

• controls


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“Fatih” project

• ordered by Turkish Ministry of Education

• 15 million devices delivered at 30k public sc

• free wifi Internet to all public schools

• running since mid 2013


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about this project


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“Fatih” project requirements

• deliver and manage 15 million devices

• control applications

• control hardware

• manage by profile, location, group


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design


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MDM application design

• MDM is an app

• protect MDM

• undetectable, unstoppable, unremovable

• prevent rooting

• detect if rooted


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make app unstoppable?!

• device administration permission

• app is unstoppable!

• and unremovable!


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device administration API

• password strength policy

• set new password

• lock, wipe, encrypt, disable camera


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security -> device administrators

• view device administrators

• remove permission


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prevent removing admin permission

• offer carrot on a stick

• wifi settings

• email account

• vpn settings


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if permission removed!

• DeviceAdminReceiver.onDisabled()

• disable accounts

• show warning

• notify system administrator


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prevent removing admin permission

• use custom launcher

• what is “launcher”?


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custom launcher

• an application

• device home screen

• lists and launches other apps• keyword: lists and launches


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use custom launcher to:

• show only allowed apps

• hide settings app

• show your own modified Settings


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developing a launcher

• Intent filter

• full-screen app


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making launcher default

• click home button

• select your launcher

• tick “Use by default for this action” checkbox


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application management

• list apps using PackageManager

• every app is not runnable

• getLaunchIntentForPackage()

• launch apps


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application management

• installing apps

• deleting apps

Intent promptInstall = new Intent(Intent.ACTION_VIEW).setDataAndType(Uri.parse("file:///RestaurantMenu.apk"),

"application/vnd.android.package-archive");

Intent intent = new Intent(Intent.ACTION_DELETE);intent.setData(Uri.parse("package:com.facebook.messenger"));


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remember the carrots

• don’t restrict too much

• give good carrots:

• wifi access. Don't give the password!

• corporate accounts: disable account if MDM gets remo


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hard-core Android


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but how do we REALLY control the device?

• unremovable

• system application

• undetectable

• core application


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what is a system application?

• runs with system UIDUSER PID PPID VSIZE RSS NAMEroot 1 0 888 740 /initroot 2 0 0 0 kthreaddroot 157 1 883620 45152 zygotekeystore 163 1 4712 1048 /system/bin/keyst

radio 871 157 920240 31748 com.android.phonebluetooth 886 157 896776 21828 com.mediatek.bluesystem 901 157 903968 29880 com.btt.mdm

u0_a8 923 157 954192 33456 com.android.launu0_a2 974 157 905620 25408 com.android.conta


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developing a system application

• core application

• use system privileges


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permissions


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obtaining the permissions

• “System” permission

• put app to system ROM

• /system/app/

• “Signature” permission:

• sign the app with platform key


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prevent removing Device admin permission?

• disable settings menu

• compile Settings from sources

• mind vendor-specific features


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how to control hardware?

• disable bluetooth use

• for ALL apps!

• disable external memory card, wifi, …

• for ALL apps!

• no functions to disable camera for ALL apps


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reverse-engineer Android

• android source

• http://source.android.com/source/building.html

• find settings application source

• android-source/packages/apps/Settings/

• find bluetooth control functions

http://source.android.com/source/building.html


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hardware control functions

• camera control

• bluetooth control

SystemProperties.set(SYSTEM_PROP_DISABLE_CAMERA

BluetoothAdapter mBluetoothAdapter =BluetoothAdapter.getDefaultAdapter();

mBluetoothAdapter.disable();


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these functions:

• undocumented

• hidden

• unavailable

• modify kernel-level params


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app is compiled. now what?

• root the device

• manufacturer’s support


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what do we get from manufacturers?

• Android (Samsung, LG, General Mobile, etc)

• MDM API

• Sony Open Devices

• Apple MDM

• built-in


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MDM API

• Hardware control

• Application management

• Install application (silent)

• Remove application (silent)

• Control submenus of Settings


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procedure

• join Enterprise Developer Program

• get you app signed by vendor

• security check


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scaling


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app requirements

• low battery

• low bandwidth

• low latency


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how do you do this?

• minimal number of transactions


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server side

• memory

• CPU

• network bandwidth

• example: 15 million devices sending 1KB ea


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how to reduce?

• few requests

• small packets

• Google spdy protocol

• faster!

• great for poor network!


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optimize network operations

• handle connection exceptions

• random wait period

• use AlarmManager, set PendingIntent

• setInexactRepeating()

• limited retry count


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optimize network operations

• check the connectivity status

• listen to network connection changes

ConnectivityManager cm =(ConnectivityManager)context.getSystemService(Context.CONNECTIVIT

NetworkInfo activeNetwork = cm.getActiveNetworkInfo();


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sending commands to device

• send push notification

• device connects over HTTPS

• verify SSL certificate


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server optimization


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microservices

• separate service for each function:

• send message

• send ‘like’

• upload image

• get messages


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microservice workflow

• parse and validate message

• authenticate user

• no business logic


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background services

• sending push notifications

• sending emails

• resizing images

• processing video


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database optimization

• stored procedures

• speed

• security

• business logic


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debugging (shared) production server

• identify single request out of millions of req

• log all requests

• turn on when needed

• for a single microservice

• turn off when done


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testing is important!

• what happens if 1% of 100 customers compl

• what happens if 1% of 15mln customers com

• is bug-free software possible?

• well-tested software is


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conclusion

• android administration

• scaling

• optimization

• don't over-engineer!

• release the app


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questions?http://google.com/+RimKhazhin

http://google.com/+RimKhazhin

Developing Mobile Device Management for 15 million devices (case study)

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