src/security/index.jd

page.title=Security
@jd:body
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<div id="qv-wrapper">
  <div id="qv">
    <h2>In this document</h2>
    <ol id="auto-toc"></ol>
  </div>
</div>

<p>
Android incorporates industry-leading security features and works with
developers and device implementers to keep the Android platform and ecosystem
safe. A robust security model is essential to enable a vigorous ecosystem of
applications and devices built on and around the Android platform and supported
by cloud services. As a result, through its entire development lifecycle,
Android has been subject to a rigorous security program.
</p>
<p>
<strong>Android is designed to be open</strong>. Android applications use
advanced hardware and software, as well as local and served data, exposed
through the platform to bring innovation and value to consumers. To realize that
value, the platform offers an application environment that protects the
confidentiality, integrity, and availability of users, data, applications, the
device, and the network.
</p>
<p>
Securing an open platform requires a strong security architecture and rigorous
security programs. Android was designed with multi-layered security that is
flexible enough to support an open platform while still protecting all users of
the platform. For information about reporting security issues and the update
process, see <a href="{@docRoot}security/overview/updates-resources.html">Security
Updates and Resources</a>.
</p>
<p>
<strong>Android is designed for developers</strong>. Security controls were
designed to reduce the burden on developers. Security-savvy developers can
easily work with and rely on flexible security controls. Developers less
familiar with security will be protected by safe defaults.
</p>
<p>
In addition to providing a stable platform to build upon, Android gives
additional support to developers in a number of ways. The Android security team
looks for potential vulnerabilities in apps and suggests ways to fix those
issues. For devices with Google Play, Play Services delivers security updates
for critical software libraries, such as OpenSSL, which is used to secure
application communications. Android security released a tool for testing SSL
(<a href="https://github.com/google/nogotofail">nogotofail</a>) that helps
developers find potential security issues on whichever platform they are
developing.
</p>
<p>
More information for Android app developers can be found on
<a href="https://developer.android.com/training/best-security.html">developer.android.com</a>.
</p>
<p>
<strong>Android is designed for users</strong>. Users are provided visibility
into permissions requested by each application and control over those
permissions. This design includes the expectation that attackers would attempt
to perform common attacks, such as social engineering attacks to convince device
users to install malware, and attacks on third-party applications on Android.
Android was designed to both reduce the probability of these attacks and greatly
limit the impact of the attack in the event it was successful. Android security
continues to progress once the device is in the user's hands: Android works with
<a href="{@docRoot}security/overview/acknowledgements.html">partners and the
public</a> to provide patches for any Android device that is continuing to
receive security updates.
</p>
<p>
More information for end users can be found in the <a
href="https://support.google.com/nexus/answer/6172890">Nexus help center</a> or
your device manufacturer’s help center.
</p>
<p>
This documentation outlines the goals of the Android security program, describes
the fundamentals of the Android security architecture, and answers the most
pertinent questions for system architects and security analysts. It focuses on
the security features of Android's core platform and does not discuss security
issues that are unique to specific applications, such as those related to the
browser or SMS application.
</p>

<h2 id="background">Background</h2>
<p>
Android provides an open source platform and application environment for mobile
devices.
</p>
<p>
The sections and pages below describe the security features of the Android
platform. <em>Figure 1</em> summarizes the security components and
considerations of the various levels of the Android software stack. Each
component assumes that the components below are properly secured. With the
exception of a small amount of Android OS code running as root, all code above
the Linux Kernel is restricted by the Application Sandbox.
</p>

<p><img alt="Figure 1: Android software stack" src="images/android_software_stack.png" /></p>
<p  class="img-caption">
<strong>Figure 1</strong>. Android software stack.
</p>
<p>
The main Android platform building blocks are:
</p>
<ul>
  <li><strong>Device hardware</strong>: Android runs on a wide range of hardware
  configurations including smart phones, tablets, watches, automobiles, smart TVs,
  OTT gaming boxes, and set-top-boxes. Android is processor-agnostic, but it does
  take advantage of some hardware-specific security capabilities such as ARM
  eXecute-Never.</li>
  <li><strong>Android operating system</strong>: The core operating system is
  built on top of the Linux kernel. All device resources, like camera functions,
  GPS data, Bluetooth functions, telephony functions, network connections, etc.
  are accessed through the operating system.</li>
  <li><strong>Android Application Runtime</strong>: Android applications are most
  often written in the Java programming language and run in the Android runtime
  (ART). However, many applications, including core Android services and
  applications, are native applications or include native libraries. Both ART and
  native applications run within the same security environment, contained within
  the Application Sandbox. Applications get a dedicated part of the filesystem in
  which they can write private data, including databases and raw files.</li>
</ul>
<p>
Android applications extend the core Android operating system. There are two
primary sources for applications:
</p>
<ul>
  <li><strong>Pre-installed applications</strong>: Android includes a set of
  pre-installed applications including phone, email, calendar, web browser, and
  contacts. These function both as user applications and to provide key device
  capabilities that can be accessed by other applications. Pre-installed
  applications may be part of the open source Android platform, or they may be
  developed by a device manufacturer for a specific device.</li>
  <li><strong>User-installed applications</strong>: Android provides an open
  development environment that supports any third-party application. Google Play
  offers users hundreds of thousands of applications.</li>
</ul>

<h2 id="google-security-services">Google security services</h2>
<p>
Google provides a set of cloud-based services that are available to compatible
Android devices with <a href="https://www.android.com/gms/">Google Mobile
Services</a>. While these services are not part of the Android Open Source
Project, they are included on many Android devices. For more information on
some of these services, see Android Security’s
<a href="http://static.googleusercontent.com/media/source.android.com/en//security/reports/Google_Android_Security_2015_Report_Final.pdf">2015
Year in Review</a>.
</p>
<p>
The primary Google security services are:
</p>
<ul>
  <li><strong>Google Play</strong>: Google Play is a collection of services that
  allow users to discover, install, and purchase applications from their Android
  device or the web. Google Play makes it easy for developers to reach Android
  users and potential customers. Google Play also provides community review,
  application
  <a href="https://developer.android.com/guide/publishing/licensing.html">license
  verification</a>, application security scanning, and other security services.</li>
  <li><strong>Android updates</strong>: The Android update service delivers new
  capabilities and security updates to selected Android devices, including updates
  through the web or over the air (OTA).</li>
  <li><strong>Application services</strong>: Frameworks that allow Android
  applications to use cloud capabilities such as (<a
  href="https://developer.android.com/guide/topics/data/backup.html">backing
  up</a>) application data and settings and cloud-to-device messaging
  (<a href="https://developers.google.com/cloud-messaging/">C2DM</a>) for push
  messaging.</li>
  <li><strong>Verify Apps</strong>: Warn or automatically block the installation
  of harmful applications, and continually scan applications on the device,
  warning about or removing
  <a href="https://support.google.com/accounts/answer/2812853">harmful apps</a>.
  </li>
  <li><strong>SafetyNet</strong>: A privacy preserving intrusion detection system
  to assist Google tracking and mitigating known security threats in addition to
  identifying new security threats.</li>
  <li><strong>SafetyNet Attestation</strong>: Third-party API to determine
  whether the device is CTS compatible. <a
  href="http://developer.android.com/training/safetynet/index.html">Attestation</a>
  can also assist identify the Android app communicating with the app server.</li>
  <li><strong>Android Device Manager</strong>: A
  <a href="https://www.google.com/android/devicemanager">web app</a> and
  <a href="https://play.google.com/store/apps/details?id=com.google.android.apps.adm">Android
  app</a> to locate lost or stolen device.</li>
</ul>

<h2 id="security-program-overview">Security program overview</h2>
<p>
The key components of the Android Security Program include:
</p>
<ul>
  <li><strong>Design review</strong>: The Android security process begins early in
  the development lifecycle with the creation of a rich and configurable security
  model and design. Each major feature of the platform is reviewed by engineering
  and security resources, with appropriate security controls integrated into the
  architecture of the system.</li>
  <li><strong>Penetration testing and code review</strong>: During the development
  of the platform, Android-created and open source components are subject to
  vigorous security reviews. These reviews are performed by the Android Security
  Team, Google’s Information Security Engineering team, and independent security
  consultants. The goal of these reviews is to identify weaknesses and possible
  vulnerabilities well before major releases, and to simulate the types of
  analysis that will be performed by external security experts upon release.</li>
  <li><strong>Open source and community review</strong>: The Android Open Source
  Project enables broad security review by any interested party. Android also uses
  open source technologies that have undergone significant external security
  review, such as the Linux kernel. Google Play provides a forum for users and
  companies to provide information about specific applications directly to users.</li>
  <li><strong>Incident Response</strong>: Even with all of these precautions,
  security issues may occur after shipping, which is why the Android project has
  created a comprehensive security response process. Full-time Android security
  team members monitor Android-specific and the general security community for
  discussion of potential vulnerabilities and review
  <a href="{@docRoot}security/overview/updates-resources.html#android_security_bug_lifecycle">security
  bugs</a> filed on the Android bug database. Upon the discovery of legitimate
  issues, the Android team has a response process that enables the rapid
  mitigation of vulnerabilities to ensure that potential risk to all Android users
  is minimized. These cloud-supported responses can include updating the Android
  platform (over-the-air updates), removing applications from Google Play, and
  removing applications from devices in the field.</li>
  <li><strong>Monthly security updates</strong>: The Android security team
  provides <a href="{@docRoot}security/bulletin/index.html">monthly
  updates</a> to Google Nexus devices and all of our device manufacturing
  partners.</li>
</ul>

<h2 id="platform-security-architecture">Platform security architecture</h2>
<p>
Android seeks to be the most secure and usable operating system for mobile
platforms by re-purposing traditional operating system security controls to:
</p>
<ul>
  <li>Protect application and user data</li>
  <li>Protect system resources (including the network)</li>
  <li>Provide application isolation from the system, other applications, and from
  the user</li>
</ul>
<p>
To achieve these objectives, Android provides these key security features:
</p>
<ul>
  <li>Robust security at the OS level through the Linux kernel</li>
  <li>Mandatory application sandbox for all applications</li>
  <li>Secure interprocess communication</li>
  <li>Application signing</li>
  <li>Application-defined and user-granted permissions</li>
</ul>