units: measure the fact we enter storage target mode into TPM

storagetm mode means we we are network accessible. let's lock down
access to TPM secrets in this case: let's measure a pcr "phase" string
into PCR 11.

This is good as it means that if we are exploited in this state FDE
secrets protected by TPM are likely to remain protected, since the PCR
values wouldn't allow access.

units/meson.build

@@ -542,6 +542,11 @@ units = [
           'conditions' : ['ENABLE_BOOTLOADER', 'HAVE_OPENSSL', 'HAVE_TPM2'],
           'symlinks' : ['sysinit.target.wants/'],
         },
+        {
+          'file' : 'systemd-pcrphase-storage-target-mode.service.in',
+          'conditions' : ['ENABLE_BOOTLOADER', 'HAVE_OPENSSL', 'HAVE_TPM2'],
+          'symlinks' : ['storage-target-mode.target.wants/'],
+        },
         {
           'file' : 'systemd-pcrphase.service.in',
           'conditions' : ['ENABLE_BOOTLOADER', 'HAVE_OPENSSL', 'HAVE_TPM2'],

units/systemd-pcrphase-storage-target-mode.service.in

@@ -0,0 +1,24 @@
+#  SPDX-License-Identifier: LGPL-2.1-or-later
+#
+#  This file is part of systemd.
+#
+#  systemd is free software; you can redistribute it and/or modify it
+#  under the terms of the GNU Lesser General Public License as published by
+#  the Free Software Foundation; either version 2.1 of the License, or
+#  (at your option) any later version.
+
+[Unit]
+Description=TPM PCR Barrier (Storage Target Mode)
+Documentation=man:systemd-pcrphase-storage-target-mode.service(8)
+DefaultDependencies=no
+Conflicts=shutdown.target
+After=tpm2.target
+Before=shutdown.target
+ConditionPathExists=/etc/initrd-release
+ConditionSecurity=measured-uki
+
+[Service]
+Type=oneshot
+RemainAfterExit=yes
+ExecStart={{LIBEXECDIR}}/systemd-pcrextend --graceful storage-target-mode-start
+ExecStop={{LIBEXECDIR}}/systemd-pcrextend --graceful storage-target-mode-stop

units/systemd-storagetm.service.in

@@ -13,7 +13,7 @@ Documentation=man:systemd-storagetm.service(8)
 ConditionVirtualization=!container
 DefaultDependencies=no
 Wants=modprobe@nvmet_tcp.service modprobe@thunderbolt_net.service sys-kernel-config.mount
-After=modprobe@nvmet_tcp.service modprobe@thunderbolt_net.service sys-kernel-config.mount plymouth-start.service
+After=modprobe@nvmet_tcp.service modprobe@thunderbolt_net.service sys-kernel-config.mount plymouth-start.service systemd-pcrphase-storage-target-mode.service
 Conflicts=shutdown.target
 Before=shutdown.target
 FailureAction=reboot