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- /* SPDX-License-Identifier: MIT */
- /*
- * Copyright (C) 2016 The Android Open Source Project
- */
- #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_ */
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