nixos/confinement: Allow to include the full unit

From @edolstra at [1]:

  BTW we probably should take the closure of the whole unit rather than
  just the exec commands, to handle things like Environment variables.

With this commit, there is now a "fullUnit" option, which can be enabled
to include the full closure of the service unit into the chroot.

However, I did not enable this by default, because I do disagree here
and *especially* things like environment variables or environment files
shouldn't be in the closure of the chroot.

For example if you have something like:

  { pkgs, ... }:

  {
    systemd.services.foobar = {
      serviceConfig.EnvironmentFile = ${pkgs.writeText "secrets" ''
        user=admin
        password=abcdefg
      '';
    };
  }

We really do not want the *file* to end up in the chroot, but rather
just the environment variables to be exported.

Another thing is that this makes it less predictable what actually will
end up in the chroot, because we have a "globalEnvironment" option that
will get merged in as well, so users adding stuff to that option will
also make it available in confined units.

I also added a big fat warning about that in the description of the
fullUnit option.

[1]: https://github.com/NixOS/nixpkgs/pull/57519#issuecomment-472855704

Signed-off-by: aszlig <aszlig@nix.build>

1 files changed, 13 insertions, 0 deletions

diff --git a/nixos/tests/systemd-confinement.nix b/nixos/tests/systemd-confinement.nix
index 63cb074d7ca1..b7b10fb36aac 100644
--- a/nixos/tests/systemd-confinement.nix
+++ b/nixos/tests/systemd-confinement.nix
@@ -132,6 +132,19 @@ import ./make-test.nix {
           );
         '';
       }
+      { description = "check if only Exec* dependencies are included";
+        config.environment.FOOBAR = pkgs.writeText "foobar" "eek\n";
+        testScript = ''
+          $machine->succeed('test "$(chroot-exec \'cat "$FOOBAR"\')" != eek');
+        '';
+      }
+      { description = "check if all unit dependencies are included";
+        config.environment.FOOBAR = pkgs.writeText "foobar" "eek\n";
+        config.confinement.fullUnit = true;
+        testScript = ''
+          $machine->succeed('test "$(chroot-exec \'cat "$FOOBAR"\')" = eek');
+        '';
+      }
     ];
 
     options.__testSteps = lib.mkOption {