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
eb90d97009 broke nslcd, as /run/nslcd was
created/chowned as root user, while nslcd wants to do parts as nslcd
user.
This commit changes the nslcd to run with the proper uid/gid from the
start (through User= and Group=), so the RuntimeDirectory has proper
permissions, too.
In some cases, secrets are baked into nslcd's config file during startup
(so we don't want to provide it from the store).
This config file is normally hard-wired to /etc/nslcd.conf, but we don't
want to use PermissionsStartOnly anymore (#56265), and activation
scripts are ugly, so redirect /etc/nslcd.conf to /run/nslcd/nslcd.conf,
which now gets provisioned inside ExecStartPre=.
This change requires the files referenced to in
users.ldap.bind.passwordFile and users.ldap.daemon.rootpwmodpwFile to be
readable by the nslcd user (in the non-nslcd case, this was already the
case for users.ldap.bind.passwordFile)
fixes#57783
First of all, the reason I added this to the "highlights" section is
that we want users to be aware of these options, because in the end we
really want to decrease the attack surface of NixOS services and this is
a step towards improving that situation.
The reason why I'm adding this to the changelog of the NixOS 19.03
release instead of 19.09 is that it makes backporting services that use
these options easier. Doing the backport of the confinement module after
the official release would mean that it's not part of the release
announcement and potentially could fall under the radar of most users.
These options and the whole module also do not change anything in
existing services or affect other modules, so they're purely optional.
Adding this "last minute" to the 19.03 release doesn't hurt and is
probably a good preparation for the next months where we hopefully
confine as much services as we can :-)
I also have asked @samueldr and @lheckemann, whether they're okay with
the inclusion in 19.03. While so far only @samueldr has accepted the
change, we can still move the changelog entry to the NixOS 19.09 release
notes in case @lheckemann rejects it.
Signed-off-by: aszlig <aszlig@nix.build>
Compatibility with other distributions/software and expectation
of users coming from other systems should have higher priority over consistency.
In particular this fixes#51375, where the NetworkManager-wait-online.service
broke as a result of this.
This is a backwards-incompatible change and while it won't probably
affect a whole lot of users, it makes sense to give them a heads-up
anyway.
Signed-off-by: aszlig <aszlig@nix.build>
The explicit remove helped to uncover some hidden uses of `optionSet`
in NixOps. However it makes life harder for end-users of NixOps - it will
be impossible to deploy 19.03 systems with old NixOps, but there is no
new release of NixOps with `optionSet` fixes.
Also, "deprecation" process isn't well defined. Even that `optionSet` was
declared "deprecated" for many years, it was never announced. Hence, I
leave "deprecation" announce. Then, 3 releases after announce,
we can announce removal of this feature.
This type has to be removed, not `throw`-ed in runtime, because it makes
some perfectly fine code to fail. For example:
```
$ nix-instantiate --eval -E '(import <nixpkgs/lib>).types' --strict
trace: `types.list` is deprecated; use `types.listOf` instead
error: types.optionSet is deprecated; use types.submodule instead
(use '--show-trace' to show detailed location information)
```
Before this change `man 5 configuration.nix` would only show options of modules in
the `baseModules` set, which consists only of the list of modules in
`nixos/modules/module-list.nix`
With this change applied and `documentation.nixos.includeAllModules` option enabled
all modules included in `configuration.nix` file will be used instead.
This makes configurations with custom modules self-documenting. It also means
that importing non-`baseModules` modules like `gce.nix` or `azure.nix`
will make their documentation available in `man 5 configuration.nix`.
`documentation.nixos.includeAllModules` is currently set to `false` by
default as enabling it usually uncovers bugs and prevents evaluation.
It should be set to `true` in a release or two.
This was originally implemented in #47177, edited for more configurability,
documented and rebased onto master by @oxij.
