Features overview

GrapheneOS is a private and secure mobile operating system with great functionality and usability. It starts from the strong baseline of the Android Open Source Project (AOSP) and takes great care to avoid increasing attack surface or hurting the strong security model. GrapheneOS makes substantial improvements to both privacy and security through many carefully designed features built to function against real adversaries. The project cares a lot about usability and app compatibility so those are taken into account for all of our features.

GrapheneOS is focused on substance rather than branding and marketing. It doesn't take the typical approach of piling on a bunch of insecure features depending on the adversaries not knowing about them and regressing actual privacy/security. It's a very technical project building privacy and security into the OS rather than including assorted unhelpful frills or bundling subjective third party apps choices.

GrapheneOS is also hard at work on filling in gaps from not bundling Google apps and services into the OS. We aren't against users using Google services but it doesn't belong integrated into the OS in an invasive way. GrapheneOS won't take the shortcut of simply bundling a very incomplete and poorly secured third party reimplementation of Google services into the OS. That wouldn't ever be something users could rely upon. It will also always be chasing a moving target while offering poorer security than the real thing if the focus is on simply getting things working without great care for doing it robustly and securely.

This page provides an overview of currently implemented features differentiating GrapheneOS from AOSP. It doesn't document our many historical features that are no longer included for one reason or another. Many of our features were implemented in AOSP, Linux, LLVM and other projects GrapheneOS is based on and those aren't listed here. In many cases, we've been involved in getting those features implemented in core infrastructure projects.

GrapheneOS

These are the features of GrapheneOS beyond what's provided by version 12.1 of the Android Open Source Project. It only covers our improvements to AOSP and not baseline features. This section doesn't list features like the standard app sandbox, verified boot, exploit mitigations (ASLR, SSP, Shadow Call Stack, Control Flow Integrity, etc.), permission system (foreground-only and one-time permission grants, scoped file access control, etc.) and so on but rather only our improvements to modern Android. We plan on providing a separate page listing the improvements we've contributed to Android since those features aren't listed here despite being a substantial portion of our overall historical work.

Defending against exploitation of unknown vulnerabilities

GrapheneOS is heavily focused on protecting users against attackers exploiting unknown (0 day) vulnerabilities. Patching vulnerabilities doesn't protect users before the vulnerability is known to the vendor and has a patch developed and shipped.

Unknown (0 day) vulnerabilities are much more widely used than most realize to exploit users not just in targeted attacks but in broad deployments. Project Zero maintains a spreadsheet tracking zero day exploitation detected in the wild. This is only a peek into what's happening since it only documents cases where the attackers were caught exploiting users, often because the attacks are not targeted but rather deployed on public websites, etc.

The first line of defense is attack surface reduction. Removing unnecessary code or exposed attack surface eliminates many vulnerabilities completely. GrapheneOS avoids removing any useful functionality for end users, but we can still disable lots of functionality by default and require that users opt-in to using it to eliminate it for most of them. An example we landed upstream in Android is disallowing using the kernel's profiling support by default, since it was and still is a major source of Linux kernel vulnerabilities. Profiling is now only exposed to apps for developers who enable developer tools, enable the Android Debug Bridge (ADB) and then use profiling tools via ADB. It's also only enabled until the next boot. This isn't listed below since it's one of the features we got implemented in Android itself.

The next line of defense is preventing an attacker from exploiting a vulnerability, either by making it impossible, unreliable or at least meaningfully harder to develop. The vast majority of vulnerabilities are well understood classes of bugs and exploitation can be prevented by avoiding the bugs via languages/tooling or preventing exploitation with strong exploit mitigations. In many cases, vulnerability classes can be completely wiped out while in many others they can at least be made meaningfully harder to exploit. Android does a lot of work in this area and GrapheneOS has helped to advance this in Android and the Linux kernel. It takes an enormous amount of resources to develop fundamental fixes for these problems and there's often a high performance, memory or compatibility cost to deploying them. Mainstream operating systems usually don't prioritize security over other areas. GrapheneOS is willing to go further and we offer toggles for users to choose the compromises they prefer instead of forcing it on them. In the meantime, weaker less complete exploit mitigations can still provide meaningful barriers against attacks as long as they're developed with a clear threat model. GrapheneOS is heavily invested in many areas of developing these protections: developing/deploying memory safe languages / libraries, static/dynamic analysis tooling and many kinds of mitigations.

The final line of defense is containment through sandboxing at various levels: fine-grained sandboxes around a specific context like per site browser renderers, sandboxes around a specific component like Android's media codec sandbox and app / workspace sandboxes like the Android app sandbox used to sandbox each app which is also the basis for user/work profiles. GrapheneOS improves all of these sandboxes through fortifying the kernel and other base OS components along with improving the sandboxing policies.

Preventing an attacker from persisting their control of a component or the OS / firmware through verified boot and avoiding trust in persistent state also helps to mitigate the damage after a compromise has occurred.

Remote code execution vulnerabilities are the most serious and allow an attacker to gain a foothold on device or even substantial control over it remotely. Local code execution vulnerabilities allow breaking out of a sandbox including the app sandbox or browser renderer sandbox after either compromising an app / browser renderer remotely, compromising an app's supply chain or getting the user to install a malicious app. Many other kinds of vulnerabilities exist but most of what we're protecting against falls into these 2 broad categories.

The vast majority of local and remote code execution vulnerabilities are memory corruption bugs caused by memory unsafe languages or rare low-level unsafe code in an otherwise memory safe language. Most of the remaining issues are caused by dynamic code execution/loading features. Our main focus is on preventing or raising the difficult of exploiting memory corruption bugs followed by restricting dynamic code execution both to make escalation from a memory corruption bug harder and to directly mitigate bugs caused by dynamic code loading/generation/execution such as a JIT compiler bug or a plugin loading vulnerability.

Attack surface reduction

  • Greatly reduced remote, local and proximity-based attack surface by stripping out unnecessary code, making more features optional and disabling optional features by default (NFC, Bluetooth, etc.), when the screen is locked (connecting new USB peripherals, camera access) and optionally after a timeout (Bluetooth, Wi-Fi)
  • Option to disable native debugging (ptrace) to reduce local attack surface (still enabled by default for compatibility)

Exploit mitigations

  • Hardened app runtime
  • Secure application spawning system avoiding sharing address space layout and other secrets across applications
  • Hardened libc providing defenses against the most common classes of vulnerabilities (memory corruption)
  • Our own hardened malloc (memory allocator) leveraging modern hardware capabilities to provide substantial defenses against the most common classes of vulnerabilities (heap memory corruption) along with reducing the lifetime of sensitive data in memory. The hardened_malloc README has extensive documentation on it. The hardened_malloc project is portable to other Linux-based operating systems and is being adopted by other security-focused operating systems like Whonix. Our allocator also heavily influenced the design of the next-generation musl malloc implementation which offers substantially better security than musl's previous malloc while still having minimal memory usage and code size.
    • Fully out-of-line metadata with protection from corruption, ruling out traditional allocator exploitation
    • Separate memory regions for metadata, large allocations and each slab allocation size class with high entropy random bases and no address space reuse between the different regions
    • Deterministic detection of any invalid free
    • Zero-on-free with detection of write-after-free via checking that memory is still zeroed before handing it out again
    • Delayed reuse of address space and memory allocations through the combination of deterministic and randomized quarantines to mitigate use-after-free vulnerabilities
    • Fine-grained randomization
    • Aggressive consistency checks
    • Memory protected guard regions around allocations larger than 16k with randomization of guard region sizes for 128k and above
    • Allocations smaller than 16k have guard regions around each of the slabs containing allocations (for example, 16 byte allocations are in 4096 byte slabs with 4096 byte guard regions before and after)
    • Random canaries with a leading zero are added to these smaller allocations to block C string overflows, absorb small overflows and detect linear overflows or other heap corruption when the canary value is checked (primarily on free)
  • Hardened compiler toolchain
  • Hardened kernel
    • Full LTO (Link Time Optimization) is used instead of ThinLTO to provide improved Control Flow Integrity (CFI) granularity.
    • 4-level page tables are enabled on arm64 to provide a much larger address space (48-bit instead of 39-bit) with significantly higher entropy Address Space Layout Randomization (33-bit instead of 24-bit).
    • Random canaries with a leading zero are added to the kernel heap (slub) to block C string overflows, absorb small overflows and detect linear overflows or other heap corruption when the canary value is checked (on free, copies to/from userspace, etc.).
    • Memory is wiped (zeroed) as soon as it's released in both the low-level kernel page allocator and higher level kernel heap allocator (slub). This substantially reduces the lifetime of sensitive data in memory, mitigates use-after-free vulnerabilities and makes most uninitialized data usage vulnerabilities harmless. Without our changes, memory that's released retains data indefinitely until the memory is handed out for other uses and gets partially or fully overwritten by new data.
    • Kernel stack allocations are zeroed to make most uninitialized data usage vulnerabilities harmless.
    • Assorted attack surface reduction through disabling features or setting up infrastructure to dynamically enable/disable them only as needed (perf, ptrace).
    • Assorted upstream hardening features are enabled, including many which we played a part in developing and landing upstream as part of our linux-hardened project (which we intend to revive as a more active project again).
  • Prevention of dynamic native code execution in-memory or via the filesystem for the base OS without going via the package manager, etc.
  • Filesystem access hardening

Improved sandboxing

GrapheneOS improves the app sandbox through hardening SELinux policy and seccomp-bpf policy along with all the hardening to components like kernel implementing the app sandbox and providing a path for the attacker to escape it if they can exploit those components. We primarily focus on the app sandbox, but we also improve the other sandboxes including making direct improvements to the web browser renderer sandbox used for both the default browser and WebView rendering engine provided by the OS and used by a huge number of other apps from dedicated browsers to messaging apps.

Anti-persistence / detection

  • Enhanced verified boot with better security properties and reduced attack surface
  • Enhanced hardware-based attestation with more precise version information
  • Hardware-based security verification and monitoring via our Auditor app and attestation service

More complete patching

GrapheneOS includes fixes for many vulnerabilities not yet fixed in Android. On modern devices with Generic Kernel Image (GKI) support, we update the kernel to the latest stable GKI release many months before the stock OS gets the update. This means we're shipping hundreds of fixes not included in the stock OS including many security fixes. We also backport more fixes on top of this for the kernel and for other components too.

We often find new vulnerabilities ourselves and report them upstream. We've reported dozens of vulnerabilities for both the generic Android codebase and also for Pixels specifically. We also often find missed patches which were supposed to be included but were missed, especially when there are device specific components with partially shared but separate codebases for different devices.

Our overall approach is to focus on systemic privacy and security improvements but fixing individual vulnerabilities is still very important.

Sandboxed Google Play

GrapheneOS has a compatibility layer providing the option to install and use the official releases of Google Play in the standard app sandbox. Google Play receives absolutely no special access or privileges on GrapheneOS as opposed to bypassing the app sandbox and receiving a massive amount of highly privileged access. Instead, the compatibility layer teaches it how to work within the full app sandbox. It also isn't used as a backend for the OS services as it would be elsewhere since GrapheneOS doesn't use Google Play even when it's installed.

Since the Google Play apps are simply regular apps on GrapheneOS, you install them within a specific user or work profile and they're only available within that profile. Only apps within the same profile can use it and they need to explicitly choose to use it. It works the same way as any other app and has no special capabilities. As with any other app, it can't access data of other apps and requires explicit user consent to gain access to profile data or the standard permissions. Apps within the same profile can communicate with mutual consent and it's no different for sandboxed Google Play.

Sandboxed Google Play is close to being fully functional and provides near complete compatibility with the app ecosystem depending on Google Play. Only a small subset of privileged functionality which we haven't yet ported to different approaches with our compatibility layer is unavailable. Some functionality is inherently privileged and can't be provided as part of the compatibility layer.

The vast majority of Play services functionality works perfectly including dynamically downloaded / updated modules (dynamite modules) and functionality provided by modular app components such as Google Play Games. By default, location requests are rerouted to a partial implementation of the Play geolocation service provided by GrapheneOS. You can disable rerouting and use the full Play services geolocation service instead.

Our compatibility layer includes full support for the Play Store. Play Store services are fully available including in-app purchases, Play Asset Delivery, Play Feature Delivery and app / content license checks. It can install, update and uninstall apps with the standard approach requiring that the user authorizes it as an app source and consents to each action. It will use the standard Android 12+ unattended update feature to do automatic updates for apps where it was the last installer. Unattended updates by sandboxed apps are throttled and it can hit the limit when installing batches of updates and request consent. We plan to improve this in the future by teaching it to try an unattended update again after a short wait.

See the usage guide section on sandboxed Google Play for instructions.

Network permission toggle

GrapheneOS adds a Network permission toggle for disallowing both direct and indirect access to any of the available networks. The device-local network (localhost) is also guarded by this permission, which is important for preventing apps from using it to communicate between profiles. Unlike a firewall-based implementation, the Network permission toggle prevents apps from using the network via APIs provided by the OS or other apps in the same profile as long as they're marked appropriately.

The standard INTERNET permission used as the basis for the Network permission toggle is enhanced with a second layer of enforcement and proper support for granting/revoking it on a per-profile basis.

Sensors permission toggle

Sensors permission toggle: disallow access to all other sensors not covered by existing Android permissions (Camera, Microphone, Body Sensors, Activity Recognition) including an accelerometer, gyroscope, compass, barometer, thermometer and any other sensors present on a given device. To avoid breaking compatibility with Android apps, the added permission is enabled by default.

Storage Scopes

GrapheneOS provides Storage Scopes as a fully compatible alternative to the standard Android storage permissions. Instead of granting storage permissions, users can enable Storage Scopes to grant the requested permissions in a highly restricted mode where the app can create files/directories in the user's home directory but can only access the files it has created itself. Users can then optionally add files and directories as storage scopes to permit the app to access files created by other apps.

For more details, see the usage guide section on storage access.

Broad carrier support without invasive carrier access

GrapheneOS has much broader carrier support than AOSP and mostly matches the stock OS on Pixels without making the same sacrifices. We convert their APN, carrier configuration, MMS and visual voicemail databases to the formats used by AOSP with our carriersettings project and other scripts. We strip out anti-user configuration requiring provisioning for tethering, forbidding disabling 2G, etc. We don't include the invasive carrier specific apps and support for Open Mobile Alliance Device Management (OMA DM) so we also strip out configuration depending on those.

See our usage guide section on carrier functionality for more details.

LTE-only mode

LTE-only mode to reduce cellular radio attack surface by disabling enormous amounts of both legacy code (2G, 3G) and bleeding edge code (5G).

Wi-Fi privacy

GrapheneOS supports per-connection MAC randomization and enables it by default. This is a more private approach than the standard persistent per-network random MAC used by modern Android.

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.

GrapheneOS also applies fixes for serious flaws with the Linux kernel IPv6 privacy address implementation which allow using it as an identifier not just for connections to the same network but also across different networks. We don't need to apply these changes for the Pixel 6 and later since this was fixed in the Linux kernel upstream, but hasn't been backported to earlier kernel LTS branches so we still need to take care of it there.

See our usage guide section on Wi-Fi privacy for more general information rather than only our improvements to the standard Wi-Fi privacy approach.

Private screenshots

GrapheneOS disables the inclusion of sensitive metadata in screenshots.

On Android, each screenshot includes an EXIF Software tag with detailed OS build/version information (android.os.Build.DISPLAY). It's the same value shown at Settings ➔ About device ➔ Build number. This leaks the OS, OS version and also usually the device family/model since builds are usually specific to a family of devices. GrapheneOS completely disables this tag.

On Android, each screenshot also includes EXIF tags with the local date, time and timezone offset. GrapheneOS disables this by default in order to avoid leaking the time and quasi-location information through metadata that isn't visible to the user. The date and time are already included in the file name of the screenshot which is fully visible to the user and can be easily modified by them without a third party tool. GrapheneOS includes a toggle for turning this metadata back on in Settings ➔ Privacy since some users may find it to be useful.

Closed device identifier leaks

GrapheneOS fixes several prominent device identifier leaks bypassing Android's intention of apps not being able to uniquely identify a device. See our FAQ sections on hardware identifiers and non-hardware identifiers for more general information.

Our secure application spawning system primarily exists to significantly improve protection against exploitation. However, it also improves privacy. On a device without our secure application spawning system, the secrets used for probabilistic exploit mitigations such as ASLR are usable as device identifiers persisting until reboot. This is an easy way to identify the device from apps in different profiles. It's a minor bonus of the feature and there are still plenty of side channels to identify devices across apps, but it fixes most of the known direct identifier leaks.

We also eliminate several holes in preventing apps from accessing hardware identifiers including tightening up the restrictions for apps targeting legacy Android platform versions.

PIN scrambling

GrapheneOS adds a toggle for enabling PIN scrambling to raise the difficulty of figuring out the PIN being entered by a user either due to physical proximity or a side channel.

Privacy by default

GrapheneOS doesn't include or use Google apps and services by default and avoids including any other apps/services not aligned with our privacy and security focus. Google apps and services can be used on GrapheneOS as regular sandboxed apps without any special access or privileges through our sandboxed Google Play feature, but we don't include those apps by default to give users an explicit choice on whether they want to use those apps and which profiles they want to use it in.

We change the default settings to prefer privacy over small conveniences: personalized keyboard suggestions based on gathering input history are disabled by default, sensitive notifications are hidden on the lockscreen by default and passwords are hidden during entry by default.

Some of our changes for attack surface reduction can also improve privacy by default by not exposing unnecessary radios, etc. by default and avoiding the impact of potential privacy bugs with the hardware.

By default, we also use GrapheneOS servers for the following services instead of Google servers:

  • Connectivity checks
  • Attestation key provisioning
  • GNSS almanac downloads (PSDS) on 6th generation Pixels
  • Network time

We provide a toggle to switch back to Google's servers for connectivity checks, attestation key provisioning and GNSS almanac downloads along with adding proper support for disabling network time connections. This combines with other toggles to allow making a GrapheneOS device appear to be an AOSP device. This is only particularly important for connectivity checks since the other connections get routed through a VPN which is needed to blend in on a local network in practice.

See our default connections FAQ entry for much more detailed information.

Supports longer passwords

GrapheneOS supports setting longer passwords by default: 64 characters instead of 16 characters. This avoids the need to use a device manager to enable this functionality.

This feature allows users to make use of diceware passwords if they don't want to depend on the security of the secure element which provides very aggressive throttling and offers a high level of security even for a random 6 digit PIN.

Auto reboot

Option to enable automatically rebooting the device when no profile has been unlocked for the configured time period to put the device fully at rest again.

More secure fingerprint unlock

GrapheneOS improves the security of the fingerprint unlock feature by only permitting 5 total attempts rather than implementing a 30 second delay between every 5 failed attempts with a total of 20 attempts. This doesn't just reduce the number of potential attempts but also makes it easy to disable fingerprint unlock by intentionally failing to unlock 5 times with a different finger.

GrapheneOS also adds support for using the fingerprint scanner only for authentication in apps and unlocking hardware keystore keys by toggling off support for unlocking. This feature already existed for the standard Android face unlock feature.

Improved user profiles

Android's user profiles are isolated workspaces with their own instances of apps, app data and profile data (contacts, media store, home directory, etc.). Apps can't see the apps in other user profiles and can only communicate with apps within the same user profile (with mutual consent with the other app). Each user profile has their own encryption keys based on their lock method. They're a great fit for GrapheneOS with a lot of room for improvement.

GrapheneOS provides improvements to user profile functionality and is working on further improvements to make switching between them and monitoring other profiles much more convenient.

More user profiles

GrapheneOS raises the limit on the number of secondary user profiles to 16 (15 + guest) instead of only 4 (3 + guest) to make this feature much more flexible.

End session

GrapheneOS also enables support for logging out of user profiles without needing a device manager controlling the device to use this feature. Logging out makes profiles inactive so none of the apps installed in them can run. It also purges the disk encryption keys from memory and hardware registers, putting the user profile back at rest.

Disabling app installation

GrapheneOS adds a toggle to the user management settings for disabling secondary user app installation. You can install the apps you want to be usable in a secondary user and then disable the ability to install more apps as that user in the Owner profile. Android supports this as a standard device management feature but doesn't make it available to a user who owns their own device.

Notification forwarding

GrapheneOS supports forwarding notifications from users running in the background to the currently active user. Forwarding notifications to other users is disabled by default and can be enabled within each user profile where forwarding to the active profile is wanted. Notifications forwarded from other profiles are displayed by default in a standard local notification channel.

GrapheneOS app repository

GrapheneOS includes our own security, minimalism and usability focused app repository client for using our first party app repository. Our app repository is currently used to distribute our own apps and a mirror of Google Play for the sandboxed Google Play feature. In the future, it will be used to distribute first-party GrapheneOS builds of externally developed open source apps with hardening applied.

Vanadium: hardened WebView and default browser

GrapheneOS includes our Vanadium browser as WebView implementation provided by the OS and our default browser. Vanadium is a hardened variant of Chromium providing enhanced privacy and security, similar to how GrapheneOS compares to AOSP. The Vanadium browser currently doesn't add many features but there are a lot of enhancements planned in the long term.

More details are available in the web browsing section of our usage guide.

Auditor app and attestation service

Our Auditor app and attestation service provide strong hardware-based verification of the authenticity and integrity of the firmware/software on the device. A strong pairing-based approach is used which also provides verification of the device's identity based on the hardware backed key generated for each pairing. Software-based checks are layered on top with trust securely chained from the hardware. For more details, see the about page and tutorial.

GrapheneOS Camera

GrapheneOS Camera is a modern camera app with a great user interface and a focus on privacy and security. More details are available the camera section of our usage guide.

GrapheneOS PDF Viewer

GrapheneOS PDF Viewer is sandboxed, hardened PDF viewer using HiDPI rendering with pinch to zoom, text selection, etc.

Encrypted backups

Encrypted backups via integration of the Seedvault app with support for local backups and any cloud storage provider with a storage provider app.

Seedvault was created by a GrapheneOS community member for inclusion in our operating system. We plan on replacing it with a new implementation since the project has been taken over by another group of people not sharing our goals or approach. For now, this is the best available option so we're including it to give people encrypted backup support. We've made several security fixes to work around upstream issues with the project.

Location data access indicator

GrapheneOS enables the privacy indicator for location data access in addition to the standard Android camera and microphone indicators. This shows an indicator when an app the user has granted permission to access location requests location data. We also resolve various UX issues with this feature as it currently exists in AOSP to get it into a highly usable state.

The indicator works the same way as the Camera and Microphone ones, showing a bright green icon when location access occurs which then gets minimized to a small bright green dot when the quick settings tray isn't currently opened. Android 12 already includes Location with the other standard runtime permissions in the privacy dashboard for viewing the history.

This will likely become a standard feature in Android 13 at which point it will be removed from this page.

User installed apps can be disabled

GrapheneOS adds support for disabling user installed apps instead of only being able to disable system apps. This allows users to completely prevent one of the apps they've installed from being able to run without being forced to uninstall it and lose their app data. This is much stricter than the standard force stop feature which only prevents an app from starting itself and the app will start running again as soon as another app tries to open an activity or service it provides.

Other features

This is an incomplete list of other GrapheneOS features.

  • Low-level improvements to the filesystem-based full disk encryption used on modern Android
  • Improved user visibility into persistent firmware security through version and configuration verification with reporting of inconsistencies and debug features being enabled.
  • Authenticated encryption for network time updates via a first party server to prevent attackers from changing the time and enabling attacks based on bypassing certificate / key expiry, etc.
  • Proper support for disabling network time updates rather than just not using the results
  • Hardened local build / signing infrastructure
  • Seamless automatic OS update system that just works and stays out of the way in the background without disrupting device usage, with full support for the standard automatic rollback if the first boot of the updated OS fails
  • Require unlocking to access sensitive functionality via quick tiles
  • Minimal bundled apps and services. Only essential apps are integrated into the OS. We don't make partnerships with apps and services to bundle them into the OS. An app may be the best choice today and poor choice in the future. Our approach will be recommending certain apps during the initial setup, not hard-wiring them into the OS.

Services

Service infrastructure features:

Project

Beyond the technical features of the OS: