This new setting allows unsharing the pid namespace in a unit. Because
you have to fork to get a process into a pid namespace, we fork in
systemd-executor to get into the new pid namespace. The parent then
sends the pid of the child process back to the manager and exits while
the child process continues on with the rest of exec_invoke() and then
executes the actual payload.
Communicating the child pid is done via a new pidref socket pair that is
set up on manager startup.
We unshare the PID namespace right before the mount namespace so we
mount procfs correctly. Note PrivatePIDs=yes always implies MountAPIVFS=yes
to mount procfs.
When running unprivileged in a user session, user namespace is set up first
to allow for PID namespace to be unshared. However, when running in
privileged mode, we unshare the user namespace last to ensure the user
namespace does not own the PID namespace and cannot break out of the sandbox.
Note we disallow Type=forking services from using PrivatePIDs=yes since the
init proess inside the PID namespace must not exit for other processes in
the namespace to exist.
Note Daan De Meyer did the original work for this commit with Ryan Wilson
addressing follow-ups.
Co-authored-by: Daan De Meyer <daan.j.demeyer@gmail.com>
When an exec directory is shared between services, this allows one of the
service to be the producer of files, and the other the consumer, without
letting the consumer modify the shared files.
This will be especially useful in conjunction with id-mapped exec directories
so that fully sandboxed services can share directories in one direction, safely.
This commit adds two settings private and strict to
the ProtectControlGroups= property. Private will unshare the cgroup
namespace and mount a read-write private cgroup2 filesystem at /sys/fs/cgroup.
Strict does the same except the mount is read-only. Since the unit is
running in a cgroup namespace, the new root of /sys/fs/cgroup is the unit's
own cgroup.
We also add a new dbus property ProtectControlGroupsEx which accepts strings
instead of boolean. This will allow users to use private/strict via dbus
and systemd-run in addition to service files.
Note private and strict fall back to no and yes respectively if the kernel
doesn't support cgroup2 or system is not using unified hierarchy.
Fixes: #34634
This commit refactors ProtectControlGroups= from using a boolean
in the dbus/execute backend to using an enum. There is no functional
change but this will allow adding new non-boolean values (e.g. strict,
private) a la PrivateHome.
Follow-up for fa693fdc7e.
The documentation says the option takes a boolean or one of the "self"
and "identity". But the parser uses private_users_from_string() which
also accepts "off". Let's drop the implicit support of "off".
This allows for "per-instance" credentials for units. The use case
is best explained with an example. Currently all our getty units
have the following stanzas in their unit file:
"""
ImportCredential=agetty.*
ImportCredential=login.*
"""
This means that setting agetty.autologin=root as a system credential
will make every instance of our all our getty units autologin as the
root user. This prevents us from doing autologin on /dev/hvc0 while
still requiring manual login on all other ttys.
To solve the issue, we introduce support for renaming credentials with
ImportCredential=. This will allow us to add the following to e.g.
serial-getty@.service:
"""
ImportCredential=tty.serial.%I.agetty.*:agetty.
ImportCredential=tty.serial.%I.login.*:login.
"""
which for serial-getty@hvc0.service will make the service manager read
all credentials of the form "tty.serial.hvc0.agetty.xxx" and pass them
to the service in the form "agetty.xxx" (same goes for login). We can
apply the same to each of the getty units to allow setting agetty and
login credentials for individual ttys instead of globally.
The purpose of the check is to prevent leaking API VFS fds
from host into a mount namespace/container. When mountns
is not used at all, the check is pointless and causes
inconvenience. E.g. file managers might need to be spawned
under those directories, and they surely won't run in mountns.
Suggested in https://github.com/systemd/systemd/pull/33454#issuecomment-2186351467Fixes#33361
As discussed in https://github.com/systemd/systemd/pull/32724#discussion_r1638963071
I don't find the opposite reasoning particularly convincing.
We have ProtectHome=tmpfs and friends, and those can be
pretty much trivially implemented through TemporaryFileSystem=
too. The new logic brings many benefits, and is completely generic,
hence I see no reason not to expose it. We can even get more tests
for the code path if we make it public.
DynamicUser= enables PrivateTmp= implicitly to avoid files owned by reusable uids
leaking into the host. Change it to instead create a fully private tmpfs instance
instead, which also ensures the same result, since it has less impactful semantics
with respect to PrivateTmp=yes, which links the mount namespace to the host's /tmp
instead. If a user specifies PrivateTmp manually, let the existing behaviour
unchanged to ensure backward compatibility is not broken.
Follow-up for 14631951ce
Before this commit, if WorkingDirectory= is empty or literally "-",
'simplified' is not populated, resulting in the ASSERT_PTR
in unit_write_settingf() below getting triggered.
Also, do not accept "-", so that the parser is consistent
with load-fragment.c
Fixes#33015
Since we use varargs for sd_message_append() we need to make sure the
parameters we pass are actually 64bit wide, if "t" is used. Hence cast
appropriately if necessary.
I went through the whole tree, and in most cases we got it right, but
there are some cases we missed so far.
Inspired by: #31420
Note sure why it didn't occur earlier to me, but now that we have this
nice helper to get the effective value of the set_login_environment
field instead of just falling back to "false".
Follow-up for: #30552
This is preparation for #28891, which adds a bunch more helpers around
"struct iovec", at which point this really deserves its own .c/.h file.
The idea is that we sooner or later can consider "struct iovec" as an
entirely generic mechanism to reference some binary blob, and is the
go-to type for this purpose whenever we need one.
Before this commit, $USER, $HOME, $LOGNAME and $SHELL are only
set when User= is set for the unit. For system service, this
results in different behaviors depending on whether User=root is set.
$USER always makes sense on its own, so let's set it unconditionally.
Ideally $HOME should be set too, but it causes trouble when e.g. getty
passes '-p' to login(1), which then doesn't override $HOME. $LOGNAME and
$SHELL are more like "login environments", and are generally not
suitable for system services. Therefore, a new option SetLoginEnvironment=
is also added to control the latter three variables.
Fixes#23438
Replaces #8227
seccomp-util.h doesn't need ifdeffing, hence don't. It has worked since
quite a while with HAVE_SECCOMP is off, hence use it everywhere.
Also drop explicit seccomp.h inclusion everywhere (which needs
HAVE_SECCOMP ifdeffery everywhere). seccomp-util.h includes it anyway,
automatically, which we can just rely on, and it deals with HAVE_SECCOMP
at one central place.
Let's restrict how we apply credential globbing in ImportCredential=, so
that we have some flexibility in automatically extending the glob
expression with per-instance data eventually without getting into
conflict with the globbing parts.
In our current uses we only allow globbing at the end of the expression,
and this is a new, unreleased feature hence let's be restrictive on this
initially. We can still relax this later if we feel the need to after
all.
Fixes: #28022
This setting allows services to run in an ephemeral copy of the root
directory or root image. To make sure the ephemeral copies are always
cleaned up, we add a tmpfiles snippet to unconditionally clean up
/var/lib/systemd/ephemeral. To prevent in use ephemeral copies from
being cleaned up by tmpfiles, we use the newly added COPY_LOCK_BSD
and BTRFS_SNAPSHOT_LOCK_BSD flags to take a BSD lock on the ephemeral
copies which instruct tmpfiles to not touch those ephemeral copies as
long as the BSD lock is held.
This new helper adds all strings from a Set object as a string array to
a message.
Various places where we have similar code are then ported over to this.
ImportCredential= takes a credential name and searches for a matching
credential in all the credential stores we know about it. It supports
globs which are expanded so that all matching credentials are loaded.
This adds support for KSM (kernel samepage merging). It adds a new
boolean parameter called MemoryKSM to enable the feature. The feature
can only be enabled with newer kernels.
The property name is called ExecStartEx, but we have to write it as ExecStart=
in the unit file. :(
Bug introduced in b3d593673c when ex-properties
were initially added.
In addition, we cannot escape $ as $$, because when ":" is used, we wouldn't
unescape $$ back to $.
Daan De Meyer
Luca Boccassi
Ryan Wilson
Yu Watanabe
Mike Yuan
Luca Boccassi
Lennart Poettering
Frantisek Sumsal
Joerg Behrmann
David Tardon
Stefan Roesch
Zbigniew Jędrzejewski-Szmek