man/systemd-measure.xml - systemd - Git at Google

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 <!--*-nxml-*-->
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   "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
 <!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
 <refentry id="systemd-measure" xmlns:xi="http://www.w3.org/2001/XInclude" conditional='HAVE_GNU_EFI'>

   <refentryinfo>
     <title>systemd-measure</title>
     <productname>systemd</productname>
   </refentryinfo>

   <refmeta>
     <refentrytitle>systemd-measure</refentrytitle>
     <manvolnum>1</manvolnum>
   </refmeta>

   <refnamediv>
     <refname>systemd-measure</refname>
     <refpurpose>Pre-calculate and sign expected TPM2 PCR values for booted unified kernel images</refpurpose>
   </refnamediv>

   <refsynopsisdiv>
     <cmdsynopsis>
       <command>/usr/lib/systemd/systemd-measure <arg choice="opt" rep="repeat">OPTIONS</arg></command>
     </cmdsynopsis>
   </refsynopsisdiv>

   <refsect1>
     <title>Description</title>

     <para>Note: this command is experimental for now. While it is likely to become a regular component of
     systemd, it might still change in behaviour and interface.</para>

     <para><command>systemd-measure</command> is a tool that may be used to pre-calculate and sign the
     expected TPM2 PCR 11 values that should be seen when a unified Linux kernel image based on
     <citerefentry><refentrytitle>systemd-stub</refentrytitle><manvolnum>7</manvolnum></citerefentry> is
     booted up. It accepts paths to the ELF kernel image file, initrd image file, devicetree file, kernel
     command line file,
     <citerefentry><refentrytitle>os-release</refentrytitle><manvolnum>5</manvolnum></citerefentry> file, boot
     splash file, and TPM2 PCR PEM public key file that make up the unified kernel image, and determines the
     PCR values expected to be in place after booting the image. Calculation starts with a zero-initialized
     PCR 11, and is executed in a fashion compatible with what <filename>systemd-stub</filename> does at
     boot. The result may optionally be signed cryptographically, to allow TPM2 policies that can only be
     unlocked if a certain set of kernels is booted, for which such a PCR signature can be provided.</para>
   </refsect1>

   <refsect1>
     <title>Commands</title>

     <para>The following commands are understood:</para>

     <variablelist>
       <varlistentry>
         <term><command>status</command></term>

         <listitem><para>This is the default command if none is specified. This queries the local system's
         TPM2 PCR 11+12+13 values and displays them. The data is written in a similar format as the
         <command>calculate</command> command below, and may be used to quickly compare expectation with
         reality.</para></listitem>
       </varlistentry>

       <varlistentry>
         <term><command>calculate</command></term>

         <listitem><para>Pre-calculate the expected values seen in PCR register 11 after boot-up of a unified
         kernel image consisting of the components specified with <option>--linux=</option>,
         <option>--osrel=</option>, <option>--cmdline=</option>, <option>--initrd=</option>,
         <option>--splash=</option>, <option>--dtb=</option>, <option>--pcrpkey=</option> see below. Only
         <option>--linux=</option> is mandatory. (Alternatively, specify <option>--current</option> to use the
         current values of PCR register 11 instead.)</para></listitem>
       </varlistentry>

       <varlistentry>
         <term><command>sign</command></term>

         <listitem><para>As with the <command>calculate</command> command, pre-calculate the expected value
         seen in TPM2 PCR register 11 after boot-up of a unified kernel image. Then, cryptographically sign
         the resulting values with the private/public key pair (RSA) configured via
         <option>--private-key=</option> and <option>--public-key=</option>. This will write a JSON object to
         standard output that contains signatures for all specified PCR banks (see the
         <option>--pcr-bank=</option> option below), which may be used to unlock encrypted credentials (see
         <citerefentry><refentrytitle>systemd-creds</refentrytitle><manvolnum>1</manvolnum></citerefentry>) or
         LUKS volumes (see
         <citerefentry><refentrytitle>systemd-cryptsetup@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>).
         This allows binding secrets to a set of kernels for which such PCR 11 signatures can be
         provided.</para>

         <para>Note that a TPM2 device must be available for this signing to take place, even though the
         result is not tied to any TPM2 device or its state.</para></listitem>
       </varlistentry>
     </variablelist>
   </refsect1>

   <refsect1>
     <title>Options</title>

     <para>The following options are understood:</para>

     <variablelist>
       <varlistentry>
         <term><option>--linux=<replaceable>PATH</replaceable></option></term>
         <term><option>--osrel=<replaceable>PATH</replaceable></option></term>
         <term><option>--cmdline=<replaceable>PATH</replaceable></option></term>
         <term><option>--initrd=<replaceable>PATH</replaceable></option></term>
         <term><option>--splash=<replaceable>PATH</replaceable></option></term>
         <term><option>--dtb=<replaceable>PATH</replaceable></option></term>
         <term><option>--pcrpkey=<replaceable>PATH</replaceable></option></term>

         <listitem><para>When used with the <command>calculate</command> or <command>sign</command> verb,
         configures the files to read the unified kernel image components from. Each option corresponds with
         the equally named section in the unified kernel PE file. The <option>--linux=</option> switch expects
         the path to the ELF kernel file that the unified PE kernel will wrap. All switches except
         <option>--linux=</option> are optional. Each option may be used at most once.</para></listitem>
       </varlistentry>

       <varlistentry>
         <term><option>--current</option></term>
         <listitem><para>When used with the <command>calculate</command> or <command>sign</command> verb,
         takes the PCR 11 values currently in effect for the system (which should typically reflect the hashes
         of the currently booted kernel). This can be used in place of <option>--linux=</option> and the other
         switches listed above.</para></listitem>
       </varlistentry>

       <varlistentry>
         <term><option>--bank=<replaceable>DIGEST</replaceable></option></term>

         <listitem><para>Controls the PCR banks to pre-calculate the PCR values for – in case
         <command>calculate</command> or <command>sign</command> is invoked –, or the banks to show in the
         <command>status</command> output. May be used more then once to specify multiple banks. If not
         specified, defaults to the four banks <literal>sha1</literal>, <literal>sha256</literal>,
         <literal>sha384</literal>, <literal>sha512</literal>.</para></listitem>
       </varlistentry>

       <varlistentry>
         <term><option>--private-key=<replaceable>PATH</replaceable></option></term>
         <term><option>--public-key=<replaceable>PATH</replaceable></option></term>

         <listitem><para>These switches take paths to a pair of PEM encoded RSA key files, for use with
         the <command>sign</command> command.</para>

         <para>Note the difference between the <option>--pcrpkey=</option> and <option>--public-key=</option>
         switches. The former selects the data to include in the <literal>.pcrpkey</literal> PE section of the
         unified kernel image, the latter picks the public key of the key pair used to sign the resulting PCR
         11 values. The former is the key that the booted system will likely use to lock disk and credential
         encryption to, the latter is the key used for unlocking such resources again. Hence, typically the
         same PEM key should be supplied in both cases.</para>

         <para>If the <option>--public-key=</option> is not specified but <option>--private-key=</option> is
         specified the public key is automatically derived from the private key.</para></listitem>
       </varlistentry>

       <varlistentry>
         <term><option>--tpm2-device=</option><replaceable>PATH</replaceable></term>

         <listitem><para>Controls which TPM2 device to use. Expects a device node path referring to the TPM2
         chip (e.g. <filename>/dev/tpmrm0</filename>). Alternatively the special value <literal>auto</literal>
         may be specified, in order to automatically determine the device node of a suitable TPM2 device (of
         which there must be exactly one). The special value <literal>list</literal> may be used to enumerate
         all suitable TPM2 devices currently discovered.</para></listitem>
       </varlistentry>

       <varlistentry>
         <term><option>--phase=</option><replaceable>PHASE</replaceable></term>

         <listitem><para>Controls which boot phases to calculate expected PCR 11 values for. This takes a
         series of colon-separated strings that encode boot "paths" for entering a specific phase of the boot
         process. Each of the specified strings is measured by the
         <filename>systemd-pcrphase-initrd.service</filename> and
         <citerefentry><refentrytitle>systemd-pcrphase.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
         into PCR 11 during different milestones of the boot process. This switch may be specified multiple
         times to calculate PCR values for multiple boot phases at once. If not used defaults to
         <literal>enter-initrd</literal>, <literal>enter-initrd:leave-initrd</literal>,
         <literal>enter-initrd:leave-initrd:sysinit</literal>,
         <literal>enter-initrd:leave-initrd:sysinit:ready</literal>, i.e. calculates expected PCR values for
         the boot phase in the initrd, during early boot, during later boot, and during system runtime, but
         excluding the phases before the initrd or when shutting down. This setting is honoured both by
         <command>calculate</command> and <command>sign</command>. When used with the latter it's particularly
         useful for generating PCR signatures that can only be used for unlocking resources during specific
         parts of the boot process.</para>

         <para>For further details about PCR boot phases, see
         <citerefentry><refentrytitle>systemd-pcrphase.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para></listitem>
       </varlistentry>

       <varlistentry>
         <term><option>--append=</option><replaceable>PATH</replaceable></term>

         <listitem><para>When generating a PCR JSON signature (via the <command>sign</command> command),
         combine it with a previously generated PCR JSON signature, and output it as one. The specified path
         must refer to a regular file that contains a valid JSON PCR signature object. The specified file is
         not modified. It will be read first, then the newly generated signature appended to it, and the
         resulting object is written to standard output. Use this to generate a single JSON object consisting
         from signatures made with a number of signing keys (for example, to have one key per boot phase). The
         command will suppress duplicates: if a specific signature is already included in a JSON signature
         object it is not added a second time.</para></listitem>
       </varlistentry>

       <xi:include href="standard-options.xml" xpointer="json" />
       <xi:include href="standard-options.xml" xpointer="no-pager" />
       <xi:include href="standard-options.xml" xpointer="help" />
       <xi:include href="standard-options.xml" xpointer="version" />
     </variablelist>
   </refsect1>

   <refsect1>
     <title>Examples</title>

     <example>
       <title>Generate a unified kernel image, and calculate the expected TPM PCR 11 value</title>

       <programlisting># ukify --output foo.efi \
      --os-release @os-release.txt \
      --cmdline @cmdline.txt \
      --splash splash.bmp \
      --devicetree devicetree.dtb \
      --measure \
      vmlinux initrd.cpio
 11:sha1=d775a7b4482450ac77e03ee19bda90bd792d6ec7
 11:sha256=bc6170f9ce28eb051ab465cd62be8cf63985276766cf9faf527ffefb66f45651
 11:sha384=1cf67dff4757e61e5a73d2a21a6694d668629bbc3761747d493f7f49ad720be02fd07263e1f93061243aec599d1ee4b4
 11:sha512=8e79acd3ddbbc8282e98091849c3530f996303c8ac8e87a3b2378b71c8b3a6e86d5c4f41ecea9e1517090c3e8ec0c714821032038f525f744960bcd082d937da
 </programlisting>
     </example>

     <example>
       <title>Generate a private/public key pair, and a unified kernel image, and a TPM PCR 11 signature for
       it, and embed the signature and the public key in the image</title>

       <programlisting># openssl genpkey -algorithm RSA -pkeyopt rsa_keygen_bits:2048 -out tpm2-pcr-private.pem
 # openssl rsa -pubout -in tpm2-pcr-private.pem -out tpm2-pcr-public.pem
 # systemd-measure sign \
      --linux=vmlinux \
      --osrel=os-release.txt \
      --cmdline=cmdline.txt \
      --initrd=initrd.cpio \
      --splash=splash.bmp \
      --dtb=devicetree.dtb \
      --pcrpkey=tpm2-pcr-public.pem \
      --bank=sha1 \
      --bank=sha256 \
      --private-key=tpm2-pcr-private.pem \
      --public-key=tpm2-pcr-public.pem >tpm2-pcr-signature.json
 # ukify --output foo.efi \
      --os-release @os-release.txt \
      --cmdline @cmdline.txt \
      --splash splash.bmp \
      --devicetree devicetree.dtb \
      --pcr-private-key tpm2-pcr-private.pem \
      --pcr-public-key tpm2-pcr-public.pem \
      --pcr-banks sha1,sha256 \
      vmlinux initrd.cpio</programlisting>

      <para>Later on, enroll the signed PCR policy on a LUKS volume:</para>

      <programlisting># systemd-cryptenroll --tpm2-device=auto --tpm2-public-key=tpm2-pcr-public.pem --tpm2-signature=tpm2-pcr-signature.json /dev/sda5</programlisting>

      <para>And then unlock the device with the signature:</para>

      <programlisting># /usr/lib/systemd/systemd-cryptsetup attach myvolume /dev/sda5 - tpm2-device=auto,tpm2-signature=/path/to/tpm2-pcr-signature.json</programlisting>

      <para>Note that when the generated unified kernel image <filename>foo.efi</filename> is booted the
      signature and public key files will be placed at locations <command>systemd-cryptenroll</command> and
      <command>systemd-cryptsetup</command> will look for anyway, and thus these paths do not actually need to
      be specified.</para>
     </example>

     <example>
       <title>Introduce a second public key, signing the same kernel PCR measurements, but only for the initrd boot phase</title>

       <para>This example extends the previous one, but we now introduce a second signing key that is only
       used to sign PCR policies restricted to the initrd boot phase. This can be used to lock down root
       volumes in a way that they can only be unlocked before the transition to the host system. Thus we have
       two classes of secrets or credentials: one that can be unlocked during the entire runtime, and the
       other that can only be used in the initrd.</para>

       <programlisting># openssl genpkey -algorithm RSA -pkeyopt rsa_keygen_bits:2048 -out tpm2-pcr-private.pem
 # openssl rsa -pubout -in tpm2-pcr-private.pem -out tpm2-pcr-public.pem
 # systemd-measure sign \
      --linux=vmlinux \
      --osrel=os-release.txt \
      --cmdline=cmdline.txt \
      --initrd=initrd.cpio \
      --splash=splash.bmp \
      --dtb=devicetree.dtb \
      --pcrpkey=tpm2-pcr-public.pem \
      --bank=sha1 \
      --bank=sha256 \
      --private-key=tpm2-pcr-private.pem \
      --public-key=tpm2-pcr-public.pem >tpm2-pcr-signature.json.tmp
 # openssl genpkey -algorithm RSA -pkeyopt rsa_keygen_bits:2048 -out tpm2-pcr-initrd-private.pem
 # openssl rsa -pubout -in tpm2-pcr-initrd-private.pem -out tpm2-pcr-initrd-public.pem
 # systemd-measure sign \
      --linux=vmlinux \
      --osrel=os-release.txt \
      --cmdline=cmdline.txt \
      --initrd=initrd.cpio \
      --splash=splash.bmp \
      --dtb=devicetree.dtb \
      --pcrpkey=tpm2-pcr-public.pem \
      --bank=sha1 \
      --bank=sha256 \
      --private-key=tpm2-pcr-initrd-private.pem \
      --public-key=tpm2-pcr-initrd-public.pem \
      --phase=enter-initrd \
      --append=tpm2-pcr-signature.json.tmp >tpm2-pcr-signature.json
 # ukify --output foo.efi \
      --os-release @os-release.txt \
      --cmdline @cmdline.txt \
      --splash splash.bmp \
      --devicetree devicetree.dtb \
      --pcr-private-key tpm2-pcr-initrd-private.pem \
      --pcr-public-key tpm2-pcr-initrd-public.pem \
      --section .pcrsig=@tpm2-pcr-signature.json \
      --section .pcrpkey=@tpm2-pcr-public.pem \
      vmlinux initrd.cpio</programlisting>
     </example>

     <para>Note that in this example the <literal>.pcrpkey</literal> PE section contains the key covering all
     boot phases. The <literal>.pcrpkey</literal> is used in the default policies of
     <command>systemd-cryptenroll</command> and <command>systemd-creds</command>. To use the stricter
     <filename>tpm-pcr-initrd-public.pem</filename>-bound policy, specify <option>--tpm2-public-key=</option>
     on the command line of those tools.</para>
   </refsect1>

   <refsect1>
     <title>Exit status</title>

     <para>On success, 0 is returned, a non-zero failure code otherwise.</para>
   </refsect1>

   <refsect1>
     <title>See Also</title>
     <para>
       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
       <citerefentry><refentrytitle>systemd-stub</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
       <citerefentry><refentrytitle>ukify</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
       <citerefentry><refentrytitle>systemd-creds</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
       <citerefentry><refentrytitle>systemd-cryptsetup@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
       <citerefentry><refentrytitle>systemd-pcrphase.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
      </para>
   </refsect1>

 </refentry>
	<?xml version="1.0"?>
	<!---nxml--->
	<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
	"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
	<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
	<refentry id="systemd-measure" xmlns:xi="http://www.w3.org/2001/XInclude" conditional='HAVE_GNU_EFI'>

	<refentryinfo>
	<title>systemd-measure</title>
	<productname>systemd</productname>
	</refentryinfo>

	<refmeta>
	<refentrytitle>systemd-measure</refentrytitle>
	<manvolnum>1</manvolnum>
	</refmeta>

	<refnamediv>
	<refname>systemd-measure</refname>
	<refpurpose>Pre-calculate and sign expected TPM2 PCR values for booted unified kernel images</refpurpose>
	</refnamediv>

	<refsynopsisdiv>
	<cmdsynopsis>
	<command>/usr/lib/systemd/systemd-measure <arg choice="opt" rep="repeat">OPTIONS</arg></command>
	</cmdsynopsis>
	</refsynopsisdiv>

	<refsect1>
	<title>Description</title>

	<para>Note: this command is experimental for now. While it is likely to become a regular component of
	systemd, it might still change in behaviour and interface.</para>

	<para><command>systemd-measure</command> is a tool that may be used to pre-calculate and sign the
	expected TPM2 PCR 11 values that should be seen when a unified Linux kernel image based on
	<citerefentry><refentrytitle>systemd-stub</refentrytitle><manvolnum>7</manvolnum></citerefentry> is
	booted up. It accepts paths to the ELF kernel image file, initrd image file, devicetree file, kernel
	command line file,
	<citerefentry><refentrytitle>os-release</refentrytitle><manvolnum>5</manvolnum></citerefentry> file, boot
	splash file, and TPM2 PCR PEM public key file that make up the unified kernel image, and determines the
	PCR values expected to be in place after booting the image. Calculation starts with a zero-initialized
	PCR 11, and is executed in a fashion compatible with what <filename>systemd-stub</filename> does at
	boot. The result may optionally be signed cryptographically, to allow TPM2 policies that can only be
	unlocked if a certain set of kernels is booted, for which such a PCR signature can be provided.</para>
	</refsect1>

	<refsect1>
	<title>Commands</title>

	<para>The following commands are understood:</para>

	<variablelist>
	<varlistentry>
	<term><command>status</command></term>

	<listitem><para>This is the default command if none is specified. This queries the local system's
	TPM2 PCR 11+12+13 values and displays them. The data is written in a similar format as the
	<command>calculate</command> command below, and may be used to quickly compare expectation with
	reality.</para></listitem>
	</varlistentry>

	<varlistentry>
	<term><command>calculate</command></term>

	<listitem><para>Pre-calculate the expected values seen in PCR register 11 after boot-up of a unified
	kernel image consisting of the components specified with <option>--linux=</option>,
	<option>--osrel=</option>, <option>--cmdline=</option>, <option>--initrd=</option>,
	<option>--splash=</option>, <option>--dtb=</option>, <option>--pcrpkey=</option> see below. Only
	<option>--linux=</option> is mandatory. (Alternatively, specify <option>--current</option> to use the
	current values of PCR register 11 instead.)</para></listitem>
	</varlistentry>

	<varlistentry>
	<term><command>sign</command></term>

	<listitem><para>As with the <command>calculate</command> command, pre-calculate the expected value
	seen in TPM2 PCR register 11 after boot-up of a unified kernel image. Then, cryptographically sign
	the resulting values with the private/public key pair (RSA) configured via
	<option>--private-key=</option> and <option>--public-key=</option>. This will write a JSON object to
	standard output that contains signatures for all specified PCR banks (see the
	<option>--pcr-bank=</option> option below), which may be used to unlock encrypted credentials (see
	<citerefentry><refentrytitle>systemd-creds</refentrytitle><manvolnum>1</manvolnum></citerefentry>) or
	LUKS volumes (see
	<citerefentry><refentrytitle>systemd-cryptsetup@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>).
	This allows binding secrets to a set of kernels for which such PCR 11 signatures can be
	provided.</para>

	<para>Note that a TPM2 device must be available for this signing to take place, even though the
	result is not tied to any TPM2 device or its state.</para></listitem>
	</varlistentry>
	</variablelist>
	</refsect1>

	<refsect1>
	<title>Options</title>

	<para>The following options are understood:</para>

	<variablelist>
	<varlistentry>
	<term><option>--linux=<replaceable>PATH</replaceable></option></term>
	<term><option>--osrel=<replaceable>PATH</replaceable></option></term>
	<term><option>--cmdline=<replaceable>PATH</replaceable></option></term>
	<term><option>--initrd=<replaceable>PATH</replaceable></option></term>
	<term><option>--splash=<replaceable>PATH</replaceable></option></term>
	<term><option>--dtb=<replaceable>PATH</replaceable></option></term>
	<term><option>--pcrpkey=<replaceable>PATH</replaceable></option></term>

	<listitem><para>When used with the <command>calculate</command> or <command>sign</command> verb,
	configures the files to read the unified kernel image components from. Each option corresponds with
	the equally named section in the unified kernel PE file. The <option>--linux=</option> switch expects
	the path to the ELF kernel file that the unified PE kernel will wrap. All switches except
	<option>--linux=</option> are optional. Each option may be used at most once.</para></listitem>
	</varlistentry>

	<varlistentry>
	<term><option>--current</option></term>
	<listitem><para>When used with the <command>calculate</command> or <command>sign</command> verb,
	takes the PCR 11 values currently in effect for the system (which should typically reflect the hashes
	of the currently booted kernel). This can be used in place of <option>--linux=</option> and the other
	switches listed above.</para></listitem>
	</varlistentry>

	<varlistentry>
	<term><option>--bank=<replaceable>DIGEST</replaceable></option></term>

	<listitem><para>Controls the PCR banks to pre-calculate the PCR values for – in case
	<command>calculate</command> or <command>sign</command> is invoked –, or the banks to show in the
	<command>status</command> output. May be used more then once to specify multiple banks. If not
	specified, defaults to the four banks <literal>sha1</literal>, <literal>sha256</literal>,
	<literal>sha384</literal>, <literal>sha512</literal>.</para></listitem>
	</varlistentry>

	<varlistentry>
	<term><option>--private-key=<replaceable>PATH</replaceable></option></term>
	<term><option>--public-key=<replaceable>PATH</replaceable></option></term>

	<listitem><para>These switches take paths to a pair of PEM encoded RSA key files, for use with
	the <command>sign</command> command.</para>

	<para>Note the difference between the <option>--pcrpkey=</option> and <option>--public-key=</option>
	switches. The former selects the data to include in the <literal>.pcrpkey</literal> PE section of the
	unified kernel image, the latter picks the public key of the key pair used to sign the resulting PCR
	11 values. The former is the key that the booted system will likely use to lock disk and credential
	encryption to, the latter is the key used for unlocking such resources again. Hence, typically the
	same PEM key should be supplied in both cases.</para>

	<para>If the <option>--public-key=</option> is not specified but <option>--private-key=</option> is
	specified the public key is automatically derived from the private key.</para></listitem>
	</varlistentry>

	<varlistentry>
	<term><option>--tpm2-device=</option><replaceable>PATH</replaceable></term>

	<listitem><para>Controls which TPM2 device to use. Expects a device node path referring to the TPM2
	chip (e.g. <filename>/dev/tpmrm0</filename>). Alternatively the special value <literal>auto</literal>
	may be specified, in order to automatically determine the device node of a suitable TPM2 device (of
	which there must be exactly one). The special value <literal>list</literal> may be used to enumerate
	all suitable TPM2 devices currently discovered.</para></listitem>
	</varlistentry>

	<varlistentry>
	<term><option>--phase=</option><replaceable>PHASE</replaceable></term>

	<listitem><para>Controls which boot phases to calculate expected PCR 11 values for. This takes a
	series of colon-separated strings that encode boot "paths" for entering a specific phase of the boot
	process. Each of the specified strings is measured by the
	<filename>systemd-pcrphase-initrd.service</filename> and
	<citerefentry><refentrytitle>systemd-pcrphase.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
	into PCR 11 during different milestones of the boot process. This switch may be specified multiple
	times to calculate PCR values for multiple boot phases at once. If not used defaults to
	<literal>enter-initrd</literal>, <literal>enter-initrd:leave-initrd</literal>,
	<literal>enter-initrd:leave-initrd:sysinit</literal>,
	<literal>enter-initrd:leave-initrd:sysinit:ready</literal>, i.e. calculates expected PCR values for
	the boot phase in the initrd, during early boot, during later boot, and during system runtime, but
	excluding the phases before the initrd or when shutting down. This setting is honoured both by
	<command>calculate</command> and <command>sign</command>. When used with the latter it's particularly
	useful for generating PCR signatures that can only be used for unlocking resources during specific
	parts of the boot process.</para>

	<para>For further details about PCR boot phases, see
	<citerefentry><refentrytitle>systemd-pcrphase.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para></listitem>
	</varlistentry>

	<varlistentry>
	<term><option>--append=</option><replaceable>PATH</replaceable></term>

	<listitem><para>When generating a PCR JSON signature (via the <command>sign</command> command),
	combine it with a previously generated PCR JSON signature, and output it as one. The specified path
	must refer to a regular file that contains a valid JSON PCR signature object. The specified file is
	not modified. It will be read first, then the newly generated signature appended to it, and the
	resulting object is written to standard output. Use this to generate a single JSON object consisting
	from signatures made with a number of signing keys (for example, to have one key per boot phase). The
	command will suppress duplicates: if a specific signature is already included in a JSON signature
	object it is not added a second time.</para></listitem>
	</varlistentry>

	<xi:include href="standard-options.xml" xpointer="json" />
	<xi:include href="standard-options.xml" xpointer="no-pager" />
	<xi:include href="standard-options.xml" xpointer="help" />
	<xi:include href="standard-options.xml" xpointer="version" />
	</variablelist>
	</refsect1>

	<refsect1>
	<title>Examples</title>

	<example>
	<title>Generate a unified kernel image, and calculate the expected TPM PCR 11 value</title>

	<programlisting># ukify --output foo.efi \
	--os-release @os-release.txt \
	--cmdline @cmdline.txt \
	--splash splash.bmp \
	--devicetree devicetree.dtb \
	--measure \
	vmlinux initrd.cpio
	11:sha1=d775a7b4482450ac77e03ee19bda90bd792d6ec7
	11:sha256=bc6170f9ce28eb051ab465cd62be8cf63985276766cf9faf527ffefb66f45651
	11:sha384=1cf67dff4757e61e5a73d2a21a6694d668629bbc3761747d493f7f49ad720be02fd07263e1f93061243aec599d1ee4b4
	11:sha512=8e79acd3ddbbc8282e98091849c3530f996303c8ac8e87a3b2378b71c8b3a6e86d5c4f41ecea9e1517090c3e8ec0c714821032038f525f744960bcd082d937da
	</programlisting>
	</example>

	<example>
	<title>Generate a private/public key pair, and a unified kernel image, and a TPM PCR 11 signature for
	it, and embed the signature and the public key in the image</title>

	<programlisting># openssl genpkey -algorithm RSA -pkeyopt rsa_keygen_bits:2048 -out tpm2-pcr-private.pem
	# openssl rsa -pubout -in tpm2-pcr-private.pem -out tpm2-pcr-public.pem
	# systemd-measure sign \
	--linux=vmlinux \
	--osrel=os-release.txt \
	--cmdline=cmdline.txt \
	--initrd=initrd.cpio \
	--splash=splash.bmp \
	--dtb=devicetree.dtb \
	--pcrpkey=tpm2-pcr-public.pem \
	--bank=sha1 \
	--bank=sha256 \
	--private-key=tpm2-pcr-private.pem \
	--public-key=tpm2-pcr-public.pem >tpm2-pcr-signature.json
	# ukify --output foo.efi \
	--os-release @os-release.txt \
	--cmdline @cmdline.txt \
	--splash splash.bmp \
	--devicetree devicetree.dtb \
	--pcr-private-key tpm2-pcr-private.pem \
	--pcr-public-key tpm2-pcr-public.pem \
	--pcr-banks sha1,sha256 \
	vmlinux initrd.cpio</programlisting>

	<para>Later on, enroll the signed PCR policy on a LUKS volume:</para>

	<programlisting># systemd-cryptenroll --tpm2-device=auto --tpm2-public-key=tpm2-pcr-public.pem --tpm2-signature=tpm2-pcr-signature.json /dev/sda5</programlisting>

	<para>And then unlock the device with the signature:</para>

	<programlisting># /usr/lib/systemd/systemd-cryptsetup attach myvolume /dev/sda5 - tpm2-device=auto,tpm2-signature=/path/to/tpm2-pcr-signature.json</programlisting>

	<para>Note that when the generated unified kernel image <filename>foo.efi</filename> is booted the
	signature and public key files will be placed at locations <command>systemd-cryptenroll</command> and
	<command>systemd-cryptsetup</command> will look for anyway, and thus these paths do not actually need to
	be specified.</para>
	</example>

	<example>
	<title>Introduce a second public key, signing the same kernel PCR measurements, but only for the initrd boot phase</title>

	<para>This example extends the previous one, but we now introduce a second signing key that is only
	used to sign PCR policies restricted to the initrd boot phase. This can be used to lock down root
	volumes in a way that they can only be unlocked before the transition to the host system. Thus we have
	two classes of secrets or credentials: one that can be unlocked during the entire runtime, and the
	other that can only be used in the initrd.</para>

	<programlisting># openssl genpkey -algorithm RSA -pkeyopt rsa_keygen_bits:2048 -out tpm2-pcr-private.pem
	# openssl rsa -pubout -in tpm2-pcr-private.pem -out tpm2-pcr-public.pem
	# systemd-measure sign \
	--linux=vmlinux \
	--osrel=os-release.txt \
	--cmdline=cmdline.txt \
	--initrd=initrd.cpio \
	--splash=splash.bmp \
	--dtb=devicetree.dtb \
	--pcrpkey=tpm2-pcr-public.pem \
	--bank=sha1 \
	--bank=sha256 \
	--private-key=tpm2-pcr-private.pem \
	--public-key=tpm2-pcr-public.pem >tpm2-pcr-signature.json.tmp
	# openssl genpkey -algorithm RSA -pkeyopt rsa_keygen_bits:2048 -out tpm2-pcr-initrd-private.pem
	# openssl rsa -pubout -in tpm2-pcr-initrd-private.pem -out tpm2-pcr-initrd-public.pem
	# systemd-measure sign \
	--linux=vmlinux \
	--osrel=os-release.txt \
	--cmdline=cmdline.txt \
	--initrd=initrd.cpio \
	--splash=splash.bmp \
	--dtb=devicetree.dtb \
	--pcrpkey=tpm2-pcr-public.pem \
	--bank=sha1 \
	--bank=sha256 \
	--private-key=tpm2-pcr-initrd-private.pem \
	--public-key=tpm2-pcr-initrd-public.pem \
	--phase=enter-initrd \
	--append=tpm2-pcr-signature.json.tmp >tpm2-pcr-signature.json
	# ukify --output foo.efi \
	--os-release @os-release.txt \
	--cmdline @cmdline.txt \
	--splash splash.bmp \
	--devicetree devicetree.dtb \
	--pcr-private-key tpm2-pcr-initrd-private.pem \
	--pcr-public-key tpm2-pcr-initrd-public.pem \
	--section .pcrsig=@tpm2-pcr-signature.json \
	--section .pcrpkey=@tpm2-pcr-public.pem \
	vmlinux initrd.cpio</programlisting>
	</example>

	<para>Note that in this example the <literal>.pcrpkey</literal> PE section contains the key covering all
	boot phases. The <literal>.pcrpkey</literal> is used in the default policies of
	<command>systemd-cryptenroll</command> and <command>systemd-creds</command>. To use the stricter
	<filename>tpm-pcr-initrd-public.pem</filename>-bound policy, specify <option>--tpm2-public-key=</option>
	on the command line of those tools.</para>
	</refsect1>

	<refsect1>
	<title>Exit status</title>

	<para>On success, 0 is returned, a non-zero failure code otherwise.</para>
	</refsect1>

	<refsect1>
	<title>See Also</title>
	<para>
	<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
	<citerefentry><refentrytitle>systemd-stub</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
	<citerefentry><refentrytitle>ukify</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
	<citerefentry><refentrytitle>systemd-creds</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
	<citerefentry><refentrytitle>systemd-cryptsetup@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
	<citerefentry><refentrytitle>systemd-pcrphase.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
	</para>
	</refsect1>

	</refentry>