[PATCH v3 3/6] tpm: add wrapper and helper APIs for PCR allocate
Ilias Apalodimas
ilias.apalodimas at linaro.org
Tue Jan 28 07:54:59 CET 2025
On Mon, 27 Jan 2025 at 16:59, Raymond Mao <raymond.mao at linaro.org> wrote:
>
> Add PCR allocate wrapper APIs for using in tcg2 protocol.
> The wrapper proceeds a PCR allocate command, followed by a
> shutdown command.
> A system boot is required after two commands since TPM device needs
> a HW reset to activate the new algorithms config.
> Also, a helper function is included to determine the new bank mask
> for PCR allocation by combining the status of current active,
> supported and eventlog bank masks.
> A new kconfig is created. PCR allocate and system reboot only
> happens when the kconfig is selected, otherwise just exit with
> errors.
>
> Signed-off-by: Raymond Mao <raymond.mao at linaro.org>
> ---
> changes in v2
> - Rename the newly added APIs.
> changes in v3
> - Rename tpm2_set_algorithm_mask to tpm2_scan_masks.
>
> include/tpm-v2.h | 21 ++++++++
> lib/Kconfig | 12 +++++
> lib/tpm-v2.c | 121 +++++++++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 154 insertions(+)
>
> diff --git a/include/tpm-v2.h b/include/tpm-v2.h
> index af3158f6e4..ece422df0c 100644
> --- a/include/tpm-v2.h
> +++ b/include/tpm-v2.h
> @@ -703,6 +703,18 @@ u32 tpm2_report_state(struct udevice *dev, uint vendor_cmd, uint vendor_subcmd,
> u32 tpm2_enable_nvcommits(struct udevice *dev, uint vendor_cmd,
> uint vendor_subcmd);
>
> +/**
> + * tpm2_scan_masks - Scan the bitmask of algorithms based on the
> + * active/supported banks and the one from eventlog.
> + *
> + * @dev TPM device
> + * @log_active Active algorithm bitmask
> + * @mask Bitmask to set
> + *
> + * Return: zero on success, negative errno otherwise
> + */
> +int tpm2_scan_masks(struct udevice *dev, u32 log_active, u32 *mask);
> +
> /**
> * tpm2_pcr_config_algo() - Allocate the active PCRs. Requires reboot
> *
> @@ -730,6 +742,15 @@ u32 tpm2_pcr_config_algo(struct udevice *dev, u32 algo_mask,
> u32 tpm2_send_pcr_allocate(struct udevice *dev, const char *pw,
> const ssize_t pw_sz, struct tpml_pcr_selection *pcr,
> u32 pcr_len);
> +/**
> + * tpm2_activate_banks() - Activate PCR banks
> + *
> + * @param dev TPM device
> + * @log_active Bitmask of eventlog algorithms
> + *
> + * Return: code of the operation
> + */
> +int tpm2_activate_banks(struct udevice *dev, u32 log_active);
>
> /**
> * tpm2_auto_start() - start up the TPM and perform selftests.
> diff --git a/lib/Kconfig b/lib/Kconfig
> index baeb615626..0732333849 100644
> --- a/lib/Kconfig
> +++ b/lib/Kconfig
> @@ -514,6 +514,18 @@ config VPL_TPM
> for the low-level TPM interface, but only one TPM is supported at
> a time by the TPM library.
>
> +config TPM_PCR_ALLOCATE
> + bool "Re-configurate TPM algorithms in run-time (PCR allocate)"
> + depends on TPM_V2 && (MEASURED_BOOT || EFI_TCG2_PROTOCOL)
> + help
> + This enables a detection for the dismatches of algorithms among TPM
> + device, eventlog from previous boot stage and U-Boot support.
> + A PCR allocate command will be sent to reconfigurate the TPM device
> + in run-time to make sure algorithms in TPM device, eventlog and
> + U-Boot are aligned with each other.
> + A system reboot will be proceeded after then to activate the new
> + algorithms.
> +
> endmenu
>
> menu "Android Verified Boot"
> diff --git a/lib/tpm-v2.c b/lib/tpm-v2.c
> index 045b5dd9eb..aa02a9e961 100644
> --- a/lib/tpm-v2.c
> +++ b/lib/tpm-v2.c
> @@ -44,6 +44,127 @@ static int tpm2_update_active_banks(struct udevice *dev)
> return 0;
> }
>
> +static void tpm2_print_selected_algorithm_name(u32 selected)
> +{
> + size_t i;
> + const char *str;
> +
> + for (i = 0; i < ARRAY_SIZE(hash_algo_list); i++) {
> + const struct digest_info *algo = &hash_algo_list[i];
> +
> + if (!(selected & algo->hash_mask))
> + continue;
> +
> + str = tpm2_algorithm_name(algo->hash_alg);
> + if (str)
> + log_info("%s\n", str);
> + }
> +}
> +
> +int tpm2_scan_masks(struct udevice *dev, u32 log_active, u32 *mask)
> +{
> + struct tpml_pcr_selection pcrs;
> + u32 active = 0;
> + u32 supported = 0;
> + int rc, i;
> +
> + *mask = 0;
> +
> + rc = tpm2_get_pcr_info(dev, &pcrs);
> + if (rc)
> + return rc;
> +
> + for (i = 0; i < pcrs.count; i++) {
> + struct tpms_pcr_selection *sel = &pcrs.selection[i];
> + size_t j;
> + u32 hash_mask = 0;
> +
> + for (j = 0; j < ARRAY_SIZE(hash_algo_list); j++) {
> + if (hash_algo_list[j].hash_alg == sel->hash)
> + hash_mask = hash_algo_list[j].hash_mask;
> + }
> +
> + if (tpm2_algorithm_supported(sel->hash))
> + supported |= hash_mask;
> +
> + if (tpm2_is_active_bank(sel))
> + active |= hash_mask;
> + }
> +
> + /* All eventlog algorithm(s) must be supported */
> + if (log_active & ~supported) {
> + log_err("EventLog contains U-Boot unsupported algorithm(s)\n");
> + tpm2_print_selected_algorithm_name(log_active & ~supported);
> + rc = -1;
> + }
> + if (log_active && active & ~log_active) {
> + log_warning("TPM active algorithm(s) not exist in eventlog\n");
> + tpm2_print_selected_algorithm_name(active & ~log_active);
> + *mask = log_active;
> + }
> +
> + /* Any active algorithm(s) which are not supported must be removed */
> + if (active & ~supported) {
> + log_warning("TPM active algorithm(s) unsupported by u-boot\n");
> + tpm2_print_selected_algorithm_name(active & ~supported);
> + if (*mask)
> + *mask = active & supported & *mask;
> + else
> + *mask = active & supported;
> + }
> +
> + return rc;
> +}
> +
> +static int tpm2_pcr_allocate(struct udevice *dev, u32 algo_mask)
> +{
> + struct tpml_pcr_selection pcr = { 0 };
> + u32 pcr_len = 0;
> + int rc;
> +
> + rc = tpm2_get_pcr_info(dev, &pcr);
> + if (rc)
> + return rc;
> +
> + rc = tpm2_pcr_config_algo(dev, algo_mask, &pcr, &pcr_len);
> + if (rc)
> + return rc;
> +
> + /* Assume no password */
> + rc = tpm2_send_pcr_allocate(dev, NULL, 0, &pcr, pcr_len);
> + if (rc)
> + return rc;
> +
> + /* Send TPM2_Shutdown, assume mode = TPM2_SU_CLEAR */
> + return tpm2_startup(dev, false, TPM2_SU_CLEAR);
> +}
> +
> +int tpm2_activate_banks(struct udevice *dev, u32 log_active)
> +{
> + u32 algo_mask = 0;
> + int rc;
> +
> + rc = tpm2_scan_masks(dev, log_active, &algo_mask);
> + if (rc)
> + return rc;
> +
> + if (algo_mask) {
> + if (!IS_ENABLED(CONFIG_TPM_PCR_ALLOCATE))
> + return -1;
> +
> + rc = tpm2_pcr_allocate(dev, algo_mask);
> + if (rc)
> + return rc;
> +
> + log_info("PCR allocate done, shutdown TPM and reboot\n");
> + do_reset(NULL, 0, 0, NULL);
> + log_err("reset does not work!\n");
> + return -1;
> + }
> +
> + return 0;
> +}
> +
> u32 tpm2_startup(struct udevice *dev, bool bon, enum tpm2_startup_types mode)
> {
> int op = bon ? TPM2_CC_STARTUP : TPM2_CC_SHUTDOWN;
> --
> 2.25.1
>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas at linaro.org>
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