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Termux and Android 10

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Leonid Pliushch edited this page Aug 9, 2020 · 41 revisions

Summary

Termux does not target API 29 (Android 10) due to https://developer.android.com/about/versions/10/behavior-changes-all#execute-permission:

Untrusted apps that target Android 10 cannot invoke exec() on files within the app's home directory. This execution of files from the writable app home directory is a W^X violation. Apps should load only the binary code that's embedded within an app's APK file.

In the long run this needs to be fixed and Termux needs to update its target API. This page is for information about how to work around this.

Issue with discussion: https://github.com/termux/termux-app/issues/1072.

How issue is going to be solved ?

Package *.deb files will be transformed into APK file, where the data will be placed into JNI lib directory which is marked executable by Android OS. That makes package data to be read-only and overcome the SELinux restrictions applied.

During installation of such package the contents in JNI lib directory are symlinked to $PREFIX mimicking the normal environment like a pre- Android 10 one. Package management is handled by Termux application with command line interface exposed through utility pkg. Apt package manager is going to be removed.

Sample packages can be obtained from http://termux.net/apks/.

Related pull request: https://github.com/termux/termux-app/pull/1427

Why distribute packages in APKs ?

We choose to distribute packages in APKs because only that solution is correct. Android package format expects native code to be placed in directory for JNI libraries and that comply with W^X policy.

Of course that will made Termux "non-convenient" for users, but actually Termux can have some benefits from that packaging format change. Here is what will be possible with in-APK package distribution:

  • Full offline installation.
  • Integrity of package files. Since files are enforced to be read-only by Android OS, you can expect that they are immutable and can't be changed accidentally by script or something else.
  • Easy package downgrading without having to mess with the correct dependency versions.
  • Easy environment repair. It is possible to implement it as one-click action.

Alternate solutions

There is a number of other solutions that were suggested during discussion.

Please understand that we are not looking on other solutions beyond in-APK packaging anymore. We already have one (WIP currently) which will require minimal effort for maintaining and provide minimal feature loss. If you want to suggest your solution, provide the related pull requests and be ready to maintain it in case it will be accepted.

Name Compatibility with Google Play policy* Notes
Keep SDK 28 Not as minimum target SDK level increases each year. Will render Termux incompatible with new devices and kill project in future.
PRoot No. It implements custom executable loader. May cause issues with certain programs. May not work properly on some devices.
QEMU system mode Full or partial (code is executed in emulator). Low performance and environment isolation make it unsuitable for using Termux as terminal emulator for Android.
User-mode Linux No. Code is executed on host, can be treated as custom executable loader. Is not available for ARM and AArch64. Termux developers can't port it on these architectures. Termux will not be able to run root packages properly.
Userland exec No. It implements custom executable loader. For x86_64 and glibc only. Termux developers are not going to port it.
WASM Full or partial (depening on implementation). There no people in Termux developers who wish to or can maintain WASM package ports and runtime.

* Google Play policy restricts sideloading of executable code. See https://support.google.com/googleplay/android-developer/answer/9887877.

Additional notes about Termux and SDK-29

  • Users updating Termux compiled with SDK-28 to application compiled with SDK-29, will not face the execve() restriction.

  • On some devices, execve() is restricted even for SDK <=28, so any Termux build doesn't work on them.

  • Termux compiled with SDK-29 will lose access to shared storage /sdcard due to forced scoped storage.

  • Lineage OS 17 ROM (Android 10 based) does not restrict execve() for SDK-29 but free access to storage is lost anyway.

Android 11+ issues

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