That's also incorrect, because the gmscompat app is just a helper app. Play services can and does request additional permissions. Those permissions are handled by the OS under the play services app, not gmscompat. If you want RCS for instance, you must grant play services and google messages phone and ICC auth access, which isn't seen in gmscompat at all.

  > That's also incorrect, because the gmscompat app is just a helper app.

Hmm, ok. I was reasoning the helper app was needed to get around the default assumptions from Google Play Services.

  >  Those permissions are handled by the OS under the play services app

Yes, but I assume you don't mean that as that GOS makes special hard-coded provisions for the play services. GOS claims to run Play Services like any other unprivileged app, and so any additional permission it would want would have to be consented by the user and should be visible to the user. If not, then GOS wording would be quite a bit unfortunate at least.

EDIT: "GmsCompatConfig is the text-based configuration for the GrapheneOS sandboxed Google Play compatibility layer. It provides a large portion of the compatibility shims." [1] This seems to indicate that the permissions requested by Play Services are being honored with the shims from the helper app. That would alleviate the permission problem.

1. https://github.com/GrapheneOS/platform_packages_apps_GmsComp...

Google Mobile Services apps installed on GrapheneOS including Play services run as regular sandboxed apps. They receive absolutely no special access compared to other apps by installing and running them. There are the standard permission toggles for granting those but none of those are required for typical usage to provide compatibility with many apps from the Play Store depending on their services.

There are additional special permission toggles for RCS and Android Auto. The issue with RCS is mainly that they split the implementation across Google Messages and Play services. Android's standard permission model gives special access to the app selected by the user as the messaging app but Google Messages expects Play services to have special access too.

The shims defined with GmsCompatConfig are a small subset of the overall compatibility layer. It has many shims which need to actually implement the functionality such as remapping the Play Store using privileged installation APIs to the regular ones available to user installed app stores. It has to remap the APIs used by dynamite modules to ones not requiring privileged SELinux policies too. It has a mix of shims which simply stub out the functionality and many which need to handle it as a regular sandboxed app would need to do it.

Thank you for clarifying this.