update: Connectivity differences in Android ROMs (#2722)

Signed-off-by: redoomed1 <[email protected]>
Signed-off-by: Daniel Gray <[email protected]>

docs/android/distributions.md

@@ -62,10 +62,14 @@ GrapheneOS provides additional [security hardening](https://en.wikipedia.org/wik
 
 </div>
 
-GrapheneOS supports [sandboxed Google Play](https://grapheneos.org/usage#sandboxed-google-play), which runs [Google Play Services](https://en.wikipedia.org/wiki/Google_Play_Services) fully sandboxed like any other regular app. This means you can take advantage of most Google Play Services, such as [push notifications](https://firebase.google.com/docs/cloud-messaging), while giving you full control over their permissions and access, and while containing them to a specific [work profile](../os/android-overview.md#work-profile) or [user profile](../os/android-overview.md#user-profiles) of your choice.
+GrapheneOS supports [sandboxed Google Play](https://grapheneos.org/usage#sandboxed-google-play), which runs Google Play Services fully sandboxed like any other regular app. This means you can take advantage of most Google Play Services, such as push notifications, while giving you full control over their permissions and access, and while containing them to a specific [work profile](../os/android-overview.md#work-profile) or [user profile](../os/android-overview.md#user-profiles) of your choice.
 
 [Google Pixel phones](../mobile-phones.md#google-pixel) are the only devices that currently meet GrapheneOS's [hardware security requirements](https://grapheneos.org/faq#future-devices).
 
+By default, Android makes many network connections to Google to perform DNS connectivity checks, to sync with current network time, to check your network connectivity, and for many other background tasks. GrapheneOS replaces these with connections to servers operated by GrapheneOS and subject to their privacy policy. This hides information like your IP address [from Google](../basics/common-threats.md#privacy-from-service-providers), but means it is trivial for an admin on your network or ISP to see you are making connections to `grapheneos.network`, `grapheneos.org`, etc. and deduce what operating system you are using.
+
+GrapheneOS provides the option to switch back to connecting to Google's servers for many of these background connections if you prefer, but it is far more robust/foolproof to use a [trusted VPN](../vpn.md) and enable Android's native VPN [kill switch](../os/android-overview.md#vpn-killswitch) to hide information like this from adversaries on your network.
+
 ### DivestOS
 
 <div class="admonition recommendation" markdown>
@@ -84,12 +88,14 @@ DivestOS inherits many [supported devices](https://divestos.org/index.php?page=d
 
 </div>
 
-DivestOS has automated kernel vulnerability ([CVE](https://en.wikipedia.org/wiki/Common_Vulnerabilities_and_Exposures)) [patching](https://gitlab.com/divested-mobile/cve_checker), fewer proprietary blobs, and a custom [hosts](https://divested.dev/index.php?page=dnsbl) file. Its hardened WebView, [Mulch](https://gitlab.com/divested-mobile/mulch), enables [CFI](https://en.wikipedia.org/wiki/Control-flow_integrity) for all architectures and [network state partitioning](https://developer.mozilla.org/docs/Web/Privacy/State_Partitioning), and receives out-of-band updates.
+DivestOS has automated kernel vulnerability ([CVE](https://en.wikipedia.org/wiki/Common_Vulnerabilities_and_Exposures)) [patching](https://gitlab.com/divested-mobile/cve_checker), fewer proprietary blobs, and a custom [hosts](https://divested.dev/index.php?page=dnsbl) file. Its hardened WebView, [Mulch](https://gitlab.com/divested-mobile/mulch), enables [control-flow integrity](https://en.wikipedia.org/wiki/Control-flow_integrity) for all architectures and [network state partitioning](https://developer.mozilla.org/docs/Web/Privacy/State_Partitioning), and receives out-of-band updates.
 DivestOS also includes kernel patches from GrapheneOS and enables all available kernel security features via [defconfig hardening](https://github.com/Divested-Mobile/DivestOS-Build/blob/master/Scripts/Common/Functions.sh#L758). All kernels newer than version 3.4 include full page [sanitization](https://lwn.net/Articles/334747) and all ~22 Clang-compiled kernels have [`-ftrivial-auto-var-init=zero`](https://reviews.llvm.org/D54604?id=174471) enabled.
 
-DivestOS implements some system hardening patches originally developed for GrapheneOS. DivestOS 16.0 and higher implements GrapheneOS's [`INTERNET`](https://developer.android.com/training/basics/network-ops/connecting) and SENSORS permission toggle, [hardened memory allocator](https://github.com/GrapheneOS/hardened_malloc), [exec-spawning](https://grapheneos.org/usage#exec-spawning), [JNI](https://en.wikipedia.org/wiki/Java_Native_Interface) [constification](https://en.wikipedia.org/wiki/Const_(computer_programming)), and partial [bionic](https://en.wikipedia.org/wiki/Bionic_(software)) hardening patchsets. 17.1 and higher features GrapheneOS's per-network full [MAC randomization](https://en.wikipedia.org/wiki/MAC_address#Randomization) option, [`ptrace_scope`](https://kernel.org/doc/html/latest/admin-guide/LSM/Yama.html) control, [automatic reboot](https://grapheneos.org/features#auto-reboot), and Wi-Fi/Bluetooth [timeout options](https://grapheneos.org/features#attack-surface-reduction).
+DivestOS implements some system hardening patches originally developed for GrapheneOS. DivestOS 16.0 and higher implements GrapheneOS's `INTERNET` and `SENSORS` permission toggle, [hardened memory allocator](https://github.com/GrapheneOS/hardened_malloc), [exec-spawning](https://grapheneos.org/usage#exec-spawning), Java Native Interface [constification](https://en.wikipedia.org/wiki/Const_(computer_programming)), and partial [bionic](https://en.wikipedia.org/wiki/Bionic_(software)) hardening patchsets. 17.1 and higher features per-network full MAC address randomization, [`ptrace_scope`](https://kernel.org/doc/html/latest/admin-guide/LSM/Yama.html) control, automatic reboot, and Wi-Fi/Bluetooth [timeout options](https://grapheneos.org/features#attack-surface-reduction).
+
+DivestOS uses F-Droid as its default app store. We normally [recommend avoiding F-Droid](obtaining-apps.md#f-droid), but doing so on DivestOS isn't viable; the developers update their apps via their own F-Droid repository, [DivestOS Official](https://divestos.org/fdroid/official). For these apps you should continue to use F-Droid **with the DivestOS repository enabled** to keep those components up to date. For other apps, our recommended [methods of obtaining them](obtaining-apps.md) still apply.
 
-DivestOS uses F-Droid as its default app store. We normally [recommend avoiding F-Droid](obtaining-apps.md#f-droid), but doing so on DivestOS isn't viable; the developers update their apps via their own F-Droid repository, [DivestOS Official](https://divestos.org/fdroid/official). We recommend disabling the official F-Droid app and using [F-Droid Basic](https://f-droid.org/en/packages/org.fdroid.basic) **with the DivestOS repository enabled** to keep those components up to date. For other apps, our recommended [methods of obtaining them](obtaining-apps.md) still apply.
+DivestOS replaces many of Android's background network connections to Google services with alternative services, such as using OpenEUICC for eSIM activation, NTP.org for network time, and Quad9 for DNS. These connections can be modified, but their deviation from a standard Android phone's network connections could mean it is easier for an adversary on your network to deduce what operating system you have installed on your phone. If this is a concern to you, consider using a [trusted VPN](../vpn.md) and enabling the native VPN [kill switch](../os/android-overview.md#vpn-killswitch) to hide this network traffic from your local network and ISP.
 
 <div class="admonition warning" markdown>
 <p class="admonition-title">Warning</p>