diff options
| author | Julius Werner <jwerner@chromium.org> | 2023-05-25 18:26:32 -0700 |
|---|---|---|
| committer | Lean Sheng Tan <sheng.tan@9elements.com> | 2023-06-19 12:27:15 +0000 |
| commit | 6e303aa89b906dc12b0bbf6024a23de339634eb1 (patch) | |
| tree | 13c7fed064b5e00eed7a81744439619006fdff48 /src/lib | |
| parent | 3f1e034835fc40b43b95746b37b291de8c860810 (diff) | |
cbfs: Allow controlling decompression of unverified files
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>
Diffstat (limited to 'src/lib')
| -rw-r--r-- | src/lib/Kconfig.cbfs_verification | 14 | ||||
| -rw-r--r-- | src/lib/cbfs.c | 7 |
2 files changed, 21 insertions, 0 deletions
diff --git a/src/lib/Kconfig.cbfs_verification b/src/lib/Kconfig.cbfs_verification index 9b053e1c16..12aaf81fab 100644 --- a/src/lib/Kconfig.cbfs_verification +++ b/src/lib/Kconfig.cbfs_verification @@ -37,6 +37,20 @@ config TOCTOU_SAFETY bootblock is also safe against these vulnerabilities (i.e. there's no point in enabling this when you just rely on flash write-protection). +config CBFS_ALLOW_UNVERIFIED_DECOMPRESSION + bool "Run decompression algorithms on potentially untrusted code" + default n + help + This controls whether cbfs_unverified_area_...() access functions may + decompress files. This exposes the attack surface of all supported + decompression algorithms. Even if you don't compress the files you are + planning to load with these functions, since file metadata is also + unverified, an attacker can potentially replace them with compressed + files to access a vulnerability in the decompression code. + + If you don't need to load compressed files from unverified areas, say + no here for tighter security. + config CBFS_HASH_ALGO int default 1 if CBFS_HASH_SHA1 diff --git a/src/lib/cbfs.c b/src/lib/cbfs.c index 4e25d27cfb..78eeb3bfb2 100644 --- a/src/lib/cbfs.c +++ b/src/lib/cbfs.c @@ -208,6 +208,13 @@ static size_t cbfs_load_and_decompress(const struct region_device *rdev, void *b DEBUG("Decompressing %zu bytes from '%s' to %p with algo %d\n", in_size, mdata->h.filename, buffer, compression); + if (CONFIG(CBFS_VERIFICATION) && !CONFIG(CBFS_ALLOW_UNVERIFIED_DECOMPRESSION) && + skip_verification && compression != CBFS_COMPRESS_NONE) { + ERROR("Refusing to decompress unverified file '%s' with algo %d\n", + mdata->h.filename, compression); + return 0; + } + switch (compression) { case CBFS_COMPRESS_NONE: if (buffer_size < in_size) |