[PATCH 3/3] tpm_tcg2: hash algo optimization
Ilias Apalodimas
ilias.apalodimas at linaro.org
Mon Jul 29 16:09:57 CEST 2024
On Mon, Jul 15, 2024 at 01:33:19PM +0000, Benjamin BARATTE wrote:
> To properly enable code optimization with hash algorithm, all the
> reference of the hash algo should condition to hash enablement.
> It is possible to fine tune the list of hash algorithms based on dTPM
> configuration.
> Therefore if dTPM supports only one bank, on one hash algorithm could be
> selected (TCG PTP specification mention in case of single bank support
> that SHA256 must be support and default value)
Yes, but...
In order to apply this we need a function that *configures* the TPM with
only the supported compiled algorithms. If a TPM is configured
with more than what u-boot supports, there might be security implications
since we will fail to cap all active PCRs. On top of that the EFI TCG
explicitly says that all the active PCR banks needs to be updated when
extending measurements.
Thanks
/Ilias
>
> Signed-off-by: Benjamin BARATTE <benjamin.baratte at st.com>
> ---
>
> include/tpm-v2.h | 8 --------
> lib/efi_loader/Kconfig | 4 ----
> lib/tpm_tcg2.c | 38 ++++++++++++++++++++++++++++++++++++++
> 3 files changed, 38 insertions(+), 12 deletions(-)
>
> diff --git a/include/tpm-v2.h b/include/tpm-v2.h
> index 9848e1fd10..ec3504de44 100644
> --- a/include/tpm-v2.h
> +++ b/include/tpm-v2.h
> @@ -285,38 +285,30 @@ struct digest_info {
>
>
> static const struct digest_info hash_algo_list[] = {
> -#if IS_ENABLED(CONFIG_SHA1)
> {
> "sha1",
> TPM2_ALG_SHA1,
> TCG2_BOOT_HASH_ALG_SHA1,
> TPM2_SHA1_DIGEST_SIZE,
> },
> -#endif
> -#if IS_ENABLED(CONFIG_SHA256)
> {
> "sha256",
> TPM2_ALG_SHA256,
> TCG2_BOOT_HASH_ALG_SHA256,
> TPM2_SHA256_DIGEST_SIZE,
> },
> -#endif
> -#if IS_ENABLED(CONFIG_SHA384)
> {
> "sha384",
> TPM2_ALG_SHA384,
> TCG2_BOOT_HASH_ALG_SHA384,
> TPM2_SHA384_DIGEST_SIZE,
> },
> -#endif
> -#if IS_ENABLED(CONFIG_SHA512)
> {
> "sha512",
> TPM2_ALG_SHA512,
> TCG2_BOOT_HASH_ALG_SHA512,
> TPM2_SHA512_DIGEST_SIZE,
> },
> -#endif
> {
> "sha3_256",
> TPM2_ALG_SHA3_256,
> diff --git a/lib/efi_loader/Kconfig b/lib/efi_loader/Kconfig
> index ee71f41714..512fb710b5 100644
> --- a/lib/efi_loader/Kconfig
> +++ b/lib/efi_loader/Kconfig
> @@ -405,10 +405,6 @@ config EFI_TCG2_PROTOCOL
> bool "EFI_TCG2_PROTOCOL support"
> default y
> depends on TPM_V2
> - select SHA1
> - select SHA256
> - select SHA384
> - select SHA512
> select HASH
> select SMBIOS_PARSER
> help
> diff --git a/lib/tpm_tcg2.c b/lib/tpm_tcg2.c
> index 7f868cc883..66573b838d 100644
> --- a/lib/tpm_tcg2.c
> +++ b/lib/tpm_tcg2.c
> @@ -96,9 +96,15 @@ int tcg2_create_digest(struct udevice *dev, const u8 *input, u32 length,
> struct tpml_digest_values *digest_list)
> {
> u8 final[sizeof(union tpmu_ha)];
> +#if IS_ENABLED(CONFIG_SHA256)
> sha256_context ctx_256;
> +#endif
> +#if IS_ENABLED(CONFIG_SHA384) || IS_ENABLED(CONFIG_SHA512)
> sha512_context ctx_512;
> +#endif
> +#if IS_ENABLED(CONFIG_SHA1)
> sha1_context ctx;
> +#endif
> u32 active;
> size_t i;
> u32 len;
> @@ -114,30 +120,38 @@ int tcg2_create_digest(struct udevice *dev, const u8 *input, u32 length,
> continue;
>
> switch (hash_algo_list[i].hash_alg) {
> +#if IS_ENABLED(CONFIG_SHA1)
> case TPM2_ALG_SHA1:
> sha1_starts(&ctx);
> sha1_update(&ctx, input, length);
> sha1_finish(&ctx, final);
> len = TPM2_SHA1_DIGEST_SIZE;
> break;
> +#endif
> +#if IS_ENABLED(CONFIG_SHA256)
> case TPM2_ALG_SHA256:
> sha256_starts(&ctx_256);
> sha256_update(&ctx_256, input, length);
> sha256_finish(&ctx_256, final);
> len = TPM2_SHA256_DIGEST_SIZE;
> break;
> +#endif
> +#if IS_ENABLED(CONFIG_SHA384)
> case TPM2_ALG_SHA384:
> sha384_starts(&ctx_512);
> sha384_update(&ctx_512, input, length);
> sha384_finish(&ctx_512, final);
> len = TPM2_SHA384_DIGEST_SIZE;
> break;
> +#endif
> +#if IS_ENABLED(CONFIG_SHA512)
> case TPM2_ALG_SHA512:
> sha512_starts(&ctx_512);
> sha512_update(&ctx_512, input, length);
> sha512_finish(&ctx_512, final);
> len = TPM2_SHA512_DIGEST_SIZE;
> break;
> +#endif
> default:
> printf("%s: unsupported algorithm %x\n", __func__,
> hash_algo_list[i].hash_alg);
> @@ -236,10 +250,18 @@ static int tcg2_log_init(struct udevice *dev, struct tcg2_event_log *elog)
> continue;
>
> switch (hash_algo_list[i].hash_alg) {
> +#if IS_ENABLED(CONFIG_SHA1)
> case TPM2_ALG_SHA1:
> +#endif
> +#if IS_ENABLED(CONFIG_SHA256)
> case TPM2_ALG_SHA256:
> +#endif
> +#if IS_ENABLED(CONFIG_SHA384)
> case TPM2_ALG_SHA384:
> +#endif
> +#if IS_ENABLED(CONFIG_SHA512)
> case TPM2_ALG_SHA512:
> +#endif
> count++;
> break;
> default:
> @@ -337,10 +359,18 @@ static int tcg2_replay_eventlog(struct tcg2_event_log *elog,
> algo = get_unaligned_le16(log + pos);
> pos += offsetof(struct tpmt_ha, digest);
> switch (algo) {
> +#if IS_ENABLED(CONFIG_SHA1)
> case TPM2_ALG_SHA1:
> +#endif
> +#if IS_ENABLED(CONFIG_SHA256)
> case TPM2_ALG_SHA256:
> +#endif
> +#if IS_ENABLED(CONFIG_SHA384)
> case TPM2_ALG_SHA384:
> +#endif
> +#if IS_ENABLED(CONFIG_SHA512)
> case TPM2_ALG_SHA512:
> +#endif
> len = tpm2_algorithm_to_len(algo);
> break;
> default:
> @@ -450,10 +480,18 @@ static int tcg2_log_parse(struct udevice *dev, struct tcg2_event_log *elog)
> return 0;
>
> switch (algo) {
> +#if IS_ENABLED(CONFIG_SHA1)
> case TPM2_ALG_SHA1:
> +#endif
> +#if IS_ENABLED(CONFIG_SHA256)
> case TPM2_ALG_SHA256:
> +#endif
> +#if IS_ENABLED(CONFIG_SHA384)
> case TPM2_ALG_SHA384:
> +#endif
> +#if IS_ENABLED(CONFIG_SHA512)
> case TPM2_ALG_SHA512:
> +#endif
> len = get_unaligned_le16(&event->digest_sizes[i].digest_size);
> if (tpm2_algorithm_to_len(algo) != len)
> return 0;
> --
> 2.34.1
>
> ST Restricted
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