Let's enable this in all tools that intend to write to the OS images.
It's not conditionalized for now, as there already is conditionalization
in the existance or absence of the flag in the GPT partition table (and
it's opt-in), hence it should be OK to just enable this by default for
now if the flag is set.
This tries to shorten the race of device reuse a bit more: let's ignore
udev database entries that are older than the time where we started to
use a loopback device.
This doesn't fix the whole loopback device raciness mess, but it makes
the race window a bit shorter.
Let's drop all monitor uevent that were enqueued before we actually
started setting up the device.
This doesn't fix the race, but it makes the race window smaller: since
we cannot determine the uevent seqnum and the loopback attachment
atomically, there's a tiny window where uevents might be generated by
the device which we mistake for being associated with out use of the
loopback device.
Let's have one flag to request that when dissecting an image the
loopback device is made read-only, and another one to request that when
it is mounted to make it read-only. Previously both concepts were always
done read-only together.
(Of course, making the loopback device read-only but mounting it
read-write doesn't make too much sense, but the kernel should catch that
for us, no need to make restrictions from our side there)
Use-case for this: in systemd-repart we'd like to operate on images for
adding partitions. Thus we'd like to have the loopback device writable,
but if we read repart.d/ snippets from it, we want to do that read-only.
With some versions of the compiler, the _cleanup_ attr makes it think
the variable might be freed/closed when uninitialized, even though it
cannot happen. The added cost is small enough to be worth the benefit,
and optimized builds will help reduce it even further.
The function already has a ridiculous amount of paramaters, let's drop
one that is either not used at all or has a constant value and let's
pick it internally.
Previously, the flag did two things at once: enable support for using
generic partitions as root fs if there were only one/allow use of
partition-table-less images as root fs. And secondly, insist that there
was a rootfs, and fail if not. Let's split these two in two separate
options so that they can be used independently of each other.
There are cases where one wants to use one without the other (i.e. when
inspecting things with systemd-dissect tool it should be OK to do so
even if image has no root fs), and it's cleaner anyway.
It causes a regression in certain running environments (networkd under LXC),
so avoid enabling for now.
Fixes#18795
Suggested-by: Topi Miettinen <toiwoton@gmail.com>
Some paths (eg: mount_tmpfs) simply assumed that prefixing always
happens and it always stores the original path in path_const, and
the prefixed path in path_malloc.
But if a MountEntry is set up in a helper function and thus uses
only _malloc struct members, this assumption doesn't hold and there's
a crash.
Refactor so that prefixing is done with a helper which stores the
original path in a separate struct member, and accessing it also
uses a helper which does the right thing.
Implement directives `NoExecPaths=` and `ExecPaths=` to control `MS_NOEXEC`
mount flag for the file system tree. This can be used to implement file system
W^X policies, and for example with allow-listing mode (NoExecPaths=/) a
compromised service would not be able to execute a shell, if that was not
explicitly allowed.
Example:
[Service]
NoExecPaths=/
ExecPaths=/usr/bin/daemon /usr/lib64 /usr/lib
Closes: #17942.
Previously if people enabled RootDirectory=/RootImage= and NotifyAccess=
together, things wouldn't work, they'd have to explicitly add
BindReadOnlyPaths=/run/systemd/notify too.
Let's make this implicit. Since both options are opt-in, if people use
them together it would be pointless not also defining the
BindReadOnlyPaths= entry, in which case we can just do it automatically.
See: #18051
Allow to setup new bind mounts for a service at runtime (via either
DBUS or a new 'systemctl bind' verb) with a new helper that forks into
the unit's mount namespace.
Add a new integration test to cover this.
Useful for zero-downtime addition to services that are running inside
mount namespaces, especially when using RootImage/RootDirectory.
If a service runs with a read-only root, a tmpfs is added on /run
to ensure we can create the airlock directory for incoming mounts
under /run/host/incoming.
We need a writable /run for most operations, but in case a read-only
RootImage (or similar) is used, by default there's no additional
tmpfs mount on /run. Change this behaviour and document it.
If a namespace with PrivateTmp=true is constructed we need to restore
the context of the namespaces /tmp directory (i.e.
/tmp/systemd-private-XXXXX/tmp) to the (default) context of /tmp .
Otherwise filetransitions might result in the namespaces tmp directory
having the wrong context.
(Well, at least the ones where that makes sense. Where it does't make
sense are the ones that re invoked on the root path, which cannot
possibly be a symlink.)
Just some refactoring: let's place the various verity related parameters
in a common structure, and pass that around instead of the individual
parameters.
Also, let's load the PKCS#7 signature data when finding metadata
right-away, instead of delaying this until we need it. In all cases we
call this there's not much time difference between the metdata finding
and the loading, hence this simplifies things and makes sure root hash
data and its signature is now always acquired together.
Ideally we would like to hide all other service's credentials for all
services. That would imply for us to enable mount namespacing for all
services, which is something we cannot do, both due to compatibility
with the status quo ante, and because a number of services legitimately
should be able to install mounts in the host hierarchy.
Hence we do the second best thing, we hide the credentials automatically
for all services that opt into mount namespacing otherwise. This is
quite different from other mount sandboxing options: usually you have to
explicitly opt into each. However, given that the credentials logic is a
brand new concept we invented right here and now, and particularly
security sensitive it's OK to reverse this, and by default hide
credentials whenever we can (i.e. whenever mount namespacing is
otherwise opt-ed in to).
Long story short: if you want to hide other service's credentials, the
most basic options is to just turn on PrivateMounts= and there you go,
they should all be gone.
Kernel 5.8 gained a hidepid= implementation that is truly per procfs,
which allows us to mount a distinct once into every unit, with
individual hidepid= settings. Let's expose this via two new settings:
ProtectProc= (wrapping hidpid=) and ProcSubset= (wrapping subset=).
Replaces: #11670
it's not entirely clear what shall be passed via parameter and what via
struct, but these two definitely fit well with the other protect_xyz
fields, hence let's move them over.
We probably should move a lot more more fields into the structure
actuall (most? all even?).
Similarly to "setup" vs. "set up", "fallback" is a noun, and "fall back"
is the verb. (This is pretty clear when we construct a sentence in the
present continous: "we are falling back" not "we are fallbacking").
Follow the same model established for RootImage and RootImageOptions,
and allow to either append a single list of options or tuples of
partition_number:options.
Follows the same pattern and features as RootImage, but allows an
arbitrary mount point under / to be specified by the user, and
multiple values - like BindPaths.
Original implementation by @topimiettinen at:
https://github.com/systemd/systemd/pull/14451
Reworked to use dissect's logic instead of bare libmount() calls
and other review comments.
Thanks Topi for the initial work to come up with and implement
this useful feature.
Lennart Poettering
Luca Boccassi
Zbigniew Jędrzejewski-Szmek
Frantisek Sumsal
Xℹ Ruoyao
Yu Watanabe
Topi Miettinen
Susant Sahani
Luca Boccassi
Daan De Meyer
bauen1