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 --- 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..bd2671bf8f 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 == 0) /* No payload */ + *null_key = true; + else + *null_key = false; + + return ret; +} + /** * 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 */