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man: add man page for the systemd UEFI stub Fixes: #17215
2021-09-21 17:52:24 +03:00
<?xml version='1.0'?> <!--*-nxml-*-->
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
man: use same version in public and system ident.
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"http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd">
man: add man page for the systemd UEFI stub Fixes: #17215
2021-09-21 17:52:24 +03:00
<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
tree-wide: Drop gnu-efi This drops all mentions of gnu-efi and its manual build machinery. A future commit will bring bootloader builds back. A new bootloader meson option is now used to control whether to build sd-boot and its userspace tooling.
2023-02-26 16:09:44 +03:00
<refentry id="systemd-stub" conditional='ENABLE_BOOTLOADER'
man: add man page for the systemd UEFI stub Fixes: #17215
2021-09-21 17:52:24 +03:00
xmlns:xi="http://www.w3.org/2001/XInclude">
<refentryinfo>
<title>systemd-stub</title>
<productname>systemd</productname>
</refentryinfo>
<refmeta>
<refentrytitle>systemd-stub</refentrytitle>
<manvolnum>7</manvolnum>
</refmeta>
<refnamediv>
<refname>systemd-stub</refname>
man: also install systemd-stub man page as sd-stub So, typically systemd-boot is referenced as sd-boot, due to te usual shorter naming in ESP resources. systemd-stub didnt do that so far, since it never appears as separate files in the ESP. However it's super annoying that you can find "man sd-boot", but not the very closely related "man sd-stub". Let's fix that, and also add an "sd-stub" alias to the "systemd-stub" man page.
2022-03-22 02:19:32 +03:00
<refname>sd-stub</refname>
man: add man page for the systemd UEFI stub Fixes: #17215
2021-09-21 17:52:24 +03:00
<refname>linuxx64.efi.stub</refname>
<refname>linuxia32.efi.stub</refname>
<refname>linuxaa64.efi.stub</refname>
<refpurpose>A simple UEFI kernel boot stub</refpurpose>
</refnamediv>
<refsynopsisdiv>
man: use <simplelist> for file lists in synopsis With <para><filename>…</filename></para>, we get a separate "paragraph" for each line, i.e. entries separated by empty lines. This uses up a lot of space and was only done because docbook makes it hard to insert a newline. In some other places, <literallayout> was used, but then we cannot indent the source text (because the whitespace would end up in the final page). We can get the desired result with <simplelist>. With <simplelist> the items are indented in roff output, but not in html output. In some places this looks better then no indentation, and in others it would probably be better to have no indent. But this is a minor issue and we cannot control that. (I didn't convert all spots. There's a bunch of other man pages which have two lines, e.g. an executable and service file, and it doesn't matter there so much.)
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<para><simplelist>
<member><filename>/usr/lib/systemd/boot/efi/linuxx64.efi.stub</filename></member>
<member><filename>/usr/lib/systemd/boot/efi/linuxia32.efi.stub</filename></member>
<member><filename>/usr/lib/systemd/boot/efi/linuxaa64.efi.stub</filename></member>
<member><filename><replaceable>ESP</replaceable>/.../<replaceable>foo</replaceable>.efi.extra.d/*.addon.efi</filename></member>
<member><filename><replaceable>ESP</replaceable>/.../<replaceable>foo</replaceable>.efi.extra.d/*.cred</filename></member>
<member><filename><replaceable>ESP</replaceable>/.../<replaceable>foo</replaceable>.efi.extra.d/*.raw</filename></member>
stub: pick up confexts from the ESP as well This does what we do for system extension also for configuration extension. This is complicated by the fact that we previously looked for <uki-binary>.d/*.raw for system extensions. We want to measure sysexts and confexts to different PCRs (13 vs. 12) hence we must distinguish them, but *.raw would match both kinds. This commit solves this via the following mechanism: we'll load confexts from *.confext.raw and sysexts from *.raw but will then enclude *.confext.raw from the latter. This preserves compatibility but allows us to somewhat reasonable distinguish both types of images. The documentation is updated not going into this detail though, and instead now claims that sysexts shall be *.sysext.raw and confexts *.confext.raw even though we actually are more lenient than this. This is simply to push people towards using the longer, more descriptive suffixes. I added an XML comment (<!-- … -->) about this to the docs, so that whenever somebody notices the difference between code and docs understands why and leaves it that way.
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<member><filename><replaceable>ESP</replaceable>/.../<replaceable>foo</replaceable>.efi.extra.d/*.sysext.raw</filename></member>
<member><filename><replaceable>ESP</replaceable>/.../<replaceable>foo</replaceable>.efi.extra.d/*.confext.raw</filename></member>
man: use <simplelist> for file lists in synopsis With <para><filename>…</filename></para>, we get a separate "paragraph" for each line, i.e. entries separated by empty lines. This uses up a lot of space and was only done because docbook makes it hard to insert a newline. In some other places, <literallayout> was used, but then we cannot indent the source text (because the whitespace would end up in the final page). We can get the desired result with <simplelist>. With <simplelist> the items are indented in roff output, but not in html output. In some places this looks better then no indentation, and in others it would probably be better to have no indent. But this is a minor issue and we cannot control that. (I didn't convert all spots. There's a bunch of other man pages which have two lines, e.g. an executable and service file, and it doesn't matter there so much.)
2023-12-14 14:52:03 +03:00
<member><filename><replaceable>ESP</replaceable>/loader/addons/*.addon.efi</filename></member>
<member><filename><replaceable>ESP</replaceable>/loader/credentials/*.cred</filename></member>
</simplelist></para>
man: add man page for the systemd UEFI stub Fixes: #17215
2021-09-21 17:52:24 +03:00
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para><command>systemd-stub</command> (stored in per-architecture files
<filename>linuxx64.efi.stub</filename>, <filename>linuxia32.efi.stub</filename>,
<filename>linuxaa64.efi.stub</filename> on disk) is a simple UEFI boot stub. An UEFI boot stub is
attached to a Linux kernel binary image, and is a piece of code that runs in the UEFI firmware
environment before transitioning into the Linux kernel environment. The UEFI boot stub ensures a Linux
kernel is executable as regular UEFI binary, and is able to do various preparations before switching the
system into the Linux world.</para>
<para>The UEFI boot stub looks for various resources for the kernel invocation inside the UEFI PE binary
man: say early what a unified kernel image/UKI is
2022-09-09 12:24:12 +03:00
itself. This allows combining various resources inside a single PE binary image (usually called "Unified
Kernel Image", or "UKI" for short), which may then be signed via UEFI SecureBoot as a whole, covering all
individual resources at once. Specifically it may include:</para>
man: add man page for the systemd UEFI stub Fixes: #17215
2021-09-21 17:52:24 +03:00
<itemizedlist>
man: drop duplicate .uname documentation, add .sbat documentation This fixes the PE section documentation in the systemd-stub man page: for some reason .uname was listed twice, and .sbat was still missing. Address that. Also, let's reorder things to to match the "canonical" ordering we also use for measurement in sd-stub. The order makes sense and there's really no reason to depart from that here. Minor other tweaks. Reverts b6f2e6860220aa89550f690b12246c4e8eb6e908, among other things
2023-09-18 12:08:55 +03:00
<!-- Let's keep this in the canonical order we also measure the sections by, i.e. as in
src/fundamental/uki.h's UnifiedSection enum -->
man: reword the list of PE sections in systemd-stub Let's put the section name at the beginning of each sentence. This way we can avoid awkward constructs like "kernel is looked for in the .linux section". Also, since the paragraph above says that this is a list of "PE sections", we can just say "section". In other places, it is often useful to say "PE section" to avoid ambiguity. Also fix the off-by-one in the count of sections.
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<listitem><para>A <literal>.linux</literal> section with the ELF Linux kernel image.</para></listitem>
man: add man page for the systemd UEFI stub Fixes: #17215
2021-09-21 17:52:24 +03:00
man: reword the list of PE sections in systemd-stub Let's put the section name at the beginning of each sentence. This way we can avoid awkward constructs like "kernel is looked for in the .linux section". Also, since the paragraph above says that this is a list of "PE sections", we can just say "section". In other places, it is often useful to say "PE section" to avoid ambiguity. Also fix the off-by-one in the count of sections.
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<listitem><para>An <literal>.osrel</literal> section with OS release information, i.e. the contents of
the <citerefentry><refentrytitle>os-release</refentrytitle><manvolnum>5</manvolnum></citerefentry> file
of the OS the kernel belongs to.</para></listitem>
efi: from the stub measure the ELF kernel + built-in initrd and so on into PCR 11 Here we grab a new – on Linux so far unused (by my Googling skills, that is) – and measure all static components of the PE kernel image into. This is useful since for the first time we'll have a PCR that contains only a PCR of the booted kernel, nothing else. That allows putting together TPM policies that bind to a specific kernel (+ builtin initrd), without having to have booted that kernel first. PCRs can be pre-calculated. Yay! You might wonder, why we measure just the discovered PE sections we are about to use, instead of the whole PE image. That's because of the next step I have in mind: PE images should also be able to carry an additional section that contains a signature for its own expected, pre-calculated PCR values. This signature data should then be passed into the booted kernel and can be used there in TPM policies. Benefit: TPM policies can now be bound to *signatures* of PCRs, instead of the raw hash values themselves. This makes update management a *lot* easier, as policies don't need to be updated whenever a kernel is updated, as long as the signature is available. Now, if the PCR signature is embedded in the kernel PE image it cannot be of a PCR hash of the kernel PE image itself, because that would be a chicken-and-egg problem. Hence, by only measuring the relavent payload sections (and that means excluding the future section that will contain the PCR hash signature) we avoid this problem, naturally.
2022-07-25 18:44:24 +03:00
man: reword the list of PE sections in systemd-stub Let's put the section name at the beginning of each sentence. This way we can avoid awkward constructs like "kernel is looked for in the .linux section". Also, since the paragraph above says that this is a list of "PE sections", we can just say "section". In other places, it is often useful to say "PE section" to avoid ambiguity. Also fix the off-by-one in the count of sections.
2023-11-24 17:19:50 +03:00
<listitem><para>A <literal>.cmdline</literal> section with the kernel command line to pass to the
invoked kernel.</para></listitem>
man: drop duplicate .uname documentation, add .sbat documentation This fixes the PE section documentation in the systemd-stub man page: for some reason .uname was listed twice, and .sbat was still missing. Address that. Also, let's reorder things to to match the "canonical" ordering we also use for measurement in sd-stub. The order makes sense and there's really no reason to depart from that here. Minor other tweaks. Reverts b6f2e6860220aa89550f690b12246c4e8eb6e908, among other things
2023-09-18 12:08:55 +03:00
man: reword the list of PE sections in systemd-stub Let's put the section name at the beginning of each sentence. This way we can avoid awkward constructs like "kernel is looked for in the .linux section". Also, since the paragraph above says that this is a list of "PE sections", we can just say "section". In other places, it is often useful to say "PE section" to avoid ambiguity. Also fix the off-by-one in the count of sections.
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<listitem><para>An <literal>.initrd</literal> section with the initrd.</para></listitem>
stub/measure: document and measure .uname UKI section
2023-05-21 16:32:09 +03:00
stub: Add support for .ucode UKI section This commit adds support for loading, measuring and handling a ".ucode" UKI section. This section is functionally an initrd, intended for microcode updates. As such it will always be passed to the kernel first.
2024-04-02 13:54:30 +03:00
<listitem><para>A <literal>.ucode</literal> section with an initrd containing microcode, to be handed
to the kernel before any other initrd. This initrd must not be compressed.</para></listitem>
man: reword the list of PE sections in systemd-stub Let's put the section name at the beginning of each sentence. This way we can avoid awkward constructs like "kernel is looked for in the .linux section". Also, since the paragraph above says that this is a list of "PE sections", we can just say "section". In other places, it is often useful to say "PE section" to avoid ambiguity. Also fix the off-by-one in the count of sections.
2023-11-24 17:19:50 +03:00
<listitem><para>A <literal>.splash</literal> section with an image (in the Windows
<filename>.BMP</filename> format) to show on screen before invoking the kernel.</para></listitem>
man: add man page for the systemd UEFI stub Fixes: #17215
2021-09-21 17:52:24 +03:00
man: reword the list of PE sections in systemd-stub Let's put the section name at the beginning of each sentence. This way we can avoid awkward constructs like "kernel is looked for in the .linux section". Also, since the paragraph above says that this is a list of "PE sections", we can just say "section". In other places, it is often useful to say "PE section" to avoid ambiguity. Also fix the off-by-one in the count of sections.
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<listitem><para>A <literal>.dtb</literal> section with a compiled binary DeviceTree.</para></listitem>
[st-stub] documenting the .dtb section
2021-10-16 14:26:21 +03:00
man: reword the list of PE sections in systemd-stub Let's put the section name at the beginning of each sentence. This way we can avoid awkward constructs like "kernel is looked for in the .linux section". Also, since the paragraph above says that this is a list of "PE sections", we can just say "section". In other places, it is often useful to say "PE section" to avoid ambiguity. Also fix the off-by-one in the count of sections.
2023-11-24 17:19:50 +03:00
<listitem><para>A <literal>.uname</literal> section with the kernel version information, i.e. the
output of <command>uname -r</command> for the kernel included in the <literal>.linux</literal>
section.</para></listitem>
stub: measure SMBIOS kernel-cmdline-extra in PCR12 PCR1, where SMBIOS strings are measured, is filled with data that is not under the control of the machine owner. Measure cmdline extensions in PCR12 too, where we measure other optional addons that are loaded by sd-stub.
2023-05-21 17:18:21 +03:00
man: reword the list of PE sections in systemd-stub Let's put the section name at the beginning of each sentence. This way we can avoid awkward constructs like "kernel is looked for in the .linux section". Also, since the paragraph above says that this is a list of "PE sections", we can just say "section". In other places, it is often useful to say "PE section" to avoid ambiguity. Also fix the off-by-one in the count of sections.
2023-11-24 17:19:50 +03:00
<listitem><para>An <literal>.sbat</literal> section with
<ulink url="https://github.com/rhboot/shim/blob/main/SBAT.md">SBAT</ulink> revocation
metadata.</para></listitem>
man: document the new .pcrsig/.pcrpkey sections for unified kernel images
2022-09-09 12:08:35 +03:00
man: reword the list of PE sections in systemd-stub Let's put the section name at the beginning of each sentence. This way we can avoid awkward constructs like "kernel is looked for in the .linux section". Also, since the paragraph above says that this is a list of "PE sections", we can just say "section". In other places, it is often useful to say "PE section" to avoid ambiguity. Also fix the off-by-one in the count of sections.
2023-11-24 17:19:50 +03:00
<listitem><para>A <literal>.pcrsig</literal> section with a set of cryptographic signatures for the
expected TPM2 PCR values after the kernel has been booted, in JSON format. This is useful for
implementing TPM2 policies that bind disk encryption and similar to kernels that are signed by a
specific key.</para></listitem>
man: document the new .pcrsig/.pcrpkey sections for unified kernel images
2022-09-09 12:08:35 +03:00
man: reword the list of PE sections in systemd-stub Let's put the section name at the beginning of each sentence. This way we can avoid awkward constructs like "kernel is looked for in the .linux section". Also, since the paragraph above says that this is a list of "PE sections", we can just say "section". In other places, it is often useful to say "PE section" to avoid ambiguity. Also fix the off-by-one in the count of sections.
2023-11-24 17:19:50 +03:00
<listitem><para>A <literal>.pcrpkey</literal> section with a public key in the PEM format matching the
signature data in the the <literal>.pcrsig</literal> section.</para></listitem>
man: add man page for the systemd UEFI stub Fixes: #17215
2021-09-21 17:52:24 +03:00
</itemizedlist>
<para>If UEFI SecureBoot is enabled and the <literal>.cmdline</literal> section is present in the executed
image, any attempts to override the kernel command line by passing one as invocation parameters to the
EFI binary are ignored. Thus, in order to allow overriding the kernel command line, either disable UEFI
SecureBoot, or don't include a kernel command line PE section in the kernel image file. If a command line
man: update TPM2 PCR documentation The assignments were partly simply incorrectly documented, partly changed with 4d32507f5186a89e98093659fbbe386787a97b9f and partly missing. Moreover kernel 5.17 now measures all initrds to PCR 9 on its own (https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=f046fff8bc4c4d8f8a478022e76e40b818f692df) Let's correct all this and bring it up-to-date. And while we are at it extend the docs about this in systemd-stub, with a new table that indicates which OS resource is protected by which PCR.
2022-04-14 15:38:52 +03:00
is accepted via EFI invocation parameters to the EFI binary it is measured into TPM PCR 12 (if a TPM is
man: add man page for the systemd UEFI stub Fixes: #17215
2021-09-21 17:52:24 +03:00
present).</para>
[st-stub] documenting the .dtb section
2021-10-16 14:26:21 +03:00
<para>If a DeviceTree is embedded in the <literal>.dtb</literal> section, it replaces an existing
DeviceTree in the corresponding EFI configuration table. systemd-stub will ask the firmware via the
<literal>EFI_DT_FIXUP_PROTOCOL</literal> for hardware specific fixups to the DeviceTree.</para>
efi: from the stub measure the ELF kernel + built-in initrd and so on into PCR 11 Here we grab a new – on Linux so far unused (by my Googling skills, that is) – and measure all static components of the PE kernel image into. This is useful since for the first time we'll have a PCR that contains only a PCR of the booted kernel, nothing else. That allows putting together TPM policies that bind to a specific kernel (+ builtin initrd), without having to have booted that kernel first. PCRs can be pre-calculated. Yay! You might wonder, why we measure just the discovered PE sections we are about to use, instead of the whole PE image. That's because of the next step I have in mind: PE images should also be able to carry an additional section that contains a signature for its own expected, pre-calculated PCR values. This signature data should then be passed into the booted kernel and can be used there in TPM policies. Benefit: TPM policies can now be bound to *signatures* of PCRs, instead of the raw hash values themselves. This makes update management a *lot* easier, as policies don't need to be updated whenever a kernel is updated, as long as the signature is available. Now, if the PCR signature is embedded in the kernel PE image it cannot be of a PCR hash of the kernel PE image itself, because that would be a chicken-and-egg problem. Hence, by only measuring the relavent payload sections (and that means excluding the future section that will contain the PCR hash signature) we avoid this problem, naturally.
2022-07-25 18:44:24 +03:00
man: reword the list of PE sections in systemd-stub Let's put the section name at the beginning of each sentence. This way we can avoid awkward constructs like "kernel is looked for in the .linux section". Also, since the paragraph above says that this is a list of "PE sections", we can just say "section". In other places, it is often useful to say "PE section" to avoid ambiguity. Also fix the off-by-one in the count of sections.
2023-11-24 17:19:50 +03:00
<para>The contents of eight of these nine sections are measured into TPM PCR 11. It is otherwise not used
and thus the result can be pre-calculated without too much effort. The <literal>.pcrsig</literal> section
is not included in this PCR measurement, since it is supposed to contain signatures for the output of the
measurement operation, and thus cannot also be input to it.</para>
man: document the new .pcrsig/.pcrpkey sections for unified kernel images
2022-09-09 12:08:35 +03:00
man: reword the list of PE sections in systemd-stub Let's put the section name at the beginning of each sentence. This way we can avoid awkward constructs like "kernel is looked for in the .linux section". Also, since the paragraph above says that this is a list of "PE sections", we can just say "section". In other places, it is often useful to say "PE section" to avoid ambiguity. Also fix the off-by-one in the count of sections.
2023-11-24 17:19:50 +03:00
<para>When <literal>.pcrsig</literal> and/or <literal>.pcrpkey</literal> sections are present in a
unified kernel image their contents are passed to the booted kernel in an synthetic initrd cpio archive
that places them in the <filename>/.extra/tpm2-pcr-signature.json</filename> and
man: document the new .pcrsig/.pcrpkey sections for unified kernel images
2022-09-09 12:08:35 +03:00
<filename>/.extra/tpm2-pcr-public-key.pem</filename> files. Typically, a
<citerefentry><refentrytitle>tmpfiles.d</refentrytitle><manvolnum>5</manvolnum></citerefentry> line then
ensures they are copied into <filename>/run/systemd/tpm2-pcr-signature.json</filename> and
<filename>/run/systemd/tpm2-pcr-public-key.pem</filename> where they remain accessible even after the
system transitions out of the initrd environment into the host file system. Tools such
<citerefentry><refentrytitle>systemd-cryptsetup@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd-cryptenroll</refentrytitle><manvolnum>1</manvolnum></citerefentry>
and <citerefentry><refentrytitle>systemd-creds</refentrytitle><manvolnum>1</manvolnum></citerefentry>
will automatically use files present under these paths to unlock protected resources (encrypted storage
or credentials) or bind encryption to booted kernels.</para>
man: link UKI spec from sd-stub
2023-09-18 12:19:17 +03:00
<para>For further details about the UKI concept, see the <ulink
url="https://uapi-group.org/specifications/specs/unified_kernel_image/">UKI specification</ulink>.</para>
man: add man page for the systemd UEFI stub Fixes: #17215
2021-09-21 17:52:24 +03:00
</refsect1>
<refsect1>
<title>Companion Files</title>
man: fix counting of resource types
2023-09-18 12:19:26 +03:00
<para>The <command>systemd-stub</command> UEFI boot stub automatically collects three types of auxiliary
stub: Load credentials from \loader\credentials\*.cred Some types of credentials that a user would want to pass into the initrd do not depend on the specific kernel/initrd version. For instance, this can include SSH keys, rootfs encryption keys, dm-integrity keys, and so on. This introduces a directory where such credentials can be placed so that any kernel image will load them
2021-12-08 05:21:40 +03:00
companion files optionally placed in drop-in directories on the same partition as the EFI binary,
dynamically generates <command>cpio</command> initrd archives from them, and passes them to the kernel.
Specifically:</para>
man: add man page for the systemd UEFI stub Fixes: #17215
2021-09-21 17:52:24 +03:00
<itemizedlist>
stub: Load credentials from \loader\credentials\*.cred Some types of credentials that a user would want to pass into the initrd do not depend on the specific kernel/initrd version. For instance, this can include SSH keys, rootfs encryption keys, dm-integrity keys, and so on. This introduces a directory where such credentials can be placed so that any kernel image will load them
2021-12-08 05:21:40 +03:00
<listitem><para>For a kernel binary called <filename><replaceable>foo</replaceable>.efi</filename>, it
man: add man page for the systemd UEFI stub Fixes: #17215
2021-09-21 17:52:24 +03:00
will look for files with the <filename>.cred</filename> suffix in a directory named
stub: Ignore the boot counter when looking for .extra.d directory If `foo+3-0.efi` is booted when there are some files in `foo.efi.extra.d`, those files are ignored. But after the boot is blessed and the system rebooted, those file are taken into account, and the boot is different from first boot. This behavior is a bit puzzling. Instead we now ignore the counter and always look for the extra files in `foo.efi.extra.d` and always boot the same way.
2023-10-20 00:13:45 +03:00
<filename><replaceable>foo</replaceable>.efi.extra.d/</filename> next to it. If the kernel binary
uses a counter for the purpose of
<ulink url="https://systemd.io/AUTOMATIC_BOOT_ASSESSMENT">Automatic Boot Assessment</ulink>, this
counter will be ignored. For example, <filename><replaceable>foo</replaceable>+3-0.efi</filename>
will look in directory <filename><replaceable>foo</replaceable>.efi.extra.d/</filename>.
A <command>cpio</command>
man: add man page for the systemd UEFI stub Fixes: #17215
2021-09-21 17:52:24 +03:00
archive is generated from all files found that way, placing them in the
<filename>/.extra/credentials/</filename> directory of the initrd file hierarchy. The main initrd may
then access them in this directory. This is supposed to be used to store auxiliary, encrypted,
authenticated credentials for use with <varname>LoadCredentialEncrypted=</varname> in the UEFI System
Partition. See
man: various issues reported in #22432 Fixes #22432.
2022-02-23 00:54:23 +03:00
<citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>
and
<citerefentry><refentrytitle>systemd-creds</refentrytitle><manvolnum>1</manvolnum></citerefentry>
for
man: add man page for the systemd UEFI stub Fixes: #17215
2021-09-21 17:52:24 +03:00
details on encrypted credentials. The generated <command>cpio</command> archive is measured into TPM
man: update TPM2 PCR documentation The assignments were partly simply incorrectly documented, partly changed with 4d32507f5186a89e98093659fbbe386787a97b9f and partly missing. Moreover kernel 5.17 now measures all initrds to PCR 9 on its own (https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=f046fff8bc4c4d8f8a478022e76e40b818f692df) Let's correct all this and bring it up-to-date. And while we are at it extend the docs about this in systemd-stub, with a new table that indicates which OS resource is protected by which PCR.
2022-04-14 15:38:52 +03:00
PCR 12 (if a TPM is present).</para></listitem>
man: add man page for the systemd UEFI stub Fixes: #17215
2021-09-21 17:52:24 +03:00
stub: pick up confexts from the ESP as well This does what we do for system extension also for configuration extension. This is complicated by the fact that we previously looked for <uki-binary>.d/*.raw for system extensions. We want to measure sysexts and confexts to different PCRs (13 vs. 12) hence we must distinguish them, but *.raw would match both kinds. This commit solves this via the following mechanism: we'll load confexts from *.confext.raw and sysexts from *.raw but will then enclude *.confext.raw from the latter. This preserves compatibility but allows us to somewhat reasonable distinguish both types of images. The documentation is updated not going into this detail though, and instead now claims that sysexts shall be *.sysext.raw and confexts *.confext.raw even though we actually are more lenient than this. This is simply to push people towards using the longer, more descriptive suffixes. I added an XML comment (<!-- … -->) about this to the docs, so that whenever somebody notices the difference between code and docs understands why and leaves it that way.
2023-11-08 21:02:03 +03:00
<listitem><para>Similarly, files
<filename><replaceable>foo</replaceable>.efi.extra.d/*.sysext.raw</filename> are packed up in a
<command>cpio</command> archive and placed in the <filename>/.extra/sysext/</filename> directory in the
initrd file hierarchy. This is supposed to be used to pass additional system extension images to the
initrd. See
man: add man page for the systemd UEFI stub Fixes: #17215
2021-09-21 17:52:24 +03:00
<citerefentry><refentrytitle>systemd-sysext</refentrytitle><manvolnum>8</manvolnum></citerefentry> for
details on system extension images. The generated <command>cpio</command> archive containing these
sd-stub: measure sysext images picked up by sd-stub into PCR 13 Let's grab another so far unused PCR, and measure all sysext images into it that we load from the ESP. Note that this is possibly partly redundant, since sysext images should have dm-verity enabled, and that is hooked up to IMA. However, measuring this explicitly has the benefit that we can measure filenames too, easily, and that all without need for IMA or anything like that. This means: when booting a unified sd-stub kernel through sd-boot we'll now have: 1. PCR 11: unified kernel image payload (i.e. kernel, initrd, boot splash, dtb, osrelease) 2. PCR 12: kernel command line (i.e. the one embedded in the image, plus optionally an overriden one) + any credential files picked up by sd-stub 3. PCR 13: sysext images picked up by sd-stub And each of these three PCRs should carry just the above, and start from zero, thus be pre-calculatable. Thus, all components and parameters of the OS boot process (i.e. everything after the boot loader) is now nicely pre-calculable. NOTE: this actually replaces previous measuring of the syext images into PCR 4. I added this back in 845707aae23b3129db635604edb95c4048a5922a, following the train of thought, that sysext images for the initrd should be measured like the initrd itself they are for, and according to my thinking that would be a unified kernel which is measured by firmware into PCR 4 like any other UEFI executables. However, I think we should depart from that idea. First and foremost that makes it harder to pre-calculate PCR 4 (since we actually measured quite incompatible records to the TPM event log), but also I think there's great value in being able to write policies that bind to the used sysexts independently of the earlier boot chain (i.e. shim, boot loader, unified kernel), hence a separate PCR makes more sense. Strictly speaking, this is a compatibility break, but I think one we can get away with, simply because the initrd sysext images are currently not picked up by systemd-sysext yet in the initrd, and because of that we can be reasonably sure noone uses this yet, and hence relies on the PCR register used. Hence, let's clean this up before people actually do start relying on this.
2022-07-26 12:35:57 +03:00
system extension images is measured into TPM PCR 13 (if a TPM is present).</para></listitem>
stub: Load credentials from \loader\credentials\*.cred Some types of credentials that a user would want to pass into the initrd do not depend on the specific kernel/initrd version. For instance, this can include SSH keys, rootfs encryption keys, dm-integrity keys, and so on. This introduces a directory where such credentials can be placed so that any kernel image will load them
2021-12-08 05:21:40 +03:00
stub: pick up confexts from the ESP as well This does what we do for system extension also for configuration extension. This is complicated by the fact that we previously looked for <uki-binary>.d/*.raw for system extensions. We want to measure sysexts and confexts to different PCRs (13 vs. 12) hence we must distinguish them, but *.raw would match both kinds. This commit solves this via the following mechanism: we'll load confexts from *.confext.raw and sysexts from *.raw but will then enclude *.confext.raw from the latter. This preserves compatibility but allows us to somewhat reasonable distinguish both types of images. The documentation is updated not going into this detail though, and instead now claims that sysexts shall be *.sysext.raw and confexts *.confext.raw even though we actually are more lenient than this. This is simply to push people towards using the longer, more descriptive suffixes. I added an XML comment (<!-- … -->) about this to the docs, so that whenever somebody notices the difference between code and docs understands why and leaves it that way.
2023-11-08 21:02:03 +03:00
<!-- Note: the actual suffix we look for for sysexts is just *.raw (not *.sysext.raw), for
compatibility reasons with old versions. But we want people to name their system extensions
properly, hence we document the *.sysext.raw suffix only. -->
<listitem><para>Similarly, files
<filename><replaceable>foo</replaceable>.efi.extra.d/*.confext.raw</filename> are packed up in a
<command>cpio</command> archive and placed in the <filename>/.extra/confext/</filename> directory in
the initrd file hierarchy. This is supposed to be used to pass additional configuration extension
images to the initrd. See
<citerefentry><refentrytitle>systemd-confext</refentrytitle><manvolnum>8</manvolnum></citerefentry> for
details on configuration extension images. The generated <command>cpio</command> archive containing
these system extension images is measured into TPM PCR 12 (if a TPM is present).</para></listitem>
stub: allow loading and verifying cmdline addons Files placed in /EFI/Linux/UKI.efi.extra.d/ and /loader/addons/ are opened and verified using the LoadImage protocol, and will thus get verified via shim/firmware. If they are valid signed PE files, the .cmdline section will be extracted and appended. If there are multiple addons in each directory, they will be parsed in alphanumerical order. Optionally the .uname sections are also matched if present, so that they can be used to filter out addons as well if needed, and only addons that correspond exactly to the UKI being loaded are used. It is recommended to also always add a .sbat section to addons, so that they can be mass-revoked with just a policy update. The files must have a .addon.efi suffix. Files in the per-UKI directory are parsed, sorted, measured and appended first. Then, files in the generic directory are processed.
2023-05-12 02:55:58 +03:00
<listitem><para>Similarly, files
man/systemd-stub: split and simplify a wall'o'text paragraph
2023-11-06 17:02:51 +03:00
<filename><replaceable>foo</replaceable>.efi.extra.d/*.addon.efi</filename> are loaded and verified as
PE binaries, and a <literal>.cmdline</literal> section is parsed from them. Addons are supposed to be
used to pass additional kernel command line parameters or Devicetree blobs, regardless of the kernel
image being booted, for example to allow platform vendors to ship platform-specific
configuration.</para>
<para>In case Secure Boot is enabled, these files will be validated using keys in UEFI DB, Shim's DB or
man/systemd-stub: fix typo
2024-04-18 17:43:25 +03:00
Shim's MOK, and will be rejected otherwise. Additionally, if both the addon and the UKI contain a
man/systemd-stub: split and simplify a wall'o'text paragraph
2023-11-06 17:02:51 +03:00
<literal>.uname</literal> section, the addon will be rejected if they do not match exactly. It is
stub: allow loading and verifying cmdline addons Files placed in /EFI/Linux/UKI.efi.extra.d/ and /loader/addons/ are opened and verified using the LoadImage protocol, and will thus get verified via shim/firmware. If they are valid signed PE files, the .cmdline section will be extracted and appended. If there are multiple addons in each directory, they will be parsed in alphanumerical order. Optionally the .uname sections are also matched if present, so that they can be used to filter out addons as well if needed, and only addons that correspond exactly to the UKI being loaded are used. It is recommended to also always add a .sbat section to addons, so that they can be mass-revoked with just a policy update. The files must have a .addon.efi suffix. Files in the per-UKI directory are parsed, sorted, measured and appended first. Then, files in the generic directory are processed.
2023-05-12 02:55:58 +03:00
recommended to always add a <literal>.sbat</literal> section to all signed addons, so that they may be
revoked with a SBAT policy update, without requiring blocklisting via DBX/MOKX. The
man/systemd-stub: split and simplify a wall'o'text paragraph
2023-11-06 17:02:51 +03:00
<citerefentry><refentrytitle>ukify</refentrytitle><manvolnum>1</manvolnum></citerefentry> tool will add
a SBAT policy by default if none is passed when building addons. For more information on SBAT see
<ulink url="https://github.com/rhboot/shim/blob/main/SBAT.md">Shim documentation</ulink>.</para>
<para>Addon files are sorted, loaded, and measured into TPM PCR 12 (if a TPM is present) and appended
to the kernel command line. UKI command line options are listed first, then options from addons in
<filename>/loader/addons/*.addon.efi</filename>, and finally UKI-specific addons. Device tree blobs are
loaded and measured following the same algorithm. Addons are always loaded in the same order based on
the filename, so that, given the same set of addons, the same set of measurements can be expected in
PCR12. However, note that the filename is not protected by the PE signature, and as such an attacker
with write access to the ESP could potentially rename these files to change the order in which they are
loaded, in a way that could alter the functionality of the kernel, as some options might be
order-dependent. If you sign such addons, you should pay attention to the PCR12 values and make use of
an attestation service so that improper use of your signed addons can be detected and dealt with using
one of the aforementioned revocation mechanisms.</para></listitem>
stub: allow loading and verifying cmdline addons Files placed in /EFI/Linux/UKI.efi.extra.d/ and /loader/addons/ are opened and verified using the LoadImage protocol, and will thus get verified via shim/firmware. If they are valid signed PE files, the .cmdline section will be extracted and appended. If there are multiple addons in each directory, they will be parsed in alphanumerical order. Optionally the .uname sections are also matched if present, so that they can be used to filter out addons as well if needed, and only addons that correspond exactly to the UKI being loaded are used. It is recommended to also always add a .sbat section to addons, so that they can be mass-revoked with just a policy update. The files must have a .addon.efi suffix. Files in the per-UKI directory are parsed, sorted, measured and appended first. Then, files in the generic directory are processed.
2023-05-12 02:55:58 +03:00
stub: Load credentials from \loader\credentials\*.cred Some types of credentials that a user would want to pass into the initrd do not depend on the specific kernel/initrd version. For instance, this can include SSH keys, rootfs encryption keys, dm-integrity keys, and so on. This introduces a directory where such credentials can be placed so that any kernel image will load them
2021-12-08 05:21:40 +03:00
<listitem><para>Files <filename>/loader/credentials/*.cred</filename> are packed up in a
<command>cpio</command> archive and placed in the <filename>/.extra/global_credentials/</filename>
directory of the initrd file hierarchy. This is supposed to be used to pass additional credentials to
the initrd, regardless of the kernel being booted. The generated <command>cpio</command> archive is
man: missing/misplaced periods
2023-06-19 14:35:45 +03:00
measured into TPM PCR 12 (if a TPM is present).</para></listitem>
stub: allow loading and verifying cmdline addons Files placed in /EFI/Linux/UKI.efi.extra.d/ and /loader/addons/ are opened and verified using the LoadImage protocol, and will thus get verified via shim/firmware. If they are valid signed PE files, the .cmdline section will be extracted and appended. If there are multiple addons in each directory, they will be parsed in alphanumerical order. Optionally the .uname sections are also matched if present, so that they can be used to filter out addons as well if needed, and only addons that correspond exactly to the UKI being loaded are used. It is recommended to also always add a .sbat section to addons, so that they can be mass-revoked with just a policy update. The files must have a .addon.efi suffix. Files in the per-UKI directory are parsed, sorted, measured and appended first. Then, files in the generic directory are processed.
2023-05-12 02:55:58 +03:00
<listitem><para>Additionally, files <filename>/loader/addons/*.addon.efi</filename> are loaded and
stub: add support for dtb addons Same as kernel command line addons.
2023-08-07 03:05:18 +03:00
verified as PE binaries, and <literal>.cmdline</literal> and/or <literal>.dtb</literal> sections are
parsed from them. This is supposed to be used to pass additional command line parameters or Devicetree
blobs to the kernel, regardless of the kernel being booted.</para></listitem>
man: add man page for the systemd UEFI stub Fixes: #17215
2021-09-21 17:52:24 +03:00
</itemizedlist>
stub: Load credentials from \loader\credentials\*.cred Some types of credentials that a user would want to pass into the initrd do not depend on the specific kernel/initrd version. For instance, this can include SSH keys, rootfs encryption keys, dm-integrity keys, and so on. This introduces a directory where such credentials can be placed so that any kernel image will load them
2021-12-08 05:21:40 +03:00
<para>These mechanisms may be used to parameterize and extend trusted (i.e. signed), immutable initrd
man: add man page for the systemd UEFI stub Fixes: #17215
2021-09-21 17:52:24 +03:00
images in a reasonably safe way: all data they contain is measured into TPM PCRs. On access they should be
further validated: in case of the credentials case by encrypting/authenticating them via TPM, as exposed
by <command>systemd-creds encrypt -T</command> (see
<citerefentry><refentrytitle>systemd-creds</refentrytitle><manvolnum>1</manvolnum></citerefentry> for
details); in case of the system extension images by using signed Verity images.</para>
</refsect1>
man: update TPM2 PCR documentation The assignments were partly simply incorrectly documented, partly changed with 4d32507f5186a89e98093659fbbe386787a97b9f and partly missing. Moreover kernel 5.17 now measures all initrds to PCR 9 on its own (https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=f046fff8bc4c4d8f8a478022e76e40b818f692df) Let's correct all this and bring it up-to-date. And while we are at it extend the docs about this in systemd-stub, with a new table that indicates which OS resource is protected by which PCR.
2022-04-14 15:38:52 +03:00
<refsect1>
man: be more careful regarding TPM vs. TPM2 We support PCR measurements for both classic TPM1.2 and TPM2, hence just say "TPM" generically in that context. But the signed policies are exclusive to TPM2, hence always say TPM2 there. We mostly got that right, except at one place. Fix that.
2022-09-09 12:09:30 +03:00
<title>TPM PCR Notes</title>
man: update TPM2 PCR documentation The assignments were partly simply incorrectly documented, partly changed with 4d32507f5186a89e98093659fbbe386787a97b9f and partly missing. Moreover kernel 5.17 now measures all initrds to PCR 9 on its own (https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=f046fff8bc4c4d8f8a478022e76e40b818f692df) Let's correct all this and bring it up-to-date. And while we are at it extend the docs about this in systemd-stub, with a new table that indicates which OS resource is protected by which PCR.
2022-04-14 15:38:52 +03:00
<para>Note that when a unified kernel using <command>systemd-stub</command> is invoked the firmware will
measure it as a whole to TPM PCR 4, covering all embedded resources, such as the stub code itself, the
core kernel, the embedded initrd and kernel command line (see above for a full list).</para>
<para>Also note that the Linux kernel will measure all initrds it receives into TPM PCR 9. This means
stub: Add support for .ucode UKI section This commit adds support for loading, measuring and handling a ".ucode" UKI section. This section is functionally an initrd, intended for microcode updates. As such it will always be passed to the kernel first.
2024-04-02 13:54:30 +03:00
every type of initrd will be measured two or three times: the initrds embedded in the kernel image will be
stub: pick up confexts from the ESP as well This does what we do for system extension also for configuration extension. This is complicated by the fact that we previously looked for <uki-binary>.d/*.raw for system extensions. We want to measure sysexts and confexts to different PCRs (13 vs. 12) hence we must distinguish them, but *.raw would match both kinds. This commit solves this via the following mechanism: we'll load confexts from *.confext.raw and sysexts from *.raw but will then enclude *.confext.raw from the latter. This preserves compatibility but allows us to somewhat reasonable distinguish both types of images. The documentation is updated not going into this detail though, and instead now claims that sysexts shall be *.sysext.raw and confexts *.confext.raw even though we actually are more lenient than this. This is simply to push people towards using the longer, more descriptive suffixes. I added an XML comment (<!-- … -->) about this to the docs, so that whenever somebody notices the difference between code and docs understands why and leaves it that way.
2023-11-08 21:02:03 +03:00
measured to PCR 4, PCR 9 and PCR 11; the initrd synthesized from credentials (and the one synthesized
from configuration extensions) will be measured to both PCR 9 and PCR 12; the initrd synthesized from
system extensions will be measured to both PCR 4 and PCR 9. Let's summarize the OS resources and the PCRs
they are measured to:</para>
man: update TPM2 PCR documentation The assignments were partly simply incorrectly documented, partly changed with 4d32507f5186a89e98093659fbbe386787a97b9f and partly missing. Moreover kernel 5.17 now measures all initrds to PCR 9 on its own (https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=f046fff8bc4c4d8f8a478022e76e40b818f692df) Let's correct all this and bring it up-to-date. And while we are at it extend the docs about this in systemd-stub, with a new table that indicates which OS resource is protected by which PCR.
2022-04-14 15:38:52 +03:00
<table>
<title>OS Resource PCR Summary</title>
<tgroup cols='2' align='left' colsep='1' rowsep='1'>
<colspec colname="pcr" />
<colspec colname="definition" />
<thead>
<row>
<entry>OS Resource</entry>
<entry>Measurement PCR</entry>
</row>
</thead>
<tbody>
<row>
<entry><command>systemd-stub</command> code (the entry point of the unified PE binary)</entry>
<entry>4</entry>
</row>
<row>
man: document the new .pcrsig/.pcrpkey sections for unified kernel images
2022-09-09 12:08:35 +03:00
<entry>Core kernel code (embedded in unified PE binary)</entry>
efi: from the stub measure the ELF kernel + built-in initrd and so on into PCR 11 Here we grab a new – on Linux so far unused (by my Googling skills, that is) – and measure all static components of the PE kernel image into. This is useful since for the first time we'll have a PCR that contains only a PCR of the booted kernel, nothing else. That allows putting together TPM policies that bind to a specific kernel (+ builtin initrd), without having to have booted that kernel first. PCRs can be pre-calculated. Yay! You might wonder, why we measure just the discovered PE sections we are about to use, instead of the whole PE image. That's because of the next step I have in mind: PE images should also be able to carry an additional section that contains a signature for its own expected, pre-calculated PCR values. This signature data should then be passed into the booted kernel and can be used there in TPM policies. Benefit: TPM policies can now be bound to *signatures* of PCRs, instead of the raw hash values themselves. This makes update management a *lot* easier, as policies don't need to be updated whenever a kernel is updated, as long as the signature is available. Now, if the PCR signature is embedded in the kernel PE image it cannot be of a PCR hash of the kernel PE image itself, because that would be a chicken-and-egg problem. Hence, by only measuring the relavent payload sections (and that means excluding the future section that will contain the PCR hash signature) we avoid this problem, naturally.
2022-07-25 18:44:24 +03:00
<entry>4 + 11</entry>
man: update TPM2 PCR documentation The assignments were partly simply incorrectly documented, partly changed with 4d32507f5186a89e98093659fbbe386787a97b9f and partly missing. Moreover kernel 5.17 now measures all initrds to PCR 9 on its own (https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=f046fff8bc4c4d8f8a478022e76e40b818f692df) Let's correct all this and bring it up-to-date. And while we are at it extend the docs about this in systemd-stub, with a new table that indicates which OS resource is protected by which PCR.
2022-04-14 15:38:52 +03:00
</row>
<row>
man: document the new .pcrsig/.pcrpkey sections for unified kernel images
2022-09-09 12:08:35 +03:00
<entry>OS release information (embedded in the unified PE binary)</entry>
efi: from the stub measure the ELF kernel + built-in initrd and so on into PCR 11 Here we grab a new – on Linux so far unused (by my Googling skills, that is) – and measure all static components of the PE kernel image into. This is useful since for the first time we'll have a PCR that contains only a PCR of the booted kernel, nothing else. That allows putting together TPM policies that bind to a specific kernel (+ builtin initrd), without having to have booted that kernel first. PCRs can be pre-calculated. Yay! You might wonder, why we measure just the discovered PE sections we are about to use, instead of the whole PE image. That's because of the next step I have in mind: PE images should also be able to carry an additional section that contains a signature for its own expected, pre-calculated PCR values. This signature data should then be passed into the booted kernel and can be used there in TPM policies. Benefit: TPM policies can now be bound to *signatures* of PCRs, instead of the raw hash values themselves. This makes update management a *lot* easier, as policies don't need to be updated whenever a kernel is updated, as long as the signature is available. Now, if the PCR signature is embedded in the kernel PE image it cannot be of a PCR hash of the kernel PE image itself, because that would be a chicken-and-egg problem. Hence, by only measuring the relavent payload sections (and that means excluding the future section that will contain the PCR hash signature) we avoid this problem, naturally.
2022-07-25 18:44:24 +03:00
<entry>4 + 11</entry>
man: update TPM2 PCR documentation The assignments were partly simply incorrectly documented, partly changed with 4d32507f5186a89e98093659fbbe386787a97b9f and partly missing. Moreover kernel 5.17 now measures all initrds to PCR 9 on its own (https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=f046fff8bc4c4d8f8a478022e76e40b818f692df) Let's correct all this and bring it up-to-date. And while we are at it extend the docs about this in systemd-stub, with a new table that indicates which OS resource is protected by which PCR.
2022-04-14 15:38:52 +03:00
</row>
<row>
<entry>Main initrd (embedded in unified PE binary)</entry>
efi: from the stub measure the ELF kernel + built-in initrd and so on into PCR 11 Here we grab a new – on Linux so far unused (by my Googling skills, that is) – and measure all static components of the PE kernel image into. This is useful since for the first time we'll have a PCR that contains only a PCR of the booted kernel, nothing else. That allows putting together TPM policies that bind to a specific kernel (+ builtin initrd), without having to have booted that kernel first. PCRs can be pre-calculated. Yay! You might wonder, why we measure just the discovered PE sections we are about to use, instead of the whole PE image. That's because of the next step I have in mind: PE images should also be able to carry an additional section that contains a signature for its own expected, pre-calculated PCR values. This signature data should then be passed into the booted kernel and can be used there in TPM policies. Benefit: TPM policies can now be bound to *signatures* of PCRs, instead of the raw hash values themselves. This makes update management a *lot* easier, as policies don't need to be updated whenever a kernel is updated, as long as the signature is available. Now, if the PCR signature is embedded in the kernel PE image it cannot be of a PCR hash of the kernel PE image itself, because that would be a chicken-and-egg problem. Hence, by only measuring the relavent payload sections (and that means excluding the future section that will contain the PCR hash signature) we avoid this problem, naturally.
2022-07-25 18:44:24 +03:00
<entry>4 + 9 + 11</entry>
man: update TPM2 PCR documentation The assignments were partly simply incorrectly documented, partly changed with 4d32507f5186a89e98093659fbbe386787a97b9f and partly missing. Moreover kernel 5.17 now measures all initrds to PCR 9 on its own (https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=f046fff8bc4c4d8f8a478022e76e40b818f692df) Let's correct all this and bring it up-to-date. And while we are at it extend the docs about this in systemd-stub, with a new table that indicates which OS resource is protected by which PCR.
2022-04-14 15:38:52 +03:00
</row>
stub: Add support for .ucode UKI section This commit adds support for loading, measuring and handling a ".ucode" UKI section. This section is functionally an initrd, intended for microcode updates. As such it will always be passed to the kernel first.
2024-04-02 13:54:30 +03:00
<row>
<entry>Microcode initrd (embedded in unified PE binary)</entry>
<entry>4 + 9 + 11</entry>
</row>
man: update TPM2 PCR documentation The assignments were partly simply incorrectly documented, partly changed with 4d32507f5186a89e98093659fbbe386787a97b9f and partly missing. Moreover kernel 5.17 now measures all initrds to PCR 9 on its own (https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=f046fff8bc4c4d8f8a478022e76e40b818f692df) Let's correct all this and bring it up-to-date. And while we are at it extend the docs about this in systemd-stub, with a new table that indicates which OS resource is protected by which PCR.
2022-04-14 15:38:52 +03:00
<row>
<entry>Default kernel command line (embedded in unified PE binary)</entry>
efi: from the stub measure the ELF kernel + built-in initrd and so on into PCR 11 Here we grab a new – on Linux so far unused (by my Googling skills, that is) – and measure all static components of the PE kernel image into. This is useful since for the first time we'll have a PCR that contains only a PCR of the booted kernel, nothing else. That allows putting together TPM policies that bind to a specific kernel (+ builtin initrd), without having to have booted that kernel first. PCRs can be pre-calculated. Yay! You might wonder, why we measure just the discovered PE sections we are about to use, instead of the whole PE image. That's because of the next step I have in mind: PE images should also be able to carry an additional section that contains a signature for its own expected, pre-calculated PCR values. This signature data should then be passed into the booted kernel and can be used there in TPM policies. Benefit: TPM policies can now be bound to *signatures* of PCRs, instead of the raw hash values themselves. This makes update management a *lot* easier, as policies don't need to be updated whenever a kernel is updated, as long as the signature is available. Now, if the PCR signature is embedded in the kernel PE image it cannot be of a PCR hash of the kernel PE image itself, because that would be a chicken-and-egg problem. Hence, by only measuring the relavent payload sections (and that means excluding the future section that will contain the PCR hash signature) we avoid this problem, naturally.
2022-07-25 18:44:24 +03:00
<entry>4 + 11</entry>
man: update TPM2 PCR documentation The assignments were partly simply incorrectly documented, partly changed with 4d32507f5186a89e98093659fbbe386787a97b9f and partly missing. Moreover kernel 5.17 now measures all initrds to PCR 9 on its own (https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=f046fff8bc4c4d8f8a478022e76e40b818f692df) Let's correct all this and bring it up-to-date. And while we are at it extend the docs about this in systemd-stub, with a new table that indicates which OS resource is protected by which PCR.
2022-04-14 15:38:52 +03:00
</row>
<row>
tree-wide: Fix typo
2022-04-25 04:06:08 +03:00
<entry>Overridden kernel command line</entry>
man: update TPM2 PCR documentation The assignments were partly simply incorrectly documented, partly changed with 4d32507f5186a89e98093659fbbe386787a97b9f and partly missing. Moreover kernel 5.17 now measures all initrds to PCR 9 on its own (https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=f046fff8bc4c4d8f8a478022e76e40b818f692df) Let's correct all this and bring it up-to-date. And while we are at it extend the docs about this in systemd-stub, with a new table that indicates which OS resource is protected by which PCR.
2022-04-14 15:38:52 +03:00
<entry>12</entry>
</row>
man: document the new .pcrsig/.pcrpkey sections for unified kernel images
2022-09-09 12:08:35 +03:00
<row>
<entry>Boot splash (embedded in the unified PE binary)</entry>
<entry>4 + 11</entry>
</row>
<row>
<entry>TPM2 PCR signature JSON (embedded in unified PE binary, synthesized into initrd)</entry>
<entry>4 + 9</entry>
</row>
<row>
<entry>TPM2 PCR PEM public key (embedded in unified PE binary, synthesized into initrd)</entry>
<entry>4 + 9 + 11</entry>
</row>
man: update TPM2 PCR documentation The assignments were partly simply incorrectly documented, partly changed with 4d32507f5186a89e98093659fbbe386787a97b9f and partly missing. Moreover kernel 5.17 now measures all initrds to PCR 9 on its own (https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=f046fff8bc4c4d8f8a478022e76e40b818f692df) Let's correct all this and bring it up-to-date. And while we are at it extend the docs about this in systemd-stub, with a new table that indicates which OS resource is protected by which PCR.
2022-04-14 15:38:52 +03:00
<row>
<entry>Credentials (synthesized initrd from companion files)</entry>
efi: tell userspace where the stub measured the kernel command line/credentials into This is useful for userspace to know, so that policies can be put together safely, matching what the stub actually measured.
2022-07-26 19:32:21 +03:00
<entry>9 + 12</entry>
man: update TPM2 PCR documentation The assignments were partly simply incorrectly documented, partly changed with 4d32507f5186a89e98093659fbbe386787a97b9f and partly missing. Moreover kernel 5.17 now measures all initrds to PCR 9 on its own (https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=f046fff8bc4c4d8f8a478022e76e40b818f692df) Let's correct all this and bring it up-to-date. And while we are at it extend the docs about this in systemd-stub, with a new table that indicates which OS resource is protected by which PCR.
2022-04-14 15:38:52 +03:00
</row>
<row>
<entry>System Extensions (synthesized initrd from companion files)</entry>
sd-stub: measure sysext images picked up by sd-stub into PCR 13 Let's grab another so far unused PCR, and measure all sysext images into it that we load from the ESP. Note that this is possibly partly redundant, since sysext images should have dm-verity enabled, and that is hooked up to IMA. However, measuring this explicitly has the benefit that we can measure filenames too, easily, and that all without need for IMA or anything like that. This means: when booting a unified sd-stub kernel through sd-boot we'll now have: 1. PCR 11: unified kernel image payload (i.e. kernel, initrd, boot splash, dtb, osrelease) 2. PCR 12: kernel command line (i.e. the one embedded in the image, plus optionally an overriden one) + any credential files picked up by sd-stub 3. PCR 13: sysext images picked up by sd-stub And each of these three PCRs should carry just the above, and start from zero, thus be pre-calculatable. Thus, all components and parameters of the OS boot process (i.e. everything after the boot loader) is now nicely pre-calculable. NOTE: this actually replaces previous measuring of the syext images into PCR 4. I added this back in 845707aae23b3129db635604edb95c4048a5922a, following the train of thought, that sysext images for the initrd should be measured like the initrd itself they are for, and according to my thinking that would be a unified kernel which is measured by firmware into PCR 4 like any other UEFI executables. However, I think we should depart from that idea. First and foremost that makes it harder to pre-calculate PCR 4 (since we actually measured quite incompatible records to the TPM event log), but also I think there's great value in being able to write policies that bind to the used sysexts independently of the earlier boot chain (i.e. shim, boot loader, unified kernel), hence a separate PCR makes more sense. Strictly speaking, this is a compatibility break, but I think one we can get away with, simply because the initrd sysext images are currently not picked up by systemd-sysext yet in the initrd, and because of that we can be reasonably sure noone uses this yet, and hence relies on the PCR register used. Hence, let's clean this up before people actually do start relying on this.
2022-07-26 12:35:57 +03:00
<entry>9 + 13</entry>
man: update TPM2 PCR documentation The assignments were partly simply incorrectly documented, partly changed with 4d32507f5186a89e98093659fbbe386787a97b9f and partly missing. Moreover kernel 5.17 now measures all initrds to PCR 9 on its own (https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=f046fff8bc4c4d8f8a478022e76e40b818f692df) Let's correct all this and bring it up-to-date. And while we are at it extend the docs about this in systemd-stub, with a new table that indicates which OS resource is protected by which PCR.
2022-04-14 15:38:52 +03:00
</row>
stub: pick up confexts from the ESP as well This does what we do for system extension also for configuration extension. This is complicated by the fact that we previously looked for <uki-binary>.d/*.raw for system extensions. We want to measure sysexts and confexts to different PCRs (13 vs. 12) hence we must distinguish them, but *.raw would match both kinds. This commit solves this via the following mechanism: we'll load confexts from *.confext.raw and sysexts from *.raw but will then enclude *.confext.raw from the latter. This preserves compatibility but allows us to somewhat reasonable distinguish both types of images. The documentation is updated not going into this detail though, and instead now claims that sysexts shall be *.sysext.raw and confexts *.confext.raw even though we actually are more lenient than this. This is simply to push people towards using the longer, more descriptive suffixes. I added an XML comment (<!-- … -->) about this to the docs, so that whenever somebody notices the difference between code and docs understands why and leaves it that way.
2023-11-08 21:02:03 +03:00
<row>
<entry>Configuration Extensions (synthesized initrd from companion files)</entry>
<entry>9 + 12</entry>
</row>
man: update TPM2 PCR documentation The assignments were partly simply incorrectly documented, partly changed with 4d32507f5186a89e98093659fbbe386787a97b9f and partly missing. Moreover kernel 5.17 now measures all initrds to PCR 9 on its own (https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=f046fff8bc4c4d8f8a478022e76e40b818f692df) Let's correct all this and bring it up-to-date. And while we are at it extend the docs about this in systemd-stub, with a new table that indicates which OS resource is protected by which PCR.
2022-04-14 15:38:52 +03:00
</tbody>
</tgroup>
</table>
</refsect1>
man: add man page for the systemd UEFI stub Fixes: #17215
2021-09-21 17:52:24 +03:00
<refsect1>
<title>EFI Variables</title>
<para>The following EFI variables are defined, set and read by <command>systemd-stub</command>, under the
vendor UUID <literal>4a67b082-0a4c-41cf-b6c7-440b29bb8c4f</literal>, for communication between the boot
stub and the OS:</para>
<variablelist class='efi-variables'>
<varlistentry>
<term><varname>LoaderDevicePartUUID</varname></term>
<listitem><para>Contains the partition UUID of the EFI System Partition the EFI image was run
from. <citerefentry><refentrytitle>systemd-gpt-auto-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>
uses this information to automatically find the disk booted from, in order to discover various other
man: add version info This tries to add information about when each option was added. It goes back to version 183. The version info is included from a separate file to allow generating it, which would allow more control on the formatting of the final output.
2023-08-22 19:52:36 +03:00
partitions on the same disk automatically.</para>
<xi:include href="version-info.xml" xpointer="v250"/></listitem>
man: add man page for the systemd UEFI stub Fixes: #17215
2021-09-21 17:52:24 +03:00
</varlistentry>
<varlistentry>
<term><varname>LoaderFirmwareInfo</varname></term>
<term><varname>LoaderFirmwareType</varname></term>
<listitem><para>Brief firmware information. Use
<citerefentry><refentrytitle>bootctl</refentrytitle><manvolnum>1</manvolnum></citerefentry> to view this
man: add version info This tries to add information about when each option was added. It goes back to version 183. The version info is included from a separate file to allow generating it, which would allow more control on the formatting of the final output.
2023-08-22 19:52:36 +03:00
data.</para>
<xi:include href="version-info.xml" xpointer="v250"/></listitem>
man: add man page for the systemd UEFI stub Fixes: #17215
2021-09-21 17:52:24 +03:00
</varlistentry>
<varlistentry>
<term><varname>LoaderImageIdentifier</varname></term>
<listitem><para>The path of EFI executable, relative to the EFI System Partition's root
directory. Use
<citerefentry><refentrytitle>bootctl</refentrytitle><manvolnum>1</manvolnum></citerefentry> to view
man: add version info This tries to add information about when each option was added. It goes back to version 183. The version info is included from a separate file to allow generating it, which would allow more control on the formatting of the final output.
2023-08-22 19:52:36 +03:00
this data.</para>
<xi:include href="version-info.xml" xpointer="v250"/></listitem>
man: add man page for the systemd UEFI stub Fixes: #17215
2021-09-21 17:52:24 +03:00
</varlistentry>
<varlistentry>
<term><varname>StubInfo</varname></term>
<listitem><para>Brief stub information. Use
<citerefentry><refentrytitle>bootctl</refentrytitle><manvolnum>1</manvolnum></citerefentry> to view
man: add version info This tries to add information about when each option was added. It goes back to version 183. The version info is included from a separate file to allow generating it, which would allow more control on the formatting of the final output.
2023-08-22 19:52:36 +03:00
this data.</para>
<xi:include href="version-info.xml" xpointer="v250"/></listitem>
man: add man page for the systemd UEFI stub Fixes: #17215
2021-09-21 17:52:24 +03:00
</varlistentry>
efi: tell userspace where the stub measured the kernel command line/credentials into This is useful for userspace to know, so that policies can be put together safely, matching what the stub actually measured.
2022-07-26 19:32:21 +03:00
efi: from the stub measure the ELF kernel + built-in initrd and so on into PCR 11 Here we grab a new – on Linux so far unused (by my Googling skills, that is) – and measure all static components of the PE kernel image into. This is useful since for the first time we'll have a PCR that contains only a PCR of the booted kernel, nothing else. That allows putting together TPM policies that bind to a specific kernel (+ builtin initrd), without having to have booted that kernel first. PCRs can be pre-calculated. Yay! You might wonder, why we measure just the discovered PE sections we are about to use, instead of the whole PE image. That's because of the next step I have in mind: PE images should also be able to carry an additional section that contains a signature for its own expected, pre-calculated PCR values. This signature data should then be passed into the booted kernel and can be used there in TPM policies. Benefit: TPM policies can now be bound to *signatures* of PCRs, instead of the raw hash values themselves. This makes update management a *lot* easier, as policies don't need to be updated whenever a kernel is updated, as long as the signature is available. Now, if the PCR signature is embedded in the kernel PE image it cannot be of a PCR hash of the kernel PE image itself, because that would be a chicken-and-egg problem. Hence, by only measuring the relavent payload sections (and that means excluding the future section that will contain the PCR hash signature) we avoid this problem, naturally.
2022-07-25 18:44:24 +03:00
<varlistentry>
<term><varname>StubPcrKernelImage</varname></term>
man: "the initial RAM disk" → "the initrd" In many places we spelled out the phrase behind "initrd" in full, but this isn't terribly useful. In fact, no "RAM disk" is used, so emphasizing this is just confusing to the reader. Let's just say "initrd" everywhere, people understand what this refers to, and that it's in fact an initramfs image. Also, s/i.e./e.g./ where appropriate. Also, don't say "in RAM", when in fact it's virtual memory, whose pages may or may not be loaded in page frames in RAM, and we have no control over this. Also, add <filename></filename> and other minor cleanups.
2022-09-15 15:43:59 +03:00
<listitem><para>The PCR register index the kernel image, initrd image, boot splash, devicetree
database, and the embedded command line are measured into, formatted as decimal ASCII string (e.g.
<literal>11</literal>). This variable is set if a measurement was successfully completed, and remains
man: add version info This tries to add information about when each option was added. It goes back to version 183. The version info is included from a separate file to allow generating it, which would allow more control on the formatting of the final output.
2023-08-22 19:52:36 +03:00
unset otherwise.</para>
<xi:include href="version-info.xml" xpointer="v252"/></listitem>
efi: from the stub measure the ELF kernel + built-in initrd and so on into PCR 11 Here we grab a new – on Linux so far unused (by my Googling skills, that is) – and measure all static components of the PE kernel image into. This is useful since for the first time we'll have a PCR that contains only a PCR of the booted kernel, nothing else. That allows putting together TPM policies that bind to a specific kernel (+ builtin initrd), without having to have booted that kernel first. PCRs can be pre-calculated. Yay! You might wonder, why we measure just the discovered PE sections we are about to use, instead of the whole PE image. That's because of the next step I have in mind: PE images should also be able to carry an additional section that contains a signature for its own expected, pre-calculated PCR values. This signature data should then be passed into the booted kernel and can be used there in TPM policies. Benefit: TPM policies can now be bound to *signatures* of PCRs, instead of the raw hash values themselves. This makes update management a *lot* easier, as policies don't need to be updated whenever a kernel is updated, as long as the signature is available. Now, if the PCR signature is embedded in the kernel PE image it cannot be of a PCR hash of the kernel PE image itself, because that would be a chicken-and-egg problem. Hence, by only measuring the relavent payload sections (and that means excluding the future section that will contain the PCR hash signature) we avoid this problem, naturally.
2022-07-25 18:44:24 +03:00
</varlistentry>
efi: tell userspace where the stub measured the kernel command line/credentials into This is useful for userspace to know, so that policies can be put together safely, matching what the stub actually measured.
2022-07-26 19:32:21 +03:00
<varlistentry>
<term><varname>StubPcrKernelParameters</varname></term>
<listitem><para>The PCR register index the kernel command line and credentials are measured into,
man: "the initial RAM disk" → "the initrd" In many places we spelled out the phrase behind "initrd" in full, but this isn't terribly useful. In fact, no "RAM disk" is used, so emphasizing this is just confusing to the reader. Let's just say "initrd" everywhere, people understand what this refers to, and that it's in fact an initramfs image. Also, s/i.e./e.g./ where appropriate. Also, don't say "in RAM", when in fact it's virtual memory, whose pages may or may not be loaded in page frames in RAM, and we have no control over this. Also, add <filename></filename> and other minor cleanups.
2022-09-15 15:43:59 +03:00
formatted as decimal ASCII string (e.g. <literal>12</literal>). This variable is set if a measurement
man: add version info This tries to add information about when each option was added. It goes back to version 183. The version info is included from a separate file to allow generating it, which would allow more control on the formatting of the final output.
2023-08-22 19:52:36 +03:00
was successfully completed, and remains unset otherwise.</para>
<xi:include href="version-info.xml" xpointer="v252"/></listitem>
efi: tell userspace where the stub measured the kernel command line/credentials into This is useful for userspace to know, so that policies can be put together safely, matching what the stub actually measured.
2022-07-26 19:32:21 +03:00
</varlistentry>
sd-stub: measure sysext images picked up by sd-stub into PCR 13 Let's grab another so far unused PCR, and measure all sysext images into it that we load from the ESP. Note that this is possibly partly redundant, since sysext images should have dm-verity enabled, and that is hooked up to IMA. However, measuring this explicitly has the benefit that we can measure filenames too, easily, and that all without need for IMA or anything like that. This means: when booting a unified sd-stub kernel through sd-boot we'll now have: 1. PCR 11: unified kernel image payload (i.e. kernel, initrd, boot splash, dtb, osrelease) 2. PCR 12: kernel command line (i.e. the one embedded in the image, plus optionally an overriden one) + any credential files picked up by sd-stub 3. PCR 13: sysext images picked up by sd-stub And each of these three PCRs should carry just the above, and start from zero, thus be pre-calculatable. Thus, all components and parameters of the OS boot process (i.e. everything after the boot loader) is now nicely pre-calculable. NOTE: this actually replaces previous measuring of the syext images into PCR 4. I added this back in 845707aae23b3129db635604edb95c4048a5922a, following the train of thought, that sysext images for the initrd should be measured like the initrd itself they are for, and according to my thinking that would be a unified kernel which is measured by firmware into PCR 4 like any other UEFI executables. However, I think we should depart from that idea. First and foremost that makes it harder to pre-calculate PCR 4 (since we actually measured quite incompatible records to the TPM event log), but also I think there's great value in being able to write policies that bind to the used sysexts independently of the earlier boot chain (i.e. shim, boot loader, unified kernel), hence a separate PCR makes more sense. Strictly speaking, this is a compatibility break, but I think one we can get away with, simply because the initrd sysext images are currently not picked up by systemd-sysext yet in the initrd, and because of that we can be reasonably sure noone uses this yet, and hence relies on the PCR register used. Hence, let's clean this up before people actually do start relying on this.
2022-07-26 12:35:57 +03:00
<varlistentry>
<term><varname>StubPcrInitRDSysExts</varname></term>
stub: pick up confexts from the ESP as well This does what we do for system extension also for configuration extension. This is complicated by the fact that we previously looked for <uki-binary>.d/*.raw for system extensions. We want to measure sysexts and confexts to different PCRs (13 vs. 12) hence we must distinguish them, but *.raw would match both kinds. This commit solves this via the following mechanism: we'll load confexts from *.confext.raw and sysexts from *.raw but will then enclude *.confext.raw from the latter. This preserves compatibility but allows us to somewhat reasonable distinguish both types of images. The documentation is updated not going into this detail though, and instead now claims that sysexts shall be *.sysext.raw and confexts *.confext.raw even though we actually are more lenient than this. This is simply to push people towards using the longer, more descriptive suffixes. I added an XML comment (<!-- … -->) about this to the docs, so that whenever somebody notices the difference between code and docs understands why and leaves it that way.
2023-11-08 21:02:03 +03:00
<listitem><para>The PCR register index the system extensions for the initrd, which are picked up from
the file system the kernel image is located on. Formatted as decimal ASCII string (e.g.
man: "the initial RAM disk" → "the initrd" In many places we spelled out the phrase behind "initrd" in full, but this isn't terribly useful. In fact, no "RAM disk" is used, so emphasizing this is just confusing to the reader. Let's just say "initrd" everywhere, people understand what this refers to, and that it's in fact an initramfs image. Also, s/i.e./e.g./ where appropriate. Also, don't say "in RAM", when in fact it's virtual memory, whose pages may or may not be loaded in page frames in RAM, and we have no control over this. Also, add <filename></filename> and other minor cleanups.
2022-09-15 15:43:59 +03:00
<literal>13</literal>). This variable is set if a measurement was successfully completed, and remains
man: add version info This tries to add information about when each option was added. It goes back to version 183. The version info is included from a separate file to allow generating it, which would allow more control on the formatting of the final output.
2023-08-22 19:52:36 +03:00
unset otherwise.</para>
<xi:include href="version-info.xml" xpointer="v252"/></listitem>
sd-stub: measure sysext images picked up by sd-stub into PCR 13 Let's grab another so far unused PCR, and measure all sysext images into it that we load from the ESP. Note that this is possibly partly redundant, since sysext images should have dm-verity enabled, and that is hooked up to IMA. However, measuring this explicitly has the benefit that we can measure filenames too, easily, and that all without need for IMA or anything like that. This means: when booting a unified sd-stub kernel through sd-boot we'll now have: 1. PCR 11: unified kernel image payload (i.e. kernel, initrd, boot splash, dtb, osrelease) 2. PCR 12: kernel command line (i.e. the one embedded in the image, plus optionally an overriden one) + any credential files picked up by sd-stub 3. PCR 13: sysext images picked up by sd-stub And each of these three PCRs should carry just the above, and start from zero, thus be pre-calculatable. Thus, all components and parameters of the OS boot process (i.e. everything after the boot loader) is now nicely pre-calculable. NOTE: this actually replaces previous measuring of the syext images into PCR 4. I added this back in 845707aae23b3129db635604edb95c4048a5922a, following the train of thought, that sysext images for the initrd should be measured like the initrd itself they are for, and according to my thinking that would be a unified kernel which is measured by firmware into PCR 4 like any other UEFI executables. However, I think we should depart from that idea. First and foremost that makes it harder to pre-calculate PCR 4 (since we actually measured quite incompatible records to the TPM event log), but also I think there's great value in being able to write policies that bind to the used sysexts independently of the earlier boot chain (i.e. shim, boot loader, unified kernel), hence a separate PCR makes more sense. Strictly speaking, this is a compatibility break, but I think one we can get away with, simply because the initrd sysext images are currently not picked up by systemd-sysext yet in the initrd, and because of that we can be reasonably sure noone uses this yet, and hence relies on the PCR register used. Hence, let's clean this up before people actually do start relying on this.
2022-07-26 12:35:57 +03:00
</varlistentry>
stub: pick up confexts from the ESP as well This does what we do for system extension also for configuration extension. This is complicated by the fact that we previously looked for <uki-binary>.d/*.raw for system extensions. We want to measure sysexts and confexts to different PCRs (13 vs. 12) hence we must distinguish them, but *.raw would match both kinds. This commit solves this via the following mechanism: we'll load confexts from *.confext.raw and sysexts from *.raw but will then enclude *.confext.raw from the latter. This preserves compatibility but allows us to somewhat reasonable distinguish both types of images. The documentation is updated not going into this detail though, and instead now claims that sysexts shall be *.sysext.raw and confexts *.confext.raw even though we actually are more lenient than this. This is simply to push people towards using the longer, more descriptive suffixes. I added an XML comment (<!-- … -->) about this to the docs, so that whenever somebody notices the difference between code and docs understands why and leaves it that way.
2023-11-08 21:02:03 +03:00
<varlistentry>
<term><varname>StubPcrInitRDConfExts</varname></term>
<listitem><para>The PCR register index the configuration extensions for the initrd, which are picked
up from the file system the kernel image is located on. Formatted as decimal ASCII string (e.g.
<literal>12</literal>). This variable is set if a measurement was successfully completed, and remains
unset otherwise.</para>
<xi:include href="version-info.xml" xpointer="v255"/></listitem>
</varlistentry>
man: add man page for the systemd UEFI stub Fixes: #17215
2021-09-21 17:52:24 +03:00
</variablelist>
<para>Note that some of the variables above may also be set by the boot loader. The stub will only set
them if they aren't set already. Some of these variables are defined by the <ulink
url="https://systemd.io/BOOT_LOADER_INTERFACE">Boot Loader Interface</ulink>.</para>
</refsect1>
man: document the new .pcrsig/.pcrpkey sections for unified kernel images
2022-09-09 12:08:35 +03:00
<refsect1>
<title>initrd Resources</title>
<para>The following resources are passed as initrd cpio archives to the booted kernel, and thus make up
the initial file system hierarchy in the initrd execution environment:</para>
<variablelist>
<varlistentry>
<term><filename>/</filename></term>
man: reword the list of PE sections in systemd-stub Let's put the section name at the beginning of each sentence. This way we can avoid awkward constructs like "kernel is looked for in the .linux section". Also, since the paragraph above says that this is a list of "PE sections", we can just say "section". In other places, it is often useful to say "PE section" to avoid ambiguity. Also fix the off-by-one in the count of sections.
2023-11-24 17:19:50 +03:00
<listitem><para>The main initrd from the <literal>.initrd</literal> PE section of the unified kernel
image.</para>
man: add version info This tries to add information about when each option was added. It goes back to version 183. The version info is included from a separate file to allow generating it, which would allow more control on the formatting of the final output.
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<xi:include href="version-info.xml" xpointer="v252"/></listitem>
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</varlistentry>
<varlistentry>
<term><filename>/.extra/credentials/*.cred</filename></term>
<listitem><para>Credential files (suffix <literal>.cred</literal>) that are placed next to the
unified kernel image (as described above) are copied into the
<filename>/.extra/credentials/</filename> directory in the initrd execution
man: add version info This tries to add information about when each option was added. It goes back to version 183. The version info is included from a separate file to allow generating it, which would allow more control on the formatting of the final output.
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environment.</para>
<xi:include href="version-info.xml" xpointer="v252"/></listitem>
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</varlistentry>
<varlistentry>
<term><filename>/.extra/global_credentials/*.cred</filename></term>
man: reword the list of PE sections in systemd-stub Let's put the section name at the beginning of each sentence. This way we can avoid awkward constructs like "kernel is looked for in the .linux section". Also, since the paragraph above says that this is a list of "PE sections", we can just say "section". In other places, it is often useful to say "PE section" to avoid ambiguity. Also fix the off-by-one in the count of sections.
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<listitem><para>Similarly, credential files in the <filename>/loader/credentials/</filename>
directory in the file system the unified kernel image is placed in are copied into the
man: document the new .pcrsig/.pcrpkey sections for unified kernel images
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<filename>/.extra/global_credentials/</filename> directory in the initrd execution
man: add version info This tries to add information about when each option was added. It goes back to version 183. The version info is included from a separate file to allow generating it, which would allow more control on the formatting of the final output.
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environment.</para>
<xi:include href="version-info.xml" xpointer="v252"/></listitem>
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</varlistentry>
<varlistentry>
stub: pick up confexts from the ESP as well This does what we do for system extension also for configuration extension. This is complicated by the fact that we previously looked for <uki-binary>.d/*.raw for system extensions. We want to measure sysexts and confexts to different PCRs (13 vs. 12) hence we must distinguish them, but *.raw would match both kinds. This commit solves this via the following mechanism: we'll load confexts from *.confext.raw and sysexts from *.raw but will then enclude *.confext.raw from the latter. This preserves compatibility but allows us to somewhat reasonable distinguish both types of images. The documentation is updated not going into this detail though, and instead now claims that sysexts shall be *.sysext.raw and confexts *.confext.raw even though we actually are more lenient than this. This is simply to push people towards using the longer, more descriptive suffixes. I added an XML comment (<!-- … -->) about this to the docs, so that whenever somebody notices the difference between code and docs understands why and leaves it that way.
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<term><filename>/.extra/sysext/*.sysext.raw</filename></term>
<listitem><para>System extension image files (suffix <literal>.sysext.raw</literal>) that are placed
next to the unified kernel image (as described above) are copied into the
man: add version info This tries to add information about when each option was added. It goes back to version 183. The version info is included from a separate file to allow generating it, which would allow more control on the formatting of the final output.
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<filename>/.extra/sysext/</filename> directory in the initrd execution environment.</para>
<xi:include href="version-info.xml" xpointer="v252"/></listitem>
man: document the new .pcrsig/.pcrpkey sections for unified kernel images
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</varlistentry>
stub: pick up confexts from the ESP as well This does what we do for system extension also for configuration extension. This is complicated by the fact that we previously looked for <uki-binary>.d/*.raw for system extensions. We want to measure sysexts and confexts to different PCRs (13 vs. 12) hence we must distinguish them, but *.raw would match both kinds. This commit solves this via the following mechanism: we'll load confexts from *.confext.raw and sysexts from *.raw but will then enclude *.confext.raw from the latter. This preserves compatibility but allows us to somewhat reasonable distinguish both types of images. The documentation is updated not going into this detail though, and instead now claims that sysexts shall be *.sysext.raw and confexts *.confext.raw even though we actually are more lenient than this. This is simply to push people towards using the longer, more descriptive suffixes. I added an XML comment (<!-- … -->) about this to the docs, so that whenever somebody notices the difference between code and docs understands why and leaves it that way.
2023-11-08 21:02:03 +03:00
<varlistentry>
<term><filename>/.extra/confext/*.confext.raw</filename></term>
<listitem><para>Configuration extension image files (suffix <literal>.confext.raw</literal>) that are
placed next to the unified kernel image (as described above) are copied into the
<filename>/.extra/confext/</filename> directory in the initrd execution environment.</para>
<xi:include href="version-info.xml" xpointer="v255"/></listitem>
</varlistentry>
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<varlistentry>
<term><filename>/.extra/tpm2-pcr-signature.json</filename></term>
<listitem><para>The TPM2 PCR signature JSON object included in the <literal>.pcrsig</literal> PE
section of the unified kernel image is copied into the
man: reword the list of PE sections in systemd-stub Let's put the section name at the beginning of each sentence. This way we can avoid awkward constructs like "kernel is looked for in the .linux section". Also, since the paragraph above says that this is a list of "PE sections", we can just say "section". In other places, it is often useful to say "PE section" to avoid ambiguity. Also fix the off-by-one in the count of sections.
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<filename>/.extra/tpm2-pcr-signature.json</filename> file in the initrd execution environment.</para>
man: add version info This tries to add information about when each option was added. It goes back to version 183. The version info is included from a separate file to allow generating it, which would allow more control on the formatting of the final output.
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<xi:include href="version-info.xml" xpointer="v252"/></listitem>
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</varlistentry>
<varlistentry>
<term><filename>/.extra/tpm2-pcr-pkey.pem</filename></term>
<listitem><para>The PEM public key included in the <literal>.pcrpkey</literal> PE section of the
unified kernel image is copied into the <filename>/.extra/tpm2-pcr-public-key.pem</filename> file in
man: add version info This tries to add information about when each option was added. It goes back to version 183. The version info is included from a separate file to allow generating it, which would allow more control on the formatting of the final output.
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the initrd execution environment.</para>
<xi:include href="version-info.xml" xpointer="v252"/></listitem>
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</varlistentry>
</variablelist>
<para>Note that all these files are located in the <literal>tmpfs</literal> file system the kernel sets
up for the initrd file hierarchy and are thus lost when the system transitions from the initrd execution
environment into the host file system. If these resources shall be kept around over this transition they
need to be copied to a place that survives the transition first, for example via a suitable
<citerefentry><refentrytitle>tmpfiles.d</refentrytitle><manvolnum>5</manvolnum></citerefentry> line. By
default, this is done for the TPM2 PCR signature and public key files.</para>
</refsect1>
stub: Read extra kernel command line items from SMBIOS Let's read more kernel command line arguments from SMBIOS OEM string io.systemd.stub.kernel-cmdline-extra. This allows adding debug kernel command line arguments when booting in qemy without having to modify the UKI.
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<refsect1>
<title>SMBIOS Type 11 Strings</title>
<para><command>systemd-stub</command> can be configured using SMBIOS Type 11 strings. Applicable strings
man: Mention that SMBIOS type 11 strings are ignored inside CVM
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consist of a name, followed by <literal>=</literal>, followed by the value. Unless
<command>systemd-stub</command> detects it is running inside a confidential computing environment,
stub: Read extra kernel command line items from SMBIOS Let's read more kernel command line arguments from SMBIOS OEM string io.systemd.stub.kernel-cmdline-extra. This allows adding debug kernel command line arguments when booting in qemy without having to modify the UKI.
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<command>systemd-stub</command> will search the table for a string with a specific name, and if found,
use its value. The following strings are read:</para>
<variablelist>
<varlistentry>
<term><varname>io.systemd.stub.kernel-cmdline-extra</varname></term>
<listitem><para>If set, the value of this string is added to the list of kernel command line
man: add version info This tries to add information about when each option was added. It goes back to version 183. The version info is included from a separate file to allow generating it, which would allow more control on the formatting of the final output.
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arguments that are measured in PCR12 and passed to the kernel.</para>
<xi:include href="version-info.xml" xpointer="v254"/></listitem>
stub: Read extra kernel command line items from SMBIOS Let's read more kernel command line arguments from SMBIOS OEM string io.systemd.stub.kernel-cmdline-extra. This allows adding debug kernel command line arguments when booting in qemy without having to modify the UKI.
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</varlistentry>
</variablelist>
</refsect1>
man: add man page for the systemd UEFI stub Fixes: #17215
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<refsect1>
<title>Assembling Kernel Images</title>
man: Use ukify instead of objcopy in examples These hardcoded VMA section offsets are a terrible thing and should vanish from earth.
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<para>In order to assemble a bootable Unified Kernel Image from various components as described above, use
<citerefentry><refentrytitle>ukify</refentrytitle><manvolnum>1</manvolnum></citerefentry>.</para>
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</refsect1>
<refsect1>
<title>See Also</title>
man: use <simplelist> for 'See also' sections This is just a slight markup improvement; there should be no difference in rendering.
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<para><simplelist type="inline">
<member><citerefentry><refentrytitle>systemd-boot</refentrytitle><manvolnum>7</manvolnum></citerefentry></member>
<member><citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry></member>
<member><citerefentry><refentrytitle>systemd-creds</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
<member><citerefentry><refentrytitle>systemd-sysext</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
<member><ulink url="https://uapi-group.org/specifications/specs/boot_loader_specification">Boot Loader Specification</ulink></member>
<member><ulink url="https://systemd.io/BOOT_LOADER_INTERFACE">Boot Loader Interface</ulink></member>
<member><citerefentry><refentrytitle>ukify</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
<member><citerefentry><refentrytitle>systemd-measure</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
<member><ulink url="https://systemd.io/TPM2_PCR_MEASUREMENTS">TPM2 PCR Measurements Made by systemd</ulink></member>
</simplelist></para>
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</refsect1>
</refentry>
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