ENOENT means /dev/loop-control isn't there which means we're in a
container and should go via mountfsd.
At the same time, reverse the check for fatal actions as almost all
actions can be done via mountfsd, only --attach needs the loop device.
I expressed the issue I have with parse_tristate_argument()
in #37751: it doesn't add any value to direct use of parse_tristate();
on the contrary, it doesn't support means to reset the arg to "auto"/-1 state.
The mere reason it existed is that we need a int type ret param.
Since the previous attempt to address this mess failed, let's
try to make the function more useful by making it accept "auto".
I figure this is useful on its own.
As requested in
https://github.com/systemd/systemd/pull/40652#discussion_r2831833996,
the function name is suffixed with _with_auto() to establish
that "auto" is handled internally.
So far we opened a new Varlink connection for every mountfsd/nsresourced
method call. Given each tool only does a very small number of calls
(usually 1…5) on them and the connections are cheap this is not too
wasteful. Nonetheless, let's do something about it, and allow reusing
the connection for multiple calls.
This not only makes things a bit more efficient, but has one more
important benefit: Varlink connections pin the security context of the
client when connecting. This means that varlink method calls done with a
connection established while some code was privileged will still operate
as privieged once privs are dropped, until the connection is closed.
This pinning effect is really nice, as it gives us behaviour in a
"capability system" like scheme. Later code is going to use that to
continue doing certain priv userns ops even after unsharing userns and
becoming fully unpriv.
Currently, if we're copying a file, we won't copy the owner UID/GID
from the source. If we're copying a directory, we will copy the owner
UID/GID from the source. Let's give users a bit more control over this
behavior by introducing --copy-ownership= which will default to the
current behavior but allows users to explicitly enable/disable copying
of ownership.
Let's check for CAP_SYS_ADMIN instead of root for these, and make
unmounting more graceful if we can't access the backing loop device
because of permission issues. This allows mounting and unmounting images
from an unprvileged mount namespace. The actual files in the image will
end up owned by nobody:nobody because we'll be in an unprivileged user
namespace, but assuming the directory permissions are not too strict, this
still allows interacting with the image in useful ways.
These actions interact with the host. The former needs privileges to
write into the image, the latter needs privileges to write on the host.
Neither will have the privileges required if the image is attached under
a private userns, hence, don't use one.
RootImageOptions=/ExtensionImages=/MountImages= all support custom
mount options, but mountfsd does not support it. Add varlink
parameters to allow callers to specify mount options so that
those directives can work as expected. Require additional privs via
polkit.
Currently, pick_filter_image_any matches any image
with any suffix, which is way more than it should
be doing. It should only be matching images with
the .raw suffix.
Let's address this shortcoming by allowing to pass
multiple filters to path_pick(), and define
pick_filter_image_any as the combination of the
raw and directory image filters.
Fixes#40083
RootImageOptions=/ExtensionImages=/MountImages= all support
custom mount options, use the new mountfsd parameters to
configure them if they are specified.
This requires additioanl privileges via polkit due to security
implications of mount options, so document an example policy
that allows to use the nosuid mount option.
Marking a whole directory tree OS image as read-only is difficult
privilege-wise, because so far we rely on the FS_IMMUTABLE_FL which is
not accessible to unpriv clients.
One fundamental place where we currently rely on marking images
read-only is for keeping pristine copies of the originally downloaded
image around, which we place in "hidden" image directories. This is
probably the most relevant usecase for the read-only flag. And moreover,
the only usecase for the hidden images are these read-only pristine
copies.
Hence, let's make this work reasonably in the unpriv case, and simply
imply the read-only flag for hidden images. This is strictly speaking a
change in behaviour, but effectively it shouldn't be, because for nspawn
containers that are executed we insist on names that are hostname
compatible, and hidden names aren't (because they start with a dot).
Needed to implement support for RootHashSignature=/RootVerity=/RootHash=
and friends when going through mountfsd, for example with user units,
so that system and user units provide the same features at the same
level
Previously, we'd take the image policy only into consideration when
dissecting the mage, but for the unlock/verity step we'd go via best
effort. Change that. This means we can now enforce policies such as
activating by root hash only even if a signature exists and similar.
Also, introduce a separate error code if we try to unlock a Verity
volume but have no root hash. Previously we'd return ENOKEY for that,
exactly like we do for encrypted volumes where we have no passparse. The
interctive unlock loop dissected_image_decrypt_interactively() is
otherwise very confused and will ask for a root hash, which makes no
sense. Hence use two distinct errors for this.
In multi-seat scenarios, a display manager might need to start multiple
greeter sessions. But systemd allows at most one graphical session per
user. So, display managers now have a range of UIDs to dynamically
allocate users for their greeter sessions.
Let's always make sure the temporary file returned by fopen_tmpfile()
and friends is removed on failure (via _cleanup_). Conversely, make sure
that once the file is renamed into its final place, we no longer try to
remove the temporary file (since it's not going to exist anymore).
This commit cleans up the includes for all the small tools across
the tree.
A few cases of returning EXIT_SUCCESS are replaced with returning
0 to avoid including <stdlib.h>.
Split out of #37344.
Let's move some logic from _DEFINE_MAIN_FUNCTION() and other places
in main-func.h into functions that we implement in main-func.c to
allow moving some included headers from the header to the .c file.
DDIs may contain multiple versions of the same OS, or even multiple
OSes. Hence it makes sense to not just pick the "newest", whatever that
might be, but only partitions associated with specific images, or in a
specific version.
Let's a concept for such filtering: a per-designator glob expression
that can be applied to the partition label string, and can be used for
such filtering.
Usecase: when picking UKI belonging to OS image X in version Y, make
sure we only pick a /usr/ partition belonging to X in version Y, and a
root and home partition belonging to X in any version.
This only adds the basic infrastructure, but doesn't actually expose it
anywhere.
When dissecting an image, let's make use of the Verity data even if we
got told no root hash explicitly: we can simply determine it by
concatenating the data partition uuid with the verity partition uuid.
Of course, on first thought this doesn't really add much: if the root
hash is not pinned from somewhere, this does not guarantee trust in
the image.
However, this is very useful for attestation: if we have the root hash
we can measure it before mounting things, even if we don't actually
authenticate it.
Hence, at best this helps us with attestation, at worst it doesn't improve
security but certainly doesn't hurt it.
Admittedly, some of our glyphs _are_ special, e.g. "O=" for SPECIAL_GLYPH_TOUCH ;)
But we don't need this in the name. The very long names make some invocations
very wordy, e.g. special_glyph(SPECIAL_GLYPH_SLIGHTLY_UNHAPPY_SMILEY).
Also, I want to add GLYPH_SPACE, which is not special at all.
Now our baseline of meson is 0.62, hence install_symlink() can be used.
Note, install_symlink() implies install_emptydir() for specified
install_dir. Hence, this also drops several unnecessary
install_emptydir() calls.
Note, the function currently does not support 'relative' and 'force' flags,
so several 'ln -frsT' inline calls cannot be replaced.
Daan De Meyer
Mike Yuan
Lennart Poettering
DaanDeMeyer
Luca Boccassi
Luca Boccassi
Yu Watanabe
Jelle van der Waa
Lennart Poettering
Adrian Vovk
Zbigniew Jędrzejewski-Szmek