‘Resume on Reboot’ will make Android OTA updates far more seamless

Kyle Bradshaw | Dec 11 2019 - 3:22 pm PT

As Android has developed, its update process has become more and more of a hands-off experience, but there’s still one snag that prevents updates from being able to happen without your input. According to a new code change, this may soon be changing with a new Android feature called “Resume on Reboot.”

When you update your Android phone, Android will typically clear the dalvik cache for all of your apps and need to rebuild that cache so your apps can be used correctly. This process is usually displayed as “Android is upgrading.”

Despite being a core part of installing an OTA on Android, this step actually can’t be done without your initial input. For security purposes, any time your phone restarts, your device’s secure storage — also called “credential encrypted” (CE) storage — is locked until you enter a pin or pattern.

With security becoming more and more important, Android stores the majority of your files in CE storage, including personal files and your apps. Thus, the problem we all run into is that the OTA process needs to manage your apps, but your apps are locked up tight in CE storage until you manually unlock your phone.

Over the weekend, Google posted an interesting new commit to the Android Open Source Project, also spotted by our friends at XDA-Developers, entitled “Support Resume on Reboot.” The developer was kind enough to offer a technical explanation of the new feature.

When an OTA is downloaded, the RecoverySystem can be triggered to store the user’s lock screen knowledge factor in a secure way using the IRebootEscrow HAL. This will allow the credential encrypted (CE) storage, keymaster credentials, and possibly others to be unlocked when the device reboots after an OTA.

Essentially, once Resume on Reboot becomes available, Android will be able to complete the OTA process, restart your phone, and clean & rebuild the dalvik cache without needing your input. To do this, Android will securely and temporarily store your unlock pin or pattern — also known as your “lock screen knowledge factor” — before an update and use it to unlock the secure CE storage afterwards.

Of course, anything that stores your pin/pattern should be carefully considered, from a security perspective. Unfortunately for now, there isn’t much in the code itself to show us what’s happening under the hood, as it appears the rest of the code is in the closed source, internal version of Android.

On the flip side, Resume on Reboot will make your Android phone’s monthly security update much less of an inconvenience. In fact, if you enable automatic updates, your phone should be able to update overnight and be fully ready to use in the morning.

The lingering question is when can we expect to use this? Android 11 would be a safe bet, but it’s also possible Google could bring it sooner. All we know for now is that the Google Pixel 4 will likely be one of the first devices to support Resume on Reboot, as the developer lists it as one of the tested devices.