From 0318d54539fe168822447889ac0e858a10c55f74 Mon Sep 17 00:00:00 2001
From: Lennart Poettering <lennart@poettering.net>
Date: Thu, 15 Dec 2022 18:07:20 +0100
Subject: [PATCH] pcrphase: gracefully exit if TPM2 support is incomplete

If everything points to the fact that TPM2 should work, but then the
driver fails to initialize we should handle this gracefully and not
cause failing services all over the place.

Fixes: #25700
---
 man/systemd-pcrphase.service.xml          |  8 ++++++++
 src/boot/pcrphase.c                       | 13 +++++++++++++
 units/systemd-pcrphase-initrd.service.in  |  4 ++--
 units/systemd-pcrphase-sysinit.service.in |  4 ++--
 units/systemd-pcrphase.service.in         |  4 ++--
 5 files changed, 27 insertions(+), 6 deletions(-)

diff --git a/man/systemd-pcrphase.service.xml b/man/systemd-pcrphase.service.xml
index 9eda503e4c..9b7cc80b3a 100644
--- a/man/systemd-pcrphase.service.xml
+++ b/man/systemd-pcrphase.service.xml
@@ -131,6 +131,14 @@
         all suitable TPM2 devices currently discovered.</para></listitem>
       </varlistentry>
 
+      <varlistentry>
+        <term><option>--graceful</option></term>
+
+        <listitem><para>If no TPM2 firmware, kernel subsystem, kernel driver or device support is found, exit
+        with exit status 0 (i.e. indicate success). If this is not specified any attempt to measure without a
+        TPM2 device will cause the invocation to fail.</para></listitem>
+      </varlistentry>
+
       <xi:include href="standard-options.xml" xpointer="help" />
       <xi:include href="standard-options.xml" xpointer="version" />
 
diff --git a/src/boot/pcrphase.c b/src/boot/pcrphase.c
index 9ae1709253..14f79f23c0 100644
--- a/src/boot/pcrphase.c
+++ b/src/boot/pcrphase.c
@@ -14,6 +14,7 @@
 #include "tpm-pcr.h"
 #include "tpm2-util.h"
 
+static bool arg_graceful = false;
 static char *arg_tpm2_device = NULL;
 static char **arg_banks = NULL;
 
@@ -35,6 +36,7 @@ static int help(int argc, char *argv[], void *userdata) {
                "     --version           Print version\n"
                "     --bank=DIGEST       Select TPM bank (SHA1, SHA256)\n"
                "     --tpm2-device=PATH  Use specified TPM2 device\n"
+               "     --graceful          Exit gracefully if no TPM2 device is found\n"
                "\nSee the %2$s for details.\n",
                program_invocation_short_name,
                link,
@@ -51,6 +53,7 @@ static int parse_argv(int argc, char *argv[]) {
                 ARG_VERSION = 0x100,
                 ARG_BANK,
                 ARG_TPM2_DEVICE,
+                ARG_GRACEFUL,
         };
 
         static const struct option options[] = {
@@ -58,6 +61,7 @@ static int parse_argv(int argc, char *argv[]) {
                 { "version",     no_argument,       NULL, ARG_VERSION     },
                 { "bank",        required_argument, NULL, ARG_BANK        },
                 { "tpm2-device", required_argument, NULL, ARG_TPM2_DEVICE },
+                { "graceful",    no_argument,       NULL, ARG_GRACEFUL    },
                 {}
         };
 
@@ -105,6 +109,10 @@ static int parse_argv(int argc, char *argv[]) {
                         break;
                 }
 
+                case ARG_GRACEFUL:
+                        arg_graceful = true;
+                        break;
+
                 case '?':
                         return -EINVAL;
 
@@ -174,6 +182,11 @@ static int run(int argc, char *argv[]) {
         if (isempty(word))
                 return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "String to measure cannot be empty, refusing.");
 
+        if (arg_graceful && tpm2_support() != TPM2_SUPPORT_FULL) {
+                log_notice("No complete TPM2 support detected, exiting gracefully.");
+                return EXIT_SUCCESS;
+        }
+
         length = strlen(word);
 
         int b = getenv_bool("SYSTEMD_PCRPHASE_STUB_VERIFY");
diff --git a/units/systemd-pcrphase-initrd.service.in b/units/systemd-pcrphase-initrd.service.in
index c1ad5ef844..e437c7e1ce 100644
--- a/units/systemd-pcrphase-initrd.service.in
+++ b/units/systemd-pcrphase-initrd.service.in
@@ -20,5 +20,5 @@ ConditionPathExists=/sys/firmware/efi/efivars/StubPcrKernelImage-4a67b082-0a4c-4
 [Service]
 Type=oneshot
 RemainAfterExit=yes
-ExecStart={{ROOTLIBEXECDIR}}/systemd-pcrphase enter-initrd
-ExecStop={{ROOTLIBEXECDIR}}/systemd-pcrphase leave-initrd
+ExecStart={{ROOTLIBEXECDIR}}/systemd-pcrphase --graceful enter-initrd
+ExecStop={{ROOTLIBEXECDIR}}/systemd-pcrphase --graceful leave-initrd
diff --git a/units/systemd-pcrphase-sysinit.service.in b/units/systemd-pcrphase-sysinit.service.in
index 6b5ba7d878..a22fbbe935 100644
--- a/units/systemd-pcrphase-sysinit.service.in
+++ b/units/systemd-pcrphase-sysinit.service.in
@@ -21,5 +21,5 @@ ConditionPathExists=/sys/firmware/efi/efivars/StubPcrKernelImage-4a67b082-0a4c-4
 [Service]
 Type=oneshot
 RemainAfterExit=yes
-ExecStart={{ROOTLIBEXECDIR}}/systemd-pcrphase sysinit
-ExecStop={{ROOTLIBEXECDIR}}/systemd-pcrphase final
+ExecStart={{ROOTLIBEXECDIR}}/systemd-pcrphase --graceful sysinit
+ExecStop={{ROOTLIBEXECDIR}}/systemd-pcrphase --graceful final
diff --git a/units/systemd-pcrphase.service.in b/units/systemd-pcrphase.service.in
index ce469befa8..5ba437e5b1 100644
--- a/units/systemd-pcrphase.service.in
+++ b/units/systemd-pcrphase.service.in
@@ -19,5 +19,5 @@ ConditionPathExists=/sys/firmware/efi/efivars/StubPcrKernelImage-4a67b082-0a4c-4
 [Service]
 Type=oneshot
 RemainAfterExit=yes
-ExecStart={{ROOTLIBEXECDIR}}/systemd-pcrphase ready
-ExecStop={{ROOTLIBEXECDIR}}/systemd-pcrphase shutdown
+ExecStart={{ROOTLIBEXECDIR}}/systemd-pcrphase --graceful ready
+ExecStop={{ROOTLIBEXECDIR}}/systemd-pcrphase --graceful shutdown