773 lines
54 KiB
HTML
773 lines
54 KiB
HTML
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<title>Usage guide | GrapheneOS</title>
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</head>
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<body>
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<header>
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<nav id="site-menu">
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<ul>
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<li><a href="/"><img src="/mask-icon.svg" alt=""/>GrapheneOS</a></li>
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<li><a href="/features">Features</a></li>
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<li><a href="/install/">Install</a></li>
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<li><a href="/build">Build</a></li>
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<li aria-current="page"><a href="/usage">Usage</a></li>
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<li><a href="/faq">FAQ</a></li>
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<li><a href="/releases">Releases</a></li>
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<li><a href="/source">Source</a></li>
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<li><a href="/history/">History</a></li>
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<li><a href="/articles/">Articles</a></li>
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<li><a href="/donate">Donate</a></li>
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<li><a href="/contact">Contact</a></li>
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</ul>
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</nav>
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</header>
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<main id="usage">
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<h1><a href="#usage">Usage guide</a></h1>
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<p>This is a guide covering some aspects of using GrapheneOS. See the
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<a href="/features">features page</a> for a list of GrapheneOS features.</p>
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<nav id="table-of-contents">
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<h2><a href="#table-of-contents">Table of contents</a></h2>
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<ul>
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<li>
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<a href="#system-navigation">System navigation</a>
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<ul>
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<li><a href="#gesture-navigation">Gesture navigation</a></li>
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<li><a href="#2-button-navigation">2-button navigation</a></li>
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<li><a href="#3-button-navigation">3-button navigation</a></li>
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</ul>
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</li>
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<li><a href="#accessibility">Accessibility</a></li>
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<li><a href="#auditor">Auditor</a></li>
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<li>
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<a href="#updates">Updates</a>
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<ul>
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<li><a href="#updates-settings">Settings</a></li>
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<li><a href="#updates-security">Security</a></li>
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<li><a href="#updates-disabling">Disabling</a></li>
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<li><a href="#updates-sideloading">Sideloading</a></li>
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</ul>
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</li>
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<li><a href="#web-browsing">Web browsing</a></li>
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<li><a href="#camera">Camera</a></li>
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<li><a href="#exec-spawning">Exec spawning</a></li>
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<li><a href="#bugs-uncovered-by-security-features">Bugs uncovered by security features</a></li>
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<li>
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<a href="#wifi-privacy">Wi-Fi privacy</a>
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<ul>
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<li><a href="#wifi-privacy-scanning">Scanning</a></li>
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<li><a href="#wifi-privacy-associated">Associated with an Access Point (AP)</a></li>
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</ul>
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</li>
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<li><a href="#lte-only-mode">LTE-only mode</a></li>
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<li>
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<a href="#sandboxed-play-services">Sandboxed Play services (experimental)</a>
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<ul>
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<li><a href="#sandboxed-play-services-limitations">Limitations</a></li>
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</ul>
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</li>
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</ul>
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</nav>
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<section id="system-navigation">
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<h2><a href="#system-navigation">System navigation</a></h2>
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<p>By default, GrapheneOS uses gesture-based navigation. We recommend reading our
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guide on gesture navigation and giving it a chance even if you think you won't
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like it. Our experience is that when armed with the appropriate knowledge, the
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vast majority of users prefer the newer gesture navigation approach.</p>
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<p>The system navigation mode can be configured in Settings → System → Gestures →
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System navigation. The same menu is also available in Settings → Accessibility →
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System navigation.</p>
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<section id="gesture-navigation">
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<h3><a href="#gesture-navigation">Gesture navigation</a></h3>
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<p>The bottom of the screen is a reserved touch zone for system navigation. A
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line is displayed in the center to show that the navigation bar is present
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across the entire bottom of the screen. In most apps, this area will display
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padding. Modern apps are able to tell the OS that they can handle not having
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the padding to display app content there while still not being able to receive
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touches from it. Open up the Settings app for an example.</p>
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<p>Swiping up from the navigation bar while removing your finger from the
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screen is the <strong>Home</strong> gesture.</p>
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<p>Swiping up from the navigation bar while holding your finger on the screen
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before releasing is the <strong>Recent Apps</strong> gesture. The most
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recently opened activity is always on the furthest right. Each step left goes
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one step back through the history of recently opened apps. Opening an app with
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the recent apps activity will place it on the furthest right in the recent
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apps order just like a new app being opened.</p>
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<p>The recent apps activity has a screenshot button as an alternative to
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holding power and volume down while using an app.</p>
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<p>Rather than opening the recent apps activity, you can swipe left on the
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navigation bar for the <strong>Previous</strong> app and swipe right for the
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<strong>Next</strong> app. This will not change the recent apps order. This is
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usually the best way to navigate through recent apps.</p>
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<p>Swiping from either the left or the right of the screen within the app (not
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the navigation bar) is the <strong>Back</strong> gesture. Apps are supposed to
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avoid implementing conflicting gestures, but have the option to override this
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gesture if they truly need to get rid of it. However, many apps without active
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development of their UI design still haven't addressed this despite gestures
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being the default for 2 years on Google Android. You can avoid triggering the
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back gesture in one of 2 easy ways: avoid swiping from right near the edge or
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hold your finger on the side of the screen for a moment before swiping. The
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more advanced option is using a diagonal swipe pointing sharply to the bottom
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of the screen since this will bypass the back gesture but will still trigger
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most app gestures. The advanced option is the most convenient approach once
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you get used to doing it.</p>
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<p>The launcher uses a swipe up gesture starting anywhere on the screen to
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open the app drawer from the home screen. You need to start that gesture above
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the system navigation bar since any gesture starting on the navigation bar is
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handled by the OS as a system navigation gesture.</p>
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</section>
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<section id="2-button-navigation">
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<h3><a href="#2-button-navigation">2-button navigation</a></h3>
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<p>2-button navigation is a legacy mode not supported anymore by Google
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Android on the Pixel 4 and later. It will likely be removed in a future
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release of GrapheneOS. You should use <a href="#3-button-navigation">3-button
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navigation</a> if you want the traditional button-based navigation.</p>
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<p>A large row across the bottom of the screen is reserved for navigation
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buttons. The <strong>Back</strong> button is on the left and the
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<strong>Home</strong> button is in the center.</p>
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<p>Swiping up from the navigation bar while removing your finger from the
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screen is the <strong>Recent apps</strong> gesture. The most recently opened
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activity is always on the furthest right. Each step left goes one step back
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through the history of recently opened apps. Opening an app with the recent
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apps activity will place it on the furthest right in the recent apps
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order just like a new app being opened.</p>
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<p>2-button navigation provides the recent apps activity with the launcher. It
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shows the recent apps above the bottom row of the home screen and the search
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integration not used in GrapheneOS. The usual launcher features work including
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swiping up anywhere on the screen to open the app drawer. Due to the launcher
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integration, the screenshot button available in the other modes isn't present.
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Instead, a screenshot button is added to the global action menu accessed by
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holding the power button.</p>
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</section>
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<section id="3-button-navigation">
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<h3><a href="#3-button-navigation">3-button navigation</a></h3>
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<p>3-button navigation is Android's oldest touchscreen-based navigation
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system. It will remain supported for the foreseeable future to provide
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accessibility for users unable to easily use the gestures. It's older than
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2-button navigation but isn't considered a legacy feature.</p>
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<p>A large row across the bottom of the screen is reserved for navigation
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buttons. The <strong>Back</strong> button is on the left, the
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<strong>Home</strong> button is in the center and the <strong>Recent
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Apps</strong> button is on the right.</p>
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<p>In the recent apps activity, the most recently opened activity is always on
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the furthest right. Each step left goes one step back through the history of
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recently opened apps. Opening an app with the recent apps activity will place
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it on the furthest right in the recent apps order just like a new app being
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opened.</p>
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<p>The recent apps activity has a screenshot button as an alternative to
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holding power and volume down while using an app.</p>
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</section>
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</section>
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<section id="accessibility">
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<h2><a href="#accessibility">Accessibility</a></h2>
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<p>GrapheneOS includes all of the accessibility features from the Android Open
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Source Project and strives to fill in the gaps from not including Google apps and
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services. We include our own fork of the open source TalkBack and Switch Access
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accessibility services along with a Monochromacy option for the standard color
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correction menu.</p>
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<p>GrapheneOS does not yet include a text-to-speech (TTS) service in the base OS
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due to limitations of the available options. Including one is planned in the
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future when a suitable option is available. RHVoice and eSpeak NG are both open
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source and are the most common choices by GrapheneOS users. Both of these mostly
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work fine but have licensing issues and don't support Direct Boot so they cannot
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be used before the initial unlock of the device. Installing and setting up either
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one of these or another TTS app will get TalkBack working. TalkBack itself
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supports Direct Boot and works before the first unlock but it needs to have a TTS
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app supporting it in order to do more than playing the activation sound before the
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first unlock. After installing a TTS service, you need to select it in the OS
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configuration to accept activating it. The OS will display one of them as already
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selected, but it won't simply work from being installed as that wouldn't be safe.
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This is the same as the stock OS but it comes with one set up already.</p>
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<p>GrapheneOS disables showing the characters as passwords are typed by default.
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You can enable this in Settings ➔ Privacy.</p>
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<p>Third party accessibility services can be installed and activated. This
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includes the ones made by Google. Most of these will work but some may have a hard
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dependency on functionality from Google Play services for some of their
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functionality or to run at all. Accessibility services are very powerful and we
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strongly recommend against using third party implementations if you can get by
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well without them. We plan to add safeguards in this area while still keeping them
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working without problematic barriers.</p>
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</section>
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<section id="auditor">
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<h2><a href="#auditor">Auditor</a></h2>
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<p>See the <a href="https://attestation.app/tutorial">tutorial page on the site for the attestation sub-project</a>.</p>
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</section>
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<section id="updates">
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<h2><a href="#updates">Updates</a></h2>
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<p>The update system implements automatic background updates. It checks for updates
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approximately once every four hours when there's network connectivity and then
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downloads and installs updates in the background. It will pick up where it left off if
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downloads are interrupted, so you don't need to worry about interrupting it.
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Similarly, interrupting the installation isn't a risk because updates are installed to
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a secondary installation of GrapheneOS which only becomes the active installation
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after the update is complete. Once the update is complete, you'll be informed with a
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notification and simply need to reboot with the button in the notification or via a
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normal reboot. If the new version fails to boot, the OS will be rolled back to the
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past version and the updater will attempt to download and install the update
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again.</p>
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<p>The updater will use incremental (delta) updates to download only changes rather
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than the whole OS when one is available to go directly from the installed version to
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the latest version. As long as you have working network connectivity on a regular
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basis and reboot when asked, you'll almost always be on one of the past couple
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versions of the OS which will minimize bandwidth usage since incrementals will always
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be available.</p>
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<p>The updater works while the device is locked / idle, including before the first
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unlock since it's explicitly designed to be able to run before decryption of user
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data.</p>
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<p>Release changelogs are available <a href="/releases#changelog">in a section on the releases page</a>.</p>
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<section id="updates-settings">
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<h3><a href="#updates-settings">Settings</a></h3>
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<p>The settings are available in the Settings app in System ➔ Advanced ➔ Update
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settings.</p>
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<p>The "Check for updates" option will manually trigger an update check as soon as
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possible. It will still wait for the configuration conditions listed below to be
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satisfied, such as being connected to the internet via one of the permitted network
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types.</p>
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<p>The "Release channel" setting can be changed from the default Stable channel to the
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Beta channel if you want to help with testing. The Beta channel will usually simply
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follow the Stable channel, but the Beta channel may be used to experiment with new
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features.</p>
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<p>The "Permitted networks" setting controls which networks will be used to perform
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updates. It defaults to using any network connection. It can be set to "Non-roaming"
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to disable it when the cellular service is marked as roaming or "Unmetered" to disable
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it on cellular networks and also Wi-Fi networks marked as metered.</p>
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<p>The "Require battery above warning level" setting controls whether updates will
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only be performed when the battery is above the level where the warning message is
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shown. The standard value is at 15% capacity.</p>
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<p>Enabling the opt-in "Automatic reboot" setting allows the updater to reboot the
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device after an update once it has been idle for a long time. When this setting is
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enabled, a device can take care of any number of updates completely automatically even
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if it's left completely idle.</p>
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</section>
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<section id="updates-security">
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<h3><a href="#updates-security">Security</a></h3>
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<p>The update server isn't a trusted party since updates are signed and verified along
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with downgrade attacks being prevented. The update protocol doesn't send identifiable
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information to the update server and works well over a VPN / Tor. GrapheneOS isn't
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able to comply with a government order to build, sign and ship a malicious update to a
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specific user's device based on information like the IMEI, serial number, etc. The
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update server only ends up knowing the IP address used to connect to it and the
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version being upgraded from based on the requested incremental.</p>
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<p>Android updates can support serialno constraints to make them validate only on a
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certain device but GrapheneOS rejects any update with a serialno constraint for both
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over-the-air updates (Updater app) and sideloaded updates (recovery).</p>
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</section>
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<section id="updates-disabling">
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<h3><a href="#updates-disabling">Disabling</a></h3>
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<p>It's highly recommended to leave automatic updates enabled and to configure the
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permitted networks if the bandwidth usage is a problem on your mobile data connection.
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However, it's possible to turn off the update client by going to Settings ➔ Apps,
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enabling Show system via the menu, selecting Seamless Update Client and disabling the
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app. If you do this, you'll need to remember to enable it again to start receiving
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updates.</p>
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</section>
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<section id="updates-sideloading">
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<h3><a href="#updates-sideloading">Sideloading</a></h3>
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<p>Updates can be downloaded via
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<a href="https://grapheneos.org/releases">the releases page</a> and installed via recovery
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with adb sideloading. The zip files are signed and verified by recovery, just as they
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are by the update client within the OS. This includes providing downgrade protection,
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which prevents attempting to downgrade the version. If recovery didn't enforce these
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things, they would still be enforced via verified boot including downgrade protection
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and the attempted update would just fail to boot and be rolled back.</p>
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<p>To install one by sideloading, first, boot into recovery. You may do this either by
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using <code>adb reboot recovery</code> from the operating system, or by selecting the
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"Recovery" option in the bootloader interface.</p>
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<p>You should see the green Android lying on its back being repaired, with the text "No
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command" meaning that no command has been passed to recovery.</p>
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<p>Next, access the recovery menu by holding down the power button and pressing the volume
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up button a single time. This key combination toggles between the GUI and text-based mode
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with the menu and log output.</p>
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<p>Finally, select the "Apply update from ADB" option in the recovery menu and
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sideload the update with adb. For example:</p>
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<pre>adb sideload blueline-ota_update-2019.07.01.21.zip</pre>
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<p><strong>You do not need to have adb enabled within the OS or the host's ADB key
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whitelisted within the OS to sideload an update to recovery. Recovery mode does not
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trust the attached computer and this can be considered a production feature. Trusting
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a computer with ADB access within the OS is much different and exposes the device to a
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huge amount of attack surface and control by the trusted computer.</strong></p>
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</section>
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</section>
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<section id="usb-peripherals">
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<h2><a href="#usb-peripherals">USB peripherals</a></h2>
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<p>GrapheneOS defaults to ignoring connected USB peripherals when the device is
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already booted and the screen is locked. A USB device already connected at boot
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will still work. The purpose is reducing attack surface for a locked device with
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active login sessions to user profiles to protect data that's not at rest. This
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can be controlled in Settings ➔ Security ➔ USB accessories. The options are:</p>
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<ul>
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<li>Disallow new USB peripherals</li>
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<li>Allow new USB peripherals when unlocked (default)</li>
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<li>Allow new USB peripherals (like stock Android)</li>
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</ul>
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<p>This option has no impact on the device acting as a USB peripheral itself when
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connected to a computer. Android defaults to charge only mode and requires opt-in
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to the device being used for file transfer, USB tethering, MIDI or PTP.</p>
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</section>
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<section id="web-browsing">
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<h2><a href="#web-browsing">Web browsing</a></h2>
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<p>GrapheneOS includes a Vanadium subproject providing privacy and security enhanced
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releases of Chromium. Vanadium is both the user-facing browser included in the OS and
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the provider of the WebView used by other apps to render web content. The WebView is
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the browser engine used by the vast majority of web browsers and nearly all other apps
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embedding web content or using web technologies for other uses.</p>
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<p>Using Vanadium is highly recommended. Bromite is a solid alternative and is the
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only other browser we recommend. Bromite provides integrated ad-blocking and more
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advanced anti-fingerprinting. For now, Vanadium is more focused on security hardening
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and Bromite is more focused on anti-fingerprinting. The projects are collaborating
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together and will likely converge to providing more of the same features. Vanadium
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will be providing content filtering and anti-fingerprinting, but it needs to be done
|
|
in a way that meets the standards of the project, which takes time.</p>
|
|
|
|
<p>Vanadium is designed for use on GrapheneOS and does not duplicate the OS privacy
|
|
and security features such as the hardened malloc implementation. This leads to some
|
|
of the differences from Bromite, such as relying on OS support for encrypted DNS
|
|
rather than enabling Chromium's DNS-over-HTTPS support.</p>
|
|
|
|
<p>Chromium-based browsers like Vanadium and Bromite provide the strongest sandbox
|
|
implementation, leagues ahead of the alternatives. It is much harder to escape from
|
|
the sandbox and it provides much more than acting as a barrier to compromising the
|
|
rest of the OS. Site isolation enforces security boundaries around each site using the
|
|
sandbox by placing each site into an isolated sandbox. It required a huge overhaul of
|
|
the browser since it has to enforce these rules on all the IPC APIs. Site isolation is
|
|
important even without a compromise, due to side channels. Browsers without site
|
|
isolation are very vulnerable to attacks like Spectre. On mobile, due to the lack of
|
|
memory available to apps, there are different modes for site isolation. Vanadium turns
|
|
on strict site isolation, matching Chromium on the desktop. Bromite enables strict
|
|
site isolation on high memory devices, including all the devices that are officially
|
|
supported by GrapheneOS.</p>
|
|
|
|
<p>Chromium has decent exploit mitigations, unlike the available alternatives. This is
|
|
improved upon in Vanadium by enabling further mitigations, including those developed
|
|
upstream but not yet fully enabled due to code size, memory usage or performance. For
|
|
example, it enables type-based CFI like Chromium on the desktop, uses a stronger SSP
|
|
configuration, zero initializes variables by default, etc. Some of the mitigations are
|
|
inherited from the OS itself, which also applies to other browsers, at least if they
|
|
don't do things to break them.</p>
|
|
|
|
<p>We recommend against trying to achieve browser privacy and security through piling
|
|
on browser extensions and modifications. Most privacy features for browsers are
|
|
privacy theater without a clear threat model and these features often reduce privacy
|
|
by aiding fingerprinting and adding more state shared between sites. Every change you
|
|
make results in you standing out from the crowd and generally provides more ways to
|
|
track you. Enumerating badness via content filtering is not a viable approach to
|
|
achieving decent privacy, just as AntiVirus isn't a viable way to achieving decent
|
|
security. These are losing battles, and are at best a stopgap reducing exposure while
|
|
waiting for real privacy and security features.</p>
|
|
|
|
<p>Vanadium will be following the school of thought where hiding the IP address
|
|
through Tor or a trusted VPN shared between many users is the essential baseline, with
|
|
the browser partitioning state based on site and mitigating fingerprinting to avoid
|
|
that being trivially bypassed. The Tor Browser's approach is the only one with any
|
|
real potential, however flawed the current implementation may be. This work is
|
|
currently in a very early stage and it is largely being implemented upstream with the
|
|
strongest available implementation of state partitioning. Chromium is using Network
|
|
Isolation Keys to divide up connection pools, caches and other state based on site and
|
|
this will be the foundation for privacy. Chromium itself aims to prevent tracking
|
|
through mechanisms other than cookies, greatly narrowing the scope downstream work
|
|
needs to cover. Bromite is doing a lot of work in these areas and Vanadium will be
|
|
benefiting from that along with this upstream work. The focus is currently on research
|
|
since we don't see much benefit in deploying bits and pieces of this before everything
|
|
is ready to come together. At the moment, the only browser with any semblance of
|
|
privacy is the Tor Browser but there are many ways to bypass the anti-fingerprinting
|
|
and state partitioning. The Tor Browser's security is weak which makes the privacy
|
|
protection weak. The need to avoid diversity (fingerprinting) creates a monoculture
|
|
for the most interesting targets. This needs to change, especially since Tor itself
|
|
makes people into much more of a target (both locally and by the exit nodes).</p>
|
|
|
|
<p>WebView-based browsers use the hardened Vanadium rendering engine, but they can't
|
|
offer as much privacy and control due to being limited to the capabilities supported
|
|
by the WebView widget. For example, they can't provide a setting for toggling sensors
|
|
access because the feature is fairly new and the WebView WebSettings API doesn't yet
|
|
include support for it as it does for JavaScript, location, cookies, DOM storage and
|
|
other older features. For sensors, the Sensors app permission added by GrapheneOS can
|
|
be toggled off for the browser app as a whole instead. The WebView sandbox also
|
|
currently runs every instance within the same sandbox and doesn't support site
|
|
isolation.</p>
|
|
|
|
<p>Avoid Gecko-based browsers like Firefox as they're currently much more vulnerable
|
|
to exploitation and inherently add a huge amount of attack surface. Gecko doesn't have
|
|
a WebView implementation (GeckoView is not a WebView implementation), so it has to be
|
|
used alongside the Chromium-based WebView rather than instead of Chromium, which means
|
|
having the remote attack surface of two separate browser engines instead of only one.
|
|
Firefox / Gecko also bypass or cripple a fair bit of the upstream and GrapheneOS
|
|
hardening work for apps. Worst of all, Firefox runs as a single process on mobile and
|
|
has no sandbox beyond the OS sandbox. This is despite the fact that Chromium semantic
|
|
sandbox layer on Android is implemented via the OS <code>isolatedProcess</code>
|
|
feature, which is a very easy to use boolean property for app service processes to
|
|
provide strong isolation with only the ability to communicate with the app running
|
|
them via the standard service API. Even in the desktop version, Firefox's sandbox is
|
|
still substantially weaker (especially on Linux, where it can hardly be considered a
|
|
sandbox at all) and lacks support for isolating sites from each other rather than only
|
|
containing content as a whole.</p>
|
|
</section>
|
|
|
|
<section id="camera">
|
|
<h2><a href="#camera">Camera</a></h2>
|
|
|
|
<p>GrapheneOS itself has the same camera capabilities and quality as the stock OS.
|
|
It will match the stock OS when comparing the same app on each OS.</p>
|
|
|
|
<p>The Camera app included in GrapheneOS is very basic and can't take full advantage
|
|
of the hardware. It doesn't offer much in the way of configuration. In the long term,
|
|
it's going to be replaced. In the short term, there are other apps available providing
|
|
more capabilities and better support for taking advantage of the hardware.</p>
|
|
|
|
<p>The Pixel 3 (but not the Pixel 3a) and Pixel 4 (but not the Pixel 4a) have a
|
|
Pixel Visual Core / Pixel Neural Core providing a hardware-based implementation of
|
|
HDR+. HDR+ captures many images and intelligently merges data across them, taking
|
|
into account motion, etc. It substantially improves the quality of images,
|
|
especially in low light. This is used transparently for third party apps that are
|
|
compatible with it, and there isn't an explicit switch to turn it on or off for
|
|
most of them. An example of a compatible app is Open Camera's default
|
|
configuration, or Open Camera with the Camera 2 API and other settings (including
|
|
the the various knobs / toggles outside of the settings menu) left alone. In
|
|
general, HDR+ will work transparently in most apps as long as they keep things
|
|
simple and use a good minimalist approach to taking pictures. It should work
|
|
transparently in most messaging apps, etc. with internal support for taking
|
|
pictures.</p>
|
|
|
|
<p>In addition to supporting HDR+ via the Pixel Visual Core, or similar features on
|
|
other devices with the same constraints, Open Camera offers advanced configuration and
|
|
various advanced features. Make sure to enable the Camera 2 API in the settings, which
|
|
should be the default, but the app doesn't have a great user interface / user
|
|
experience. You probably don't want to use the traditional HDR feature in the app.
|
|
That's not HDR+, but rather captures 3 images and merges them in a way that isn't at
|
|
all intelligent and causes a lot of blur and distortion. The HDR+ implementation can
|
|
actually benefit from the camera not being completely steady as it's smart enough to
|
|
match up the picture and it provides it with more data vs. a traditional HDR
|
|
implementation where it essentially doesn't work without a tripod and is not really at
|
|
all useful on a phone unless you actually have that for it.</p>
|
|
</section>
|
|
|
|
<section id="exec-spawning">
|
|
<h2><a href="#exec-spawning">Exec spawning</a></h2>
|
|
|
|
<p>GrapheneOS creates fresh processes (via exec) when spawning applications instead of
|
|
using the traditional Zygote spawning model. This improves privacy and security at the
|
|
expense of higher cold start app spawning time and higher initial memory usage. It
|
|
doesn't impact runtime performance beyond the initial spawning time. It adds somewhere
|
|
in the ballpark of 100ms to app spawning time on the flagship devices and is only very
|
|
noticeable on lower-end devices with a weaker CPU and slower storage. The spawning
|
|
time impact only applies when the app doesn't already have an app process and the OS
|
|
will try to keep app processes cached in the background until memory pressure forces
|
|
it to start killing them.</p>
|
|
|
|
<p>In the typical Zygote model, a template app process is created during boot and
|
|
every app is spawned as a clone of it. This results in every app sharing the same
|
|
initial memory content and layout, including sharing secrets that are meant to be
|
|
randomized for each process. It saves time by reusing the initialization work. The
|
|
initial memory usage is reduced due to copy-on-write semantics resulting in memory
|
|
written only during initialization being shared between app processes.</p>
|
|
|
|
<p>The Zygote model weakens the security provided by features based on random secrets
|
|
including Address Space Layout Randomization (ASLR), stack canaries, heap canaries,
|
|
randomized heap layout and memory tags. It cripples these security features since
|
|
every app has the values for every other app and the values don't change for fresh app
|
|
processes until reboot. Much of the OS itself is implemented via non-user-facing apps
|
|
with privileges reserved for OS components. The Zygote template is reused across user
|
|
profiles, so it also provides a temporary set of device identifiers across profiles
|
|
for each boot via the shared randomized values.</p>
|
|
</section>
|
|
|
|
<section id="bugs-uncovered-by-security-features">
|
|
<h2><a href="#bugs-uncovered-by-security-features">Bugs uncovered by security features</a></h2>
|
|
|
|
<p>GrapheneOS substantially expands the standard mitigations for memory corruption
|
|
vulnerabilities. Some of these features are designed to directly catch the memory
|
|
corruption bugs either via an explicit check or memory protection and abort the
|
|
program in order to prevent them from being exploited. Other features mitigate issues
|
|
a bit less directly such as zeroing data immediately upon free, isolated memory
|
|
regions, heap randomization, etc. and can also lead to latent memory corruption bugs
|
|
crashing instead of the program continuing onwards with corrupted memory. This means
|
|
that many latent memory corruption bugs in apps are caught along with some in the OS
|
|
itself. These bugs are not caused by GrapheneOS, but rather already existed and are
|
|
uncovered by the features. The features are aimed at preventing or hindering exploits,
|
|
not finding bugs, but they do that as part of doing their actual job.</p>
|
|
|
|
<p>Similarly, some of the other privacy and security improvements reduce the access
|
|
available to applications and they may crash. Some of these features are always
|
|
enabled under the hood, while others like the Network and Sensors toggles are
|
|
controlled by users via opt-in or opt-out toggles. Apps may not handle having access
|
|
taken away like this, although it generally doesn't cause any issues as it's all
|
|
designed to be friendly to apps and fully compatible rather than killing the
|
|
application when it violates the rules.</p>
|
|
|
|
<p>If you run into an application aborting, try to come up with a process for
|
|
reproducing the issue and then capture a bug report via the 'Take bug report'
|
|
feature in Developer options. Report an issue to <a
|
|
href="https://github.com/GrapheneOS/os-issue-tracker/issues">the GrapheneOS OS
|
|
issue tracker</a> and email the bug report capture zip to contact@grapheneos.org
|
|
with the issue tracker number in the subject like "Bug report capture for issue
|
|
#104". The bug report capture includes plain text 'tombstones' with logs,
|
|
tracebacks, address space layout, register content and a tiny bit of context
|
|
from memory from areas that are interesting for debugging. This may contain
|
|
some sensitive data. Feel free to provide only the tombstone for the relevant
|
|
crash and filter out information you don't want to send. However, it will be
|
|
more difficult to debug if you provide less of the information. If the app
|
|
doesn't work with sensitive information, just send the whole tombstone.</p>
|
|
</section>
|
|
|
|
<section id="wifi-privacy">
|
|
<h2><a href="#wifi-privacy">Wi-Fi privacy</a></h2>
|
|
|
|
<p>Wi-Fi on GrapheneOS is very privacy-friendly and is essentially anonymous as long
|
|
as apps do not leak uniquely identifying information to the network. GrapheneOS avoids
|
|
allowing itself to be fingerprinted as GrapheneOS, other than connections which are
|
|
documented (see the FAQ) and can be easily disabled or forced through a VPN
|
|
service.</p>
|
|
|
|
<section id="wifi-privacy-scanning">
|
|
<h3><a href="#wifi-privacy-scanning">Scanning</a></h3>
|
|
|
|
<p>MAC randomization is always performed for Wi-Fi scanning. Pixel
|
|
phones have firmware support for scanning MAC randomization going
|
|
<a href="https://android-developers.googleblog.com/2017/04/changes-to-device-identifiers-in.html">significantly beyond a naive implementation</a>.
|
|
On many other devices, there are identifiers exposed by Wi-Fi scanning beyond the MAC
|
|
address such as the packet sequence number and assorted identifying information in the
|
|
probe requests.</p>
|
|
|
|
<p>Avoid using hidden APs (i.e. APs not broadcasting their SSID) since all
|
|
known hidden SSIDs end up being broadcast as part of scanning for networks to
|
|
find them again. SSIDs are not broadcast for standard non-hidden APs. Hidden
|
|
APs are only hidden when no devices are connected. It makes little sense as a
|
|
privacy feature, especially for a non-mobile AP where knowing the AP exists
|
|
can't be used for tracking it since it doesn't move. The feature reduces your
|
|
privacy rather than increasing it. If you need to use a hidden AP, make sure
|
|
to delete the saved network afterwards.</p>
|
|
|
|
<p>Wi-Fi and Bluetooth scanning for improving location detection are disabled by
|
|
default, unlike the stock OS. These can be toggled in Settings ➔ Location ➔ Wi-Fi and
|
|
Bluetooth scanning. These features enable scanning even when Wi-Fi or Bluetooth is
|
|
disabled, so these need to be kept disabled to fully disable the radios when Wi-Fi and
|
|
Bluetooth are disabled. GrapheneOS doesn't yet have an implementation of a coarse
|
|
location service to supplement GPS location, so enabling these options doesn't
|
|
actually do anything at the moment. Implementing a supplementary location service is
|
|
planned but we need a robust, secure and private implementation via a local database.
|
|
The initial focus will likely be a cell phone tower database, so these features still
|
|
wouldn't be relevant.</p>
|
|
</section>
|
|
|
|
<section id="wifi-privacy-associated">
|
|
<h3><a href="#wifi-privacy-associated">Associated with an Access Point (AP)</a></h3>
|
|
|
|
<p>Associated MAC randomization is performed by default. This can be controlled
|
|
per-network with Settings ➔ Network & Internet ➔ Wi-Fi ➔ <network> ➔
|
|
Advanced ➔ Privacy.</p>
|
|
|
|
<p>In the stock OS, the default is to use a unique persistent random MAC address for
|
|
each network. It has 2 options available: "Use randomized MAC (default)" and "Use
|
|
device MAC". In GrapheneOS, the default is generating a new random MAC address when
|
|
connecting to a network. It has 3 options available: "Use fully randomized MAC
|
|
(default)", "Use per-network randomized MAC" and "Use device MAC".</p>
|
|
|
|
<p>The DHCP client uses the anonymity profile rather than sending a hostname
|
|
so it doesn't compromise the privacy offered by MAC randomization. When the
|
|
per-connection MAC randomization added by GrapheneOS is being used, DHCP
|
|
client state is flushed before reconnecting to a network to avoid revealing
|
|
that it's likely the same device as before.</p>
|
|
|
|
<p>GrapheneOS also disables support for stable link-local IPv6 addresses, since these
|
|
have the potential to be used as identifiers. It's more sensible to use typical
|
|
link-local address generation based on the (randomized) MAC address since link-local
|
|
devices have access to both. As of Android 11, Android only uses stable link-local
|
|
privacy addresses when MAC randomization is disabled, so we no longer need to disable
|
|
the feature.</p>
|
|
</section>
|
|
</section>
|
|
|
|
<section id="lte-only-mode">
|
|
<h2><a href="#lte-only-mode">LTE-only mode</a></h2>
|
|
|
|
<p>If you have a reliable LTE connection from your carrier, you can reduce attack
|
|
surface by disabling 2G / 3G connectivity in Settings ➔ Network & Internet ➔
|
|
Mobile network ➔ Preferred network type. Traditional voice calls will only work in
|
|
the LTE-only mode if you have either an LTE connection and VoLTE (Voice over LTE)
|
|
support or a Wi-Fi connection and VoWi-Fi (Voice over Wi-Fi) support. VoLTE /
|
|
VoWi-Fi works on GrapheneOS for most carriers unless they restrict it to carrier
|
|
phones. US carriers other than T-Mobile tend to be missing these features due to
|
|
us not including their proprietary apps.</p>
|
|
|
|
<p>This feature is not intended to improve the confidentiality of traditional calls and
|
|
texts, but it might somewhat raise the bar for some forms of interception. It's not a
|
|
substitute for end-to-end encrypted calls / texts or even transport layer encryption.
|
|
LTE does provide basic network authentication / encryption, but it's for the network
|
|
itself. The intention of the LTE-only feature is only hardening against remote
|
|
exploitation by disabling an enormous amount of legacy code.</p>
|
|
</section>
|
|
|
|
<section id="sandboxed-play-services">
|
|
<h2><a href="#sandboxed-play-services">Sandboxed Play services (experimental)</a></h2>
|
|
|
|
<p>GrapheneOS has experimental support for installing the official releases of
|
|
com.android.vending (Google Play Store), com.google.android.gms (Google Play
|
|
services), com.google.android.gsf (Google Services Framework) as regular sandboxed
|
|
apps in a specific profile. These receive no special privileges and the OS itself
|
|
doesn't use them for anything. They run as unprivileged, sandboxed apps like any
|
|
others. GrapheneOS simply provides fallback code teaching them how to run without
|
|
any of the special privileged permissions and SELinux policy they depend on
|
|
having. Even within the same profile, apps not explicitly choosing to use Google
|
|
services won't use them because the OS doesn't integrate support for it or use it
|
|
as the backend for APIs in the OS like the stock OS.</p>
|
|
|
|
<p>The core functionality and APIs are almost entirely supported already since
|
|
GrapheneOS largely only has to coerce these apps into continuing to run without
|
|
being able to use any of the usual invasive OS integration. A compatibility layer
|
|
is also provided to support dynamically downloaded/loaded modules (dynamite
|
|
modules).</p>
|
|
|
|
<p>You can obtain the apps from the apps.grapheneos.org repository. We don't yet
|
|
have a client app for our repository so you'll need to install the APKs manually.
|
|
The Play Store APK has multiple split APKs which need to be installed together
|
|
rather than separately, so you'll need to use an app providing split APK
|
|
installation support. Once we have a client app for our repository, you'll be able
|
|
to install these and receive automatic updates through the app.</p>
|
|
|
|
<p>Install com.google.android.gsf, then com.google.android.gms and finally
|
|
com.android.vending via a split APK installer. Make sure to install all 3 in the
|
|
correct order and don't skip installing the Play Store since it provides services
|
|
used by apps depending on Play.</p>
|
|
|
|
<ul>
|
|
<li><a href="https://apps.grapheneos.org/packages/com.google.android.gsf/">com.google.android.gsf</a></li>
|
|
<li><a href="https://apps.grapheneos.org/packages/com.google.android.gms/">com.google.android.gms</a></li>
|
|
<li><a href="https://apps.grapheneos.org/packages/com.android.vending/">com.android.vending</a></li>
|
|
</ul>
|
|
|
|
<p>You should give a battery optimization exception to Google Play services for
|
|
features like push notifications to work properly in the background. It isn't
|
|
needed for the other 2 apps.</p>
|
|
|
|
<p>After installing the apps, you should open the Play Store and press sign in to
|
|
trigger initialization. Signing into an account is optional and it will work fine
|
|
without it, but you do need to get it initialized and this is currently the best
|
|
way to mimic the initialization done by the stock OS setup wizard.</p>
|
|
|
|
<section id="sandboxed-play-services-limitations">
|
|
<h3><a href="#sandboxed-play-services-limitations">Limitations</a></h3>
|
|
|
|
<p>There's currently a known issue with apps not being able to see that Play
|
|
services is installed in the profile in some cases. This is being worked on
|
|
and it should be resolved soon.</p>
|
|
|
|
<p>Functionality depending on privileged access such as special access to
|
|
hardware isn't available. We would need to implement compatibility layers
|
|
teaching it how to function as a regular app. This currently isn't within the
|
|
scope of the project beyond the existing support for dynamite modules and
|
|
partially implemented support for Play Store app installation/updates.</p>
|
|
|
|
<p>The Play Store app cannot install and update apps as it normally would
|
|
since it depends entirely on privileged permissions for unattended app
|
|
installation, updates and removal. GrapheneOS includes a partial
|
|
implementation of fallback code to get this working. It currently isn't fully
|
|
wired up and leads to the Play Store stalling and needing to be force stopped.
|
|
For the time being, it's easier to use the alternative Aurora Store frontend
|
|
to the Play Store.</p>
|
|
|
|
<p>Play Store feature delivery isn't currently supported, but this isn't
|
|
broadly used by current generation apps aside from large games.</p>
|
|
|
|
<p>Since there's no OS integration beyond fallback code to make it function
|
|
without any special privileges, there isn't a way to launch the settings
|
|
activity. We'll need to make a tiny app providing a way to launch it.</p>
|
|
</section>
|
|
</section>
|
|
</main>
|
|
<footer>
|
|
<a href="/"><img src="/mask-icon.svg" width="512" height="512" alt=""/>GrapheneOS</a>
|
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<ul id="social">
|
|
<li><a href="https://twitter.com/GrapheneOS">Twitter</a></li>
|
|
<li><a href="https://github.com/GrapheneOS">GitHub</a></li>
|
|
<li><a href="https://reddit.com/r/GrapheneOS">Reddit</a></li>
|
|
<li><a href="https://www.linkedin.com/company/grapheneos/">LinkedIn</a></li>
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</ul>
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</footer>
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