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"Login Service" doesn''t explain much, esp. considering that logind is actually is
for logins. I think "User Login Management" is better, but not that great either.
Suggestions welcome.
Add `ProtectClock=yes` to systemd units. Since it implies certain
`DeviceAllow=` rules, make sure that the units have `DeviceAllow=` rules so
they are still able to access other devices. Exclude timesyncd and timedated.
Devices referred to by `DeviceAllow=` sandboxing are resolved into their
corresponding major numbers when the unit is loaded by looking at
`/proc/devices`. If a reference is made to a device which is not yet
available, the `DeviceAllow` is ignored and the unit's processes cannot
access that device.
In both logind and nspawn, we have `DeviceAllow=` lines, and `modprobe`
in `ExecStartPre=` to load some kernel modules. Those kernel modules
cause device nodes to become available when they are loaded: the device
nodes may not exist when the unit itself is loaded. This means that the
unit's processes will not be able to access the device since the
`DeviceAllow=` will have been resolved earlier and denied it.
One way to fix this would be to re-evaluate the available devices and
re-apply the policy to the cgroup, but this cannot work atomically on
cgroupsv1. So we fall back to a second approach: instead of running
`modprobe` via `ExecStartPre`, we move this out to a separate unit and
order it before the units which want the module.
Closes#14322.
Fixes: #13943.
We set ProtectKernelLogs=yes on all long running services except for
udevd, since it accesses /dev/kmsg, and journald, since it calls syslog
and accesses /dev/kmsg.
As discussed on systemd-devel [1], in Fedora we get lots of abrt reports
about the watchdog firing [2], but 100% of them seem to be caused by resource
starvation in the machine, and never actual deadlocks in the services being
monitored. Killing the services not only does not improve anything, but it
makes the resource starvation worse, because the service needs cycles to restart,
and coredump processing is also fairly expensive. This adds a configuration option
to allow the value to be changed. If the setting is not set, there is no change.
My plan is to set it to some ridiculusly high value, maybe 1h, to catch cases
where a service is actually hanging.
[1] https://lists.freedesktop.org/archives/systemd-devel/2019-October/043618.html
[2] https://bugzilla.redhat.com/show_bug.cgi?id=1300212
While the need for access to character devices can be tricky to determine for
the general case, it's obvious that most of our services have no need to access
block devices. For logind and timedated this can be tightened further.
This behaves similar to the "boot into firmware" logic, and also allows
either direct EFI operation (which sd-boot supports and others might
support eventually too) or override through env var.
now that logind doesn't mount $XDG_RUNTIME_DIR anymore we can lock down
the service using fs namespacing (as we don't need the mount to
propagate to the host namespace anymore).
Previously, setting this option by default was problematic due to
SELinux (as this would also prohibit the transition from PID1's label to
the service's label). However, this restriction has since been lifted,
hence let's start making use of this universally in our services.
On SELinux system this change should be synchronized with a policy
update that ensures that NNP-ful transitions from init_t to service
labels is permitted.
An while we are at it: sort the settings in the unit files this touches.
This might increase the size of the change in this case, but hopefully
should result in stabler patches later on.
Fixes: #1219
This updates the unit files of all our serviecs that deal with journal
stuff to use a higher RLIMIT_NOFILE soft limit by default. The new value
is the same as used for the new HIGH_RLIMIT_NOFILE we just added.
With this we ensure all code that access the journal has higher
RLIMIT_NOFILE. The code that runs as daemon via the unit files, the code
that is run from the user's command line via C code internal to the
relevant tools. In some cases this means we'll redundantly bump the
limits as there are tools run both from the command line and as service.
This is generally the safer approach, and is what container managers
(including nspawn) do, hence let's move to this too for our own
services. This is particularly useful as this this means the new
@system-service system call filter group will get serious real-life
testing quickly.
This also switches from firing SIGSYS on unexpected syscalls to
returning EPERM. This would have probably been a better default anyway,
but it's hard to change that these days. When whitelisting system calls
SIGSYS is highly problematic as system calls that are newly introduced
to Linux become minefields for services otherwise.
Note that this enables a system call filter for udev for the first time,
and will block @clock, @mount and @swap from it. Some downstream
distributions might want to revert this locally if they want to permit
unsafe operations on udev rules, but in general this shiuld be mostly
safe, as we already set MountFlags=shared for udevd, hence at least
@mount won't change anything.
Some kdbus_flag and memfd related parts are left behind, because they
are entangled with the "legacy" dbus support.
test-bus-benchmark is switched to "manual". It was already broken before
(in the non-kdbus mode) but apparently nobody noticed. Hopefully it can
be fixed later.
This patch ensures that session devices are saved for each session.
In order to make the revokation logic work when logind is restarted, the
session devices are now saved in the session state files and their respective
file descriptors sent to PID1's fdstore in order to keep them open accross
restart.
This is mandatory in order to keep the revokation logic working. Indeed in case
of input-devices, the same file descriptors must be shared by logind and a
given session controller in order EVIOCREVOKE to work otherwise multiple
sessions can have device access in parallel.
This should be the only remaining and missing piece for making logind fully
restartable.
Fixes: #1163
Basically, we turn it on for most long-running services, with the
exception of machined (whose child processes need to join containers
here and there), and importd (which sandboxes tar in a CLONE_NEWNET
namespace). machined is left unrestricted, and importd is restricted to
use only "net"
Let's make this an excercise in dogfooding: let's turn on more security
features for all our long-running services.
Specifically:
- Turn on RestrictRealtime=yes for all of them
- Turn on ProtectKernelTunables=yes and ProtectControlGroups=yes for most of
them
- Turn on RestrictAddressFamilies= for all of them, but different sets of
address families for each
Also, always order settings in the unit files, that the various sandboxing
features are close together.
Add a couple of missing, older settings for a numbre of unit files.
Note that this change turns off AF_INET/AF_INET6 from udevd, thus effectively
turning of networking from udev rule commands. Since this might break stuff
(that is already broken I'd argue) this is documented in NEWS.
Add a line
SystemCallFilter=~@clock @module @mount @obsolete @raw-io ptrace
for daemons shipped by systemd. As an exception, systemd-timesyncd
needs @clock system calls and systemd-localed is not privileged.
ptrace(2) is blocked to prevent seccomp escapes.
Apparently, disk IO issues are more frequent than we hope, and 1min
waiting for disk IO happens, so let's increase the watchdog timeout a
bit, for all our services.
See #1353 for an example where this triggers.
This reverts commit a4962513c5.
logind.service is a D-Bus service, hence we should use the dbus name as
indication that we are up. Type=dbus is implied if BusName= is
specified, as it is in this case.
This removes a warning that is printed because a BusName= is specified
for a Type=notify unit.
The code already calls sd_notify("READY=1"), so we may as well take
advantage of the startup behavior in the unit. The same was done for
the journal in a87a38c20.
ReadOnlySystem= uses fs namespaces to mount /usr and /boot read-only for
a service.
ProtectedHome= uses fs namespaces to mount /home and /run/user
inaccessible or read-only for a service.
This patch also enables these settings for all our long-running services.
Together they should be good building block for a minimal service
sandbox, removing the ability for services to modify the operating
system or access the user's private data.
That is, without --enable-kdbus and kdbus running.
With --enable-kdbus things are more complicated, because dbus might be
necessary, if kdbus is missing at runtime. If it is not necessary,
the socket will be started, which is not imporant, but not the service.
Adds a new call sd_event_set_watchdog() that can be used to hook up the
event loop with the watchdog supervision logic of systemd. If enabled
and $WATCHDOG_USEC is set the event loop will ping the invoking systemd
daemon right after coming back from epoll_wait() but not more often than
$WATCHDOG_USEC/4. The epoll_wait() will sleep no longer than
$WATCHDOG_USEC/4*3, to make sure the service manager is called in time.
This means that setting WatchdogSec= in a .service file and calling
sd_event_set_watchdog() in your daemon is enough to hook it up with the
watchdog logic.
DRM Master access requires CAP_SYS_ADMIN, yay! Add it to the capability
bounding set for systemd-logind. As CAP_SYS_ADMIN actually allows a huge
set of actions, this mostly renders the restriction-set useless. Anyway,
patches are already pending to reduce the restriction on the kernel side.
But these won't really make it into any stable-release so for now we're
stuck with CAP_SYS_ADMIN.
