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LoadPin expects the file with trusted verity root digests to be an ASCII file with one digest (hex value) per line. A pinned root could contain files that meet these format requirements, even though the hex values don't represent trusted root digests. Add a new requirement to the file format which consists in the first line containing a fixed string. This prevents attackers from feeding files with an otherwise valid format to LoadPin. Suggested-by: Sarthak Kukreti <sarthakkukreti@chromium.org> Signed-off-by: Matthias Kaehlcke <mka@chromium.org> Signed-off-by: Kees Cook <keescook@chromium.org> Link: https://lore.kernel.org/r/20220906181725.1.I3f51d1bb0014e5a5951be4ad3c5ad7c7ca1dfc32@changeid
42 lines
1.6 KiB
Plaintext
42 lines
1.6 KiB
Plaintext
# SPDX-License-Identifier: GPL-2.0-only
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config SECURITY_LOADPIN
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bool "Pin load of kernel files (modules, fw, etc) to one filesystem"
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depends on SECURITY && BLOCK
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help
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Any files read through the kernel file reading interface
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(kernel modules, firmware, kexec images, security policy)
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can be pinned to the first filesystem used for loading. When
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enabled, any files that come from other filesystems will be
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rejected. This is best used on systems without an initrd that
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have a root filesystem backed by a read-only device such as
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dm-verity or a CDROM.
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config SECURITY_LOADPIN_ENFORCE
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bool "Enforce LoadPin at boot"
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depends on SECURITY_LOADPIN
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help
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If selected, LoadPin will enforce pinning at boot. If not
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selected, it can be enabled at boot with the kernel parameter
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"loadpin.enforce=1".
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config SECURITY_LOADPIN_VERITY
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bool "Allow reading files from certain other filesystems that use dm-verity"
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depends on SECURITY_LOADPIN && DM_VERITY=y && SECURITYFS
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help
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If selected LoadPin can allow reading files from filesystems
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that use dm-verity. LoadPin maintains a list of verity root
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digests it considers trusted. A verity backed filesystem is
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considered trusted if its root digest is found in the list
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of trusted digests.
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The list of trusted verity can be populated through an ioctl
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on the LoadPin securityfs entry 'dm-verity'. The ioctl
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expects a file descriptor of a file with verity digests as
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parameter. The file must be located on the pinned root and
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start with the line:
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# LOADPIN_TRUSTED_VERITY_ROOT_DIGESTS
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This is followed by the verity digests, with one digest per
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line.
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