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/* SPDX-License-Identifier: GPL-2.0-only */
#include <security/tpm/tspi.h>
#include <security/vboot/tpm_common.h>
#include <vb2_api.h>
#include <vb2_sha.h>
#define TPM_PCR_BOOT_MODE "VBOOT: boot mode"
#define TPM_PCR_GBB_HWID_NAME "VBOOT: GBB HWID"
#define TPM_PCR_MINIMUM_DIGEST_SIZE 20
uint32_t vboot_setup_tpm(struct vb2_context *ctx)
{
uint32_t rc;
rc = tpm_setup(ctx->flags & VB2_CONTEXT_S3_RESUME);
if (rc == TPM_CB_MUST_REBOOT)
ctx->flags |= VB2_CONTEXT_SECDATA_WANTS_REBOOT;
return rc;
}
vb2_error_t vboot_extend_pcr(struct vb2_context *ctx, int pcr,
enum vb2_pcr_digest which_digest)
{
uint8_t buffer[VB2_PCR_DIGEST_RECOMMENDED_SIZE];
uint32_t size = sizeof(buffer);
vb2_error_t rv;
rv = vb2api_get_pcr_digest(ctx, which_digest, buffer, &size);
if (rv != VB2_SUCCESS)
return rv;
/*
* On TPM 1.2, all PCRs are intended for use with SHA1. We truncate our
* SHA256 HWID hash to 20 bytes to make it fit. On TPM 2.0, we always
* want to use the SHA256 banks, even for the boot mode which is
* technically a SHA1 value for historical reasons. vboot has already
* zero-extended the buffer to 32 bytes for us, so we just take it like
* that and pretend it's a SHA256. In practice, this means we never care
* about the (*size) value returned from vboot (which indicates how many
* significant bytes vboot wrote, although it always extends zeroes up
* to the end of the buffer), we always use a hardcoded size instead.
*/
_Static_assert(sizeof(buffer) >= VB2_SHA256_DIGEST_SIZE,
"Buffer needs to be able to fit at least a SHA256");
enum vb2_hash_algorithm algo = CONFIG(TPM1) ? VB2_HASH_SHA1 : VB2_HASH_SHA256;
switch (which_digest) {
/* SHA1 of (devmode|recmode|keyblock) bits */
case BOOT_MODE_PCR:
return tpm_extend_pcr(pcr, algo, buffer, vb2_digest_size(algo),
TPM_PCR_BOOT_MODE);
/* SHA256 of HWID */
case HWID_DIGEST_PCR:
return tpm_extend_pcr(pcr, algo, buffer, vb2_digest_size(algo),
TPM_PCR_GBB_HWID_NAME);
default:
return VB2_ERROR_UNKNOWN;
}
}
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