What exactly change that is causing the old SU binaries to fail in android 8?

I have here the source code for the SU addon for Lineage OS: https://github.com/LineageOS/android_system_extras_su

I looked through the source code and am not sure how it works. It seems to spawn a daemon process that handles all calls to root, but other than that I'm not really sure what's happening.

There's really no documentation for this source code, and I can't even find any technical write-up on how systemless rooting even works in android 8.

The main file is su.c, where it seems to provide a sort of terminal-like interface for the application requesting root. From there it looks like it goes to open a socket to a daemon process.It's not clear to me where we're even getting access to root here.

Can anyone provide a brief overview of how rooting works, or point me to somewhere that does?

  • Rooting (modifying a system so that root access is possible) and executing something with root permission something completely different. su makes the latter on a previously rooted system. – Robert Mar 23 '18 at 20:28
  • Systemless rooting works slightly different to system rooting and it's extremely restricted compared to a full system RW access root, However many files are manipulated by the system for system application purposes such as the Build.prop file etc, This means an application at a root level also can manipulate this file without raising the system is modified flag, You can manipulate the system with systemless root but it can cause a bricked device, Usually installing things like busybox will work fine, it might be the folder permissions for bin or xbin may be different from other system folders – Gadget Guru Mar 24 '18 at 0:33

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