/*
|
* Copyright (C) 2016 The Android Open Source Project
|
*
|
* Permission is hereby granted, free of charge, to any person
|
* obtaining a copy of this software and associated documentation
|
* files (the "Software"), to deal in the Software without
|
* restriction, including without limitation the rights to use, copy,
|
* modify, merge, publish, distribute, sublicense, and/or sell copies
|
* of the Software, and to permit persons to whom the Software is
|
* furnished to do so, subject to the following conditions:
|
*
|
* The above copyright notice and this permission notice shall be
|
* included in all copies or substantial portions of the Software.
|
*
|
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
|
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
|
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
|
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
|
* BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
|
* ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
|
* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
|
* SOFTWARE.
|
*/
|
|
/*
|
#if !defined(AVB_INSIDE_LIBAVB_H) && !defined(AVB_COMPILATION)
|
#error "Never include this file directly, include libavb.h instead."
|
#endif
|
*/
|
|
#ifndef AVB_VBMETA_IMAGE_H_
|
#define AVB_VBMETA_IMAGE_H_
|
|
#include "avb_sysdeps.h"
|
|
#ifdef __cplusplus
|
extern "C" {
|
#endif
|
|
#include "avb_crypto.h"
|
#include "avb_descriptor.h"
|
|
/* Size of the vbmeta image header. */
|
#define AVB_VBMETA_IMAGE_HEADER_SIZE 256
|
|
/* Magic for the vbmeta image header. */
|
#define AVB_MAGIC "AVB0"
|
#define AVB_MAGIC_LEN 4
|
|
/* Maximum size of the release string including the terminating NUL byte. */
|
#define AVB_RELEASE_STRING_SIZE 48
|
|
/* Flags for the vbmeta image.
|
*
|
* AVB_VBMETA_IMAGE_FLAGS_HASHTREE_DISABLED: If this flag is set,
|
* hashtree image verification will be disabled.
|
*
|
* AVB_VBMETA_IMAGE_FLAGS_VERIFICATION_DISABLED: If this flag is set,
|
* verification will be disabled and descriptors will not be parsed.
|
*/
|
typedef enum {
|
AVB_VBMETA_IMAGE_FLAGS_HASHTREE_DISABLED = (1 << 0),
|
AVB_VBMETA_IMAGE_FLAGS_VERIFICATION_DISABLED = (1 << 1)
|
} AvbVBMetaImageFlags;
|
|
/* Binary format for header of the vbmeta image.
|
*
|
* The vbmeta image consists of three blocks:
|
*
|
* +-----------------------------------------+
|
* | Header data - fixed size |
|
* +-----------------------------------------+
|
* | Authentication data - variable size |
|
* +-----------------------------------------+
|
* | Auxiliary data - variable size |
|
* +-----------------------------------------+
|
*
|
* The "Header data" block is described by this struct and is always
|
* |AVB_VBMETA_IMAGE_HEADER_SIZE| bytes long.
|
*
|
* The "Authentication data" block is |authentication_data_block_size|
|
* bytes long and contains the hash and signature used to authenticate
|
* the vbmeta image. The type of the hash and signature is defined by
|
* the |algorithm_type| field.
|
*
|
* The "Auxiliary data" is |auxiliary_data_block_size| bytes long and
|
* contains the auxiliary data including the public key used to make
|
* the signature and descriptors.
|
*
|
* The public key is at offset |public_key_offset| with size
|
* |public_key_size| in this block. The size of the public key data is
|
* defined by the |algorithm_type| field. The format of the public key
|
* data is described in the |AvbRSAPublicKeyHeader| struct.
|
*
|
* The descriptors starts at |descriptors_offset| from the beginning
|
* of the "Auxiliary Data" block and take up |descriptors_size|
|
* bytes. Each descriptor is stored as a |AvbDescriptor| with tag and
|
* number of bytes following. The number of descriptors can be
|
* determined by walking this data until |descriptors_size| is
|
* exhausted.
|
*
|
* The size of each of the "Authentication data" and "Auxiliary data"
|
* blocks must be divisible by 64. This is to ensure proper alignment.
|
*
|
* Descriptors are free-form blocks stored in a part of the vbmeta
|
* image subject to the same integrity checks as the rest of the
|
* image. See the documentation for |AvbDescriptor| for well-known
|
* descriptors. See avb_descriptor_foreach() for a convenience
|
* function to iterate over descriptors.
|
*
|
* This struct is versioned, see the |required_libavb_version_major|
|
* and |required_libavb_version_minor| fields. This represents the
|
* minimum version of libavb required to verify the header and depends
|
* on the features (e.g. algorithms, descriptors) used. Note that this
|
* may be 1.0 even if generated by an avbtool from 1.4 but where no
|
* features introduced after 1.0 has been used. See the "Versioning
|
* and compatibility" section in the README.md file for more details.
|
*
|
* All fields are stored in network byte order when serialized. To
|
* generate a copy with fields swapped to native byte order, use the
|
* function avb_vbmeta_image_header_to_host_byte_order().
|
*
|
* Before reading and/or using any of this data, you MUST verify it
|
* using avb_vbmeta_image_verify() and reject it unless it's signed by
|
* a known good public key.
|
*/
|
typedef struct AvbVBMetaImageHeader {
|
/* 0: Four bytes equal to "AVB0" (AVB_MAGIC). */
|
uint8_t magic[AVB_MAGIC_LEN];
|
|
/* 4: The major version of libavb required for this header. */
|
uint32_t required_libavb_version_major;
|
/* 8: The minor version of libavb required for this header. */
|
uint32_t required_libavb_version_minor;
|
|
/* 12: The size of the signature block. */
|
uint64_t authentication_data_block_size;
|
/* 20: The size of the auxiliary data block. */
|
uint64_t auxiliary_data_block_size;
|
|
/* 28: The verification algorithm used, see |AvbAlgorithmType| enum. */
|
uint32_t algorithm_type;
|
|
/* 32: Offset into the "Authentication data" block of hash data. */
|
uint64_t hash_offset;
|
/* 40: Length of the hash data. */
|
uint64_t hash_size;
|
|
/* 48: Offset into the "Authentication data" block of signature data. */
|
uint64_t signature_offset;
|
/* 56: Length of the signature data. */
|
uint64_t signature_size;
|
|
/* 64: Offset into the "Auxiliary data" block of public key data. */
|
uint64_t public_key_offset;
|
/* 72: Length of the public key data. */
|
uint64_t public_key_size;
|
|
/* 80: Offset into the "Auxiliary data" block of public key metadata. */
|
uint64_t public_key_metadata_offset;
|
/* 88: Length of the public key metadata. Must be set to zero if there
|
* is no public key metadata.
|
*/
|
uint64_t public_key_metadata_size;
|
|
/* 96: Offset into the "Auxiliary data" block of descriptor data. */
|
uint64_t descriptors_offset;
|
/* 104: Length of descriptor data. */
|
uint64_t descriptors_size;
|
|
/* 112: The rollback index which can be used to prevent rollback to
|
* older versions.
|
*/
|
uint64_t rollback_index;
|
|
/* 120: Flags from the AvbVBMetaImageFlags enumeration. This must be
|
* set to zero if the vbmeta image is not a top-level image.
|
*/
|
uint32_t flags;
|
|
/* 124: Reserved to ensure |release_string| start on a 16-byte
|
* boundary. Must be set to zeroes.
|
*/
|
uint8_t reserved0[4];
|
|
/* 128: The release string from avbtool, e.g. "avbtool 1.0.0" or
|
* "avbtool 1.0.0 xyz_board Git-234abde89". Is guaranteed to be NUL
|
* terminated. Applications must not make assumptions about how this
|
* string is formatted.
|
*/
|
uint8_t release_string[AVB_RELEASE_STRING_SIZE];
|
|
/* 176: Padding to ensure struct is size AVB_VBMETA_IMAGE_HEADER_SIZE
|
* bytes. This must be set to zeroes.
|
*/
|
uint8_t reserved[80];
|
} AVB_ATTR_PACKED AvbVBMetaImageHeader;
|
|
/* Copies |src| to |dest|, byte-swapping fields in the process.
|
*
|
* Make sure you've verified |src| using avb_vbmeta_image_verify()
|
* before accessing the data and/or using this function.
|
*/
|
void avb_vbmeta_image_header_to_host_byte_order(const AvbVBMetaImageHeader* src,
|
AvbVBMetaImageHeader* dest);
|
|
/* Return codes used in avb_vbmeta_image_verify().
|
*
|
* AVB_VBMETA_VERIFY_RESULT_OK is returned if the vbmeta image header
|
* is valid, the hash is correct and the signature is correct. Keep in
|
* mind that you still need to check that you know the public key used
|
* to sign the image, see avb_vbmeta_image_verify() for details.
|
*
|
* AVB_VBMETA_VERIFY_RESULT_OK_NOT_SIGNED is returned if the vbmeta
|
* image header is valid but there is no signature or hash.
|
*
|
* AVB_VBMETA_VERIFY_RESULT_INVALID_VBMETA_HEADER is returned if the
|
* header of the vbmeta image is invalid, for example, invalid magic
|
* or inconsistent data.
|
*
|
* AVB_VBMETA_VERIFY_RESULT_UNSUPPORTED_VERSION is returned if a) the
|
* vbmeta image requires a minimum version of libavb which exceeds the
|
* version of libavb used; or b) the vbmeta image major version
|
* differs from the major version of libavb in use.
|
*
|
* AVB_VBMETA_VERIFY_RESULT_HASH_MISMATCH is returned if the hash
|
* stored in the "Authentication data" block does not match the
|
* calculated hash.
|
*
|
* AVB_VBMETA_VERIFY_RESULT_SIGNATURE_MISMATCH is returned if the
|
* signature stored in the "Authentication data" block is invalid or
|
* doesn't match the public key stored in the vbmeta image.
|
*/
|
typedef enum {
|
AVB_VBMETA_VERIFY_RESULT_OK,
|
AVB_VBMETA_VERIFY_RESULT_OK_NOT_SIGNED,
|
AVB_VBMETA_VERIFY_RESULT_INVALID_VBMETA_HEADER,
|
AVB_VBMETA_VERIFY_RESULT_UNSUPPORTED_VERSION,
|
AVB_VBMETA_VERIFY_RESULT_HASH_MISMATCH,
|
AVB_VBMETA_VERIFY_RESULT_SIGNATURE_MISMATCH,
|
} AvbVBMetaVerifyResult;
|
|
/* Get a textual representation of |result|. */
|
const char* avb_vbmeta_verify_result_to_string(AvbVBMetaVerifyResult result);
|
|
/* Checks that vbmeta image at |data| of size |length| is a valid
|
* vbmeta image. The complete contents of the vbmeta image must be
|
* passed in. It's fine if |length| is bigger than the actual image,
|
* typically callers of this function will load the entire contents of
|
* the 'vbmeta_a' or 'vbmeta_b' partition and pass in its length (for
|
* example, 1 MiB).
|
*
|
* See the |AvbVBMetaImageHeader| struct for information about the
|
* three blocks (header, authentication, auxiliary) that make up a
|
* vbmeta image.
|
*
|
* If the function returns |AVB_VBMETA_VERIFY_RESULT_OK| and
|
* |out_public_key_data| is non-NULL, it will be set to point inside
|
* |data| for where the serialized public key data is stored and
|
* |out_public_key_length|, if non-NULL, will be set to the length of
|
* the public key data. If there is no public key in the metadata then
|
* |out_public_key_data| is set to NULL.
|
*
|
* See the |AvbVBMetaVerifyResult| enum for possible return values.
|
*
|
* VERY IMPORTANT:
|
*
|
* 1. Even if |AVB_VBMETA_VERIFY_RESULT_OK| is returned, you still
|
* need to check that the public key embedded in the image
|
* matches a known key! You can use 'avbtool extract_public_key'
|
* to extract the key (at build time, then store it along your
|
* code) and compare it to what is returned in
|
* |out_public_key_data|.
|
*
|
* 2. You need to check the |rollback_index| field against a stored
|
* value in NVRAM and reject the vbmeta image if the value in
|
* NVRAM is bigger than |rollback_index|. You must also update
|
* the value stored in NVRAM to the smallest value of
|
* |rollback_index| field from boot images in all bootable and
|
* authentic slots marked as GOOD.
|
*
|
* This is a low-level function to only verify the vbmeta data - you
|
* are likely looking for avb_slot_verify() instead for verifying
|
* integrity data for a whole set of partitions.
|
*/
|
AvbVBMetaVerifyResult avb_vbmeta_image_verify(
|
const uint8_t* data,
|
size_t length,
|
const uint8_t** out_public_key_data,
|
size_t* out_public_key_length) AVB_ATTR_WARN_UNUSED_RESULT;
|
|
#ifdef __cplusplus
|
}
|
#endif
|
|
#endif /* AVB_VBMETA_IMAGE_H_ */
|
