From b7f74506b4a479edf2d7c5b9c08fb105e3fd7b29 Mon Sep 17 00:00:00 2001 From: Lennart Poettering Date: Tue, 20 Dec 2022 17:16:47 +0100 Subject: [PATCH] =?UTF-8?q?units:=20rename/rework=20systemd-boot-system-to?= =?UTF-8?q?ken.service=20=E2=86=92=20systemd-boot-random-seed.service?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit This renames systemd-boot-system-token.service to systemd-boot-random-seed.service and conditions it less strictly. Previously, the job of the service was to write a "system token" EFI variable if it was missing. It called "bootctl --graceful random-seed" for that. With this change we condition it more liberally: instead of calling it only when the "system token" EFI variable isn't set, we call it whenever a boot loader interface compatible boot loader is used. This means, previously it was invoked on the first boot only: now it is invoked at every boot. This doesn#t change the command that is invoked. That's because previously already the "bootctl --graceful random-seed" did two things: set the system token if not set yet *and* refresh the random seed in the ESP. Previousy we put the focus on the former, now we shift the focus to the latter. With this simple change we can replace the logic f913c784ad4c93894fd6cb2590738113dff5a694 added, but from a service that can run much later and doesn't keep the ESP pinned. (cherry picked from commit 921fc451cb7ce29467c5d87346db2b8bb72fdf18) Related: RHEL-16952 --- man/bootctl.xml | 4 +- man/rules/meson.build | 2 +- man/systemd-boot-random-seed.service.xml | 99 +++++++++++++++++++++++ man/systemd-boot-system-token.service.xml | 76 ----------------- man/systemd-boot.xml | 2 +- man/systemd-random-seed.service.xml | 6 +- units/meson.build | 2 +- units/systemd-boot-random-seed.service | 15 ++-- units/systemd-boot-update.service | 3 +- units/systemd-random-seed.service.in | 4 +- 10 files changed, 120 insertions(+), 93 deletions(-) create mode 100644 man/systemd-boot-random-seed.service.xml delete mode 100644 man/systemd-boot-system-token.service.xml diff --git a/man/bootctl.xml b/man/bootctl.xml index d82f12d5bb..27b45c06d3 100644 --- a/man/bootctl.xml +++ b/man/bootctl.xml @@ -208,7 +208,7 @@ OS and a new seed to store in the ESP from the combination of both. The random seed passed to the OS is credited to the kernel's entropy pool by the system manager during early boot, and permits userspace to boot up with an entropy pool fully initialized very early on. Also see - systemd-boot-system-token.service8. + systemd-boot-random-seed.service8. See Random Seeds for further information. @@ -550,7 +550,7 @@ Boot Loader Entries: systemd-boot7, Boot Loader Specification, Boot Loader Interface, - systemd-boot-system-token.service8 + systemd-boot-random-seed.service8 diff --git a/man/rules/meson.build b/man/rules/meson.build index 9c0d773e51..beecc893fd 100644 --- a/man/rules/meson.build +++ b/man/rules/meson.build @@ -863,7 +863,7 @@ manpages = [ '8', ['systemd-boot-check-no-failures'], ''], - ['systemd-boot-system-token.service', '8', [], 'HAVE_GNU_EFI'], + ['systemd-boot-random-seed.service', '8', [], 'HAVE_GNU_EFI'], ['systemd-boot', '7', ['sd-boot'], 'HAVE_GNU_EFI'], ['systemd-cat', '1', [], ''], ['systemd-cgls', '1', [], ''], diff --git a/man/systemd-boot-random-seed.service.xml b/man/systemd-boot-random-seed.service.xml new file mode 100644 index 0000000000..86ce639828 --- /dev/null +++ b/man/systemd-boot-random-seed.service.xml @@ -0,0 +1,99 @@ + + + + + + + + systemd-boot-random-seed.service + systemd + + + + systemd-boot-random-seed.service + 8 + + + + systemd-boot-random-seed.service + Refresh boot loader random seed at boot + + + + systemd-boot-random-seed.service + + + + Description + + systemd-boot-random-seed.service is a system service that automatically + refreshes the boot loader random seed stored in the EFI System Partition (ESP), from the Linux kernel + entropy pool. The boot loader random seed is primarily consumed and updated by + systemd-boot7 from the + UEFI environemnt (or + systemd-stub7 if the + former is not used, but the latter is), and passed as initial RNG seed to the OS. It is an effective way + to ensure the OS comes up with a random pool that is fully initialized. + + The service also automatically generates a 'system token' to store in an EFI variable in the + system's NVRAM. The boot loader may then combine the on-disk random seed and the system token by + cryptographic hashing, and pass it to the OS it boots as initialization seed for its entropy pool. Note: + the random seed stored in the ESP is refreshed on every reboot ensuring that + multiple subsequent boots will boot with different seeds. On the other hand, the system token is + generated randomly once, and then persistently stored in the system's EFI variable + storage, ensuring the same disk image won't result in the same series of boot loader seed values if used + on multiple systems in parallel. + + The systemd-boot-random-seed.service unit invokes the bootctl + random-seed command, which updates the random seed in the ESP, and initializes the system + token if it's not initialized yet. The service is conditionalized so that it is run only when a boot + loader is used that implements the Boot Loader + Interface. For further details see + bootctl1, regarding + the command this service invokes. + + Note the relationship between systemd-boot-random-seed.service and + systemd-random-seed8. The + former maintains the random seed consumed and updated by the boot environment (i.e. by + systemd-boot7 or + systemd-stub7), the + latter maintains a random seed consumed and updated by the OS itself. The former ensures that the OS has + a filled entropy pool already during earliest boot when regular disk access is not available yet + (i.e. when the OS random seed cannot be loaded yet). The latter is processed much later, once writable + disk access is available. Thus it cannot be used to seed the initial boot phase, but typically has much + higher quality of entropy. Both files are consumed and updated at boot, but at different + times. Specifically: + + + In UEFI mode, the systemd-boot or + systemd-stub components load the boot loader random seed off the ESP, hash it with + available entropy and the system token, and then update it on disk. A derived seed is passed to the + kernel which writes it to its entropy pool. + + In userspace the systemd-random-seed.service service loads the OS + random seed, writes it to the kernel entropy pool, and then updates it on disk with a new value derived + from the kernel entropy pool. + + In userspace the systemd-boot-random-seed.service service updates + the boot loader random seed with a new value derived from the kernel kernel entropy pool. + + + This logic should ensure that the kernel's entropy pool is seeded during earliest bool already, if + possible, but the highest quality entropy is propagated back to both on-disk seeds. + + + + See Also + + systemd1, + random4, + bootctl1, + systemd-boot7, + systemd-stub7, + systemd-random-seed.service8 + + + + diff --git a/man/systemd-boot-system-token.service.xml b/man/systemd-boot-system-token.service.xml deleted file mode 100644 index f2e30a9b13..0000000000 --- a/man/systemd-boot-system-token.service.xml +++ /dev/null @@ -1,76 +0,0 @@ - - - - - - - - systemd-boot-system-token.service - systemd - - - - systemd-boot-system-token.service - 8 - - - - systemd-boot-system-token.service - Generate an initial boot loader system token and random seed - - - - systemd-boot-system-token.service - - - - Description - - systemd-boot-system-token.service is a system service that automatically - generates a 'system token' to store in an EFI variable in the system's NVRAM and a random seed to store - on the EFI System Partition ESP on disk. The boot loader may then combine these two randomized data - fields by cryptographic hashing, and pass it to the OS it boots as initialization seed for its entropy - pool. The random seed stored in the ESP is refreshed on each reboot ensuring that multiple subsequent - boots will boot with different seeds. The 'system token' is generated randomly once, and then - persistently stored in the system's EFI variable storage. - - The systemd-boot-system-token.service unit invokes the bootctl - random-seed command, which updates the random seed in the ESP, and initializes the 'system - token' if it's not initialized yet. The service is conditionalized so that it is run only when all of the - below apply: - - - A boot loader is used that implements the Boot Loader Interface (which defines the 'system - token' concept). - - Either a 'system token' was not set yet, or the boot loader has not passed the OS a - random seed yet (and thus most likely has been missing the random seed file in the - ESP). - - The system is not running in a VM environment. This case is explicitly excluded since - on VM environments the ESP backing storage and EFI variable storage is typically not physically - separated and hence booting the same OS image in multiple instances would replicate both, thus reusing - the same random seed and 'system token' among all instances, which defeats its purpose. Note that it's - still possible to use boot loader random seed provisioning in this mode, but the automatic logic - implemented by this service has no effect then, and the user instead has to manually invoke the - bootctl random-seed acknowledging these restrictions. - - - For further details see - bootctl1, regarding - the command this service invokes. - - - - See Also - - systemd1, - bootctl1, - systemd-boot7 - - - - diff --git a/man/systemd-boot.xml b/man/systemd-boot.xml index f96c4c6512..773d6988e3 100644 --- a/man/systemd-boot.xml +++ b/man/systemd-boot.xml @@ -526,7 +526,7 @@ bootctl1, loader.conf5, systemd-bless-boot.service8, - systemd-boot-system-token.service8, + systemd-boot-random-seed.service8, kernel-install8, systemd-stub7, Boot Loader Specification, diff --git a/man/systemd-random-seed.service.xml b/man/systemd-random-seed.service.xml index a1e31cd460..bc8cf50a39 100644 --- a/man/systemd-random-seed.service.xml +++ b/man/systemd-random-seed.service.xml @@ -18,7 +18,7 @@ systemd-random-seed.service systemd-random-seed - Load and save the system random seed at boot and shutdown + Load and save the OS system random seed at boot and shutdown @@ -86,7 +86,9 @@ systemd1, random4, systemd-boot7, - bootctl4 + systemd-stub7, + bootctl4, + systemd-boot-random-seed.service8 diff --git a/units/meson.build b/units/meson.build index 3a1f5229a0..cfc96a9111 100644 --- a/units/meson.build +++ b/units/meson.build @@ -105,7 +105,7 @@ units = [ ['systemd-ask-password-wall.path', '', 'multi-user.target.wants/'], ['systemd-ask-password-wall.service', ''], - ['systemd-boot-system-token.service', 'HAVE_GNU_EFI', + ['systemd-boot-random-seed.service', 'HAVE_GNU_EFI', 'sysinit.target.wants/'], ['systemd-boot-update.service', 'HAVE_GNU_EFI'], ['systemd-coredump.socket', 'ENABLE_COREDUMP', diff --git a/units/systemd-boot-random-seed.service b/units/systemd-boot-random-seed.service index ef5577549e..4fa286071d 100644 --- a/units/systemd-boot-random-seed.service +++ b/units/systemd-boot-random-seed.service @@ -8,22 +8,21 @@ # (at your option) any later version. [Unit] -Description=Store a System Token in an EFI Variable -Documentation=man:systemd-boot-system-token.service(8) +Description=Update Boot Loader Random Seed +Documentation=man:systemd-boot-random-seed.service(8) man:random(4) DefaultDependencies=no After=local-fs.target systemd-random-seed.service -Conflicts=shutdown.target initrd-switch-root.target -Before=shutdown.target initrd-switch-root.target +Conflicts=shutdown.target +Before=sysinit.target shutdown.target +ConditionVirtualization=!container +ConditionPathExists=!/etc/initrd-release # Only run this if the boot loader can support random seed initialization. ConditionPathExists=|/sys/firmware/efi/efivars/LoaderFeatures-4a67b082-0a4c-41cf-b6c7-440b29bb8c4f ConditionPathExists=|/sys/firmware/efi/efivars/StubFeatures-4a67b082-0a4c-41cf-b6c7-440b29bb8c4f -# Only run this if there is no system token defined yet -ConditionPathExists=!/sys/firmware/efi/efivars/LoaderSystemToken-4a67b082-0a4c-41cf-b6c7-440b29bb8c4f - [Service] Type=oneshot RemainAfterExit=yes -ExecStart=bootctl random-seed --graceful +ExecStart=bootctl --graceful random-seed diff --git a/units/systemd-boot-update.service b/units/systemd-boot-update.service index 61ff12762a..fe63fde35a 100644 --- a/units/systemd-boot-update.service +++ b/units/systemd-boot-update.service @@ -10,9 +10,10 @@ [Unit] Description=Automatic Boot Loader Update Documentation=man:bootctl(1) + DefaultDependencies=no -Conflicts=shutdown.target After=local-fs.target +Conflicts=shutdown.target Before=sysinit.target shutdown.target systemd-update-done.service [Service] diff --git a/units/systemd-random-seed.service.in b/units/systemd-random-seed.service.in index 1aa9af9710..d57b2d1269 100644 --- a/units/systemd-random-seed.service.in +++ b/units/systemd-random-seed.service.in @@ -8,14 +8,16 @@ # (at your option) any later version. [Unit] -Description=Load/Save Random Seed +Description=Load/Save OS Random Seed Documentation=man:systemd-random-seed.service(8) man:random(4) + DefaultDependencies=no RequiresMountsFor={{RANDOM_SEED}} Conflicts=shutdown.target After=systemd-remount-fs.service Before=first-boot-complete.target shutdown.target Wants=first-boot-complete.target + ConditionVirtualization=!container ConditionPathExists=!/etc/initrd-release