OpenSync Android Template

An example/template vendor layer implementation for Android-based devices.

Target:

• ANDROID_GENERIC - generic Android implementation

The example implementation can be used to create a custom vendor layer for the specific hardware at hand.

Reference software versions

• Components and versions:

  Component	Version
  OpenSync core	6.2.x	public
  OpenSync vendor/android-template	6.2.x	public
  OpenSync platform/android	6.2.x	public
  Android	>= 9.0	public

Hardware information

• Interfaces:

  Interface	Description
  eth0	ethernet interface
  wlan0	Wi-Fi STA interface

OpenSync root directory

OpenSync build system requires a certain directory structure in order to ensure modularity. Key components are:

• OpenSync core: ${OPENSYNC_ROOT}/core
• OpenSync Android platform: ${OPENSYNC_ROOT}/platform/android
• OpenSync vendor layer template: ${OPENSYNC_ROOT}/vendor/android-template
• OpenSync service provider: ${OPENSYNC_ROOT}/service-provider/local (local given as an example which needs to be replaced with your service provider)

Follow these steps to populate the ${OPENSYNC_ROOT} directory:

$ git clone --branch osync_6.2.x https://github.com/plume-design/opensync.git ${OPENSYNC_ROOT}/core
$ git clone --branch osync_6.2.x https://github.com/plume-design/opensync-platform-android.git ${OPENSYNC_ROOT}/platform/android
$ git clone --branch osync_6.2.x https://github.com/plume-design/opensync-vendor-android-template.git ${OPENSYNC_ROOT}/vendor/android-template
$ git clone --branch osync_6.2.x https://github.com/plume-design/opensync-service-provider-local.git ${OPENSYNC_ROOT}/service-provider/local
$ mkdir -p ${OPENSYNC_ROOT}/3rdparty

The resulting layout should be as follows:

${OPENSYNC_ROOT}
├── 3rdparty
│   └── ...
├── core
│   ├── 3rdparty -> ../3rdparty
│   ├── build
│   ├── doc
│   ├── docker
│   ├── interfaces
│   ├── kconfig
│   ├── Makefile
│   ├── ovsdb
│   ├── platform -> ../platform
│   ├── README.md
│   ├── rootfs
│   ├── service-provider -> ../service-provider
│   ├── src
│   └── vendor -> ../vendor
├── platform
│   └── android
├── service-provider
│   └── local
└── vendor
    └── android-template

Build

1. Clone the build system provided in opensync-sdk-android repository:

git clone --branch osync_6.2.x https://github.com/plume-design/opensync-sdk-android.git ${SDK_ROOT}

2. In ${SDK_ROOT}, run make with OPENSYNC_SRC specified:

make OPENSYNC_SRC=${OPENSYNC_ROOT} build

The resulting APK package is located in build-android-generic/apk/app/build/outputs/apk.

Install and run

Install and run the OpenSync APK on your Android device using the standard method.

Android 10 W^X Violation

Up to Android 9 (targetSdkVersion <= 28), apps were able to invoke exec() on binary code embedded within app's APK file.
On Android 10 (targetSdkVersion > 28) however, W^X restrictions do not allow app's data files to be executed, even if signed with the platform key (system app).

Example of logged errors:

10-21 00:13:33.608  4892  4892 W Thread-3: type=1400 audit(0.0:460): avc: denied { execute } for name="ovsdb-server" dev="mmcblk0p23" ino=459791 scontext=u:r:system_app:s0 tcontext=u:object_r:system_app_data_file:s0 tclass=file permissive=0
10-21 00:13:33.616  4851  4889 W System.err: java.io.IOException: Cannot run program "/data/user/0/com.opensync.app/files/bin/ovsdb-server": error=13, Permission denied
10-21 00:13:33.617  4851  4889 W System.err: 	at com.opensync.app.OpenSyncBootStrap$1.run(OpenSyncBootStrap.java:189)
10-21 00:13:33.612  4893  4893 W Thread-2: type=1400 audit(0.0:461): avc: denied { execute } for name="dm" dev="mmcblk0p23" ino=459829 scontext=u:r:system_app:s0 tcontext=u:object_r:system_app_data_file:s0 tclass=file permissive=0
10-21 00:13:33.622  4851  4888 W System.err: java.io.IOException: Cannot run program "/data/user/0/com.opensync.app/files/opensync/bin/dm": error=13, Permission denied
10-21 00:13:33.622  4851  4888 W System.err: 	at com.opensync.app.OpenSyncBootStrap$1.run(OpenSyncBootStrap.java:189)

To fix the issue, a separate set of Android SELinux rules is needed for the OpenSync app. These rules must be based on the same foundation as the System App, with some additional rules incorporated. Refer to the directory of ${SDK_ROOT}/sepolicy and apply the patches to your Android sepolicy source code. Note that sepolicy may vary for different Android versions. The patches include changes for API levels 28 to 33. You should refer to these modifications and subsequently port them to your sepolicy directory based on your Android version.

For more information, see https://issuetracker.google.com/issues/128554619.

Device access

To access the device (e.g. for debugging) use 'Android Debug Bridge (adb)'.

OpenSync resources

For further information please visit: https://www.opensync.io/