nixos/immich: restrict media filesystem permissions

[Ralith]

immich appears to create this directory with permissions 0755 by default, which needlessly exposes user data to other processes.

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandboxing enabled in nix.conf? (See Nix manual)
  • sandbox = relaxed
  • sandbox = true
• Tested, as applicable:
  • NixOS test(s) (look inside nixos/tests)
  • and/or package tests
  • or, for functions and "core" functionality, tests in lib/tests or pkgs/test
  • made sure NixOS tests are linked to the relevant packages
• Tested compilation of all packages that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage
• Tested basic functionality of all binary files (usually in ./result/bin/)
• 25.05 Release Notes (or backporting 24.11 and 25.05 Release notes)
  • (Package updates) Added a release notes entry if the change is major or breaking
  • (Module updates) Added a release notes entry if the change is significant
  • (Module addition) Added a release notes entry if adding a new NixOS module
• Fits CONTRIBUTING.md.

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[dotlambda]

We should rather set serviceConfig.UMask.

[Ralith]

That does seem more elegant, but will it fix up existing installations? Seems like a shame to leave some unknown number of users with world-readable data.

[dotlambda]

will it fix up existing installations?

I don't think we should mess with existing installations. What if someone manually adjusted the permissions?
Maybe just add a changelog entry?
EDIT: Actually, this is probably fine. But let's hear the opinion of the other Immich maintainers.

[Ralith]

Applied suggestions. Does also excluding group permissions serve a security purpose, or is it just on principle of minimizing surface area?

[dotlambda]

Does also excluding group permissions serve a security purpose, or is it just on principle of minimizing surface area?

I guess it's the latter. I'm just following what most other NixOS services with a umask do.

[dotlambda]

@ofborg test immich

[dotlambda]

@ofborg test immich