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coreboot-kgpe-d16/src/include/metadata_hash.h

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cbfs: Add verification for RO CBFS metadata hash 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>
2020-05-07 02:06:35 +02:00
/* SPDX-License-Identifier: GPL-2.0-only */
#ifndef _METADATA_HASH_H_
#define _METADATA_HASH_H_
#include <commonlib/bsd/metadata_hash.h>
decompressor: Add CBFS_VERIFICATION support 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>
2021-04-03 01:31:21 +02:00
/* Return a pointer to the whole anchor. Only used for decompressor builds. */
void *metadata_hash_export_anchor(void);
/* Import a pointer that points to the anchor. Only used for decompressor builds. */
void metadata_hash_import_anchor(void *ptr);
cbfs: Add verification for RO CBFS metadata hash 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>
2020-05-07 02:06:35 +02:00
/* Verify the an FMAP data structure with the FMAP hash that is stored together with the CBFS
metadata hash in the bootblock's metadata hash anchor (when CBFS verification is enabled). */
vb2_error_t metadata_hash_verify_fmap(const void *fmap_base, size_t fmap_size);
#if CONFIG(CBFS_VERIFICATION)
/* Get the (RO) CBFS metadata hash for this CBFS image, which forms the root of trust for CBFS
verification. This function is only available in the bootblock. */
struct vb2_hash *metadata_hash_get(void);
#else
static inline struct vb2_hash *metadata_hash_get(void) { return NULL; }
#endif
#endif
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