[PATCH 1/1] efi_loader: validate load option

AKASHI Takahiro
2020-06-03T02:25:41Z

Heinrich,

On Sun, May 31, 2020 at 10:52:16PM +0200, Heinrich Schuchardt wrote:
> For passing the optional data of the load option to the loaded imaged
> protocol we need its size.
>
> efi_deserialize_load_option() is changed to return the size of the optional
> data.
>
> As a by-product we get a partial validation of the load option.
> Checking the length of the device path remains to be implemented.
>
> Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>

Please add "Reported-by: Coverity (CID xxx)" for tracing
as you requested me before.
(even if it doesn't fully address the issue.)

Reported-by: Coverity (CID 303760)
Reported-by: Coverity (CID 303768)
Reported-by: Coverity (CID 303776)

-Takahiro Akashi

> ---
> cmd/efidebug.c | 21 +++++++++++-----
> include/efi_loader.h | 3 ++-
> lib/efi_loader/efi_bootmgr.c | 48 +++++++++++++++++++++++++++++-------
> 3 files changed, 56 insertions(+), 16 deletions(-)
>
> diff --git a/cmd/efidebug.c b/cmd/efidebug.c
> index 32430e62f0..58018f700c 100644
> --- a/cmd/efidebug.c
> +++ b/cmd/efidebug.c
> @@ -694,14 +694,19 @@ static int do_efi_boot_rm(struct cmd_tbl *cmdtp, int flag,
> *
> * Decode the value of UEFI load option variable and print information.
> */
> -static void show_efi_boot_opt_data(u16 *varname16, void *data, size_t size)
> +static void show_efi_boot_opt_data(u16 *varname16, void *data, size_t *size)
> {
> struct efi_load_option lo;
> char *label, *p;
> size_t label_len16, label_len;
> u16 *dp_str;
> + efi_status_t ret;
>
> - efi_deserialize_load_option(&lo, data);
> + ret = efi_deserialize_load_option(&lo, data, size);
> + if (ret != EFI_SUCCESS) {
> + printf("%ls: invalid load option\n", varname16);
> + return;
> + }
>
> label_len16 = u16_strlen(lo.label);
> label_len = utf16_utf8_strnlen(lo.label, label_len16);
> @@ -728,8 +733,7 @@ static void show_efi_boot_opt_data(u16 *varname16, void *data, size_t size)
>
> printf(" data:\n");
> print_hex_dump(" ", DUMP_PREFIX_OFFSET, 16, 1,
> - lo.optional_data, size + (u8 *)data -
> - (u8 *)lo.optional_data, true);
> + lo.optional_data, *size, true);
> free(label);
> }
>
> @@ -759,7 +763,7 @@ static void show_efi_boot_opt(u16 *varname16)
> &efi_global_variable_guid,
> NULL, &size, data));
> if (ret == EFI_SUCCESS)
> - show_efi_boot_opt_data(varname16, data, size);
> + show_efi_boot_opt_data(varname16, data, &size);
> free(data);
> }
> }
> @@ -920,7 +924,12 @@ static int show_efi_boot_order(void)
> goto out;
> }
>
> - efi_deserialize_load_option(&lo, data);
> + ret = efi_deserialize_load_option(&lo, data, &size);
> + if (ret != EFI_SUCCESS) {
> + printf("%ls: invalid load option\n", var_name16);
> + ret = CMD_RET_FAILURE;
> + goto out;
> + }
>
> label_len16 = u16_strlen(lo.label);
> label_len = utf16_utf8_strnlen(lo.label, label_len16);
> diff --git a/include/efi_loader.h b/include/efi_loader.h
> index 9533df26dc..c2cae814b6 100644
> --- a/include/efi_loader.h
> +++ b/include/efi_loader.h
> @@ -708,7 +708,8 @@ struct efi_load_option {
> const u8 *optional_data;
> };
>
> -void efi_deserialize_load_option(struct efi_load_option *lo, u8 *data);
> +efi_status_t efi_deserialize_load_option(struct efi_load_option *lo, u8 *data,
> + efi_uintn_t *size);
> unsigned long efi_serialize_load_option(struct efi_load_option *lo, u8 **data);
> efi_status_t efi_bootmgr_load(efi_handle_t *handle);
>
> diff --git a/lib/efi_loader/efi_bootmgr.c b/lib/efi_loader/efi_bootmgr.c
> index fa65445c12..e268e9c4b8 100644
> --- a/lib/efi_loader/efi_bootmgr.c
> +++ b/lib/efi_loader/efi_bootmgr.c
> @@ -38,24 +38,50 @@ static const struct efi_runtime_services *rs;
> *
> * @lo: pointer to target
> * @data: serialized data
> + * @size: size of the load option, on return size of the optional data
> + * Return: status code
> */
> -void efi_deserialize_load_option(struct efi_load_option *lo, u8 *data)
> +efi_status_t efi_deserialize_load_option(struct efi_load_option *lo, u8 *data,
> + efi_uintn_t *size)
> {
> + efi_uintn_t len;
> +
> + len = sizeof(u32);
> + if (*size < len + 2 * sizeof(u16))
> + return EFI_INVALID_PARAMETER;
> lo->attributes = get_unaligned_le32(data);
> - data += sizeof(u32);
> + data += len;
> + *size -= len;
>
> + len = sizeof(u16);
> lo->file_path_length = get_unaligned_le16(data);
> - data += sizeof(u16);
> + data += len;
> + *size -= len;
>
> - /* FIXME */
> lo->label = (u16 *)data;
> - data += (u16_strlen(lo->label) + 1) * sizeof(u16);
> -
> - /* FIXME */
> + len = u16_strnlen(lo->label, *size / sizeof(u16) - 1);
> + if (lo->label[len])
> + return EFI_INVALID_PARAMETER;
> + len = (len + 1) * sizeof(u16);
> + if (*size < len)
> + return EFI_INVALID_PARAMETER;
> + data += len;
> + *size -= len;
> +
> + len = lo->file_path_length;
> + if (*size < len)
> + return EFI_INVALID_PARAMETER;
> lo->file_path = (struct efi_device_path *)data;
> - data += lo->file_path_length;
> + /*
> + * TODO: validate device path. There should be an end node within
> + * the indicated file_path_length.
> + */
> + data += len;
> + *size -= len;
>
> lo->optional_data = data;
> +
> + return EFI_SUCCESS;
> }
>
> /**
> @@ -170,7 +196,11 @@ static efi_status_t try_load_entry(u16 n, efi_handle_t *handle)
> if (!load_option)
> return EFI_LOAD_ERROR;
>
> - efi_deserialize_load_option(&lo, load_option);
> + ret = efi_deserialize_load_option(&lo, load_option, &size);
> + if (ret != EFI_SUCCESS) {
> + log_warning("Invalid load option for %ls\n", varname);
> + goto error;
> + }
>
> if (lo.attributes & LOAD_OPTION_ACTIVE) {
> u32 attributes;
> --
> 2.26.2
>