Android Lollipop for Enterprise
● Senior Security Researcher - Mobile Security Lab● Senior Security Analyst - Consulthink S.p.A.
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Who are we
● [email protected]● @robpicone
● [email protected]● @robgas
@droidconit #droidconit
Enterprise Mobile Management
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Enterprise Mobile Trends
Gartner Market Statistics Forecast:PCs, Ultramobiles and Mobile Phones Worldwide, 2011-2018, 4Q14 Update
Enterprise Mobile Management
● Secure Environment○ SELinux
● Device Protection○ Smart Lock○ "Kill Switch"
● Device Management○ Device Administration API○ Device Owner
● Security Container○ Managed Profile○ App Restrictions
● Data Encryption
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Lollipop for Enteprise
● Introduced in Android 4.3 to enforce the existing Discretionary Access Control (DAC) for application sandboxing (UID,GID)
● Provides Mandatory Access Control (MAC) over all processes at kernel level
● Allows to define fine-grained security policies● Main security features:
○ Better system service restriction and protection ○ Improved access control to application data and system logs○ Reduce effects of malicious software○ User protection from potential flaws in mobile application
SELinux
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Security-Enhanced Linux in Android
"This new layer provides additional protection against potential security vulnerabilities by reducing exposure of system functionality to applications"
Google Report Android Security 2014 Year in Review
SELinux
● Three core elements:○ Subject: Agent that perform actions on objects (processes or groups of processes
referred as domains)○ Action: The operation to perform○ Object: OS-level resources managed by the kernel (file, socket)
● Processes, Sockets and Files have a label or security context:○ username:role:type:mls_level
■ username is always u■ role is r for domains, object_r for objects■ type refers to the domain or to the object logic type■ mls_level is always s0
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Concepts
SELinux
username:role:type:mls_level○ username is always u○ role is r for domains, object_r for objects○ type refers to the domain or to the object logical type○ mls_level is always s0
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Concepts
SUBJECT
OBJECT
Lollipop EnhancementsSELinux
● SELinux mode:○ Permissive: permission denials are logged but not enforced○ Enforcing: permission denials are both logged and enforced
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Android 4.3
Permissive
Android 4.4
PartialEnforcing
Android 5.x
FullEnforcing
... limited set of crucial domains (installd, netd, vold and zygote)...
...to everything (more than 60 domains)...
Smart Lock
● Disable device lockscreen in "trusted condition"● Based on Trust Agent:
○ "A service that notifies the system about whether it believes the environment of the device to be trusted"
○ Requires signatureOrSystem permission
○ Can be disabled by Device Administrator [KEYGUARD_DISABLE_TRUST_AGENTS]
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Trust Agent
http://nelenkov.blogspot.
it/2014/12/dissecting-lollipops-smart-
lock.html
lollipop/frameworks/base/core/res/AndroidManifest.xml
Smart Lock
● Trust Agent provided by Google Play Services
● Device Unlocked methods:○ Trusted bluetooth connected devices○ Trusted places○ Trusted face○ On Body Detection
● Temporary unlock is disabled:○ After 4 hours of inactivity○ Device Reboot/Shutdown
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Some Details
Device Protection
● "You can set up your device to prevent other people from using it if it's been reset to factory settings without your permission"
● Introduced in Android 5.1● Actually works only on Nexus 6 and Nexus 9● Requires:
○ Screen Lock enabled○ Default Google account
○ "OEM Unlocking" disabled in Settings -> Developer Options
● Needs to wait 72 hours after changing password to reset the device
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"Kill Switch" Factory Reset
Device Protection
● PersistentDataBlockService write on the partition defined by ro.frp.pst:○ The OEM Unlocking setting (bit) ○ Write Block Checksum (SHA-256)
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OEM Unlocking
PersistentDataBlockService
Device Administration API
● Introduced in Android 2.2 Froyo (API 8)
● Allows to enforce security policy on
device
● Enterprise Oriented
● Vendor Customization
○ Samsung KNOX
○ LG Gate
● Used by Device Admin Application
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Intro
Device Administration API
● Must be explicitly enabled in the device security settings
● Cannot be uninstalled if active
● Could be controlled by a remote server (agent)
● Several device admin applications can be enabled on a device (strictest policy among all applications is active)
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Device Admin Application
Device Administration API
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Main FeaturesAPI 8 API 9 API 11 API 14 API 17 API 21 API 22
Enforce Password PolicyWatch User Login Reset PasswordLock and Wipe DeviceSet Max Failed Password For WipeSet Max Time To Lock Device
Wipe SDCard
Force Device Encryption
Disable Camera
Disable Keyguard
Managed ProfileGlobal SettingsNFC Provisioning
Wipe Factory Protection
Device Administration API
● Main Admin Application component
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DeviceAdminReceiver
Required to ensure that only the system can interact with the receiver
Primary ACTION that the receiver must handle
PolicyDeclaration
Device Administration API
● Callback functions triggered on particular ACTION
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DeviceAdminReceiver
Method Action
onEnabled(Context context, Intent intent) ACTION_DEVICE_ADMIN_ENABLED
onDisabled(Context context, Intent intent) ACTION_DEVICE_ADMIN_DISABLED
onDisableRequested(Context context, Intent intent) ACTION_DEVICE_ADMIN_DISABLE_REQUESTED
onPasswordSucceeded(Context context, Intent intent) ACTION_PASSWORD_SUCCEEDED
onPasswordFailed(Context context, Intent intent) ACTION_PASSWORD_FAILED
onPasswordChanged(Context context, Intent intent) ACTION_PASSWORD_CHANGED
Device Administration API
● Public Interface for managing policies on device● Requires Device Administration rights enabled● Main methods:
○ isAdminActive(ComponentName who)
○ setPasswordQuality(ComponentName admin, int quality)
○ resetPassword(String password, int flags)
○ lockNow()
○ wipeData(int flags)
○ setCameraDisabled(ComponentName admin, boolean disabled)
○ setStorageEncryption(ComponentName admin, boolean encrypt)
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DevicePolicyManager
Device Administration API
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Device Admin ActivationImplicit Intent for
the system Settings
Device Administration API
● "Specialized type of device administrator" with the additional ability to:○ Add/Remove User○ Modify Global settings○ Set Application Restrictions○ Wipe Factory Protection
● Typically used for company device● Introduced in Android Lollipop (API 21)● Only one device owner can be active at a time● Cannot be disabled or removed● Requires Device Encryption● Deployed and activated via NFC
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Device Owner
Device Administration API
● Via NFC NDEF Record with MIME Type MIME_TYPE_PROVISIONING_NFC and with properties:
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Device Owner Deploy
REQUIRED
CHECKSUMA String extra holding the SHA-1 checksum of the file at download location specified in EXTRA_PROVISIONING_DEVICE_ADMIN_PACKAGE_DOWNLOAD_LOCATION. If this doesn't match the file at the download location an error will be shown to the user and the user will be asked to factory reset the device.
cat app-debug.apk | openssl dgst -binary -sha1 | openssl base64 | tr '+/' '-_' | tr -d '='
Device Administration API
● Device should not be provisionedSettings.Global.DEVICE_PROVISIONED = 0
● Encrypted phone required
● "If provisioning fails, the device is factory reset"
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Device Owner Activation
Managed Profile
● New security feature for enterprise “managed profile”● Available since Android Lollipop (API 21)● Using managed profile the enterprise could define a controlled domain
on the user's device to run controlled application● The application inside the new managed profile can be configured with
policy to interact or not with other apps on device● Samsung KNOX functionality has been integrated into Android
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Introduction
Managed Profile
● A Technology platform for:○ Business protection, and○ Personal Privacy
● Google and Samsung has designed the new Enterprise API around three major concepts:○ Device and data security
○ Support for IT policies and restrictions
○ Mobile application management
● It has been introduced into Android Lollipop
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KNOX Framework
Managed Profile
● A device administration component○ A broadcast receiver that extends “DeviceAdminReceiver”
● AndroidManifest with a receiver:○ The BIND_DEVICE_ADMIN permission○ Respond, by intent-filetr, to the ACTION_DEVICE_ADMIN_ENABLED intent ○ A declaration of security policies used in metadata
● An intent to start the managed profile provisioning process:○ ACTION_PROVISION_MANAGED_PROFILE action ○ An extra with the application package
● Override onProfileProvisioningComplete callback method to verify all is OK
● Enable the new managed profile
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Have to use...
Managed Profile
● BasicDeviceAdminReceiver component
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Broadcast ReceiverBroadcastReceiver of our
provisioner application
Callback method will be called when the system
send ACTION_DEVICE_ADMIN_ENABLED. The new
profile is installed but not yet enabled
Managed Profile
● AndroidManifest.xml declaration
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AndroidManifestTo avoid abuse by other
applications
Intercepted when the Managed Profile has successfully installed
Policy declaration
Managed Profile
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ActivationIntent to start the setup
(Defined in the DevicePolicyManager.java)
● Start the Managed Profile provisioning
The Application package name as additional
information
Verify there is an activity that resolves intent
(ManagedProvisonActivity)
Start activity by intent
● The new Managed profile has to be enabled
Managed Profile
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Enable the new profile
Enable the managed profile
Set name for new profile
Managed Profile
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Managed profile activated
● New Accounts associated to the new managed profile (Settings->Accounts)
● The admin profile (Work) for the new Managed Profile (Settings->Security->Device administrators)
● The applications into new Managed Profile are badged
Managed Profile
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Enable Application
● Add new application into Managed Profile
Add the application by package name via
DevicePolicyManager
Get info about app
Get reference at packageManager and DevicePolicyManager
Managed Profile
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Hide Application
● During the life of Managed Profile the application could be hidden specyfing the app package name○ Only if the application is already installed
we can hide application
true to hide and false to un-hide
Managed Profile
● Enable and disable Intent forwarding between private account and managed profile
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Cross Intent
Enable with and disable intent
between profiles
Share some content
Managed Profile
● Define Chrome restrictions
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App Restriction
Define restriction
Enable restriction
Managed Profile
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App restrictions
Configure some bookmarks
Disable anonymous navigation
Block www.example.com
Configure search engine
Managed Profile
● Application has to define a file restriction and declare it into Manifest file
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Define App Restrictions
● Defines the restriction item into app_restriction.xml file
Declare external resource for restrictions
restriction element with key and type of value
Managed Profile
● Check current application’s restrictions
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Check app restrictions
get current restrictions
get reference to RestrictionManager
search restriction by key to take the appropriate action
Managed Profile
● Set application restriction via DevicePolicyManager
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Set app restrictions
Builds a bundle with value for
restriction
Apply application restriction with method setApplicationRestrictions
Data Encryption
● Encryption is the process of encoding user data on an Android device using an encrypted key
● New feature on Android 5.0:○ Fast encryption (only used blocks are encrypted on data partition)○ forceencrypt flag to encrypt on first boot (Mandatory encryption at first boot)○ Support for encryption without password○ Hardware-backed storage of encryption key using Trusted Execution Environment
● Android introduced Disk encryption in Android version 3.0 and it has been available in all subsequent versions
● New key derivation function scrypt
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Some info
Data Encryption
● Android disk encryption is based on dm-crypt (also used in Linux)
● Use a randomly 128-bit key with AES in CBC mode○ CBC requires an inizialization vector IV
○ Android uses the encrypted salt-sector initialization vector
(ESSIV) method with the SHA-256 hash algorithm (ESSIV:SHA256)
○ SHA256 is used to derive a key s from disk encryption key K called salt
○ Use the salt as encryption key to encrypt sector number SN of each sector to produce a per-sector IV
○ IV(SN)=AES-s(SN) where s=SHA256(K)
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How works
Data Encryption
● The master key is encrypted with 128-bit AES● In Android 5.0 release, four encryption states:
○ default,PIN,Password,Pattern
● Upon first boot the device creates a randomly generated 128-bit master key and then hashes it with a default password and stored salt (default_password)
● The hash is signed through a TEE, that uses hash to encrypt the master key
● When the user sets the PIN/pass or password on the device, only the 128-bit key is re-encrypted and stored
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How works
Data Encryption
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Securing disk encryption key
When user set PIN/PASSWORD/P
ATTERN another key K1 is choosen to
encrypt disk encryption key K
Thanks! DroidCon ItalyTorino 2015www.mseclab.com