2020-02-14 08:48:42 +00:00
|
|
|
import ./make-test-python.nix {
|
2019-03-14 14:26:10 +00:00
|
|
|
name = "systemd-confinement";
|
nixos: Add 'chroot' options to systemd.services
Currently, if you want to properly chroot a systemd service, you could
do it using BindReadOnlyPaths=/nix/store (which is not what I'd call
"properly", because the whole store is still accessible) or use a
separate derivation that 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. That's also what I did several times[1][2] in the
past.
However, this process got a bit tedious, so I decided that it would be
generally useful for NixOS, so this very implementation was born.
Now if you want to chroot a systemd service, all you need to do is:
{
systemd.services.yourservice = {
description = "My Shiny Service";
wantedBy = [ "multi-user.target" ];
chroot.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 chroot.packages option. By
default (which uses the "full-apivfs"[3] 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 as well,
which is useful for most programs that use the system() C library call
to execute commands via shell. The shell providing /bin/sh is dash
instead of the default in NixOS (which is bash), because it's way more
lightweight and after all we're chrooting because we want to lower the
attack surface and it should be only used for "/bin/sh -c something".
Prior to submitting this here, I did a first implementation of this
outside[4] of nixpkgs, which duplicated the "pathSafeName" functionality
from systemd-lib.nix, just because it's only a single line.
However, I decided to just re-use the one from systemd here and
subsequently made it available when importing systemd-lib.nix, so that
the systemd-chroot implementation also benefits from fixes to that
functionality (which is now a proper function).
Unfortunately, we do have a few limitations as well. The first being
that DynamicUser doesn't work in conjunction with tmpfs, because it
already sets up a tmpfs in a different path and simply ignores the one
we define. We could probably solve this by detecting it and try to
bind-mount our paths to that different path whenever DynamicUser is
enabled.
The second limitation/issue is that RootDirectoryStartOnly doesn't work
right now, because it only affects the RootDirectory option and not the
individual bind mounts or our tmpfs. It would be helpful if systemd
would have a way to disable specific bind mounts as well or at least
have some way to ignore failures for the bind mounts/tmpfs setup.
Another 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.
[1]: https://github.com/headcounter/shabitica/blob/3bb01728a0237ad5e7/default.nix#L43-L62
[2]: https://github.com/aszlig/avonc/blob/dedf29e092481a33dc/nextcloud.nix#L103-L124
[3]: The reason this is called "full-apivfs" instead of just "full" is
to make room for a *real* "full" confinement mode, which is more
restrictive even.
[4]: https://github.com/aszlig/avonc/blob/92a20bece4df54625e/systemd-chroot.nix
Signed-off-by: aszlig <aszlig@nix.build>
2019-03-10 11:21:55 +00:00
|
|
|
|
|
|
|
machine = { pkgs, lib, ... }: let
|
|
|
|
testServer = pkgs.writeScript "testserver.sh" ''
|
2020-04-07 07:25:48 +01:00
|
|
|
#!${pkgs.runtimeShell}
|
nixos: Add 'chroot' options to systemd.services
Currently, if you want to properly chroot a systemd service, you could
do it using BindReadOnlyPaths=/nix/store (which is not what I'd call
"properly", because the whole store is still accessible) or use a
separate derivation that 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. That's also what I did several times[1][2] in the
past.
However, this process got a bit tedious, so I decided that it would be
generally useful for NixOS, so this very implementation was born.
Now if you want to chroot a systemd service, all you need to do is:
{
systemd.services.yourservice = {
description = "My Shiny Service";
wantedBy = [ "multi-user.target" ];
chroot.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 chroot.packages option. By
default (which uses the "full-apivfs"[3] 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 as well,
which is useful for most programs that use the system() C library call
to execute commands via shell. The shell providing /bin/sh is dash
instead of the default in NixOS (which is bash), because it's way more
lightweight and after all we're chrooting because we want to lower the
attack surface and it should be only used for "/bin/sh -c something".
Prior to submitting this here, I did a first implementation of this
outside[4] of nixpkgs, which duplicated the "pathSafeName" functionality
from systemd-lib.nix, just because it's only a single line.
However, I decided to just re-use the one from systemd here and
subsequently made it available when importing systemd-lib.nix, so that
the systemd-chroot implementation also benefits from fixes to that
functionality (which is now a proper function).
Unfortunately, we do have a few limitations as well. The first being
that DynamicUser doesn't work in conjunction with tmpfs, because it
already sets up a tmpfs in a different path and simply ignores the one
we define. We could probably solve this by detecting it and try to
bind-mount our paths to that different path whenever DynamicUser is
enabled.
The second limitation/issue is that RootDirectoryStartOnly doesn't work
right now, because it only affects the RootDirectory option and not the
individual bind mounts or our tmpfs. It would be helpful if systemd
would have a way to disable specific bind mounts as well or at least
have some way to ignore failures for the bind mounts/tmpfs setup.
Another 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.
[1]: https://github.com/headcounter/shabitica/blob/3bb01728a0237ad5e7/default.nix#L43-L62
[2]: https://github.com/aszlig/avonc/blob/dedf29e092481a33dc/nextcloud.nix#L103-L124
[3]: The reason this is called "full-apivfs" instead of just "full" is
to make room for a *real* "full" confinement mode, which is more
restrictive even.
[4]: https://github.com/aszlig/avonc/blob/92a20bece4df54625e/systemd-chroot.nix
Signed-off-by: aszlig <aszlig@nix.build>
2019-03-10 11:21:55 +00:00
|
|
|
export PATH=${lib.escapeShellArg "${pkgs.coreutils}/bin"}
|
2020-04-07 07:25:48 +01:00
|
|
|
${lib.escapeShellArg pkgs.runtimeShell} 2>&1
|
nixos: Add 'chroot' options to systemd.services
Currently, if you want to properly chroot a systemd service, you could
do it using BindReadOnlyPaths=/nix/store (which is not what I'd call
"properly", because the whole store is still accessible) or use a
separate derivation that gathers the runtime closure of the service you
want to chroot. The former is the easier method and there is also a
method directly offered by systemd, called ProtectSystem, which still
leaves the whole store accessible. The latter however is a bit more
involved, because you need to bind-mount each store path of the runtime
closure of the service you want to chroot.
This can be achieved using pkgs.closureInfo and a small derivation that
packs everything into a systemd unit, which later can be added to
systemd.packages. That's also what I did several times[1][2] in the
past.
However, this process got a bit tedious, so I decided that it would be
generally useful for NixOS, so this very implementation was born.
Now if you want to chroot a systemd service, all you need to do is:
{
systemd.services.yourservice = {
description = "My Shiny Service";
wantedBy = [ "multi-user.target" ];
chroot.enable = true;
serviceConfig.ExecStart = "${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 chroot.packages option. By
default (which uses the "full-apivfs"[3] 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 as well,
which is useful for most programs that use the system() C library call
to execute commands via shell. The shell providing /bin/sh is dash
instead of the default in NixOS (which is bash), because it's way more
lightweight and after all we're chrooting because we want to lower the
attack surface and it should be only used for "/bin/sh -c something".
Prior to submitting this here, I did a first implementation of this
outside[4] of nixpkgs, which duplicated the "pathSafeName" functionality
from systemd-lib.nix, just because it's only a single line.
However, I decided to just re-use the one from systemd here and
subsequently made it available when importing systemd-lib.nix, so that
the systemd-chroot implementation also benefits from fixes to that
functionality (which is now a proper function).
Unfortunately, we do have a few limitations as well. The first being
that DynamicUser doesn't work in conjunction with tmpfs, because it
already sets up a tmpfs in a different path and simply ignores the one
we define. We could probably solve this by detecting it and try to
bind-mount our paths to that different path whenever DynamicUser is
enabled.
The second limitation/issue is that RootDirectoryStartOnly doesn't work
right now, because it only affects the RootDirectory option and not the
individual bind mounts or our tmpfs. It would be helpful if systemd
would have a way to disable specific bind mounts as well or at least
have some way to ignore failures for the bind mounts/tmpfs setup.
Another 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.
[1]: https://github.com/headcounter/shabitica/blob/3bb01728a0237ad5e7/default.nix#L43-L62
[2]: https://github.com/aszlig/avonc/blob/dedf29e092481a33dc/nextcloud.nix#L103-L124
[3]: The reason this is called "full-apivfs" instead of just "full" is
to make room for a *real* "full" confinement mode, which is more
restrictive even.
[4]: https://github.com/aszlig/avonc/blob/92a20bece4df54625e/systemd-chroot.nix
Signed-off-by: aszlig <aszlig@nix.build>
2019-03-10 11:21:55 +00:00
|
|
|
echo "exit-status:$?"
|
|
|
|
'';
|
|
|
|
|
|
|
|
testClient = pkgs.writeScriptBin "chroot-exec" ''
|
2020-04-07 07:25:48 +01:00
|
|
|
#!${pkgs.runtimeShell} -e
|
nixos: Add 'chroot' options to systemd.services
Currently, if you want to properly chroot a systemd service, you could
do it using BindReadOnlyPaths=/nix/store (which is not what I'd call
"properly", because the whole store is still accessible) or use a
separate derivation that 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. That's also what I did several times[1][2] in the
past.
However, this process got a bit tedious, so I decided that it would be
generally useful for NixOS, so this very implementation was born.
Now if you want to chroot a systemd service, all you need to do is:
{
systemd.services.yourservice = {
description = "My Shiny Service";
wantedBy = [ "multi-user.target" ];
chroot.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 chroot.packages option. By
default (which uses the "full-apivfs"[3] 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 as well,
which is useful for most programs that use the system() C library call
to execute commands via shell. The shell providing /bin/sh is dash
instead of the default in NixOS (which is bash), because it's way more
lightweight and after all we're chrooting because we want to lower the
attack surface and it should be only used for "/bin/sh -c something".
Prior to submitting this here, I did a first implementation of this
outside[4] of nixpkgs, which duplicated the "pathSafeName" functionality
from systemd-lib.nix, just because it's only a single line.
However, I decided to just re-use the one from systemd here and
subsequently made it available when importing systemd-lib.nix, so that
the systemd-chroot implementation also benefits from fixes to that
functionality (which is now a proper function).
Unfortunately, we do have a few limitations as well. The first being
that DynamicUser doesn't work in conjunction with tmpfs, because it
already sets up a tmpfs in a different path and simply ignores the one
we define. We could probably solve this by detecting it and try to
bind-mount our paths to that different path whenever DynamicUser is
enabled.
The second limitation/issue is that RootDirectoryStartOnly doesn't work
right now, because it only affects the RootDirectory option and not the
individual bind mounts or our tmpfs. It would be helpful if systemd
would have a way to disable specific bind mounts as well or at least
have some way to ignore failures for the bind mounts/tmpfs setup.
Another 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.
[1]: https://github.com/headcounter/shabitica/blob/3bb01728a0237ad5e7/default.nix#L43-L62
[2]: https://github.com/aszlig/avonc/blob/dedf29e092481a33dc/nextcloud.nix#L103-L124
[3]: The reason this is called "full-apivfs" instead of just "full" is
to make room for a *real* "full" confinement mode, which is more
restrictive even.
[4]: https://github.com/aszlig/avonc/blob/92a20bece4df54625e/systemd-chroot.nix
Signed-off-by: aszlig <aszlig@nix.build>
2019-03-10 11:21:55 +00:00
|
|
|
output="$(echo "$@" | nc -NU "/run/test$(< /teststep).sock")"
|
|
|
|
ret="$(echo "$output" | sed -nre '$s/^exit-status:([0-9]+)$/\1/p')"
|
|
|
|
echo "$output" | head -n -1
|
|
|
|
exit "''${ret:-1}"
|
|
|
|
'';
|
|
|
|
|
2022-02-02 12:12:49 +00:00
|
|
|
mkTestStep = num: {
|
|
|
|
testScript,
|
|
|
|
config ? {},
|
|
|
|
serviceName ? "test${toString num}",
|
|
|
|
}: {
|
|
|
|
systemd.sockets.${serviceName} = {
|
nixos: Add 'chroot' options to systemd.services
Currently, if you want to properly chroot a systemd service, you could
do it using BindReadOnlyPaths=/nix/store (which is not what I'd call
"properly", because the whole store is still accessible) or use a
separate derivation that 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. That's also what I did several times[1][2] in the
past.
However, this process got a bit tedious, so I decided that it would be
generally useful for NixOS, so this very implementation was born.
Now if you want to chroot a systemd service, all you need to do is:
{
systemd.services.yourservice = {
description = "My Shiny Service";
wantedBy = [ "multi-user.target" ];
chroot.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 chroot.packages option. By
default (which uses the "full-apivfs"[3] 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 as well,
which is useful for most programs that use the system() C library call
to execute commands via shell. The shell providing /bin/sh is dash
instead of the default in NixOS (which is bash), because it's way more
lightweight and after all we're chrooting because we want to lower the
attack surface and it should be only used for "/bin/sh -c something".
Prior to submitting this here, I did a first implementation of this
outside[4] of nixpkgs, which duplicated the "pathSafeName" functionality
from systemd-lib.nix, just because it's only a single line.
However, I decided to just re-use the one from systemd here and
subsequently made it available when importing systemd-lib.nix, so that
the systemd-chroot implementation also benefits from fixes to that
functionality (which is now a proper function).
Unfortunately, we do have a few limitations as well. The first being
that DynamicUser doesn't work in conjunction with tmpfs, because it
already sets up a tmpfs in a different path and simply ignores the one
we define. We could probably solve this by detecting it and try to
bind-mount our paths to that different path whenever DynamicUser is
enabled.
The second limitation/issue is that RootDirectoryStartOnly doesn't work
right now, because it only affects the RootDirectory option and not the
individual bind mounts or our tmpfs. It would be helpful if systemd
would have a way to disable specific bind mounts as well or at least
have some way to ignore failures for the bind mounts/tmpfs setup.
Another 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.
[1]: https://github.com/headcounter/shabitica/blob/3bb01728a0237ad5e7/default.nix#L43-L62
[2]: https://github.com/aszlig/avonc/blob/dedf29e092481a33dc/nextcloud.nix#L103-L124
[3]: The reason this is called "full-apivfs" instead of just "full" is
to make room for a *real* "full" confinement mode, which is more
restrictive even.
[4]: https://github.com/aszlig/avonc/blob/92a20bece4df54625e/systemd-chroot.nix
Signed-off-by: aszlig <aszlig@nix.build>
2019-03-10 11:21:55 +00:00
|
|
|
description = "Socket for Test Service ${toString num}";
|
|
|
|
wantedBy = [ "sockets.target" ];
|
|
|
|
socketConfig.ListenStream = "/run/test${toString num}.sock";
|
|
|
|
socketConfig.Accept = true;
|
|
|
|
};
|
|
|
|
|
2022-02-02 12:12:49 +00:00
|
|
|
systemd.services."${serviceName}@" = {
|
2019-03-14 14:26:10 +00:00
|
|
|
description = "Confined Test Service ${toString num}";
|
|
|
|
confinement = (config.confinement or {}) // { enable = true; };
|
nixos: Add 'chroot' options to systemd.services
Currently, if you want to properly chroot a systemd service, you could
do it using BindReadOnlyPaths=/nix/store (which is not what I'd call
"properly", because the whole store is still accessible) or use a
separate derivation that gathers the runtime closure of the service you
want to chroot. The former is the easier method and there is also a
method directly offered by systemd, called ProtectSystem, which still
leaves the whole store accessible. The latter however is a bit more
involved, because you need to bind-mount each store path of the runtime
closure of the service you want to chroot.
This can be achieved using pkgs.closureInfo and a small derivation that
packs everything into a systemd unit, which later can be added to
systemd.packages. That's also what I did several times[1][2] in the
past.
However, this process got a bit tedious, so I decided that it would be
generally useful for NixOS, so this very implementation was born.
Now if you want to chroot a systemd service, all you need to do is:
{
systemd.services.yourservice = {
description = "My Shiny Service";
wantedBy = [ "multi-user.target" ];
chroot.enable = true;
serviceConfig.ExecStart = "${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 chroot.packages option. By
default (which uses the "full-apivfs"[3] 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 as well,
which is useful for most programs that use the system() C library call
to execute commands via shell. The shell providing /bin/sh is dash
instead of the default in NixOS (which is bash), because it's way more
lightweight and after all we're chrooting because we want to lower the
attack surface and it should be only used for "/bin/sh -c something".
Prior to submitting this here, I did a first implementation of this
outside[4] of nixpkgs, which duplicated the "pathSafeName" functionality
from systemd-lib.nix, just because it's only a single line.
However, I decided to just re-use the one from systemd here and
subsequently made it available when importing systemd-lib.nix, so that
the systemd-chroot implementation also benefits from fixes to that
functionality (which is now a proper function).
Unfortunately, we do have a few limitations as well. The first being
that DynamicUser doesn't work in conjunction with tmpfs, because it
already sets up a tmpfs in a different path and simply ignores the one
we define. We could probably solve this by detecting it and try to
bind-mount our paths to that different path whenever DynamicUser is
enabled.
The second limitation/issue is that RootDirectoryStartOnly doesn't work
right now, because it only affects the RootDirectory option and not the
individual bind mounts or our tmpfs. It would be helpful if systemd
would have a way to disable specific bind mounts as well or at least
have some way to ignore failures for the bind mounts/tmpfs setup.
Another 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.
[1]: https://github.com/headcounter/shabitica/blob/3bb01728a0237ad5e7/default.nix#L43-L62
[2]: https://github.com/aszlig/avonc/blob/dedf29e092481a33dc/nextcloud.nix#L103-L124
[3]: The reason this is called "full-apivfs" instead of just "full" is
to make room for a *real* "full" confinement mode, which is more
restrictive even.
[4]: https://github.com/aszlig/avonc/blob/92a20bece4df54625e/systemd-chroot.nix
Signed-off-by: aszlig <aszlig@nix.build>
2019-03-10 11:21:55 +00:00
|
|
|
serviceConfig = (config.serviceConfig or {}) // {
|
|
|
|
ExecStart = testServer;
|
|
|
|
StandardInput = "socket";
|
|
|
|
};
|
2019-03-14 14:26:10 +00:00
|
|
|
} // removeAttrs config [ "confinement" "serviceConfig" ];
|
nixos: Add 'chroot' options to systemd.services
Currently, if you want to properly chroot a systemd service, you could
do it using BindReadOnlyPaths=/nix/store (which is not what I'd call
"properly", because the whole store is still accessible) or use a
separate derivation that 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. That's also what I did several times[1][2] in the
past.
However, this process got a bit tedious, so I decided that it would be
generally useful for NixOS, so this very implementation was born.
Now if you want to chroot a systemd service, all you need to do is:
{
systemd.services.yourservice = {
description = "My Shiny Service";
wantedBy = [ "multi-user.target" ];
chroot.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 chroot.packages option. By
default (which uses the "full-apivfs"[3] 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 as well,
which is useful for most programs that use the system() C library call
to execute commands via shell. The shell providing /bin/sh is dash
instead of the default in NixOS (which is bash), because it's way more
lightweight and after all we're chrooting because we want to lower the
attack surface and it should be only used for "/bin/sh -c something".
Prior to submitting this here, I did a first implementation of this
outside[4] of nixpkgs, which duplicated the "pathSafeName" functionality
from systemd-lib.nix, just because it's only a single line.
However, I decided to just re-use the one from systemd here and
subsequently made it available when importing systemd-lib.nix, so that
the systemd-chroot implementation also benefits from fixes to that
functionality (which is now a proper function).
Unfortunately, we do have a few limitations as well. The first being
that DynamicUser doesn't work in conjunction with tmpfs, because it
already sets up a tmpfs in a different path and simply ignores the one
we define. We could probably solve this by detecting it and try to
bind-mount our paths to that different path whenever DynamicUser is
enabled.
The second limitation/issue is that RootDirectoryStartOnly doesn't work
right now, because it only affects the RootDirectory option and not the
individual bind mounts or our tmpfs. It would be helpful if systemd
would have a way to disable specific bind mounts as well or at least
have some way to ignore failures for the bind mounts/tmpfs setup.
Another 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.
[1]: https://github.com/headcounter/shabitica/blob/3bb01728a0237ad5e7/default.nix#L43-L62
[2]: https://github.com/aszlig/avonc/blob/dedf29e092481a33dc/nextcloud.nix#L103-L124
[3]: The reason this is called "full-apivfs" instead of just "full" is
to make room for a *real* "full" confinement mode, which is more
restrictive even.
[4]: https://github.com/aszlig/avonc/blob/92a20bece4df54625e/systemd-chroot.nix
Signed-off-by: aszlig <aszlig@nix.build>
2019-03-10 11:21:55 +00:00
|
|
|
|
2020-02-14 08:48:42 +00:00
|
|
|
__testSteps = lib.mkOrder num (''
|
|
|
|
machine.succeed("echo ${toString num} > /teststep")
|
|
|
|
'' + testScript);
|
nixos: Add 'chroot' options to systemd.services
Currently, if you want to properly chroot a systemd service, you could
do it using BindReadOnlyPaths=/nix/store (which is not what I'd call
"properly", because the whole store is still accessible) or use a
separate derivation that gathers the runtime closure of the service you
want to chroot. The former is the easier method and there is also a
method directly offered by systemd, called ProtectSystem, which still
leaves the whole store accessible. The latter however is a bit more
involved, because you need to bind-mount each store path of the runtime
closure of the service you want to chroot.
This can be achieved using pkgs.closureInfo and a small derivation that
packs everything into a systemd unit, which later can be added to
systemd.packages. That's also what I did several times[1][2] in the
past.
However, this process got a bit tedious, so I decided that it would be
generally useful for NixOS, so this very implementation was born.
Now if you want to chroot a systemd service, all you need to do is:
{
systemd.services.yourservice = {
description = "My Shiny Service";
wantedBy = [ "multi-user.target" ];
chroot.enable = true;
serviceConfig.ExecStart = "${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 chroot.packages option. By
default (which uses the "full-apivfs"[3] 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 as well,
which is useful for most programs that use the system() C library call
to execute commands via shell. The shell providing /bin/sh is dash
instead of the default in NixOS (which is bash), because it's way more
lightweight and after all we're chrooting because we want to lower the
attack surface and it should be only used for "/bin/sh -c something".
Prior to submitting this here, I did a first implementation of this
outside[4] of nixpkgs, which duplicated the "pathSafeName" functionality
from systemd-lib.nix, just because it's only a single line.
However, I decided to just re-use the one from systemd here and
subsequently made it available when importing systemd-lib.nix, so that
the systemd-chroot implementation also benefits from fixes to that
functionality (which is now a proper function).
Unfortunately, we do have a few limitations as well. The first being
that DynamicUser doesn't work in conjunction with tmpfs, because it
already sets up a tmpfs in a different path and simply ignores the one
we define. We could probably solve this by detecting it and try to
bind-mount our paths to that different path whenever DynamicUser is
enabled.
The second limitation/issue is that RootDirectoryStartOnly doesn't work
right now, because it only affects the RootDirectory option and not the
individual bind mounts or our tmpfs. It would be helpful if systemd
would have a way to disable specific bind mounts as well or at least
have some way to ignore failures for the bind mounts/tmpfs setup.
Another 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.
[1]: https://github.com/headcounter/shabitica/blob/3bb01728a0237ad5e7/default.nix#L43-L62
[2]: https://github.com/aszlig/avonc/blob/dedf29e092481a33dc/nextcloud.nix#L103-L124
[3]: The reason this is called "full-apivfs" instead of just "full" is
to make room for a *real* "full" confinement mode, which is more
restrictive even.
[4]: https://github.com/aszlig/avonc/blob/92a20bece4df54625e/systemd-chroot.nix
Signed-off-by: aszlig <aszlig@nix.build>
2019-03-10 11:21:55 +00:00
|
|
|
};
|
|
|
|
|
|
|
|
in {
|
|
|
|
imports = lib.imap1 mkTestStep [
|
2020-02-14 08:48:42 +00:00
|
|
|
{ config.confinement.mode = "chroot-only";
|
nixos: Add 'chroot' options to systemd.services
Currently, if you want to properly chroot a systemd service, you could
do it using BindReadOnlyPaths=/nix/store (which is not what I'd call
"properly", because the whole store is still accessible) or use a
separate derivation that 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. That's also what I did several times[1][2] in the
past.
However, this process got a bit tedious, so I decided that it would be
generally useful for NixOS, so this very implementation was born.
Now if you want to chroot a systemd service, all you need to do is:
{
systemd.services.yourservice = {
description = "My Shiny Service";
wantedBy = [ "multi-user.target" ];
chroot.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 chroot.packages option. By
default (which uses the "full-apivfs"[3] 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 as well,
which is useful for most programs that use the system() C library call
to execute commands via shell. The shell providing /bin/sh is dash
instead of the default in NixOS (which is bash), because it's way more
lightweight and after all we're chrooting because we want to lower the
attack surface and it should be only used for "/bin/sh -c something".
Prior to submitting this here, I did a first implementation of this
outside[4] of nixpkgs, which duplicated the "pathSafeName" functionality
from systemd-lib.nix, just because it's only a single line.
However, I decided to just re-use the one from systemd here and
subsequently made it available when importing systemd-lib.nix, so that
the systemd-chroot implementation also benefits from fixes to that
functionality (which is now a proper function).
Unfortunately, we do have a few limitations as well. The first being
that DynamicUser doesn't work in conjunction with tmpfs, because it
already sets up a tmpfs in a different path and simply ignores the one
we define. We could probably solve this by detecting it and try to
bind-mount our paths to that different path whenever DynamicUser is
enabled.
The second limitation/issue is that RootDirectoryStartOnly doesn't work
right now, because it only affects the RootDirectory option and not the
individual bind mounts or our tmpfs. It would be helpful if systemd
would have a way to disable specific bind mounts as well or at least
have some way to ignore failures for the bind mounts/tmpfs setup.
Another 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.
[1]: https://github.com/headcounter/shabitica/blob/3bb01728a0237ad5e7/default.nix#L43-L62
[2]: https://github.com/aszlig/avonc/blob/dedf29e092481a33dc/nextcloud.nix#L103-L124
[3]: The reason this is called "full-apivfs" instead of just "full" is
to make room for a *real* "full" confinement mode, which is more
restrictive even.
[4]: https://github.com/aszlig/avonc/blob/92a20bece4df54625e/systemd-chroot.nix
Signed-off-by: aszlig <aszlig@nix.build>
2019-03-10 11:21:55 +00:00
|
|
|
testScript = ''
|
2020-02-14 08:48:42 +00:00
|
|
|
with subtest("chroot-only confinement"):
|
systemd: 247.6 -> 249.4
This updates systemd to version v249.4 from version v247.6.
Besides the many new features that can be found in the upstream
repository they also introduced a bunch of cleanup which ended up
requiring a few more patches on our side.
a) 0022-core-Handle-lookup-paths-being-symlinks.patch:
The way symlinked units were handled was changed in such that the last
name of a unit file within one of the unit directories
(/run/systemd/system, /etc/systemd/system, ...) is used as the name
for the unit. Unfortunately that code didn't take into account that
the unit directories themselves could already be symlinks and thus
caused all our units to be recognized slightly different.
There is an upstream PR for this new patch:
https://github.com/systemd/systemd/pull/20479
b) The way the APIVFS is setup has been changed in such a way that we
now always have /run. This required a few changes to the
confinement tests which did assert that they didn't exist. Instead of
adding another patch we can just adopt the upstream behavior. An
empty /run doesn't seem harmful.
As part of this work I refactored the confinement test just a little
bit to allow better debugging of test failures. Previously it would
just fail at some point and it wasn't obvious which of the many
commands failed or what the unexpected string was. This should now be
more obvious.
c) Again related to the confinement tests the way a file was tested for
being accessible was optimized. Previously systemd would in some
situations open a file twice during that check. This was reduced to
one operation but required the procfs to be mounted in a units
namespace.
An upstream bug was filed and fixed. We are now carrying the
essential patch to fix that issue until it is backported to a new
release (likely only version 250). The good part about this story is
that upstream systemd now has a test case that looks very similar to
one of our confinement tests. Hopefully that will lead to less
friction in the long run.
https://github.com/systemd/systemd/issues/20514
https://github.com/systemd/systemd/pull/20515
d) Previously we could grep for dlopen( somewhat reliably but now
upstream started using a wrapper around dlopen that is most of the
time used with linebreaks. This makes using grep not ergonomic
anymore.
With this bump we are grepping for anything that looks like a
dynamic library name (in contrast to a dlopen(3) call) and replace
those instead. That seems more robust. Time will tell if this holds.
I tried using coccinelle to patch all those call sites using its
tooling but unfornately it does stumble upon the _cleanup_
annotations that are very common in the systemd code.
e) We now have some machinery for libbpf support in our systemd build.
That being said it doesn't actually work as generating some skeletons
doesn't work just yet. It fails with the below error message and is
disabled by default (in both minimal and the regular build).
> FAILED: src/core/bpf/socket_bind/socket-bind.skel.h
> /build/source/tools/build-bpf-skel.py --clang_exec /nix/store/x1bi2mkapk1m0zq2g02nr018qyjkdn7a-clang-wrapper-12.0.1/bin/clang --llvm_strip_exec /nix/store/zm0kqan9qc77x219yihmmisi9g3sg8ns-llvm-12.0.1/bin/llvm-strip --bpftool_exec /nix/store/l6dg8jlbh8qnqa58mshh3d8r6999dk0p-bpftools-5.13.11/bin/bpftool --arch x86_64 ../src/core/bpf/socket_bind/socket-bind.bpf.c src/core/bpf/socket_bind/socket-bind.skel.h
> libbpf: elf: socket_bind_bpf is not a valid eBPF object file
> Error: failed to open BPF object file: BPF object format invalid
> Traceback (most recent call last):
> File "/build/source/tools/build-bpf-skel.py", line 128, in <module>
> bpf_build(args)
> File "/build/source/tools/build-bpf-skel.py", line 92, in bpf_build
> gen_bpf_skeleton(bpftool_exec=args.bpftool_exec,
> File "/build/source/tools/build-bpf-skel.py", line 63, in gen_bpf_skeleton
> skel = subprocess.check_output(bpftool_args, universal_newlines=True)
> File "/nix/store/81lwy2hfqj4c1943b1x8a0qsivjhdhw9-python3-3.9.6/lib/python3.9/subprocess.py", line 424, in check_output
> return run(*popenargs, stdout=PIPE, timeout=timeout, check=True,
> File "/nix/store/81lwy2hfqj4c1943b1x8a0qsivjhdhw9-python3-3.9.6/lib/python3.9/subprocess.py", line 528, in run
> raise CalledProcessError(retcode, process.args,
> subprocess.CalledProcessError: Command '['/nix/store/l6dg8jlbh8qnqa58mshh3d8r6999dk0p-bpftools-5.13.11/bin/bpftool', 'g', 's', '../src/core/bpf/socket_bind/socket-bind.bpf.o']' returned non-zero exit status 255.
> [102/1457] Compiling C object src/journal/libjournal-core.a.p/journald-server.c.oapture output)put)ut)
> ninja: build stopped: subcommand failed.
f) We do now have support for TPM2 based disk encryption in our
systemd build. The actual bits and pieces to make use of that are
missing but there are various ongoing efforts in that direction.
There is also the story about systemd in our initrd to enable this
being used for root volumes. None of this will yet work out of the
box but we can start improving on that front.
g) FIDO2 support was added systemd and consequently we can now use
that. Just with TPM2 there hasn't been any integration work with
NixOS and instead this just adds that capability to work on that.
Co-Authored-By: Jörg Thalheim <joerg@thalheim.io>
2021-08-30 14:10:54 +01:00
|
|
|
paths = machine.succeed('chroot-exec ls -1 / | paste -sd,').strip()
|
|
|
|
assert_eq(paths, "bin,nix,run")
|
|
|
|
uid = machine.succeed('chroot-exec id -u').strip()
|
|
|
|
assert_eq(uid, "0")
|
|
|
|
machine.succeed("chroot-exec chown 65534 /bin")
|
nixos: Add 'chroot' options to systemd.services
Currently, if you want to properly chroot a systemd service, you could
do it using BindReadOnlyPaths=/nix/store (which is not what I'd call
"properly", because the whole store is still accessible) or use a
separate derivation that 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. That's also what I did several times[1][2] in the
past.
However, this process got a bit tedious, so I decided that it would be
generally useful for NixOS, so this very implementation was born.
Now if you want to chroot a systemd service, all you need to do is:
{
systemd.services.yourservice = {
description = "My Shiny Service";
wantedBy = [ "multi-user.target" ];
chroot.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 chroot.packages option. By
default (which uses the "full-apivfs"[3] 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 as well,
which is useful for most programs that use the system() C library call
to execute commands via shell. The shell providing /bin/sh is dash
instead of the default in NixOS (which is bash), because it's way more
lightweight and after all we're chrooting because we want to lower the
attack surface and it should be only used for "/bin/sh -c something".
Prior to submitting this here, I did a first implementation of this
outside[4] of nixpkgs, which duplicated the "pathSafeName" functionality
from systemd-lib.nix, just because it's only a single line.
However, I decided to just re-use the one from systemd here and
subsequently made it available when importing systemd-lib.nix, so that
the systemd-chroot implementation also benefits from fixes to that
functionality (which is now a proper function).
Unfortunately, we do have a few limitations as well. The first being
that DynamicUser doesn't work in conjunction with tmpfs, because it
already sets up a tmpfs in a different path and simply ignores the one
we define. We could probably solve this by detecting it and try to
bind-mount our paths to that different path whenever DynamicUser is
enabled.
The second limitation/issue is that RootDirectoryStartOnly doesn't work
right now, because it only affects the RootDirectory option and not the
individual bind mounts or our tmpfs. It would be helpful if systemd
would have a way to disable specific bind mounts as well or at least
have some way to ignore failures for the bind mounts/tmpfs setup.
Another 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.
[1]: https://github.com/headcounter/shabitica/blob/3bb01728a0237ad5e7/default.nix#L43-L62
[2]: https://github.com/aszlig/avonc/blob/dedf29e092481a33dc/nextcloud.nix#L103-L124
[3]: The reason this is called "full-apivfs" instead of just "full" is
to make room for a *real* "full" confinement mode, which is more
restrictive even.
[4]: https://github.com/aszlig/avonc/blob/92a20bece4df54625e/systemd-chroot.nix
Signed-off-by: aszlig <aszlig@nix.build>
2019-03-10 11:21:55 +00:00
|
|
|
'';
|
|
|
|
}
|
2020-02-14 08:48:42 +00:00
|
|
|
{ testScript = ''
|
|
|
|
with subtest("full confinement with APIVFS"):
|
systemd: 247.6 -> 249.4
This updates systemd to version v249.4 from version v247.6.
Besides the many new features that can be found in the upstream
repository they also introduced a bunch of cleanup which ended up
requiring a few more patches on our side.
a) 0022-core-Handle-lookup-paths-being-symlinks.patch:
The way symlinked units were handled was changed in such that the last
name of a unit file within one of the unit directories
(/run/systemd/system, /etc/systemd/system, ...) is used as the name
for the unit. Unfortunately that code didn't take into account that
the unit directories themselves could already be symlinks and thus
caused all our units to be recognized slightly different.
There is an upstream PR for this new patch:
https://github.com/systemd/systemd/pull/20479
b) The way the APIVFS is setup has been changed in such a way that we
now always have /run. This required a few changes to the
confinement tests which did assert that they didn't exist. Instead of
adding another patch we can just adopt the upstream behavior. An
empty /run doesn't seem harmful.
As part of this work I refactored the confinement test just a little
bit to allow better debugging of test failures. Previously it would
just fail at some point and it wasn't obvious which of the many
commands failed or what the unexpected string was. This should now be
more obvious.
c) Again related to the confinement tests the way a file was tested for
being accessible was optimized. Previously systemd would in some
situations open a file twice during that check. This was reduced to
one operation but required the procfs to be mounted in a units
namespace.
An upstream bug was filed and fixed. We are now carrying the
essential patch to fix that issue until it is backported to a new
release (likely only version 250). The good part about this story is
that upstream systemd now has a test case that looks very similar to
one of our confinement tests. Hopefully that will lead to less
friction in the long run.
https://github.com/systemd/systemd/issues/20514
https://github.com/systemd/systemd/pull/20515
d) Previously we could grep for dlopen( somewhat reliably but now
upstream started using a wrapper around dlopen that is most of the
time used with linebreaks. This makes using grep not ergonomic
anymore.
With this bump we are grepping for anything that looks like a
dynamic library name (in contrast to a dlopen(3) call) and replace
those instead. That seems more robust. Time will tell if this holds.
I tried using coccinelle to patch all those call sites using its
tooling but unfornately it does stumble upon the _cleanup_
annotations that are very common in the systemd code.
e) We now have some machinery for libbpf support in our systemd build.
That being said it doesn't actually work as generating some skeletons
doesn't work just yet. It fails with the below error message and is
disabled by default (in both minimal and the regular build).
> FAILED: src/core/bpf/socket_bind/socket-bind.skel.h
> /build/source/tools/build-bpf-skel.py --clang_exec /nix/store/x1bi2mkapk1m0zq2g02nr018qyjkdn7a-clang-wrapper-12.0.1/bin/clang --llvm_strip_exec /nix/store/zm0kqan9qc77x219yihmmisi9g3sg8ns-llvm-12.0.1/bin/llvm-strip --bpftool_exec /nix/store/l6dg8jlbh8qnqa58mshh3d8r6999dk0p-bpftools-5.13.11/bin/bpftool --arch x86_64 ../src/core/bpf/socket_bind/socket-bind.bpf.c src/core/bpf/socket_bind/socket-bind.skel.h
> libbpf: elf: socket_bind_bpf is not a valid eBPF object file
> Error: failed to open BPF object file: BPF object format invalid
> Traceback (most recent call last):
> File "/build/source/tools/build-bpf-skel.py", line 128, in <module>
> bpf_build(args)
> File "/build/source/tools/build-bpf-skel.py", line 92, in bpf_build
> gen_bpf_skeleton(bpftool_exec=args.bpftool_exec,
> File "/build/source/tools/build-bpf-skel.py", line 63, in gen_bpf_skeleton
> skel = subprocess.check_output(bpftool_args, universal_newlines=True)
> File "/nix/store/81lwy2hfqj4c1943b1x8a0qsivjhdhw9-python3-3.9.6/lib/python3.9/subprocess.py", line 424, in check_output
> return run(*popenargs, stdout=PIPE, timeout=timeout, check=True,
> File "/nix/store/81lwy2hfqj4c1943b1x8a0qsivjhdhw9-python3-3.9.6/lib/python3.9/subprocess.py", line 528, in run
> raise CalledProcessError(retcode, process.args,
> subprocess.CalledProcessError: Command '['/nix/store/l6dg8jlbh8qnqa58mshh3d8r6999dk0p-bpftools-5.13.11/bin/bpftool', 'g', 's', '../src/core/bpf/socket_bind/socket-bind.bpf.o']' returned non-zero exit status 255.
> [102/1457] Compiling C object src/journal/libjournal-core.a.p/journald-server.c.oapture output)put)ut)
> ninja: build stopped: subcommand failed.
f) We do now have support for TPM2 based disk encryption in our
systemd build. The actual bits and pieces to make use of that are
missing but there are various ongoing efforts in that direction.
There is also the story about systemd in our initrd to enable this
being used for root volumes. None of this will yet work out of the
box but we can start improving on that front.
g) FIDO2 support was added systemd and consequently we can now use
that. Just with TPM2 there hasn't been any integration work with
NixOS and instead this just adds that capability to work on that.
Co-Authored-By: Jörg Thalheim <joerg@thalheim.io>
2021-08-30 14:10:54 +01:00
|
|
|
machine.fail("chroot-exec ls -l /etc")
|
|
|
|
machine.fail("chroot-exec chown 65534 /bin")
|
|
|
|
assert_eq(machine.succeed('chroot-exec id -u').strip(), "0")
|
|
|
|
machine.succeed("chroot-exec chown 0 /bin")
|
nixos: Add 'chroot' options to systemd.services
Currently, if you want to properly chroot a systemd service, you could
do it using BindReadOnlyPaths=/nix/store (which is not what I'd call
"properly", because the whole store is still accessible) or use a
separate derivation that 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. That's also what I did several times[1][2] in the
past.
However, this process got a bit tedious, so I decided that it would be
generally useful for NixOS, so this very implementation was born.
Now if you want to chroot a systemd service, all you need to do is:
{
systemd.services.yourservice = {
description = "My Shiny Service";
wantedBy = [ "multi-user.target" ];
chroot.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 chroot.packages option. By
default (which uses the "full-apivfs"[3] 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 as well,
which is useful for most programs that use the system() C library call
to execute commands via shell. The shell providing /bin/sh is dash
instead of the default in NixOS (which is bash), because it's way more
lightweight and after all we're chrooting because we want to lower the
attack surface and it should be only used for "/bin/sh -c something".
Prior to submitting this here, I did a first implementation of this
outside[4] of nixpkgs, which duplicated the "pathSafeName" functionality
from systemd-lib.nix, just because it's only a single line.
However, I decided to just re-use the one from systemd here and
subsequently made it available when importing systemd-lib.nix, so that
the systemd-chroot implementation also benefits from fixes to that
functionality (which is now a proper function).
Unfortunately, we do have a few limitations as well. The first being
that DynamicUser doesn't work in conjunction with tmpfs, because it
already sets up a tmpfs in a different path and simply ignores the one
we define. We could probably solve this by detecting it and try to
bind-mount our paths to that different path whenever DynamicUser is
enabled.
The second limitation/issue is that RootDirectoryStartOnly doesn't work
right now, because it only affects the RootDirectory option and not the
individual bind mounts or our tmpfs. It would be helpful if systemd
would have a way to disable specific bind mounts as well or at least
have some way to ignore failures for the bind mounts/tmpfs setup.
Another 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.
[1]: https://github.com/headcounter/shabitica/blob/3bb01728a0237ad5e7/default.nix#L43-L62
[2]: https://github.com/aszlig/avonc/blob/dedf29e092481a33dc/nextcloud.nix#L103-L124
[3]: The reason this is called "full-apivfs" instead of just "full" is
to make room for a *real* "full" confinement mode, which is more
restrictive even.
[4]: https://github.com/aszlig/avonc/blob/92a20bece4df54625e/systemd-chroot.nix
Signed-off-by: aszlig <aszlig@nix.build>
2019-03-10 11:21:55 +00:00
|
|
|
'';
|
|
|
|
}
|
2020-02-14 08:48:42 +00:00
|
|
|
{ config.serviceConfig.BindReadOnlyPaths = [ "/etc" ];
|
nixos: Add 'chroot' options to systemd.services
Currently, if you want to properly chroot a systemd service, you could
do it using BindReadOnlyPaths=/nix/store (which is not what I'd call
"properly", because the whole store is still accessible) or use a
separate derivation that 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. That's also what I did several times[1][2] in the
past.
However, this process got a bit tedious, so I decided that it would be
generally useful for NixOS, so this very implementation was born.
Now if you want to chroot a systemd service, all you need to do is:
{
systemd.services.yourservice = {
description = "My Shiny Service";
wantedBy = [ "multi-user.target" ];
chroot.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 chroot.packages option. By
default (which uses the "full-apivfs"[3] 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 as well,
which is useful for most programs that use the system() C library call
to execute commands via shell. The shell providing /bin/sh is dash
instead of the default in NixOS (which is bash), because it's way more
lightweight and after all we're chrooting because we want to lower the
attack surface and it should be only used for "/bin/sh -c something".
Prior to submitting this here, I did a first implementation of this
outside[4] of nixpkgs, which duplicated the "pathSafeName" functionality
from systemd-lib.nix, just because it's only a single line.
However, I decided to just re-use the one from systemd here and
subsequently made it available when importing systemd-lib.nix, so that
the systemd-chroot implementation also benefits from fixes to that
functionality (which is now a proper function).
Unfortunately, we do have a few limitations as well. The first being
that DynamicUser doesn't work in conjunction with tmpfs, because it
already sets up a tmpfs in a different path and simply ignores the one
we define. We could probably solve this by detecting it and try to
bind-mount our paths to that different path whenever DynamicUser is
enabled.
The second limitation/issue is that RootDirectoryStartOnly doesn't work
right now, because it only affects the RootDirectory option and not the
individual bind mounts or our tmpfs. It would be helpful if systemd
would have a way to disable specific bind mounts as well or at least
have some way to ignore failures for the bind mounts/tmpfs setup.
Another 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.
[1]: https://github.com/headcounter/shabitica/blob/3bb01728a0237ad5e7/default.nix#L43-L62
[2]: https://github.com/aszlig/avonc/blob/dedf29e092481a33dc/nextcloud.nix#L103-L124
[3]: The reason this is called "full-apivfs" instead of just "full" is
to make room for a *real* "full" confinement mode, which is more
restrictive even.
[4]: https://github.com/aszlig/avonc/blob/92a20bece4df54625e/systemd-chroot.nix
Signed-off-by: aszlig <aszlig@nix.build>
2019-03-10 11:21:55 +00:00
|
|
|
testScript = ''
|
2020-02-14 08:48:42 +00:00
|
|
|
with subtest("check existence of bind-mounted /etc"):
|
systemd: 247.6 -> 249.4
This updates systemd to version v249.4 from version v247.6.
Besides the many new features that can be found in the upstream
repository they also introduced a bunch of cleanup which ended up
requiring a few more patches on our side.
a) 0022-core-Handle-lookup-paths-being-symlinks.patch:
The way symlinked units were handled was changed in such that the last
name of a unit file within one of the unit directories
(/run/systemd/system, /etc/systemd/system, ...) is used as the name
for the unit. Unfortunately that code didn't take into account that
the unit directories themselves could already be symlinks and thus
caused all our units to be recognized slightly different.
There is an upstream PR for this new patch:
https://github.com/systemd/systemd/pull/20479
b) The way the APIVFS is setup has been changed in such a way that we
now always have /run. This required a few changes to the
confinement tests which did assert that they didn't exist. Instead of
adding another patch we can just adopt the upstream behavior. An
empty /run doesn't seem harmful.
As part of this work I refactored the confinement test just a little
bit to allow better debugging of test failures. Previously it would
just fail at some point and it wasn't obvious which of the many
commands failed or what the unexpected string was. This should now be
more obvious.
c) Again related to the confinement tests the way a file was tested for
being accessible was optimized. Previously systemd would in some
situations open a file twice during that check. This was reduced to
one operation but required the procfs to be mounted in a units
namespace.
An upstream bug was filed and fixed. We are now carrying the
essential patch to fix that issue until it is backported to a new
release (likely only version 250). The good part about this story is
that upstream systemd now has a test case that looks very similar to
one of our confinement tests. Hopefully that will lead to less
friction in the long run.
https://github.com/systemd/systemd/issues/20514
https://github.com/systemd/systemd/pull/20515
d) Previously we could grep for dlopen( somewhat reliably but now
upstream started using a wrapper around dlopen that is most of the
time used with linebreaks. This makes using grep not ergonomic
anymore.
With this bump we are grepping for anything that looks like a
dynamic library name (in contrast to a dlopen(3) call) and replace
those instead. That seems more robust. Time will tell if this holds.
I tried using coccinelle to patch all those call sites using its
tooling but unfornately it does stumble upon the _cleanup_
annotations that are very common in the systemd code.
e) We now have some machinery for libbpf support in our systemd build.
That being said it doesn't actually work as generating some skeletons
doesn't work just yet. It fails with the below error message and is
disabled by default (in both minimal and the regular build).
> FAILED: src/core/bpf/socket_bind/socket-bind.skel.h
> /build/source/tools/build-bpf-skel.py --clang_exec /nix/store/x1bi2mkapk1m0zq2g02nr018qyjkdn7a-clang-wrapper-12.0.1/bin/clang --llvm_strip_exec /nix/store/zm0kqan9qc77x219yihmmisi9g3sg8ns-llvm-12.0.1/bin/llvm-strip --bpftool_exec /nix/store/l6dg8jlbh8qnqa58mshh3d8r6999dk0p-bpftools-5.13.11/bin/bpftool --arch x86_64 ../src/core/bpf/socket_bind/socket-bind.bpf.c src/core/bpf/socket_bind/socket-bind.skel.h
> libbpf: elf: socket_bind_bpf is not a valid eBPF object file
> Error: failed to open BPF object file: BPF object format invalid
> Traceback (most recent call last):
> File "/build/source/tools/build-bpf-skel.py", line 128, in <module>
> bpf_build(args)
> File "/build/source/tools/build-bpf-skel.py", line 92, in bpf_build
> gen_bpf_skeleton(bpftool_exec=args.bpftool_exec,
> File "/build/source/tools/build-bpf-skel.py", line 63, in gen_bpf_skeleton
> skel = subprocess.check_output(bpftool_args, universal_newlines=True)
> File "/nix/store/81lwy2hfqj4c1943b1x8a0qsivjhdhw9-python3-3.9.6/lib/python3.9/subprocess.py", line 424, in check_output
> return run(*popenargs, stdout=PIPE, timeout=timeout, check=True,
> File "/nix/store/81lwy2hfqj4c1943b1x8a0qsivjhdhw9-python3-3.9.6/lib/python3.9/subprocess.py", line 528, in run
> raise CalledProcessError(retcode, process.args,
> subprocess.CalledProcessError: Command '['/nix/store/l6dg8jlbh8qnqa58mshh3d8r6999dk0p-bpftools-5.13.11/bin/bpftool', 'g', 's', '../src/core/bpf/socket_bind/socket-bind.bpf.o']' returned non-zero exit status 255.
> [102/1457] Compiling C object src/journal/libjournal-core.a.p/journald-server.c.oapture output)put)ut)
> ninja: build stopped: subcommand failed.
f) We do now have support for TPM2 based disk encryption in our
systemd build. The actual bits and pieces to make use of that are
missing but there are various ongoing efforts in that direction.
There is also the story about systemd in our initrd to enable this
being used for root volumes. None of this will yet work out of the
box but we can start improving on that front.
g) FIDO2 support was added systemd and consequently we can now use
that. Just with TPM2 there hasn't been any integration work with
NixOS and instead this just adds that capability to work on that.
Co-Authored-By: Jörg Thalheim <joerg@thalheim.io>
2021-08-30 14:10:54 +01:00
|
|
|
passwd = machine.succeed('chroot-exec cat /etc/passwd').strip()
|
|
|
|
assert len(passwd) > 0, "/etc/passwd must not be empty"
|
nixos: Add 'chroot' options to systemd.services
Currently, if you want to properly chroot a systemd service, you could
do it using BindReadOnlyPaths=/nix/store (which is not what I'd call
"properly", because the whole store is still accessible) or use a
separate derivation that 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. That's also what I did several times[1][2] in the
past.
However, this process got a bit tedious, so I decided that it would be
generally useful for NixOS, so this very implementation was born.
Now if you want to chroot a systemd service, all you need to do is:
{
systemd.services.yourservice = {
description = "My Shiny Service";
wantedBy = [ "multi-user.target" ];
chroot.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 chroot.packages option. By
default (which uses the "full-apivfs"[3] 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 as well,
which is useful for most programs that use the system() C library call
to execute commands via shell. The shell providing /bin/sh is dash
instead of the default in NixOS (which is bash), because it's way more
lightweight and after all we're chrooting because we want to lower the
attack surface and it should be only used for "/bin/sh -c something".
Prior to submitting this here, I did a first implementation of this
outside[4] of nixpkgs, which duplicated the "pathSafeName" functionality
from systemd-lib.nix, just because it's only a single line.
However, I decided to just re-use the one from systemd here and
subsequently made it available when importing systemd-lib.nix, so that
the systemd-chroot implementation also benefits from fixes to that
functionality (which is now a proper function).
Unfortunately, we do have a few limitations as well. The first being
that DynamicUser doesn't work in conjunction with tmpfs, because it
already sets up a tmpfs in a different path and simply ignores the one
we define. We could probably solve this by detecting it and try to
bind-mount our paths to that different path whenever DynamicUser is
enabled.
The second limitation/issue is that RootDirectoryStartOnly doesn't work
right now, because it only affects the RootDirectory option and not the
individual bind mounts or our tmpfs. It would be helpful if systemd
would have a way to disable specific bind mounts as well or at least
have some way to ignore failures for the bind mounts/tmpfs setup.
Another 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.
[1]: https://github.com/headcounter/shabitica/blob/3bb01728a0237ad5e7/default.nix#L43-L62
[2]: https://github.com/aszlig/avonc/blob/dedf29e092481a33dc/nextcloud.nix#L103-L124
[3]: The reason this is called "full-apivfs" instead of just "full" is
to make room for a *real* "full" confinement mode, which is more
restrictive even.
[4]: https://github.com/aszlig/avonc/blob/92a20bece4df54625e/systemd-chroot.nix
Signed-off-by: aszlig <aszlig@nix.build>
2019-03-10 11:21:55 +00:00
|
|
|
'';
|
|
|
|
}
|
2020-02-14 08:48:42 +00:00
|
|
|
{ config.serviceConfig.User = "chroot-testuser";
|
nixos: Add 'chroot' options to systemd.services
Currently, if you want to properly chroot a systemd service, you could
do it using BindReadOnlyPaths=/nix/store (which is not what I'd call
"properly", because the whole store is still accessible) or use a
separate derivation that 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. That's also what I did several times[1][2] in the
past.
However, this process got a bit tedious, so I decided that it would be
generally useful for NixOS, so this very implementation was born.
Now if you want to chroot a systemd service, all you need to do is:
{
systemd.services.yourservice = {
description = "My Shiny Service";
wantedBy = [ "multi-user.target" ];
chroot.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 chroot.packages option. By
default (which uses the "full-apivfs"[3] 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 as well,
which is useful for most programs that use the system() C library call
to execute commands via shell. The shell providing /bin/sh is dash
instead of the default in NixOS (which is bash), because it's way more
lightweight and after all we're chrooting because we want to lower the
attack surface and it should be only used for "/bin/sh -c something".
Prior to submitting this here, I did a first implementation of this
outside[4] of nixpkgs, which duplicated the "pathSafeName" functionality
from systemd-lib.nix, just because it's only a single line.
However, I decided to just re-use the one from systemd here and
subsequently made it available when importing systemd-lib.nix, so that
the systemd-chroot implementation also benefits from fixes to that
functionality (which is now a proper function).
Unfortunately, we do have a few limitations as well. The first being
that DynamicUser doesn't work in conjunction with tmpfs, because it
already sets up a tmpfs in a different path and simply ignores the one
we define. We could probably solve this by detecting it and try to
bind-mount our paths to that different path whenever DynamicUser is
enabled.
The second limitation/issue is that RootDirectoryStartOnly doesn't work
right now, because it only affects the RootDirectory option and not the
individual bind mounts or our tmpfs. It would be helpful if systemd
would have a way to disable specific bind mounts as well or at least
have some way to ignore failures for the bind mounts/tmpfs setup.
Another 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.
[1]: https://github.com/headcounter/shabitica/blob/3bb01728a0237ad5e7/default.nix#L43-L62
[2]: https://github.com/aszlig/avonc/blob/dedf29e092481a33dc/nextcloud.nix#L103-L124
[3]: The reason this is called "full-apivfs" instead of just "full" is
to make room for a *real* "full" confinement mode, which is more
restrictive even.
[4]: https://github.com/aszlig/avonc/blob/92a20bece4df54625e/systemd-chroot.nix
Signed-off-by: aszlig <aszlig@nix.build>
2019-03-10 11:21:55 +00:00
|
|
|
config.serviceConfig.Group = "chroot-testgroup";
|
|
|
|
testScript = ''
|
2020-02-14 08:48:42 +00:00
|
|
|
with subtest("check if User/Group really runs as non-root"):
|
|
|
|
machine.succeed("chroot-exec ls -l /dev")
|
systemd: 247.6 -> 249.4
This updates systemd to version v249.4 from version v247.6.
Besides the many new features that can be found in the upstream
repository they also introduced a bunch of cleanup which ended up
requiring a few more patches on our side.
a) 0022-core-Handle-lookup-paths-being-symlinks.patch:
The way symlinked units were handled was changed in such that the last
name of a unit file within one of the unit directories
(/run/systemd/system, /etc/systemd/system, ...) is used as the name
for the unit. Unfortunately that code didn't take into account that
the unit directories themselves could already be symlinks and thus
caused all our units to be recognized slightly different.
There is an upstream PR for this new patch:
https://github.com/systemd/systemd/pull/20479
b) The way the APIVFS is setup has been changed in such a way that we
now always have /run. This required a few changes to the
confinement tests which did assert that they didn't exist. Instead of
adding another patch we can just adopt the upstream behavior. An
empty /run doesn't seem harmful.
As part of this work I refactored the confinement test just a little
bit to allow better debugging of test failures. Previously it would
just fail at some point and it wasn't obvious which of the many
commands failed or what the unexpected string was. This should now be
more obvious.
c) Again related to the confinement tests the way a file was tested for
being accessible was optimized. Previously systemd would in some
situations open a file twice during that check. This was reduced to
one operation but required the procfs to be mounted in a units
namespace.
An upstream bug was filed and fixed. We are now carrying the
essential patch to fix that issue until it is backported to a new
release (likely only version 250). The good part about this story is
that upstream systemd now has a test case that looks very similar to
one of our confinement tests. Hopefully that will lead to less
friction in the long run.
https://github.com/systemd/systemd/issues/20514
https://github.com/systemd/systemd/pull/20515
d) Previously we could grep for dlopen( somewhat reliably but now
upstream started using a wrapper around dlopen that is most of the
time used with linebreaks. This makes using grep not ergonomic
anymore.
With this bump we are grepping for anything that looks like a
dynamic library name (in contrast to a dlopen(3) call) and replace
those instead. That seems more robust. Time will tell if this holds.
I tried using coccinelle to patch all those call sites using its
tooling but unfornately it does stumble upon the _cleanup_
annotations that are very common in the systemd code.
e) We now have some machinery for libbpf support in our systemd build.
That being said it doesn't actually work as generating some skeletons
doesn't work just yet. It fails with the below error message and is
disabled by default (in both minimal and the regular build).
> FAILED: src/core/bpf/socket_bind/socket-bind.skel.h
> /build/source/tools/build-bpf-skel.py --clang_exec /nix/store/x1bi2mkapk1m0zq2g02nr018qyjkdn7a-clang-wrapper-12.0.1/bin/clang --llvm_strip_exec /nix/store/zm0kqan9qc77x219yihmmisi9g3sg8ns-llvm-12.0.1/bin/llvm-strip --bpftool_exec /nix/store/l6dg8jlbh8qnqa58mshh3d8r6999dk0p-bpftools-5.13.11/bin/bpftool --arch x86_64 ../src/core/bpf/socket_bind/socket-bind.bpf.c src/core/bpf/socket_bind/socket-bind.skel.h
> libbpf: elf: socket_bind_bpf is not a valid eBPF object file
> Error: failed to open BPF object file: BPF object format invalid
> Traceback (most recent call last):
> File "/build/source/tools/build-bpf-skel.py", line 128, in <module>
> bpf_build(args)
> File "/build/source/tools/build-bpf-skel.py", line 92, in bpf_build
> gen_bpf_skeleton(bpftool_exec=args.bpftool_exec,
> File "/build/source/tools/build-bpf-skel.py", line 63, in gen_bpf_skeleton
> skel = subprocess.check_output(bpftool_args, universal_newlines=True)
> File "/nix/store/81lwy2hfqj4c1943b1x8a0qsivjhdhw9-python3-3.9.6/lib/python3.9/subprocess.py", line 424, in check_output
> return run(*popenargs, stdout=PIPE, timeout=timeout, check=True,
> File "/nix/store/81lwy2hfqj4c1943b1x8a0qsivjhdhw9-python3-3.9.6/lib/python3.9/subprocess.py", line 528, in run
> raise CalledProcessError(retcode, process.args,
> subprocess.CalledProcessError: Command '['/nix/store/l6dg8jlbh8qnqa58mshh3d8r6999dk0p-bpftools-5.13.11/bin/bpftool', 'g', 's', '../src/core/bpf/socket_bind/socket-bind.bpf.o']' returned non-zero exit status 255.
> [102/1457] Compiling C object src/journal/libjournal-core.a.p/journald-server.c.oapture output)put)ut)
> ninja: build stopped: subcommand failed.
f) We do now have support for TPM2 based disk encryption in our
systemd build. The actual bits and pieces to make use of that are
missing but there are various ongoing efforts in that direction.
There is also the story about systemd in our initrd to enable this
being used for root volumes. None of this will yet work out of the
box but we can start improving on that front.
g) FIDO2 support was added systemd and consequently we can now use
that. Just with TPM2 there hasn't been any integration work with
NixOS and instead this just adds that capability to work on that.
Co-Authored-By: Jörg Thalheim <joerg@thalheim.io>
2021-08-30 14:10:54 +01:00
|
|
|
uid = machine.succeed('chroot-exec id -u').strip()
|
|
|
|
assert uid != "0", "UID of chroot-testuser shouldn't be 0"
|
2020-02-14 08:48:42 +00:00
|
|
|
machine.fail("chroot-exec touch /bin/test")
|
nixos: Add 'chroot' options to systemd.services
Currently, if you want to properly chroot a systemd service, you could
do it using BindReadOnlyPaths=/nix/store (which is not what I'd call
"properly", because the whole store is still accessible) or use a
separate derivation that 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. That's also what I did several times[1][2] in the
past.
However, this process got a bit tedious, so I decided that it would be
generally useful for NixOS, so this very implementation was born.
Now if you want to chroot a systemd service, all you need to do is:
{
systemd.services.yourservice = {
description = "My Shiny Service";
wantedBy = [ "multi-user.target" ];
chroot.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 chroot.packages option. By
default (which uses the "full-apivfs"[3] 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 as well,
which is useful for most programs that use the system() C library call
to execute commands via shell. The shell providing /bin/sh is dash
instead of the default in NixOS (which is bash), because it's way more
lightweight and after all we're chrooting because we want to lower the
attack surface and it should be only used for "/bin/sh -c something".
Prior to submitting this here, I did a first implementation of this
outside[4] of nixpkgs, which duplicated the "pathSafeName" functionality
from systemd-lib.nix, just because it's only a single line.
However, I decided to just re-use the one from systemd here and
subsequently made it available when importing systemd-lib.nix, so that
the systemd-chroot implementation also benefits from fixes to that
functionality (which is now a proper function).
Unfortunately, we do have a few limitations as well. The first being
that DynamicUser doesn't work in conjunction with tmpfs, because it
already sets up a tmpfs in a different path and simply ignores the one
we define. We could probably solve this by detecting it and try to
bind-mount our paths to that different path whenever DynamicUser is
enabled.
The second limitation/issue is that RootDirectoryStartOnly doesn't work
right now, because it only affects the RootDirectory option and not the
individual bind mounts or our tmpfs. It would be helpful if systemd
would have a way to disable specific bind mounts as well or at least
have some way to ignore failures for the bind mounts/tmpfs setup.
Another 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.
[1]: https://github.com/headcounter/shabitica/blob/3bb01728a0237ad5e7/default.nix#L43-L62
[2]: https://github.com/aszlig/avonc/blob/dedf29e092481a33dc/nextcloud.nix#L103-L124
[3]: The reason this is called "full-apivfs" instead of just "full" is
to make room for a *real* "full" confinement mode, which is more
restrictive even.
[4]: https://github.com/aszlig/avonc/blob/92a20bece4df54625e/systemd-chroot.nix
Signed-off-by: aszlig <aszlig@nix.build>
2019-03-10 11:21:55 +00:00
|
|
|
'';
|
|
|
|
}
|
|
|
|
(let
|
|
|
|
symlink = pkgs.runCommand "symlink" {
|
|
|
|
target = pkgs.writeText "symlink-target" "got me\n";
|
|
|
|
} "ln -s \"$target\" \"$out\"";
|
|
|
|
in {
|
2019-03-14 14:26:10 +00:00
|
|
|
config.confinement.packages = lib.singleton symlink;
|
nixos: Add 'chroot' options to systemd.services
Currently, if you want to properly chroot a systemd service, you could
do it using BindReadOnlyPaths=/nix/store (which is not what I'd call
"properly", because the whole store is still accessible) or use a
separate derivation that gathers the runtime closure of the service you
want to chroot. The former is the easier method and there is also a
method directly offered by systemd, called ProtectSystem, which still
leaves the whole store accessible. The latter however is a bit more
involved, because you need to bind-mount each store path of the runtime
closure of the service you want to chroot.
This can be achieved using pkgs.closureInfo and a small derivation that
packs everything into a systemd unit, which later can be added to
systemd.packages. That's also what I did several times[1][2] in the
past.
However, this process got a bit tedious, so I decided that it would be
generally useful for NixOS, so this very implementation was born.
Now if you want to chroot a systemd service, all you need to do is:
{
systemd.services.yourservice = {
description = "My Shiny Service";
wantedBy = [ "multi-user.target" ];
chroot.enable = true;
serviceConfig.ExecStart = "${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 chroot.packages option. By
default (which uses the "full-apivfs"[3] 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 as well,
which is useful for most programs that use the system() C library call
to execute commands via shell. The shell providing /bin/sh is dash
instead of the default in NixOS (which is bash), because it's way more
lightweight and after all we're chrooting because we want to lower the
attack surface and it should be only used for "/bin/sh -c something".
Prior to submitting this here, I did a first implementation of this
outside[4] of nixpkgs, which duplicated the "pathSafeName" functionality
from systemd-lib.nix, just because it's only a single line.
However, I decided to just re-use the one from systemd here and
subsequently made it available when importing systemd-lib.nix, so that
the systemd-chroot implementation also benefits from fixes to that
functionality (which is now a proper function).
Unfortunately, we do have a few limitations as well. The first being
that DynamicUser doesn't work in conjunction with tmpfs, because it
already sets up a tmpfs in a different path and simply ignores the one
we define. We could probably solve this by detecting it and try to
bind-mount our paths to that different path whenever DynamicUser is
enabled.
The second limitation/issue is that RootDirectoryStartOnly doesn't work
right now, because it only affects the RootDirectory option and not the
individual bind mounts or our tmpfs. It would be helpful if systemd
would have a way to disable specific bind mounts as well or at least
have some way to ignore failures for the bind mounts/tmpfs setup.
Another 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.
[1]: https://github.com/headcounter/shabitica/blob/3bb01728a0237ad5e7/default.nix#L43-L62
[2]: https://github.com/aszlig/avonc/blob/dedf29e092481a33dc/nextcloud.nix#L103-L124
[3]: The reason this is called "full-apivfs" instead of just "full" is
to make room for a *real* "full" confinement mode, which is more
restrictive even.
[4]: https://github.com/aszlig/avonc/blob/92a20bece4df54625e/systemd-chroot.nix
Signed-off-by: aszlig <aszlig@nix.build>
2019-03-10 11:21:55 +00:00
|
|
|
testScript = ''
|
2020-02-14 08:48:42 +00:00
|
|
|
with subtest("check if symlinks are properly bind-mounted"):
|
|
|
|
machine.fail("chroot-exec test -e /etc")
|
systemd: 247.6 -> 249.4
This updates systemd to version v249.4 from version v247.6.
Besides the many new features that can be found in the upstream
repository they also introduced a bunch of cleanup which ended up
requiring a few more patches on our side.
a) 0022-core-Handle-lookup-paths-being-symlinks.patch:
The way symlinked units were handled was changed in such that the last
name of a unit file within one of the unit directories
(/run/systemd/system, /etc/systemd/system, ...) is used as the name
for the unit. Unfortunately that code didn't take into account that
the unit directories themselves could already be symlinks and thus
caused all our units to be recognized slightly different.
There is an upstream PR for this new patch:
https://github.com/systemd/systemd/pull/20479
b) The way the APIVFS is setup has been changed in such a way that we
now always have /run. This required a few changes to the
confinement tests which did assert that they didn't exist. Instead of
adding another patch we can just adopt the upstream behavior. An
empty /run doesn't seem harmful.
As part of this work I refactored the confinement test just a little
bit to allow better debugging of test failures. Previously it would
just fail at some point and it wasn't obvious which of the many
commands failed or what the unexpected string was. This should now be
more obvious.
c) Again related to the confinement tests the way a file was tested for
being accessible was optimized. Previously systemd would in some
situations open a file twice during that check. This was reduced to
one operation but required the procfs to be mounted in a units
namespace.
An upstream bug was filed and fixed. We are now carrying the
essential patch to fix that issue until it is backported to a new
release (likely only version 250). The good part about this story is
that upstream systemd now has a test case that looks very similar to
one of our confinement tests. Hopefully that will lead to less
friction in the long run.
https://github.com/systemd/systemd/issues/20514
https://github.com/systemd/systemd/pull/20515
d) Previously we could grep for dlopen( somewhat reliably but now
upstream started using a wrapper around dlopen that is most of the
time used with linebreaks. This makes using grep not ergonomic
anymore.
With this bump we are grepping for anything that looks like a
dynamic library name (in contrast to a dlopen(3) call) and replace
those instead. That seems more robust. Time will tell if this holds.
I tried using coccinelle to patch all those call sites using its
tooling but unfornately it does stumble upon the _cleanup_
annotations that are very common in the systemd code.
e) We now have some machinery for libbpf support in our systemd build.
That being said it doesn't actually work as generating some skeletons
doesn't work just yet. It fails with the below error message and is
disabled by default (in both minimal and the regular build).
> FAILED: src/core/bpf/socket_bind/socket-bind.skel.h
> /build/source/tools/build-bpf-skel.py --clang_exec /nix/store/x1bi2mkapk1m0zq2g02nr018qyjkdn7a-clang-wrapper-12.0.1/bin/clang --llvm_strip_exec /nix/store/zm0kqan9qc77x219yihmmisi9g3sg8ns-llvm-12.0.1/bin/llvm-strip --bpftool_exec /nix/store/l6dg8jlbh8qnqa58mshh3d8r6999dk0p-bpftools-5.13.11/bin/bpftool --arch x86_64 ../src/core/bpf/socket_bind/socket-bind.bpf.c src/core/bpf/socket_bind/socket-bind.skel.h
> libbpf: elf: socket_bind_bpf is not a valid eBPF object file
> Error: failed to open BPF object file: BPF object format invalid
> Traceback (most recent call last):
> File "/build/source/tools/build-bpf-skel.py", line 128, in <module>
> bpf_build(args)
> File "/build/source/tools/build-bpf-skel.py", line 92, in bpf_build
> gen_bpf_skeleton(bpftool_exec=args.bpftool_exec,
> File "/build/source/tools/build-bpf-skel.py", line 63, in gen_bpf_skeleton
> skel = subprocess.check_output(bpftool_args, universal_newlines=True)
> File "/nix/store/81lwy2hfqj4c1943b1x8a0qsivjhdhw9-python3-3.9.6/lib/python3.9/subprocess.py", line 424, in check_output
> return run(*popenargs, stdout=PIPE, timeout=timeout, check=True,
> File "/nix/store/81lwy2hfqj4c1943b1x8a0qsivjhdhw9-python3-3.9.6/lib/python3.9/subprocess.py", line 528, in run
> raise CalledProcessError(retcode, process.args,
> subprocess.CalledProcessError: Command '['/nix/store/l6dg8jlbh8qnqa58mshh3d8r6999dk0p-bpftools-5.13.11/bin/bpftool', 'g', 's', '../src/core/bpf/socket_bind/socket-bind.bpf.o']' returned non-zero exit status 255.
> [102/1457] Compiling C object src/journal/libjournal-core.a.p/journald-server.c.oapture output)put)ut)
> ninja: build stopped: subcommand failed.
f) We do now have support for TPM2 based disk encryption in our
systemd build. The actual bits and pieces to make use of that are
missing but there are various ongoing efforts in that direction.
There is also the story about systemd in our initrd to enable this
being used for root volumes. None of this will yet work out of the
box but we can start improving on that front.
g) FIDO2 support was added systemd and consequently we can now use
that. Just with TPM2 there hasn't been any integration work with
NixOS and instead this just adds that capability to work on that.
Co-Authored-By: Jörg Thalheim <joerg@thalheim.io>
2021-08-30 14:10:54 +01:00
|
|
|
text = machine.succeed('chroot-exec cat ${symlink}').strip()
|
|
|
|
assert_eq(text, "got me")
|
nixos: Add 'chroot' options to systemd.services
Currently, if you want to properly chroot a systemd service, you could
do it using BindReadOnlyPaths=/nix/store (which is not what I'd call
"properly", because the whole store is still accessible) or use a
separate derivation that gathers the runtime closure of the service you
want to chroot. The former is the easier method and there is also a
method directly offered by systemd, called ProtectSystem, which still
leaves the whole store accessible. The latter however is a bit more
involved, because you need to bind-mount each store path of the runtime
closure of the service you want to chroot.
This can be achieved using pkgs.closureInfo and a small derivation that
packs everything into a systemd unit, which later can be added to
systemd.packages. That's also what I did several times[1][2] in the
past.
However, this process got a bit tedious, so I decided that it would be
generally useful for NixOS, so this very implementation was born.
Now if you want to chroot a systemd service, all you need to do is:
{
systemd.services.yourservice = {
description = "My Shiny Service";
wantedBy = [ "multi-user.target" ];
chroot.enable = true;
serviceConfig.ExecStart = "${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 chroot.packages option. By
default (which uses the "full-apivfs"[3] 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 as well,
which is useful for most programs that use the system() C library call
to execute commands via shell. The shell providing /bin/sh is dash
instead of the default in NixOS (which is bash), because it's way more
lightweight and after all we're chrooting because we want to lower the
attack surface and it should be only used for "/bin/sh -c something".
Prior to submitting this here, I did a first implementation of this
outside[4] of nixpkgs, which duplicated the "pathSafeName" functionality
from systemd-lib.nix, just because it's only a single line.
However, I decided to just re-use the one from systemd here and
subsequently made it available when importing systemd-lib.nix, so that
the systemd-chroot implementation also benefits from fixes to that
functionality (which is now a proper function).
Unfortunately, we do have a few limitations as well. The first being
that DynamicUser doesn't work in conjunction with tmpfs, because it
already sets up a tmpfs in a different path and simply ignores the one
we define. We could probably solve this by detecting it and try to
bind-mount our paths to that different path whenever DynamicUser is
enabled.
The second limitation/issue is that RootDirectoryStartOnly doesn't work
right now, because it only affects the RootDirectory option and not the
individual bind mounts or our tmpfs. It would be helpful if systemd
would have a way to disable specific bind mounts as well or at least
have some way to ignore failures for the bind mounts/tmpfs setup.
Another 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.
[1]: https://github.com/headcounter/shabitica/blob/3bb01728a0237ad5e7/default.nix#L43-L62
[2]: https://github.com/aszlig/avonc/blob/dedf29e092481a33dc/nextcloud.nix#L103-L124
[3]: The reason this is called "full-apivfs" instead of just "full" is
to make room for a *real* "full" confinement mode, which is more
restrictive even.
[4]: https://github.com/aszlig/avonc/blob/92a20bece4df54625e/systemd-chroot.nix
Signed-off-by: aszlig <aszlig@nix.build>
2019-03-10 11:21:55 +00:00
|
|
|
'';
|
|
|
|
})
|
2020-02-14 08:48:42 +00:00
|
|
|
{ config.serviceConfig.User = "chroot-testuser";
|
nixos: Add 'chroot' options to systemd.services
Currently, if you want to properly chroot a systemd service, you could
do it using BindReadOnlyPaths=/nix/store (which is not what I'd call
"properly", because the whole store is still accessible) or use a
separate derivation that 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. That's also what I did several times[1][2] in the
past.
However, this process got a bit tedious, so I decided that it would be
generally useful for NixOS, so this very implementation was born.
Now if you want to chroot a systemd service, all you need to do is:
{
systemd.services.yourservice = {
description = "My Shiny Service";
wantedBy = [ "multi-user.target" ];
chroot.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 chroot.packages option. By
default (which uses the "full-apivfs"[3] 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 as well,
which is useful for most programs that use the system() C library call
to execute commands via shell. The shell providing /bin/sh is dash
instead of the default in NixOS (which is bash), because it's way more
lightweight and after all we're chrooting because we want to lower the
attack surface and it should be only used for "/bin/sh -c something".
Prior to submitting this here, I did a first implementation of this
outside[4] of nixpkgs, which duplicated the "pathSafeName" functionality
from systemd-lib.nix, just because it's only a single line.
However, I decided to just re-use the one from systemd here and
subsequently made it available when importing systemd-lib.nix, so that
the systemd-chroot implementation also benefits from fixes to that
functionality (which is now a proper function).
Unfortunately, we do have a few limitations as well. The first being
that DynamicUser doesn't work in conjunction with tmpfs, because it
already sets up a tmpfs in a different path and simply ignores the one
we define. We could probably solve this by detecting it and try to
bind-mount our paths to that different path whenever DynamicUser is
enabled.
The second limitation/issue is that RootDirectoryStartOnly doesn't work
right now, because it only affects the RootDirectory option and not the
individual bind mounts or our tmpfs. It would be helpful if systemd
would have a way to disable specific bind mounts as well or at least
have some way to ignore failures for the bind mounts/tmpfs setup.
Another 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.
[1]: https://github.com/headcounter/shabitica/blob/3bb01728a0237ad5e7/default.nix#L43-L62
[2]: https://github.com/aszlig/avonc/blob/dedf29e092481a33dc/nextcloud.nix#L103-L124
[3]: The reason this is called "full-apivfs" instead of just "full" is
to make room for a *real* "full" confinement mode, which is more
restrictive even.
[4]: https://github.com/aszlig/avonc/blob/92a20bece4df54625e/systemd-chroot.nix
Signed-off-by: aszlig <aszlig@nix.build>
2019-03-10 11:21:55 +00:00
|
|
|
config.serviceConfig.Group = "chroot-testgroup";
|
|
|
|
config.serviceConfig.StateDirectory = "testme";
|
|
|
|
testScript = ''
|
2020-02-14 08:48:42 +00:00
|
|
|
with subtest("check if StateDirectory works"):
|
|
|
|
machine.succeed("chroot-exec touch /tmp/canary")
|
|
|
|
machine.succeed('chroot-exec "echo works > /var/lib/testme/foo"')
|
|
|
|
machine.succeed('test "$(< /var/lib/testme/foo)" = works')
|
|
|
|
machine.succeed("test ! -e /tmp/canary")
|
nixos: Add 'chroot' options to systemd.services
Currently, if you want to properly chroot a systemd service, you could
do it using BindReadOnlyPaths=/nix/store (which is not what I'd call
"properly", because the whole store is still accessible) or use a
separate derivation that 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. That's also what I did several times[1][2] in the
past.
However, this process got a bit tedious, so I decided that it would be
generally useful for NixOS, so this very implementation was born.
Now if you want to chroot a systemd service, all you need to do is:
{
systemd.services.yourservice = {
description = "My Shiny Service";
wantedBy = [ "multi-user.target" ];
chroot.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 chroot.packages option. By
default (which uses the "full-apivfs"[3] 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 as well,
which is useful for most programs that use the system() C library call
to execute commands via shell. The shell providing /bin/sh is dash
instead of the default in NixOS (which is bash), because it's way more
lightweight and after all we're chrooting because we want to lower the
attack surface and it should be only used for "/bin/sh -c something".
Prior to submitting this here, I did a first implementation of this
outside[4] of nixpkgs, which duplicated the "pathSafeName" functionality
from systemd-lib.nix, just because it's only a single line.
However, I decided to just re-use the one from systemd here and
subsequently made it available when importing systemd-lib.nix, so that
the systemd-chroot implementation also benefits from fixes to that
functionality (which is now a proper function).
Unfortunately, we do have a few limitations as well. The first being
that DynamicUser doesn't work in conjunction with tmpfs, because it
already sets up a tmpfs in a different path and simply ignores the one
we define. We could probably solve this by detecting it and try to
bind-mount our paths to that different path whenever DynamicUser is
enabled.
The second limitation/issue is that RootDirectoryStartOnly doesn't work
right now, because it only affects the RootDirectory option and not the
individual bind mounts or our tmpfs. It would be helpful if systemd
would have a way to disable specific bind mounts as well or at least
have some way to ignore failures for the bind mounts/tmpfs setup.
Another 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.
[1]: https://github.com/headcounter/shabitica/blob/3bb01728a0237ad5e7/default.nix#L43-L62
[2]: https://github.com/aszlig/avonc/blob/dedf29e092481a33dc/nextcloud.nix#L103-L124
[3]: The reason this is called "full-apivfs" instead of just "full" is
to make room for a *real* "full" confinement mode, which is more
restrictive even.
[4]: https://github.com/aszlig/avonc/blob/92a20bece4df54625e/systemd-chroot.nix
Signed-off-by: aszlig <aszlig@nix.build>
2019-03-10 11:21:55 +00:00
|
|
|
'';
|
|
|
|
}
|
2020-02-14 08:48:42 +00:00
|
|
|
{ testScript = ''
|
|
|
|
with subtest("check if /bin/sh works"):
|
|
|
|
machine.succeed(
|
|
|
|
"chroot-exec test -e /bin/sh",
|
|
|
|
'test "$(chroot-exec \'/bin/sh -c "echo bar"\')" = bar',
|
|
|
|
)
|
2019-03-14 18:07:03 +00:00
|
|
|
'';
|
|
|
|
}
|
2020-02-14 08:48:42 +00:00
|
|
|
{ config.confinement.binSh = null;
|
2019-03-14 18:07:03 +00:00
|
|
|
testScript = ''
|
2020-02-14 08:48:42 +00:00
|
|
|
with subtest("check if suppressing /bin/sh works"):
|
|
|
|
machine.succeed("chroot-exec test ! -e /bin/sh")
|
|
|
|
machine.succeed('test "$(chroot-exec \'/bin/sh -c "echo foo"\')" != foo')
|
2019-03-14 18:07:03 +00:00
|
|
|
'';
|
|
|
|
}
|
2020-02-14 08:48:42 +00:00
|
|
|
{ config.confinement.binSh = "${pkgs.hello}/bin/hello";
|
2019-03-14 18:07:03 +00:00
|
|
|
testScript = ''
|
2020-02-14 08:48:42 +00:00
|
|
|
with subtest("check if we can set /bin/sh to something different"):
|
|
|
|
machine.succeed("chroot-exec test -e /bin/sh")
|
|
|
|
machine.succeed('test "$(chroot-exec /bin/sh -g foo)" = foo')
|
2019-03-14 18:07:03 +00:00
|
|
|
'';
|
|
|
|
}
|
2020-02-14 08:48:42 +00:00
|
|
|
{ config.environment.FOOBAR = pkgs.writeText "foobar" "eek\n";
|
2019-03-14 18:48:20 +00:00
|
|
|
testScript = ''
|
2020-02-14 08:48:42 +00:00
|
|
|
with subtest("check if only Exec* dependencies are included"):
|
|
|
|
machine.succeed('test "$(chroot-exec \'cat "$FOOBAR"\')" != eek')
|
2019-03-14 18:48:20 +00:00
|
|
|
'';
|
|
|
|
}
|
2020-02-14 08:48:42 +00:00
|
|
|
{ config.environment.FOOBAR = pkgs.writeText "foobar" "eek\n";
|
2019-03-14 18:48:20 +00:00
|
|
|
config.confinement.fullUnit = true;
|
|
|
|
testScript = ''
|
2020-02-14 08:48:42 +00:00
|
|
|
with subtest("check if all unit dependencies are included"):
|
|
|
|
machine.succeed('test "$(chroot-exec \'cat "$FOOBAR"\')" = eek')
|
2019-03-14 18:48:20 +00:00
|
|
|
'';
|
|
|
|
}
|
2022-02-02 12:12:49 +00:00
|
|
|
{ serviceName = "shipped-unitfile";
|
|
|
|
config.confinement.mode = "chroot-only";
|
|
|
|
testScript = ''
|
|
|
|
with subtest("check if shipped unit file still works"):
|
|
|
|
machine.succeed(
|
|
|
|
'chroot-exec \'kill -9 $$ 2>&1 || :\' | '
|
|
|
|
'grep -q "Too many levels of symbolic links"'
|
|
|
|
)
|
|
|
|
'';
|
|
|
|
}
|
nixos: Add 'chroot' options to systemd.services
Currently, if you want to properly chroot a systemd service, you could
do it using BindReadOnlyPaths=/nix/store (which is not what I'd call
"properly", because the whole store is still accessible) or use a
separate derivation that 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. That's also what I did several times[1][2] in the
past.
However, this process got a bit tedious, so I decided that it would be
generally useful for NixOS, so this very implementation was born.
Now if you want to chroot a systemd service, all you need to do is:
{
systemd.services.yourservice = {
description = "My Shiny Service";
wantedBy = [ "multi-user.target" ];
chroot.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 chroot.packages option. By
default (which uses the "full-apivfs"[3] 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 as well,
which is useful for most programs that use the system() C library call
to execute commands via shell. The shell providing /bin/sh is dash
instead of the default in NixOS (which is bash), because it's way more
lightweight and after all we're chrooting because we want to lower the
attack surface and it should be only used for "/bin/sh -c something".
Prior to submitting this here, I did a first implementation of this
outside[4] of nixpkgs, which duplicated the "pathSafeName" functionality
from systemd-lib.nix, just because it's only a single line.
However, I decided to just re-use the one from systemd here and
subsequently made it available when importing systemd-lib.nix, so that
the systemd-chroot implementation also benefits from fixes to that
functionality (which is now a proper function).
Unfortunately, we do have a few limitations as well. The first being
that DynamicUser doesn't work in conjunction with tmpfs, because it
already sets up a tmpfs in a different path and simply ignores the one
we define. We could probably solve this by detecting it and try to
bind-mount our paths to that different path whenever DynamicUser is
enabled.
The second limitation/issue is that RootDirectoryStartOnly doesn't work
right now, because it only affects the RootDirectory option and not the
individual bind mounts or our tmpfs. It would be helpful if systemd
would have a way to disable specific bind mounts as well or at least
have some way to ignore failures for the bind mounts/tmpfs setup.
Another 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.
[1]: https://github.com/headcounter/shabitica/blob/3bb01728a0237ad5e7/default.nix#L43-L62
[2]: https://github.com/aszlig/avonc/blob/dedf29e092481a33dc/nextcloud.nix#L103-L124
[3]: The reason this is called "full-apivfs" instead of just "full" is
to make room for a *real* "full" confinement mode, which is more
restrictive even.
[4]: https://github.com/aszlig/avonc/blob/92a20bece4df54625e/systemd-chroot.nix
Signed-off-by: aszlig <aszlig@nix.build>
2019-03-10 11:21:55 +00:00
|
|
|
];
|
|
|
|
|
|
|
|
options.__testSteps = lib.mkOption {
|
|
|
|
type = lib.types.lines;
|
|
|
|
description = "All of the test steps combined as a single script.";
|
|
|
|
};
|
|
|
|
|
|
|
|
config.environment.systemPackages = lib.singleton testClient;
|
2022-02-02 12:12:49 +00:00
|
|
|
config.systemd.packages = lib.singleton (pkgs.writeTextFile {
|
|
|
|
name = "shipped-unitfile";
|
|
|
|
destination = "/etc/systemd/system/shipped-unitfile@.service";
|
|
|
|
text = ''
|
|
|
|
[Service]
|
|
|
|
SystemCallFilter=~kill
|
|
|
|
SystemCallErrorNumber=ELOOP
|
|
|
|
'';
|
|
|
|
});
|
nixos: Add 'chroot' options to systemd.services
Currently, if you want to properly chroot a systemd service, you could
do it using BindReadOnlyPaths=/nix/store (which is not what I'd call
"properly", because the whole store is still accessible) or use a
separate derivation that 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. That's also what I did several times[1][2] in the
past.
However, this process got a bit tedious, so I decided that it would be
generally useful for NixOS, so this very implementation was born.
Now if you want to chroot a systemd service, all you need to do is:
{
systemd.services.yourservice = {
description = "My Shiny Service";
wantedBy = [ "multi-user.target" ];
chroot.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 chroot.packages option. By
default (which uses the "full-apivfs"[3] 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 as well,
which is useful for most programs that use the system() C library call
to execute commands via shell. The shell providing /bin/sh is dash
instead of the default in NixOS (which is bash), because it's way more
lightweight and after all we're chrooting because we want to lower the
attack surface and it should be only used for "/bin/sh -c something".
Prior to submitting this here, I did a first implementation of this
outside[4] of nixpkgs, which duplicated the "pathSafeName" functionality
from systemd-lib.nix, just because it's only a single line.
However, I decided to just re-use the one from systemd here and
subsequently made it available when importing systemd-lib.nix, so that
the systemd-chroot implementation also benefits from fixes to that
functionality (which is now a proper function).
Unfortunately, we do have a few limitations as well. The first being
that DynamicUser doesn't work in conjunction with tmpfs, because it
already sets up a tmpfs in a different path and simply ignores the one
we define. We could probably solve this by detecting it and try to
bind-mount our paths to that different path whenever DynamicUser is
enabled.
The second limitation/issue is that RootDirectoryStartOnly doesn't work
right now, because it only affects the RootDirectory option and not the
individual bind mounts or our tmpfs. It would be helpful if systemd
would have a way to disable specific bind mounts as well or at least
have some way to ignore failures for the bind mounts/tmpfs setup.
Another 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.
[1]: https://github.com/headcounter/shabitica/blob/3bb01728a0237ad5e7/default.nix#L43-L62
[2]: https://github.com/aszlig/avonc/blob/dedf29e092481a33dc/nextcloud.nix#L103-L124
[3]: The reason this is called "full-apivfs" instead of just "full" is
to make room for a *real* "full" confinement mode, which is more
restrictive even.
[4]: https://github.com/aszlig/avonc/blob/92a20bece4df54625e/systemd-chroot.nix
Signed-off-by: aszlig <aszlig@nix.build>
2019-03-10 11:21:55 +00:00
|
|
|
|
|
|
|
config.users.groups.chroot-testgroup = {};
|
|
|
|
config.users.users.chroot-testuser = {
|
2021-03-07 13:54:00 +00:00
|
|
|
isSystemUser = true;
|
nixos: Add 'chroot' options to systemd.services
Currently, if you want to properly chroot a systemd service, you could
do it using BindReadOnlyPaths=/nix/store (which is not what I'd call
"properly", because the whole store is still accessible) or use a
separate derivation that 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. That's also what I did several times[1][2] in the
past.
However, this process got a bit tedious, so I decided that it would be
generally useful for NixOS, so this very implementation was born.
Now if you want to chroot a systemd service, all you need to do is:
{
systemd.services.yourservice = {
description = "My Shiny Service";
wantedBy = [ "multi-user.target" ];
chroot.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 chroot.packages option. By
default (which uses the "full-apivfs"[3] 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 as well,
which is useful for most programs that use the system() C library call
to execute commands via shell. The shell providing /bin/sh is dash
instead of the default in NixOS (which is bash), because it's way more
lightweight and after all we're chrooting because we want to lower the
attack surface and it should be only used for "/bin/sh -c something".
Prior to submitting this here, I did a first implementation of this
outside[4] of nixpkgs, which duplicated the "pathSafeName" functionality
from systemd-lib.nix, just because it's only a single line.
However, I decided to just re-use the one from systemd here and
subsequently made it available when importing systemd-lib.nix, so that
the systemd-chroot implementation also benefits from fixes to that
functionality (which is now a proper function).
Unfortunately, we do have a few limitations as well. The first being
that DynamicUser doesn't work in conjunction with tmpfs, because it
already sets up a tmpfs in a different path and simply ignores the one
we define. We could probably solve this by detecting it and try to
bind-mount our paths to that different path whenever DynamicUser is
enabled.
The second limitation/issue is that RootDirectoryStartOnly doesn't work
right now, because it only affects the RootDirectory option and not the
individual bind mounts or our tmpfs. It would be helpful if systemd
would have a way to disable specific bind mounts as well or at least
have some way to ignore failures for the bind mounts/tmpfs setup.
Another 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.
[1]: https://github.com/headcounter/shabitica/blob/3bb01728a0237ad5e7/default.nix#L43-L62
[2]: https://github.com/aszlig/avonc/blob/dedf29e092481a33dc/nextcloud.nix#L103-L124
[3]: The reason this is called "full-apivfs" instead of just "full" is
to make room for a *real* "full" confinement mode, which is more
restrictive even.
[4]: https://github.com/aszlig/avonc/blob/92a20bece4df54625e/systemd-chroot.nix
Signed-off-by: aszlig <aszlig@nix.build>
2019-03-10 11:21:55 +00:00
|
|
|
description = "Chroot Test User";
|
|
|
|
group = "chroot-testgroup";
|
|
|
|
};
|
|
|
|
};
|
|
|
|
|
|
|
|
testScript = { nodes, ... }: ''
|
systemd: 247.6 -> 249.4
This updates systemd to version v249.4 from version v247.6.
Besides the many new features that can be found in the upstream
repository they also introduced a bunch of cleanup which ended up
requiring a few more patches on our side.
a) 0022-core-Handle-lookup-paths-being-symlinks.patch:
The way symlinked units were handled was changed in such that the last
name of a unit file within one of the unit directories
(/run/systemd/system, /etc/systemd/system, ...) is used as the name
for the unit. Unfortunately that code didn't take into account that
the unit directories themselves could already be symlinks and thus
caused all our units to be recognized slightly different.
There is an upstream PR for this new patch:
https://github.com/systemd/systemd/pull/20479
b) The way the APIVFS is setup has been changed in such a way that we
now always have /run. This required a few changes to the
confinement tests which did assert that they didn't exist. Instead of
adding another patch we can just adopt the upstream behavior. An
empty /run doesn't seem harmful.
As part of this work I refactored the confinement test just a little
bit to allow better debugging of test failures. Previously it would
just fail at some point and it wasn't obvious which of the many
commands failed or what the unexpected string was. This should now be
more obvious.
c) Again related to the confinement tests the way a file was tested for
being accessible was optimized. Previously systemd would in some
situations open a file twice during that check. This was reduced to
one operation but required the procfs to be mounted in a units
namespace.
An upstream bug was filed and fixed. We are now carrying the
essential patch to fix that issue until it is backported to a new
release (likely only version 250). The good part about this story is
that upstream systemd now has a test case that looks very similar to
one of our confinement tests. Hopefully that will lead to less
friction in the long run.
https://github.com/systemd/systemd/issues/20514
https://github.com/systemd/systemd/pull/20515
d) Previously we could grep for dlopen( somewhat reliably but now
upstream started using a wrapper around dlopen that is most of the
time used with linebreaks. This makes using grep not ergonomic
anymore.
With this bump we are grepping for anything that looks like a
dynamic library name (in contrast to a dlopen(3) call) and replace
those instead. That seems more robust. Time will tell if this holds.
I tried using coccinelle to patch all those call sites using its
tooling but unfornately it does stumble upon the _cleanup_
annotations that are very common in the systemd code.
e) We now have some machinery for libbpf support in our systemd build.
That being said it doesn't actually work as generating some skeletons
doesn't work just yet. It fails with the below error message and is
disabled by default (in both minimal and the regular build).
> FAILED: src/core/bpf/socket_bind/socket-bind.skel.h
> /build/source/tools/build-bpf-skel.py --clang_exec /nix/store/x1bi2mkapk1m0zq2g02nr018qyjkdn7a-clang-wrapper-12.0.1/bin/clang --llvm_strip_exec /nix/store/zm0kqan9qc77x219yihmmisi9g3sg8ns-llvm-12.0.1/bin/llvm-strip --bpftool_exec /nix/store/l6dg8jlbh8qnqa58mshh3d8r6999dk0p-bpftools-5.13.11/bin/bpftool --arch x86_64 ../src/core/bpf/socket_bind/socket-bind.bpf.c src/core/bpf/socket_bind/socket-bind.skel.h
> libbpf: elf: socket_bind_bpf is not a valid eBPF object file
> Error: failed to open BPF object file: BPF object format invalid
> Traceback (most recent call last):
> File "/build/source/tools/build-bpf-skel.py", line 128, in <module>
> bpf_build(args)
> File "/build/source/tools/build-bpf-skel.py", line 92, in bpf_build
> gen_bpf_skeleton(bpftool_exec=args.bpftool_exec,
> File "/build/source/tools/build-bpf-skel.py", line 63, in gen_bpf_skeleton
> skel = subprocess.check_output(bpftool_args, universal_newlines=True)
> File "/nix/store/81lwy2hfqj4c1943b1x8a0qsivjhdhw9-python3-3.9.6/lib/python3.9/subprocess.py", line 424, in check_output
> return run(*popenargs, stdout=PIPE, timeout=timeout, check=True,
> File "/nix/store/81lwy2hfqj4c1943b1x8a0qsivjhdhw9-python3-3.9.6/lib/python3.9/subprocess.py", line 528, in run
> raise CalledProcessError(retcode, process.args,
> subprocess.CalledProcessError: Command '['/nix/store/l6dg8jlbh8qnqa58mshh3d8r6999dk0p-bpftools-5.13.11/bin/bpftool', 'g', 's', '../src/core/bpf/socket_bind/socket-bind.bpf.o']' returned non-zero exit status 255.
> [102/1457] Compiling C object src/journal/libjournal-core.a.p/journald-server.c.oapture output)put)ut)
> ninja: build stopped: subcommand failed.
f) We do now have support for TPM2 based disk encryption in our
systemd build. The actual bits and pieces to make use of that are
missing but there are various ongoing efforts in that direction.
There is also the story about systemd in our initrd to enable this
being used for root volumes. None of this will yet work out of the
box but we can start improving on that front.
g) FIDO2 support was added systemd and consequently we can now use
that. Just with TPM2 there hasn't been any integration work with
NixOS and instead this just adds that capability to work on that.
Co-Authored-By: Jörg Thalheim <joerg@thalheim.io>
2021-08-30 14:10:54 +01:00
|
|
|
def assert_eq(a, b):
|
|
|
|
assert a == b, f"{a} != {b}"
|
|
|
|
|
2020-02-14 08:48:42 +00:00
|
|
|
machine.wait_for_unit("multi-user.target")
|
|
|
|
'' + nodes.machine.config.__testSteps;
|
nixos: Add 'chroot' options to systemd.services
Currently, if you want to properly chroot a systemd service, you could
do it using BindReadOnlyPaths=/nix/store (which is not what I'd call
"properly", because the whole store is still accessible) or use a
separate derivation that 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. That's also what I did several times[1][2] in the
past.
However, this process got a bit tedious, so I decided that it would be
generally useful for NixOS, so this very implementation was born.
Now if you want to chroot a systemd service, all you need to do is:
{
systemd.services.yourservice = {
description = "My Shiny Service";
wantedBy = [ "multi-user.target" ];
chroot.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 chroot.packages option. By
default (which uses the "full-apivfs"[3] 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 as well,
which is useful for most programs that use the system() C library call
to execute commands via shell. The shell providing /bin/sh is dash
instead of the default in NixOS (which is bash), because it's way more
lightweight and after all we're chrooting because we want to lower the
attack surface and it should be only used for "/bin/sh -c something".
Prior to submitting this here, I did a first implementation of this
outside[4] of nixpkgs, which duplicated the "pathSafeName" functionality
from systemd-lib.nix, just because it's only a single line.
However, I decided to just re-use the one from systemd here and
subsequently made it available when importing systemd-lib.nix, so that
the systemd-chroot implementation also benefits from fixes to that
functionality (which is now a proper function).
Unfortunately, we do have a few limitations as well. The first being
that DynamicUser doesn't work in conjunction with tmpfs, because it
already sets up a tmpfs in a different path and simply ignores the one
we define. We could probably solve this by detecting it and try to
bind-mount our paths to that different path whenever DynamicUser is
enabled.
The second limitation/issue is that RootDirectoryStartOnly doesn't work
right now, because it only affects the RootDirectory option and not the
individual bind mounts or our tmpfs. It would be helpful if systemd
would have a way to disable specific bind mounts as well or at least
have some way to ignore failures for the bind mounts/tmpfs setup.
Another 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.
[1]: https://github.com/headcounter/shabitica/blob/3bb01728a0237ad5e7/default.nix#L43-L62
[2]: https://github.com/aszlig/avonc/blob/dedf29e092481a33dc/nextcloud.nix#L103-L124
[3]: The reason this is called "full-apivfs" instead of just "full" is
to make room for a *real* "full" confinement mode, which is more
restrictive even.
[4]: https://github.com/aszlig/avonc/blob/92a20bece4df54625e/systemd-chroot.nix
Signed-off-by: aszlig <aszlig@nix.build>
2019-03-10 11:21:55 +00:00
|
|
|
}
|