tpm2-clear: optionally reset TPM during a factory reset
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Lennart Poettering
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@ -819,3 +819,18 @@ systemd-networkd, has been changed by another, unrelated process
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and will likely result in problems later on.
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Value changed to "@NEWVALUE@", which should be "@OURVALUE@".
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-- 438188861e0b427a9d638a90487a0ca6
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Subject: TPM clear requested
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Defined-By: systemd
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Support: %SUPPORT_URL%
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Documentation: man:systemd-tpm2-clear.service(8)
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A request to clear the TPM security chip has been issued to the firmware. This
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is typically done as part of a comprehensive factory reset operation, and
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ensures that on the next boot process the firmware will reset the TPM, after
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interactively requesting confirmation by the user.
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Clearing the TPM has the effect of invalidating all keys locked to the TPM,
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including full disk encryption keys. Because of that care should be taken that
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access to relevant resources is retained via other means.
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@ -767,3 +767,10 @@ Tools using the Varlink protocol (such as `varlinkctl`) or sd-bus (such as
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`process`, `session`, `user`, `user-session`, or `group`. Controls the kernel
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keyring in which `systemd-ask-password` caches the queried password. Defaults
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to `user`.
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`systemd-tpm2-clear`:
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* `SYSTEMD_TPM2_ALLOW_CLEAR` – takes a boolean. Overrides the effect of the
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`systemd.factory_reset=` kernel command line option: if set to false,
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requesting a TPM clearing is skipped, and the command immediately exits
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successfully.
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@ -752,6 +752,15 @@
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<xi:include href="version-info.xml" xpointer="v245"/></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>systemd.tpm2_allow_clear=</varname></term>
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<listitem><para>Controls whether to allow clearing of the TPM chip, implemented by
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<citerefentry><refentrytitle>systemd-tpm2-clear</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
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<xi:include href="version-info.xml" xpointer="v258"/></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>systemd.tpm2_wait=</varname></term>
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@ -1142,6 +1142,7 @@ manpages = [
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'systemd-tmpfiles-setup-dev.service',
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'systemd-tmpfiles-setup.service'],
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''],
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['systemd-tpm2-clear.service', '8', [], 'ENABLE_BOOTLOADER'],
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['systemd-tpm2-generator', '8', [], ''],
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['systemd-tpm2-setup.service',
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'8',
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@ -0,0 +1,90 @@
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<?xml version="1.0"?>
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<!--*-nxml-*-->
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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"http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd">
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<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
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<refentry id="systemd-tpm2-clear.service" conditional='ENABLE_BOOTLOADER'
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xmlns:xi="http://www.w3.org/2001/XInclude">
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<refentryinfo>
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<title>systemd-tpm2-clear.service</title>
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<productname>systemd</productname>
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</refentryinfo>
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<refmeta>
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<refentrytitle>systemd-tpm2-clear.service</refentrytitle>
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<manvolnum>8</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>systemd-tpm2-clear.service</refname>
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<refpurpose>Request that the TPM security chip is cleared on next boot</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<para><filename>systemd-tpm2-clear.service</filename></para>
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<para><filename>/usr/lib/systemd/systemd-tpm2-clear</filename></para>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para><filename>systemd-tpm2-clear.service</filename> is a service that requests that the TPM is reset by
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the PC firmware on the next boot. It makes use of the TPM Physical Presence Interface (PPI). Note that
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this service does not immediately execute the clear operation, but simply asks the PC firmware to execute
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it at next boot, where the user will be asked for confirmation before the operation is done.</para>
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<para><filename>systemd-tpm2-clear.service</filename> is typically hooked into the
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<filename>factory-reset.target</filename> unit in order to request the TPM request before an immediate
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reboot. See <ulink url="https://systemd.io/FACTORY_RESET">Factory Reset</ulink> for more
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information.</para>
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</refsect1>
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<refsect1>
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<title>Options</title>
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<para>The following options are understood:</para>
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<variablelist>
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<varlistentry>
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<term><option>--graceful</option></term>
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<listitem><para>Exit cleanly and execute no operation if the system does not possess a TPM
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chip.</para>
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<xi:include href="version-info.xml" xpointer="v258"/></listitem>
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</varlistentry>
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<xi:include href="standard-options.xml" xpointer="help" />
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<xi:include href="standard-options.xml" xpointer="version" />
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</variablelist>
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</refsect1>
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<refsect1>
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<title>Kernel Command Line</title>
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<para><filename>systemd-tpm2-clear</filename> understands the following kernel command line
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parameters:</para>
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<variablelist class='kernel-commandline-options'>
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<varlistentry>
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<term><varname>systemd.tpm2_allow_clear=</varname></term>
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<listitem><para>Takes a boolean argument. If false the service will succeed, but instead of requesting
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the TPM clear operation from the PC firmware it will not execute any operation. If not specified
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defaults to true.</para>
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<xi:include href="version-info.xml" xpointer="v258"/></listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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<refsect1>
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<title>See Also</title>
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<para><simplelist type="inline">
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<member><citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
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<member><citerefentry><refentrytitle>systemd-tpm2-setup.service</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
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<member><citerefentry><refentrytitle>systemd-factory-reset-request.service</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
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</simplelist></para>
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</refsect1>
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</refentry>
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@ -33,6 +33,7 @@ enable systemd-pstore.service
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enable systemd-resolved.service
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enable systemd-sysext.service
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enable systemd-timesyncd.service
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enable systemd-tpm2-clear.service
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enable systemd-userdbd.socket
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disable console-getty.service
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@ -278,6 +278,8 @@ _SD_BEGIN_DECLARATIONS;
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#define SD_MESSAGE_SRK_ENROLLMENT_NEEDS_AUTHORIZATION SD_ID128_MAKE(ad,70,89,f9,28,ac,4f,7e,a0,0c,07,45,7d,47,ba,8a)
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#define SD_MESSAGE_SRK_ENROLLMENT_NEEDS_AUTHORIZATION_STR SD_ID128_MAKE_STR(ad,70,89,f9,28,ac,4f,7e,a0,0c,07,45,7d,47,ba,8a)
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#define SD_MESSAGE_TPM2_CLEAR_REQUESTED SD_ID128_MAKE(43,81,88,86,1e,0b,42,7a,9d,63,8a,90,48,7a,0c,a6)
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#define SD_MESSAGE_TPM2_CLEAR_REQUESTED_STR SD_ID128_MAKE_STR(43,81,88,86,1e,0b,42,7a,9d,63,8a,90,48,7a,0c,a6)
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#define SD_MESSAGE_SYSCTL_CHANGED SD_ID128_MAKE(9c,f5,6b,8b,af,95,46,cf,94,78,78,3a,8d,e4,21,13)
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#define SD_MESSAGE_SYSCTL_CHANGED_STR SD_ID128_MAKE_STR(9c,f5,6b,8b,af,95,46,cf,94,78,78,3a,8d,e4,21,13)
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@ -13,6 +13,13 @@ executables += [
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libopenssl,
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],
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},
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libexec_template + {
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'name' : 'systemd-tpm2-clear',
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'sources' : files('tpm2-clear.c'),
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'conditions' : [
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'HAVE_TPM2',
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],
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},
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generator_template + {
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'name' : 'systemd-tpm2-generator',
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'sources' : files('tpm2-generator.c'),
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@ -0,0 +1,140 @@
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/* SPDX-License-Identifier: LGPL-2.1-or-later */
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#include <getopt.h>
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#include "sd-messages.h"
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#include "build.h"
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#include "env-util.h"
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#include "fileio.h"
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#include "main-func.h"
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#include "pretty-print.h"
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#include "proc-cmdline.h"
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#include "tpm2-util.h"
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static bool arg_graceful = false;
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static int help(void) {
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_cleanup_free_ char *link = NULL;
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int r;
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r = terminal_urlify_man("systemd-tpm2-clear", "8", &link);
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if (r < 0)
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return log_oom();
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printf("%1$s [OPTIONS...]\n"
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"\n%5$sRequest clearing of the TPM2 from PC firmware.%6$s\n"
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"\n%3$sOptions:%4$s\n"
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" -h --help Show this help\n"
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" --version Show package version\n"
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" --graceful Exit gracefully if no TPM2 device is found\n"
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"\nSee the %2$s for details.\n",
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program_invocation_short_name,
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link,
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ansi_underline(),
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ansi_normal(),
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ansi_highlight(),
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ansi_normal());
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return 0;
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}
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static int parse_argv(int argc, char *argv[]) {
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enum {
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ARG_VERSION = 0x100,
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ARG_GRACEFUL,
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};
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static const struct option options[] = {
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{ "help", no_argument, NULL, 'h' },
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{ "version", no_argument, NULL, ARG_VERSION },
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{ "graceful", no_argument, NULL, ARG_GRACEFUL },
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{}
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};
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int c;
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assert(argc >= 0);
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assert(argv);
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while ((c = getopt_long(argc, argv, "h", options, NULL)) >= 0)
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switch (c) {
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case 'h':
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return help();
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case ARG_VERSION:
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return version();
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case ARG_GRACEFUL:
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arg_graceful = true;
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break;
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case '?':
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return -EINVAL;
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default:
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assert_not_reached();
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}
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if (optind != argc)
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return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "This program expects no arguments.");
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return 1;
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}
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static int request_tpm2_clear(void) {
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int r, clear = -1;
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r = secure_getenv_bool("SYSTEMD_TPM2_ALLOW_CLEAR");
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if (r < 0 && r != -ENXIO)
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log_warning_errno(r, "Failed to parse $SYSTEMD_TPM2_ALLOW_CLEAR, ignoring: %m");
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if (r >= 0)
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clear = r;
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if (clear < 0) {
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bool b;
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r = proc_cmdline_get_bool("systemd.tpm2_allow_clear", /* flags= */ 0, &b);
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if (r < 0)
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return log_debug_errno(r, "Failed to parse systemd.tpm2_allow_clear kernel command line argument: %m");
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if (r > 0)
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clear = b;
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}
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if (clear == 0) {
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log_info("Clearing TPM2 disabled, exiting early.");
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return EXIT_SUCCESS;
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}
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/* Now issue PPI request */
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r = write_string_file("/sys/class/tpm/tpm0/ppi/request", "5", /* flags= */ 0);
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if (r < 0)
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return log_error_errno(r, "Failed to request TPM2 cleaing via PPI, unable to write to /sys/class/tpm/tpm0/ppi/request: %m");
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log_struct(LOG_NOTICE,
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"MESSAGE_ID=" SD_MESSAGE_TPM2_CLEAR_REQUESTED_STR,
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LOG_MESSAGE("Requested TPM2 clearing via PPI. Firmware will verify with user and clear TPM on reboot."));
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return 0;
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}
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static int run(int argc, char *argv[]) {
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int r;
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log_setup();
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r = parse_argv(argc, argv);
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if (r <= 0)
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return r;
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/* If we don't fully support the TPM we are unlikely able to reinitialize it after boot, hence don't
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* be tempted to reset it in graceful mode. Otherwise we might destroy something without being able
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* to rebuild it. */
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if (arg_graceful && !tpm2_is_fully_supported()) {
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log_notice("No complete TPM2 support detected, exiting gracefully.");
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return EXIT_SUCCESS;
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}
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return request_tpm2_clear();
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}
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DEFINE_MAIN_FUNCTION_WITH_POSITIVE_FAILURE(run);
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@ -571,6 +571,10 @@ units = [
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'conditions' : ['ENABLE_BOOTLOADER', 'HAVE_OPENSSL', 'HAVE_TPM2'],
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'symlinks' : ['sysinit.target.wants/'],
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},
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{
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'file' : 'systemd-tpm2-clear.service.in',
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'conditions' : ['ENABLE_BOOTLOADER', 'HAVE_OPENSSL', 'HAVE_TPM2'],
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},
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{
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'file' : 'systemd-tpm2-setup.service.in',
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'conditions' : ['ENABLE_BOOTLOADER', 'HAVE_OPENSSL', 'HAVE_TPM2'],
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@ -0,0 +1,33 @@
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# SPDX-License-Identifier: LGPL-2.1-or-later
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#
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# This file is part of systemd.
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#
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# systemd is free software; you can redistribute it and/or modify it
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# under the terms of the GNU Lesser General Public License as published by
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# the Free Software Foundation; either version 2.1 of the License, or
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# (at your option) any later version.
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[Unit]
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Description=Issue TPM Clear Request
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Documentation=man:systemd-tpm2-clear.service(8)
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DefaultDependencies=no
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Conflicts=shutdown.target
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After=tpm2.target systemd-pcrphase-factory-reset.service
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Before=factory-reset.target shutdown.target
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# Note all systems that have a TPM implement the "Physical Presence Interface" (PPI)
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ConditionPathExists=/sys/class/tpm/tpm0/ppi/request
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# Only do this if we can be reasonably sure people accept our TPM use, which we
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# derive here from the fact that UKIs are used. Because if they do they are OK
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# with our SRK initialization and our PCR measurements, and hence should also
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# be OK with our TPM resets.
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ConditionSecurity=measured-uki
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[Service]
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Type=oneshot
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RemainAfterExit=yes
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ExecStart={{LIBEXECDIR}}/systemd-tpm2-clear --graceful
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[Install]
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WantedBy=factory-reset.target
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