man: systemd-stub places PCR public key in file 'tpm2-pcr-public-key.pem', stick to that name across the board
systemd-stub provides the signing key for TPM2 signed PCR policies in a
file tpm2-pcr-public-key.pem to userspace. Hence, to clarify that this
is the same key as used when signing via "systemd-measure", let's rename
it in the docs like that.
Also rename the private key to tpm2-pcr-private-key.pem, to keep the
symmetry.
With this we should universally stick to this nomenclature:
1. tpm2-pcr-public-key.pem ← public part of signing key
2. tpm2-pcr-private-key.pem ← private part of signing key
3. tpm2-pcr-signature.json ← signature file made with key pair
This is a rework of e7a93e75219b22424bab95fe45982f5eef21d581: instead of
handling components with n_variants being zero at every step of the way, we instead
remove it from our list after loading all components, given that such a
component simply makes not sense for the rest of our logic.
cryptenroll: don't try to get PCR bank if we know the device key
If we operate in "offline" mode, i.e. know the device key, then we will
not have a TPM2 connection, hence don't try to read the PCR bank to use form
it.
We don't need it anyway because we are not going to test unseal things.
Karel Zak [Wed, 11 Sep 2024 09:27:09 +0000 (11:27 +0200)]
udev: allow persistent storage rules for zram devices
The /dev/zramN devices can be used as regular block devices. They are
typically used for swap areas, but it would be beneficial to have
LABEL and UUID in the udev database to make it more user-friendly for
tools such as lsblk or mount (if used with other filesystems).
Such a policy won't provide any protection, but it's still entirely fine
to have it like this in various contexts, for example at OS install
time, to allocate the nvindex and reference it in enrollments. However,
it does deserve mention, hence log about it at LOG_NOTICE level.
This is based on a similar patch by Arnaud Patard
<arnaud.patard@collabora.com> proposed at #33663.
It is not true that "no string" is written to journal; the binary
name is used when run via `systemd-cat command`, or `cat` is used
when run via `command | systemd-cat`.
TEST-64-UDEV-STORAGE is invoked with the subtest appended, so TEST_SKIP=TEST-64-UDEV-STORAGE
does not work. Fix it by using TEST_SKIP as a partial match.
These variables closely mirror the existing
LoaderDevicePartUUID/LoaderImageIdentifier variables. But the Stub…
variables indicate the location of the stub/UKI (i.e. of systemd-stub),
while the Loader… variables indicate the location of the boot loader
(i.e. of systemd-boot). (Except of course, there is no boot loader used,
in which case both sets point to the stub/UKI, as a special case).
This actually matters, as we support that sd-boot runs off the ESP,
while a UKI then runs off XBOOTLDR, i.e. two distinct partitions.
First of all, these were always set, i.e. since sd-boot was merged into
our tree, i.e. v220. Let's say so explicitly.
Also, let's be more accurate, regarding which partition this referes to:
it's usually "the" ESP, but given that you can make firmware boot from
arbitrary disks, it could be any other partition too. Hence, be
explicit on this.
Also, clarify tha sd-stub will set this too, if sd-boot never set it.
src/sysext: Use versioned names when logging extensions used for merge operation
If this is not done, and there are two images, image_1.raw and image_2.raw under
an image.raw.v folder, then the log will say "Using extensions image" instead of
using "Using extensions image_2.raw" which is the desired behavior for v-picked extensions.
meson: increase default number of available sections for the stub
Now that we have multi-profile UKIs people likely want to stick more PE
sections into them than before. Hence, bump the number of available PE
section slots to 30 (up from 15). Also, make this configurable at build
time since some folks probably want even more, and others don't want
this at all.
(pre-allocating too many shouldn't matter too much btw, I'd advise
everyone to overshoot, except maybe on the tiniest of embedded boards)
cryptsetup: use the new crypt_token_set_external_path() API if available
Let's make use of libcryptsetup's new crypt_token_set_external_path()
API in place of the interposition stuff we have been doing before. Let's
kill it entirely, given that this was a developer feature only anyway
(and guarded by an appropriate ifdef).
homectl: when chainloading a shell, prefix "-" rather than overriding first char
Login shells are supposed to marked via a dash as first char. We follow
that logic, but right now we simply overwrite the first char of the
shell. That might not be the right choice, given that this turns
"zsh" into "-sh", which suggests some bourne shell process.
Hence, let's correct things, and instead prefix a dash, which should be
safer.
Inspired by findings on https://github.com/systemd/systemd/issues/34153#issuecomment-2338104907
stub: add ability to place multiple alternative PE sections of a specific type in the same UKI ("Multi-Profile UKIs")
This adds a ability to add alternative sections of a specific type in
the same UKI. The primary usecase is for supporting multiple different
kernel cmdlines that are baked into a UKI.
The mechanism is relatively simple (I think), in order to make it robust.
1. A new PE section ".profile" is introduced, that is a lot like
".osrel", but contains information about a specific "profile" to
boot. The ".profile" section can appear multiple times in the same
PE, and acts as delimiter indicating where a new profile starts.
Everything before the first ".profile" is called the "base profile",
and is shared among all other profiles, which can then override or
add addition PE sections on top.
2. An UKI's command line can be prefixed with an argument such as "@0" or
"@1" or "@2" which indicates the "profile" to boot. If no argument is
specified the default is profile 0. Also, a UKI that lacks any
.profile section is treated like one with only a profile 0, but with
no data in that profile section.
3. The stub will first search for its usual set of PE sections
(hereafter called "base sections"), and stop at the first .profile PE
section if any. It will then find the .profile matching the selected
profile by its index, and any sections found as part of that profile
on top of the base sections.
And that's already it.
Example: let's say a distro wants to provide a single UKI that can be
invoked in one of three ways:
1. The regular profile that just boots the system
2. A profile that boots into storagetm
3. A profile that initiates factory reset and reboots.
For this it would define a classic UKI with sections .linux, .initrd,
.cmdline, and whatever else it needs. The .cmdline section would contain
the kernel command line for the regular profile.
It would then insert one ".profile" section, with a contents like the
following:
ID=regular
This is the profile for profile 0. It would immediately afterwards add
another ".profile" section:
ID=storagetm
TITLE=Boot into Storage Target Mode
This would then followed with a .cmdline section that is just like the
basic one, but with "rd.systemd.unit=storage-target-mode.target"
suffixed. Then, another .profile section would be added:
ID=factory-reset
TITLE=Factory Reset
Which is then followed by one last PE section: a .cmdline one with
"systemd.unit=factory-reset.target" suffixed to te regular command line.
i.e. expressed in tabular form the above would be:
The base profile:
.linux
.initrd
.cmdline
.osrel
The regular boot profile:
.profile
The storagetm profile:
.profile
.cmdline
The factory reset profile:
.profile
.cmdline
You might wonder why the first .cmdline in the list above is placed in
the base profile rather than in the regular boot profile, given that it
is overriden in all other profiles anyway. And you are right. The only
reason I'd place it in the base profile is that it makes the UKI more
nicely extensible if later profiles are added that want to replace
something else instead of the .cmdline, for example .ucode or so. But it
really doesn't matter much.
While the primary usecase is of course multiple alternative command
lines, the concept is more powerful than that: for various usecases it
might be valuable to offer multiple choices of devicetree, ucode or
initrds.
The .profile contents is also passed to the invoked kernel as a file in
/.extra/profile (via a synthetic initrd). Thus, this functionality can
even be useful without overriding any section at all, simply by means of
reading that file from userspace.
Design choices:
1. On purposes I used a special command line marker (i.e. the "@" thing,
which maybe we should call the "profile selector"), that doesn't look
like a regular kernel command line option. This is because this is
really not a regular kernel command line option – we process it in
the stub, then remove it as prefix, and measure the unprefixed
command line only after that. The kernel will not see the profile
selector either. I think these special semantics are best
communicated by making it look substantially different from regular
options.
2. This moves around measurements a bit. Previously we measured our UKI
sections right after finding them. Now we first parse the profile
number from the command line, then search for the profile's sections,
and only then measure the sections we actually end up using for this
profile. I think that this logic makes most sense: measure what we
are using, not what we are overriding. Or in other words, if you boot
profile @3, then we'll measure .cmdline (assuming it exists) of
profile 3, and *not* measure .cmdline of the base profile. Also note
that if the user passes in a custom kernel command line via command
line arguments we'll strip off the profile selector (i.e. the initial
"@X" thing) before we pass it on.
3. The .profile stuff is supposed to be generic and extensible. For
example we could use it in future to mark "dangerous" options such as
factory reset, so that boot menus can ask for confirmation before
booting into it. Or we could introduce match expressions against
SMBIOS or other system identifiers, to filter out profiles on
specific hw.
Note btw, that PE allows defining multiple sections that point to the
same offsets in the file. This allows sharing payload under different
names. For example, if profile @4 and @7 shall carry the same .ucode
section, they can define .ucode in each profile and then make it point to
the same offset.
Also note that that one can even "mask" a base section in a profile, by
inserting an empty section. For example, if the base .dtb section should
not be used for profile @4, then add a section .dtb right after the
fourth .profile with a zero size to the UKI, and you will get your wish
fulfilled.
This code only contains changes to sd-stub. A follow-up commit will
teach sd-boot to also find this profile PE sections to synthesize
additional menu entries from a single UKI.
A later commit will add support for gnerating this via ukify.
In mkosi, I want to add a sysupdate verb to wrap systemd-sysupdate.
The definitions will be picked up from mkosi.sysupdate/ and passed
to systemd-sysupdate. I want users to be able to write transfer
definitions that are independent of the output directory used by
mkosi. To make this possible, it should be possible to specify the
directory that transfer sources should be looked up in on the sysupdate
command line. Let's allow this via a new --transfer-source= option.
Additionally, transfer sources that want to take advantage of this
feature should specify PathRelativeTo=directory to indicate the configured
Path= is interpreted relative to the tranfer source directory specified
on the CLI.
This allows for the following transfer definition to be put in
mkosi.sysupdate:
projects / thirdparty / systemd.git / log
