From f8d78b9f67bdd3b6b12dbe1b6a2377ec0eef8050 Mon Sep 17 00:00:00 2001
From: Dominique Martinet <asmadeus@codewreck.org>
Date: Mon, 28 Sep 2020 13:27:47 +0200
Subject: [PATCH] confinement: fix assert for serviceConfig.ProtectSystem

serviceConfig.ProtectSystem is usually a string so if set, the assert
itself would error out leaving no useable trace:

  # nixos-rebuild switch --show-trace
  building Nix...
  building the system configuration...
  error: while evaluating the attribute 'config.system.build.toplevel' at /nix/var/nix/profiles/per-user/root/channels/nixos/nixos/modules/system/activation/top-level.nix:293:5:
  while evaluating 'foldr' at /nix/var/nix/profiles/per-user/root/channels/nixos/lib/lists.nix:52:20, called from /nix/var/nix/profiles/per-user/root/channels/nixos/nixos/modules/system/activation/top-level.nix:128:12:
  while evaluating 'fold'' at /nix/var/nix/profiles/per-user/root/channels/nixos/lib/lists.nix:55:15, called from /nix/var/nix/profiles/per-user/root/channels/nixos/lib/lists.nix:59:8:
  while evaluating anonymous function at /nix/var/nix/profiles/per-user/root/channels/nixos/nixos/modules/system/activation/top-level.nix:121:50, called from undefined position:
  while evaluating the attribute 'assertion' at /nix/var/nix/profiles/per-user/root/channels/nixos/nixos/modules/security/systemd-confinement.nix:163:7:
  value is a string while a Boolean was expected

Fix the check to give a sensible assert message instead; the attribute
should either be not set or false bool to pass.

Closes: #99000
---
 nixos/modules/security/systemd-confinement.nix | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/nixos/modules/security/systemd-confinement.nix b/nixos/modules/security/systemd-confinement.nix
index 2927d424a8a..afb81a2b56b 100644
--- a/nixos/modules/security/systemd-confinement.nix
+++ b/nixos/modules/security/systemd-confinement.nix
@@ -160,7 +160,7 @@ in {
               + " the 'users.users' option instead as this combination is"
               + " currently not supported.";
     }
-    { assertion = !cfg.serviceConfig.ProtectSystem or false;
+    { assertion = cfg.serviceConfig ? ProtectSystem -> cfg.serviceConfig.ProtectSystem == false;
       message = "${whatOpt "ProtectSystem"}. ProtectSystem is not compatible"
               + " with service confinement as it fails to remount /usr within"
               + " our chroot. Please disable the option.";