| /* SPDX-License-Identifier: GPL-2.0-only */ |
| |
| #include <security/tpm/tspi.h> |
| #include <vb2_api.h> |
| #include <security/vboot/tpm_common.h> |
| |
| #define TPM_PCR_BOOT_MODE "VBOOT: boot mode" |
| #define TPM_PCR_GBB_HWID_NAME "VBOOT: GBB HWID" |
| |
| uint32_t vboot_setup_tpm(struct vb2_context *ctx) |
| { |
| uint32_t result; |
| |
| result = tpm_setup(ctx->flags & VB2_CONTEXT_S3_RESUME); |
| if (result == TPM_E_MUST_REBOOT) |
| ctx->flags |= VB2_CONTEXT_SECDATA_WANTS_REBOOT; |
| |
| return result; |
| } |
| |
| 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; |
| if (size < TPM_PCR_MINIMUM_DIGEST_SIZE) |
| return VB2_ERROR_UNKNOWN; |
| |
| /* |
| * 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; |
| } |
| } |