On 12/20/22 10:38, Masahisa Kojima wrote:

The signed null key with authenticated header is used to clear the PK, KEK, db and dbx. When CONFIG_EFI_MM_COMM_TEE is enabled (StMM and OP-TEE based RPMB storage is used as the EFI variable storage), clearing KEK, db and dbx by enrolling a signed null key does not work as expected if EFI_VARIABLE_APPEND_WRITE attritube is set.

This commit checks the selected file is null key, then EFI_VARIABLE_APPEND_WRITE attibute will not be used for the null key.

Signed-off-by: Masahisa Kojima masahisa.kojima@linaro.org Reviewed-by: Ilias Apalodimas ilias.apalodimas@linaro.org

---

Changes in v2:

• s/size == 0/!size/

  cmd/eficonfig_sbkey.c | 40 ++++++++++++++++++++++++++++++++++++++-- 1 file changed, 38 insertions(+), 2 deletions(-)

diff --git a/cmd/eficonfig_sbkey.c b/cmd/eficonfig_sbkey.c index 6e0bebf1d4..7fb0467543 100644 --- a/cmd/eficonfig_sbkey.c +++ b/cmd/eficonfig_sbkey.c @@ -72,6 +72,30 @@ static bool file_have_auth_header(void *buf, efi_uintn_t size) return true; }

+/**

• • file_is_null_key() - check the file is an authenticated and signed null key
• • @auth: pointer to the file
• • @size: file size
• • @null_key: pointer to store the result
• • Return: status code
• */

+static efi_status_t file_is_null_key(struct efi_variable_authentication_2 *auth,

• 		     efi_uintn_t size, bool *null_key)
  

+{

• efi_status_t ret = EFI_SUCCESS;
• if (size < (sizeof(auth->time_stamp) + auth->auth_info.hdr.dwLength))

• return EFI_INVALID_PARAMETER;
  

• size -= (sizeof(auth->time_stamp) + auth->auth_info.hdr.dwLength);
• if (!size) /* No payload */

• *null_key = true;
  

• else

• *null_key = false;
  

• return ret;

+}

When merging I will make this:

+static efi_status_t file_is_null_key(struct efi_variable_authentication_2 *auth, + efi_uintn_t size, bool *null_key) +{ + efi_uintn_t auth_size = + sizeof(auth->time_stamp) + auth->auth_info.hdr.dwLength; + + if (size < auth_size) + return EFI_INVALID_PARAMETER; + + *null_key = (size == auth_size); + + return EFI_SUCCESS; +}

Looks easier to read to me.

Reviewed-by: Heinrich Schuchardt heinrich.schuchardt@canonical.com

/**

• eficonfig_process_enroll_key() - enroll key into signature database

@@ -84,6 +108,7 @@ static efi_status_t eficonfig_process_enroll_key(void *data) char *buf = NULL; efi_uintn_t size; efi_status_t ret;

• bool null_key = false; struct efi_file_handle *f = NULL; struct efi_device_path *full_dp = NULL; struct eficonfig_select_file_info file_info;

@@ -149,13 +174,24 @@ static efi_status_t eficonfig_process_enroll_key(void *data) goto out; }

• ret = file_is_null_key((struct efi_variable_authentication_2 *)buf,

• 	       size, &null_key);
  

• if (ret != EFI_SUCCESS) {

• eficonfig_print_msg("ERROR! Invalid file format.");
  

• goto out;
  

• }
• attr = EFI_VARIABLE_NON_VOLATILE | EFI_VARIABLE_BOOTSERVICE_ACCESS | EFI_VARIABLE_RUNTIME_ACCESS | EFI_VARIABLE_TIME_BASED_AUTHENTICATED_WRITE_ACCESS;

• /* PK can enroll only one certificate */
• if (u16_strcmp(data, u"PK")) {

• /*

• * PK can enroll only one certificate.
  

• * The signed null key is used to clear KEK, db and dbx.
  

• * EFI_VARIABLE_APPEND_WRITE attribute must not be set in these cases.
  

• */
  

• if (u16_strcmp(data, u"PK") && !null_key) { efi_uintn_t db_size = 0;

  /* check the variable exists. If exists, add APPEND_WRITE attribute */