Re: [PATCH 3/3] efi_loader: add DeployedMode and AuditMode variable measurement

Hi Heinrich,

On Thu, 16 Sept 2021 at 16:02, Heinrich Schuchardt xypron.glpk@gmx.de wrote:

On 9/15/21 7:15 AM, Masahisa Kojima wrote:

...

This commit adds the DeployedMode and AuditMode variable measurement required in TCG PC Client PFP Spec.

Signed-off-by: Masahisa Kojima masahisa.kojima@linaro.org

lib/efi_loader/efi_tcg2.c | 47 +++++++++++++++++++++++++++++++++++++++ 1 file changed, 47 insertions(+)

diff --git a/lib/efi_loader/efi_tcg2.c b/lib/efi_loader/efi_tcg2.c index 35810615ed..427d6e22b1 100644 --- a/lib/efi_loader/efi_tcg2.c +++ b/lib/efi_loader/efi_tcg2.c @@ -12,6 +12,7 @@ #include <dm.h> #include <efi_loader.h> #include <efi_tcg2.h> +#include <efi_variable.h> #include <log.h> #include <malloc.h> #include <smbios.h> @@ -1828,6 +1829,50 @@ out: return ret; }

+/**

• • tcg2_measure_deployed_audit_mode() - measure deployedmode and auditmode
• • @dev: TPM device
• • Return: status code
• */

+static efi_status_t tcg2_measure_deployed_audit_mode(struct udevice *dev) +{

• u8 deployed_mode;
  

• u8 audit_mode;
  

• efi_uintn_t size;
  

• efi_status_t ret;
  

• u32 pcr_index;
  

• size = sizeof(deployed_mode);
  

• ret = efi_get_variable_int(L"DeployedMode", &efi_global_variable_guid,
  

•                            NULL, &size, &deployed_mode, NULL);
  

• if (ret != EFI_SUCCESS)
  

•         return ret;
  

Why should AuditMode not be measured if DeployedMode does not exist?

TCG spec says that PCR index is different depending on the DeployedMode value.

--- PCR[1] If the system supports UEFI 2.5 or later and DeployedMode is enabled, the following additional variables MUST be measured into PCR[1]: a. The DeployedMode variable value. The Event Type SHALL be EV_EFI_VARIABLE_DRIVER_CONFIG and the Event value shall be the value of the UEFI_VARIABLE data structure. b. The AuditMode variable value. The Event Type SHALL be EV_EFI_VARIABLE_DRIVER_CONFIG and the Event value shall be the value of the UEFI_VARIABLE data structure. ---

--- PCR[7] If the system supports UEFI 2.5 or later and DeployedMode is NOT enabled, the following additional variables MUST be measured into PCR[7]: a. The contents of the AuditMode variable b. The contents of the DeployedMode variable ---

If DeployedMode does not exist, we can not decide which PCR to be extended.

Thanks, Masahisa Kojima

Could we handle these variables in a loop over an array containing dbt and dbr reduce code duplication?

Best regards

Heinrich

...

• pcr_index = (deployed_mode ? 1 : 7);
  

• ret = tcg2_measure_variable(dev, pcr_index,
  

•                             EV_EFI_VARIABLE_DRIVER_CONFIG,
  

•                             L"DeployedMode",
  

•                             &efi_global_variable_guid,
  

•                             size, &deployed_mode);
  

• size = sizeof(audit_mode);
  

• ret = efi_get_variable_int(L"AuditMode", &efi_global_variable_guid,
  

•                            NULL, &size, &audit_mode, NULL);
  

• if (ret != EFI_SUCCESS)
  

•         return ret;
  

• ret = tcg2_measure_variable(dev, pcr_index,
  

•                             EV_EFI_VARIABLE_DRIVER_CONFIG,
  

•                             L"AuditMode",
  

•                             &efi_global_variable_guid,
  

•                             size, &audit_mode);
  

• return ret;
  

+}

• /**
  • tcg2_measure_secure_boot_variable() - measure secure boot variables

@@ -1891,6 +1936,8 @@ static efi_status_t tcg2_measure_secure_boot_variable(struct udevice *dev) free(data); }

• ret = tcg2_measure_deployed_audit_mode(dev);
  

• error: return ret; }