On Tue, Dec 20, 2022 at 12:12:56AM +0900, 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.koj...@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 */
s/size == 0/!size
> + *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 */
> --
> 2.17.1
>
Reviewed-by: Ilias Apalodimas <ilias.apalodi...@linaro.org>
