android_frameworks_base/docs/html/guide/topics/security/permissions.jd

page.title=System Permissions
page.tags=permissions
@jd:body

<div id="qv-wrapper">
<div id="qv">

<h2>In this document</h2>
<ol>
<li><a href="#arch">Security Architecture</a></li>
<li><a href="#signing">Application Signing</a></li>
<li><a href="#userid">User IDs and File Access</a></li>
<li><a href="#permissions">Using Permissions</a></li>
<li><a href="#normal-dangerous">Normal and Dangerous Permissions</a>
  <ol>
    <li><a href="#perm-groups">Permission Groups</a></li>
  </ol>
</li>
<li><a href="#defining">Defining and Enforcing Permissions</a>
	<ol>
	<li><a href="#manifest">...in AndroidManifest.xml</a></li>
	<li><a href="#broadcasts">...when Sending Broadcasts</a></li>
	<li><a href="#enforcement">Other Permission Enforcement</a></li>
	</ol></li>
<li><a href="#uri">URI Permissions</a></li>
</ol>

  <h2>Key classes</h2>
  <ol>
    <li>{@link android.Manifest.permission}</li>
    <li>{@link android.Manifest.permission_group}</li>
  </ol>

  <h2>See Also</h2>
  <ol>
    <li><a href="{@docRoot}training/permissions/index.html">Working with System
        Permissions</a></li>
  </ol>

<!--
  <h2>See also</h2>
  <ol>
    <li></li>
  </ol>
-->
</div>
</div>

<a class="notice-designers"
    href="https://www.google.com/design/spec/patterns/permissions.html">
  <div>
    <h3>Design Patterns</h3>
    <p>Permissions</p>
  </div>
</a>

<!-- video box -->
<a class="notice-developers-video"
    href="https://www.youtube.com/watch?v=f17qe9vZ8RM">
<div>
    <h3>Video</h3>
    <p>Google I/O 2015—Android M Permissions: Best Practices for
      Developers</p>
</div>
</a>

<p>Android is a privilege-separated operating system, in which each
application runs with a distinct system identity (Linux user ID and group
ID).  Parts of the system are also separated into distinct identities.
Linux thereby isolates applications from each other and from the system.</p>

<p>Additional finer-grained security features are provided through a
"permission" mechanism that enforces restrictions on the specific operations
that a particular process can perform, and per-URI permissions for granting
ad hoc access to specific pieces of data.</p>

<p>This document describes how application developers can use the
security features provided by Android.  A more general <a
href="http://source.android.com/tech/security/index.html"
class="external-link">Android Security
Overview</a> is provided in the Android Open Source Project.</p>


<a name="arch"></a>
<h2>Security Architecture</h2>

<p>A central design point of the Android security architecture is that no
application, by default, has permission to perform any operations that would
adversely impact other applications, the operating system, or the user.  This
includes reading or writing the user's private data (such as contacts or
emails), reading or writing another application's files, performing
network access, keeping the device awake, and so on.</p>

<p>Because each Android application operates in a process sandbox, applications
must explicitly share resources and data. They do this by declaring the
<em>permissions</em> they need for additional capabilities not provided by
the basic sandbox. Applications statically declare the permissions they
require, and the Android system prompts the user for consent.</p>

<p>The application sandbox does not depend on the technology used to build
an application. In particular the Dalvik VM is not a security boundary, and
any app can run native code (see <a href="{@docRoot}tools/sdk/ndk/index.html">the Android
NDK</a>). All types of applications &mdash; Java, native, and hybrid &mdash;
are sandboxed in the same way and have the same degree of security from each
other.</p>


<a name="signing"></a>
<h2>Application Signing</h2>

<p>All APKs ({@code .apk} files) must be signed with a certificate
whose private key is held by their developer.  This certificate identifies
the author of the application.  The certificate does <em>not</em> need to be
signed by a certificate authority; it is perfectly allowable, and typical,
for Android applications to use self-signed certificates. The purpose of
certificates in Android is to distinguish application authors. This allows
the system to grant or deny applications access to <a
href="{@docRoot}guide/topics/manifest/permission-element.html#plevel">signature-level
permissions</a> and to grant or deny an application's <a
href="{@docRoot}guide/topics/manifest/manifest-element.html#uid">request to be given
the same Linux identity</a> as another application.</p>

<a name="userid"></a>
<h2>User IDs and File Access</h2>

<p>At install time, Android gives each package a distinct Linux user ID. The
identity remains constant for the duration of the package's life on that
device. On a different device, the same package may have a different UID;
what matters is that each package has a distinct UID on a given device.</p>

<p>Because security enforcement happens at the
process level, the code of any two packages cannot normally
run in the same process, since they need to run as different Linux users.
You can use the {@link android.R.attr#sharedUserId} attribute in the
<code>AndroidManifest.xml</code>'s
{@link android.R.styleable#AndroidManifest manifest} tag of each package to
have them assigned the same user ID.  By doing this, for purposes of security
the two packages are then treated as being the same application, with the same
user ID and file permissions.  Note that in order to retain security, only two applications
signed with the same signature (and requesting the same sharedUserId) will
be given the same user ID.</p>

<p>Any data stored by an application will be assigned that application's user
ID, and not normally accessible to other packages.  When creating a new file
with {@link android.content.Context#getSharedPreferences},
{@link android.content.Context#openFileOutput}, or
{@link android.content.Context#openOrCreateDatabase},
you can use the
{@link android.content.Context#MODE_WORLD_READABLE} and/or
{@link android.content.Context#MODE_WORLD_WRITEABLE} flags to allow any other
package to read/write the file.  When setting these flags, the file is still
owned by your application, but its global read and/or write permissions have
been set appropriately so any other application can see it.</p>


<h2 id="permissions">Using Permissions</h2>

<p>A basic Android application has no permissions associated with it by default,
meaning it cannot do anything that would adversely impact the user experience
or any data on the device.  To make use of protected features of the device,
you must include one or more
<a href="{@docRoot}guide/topics/manifest/uses-permission-element.html"
    ><code>&lt;uses-permission&gt;</code></a>
tags in your <a href="{@docRoot}guide/topics/manifest/manifest-intro.html">app
manifest</a>.</p>

<p>For example, an application that needs to monitor incoming SMS messages would
specify:</p>

<pre>&lt;manifest xmlns:android=&quot;http://schemas.android.com/apk/res/android&quot;
    package=&quot;com.android.app.myapp&quot; &gt;
    &lt;uses-permission android:name=&quot;android.permission.RECEIVE_SMS&quot; /&gt;
    ...
&lt;/manifest&gt;</pre>

<div class="sidebox-wrapper">
<div class="sidebox">
  <h3>Permission Levels</h3>
  <p>For more information about the different protection levels for
    permissions, see <a href="#normal-dangerous">Normal and Dangerous
    Permissions</a>.</p>
</div>
</div>

<p>
  If your app lists <em>normal</em> permissions in its manifest (that is,
  permissions that don't pose much risk to the user's privacy or the device's
  operation), the system automatically grants those permissions.
  If your app lists <em>dangerous</em> permissions in its manifest (that is,
  permissions that could potentially affect the user's privacy or the device's
  normal operation), the system asks the user to explicitly grant those
  permissions. The way Android makes the requests depends on the system
  version, and the system version targeted by your app:
</p>

<ul>
  <li>If the device is running Android 6.0 (API level 23) or higher,
  <em>and</em> the app's <a
  href="{@docRoot}guide/topics/manifest/uses-sdk-element.html#target"
  ><code>targetSdkVersion</code></a>
  is 23 or higher, the app requests permissions from the user at run-time.
  The user can revoke the permissions at any time, so the app needs to
  check whether it has the permissions every time it runs.
  For more information about requesting permissions in your app, see the
  <a href="{@docRoot}training/permissions/index.html">Working with System
  Permissions</a> training guide.
  </li>

  <li>If the device is running Android 5.1 (API level 22) or lower, <em>or</em>
  the app's <a
  href="{@docRoot}guide/topics/manifest/uses-sdk-element.html#target"
  ><code>targetSdkVersion</code></a>
  is 22 or lower, the system asks the user to grant the permissions when the
  user installs the app. If you add a new permission to an updated version of
  the app, the system asks the user to grant that permission when the user
  updates the app. Once the user installs the app, the only way they can
  revoke the permission is by uninstalling the app.
  </li>
</ul>

<p>Often times a permission failure will result in a {@link
java.lang.SecurityException} being thrown back to the application. However,
this is not guaranteed to occur everywhere. For example, the {@link
android.content.Context#sendBroadcast} method checks permissions as data is
being delivered to each receiver, after the method call has returned, so you
will not receive an exception if there are permission failures. In almost all
cases, however, a permission failure will be printed to the system log.</p>

<p>The permissions provided by the Android system can be found at {@link
android.Manifest.permission}. Any application may also define and enforce its
own permissions, so this is not a comprehensive list of all possible
permissions.</p>

<p>A particular permission may be enforced at a number of places during your
program's operation:</p>

<ul>
<li>At the time of a call into the system, to prevent an application from
executing certain functions.</li>
<li>When starting an activity, to prevent applications from launching
activities of other applications.</li>
<li>Both sending and receiving broadcasts, to control who can receive
your broadcast or who can send a broadcast to you.</li>
<li>When accessing and operating on a content provider.</li>
<li>Binding to or starting a service.</li>
</ul>

<h3 id="auto-adjustments">Automatic permission adjustments</h3>

<p> Over time,
new restrictions may be added to the platform such that, in order
to use certain APIs, your app must request a permission that it previously did not need.
Because existing apps assume access to those APIs is freely available,
Android may apply the new permission request to the app's manifest to avoid
breaking the app on the new platform version.
Android makes the decision as to whether an app might need the permission based on
the value provided for the <a
href="{@docRoot}guide/topics/manifest/uses-sdk-element.html#target">{@code targetSdkVersion}</a>
attribute. If the value is lower than the version in which the permission was added, then
Android adds the permission.</p>
<p>For example, the {@link android.Manifest.permission#WRITE_EXTERNAL_STORAGE} permission was
added in API level 4 to restrict access to the shared storage space. If your <a
href="{@docRoot}guide/topics/manifest/uses-sdk-element.html#target">{@code targetSdkVersion}</a>
is 3 or lower, this permission is added to your app on newer versions of Android.</p>

<p class="caution">
  <strong>Caution:</strong> If a permission is automatically added to your app,
  your app listing on Google Play lists these additional permissions even
  though your app might not actually require them.
</p>

<p>To avoid this and remove the default permissions you don't need, always update your <a
href="{@docRoot}guide/topics/manifest/uses-sdk-element.html#target">{@code targetSdkVersion}</a>
to be as high as possible. You can see which permissions were added with each release in the
{@link android.os.Build.VERSION_CODES} documentation.</p>
</div>

<h2 id="normal-dangerous">Normal and Dangerous Permissions</h2>

<p>
  System permissions are divided into several protection levels. The two most
  important protection levels to know about are <em>normal</em> and
  <em>dangerous</em> permissions:
</p>

<ul>
  <li>
    <em>Normal</em> permissions cover areas where your app needs to access data
    or resources outside the app's sandbox, but where there's very little risk
    to the user's privacy or the operation of other apps. For example,
    permission to set the time zone is a normal permission. If an app
    declares that it needs a normal permission, the system automatically grants
    the permission to the app. For a full listing of the current normal
    permissions, see <a href="normal-permissions.html">Normal permissions</a>.
  </li>

  <li>
    <em>Dangerous</em> permissions cover areas where the app wants data or
    resources that involve the user's private information, or could potentially
    affect the user's stored data or the operation of other apps. For example,
    the ability to read the user's contacts is a dangerous permission. If an
    app declares that it needs a dangerous permission, the user has to
    explicitly grant the permission to the app.
  </li>
</ul>

<div class="sidebox-wrapper">
<div class="sidebox">
  <h3 id="special_permissions">Special Permissions</h3>
  <p>
    There are a couple of permissions that don't behave like normal and
    dangerous permissions. {@link android.Manifest.permission#SYSTEM_ALERT_WINDOW
    SYSTEM_ALERT_WINDOW} and {@link android.Manifest.permission#WRITE_SETTINGS
    WRITE_SETTINGS} are particularly sensitive, so most apps should not use
    them. If an app needs one of these permissions, it must declare the
    permission in the manifest, <em>and</em> send an intent requesting the
    user's authorization. The system responds to the intent by showing a
    detailed management screen to the user.
  </p>

  <p>
    For details on how to request these permissions, see the {@link
    android.Manifest.permission#SYSTEM_ALERT_WINDOW SYSTEM_ALERT_WINDOW} and
    {@link android.Manifest.permission#WRITE_SETTINGS WRITE_SETTINGS} reference
    entries.
  </p>
</div>
</div>

<h3 id="perm-groups">Permission groups</h3>

<p>
  All dangerous Android system permissions belong to permission groups.
  If the device is running Android 6.0 (API level 23) and the app's <a href=
  "{@docRoot}guide/topics/manifest/uses-sdk-element.html#target"
  ><code>targetSdkVersion</code></a> is 23 or higher, the following system
  behavior applies when your app requests a dangerous permission:
</p>

<ul>
  <li>If an app requests a dangerous permission listed in its manifest, and the app
  does not currently have any permissions in the permission group, the system
  shows a dialog box to the user describing the permission group that the app
  wants access to. The dialog box does not describe the specific permission
  within that group. For example, if an app requests the {@link
  android.Manifest.permission#READ_CONTACTS READ_CONTACTS} permission, the
  system dialog box just says the app needs access to the device's contacts. If
  the user grants approval, the system gives the app just the permission it
  requested.
  </li>

  <li>If an app requests a dangerous permission listed in its manifest, and the app
  already has another dangerous permission in the same permission group, the
  system immediately grants the permission without any interaction with the
  user. For example, if an app had previously requested and been granted the
  {@link android.Manifest.permission#READ_CONTACTS READ_CONTACTS} permission,
  and it then requests {@link android.Manifest.permission#WRITE_CONTACTS
  WRITE_CONTACTS}, the system immediately grants that permission.
  </li>
</ul>

<p class="aside">
  Any permission can belong to a permission group, including normal permissions
  and permissions defined by your app.
  However, a permission's group only affects the user experience if the
  permission is dangerous. You can ignore the permission group for normal
  permissions.
</p>

<p>
  If the device is running Android 5.1 (API level 22) or lower, or the app's
  <a href="{@docRoot}guide/topics/manifest/uses-sdk-element.html#target"
  ><code>targetSdkVersion</code></a> is 22 or lower, the system asks the user
  to grant the permissions at install time. Once again, the system just tells
  the user what permission <em>groups</em> the app needs, not the individual
  permissions.
</p>

<p class="table-caption" id="permission-groups">
  <strong>Table 1.</strong> Dangerous permissions and permission groups.</p>
<table>
  <tr>
    <th scope="col">Permission Group</th>
    <th scope="col">Permissions</th>
  </tr>

  <tr>
    <td>{@link android.Manifest.permission_group#CALENDAR CALENDAR}</td>
    <td>
      <ul>
        <li>
          {@link android.Manifest.permission#READ_CALENDAR READ_CALENDAR}
        </li>
      </ul>
      <ul>
        <li>
          {@link android.Manifest.permission#WRITE_CALENDAR WRITE_CALENDAR}
        </li>
      </ul>
    </td>
  </tr>

  <tr>
    <td>{@link android.Manifest.permission_group#CAMERA CAMERA}</td>
    <td>
      <ul>
        <li>
          {@link android.Manifest.permission#CAMERA CAMERA}
        </li>
      </ul>
    </td>
  </tr>

  <tr>
    <td>{@link android.Manifest.permission_group#CONTACTS CONTACTS}</td>
    <td>
      <ul>
        <li>
          {@link android.Manifest.permission#READ_CONTACTS READ_CONTACTS}
        </li>
        <li>
          {@link android.Manifest.permission#WRITE_CONTACTS WRITE_CONTACTS}
        </li>
        <li>
          {@link android.Manifest.permission#GET_ACCOUNTS GET_ACCOUNTS}
        </li>
      </ul>
    </td>
  </tr>

  <tr>
    <td>{@link android.Manifest.permission_group#LOCATION LOCATION}</td>
    <td>
      <ul>
        <li>
          {@link android.Manifest.permission#ACCESS_FINE_LOCATION ACCESS_FINE_LOCATION}
        </li>
        <li>
          {@link android.Manifest.permission#ACCESS_COARSE_LOCATION ACCESS_COARSE_LOCATION}
        </li>
      </ul>
    </td>
  </tr>

  <tr>
    <td>{@link android.Manifest.permission_group#MICROPHONE MICROPHONE}</td>
    <td>
      <ul>
        <li>
          {@link android.Manifest.permission#RECORD_AUDIO RECORD_AUDIO}
        </li>
      </ul>
    </td>
  </tr>

  <tr>
    <td>{@link android.Manifest.permission_group#PHONE PHONE}</td>
    <td>
      <ul>
        <li>
          {@link android.Manifest.permission#READ_PHONE_STATE READ_PHONE_STATE}
        </li>
        <li>
          {@link android.Manifest.permission#CALL_PHONE CALL_PHONE}
        </li>
        <li>
          {@link android.Manifest.permission#READ_CALL_LOG READ_CALL_LOG}
        </li>
        <li>
          {@link android.Manifest.permission#WRITE_CALL_LOG WRITE_CALL_LOG}
        </li>
        <li>
          {@link android.Manifest.permission#ADD_VOICEMAIL ADD_VOICEMAIL}
        </li>
        <li>
          {@link android.Manifest.permission#USE_SIP USE_SIP}
        </li>
        <li>
          {@link android.Manifest.permission#PROCESS_OUTGOING_CALLS PROCESS_OUTGOING_CALLS}
        </li>
      </ul>
    </td>
  </tr>

  <tr>
    <td>{@link android.Manifest.permission_group#SENSORS SENSORS}</td>
    <td>
      <ul>
        <li>
          {@link android.Manifest.permission#BODY_SENSORS BODY_SENSORS}
        </li>
      </ul>
    </td>
  </tr>

  <tr>
    <td>{@link android.Manifest.permission_group#SMS SMS}</td>
    <td>
      <ul>
        <li>
          {@link android.Manifest.permission#SEND_SMS SEND_SMS}
        </li>
        <li>
          {@link android.Manifest.permission#RECEIVE_SMS RECEIVE_SMS}
        </li>
        <li>
          {@link android.Manifest.permission#READ_SMS READ_SMS}
        </li>
        <li>
          {@link android.Manifest.permission#RECEIVE_WAP_PUSH RECEIVE_WAP_PUSH}
        </li>
        <li>
          {@link android.Manifest.permission#RECEIVE_MMS RECEIVE_MMS}
        </li>
      </ul>
    </td>
  </tr>

  <tr>
    <td>
      {@link android.Manifest.permission_group#STORAGE STORAGE}
    </td>
    <td>
      <ul>
        <li>
          {@link android.Manifest.permission#READ_EXTERNAL_STORAGE
              READ_EXTERNAL_STORAGE}
        </li>
        <li>
          {@link android.Manifest.permission#WRITE_EXTERNAL_STORAGE
              WRITE_EXTERNAL_STORAGE}
        </li>
      </ul>
    </td>
  </tr>

</table>


<a name="declaring"></a>
<h2 id="defining">Defining and Enforcing Permissions</h2>

<p>To enforce your own permissions, you must first declare them in your
<code>AndroidManifest.xml</code> using one or more
<code>{@link android.R.styleable#AndroidManifestPermission &lt;permission&gt;}</code>
tags.</p>

<p>For example, an application that wants to control who can start one
of its activities could declare a permission for this operation as follows:</p>

<pre>&lt;manifest xmlns:android=&quot;http://schemas.android.com/apk/res/android&quot;
    package=&quot;com.me.app.myapp&quot; &gt;
    &lt;permission android:name=&quot;com.me.app.myapp.permission.DEADLY_ACTIVITY&quot;
        android:label=&quot;&#64;string/permlab_deadlyActivity&quot;
        android:description=&quot;&#64;string/permdesc_deadlyActivity&quot;
        android:permissionGroup=&quot;android.permission-group.COST_MONEY&quot;
        android:protectionLevel=&quot;dangerous&quot; /&gt;
    ...
&lt;/manifest&gt;</pre>

<p>The {@link android.R.styleable#AndroidManifestPermission_protectionLevel
&lt;protectionLevel&gt;} attribute is required, telling the system how the
user is to be informed of applications requiring the permission, or who is
allowed to hold that permission, as described in the linked documentation.</p>

<p>The {@link android.R.styleable#AndroidManifestPermission_permissionGroup
&lt;permissionGroup&gt;} attribute is optional, and only used to help the system display
permissions to the user.  You will usually want to set this to either a standard
system group (listed in {@link android.Manifest.permission_group
android.Manifest.permission_group}) or in more rare cases to one defined by
yourself.  It is preferred to use an existing group, as this simplifies the
permission UI shown to the user.</p>

<p>Note that both a label and description should be supplied for the
permission. These are string resources that can be displayed to the user when
they are viewing a list of permissions
(<code>{@link android.R.styleable#AndroidManifestPermission_label android:label}</code>)
or details on a single permission (
<code>{@link android.R.styleable#AndroidManifestPermission_description android:description}</code>).
The label should be short, a few words
describing the key piece of functionality the permission is protecting. The
description should be a couple sentences describing what the permission allows
a holder to do. Our convention for the description is two sentences, the first
describing the permission, the second warning the user of what bad things
can happen if an application is granted the permission.</p>

<p>Here is an example of a label and description for the CALL_PHONE
permission:</p>

<pre>
    &lt;string name=&quot;permlab_callPhone&quot;&gt;directly call phone numbers&lt;/string&gt;
    &lt;string name=&quot;permdesc_callPhone&quot;&gt;Allows the application to call
        phone numbers without your intervention. Malicious applications may
        cause unexpected calls on your phone bill. Note that this does not
        allow the application to call emergency numbers.&lt;/string&gt;
</pre>

<p>You can look at the permissions currently defined in the system with the
Settings app and the shell command <code>adb shell pm list permissions</code>.
To use the Settings app, go to Settings &gt; Applications.  Pick an app and
scroll down to see the permissions that the app uses. For developers, the adb '-s'
option displays the permissions in a form similar to how the user will see them:</p>

<pre>
$ adb shell pm list permissions -s
All Permissions:

Network communication: view Wi-Fi state, create Bluetooth connections, full
Internet access, view network state

Your location: access extra location provider commands, fine (GPS) location,
mock location sources for testing, coarse (network-based) location

Services that cost you money: send SMS messages, directly call phone numbers

...</pre>

<a name="manifest"></a>
<h3>Enforcing Permissions in AndroidManifest.xml</h3>

<p>High-level permissions restricting access to entire components of the
system or application can be applied through your
<code>AndroidManifest.xml</code>. All that this requires is including an {@link
android.R.attr#permission android:permission} attribute on the desired
component, naming the permission that will be used to control access to
it.</p>

<p><strong>{@link android.app.Activity}</strong> permissions
(applied to the
{@link android.R.styleable#AndroidManifestActivity &lt;activity&gt;} tag)
restrict who can start the associated
activity.  The permission is checked during
{@link android.content.Context#startActivity Context.startActivity()} and
{@link android.app.Activity#startActivityForResult Activity.startActivityForResult()};
if the caller does not have
the required permission then {@link java.lang.SecurityException} is thrown
from the call.</p>

<p><strong>{@link android.app.Service}</strong> permissions
(applied to the
{@link android.R.styleable#AndroidManifestService &lt;service&gt;} tag)
restrict who can start or bind to the
associated service.  The permission is checked during
{@link android.content.Context#startService Context.startService()},
{@link android.content.Context#stopService Context.stopService()} and
{@link android.content.Context#bindService Context.bindService()};
if the caller does not have
the required permission then {@link java.lang.SecurityException} is thrown
from the call.</p>

<p><strong>{@link android.content.BroadcastReceiver}</strong> permissions
(applied to the
{@link android.R.styleable#AndroidManifestReceiver &lt;receiver&gt;} tag)
restrict who can send broadcasts to the associated receiver.
The permission is checked <em>after</em>
{@link android.content.Context#sendBroadcast Context.sendBroadcast()} returns,
as the system tries
to deliver the submitted broadcast to the given receiver.  As a result, a
permission failure will not result in an exception being thrown back to the
caller; it will just not deliver the intent.  In the same way, a permission
can be supplied to
{@link android.content.Context#registerReceiver(android.content.BroadcastReceiver, android.content.IntentFilter, String, android.os.Handler)
Context.registerReceiver()}
to control who can broadcast to a programmatically registered receiver.
Going the other way, a permission can be supplied when calling
{@link android.content.Context#sendBroadcast(Intent, String) Context.sendBroadcast()}
to restrict which BroadcastReceiver objects are allowed to receive the broadcast (see
below).</p>

<p><strong>{@link android.content.ContentProvider}</strong> permissions
(applied to the
{@link android.R.styleable#AndroidManifestProvider &lt;provider&gt;} tag)
restrict who can access the data in
a {@link android.content.ContentProvider}.  (Content providers have an important
additional security facility available to them called
<a href="#uri">URI permissions</a> which is described later.)
Unlike the other components,
there are two separate permission attributes you can set:
{@link android.R.attr#readPermission android:readPermission} restricts who
can read from the provider, and
{@link android.R.attr#writePermission android:writePermission} restricts
who can write to it.  Note that if a provider is protected with both a read
and write permission, holding only the write permission does not mean
you can read from a provider.  The permissions are checked when you first
retrieve a provider (if you don't have either permission, a SecurityException
will be thrown), and as you perform operations on the provider.  Using
{@link android.content.ContentResolver#query ContentResolver.query()} requires
holding the read permission; using
{@link android.content.ContentResolver#insert ContentResolver.insert()},
{@link android.content.ContentResolver#update ContentResolver.update()},
{@link android.content.ContentResolver#delete ContentResolver.delete()}
requires the write permission.
In all of these cases, not holding the required permission results in a
{@link java.lang.SecurityException} being thrown from the call.</p>


<a name="broadcasts"></a>
<h3>Enforcing Permissions when Sending Broadcasts</h3>

<p>In addition to the permission enforcing who can send Intents to a
registered {@link android.content.BroadcastReceiver} (as described above), you
can also specify a required permission when sending a broadcast. By calling {@link
android.content.Context#sendBroadcast(android.content.Intent,String)
Context.sendBroadcast()} with a
permission string, you require that a receiver's application must hold that
permission in order to receive your broadcast.</p>

<p>Note that both a receiver and a broadcaster can require a permission. When
this happens, both permission checks must pass for the Intent to be delivered
to the associated target.</p>


<a name="enforcement"></a>
<h3>Other Permission Enforcement</h3>

<p>Arbitrarily fine-grained permissions can be enforced at any call into a
service. This is accomplished with the {@link
android.content.Context#checkCallingPermission Context.checkCallingPermission()}
method. Call with a desired
permission string and it will return an integer indicating whether that
permission has been granted to the current calling process. Note that this can
only be used when you are executing a call coming in from another process,
usually through an IDL interface published from a service or in some other way
given to another process.</p>

<p>There are a number of other useful ways to check permissions. If you have
the pid of another process, you can use the Context method {@link
android.content.Context#checkPermission(String, int, int) Context.checkPermission(String, int, int)}
to check a permission against that pid. If you have the package name of another
application, you can use the direct PackageManager method {@link
android.content.pm.PackageManager#checkPermission(String, String)
PackageManager.checkPermission(String, String)}
to find out whether that particular package has been granted a specific permission.</p>


<a name="uri"></a>
<h2>URI Permissions</h2>

<p>The standard permission system described so far is often not sufficient
when used with content providers.  A content provider may want to
protect itself with read and write permissions, while its direct clients
also need to hand specific URIs to other applications for them to operate on.
A typical example is attachments in a mail application.  Access to the mail
should be protected by permissions, since this is sensitive user data.  However,
if a URI to an image attachment is given to an image viewer, that image viewer
will not have permission to open the attachment since it has no reason to hold
a permission to access all e-mail.</p>

<p>The solution to this problem is per-URI permissions: when starting an
activity or returning a result to an activity, the caller can set
{@link android.content.Intent#FLAG_GRANT_READ_URI_PERMISSION
Intent.FLAG_GRANT_READ_URI_PERMISSION} and/or
{@link android.content.Intent#FLAG_GRANT_WRITE_URI_PERMISSION
Intent.FLAG_GRANT_WRITE_URI_PERMISSION}.  This grants the receiving activity
permission access the specific data URI in the Intent, regardless of whether
it has any permission to access data in the content provider corresponding
to the Intent.</p>

<p>This mechanism allows a common capability-style model where user interaction
(opening an attachment, selecting a contact from a list, etc) drives ad-hoc
granting of fine-grained permission.  This can be a key facility for reducing
the permissions needed by applications to only those directly related to their
behavior.</p>

<p>The granting of fine-grained URI permissions does, however, require some
cooperation with the content provider holding those URIs.  It is strongly
recommended that content providers implement this facility, and declare that
they support it through the
{@link android.R.styleable#AndroidManifestProvider_grantUriPermissions
android:grantUriPermissions} attribute or
{@link android.R.styleable#AndroidManifestGrantUriPermission
&lt;grant-uri-permissions&gt;} tag.</p>

<p>More information can be found in the
{@link android.content.Context#grantUriPermission Context.grantUriPermission()},
{@link android.content.Context#revokeUriPermission Context.revokeUriPermission()}, and
{@link android.content.Context#checkUriPermission Context.checkUriPermission()}
methods.</p>

<div class="next-docs">
<div class="col-6">
  <h2 class="norule">Continue reading about:</h2>
  <dl>
    <dt><a href="{@docRoot}guide/topics/manifest/uses-feature-element.html#permissions"
        >Permissions that Imply Feature Requirements</a></dt>
    <dd>Information about how requesting some permissions will implicitly restrict your app
    to devices that include the corresponding hardware or software feature.</dd>
    <dt><a href="{@docRoot}guide/topics/manifest/uses-permission-element.html">{@code
    &lt;uses-permission>}</a></dt>
    <dd>API reference for the manifest tag that declare's your app's required system permissions.
    </dd>
    <dt>{@link android.Manifest.permission}</dt>
    <dd>API reference for all system permissions.</dd>
  </dl>
</div>
<div class="col-6">
  <h2 class="norule">You might also be interested in:</h2>
  <dl>
    <dt><a href="{@docRoot}guide/practices/compatibility.html"
        >Device Compatibility</a></dt>
    <dd>Information about Android works on different types of devices and an introduction
    to how you can optimize your app for each device or restrict your app's availability
    to different devices.</dd>
    <dt><a href="http://source.android.com/devices/tech/security/index.html"
        class="external-link">Android Security Overview</a></dt>
    <dd>A detailed discussion about the Android platform's security model.</dd>
  </dl>
</div>
</div>