Description: Currently, for APK bundled with xwalk_shared_library (aka, shared mode APK), at the first launch, users will be prompted to download and install the XWalkRuntimeLib.apk explicitly when the runtime APK had not been installed on the device. Some customers think that it’s not user-friendly and then they want to have the runtime APK downloaded/installed in the background silently without any user interaction.
To meet this customer request, we are proposing the introduction of “silent download mode”. In silent download mode, customer’s application is still bundled with xwalk_shared_library in order to keep the app size as small as possible, while the XWalkRuntimeLib.apk is downloaded from the host indicated by customer in the background silently at the first launch of customer’s APK and the runtime libraries/resources will be extracted from the downloaded runtime APK and loaded as a plugin, that is, the runtime APK will not be installed as a normal application as usual. *Security Concern* After the XWalkRuntimeLib.apk was downloaded, we will check the integrity of the APK and check the signature of the APK to ensure that the APK was signed with either Chromium debug key or Intel’s private key. The XWalkRuntimeLib.apk built by Crosswalk buildbot (could be downloaded from https://download.01.org/crosswalk/releases/crosswalk/android/canary/latest/) was signed with Chromium debug key by default and the one released to Google Play was re-signed with Intel’s private key, that’s why we check these two keys here. *Deployment* Given that the security check mentioned above, XWalkRuntimeLib.apk signed with developer’s private key is NOT supported. Developers have to grab a build from Crosswalk official build or the one released to Google Play. However, a local built XWalkRuntimeLib.apk is also supported as the local build will be signed with Chromium debug key by default. Developer need to host XWalkRuntimeLib.apk for different CPU architectures, the URL will be appended with a query string “?arch=CPU_ABI” when the request is sent to server, where CPU_ABI is exactly the same as the value returned from “adb shell getprop ro.product.cpu.abi”, e.g, x86 for x86 32bit, armeabi-v7a for ARM 32bit. *Advantages* * App size is as small as shared mode’s * Developer can use a dedicated XWalkRuntimeLib.apk for his/her application while can avoid huge app size in embedded mode. Affected component: Crosswalk Related feature: https://crosswalk-project.org/jira/browse/XWALK-5121 Target release: Crosswalk-16 Implementation details: Code review is ready @ https://github.com/XiaosongWei/crosswalk/tree/silent-download 1) The URL where XWalkRuntimeLib.apk will be downloaded from is specified in AndroidManifest.xml, using a meta-data entry <meta-data android:name=”xwalk_apk_url” android:value=”http://host/XWalkRuntimeLib.apk” />. 2) A new interface XWalkBackgroundUpdateListener is added in XWalkUpdater and developer should create XWalkUpdater with XWalkBackgroundUpdateListener in order to get App work under silent download mode. 3) After the downloaded XWalkRuntimeLib.apk has been verified good, Crosswalk runtime libraries/resources ( libxwalkcore.so, classes.dex, xwalk.pak and icudtl.dat ) will be extracted from the downloaded XWalkRuntimeLib.apk and saved to app’s private folder. 4) In XWalkCoreWrapper.java attachXWalkCore() will invoke a new method findDownloadedCore() to check if the downloaded core library is ready. And within findDownloadedCore(), a DexClassLoader is created to load xwalk core library from the extracted classes.dex 5) make_apk.py will be modified to support silent download mode packaging Thanks, Xiaosong
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