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This patch adds a new Kconfig that controls whether CBFS APIs for
unverified areas will allow file decompression when CBFS verification is
enabled. This should be disallowed by default because it exposes the
attack surface of all supported decompression algorithms. Make
allowances for one legacy use case with CONFIG_SOC_INTEL_CSE_LITE_
COMPRESS_ME_RW that should become obsolete with VBOOT_CBFS_INTEGRATION.
Signed-off-by: Julius Werner <jwerner@chromium.org>
Change-Id: Ieae420f51cbc01dae2ab265414219cc9c288087b
Reviewed-on: https://review.coreboot.org/c/coreboot/+/75457
Reviewed-by: Jakub Czapiga <jacz@semihalf.com>
Reviewed-by: Subrata Banik <subratabanik@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Yu-Ping Wu <yupingso@google.com>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
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CBFS verification on boards where VBOOT starts before bootblock eg. PSP
verstage has been accommodated by keeping metadata hash outside the
bootblock. Hence the dependency can be removed.
BUG=b:227809919
TEST=Build and boot to OS in skyrim with CBFS verification enabled using
both x86 verstage and PSP verstage.
Change-Id: I0a3254728a51a8ee7d7782afcea15ea06d93da7d
Signed-off-by: Karthikeyan Ramasubramanian <kramasub@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/66947
Reviewed-by: Julius Werner <jwerner@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Raul Rangel <rrangel@chromium.org>
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See for example Intel document *Secure the Network Infrastructure –
Secure Boot Methodologies* [1].
Change all occurrences with the command below:
$ git grep -l BootGuard | xargs sed -i 's/BootGuard/Boot Guard/g'
[1]: https://builders.intel.com/docs/networkbuilders/secure-the-network-infrastructure-secure-boot-methodologies.pdf
Change-Id: I69fb64b525fb4799bcb9d75624003c0d59b885b5
Signed-off-by: Paul Menzel <pmenzel@molgen.mpg.de>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/60136
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
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With the elimination of remaining non-verifying CBFS APIs in CB:59682,
CBFS verification is now ready to be used in its simplest form, so
enable the respective Kconfig options in menuconfig. Add a few more
restrictions to the TOCTOU_SAFETY option for problems that haven't been
solved yet, and transform a comment in cbfs.c into a die() to make sure
we don't accidentally forget implementing it once vboot integration gets
added.
Signed-off-by: Julius Werner <jwerner@chromium.org>
Change-Id: Ifeba5c962c943856ab79bc6c4cb90a60c1de4a60
Reviewed-on: https://review.coreboot.org/c/coreboot/+/59982
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Jakub Czapiga <jacz@semihalf.com>
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CBFS_VERIFICATION requires the CBFS metadata hash anchor to be linked
into an uncompressed stage, but for platforms using COMPRESS_BOOTBLOCK,
this is only the decompressor stage. The first CBFS accesses are made in
the bootblock stage after decompression, so if we want to make
CBFS_VERIFICATION work on those platforms, we have to pass the metadata
hash anchor from the decompressor into the bootblock. This patch does
just that. (Note that this relies on the decompressor data remaining
valid in memory for as long as the metadata hash anchor is needed. This
is always true even for OVERLAP_DECOMPRESSOR_ROMSTAGE() situations
because the FMAP and CBFS metadata necessarily need to have finished
verification before a new stage could be loaded.)
Signed-off-by: Julius Werner <jwerner@chromium.org>
Change-Id: I2e6d7384cfb8339a24369eb6c01fc12f911c974e
Reviewed-on: https://review.coreboot.org/c/coreboot/+/52085
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
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Change-Id: I9031dad52581e77aa56014b1fede884f2cdeb6de
Signed-off-by: Elyes HAOUAS <ehaouas@noos.fr>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/49882
Reviewed-by: Felix Singer <felixsinger@posteo.net>
Reviewed-by: Nico Huber <nico.h@gmx.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
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This patch addresses the same problem as CB:48429, but hopefully this
time correctly. Since the mcache is not guaranteed to be available on
the first CBFS lookup for some special cases, we can no longer treat it
as a one-time fire-and-forget initialization. Instead, we test
cbd->mcache_size to check if the mcache has been initialized yet, and
keep trying on every lookup if we don't find it the first time.
Since the mcache is a hard requirement for TOCTOU safety, also make it
more clear in Kconfig that configurations known to do CBFS accesses
before CBMEM init are incompatbile with that, and make sure we die()
rather than do something unsafe if there's a case that Kconfig didn't
catch.
Signed-off-by: Julius Werner <jwerner@chromium.org>
Change-Id: I4e01e9a9905f7dcba14eaf05168495201ed5de60
Reviewed-on: https://review.coreboot.org/c/coreboot/+/48482
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-by: Christian Walter <christian.walter@9elements.com>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
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This patch adds the first stage of the new CONFIG_CBFS_VERIFICATION
feature. It's not useful to end-users in this stage so it cannot be
selected in menuconfig (and should not be used other than for
development) yet. With this patch coreboot can verify the metadata hash
of the RO CBFS when it starts booting, but it does not verify individual
files yet. Likewise, verifying RW CBFSes with vboot is not yet
supported.
Verification is bootstrapped from a "metadata hash anchor" structure
that is embedded in the bootblock code and marked by a unique magic
number. This anchor contains both the CBFS metadata hash and a separate
hash for the FMAP which is required to find the primary CBFS. Both are
verified on first use in the bootblock (and halt the system on failure).
The CONFIG_TOCTOU_SAFETY option is also added for illustrative purposes
to show some paths that need to be different when full protection
against TOCTOU (time-of-check vs. time-of-use) attacks is desired. For
normal verification it is sufficient to check the FMAP and the CBFS
metadata hash only once in the bootblock -- for TOCTOU verification we
do the same, but we need to be extra careful that we do not re-read the
FMAP or any CBFS metadata in later stages. This is mostly achieved by
depending on the CBFS metadata cache and FMAP cache features, but we
allow for one edge case in case the RW CBFS metadata cache overflows
(which may happen during an RW update and could otherwise no longer be
fixed because mcache size is defined by RO code). This code is added to
demonstrate design intent but won't really matter until RW CBFS
verification can be supported.
Signed-off-by: Julius Werner <jwerner@chromium.org>
Change-Id: I8930434de55eb938b042fdada9aa90218c0b5a34
Reviewed-on: https://review.coreboot.org/c/coreboot/+/41120
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
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