Android 2.2 introduces support for enterprise applications by offering the Android Device Administration API. The Device Administration API provides device administration features at the system level. These APIs allow you to create security-aware applications that are useful in enterprise settings, in which IT professionals require rich control over employee devices. For example, the built-in Android Email application has leveraged the new APIs to improve Exchange support. Through the Email application, Exchange administrators can enforce password policies — including alphanumeric passwords or numeric PINs — across devices. Administrators can also remotely wipe (that is, restore factory defaults on) lost or stolen handsets. Exchange users can sync their email and calendar data.
This document is intended for developers who want to develop enterprise solutions for Android-powered devices. It discusses the various features provided by the Device Administration API to provide stronger security for employee devices that are powered by Android.
Here are examples of the types of applications that might use the Device Administration API:
You use the Device Administration API to write device admin applications that users install on their devices. The device admin application enforces the desired policies. Here's how it works:
If users do not enable the device admin app, it remains on the device, but in an inactive state. Users will not be subject to its policies, and they will conversely not get any of the application's benefits—for example, they may not be able to sync data.
If a user fails to comply with the policies (for example, if a user sets a password that violates the guidelines), it is up to the application to decide how to handle this. However, typically this will result in the user not being able to sync data.
If a device attempts to connect to a server that requires policies not supported in the Device Administration API, the connection will not be allowed. The Device Administration API does not currently allow partial provisioning. In other words, if a device (for example, a legacy device) does not support all of the stated policies, there is no way to allow the device to connect.
If a device contains multiple enabled admin applications, the strictest policy is enforced. There is no way to target a particular admin application.
To uninstall an existing device admin application, users need to first unregister the application as an administrator.
In an enterprise setting, it's often the case that employee devices must adhere to a strict set of policies that govern the use of the device. The Device Administration API supports the policies listed in Table 1. Note that the Device Administration API currently only supports passwords for screen lock:
Table 1. Policies supported by the Device Administration API.
| Policy | Description |
|---|---|
| Password enabled | Requires that devices ask for PIN or passwords. |
| Minimum password length | Set the required number of characters for the password. For example, you can require PIN or passwords to have at least six characters. |
| Alphanumeric password required | Requires that passwords have a combination of letters and numbers. They may include symbolic characters. |
| Maximum failed password attempts | Specifies how many times a user can enter the wrong password before the device wipes its data. The Device Administration API also allows administrators to remotely reset the device to factory defaults. This secures data in case the device is lost or stolen. |
| Maximum inactivity time lock | Sets the length of time since the user last touched the screen or pressed a button before the device locks the screen. When this happens, users need to enter their PIN or passwords again before they can use their devices and access data. The value can be between 1 and 60 minutes. |
In addition to supporting the policies listed in the above table, the Device Administration API lets you do the following:
The examples used in this document are based on the Device Administration API sample, which is included in the SDK samples. For information on downloading and installing the SDK samples, see Getting the Samples. Here is the complete code for the sample.
The sample application offers a demo of device admin features. It presents users with a user interface that lets them enable the device admin application. Once they've enabled the application, they can use the buttons in the user interface to do the following:
Figure 1. Screenshot of the Sample Application
System administrators can use the Device Administration API to write an application that enforces remote/local device security policy enforcement. This section summarizes the steps involved in creating a device administration application.
To use the Device Administration API, the application's manifest must include the following:
DeviceAdminReceiver that includes the following:
BIND_DEVICE_ADMIN permission.ACTION_DEVICE_ADMIN_ENABLED
intent, expressed in the manifest as an intent filter.Here is an excerpt from the Device Administration sample manifest:
<activity android:name=".app.DeviceAdminSample$Controller" android:label="@string/activity_sample_device_admin"> <intent-filter> <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.SAMPLE_CODE" /> </intent-filter> </activity> <receiver android:name=".app.DeviceAdminSample" android:label="@string/sample_device_admin" android:description="@string/sample_device_admin_description" android:permission="android.permission.BIND_DEVICE_ADMIN"> <meta-data android:name="android.app.device_admin" android:resource="@xml/device_admin_sample" /> <intent-filter> <action android:name="android.app.action.DEVICE_ADMIN_ENABLED" /> </intent-filter> </receiver>
Note that:
Activity
subclass called Controller. The syntax
".app.DeviceAdminSample$Controller" indicates that
Controller is an inner class that is nested inside the
DeviceAdminSample class. Note that an Activity does not need to be
an inner class; it just is in this example.ApiDemos/res/values/strings.xml. For more information about resources, see
Application Resources.
android:label="@string/activity_sample_device_admin" refers to the
user-readable label for the activity.android:label="@string/sample_device_admin" refers to the
user-readable label for the permission.android:description="@string/sample_device_admin_description" refers to
the user-readable description of the permission. A descripton is typically longer and more
informative than
a label.android:permission="android.permission.BIND_DEVICE_ADMIN"
is a permission that a DeviceAdminReceiver subclass must
have, to ensure that only the system can interact with the receiver (no application can be granted this permission). This
prevents other applications from abusing your device admin app.android.app.action.DEVICE_ADMIN_ENABLED is the the primary
action that a DeviceAdminReceiver subclass must handle to be
allowed to manage a device. This is set to the receiver when the user enables
the device admin app. Your code typically handles this in
onEnabled(). To be supported, the receiver must also
require the BIND_DEVICE_ADMIN permission so that other applications
cannot abuse it. android:resource="@xml/device_admin_sample"
declares the security policies used in metadata. The metadata provides additional
information specific to the device administrator, as parsed by the DeviceAdminInfo class. Here are the contents of
device_admin_sample.xml:<device-admin xmlns:android="http://schemas.android.com/apk/res/android">
<uses-policies>
<limit-password />
<watch-login />
<reset-password />
<force-lock />
<wipe-data />
</uses-policies>
</device-admin>
In designing your device administration application, you don't need to include all of the policies, just the ones that are relevant for your app.
For more discussion of the manifest file, see the Android Developers Guide.The Device Administration API includes the following classes:
DeviceAdminReceiverDeviceAdminReceiver subclass.DevicePolicyManagerDeviceAdminReceiver that the user
has currently enabled. The DevicePolicyManager manages policies for
one or more DeviceAdminReceiver instancesDeviceAdminInfoThese classes provide the foundation for a fully functional device administration application.
The rest of this section describes how you use the DeviceAdminReceiver and
DevicePolicyManager APIs to write a device admin application.
To create a device admin application, you must subclass
DeviceAdminReceiver. The DeviceAdminReceiver class
consists of a series of callbacks that are triggered when particular events
occur.
In its DeviceAdminReceiver subclass, the sample application
simply displays a Toast notification in response to particular
events. For example:
public class DeviceAdminSample extends DeviceAdminReceiver {
...
@Override
public void onEnabled(Context context, Intent intent) {
showToast(context, "Sample Device Admin: enabled");
}
@Override
public CharSequence onDisableRequested(Context context, Intent intent) {
return "This is an optional message to warn the user about disabling.";
}
@Override
public void onDisabled(Context context, Intent intent) {
showToast(context, "Sample Device Admin: disabled");
}
@Override
public void onPasswordChanged(Context context, Intent intent) {
showToast(context, "Sample Device Admin: pw changed");
}
void showToast(Context context, CharSequence msg) {
Toast.makeText(context, msg, Toast.LENGTH_SHORT).show();
}
...
}
One of the major events a device admin application has to handle is the user enabling the application. The user must explicitly enable the application for the policies to be enforced. If the user chooses not to enable the application it will still be present on the device, but its policies will not be enforced, and the user will not get any of the application's benefits.
The process of enabling the application begins when the user performs an
action that triggers the ACTION_ADD_DEVICE_ADMIN
intent. In the
sample application, this happens when the user clicks the Enable
Admin button.
When the user clicks the Enable Admin button, the display changes to prompt the user to enable the device admin application, as shown in figure 2.
Figure 2. Sample Application: Activating the Application
Below is the code that gets executed when the user clicks the Enable Admin button shown in figure 1.
private OnClickListener mEnableListener = new OnClickListener() {
public void onClick(View v) {
// Launch the activity to have the user enable our admin.
Intent intent = new Intent(DevicePolicyManager.ACTION_ADD_DEVICE_ADMIN);
intent.putExtra(DevicePolicyManager.EXTRA_DEVICE_ADMIN,
mDeviceAdminSample);
intent.putExtra(DevicePolicyManager.EXTRA_ADD_EXPLANATION,
"Additional text explaining why this needs to be added.");
startActivityForResult(intent, RESULT_ENABLE);
}
};
...
// This code checks whether the device admin app was successfully enabled.
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
switch (requestCode) {
case RESULT_ENABLE:
if (resultCode == Activity.RESULT_OK) {
Log.i("DeviceAdminSample", "Administration enabled!");
} else {
Log.i("DeviceAdminSample", "Administration enable FAILED!");
}
return;
}
super.onActivityResult(requestCode, resultCode, data);
}
The line
intent.putExtra(DevicePolicyManager.EXTRA_DEVICE_ADMIN,
mDeviceAdminSample) states that mDeviceAdminSample (which is
a DeviceAdminReceiver component) is the target policy.
This line invokes the user interface shown in figure 2, which guides users through
adding the device administrator to the system (or allows them to reject it).
When the application needs to perform an operation that is contingent on the
device admin application being enabled, it confirms that the application is
active. To do this it uses the DevicePolicyManager method
isAdminActive(). Notice that the DevicePolicyManager
method isAdminActive() takes a DeviceAdminReceiver
component as its argument:
DevicePolicyManager mDPM;
...
boolean active = mDPM.isAdminActive(mDeviceAdminSample);
if (active) {
// Admin app is active, so do some admin stuff
...
} else {
// do something else
}
DevicePolicyManager is a public class for managing policies
enforced on a device. DevicePolicyManager manages policies for one
or more DeviceAdminReceiver instances.
You get a handle to the DevicePolicyManager as follows:
DevicePolicyManager mDPM =
(DevicePolicyManager)getSystemService(Context.DEVICE_POLICY_SERVICE);
This section describes how to use DevicePolicyManager to perform
administrative tasks:
DevicePolicyManager includes APIs for setting and enforcing the
device password policy. In the Device Administration API, the password only applies to
screen lock. This section describes common password-related tasks.
This code displays a user interface prompting the user to set a password:
Intent intent = new Intent(DevicePolicyManager.ACTION_SET_NEW_PASSWORD); startActivity(intent);
The password quality can be one of the following DevicePolicyManager constants:
PASSWORD_QUALITY_ALPHABETICPASSWORD_QUALITY_ALPHANUMERICPASSWORD_QUALITY_NUMERICPASSWORD_QUALITY_SOMETHINGPASSWORD_QUALITY_UNSPECIFIEDFor example, this is how you would set the password policy to require an alphanumeric password:
DevicePolicyManager mDPM; ComponentName mDeviceAdminSample; ... mDPM.setPasswordQuality(mDeviceAdminSample, DevicePolicyManager.PASSWORD_QUALITY_ALPHANUMERIC);
You can specify that a password must be at least the specified minimum length. For example:
DevicePolicyManager mDPM; ComponentName mDeviceAdminSample; int pwLength; ... mDPM.setPasswordMinimumLength(mDeviceAdminSample, pwLength);
You can set the maximum number of allowed failed password attempts before the device is wiped (that is, reset to factory settings). For example:
DevicePolicyManager mDPM; ComponentName mDeviceAdminSample; int maxFailedPw; ... mDPM.setMaximumFailedPasswordsForWipe(mDeviceAdminSample, maxFailedPw);
You can set the maximum period of user inactivity that can occur before the device locks. For example:
DevicePolicyManager mDPM; ComponentName mDeviceAdminSample; ... long timeMs = 1000L*Long.parseLong(mTimeout.getText().toString()); mDPM.setMaximumTimeToLock(mDeviceAdminSample, timeMs);
You can also programmatically tell the device to lock immediately:
DevicePolicyManager mDPM; mDPM.lockNow();
You can use the DevicePolicyManager method
wipeData() to reset the device to factory settings. This is useful
if the device is lost or stolen. Often the decision to wipe the device is the
result of certain conditions being met. For example, you can use
setMaximumFailedPasswordsForWipe() to state that a device should be
wiped after a specific number of failed password attempts.
You wipe data as follows:
DevicePolicyManager mDPM; mDPM.wipeData(0);
The wipeData() method takes as its parameter a bit mask of
additional options. Currently the value must be 0.