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The ESP is simply not mounted early enough for this. We want that the
regular random seed handling runs as early as we possibly could, but we
don't want to delay this until the ESP is actually mounted.
Hence, let's remove this from random-seed.c here. A follow-up commit
will then add this back in, in a separate service which just calls
"bootctl random-seed".
Effectively reverts: f913c784adFixes: #25769
-1 was used everywhere, but -EBADF or -EBADFD started being used in various
places. Let's make things consistent in the new style.
Note that there are two candidates:
EBADF 9 Bad file descriptor
EBADFD 77 File descriptor in bad state
Since we're initializating the fd, we're just assigning a value that means
"no fd yet", so it's just a bad file descriptor, and the first errno fits
better. If instead we had a valid file descriptor that became invalid because
of some operation or state change, the other errno would fit better.
In some places, initialization is dropped if unnecessary.
Since this runs at shutdown to write a new seed, we should also keep the
bootloader's seed maximally fresh by doing the same. So we follow the
same pattern - hash some new random bytes with the old seed to make a
new seed. We let this fail without warning, because it's just an
opportunistic thing. If the user happens to have set up the random seed
with bootctl, and the RNG is initialized, then things should be fine. If
not, we create a new seed if systemd-boot is in use. And if not, then we
just don't do anything.
We want the size to lie within [/proc/sys/kernel/random/poolsize,RANDOM_POOL_SIZE_MAX]
interval. Let's make it more obvious.
Also move the logic in a dedicated function.
It's not really necessary since systemd-random-seed is an internal tool for the
moment but this might change in future (to allow system installers to
initialize a random seed file for example).
Also introducing new options will be easier.
If we're consuming an on-disk seed, we usually write out a new one after
consuming it. In that case, we might be at early boot and the randomness
could be rather poor, and the kernel doesn't guarantee that it'll use
the new randomness right away for us. In order to prevent the new
entropy from getting any worse, hash together the old seed and the new
seed, and replace the final bytes of the new seed with the hash output.
This way, entropy strictly increases and never regresses.
Fixes: https://github.com/systemd/systemd/issues/21983
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
This makes two major changes to the way systemd-random-seed operates:
1. We now optionally credit entropy if this is configured (via an env
var). Previously we never would do that, with this change we still don't
by default, but it's possible to enable this if people acknowledge that
they shouldn't replicate an image with a contained random seed to
multiple systems. Note that in this patch crediting entropy is a boolean
thing (unlike in previous attempts such as #1062), where only a relative
amount of bits was credited. The simpler scheme implemented here should
be OK though as the random seeds saved to disk are now written only with
data from the kernel's entropy pool retrieved after the pool is fully
initialized. Specifically:
2. This makes systemd-random-seed.service a synchronization point for
kernel entropy pool initialization. It was already used like this, for
example by systemd-cryptsetup-generator's /dev/urandom passphrase
handling, with this change it explicitly operates like that (at least
systems which provide getrandom(), where we can support this). This
means services that rely on an initialized random pool should now place
After=systemd-random-seed.service and everything should be fine. Note
that with this change sysinit.target (and thus early boot) is NOT
systematically delayed until the entropy pool is initialized, i.e.
regular services need to add explicit ordering deps on this service if
they require an initialized random pool.
Fixes: #4271
Replaces: #10621#4513
There's no reason why writing should work if reading and writing
doesn't. Let's simplify this hence. /dev/urandom is generally an r/w
device, and everything else would be a serious system misconfiguration.
We don't load the selinux label database anyway, hence this is not going
to do anything at all. Let's simplify this hence and drop the explicit
request.
Also note that today SELinux can take the filename into account when
automatically deducing the label for a new file, hence even if this code
actually would have done something it is redundant today.
Ideally, coccinelle would strip unnecessary braces too. But I do not see any
option in coccinelle for this, so instead, I edited the patch text using
search&replace to remove the braces. Unfortunately this is not fully automatic,
in particular it didn't deal well with if-else-if-else blocks and ifdefs, so
there is an increased likelikehood be some bugs in such spots.
I also removed part of the patch that coccinelle generated for udev, where we
returns -1 for failure. This should be fixed independently.
This way, we can extend the macro a bit with stuff pulled in from other
headers without this affecting everything which pulls in macro.h, which
is one of our most basic headers.
This is just refactoring, no change in behaviour, in prepartion for
later changes.
This is some extra protection for sloppy "golden master" systems, where
images are duplicated many times but the random seed is not
deleted (or reset for each copy). That golden master systems have to
reset /etc/machine-id is better known, and easier to notice (as having
the same ID will result in address conflicts and suchlike quite often).
Hence let's write the machine ID into /dev/urandom, in case it has been
initialized and unlikely the stored random seed has been provisioned
differently on each image.
Note that we don't credit the entropy either way, hence in the case
there's a cycle of a) generating the machine-id early at boot and b)
writing it back into /dev/urandom late at boot it shouldn't matter. It's
never going to make things worse, just in a few cases better.
Previously, we'd only ever read 512 byte from the random seed file,
under the assumption we won't need more. With this change we'll read the
full file, even if it is larger.
The idea behind htis change is that people can dump additional data into the
random seed file offline if they like, and it can be low quality, and
we'll seed the pool with it anyway. Moreover, if people are paranoid and
want us to save/restore a bigger seed, it's easy to do: just truncate
the file to the right size and we'll save/restore as much in the future.
This also reworks the file a bit, introducing two clear if blocks that
load and that save the random seed, and that each are conditionalized
more carefully.
These lines are generally out-of-date, incomplete and unnecessary. With
SPDX and git repository much more accurate and fine grained information
about licensing and authorship is available, hence let's drop the
per-file copyright notice. Of course, removing copyright lines of others
is problematic, hence this commit only removes my own lines and leaves
all others untouched. It might be nicer if sooner or later those could
go away too, making git the only and accurate source of authorship
information.
This part of the copyright blurb stems from the GPL use recommendations:
https://www.gnu.org/licenses/gpl-howto.en.html
The concept appears to originate in times where version control was per
file, instead of per tree, and was a way to glue the files together.
Ultimately, we nowadays don't live in that world anymore, and this
information is entirely useless anyway, as people are very welcome to
copy these files into any projects they like, and they shouldn't have to
change bits that are part of our copyright header for that.
hence, let's just get rid of this old cruft, and shorten our codebase a
bit.
Files which are installed as-is (any .service and other unit files, .conf
files, .policy files, etc), are left as is. My assumption is that SPDX
identifiers are not yet that well known, so it's better to retain the
extended header to avoid any doubt.
I also kept any copyright lines. We can probably remove them, but it'd nice to
obtain explicit acks from all involved authors before doing that.
