nixpkgs/nixos/modules/security
aszlig dcf40f7c24
Merge pull request (systemd-confinement)
Currently if you want to properly chroot a systemd service, you could do
it using BindReadOnlyPaths=/nix/store or use a separate derivation which
gathers the runtime closure of the service you want to chroot. The
former is the easier method and there is also a method directly offered
by systemd, called ProtectSystem, which still leaves the whole store
accessible. The latter however is a bit more involved, because you need
to bind-mount each store path of the runtime closure of the service you
want to chroot.

This can be achieved using pkgs.closureInfo and a small derivation that
packs everything into a systemd unit, which later can be added to
systemd.packages.

However, this process is a bit tedious, so the changes here implement
this in a more generic way.

Now if you want to chroot a systemd service, all you need to do is:

  {
    systemd.services.myservice = {
      description = "My Shiny Service";
      wantedBy = [ "multi-user.target" ];

      confinement.enable = true;
      serviceConfig.ExecStart = "${pkgs.myservice}/bin/myservice";
    };
  }

If more than the dependencies for the ExecStart* and ExecStop* (which
btw. also includes script and {pre,post}Start) need to be in the chroot,
it can be specified using the confinement.packages option. By default
(which uses the full-apivfs confinement mode), a user namespace is set
up as well and /proc, /sys and /dev are mounted appropriately.

In addition - and by default - a /bin/sh executable is provided, which
is useful for most programs that use the system() C library call to
execute commands via shell.

Unfortunately, there are a few limitations at the moment. The first
being that DynamicUser doesn't work in conjunction with tmpfs, because
systemd seems to ignore the TemporaryFileSystem option if DynamicUser is
enabled. I started implementing a workaround to do this, but I decided
to not include it as part of this pull request, because it needs a lot
more testing to ensure it's consistent with the behaviour without
DynamicUser.

The second limitation/issue is that RootDirectoryStartOnly doesn't work
right now, because it only affects the RootDirectory option and doesn't
include/exclude the individual bind mounts or the tmpfs.

A quirk we do have right now is that systemd tries to create a /usr
directory within the chroot, which subsequently fails. Fortunately, this
is just an ugly error and not a hard failure.

The changes also come with a changelog entry for NixOS 19.03, which is
why I asked for a vote of the NixOS 19.03 stable maintainers whether to
include it (I admit it's a bit late a few days before official release,
sorry for that):

  @samueldr:

    Via pull request comment[1]:

      +1 for backporting as this only enhances the feature set of nixos,
      and does not (at a glance) change existing behaviours.

    Via IRC:

      new feature: -1, tests +1, we're at zero, self-contained, with no
      global effects without actively using it, +1, I think it's good

  @lheckemann:

    Via pull request comment[2]:

      I'm neutral on backporting. On the one hand, as @samueldr says,
      this doesn't change any existing functionality. On the other hand,
      it's a new feature and we're well past the feature freeze, which
      AFAIU is intended so that new, potentially buggy features aren't
      introduced in the "stabilisation period". It is a cool feature
      though? :)

A few other people on IRC didn't have opposition either against late
inclusion into NixOS 19.03:

  @edolstra:  "I'm not against it"
  @Infinisil: "+1 from me as well"
  @grahamc:   "IMO its up to the RMs"

So that makes +1 from @samueldr, 0 from @lheckemann, 0 from @edolstra
and +1 from @Infinisil (even though he's not a release manager) and no
opposition from anyone, which is the reason why I'm merging this right
now.

I also would like to thank @Infinisil, @edolstra and @danbst for their
reviews.

[1]: https://github.com/NixOS/nixpkgs/pull/57519#issuecomment-477322127
[2]: https://github.com/NixOS/nixpkgs/pull/57519#issuecomment-477548395
2019-03-29 04:37:53 +01:00
..
wrappers nixos/wrappers: remove outdated upgrade code 2018-10-21 15:12:36 +02:00
acme.nix acme module: fix self-signed cert with openssl 1.1 2018-09-12 13:40:46 +02:00
acme.xml docs: format 2018-09-29 20:51:11 -04:00
apparmor-suid.nix apparmor-suid: don't force glibc 2018-10-30 19:50:47 -05:00
apparmor.nix apparmor: support for lxc profiles 2017-01-10 23:01:03 +01:00
audit.nix nixos: Move uses of stdenv.shell to runtimeShell. 2018-03-01 14:38:53 -05:00
auditd.nix nixos/auditd: break ordering cycle () 2017-08-01 20:45:01 +01:00
ca.nix nixos: add preferLocalBuild=true; on derivations for config files 2019-02-22 20:11:27 +01:00
chromium-suid-sandbox.nix nixos/chromium-suid-sandbox: remove reference to grsecurity 2017-09-02 20:35:28 +02:00
dhparams.nix dhparams module: add self as maintainer 2018-10-31 01:05:35 +09:00
duosec.nix nixos/security: make duo support secure failure correctly 2019-03-17 18:25:20 -07:00
google_oslogin.nix config.security.googleOsLogin: add module 2018-12-21 17:52:37 +01:00
hidepid.nix [bot] nixos/*: remove unused arguments in lambdas 2018-07-20 20:56:59 +00:00
hidepid.xml docs: format 2018-09-29 20:51:11 -04:00
lock-kernel-modules.nix nixos/lock-kernel-modules: add myself to maintainers 2018-10-15 01:33:30 +02:00
misc.nix nixos/security/misc: expose SMT control option 2018-12-27 15:00:49 +01:00
oath.nix [bot] nixos/*: remove unused arguments in lambdas 2018-07-20 20:56:59 +00:00
pam_mount.nix nixos/modules: users.(extraUsers|extraGroup->users|group) 2018-06-30 03:02:58 +02:00
pam_usb.nix [bot] treewide: remove unused 'inherit' in let blocks 2018-07-20 19:38:19 +00:00
pam.nix nixos/security: Add duo-unix support to pam. 2019-02-24 22:48:56 +00:00
polkit.nix nixos/polkit: use tmpfiles to clean old dirs 2018-09-30 11:08:11 -07:00
prey.nix nixos: fix some types 2015-09-18 18:48:50 +00:00
rngd.nix nixos/rngd: do not pass --version flag 2018-11-05 10:41:38 +01:00
rtkit.nix nixos/modules: users.(extraUsers|extraGroup->users|group) 2018-06-30 03:02:58 +02:00
sudo.nix nixos: add preferLocalBuild=true; on derivations for config files 2019-02-22 20:11:27 +01:00
systemd-confinement.nix nixos/confinement: Use PrivateMounts option 2019-03-27 20:34:32 +01:00