290 lines
9.2 KiB
C
290 lines
9.2 KiB
C
// SPDX-License-Identifier: MIT
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/*
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* Copyright (C) 2016 The Android Open Source Project
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*/
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#include "avb_vbmeta_image.h"
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#include "avb_crypto.h"
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#include "avb_rsa.h"
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#include "avb_sha.h"
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#include "avb_util.h"
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#include "avb_version.h"
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AvbVBMetaVerifyResult avb_vbmeta_image_verify(
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const uint8_t* data,
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size_t length,
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const uint8_t** out_public_key_data,
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size_t* out_public_key_length) {
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AvbVBMetaVerifyResult ret;
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AvbVBMetaImageHeader h;
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uint8_t* computed_hash;
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const AvbAlgorithmData* algorithm;
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AvbSHA256Ctx sha256_ctx;
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AvbSHA512Ctx sha512_ctx;
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const uint8_t* header_block;
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const uint8_t* authentication_block;
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const uint8_t* auxiliary_block;
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int verification_result;
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ret = AVB_VBMETA_VERIFY_RESULT_INVALID_VBMETA_HEADER;
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if (out_public_key_data != NULL) {
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*out_public_key_data = NULL;
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}
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if (out_public_key_length != NULL) {
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*out_public_key_length = 0;
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}
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/* Ensure magic is correct. */
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if (avb_safe_memcmp(data, AVB_MAGIC, AVB_MAGIC_LEN) != 0) {
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avb_error("Magic is incorrect.\n");
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goto out;
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}
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/* Before we byteswap, ensure length is long enough. */
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if (length < sizeof(AvbVBMetaImageHeader)) {
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avb_error("Length is smaller than header.\n");
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goto out;
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}
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avb_vbmeta_image_header_to_host_byte_order((const AvbVBMetaImageHeader*)data,
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&h);
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/* Ensure we don't attempt to access any fields if we do not meet
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* the specified minimum version of libavb.
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*/
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if ((h.required_libavb_version_major != AVB_VERSION_MAJOR) ||
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(h.required_libavb_version_minor > AVB_VERSION_MINOR)) {
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avb_error("Mismatch between image version and libavb version.\n");
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ret = AVB_VBMETA_VERIFY_RESULT_UNSUPPORTED_VERSION;
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goto out;
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}
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/* Ensure |release_string| ends with a NUL byte. */
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if (h.release_string[AVB_RELEASE_STRING_SIZE - 1] != '\0') {
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avb_error("Release string does not end with a NUL byte.\n");
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goto out;
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}
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/* Ensure inner block sizes are multiple of 64. */
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if ((h.authentication_data_block_size & 0x3f) != 0 ||
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(h.auxiliary_data_block_size & 0x3f) != 0) {
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avb_error("Block size is not a multiple of 64.\n");
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goto out;
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}
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/* Ensure block sizes all add up to at most |length|. */
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uint64_t block_total = sizeof(AvbVBMetaImageHeader);
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if (!avb_safe_add_to(&block_total, h.authentication_data_block_size) ||
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!avb_safe_add_to(&block_total, h.auxiliary_data_block_size)) {
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avb_error("Overflow while computing size of boot image.\n");
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goto out;
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}
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if (block_total > length) {
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avb_error("Block sizes add up to more than given length.\n");
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goto out;
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}
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uintptr_t data_ptr = (uintptr_t)data;
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/* Ensure passed in memory doesn't wrap. */
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if (!avb_safe_add(NULL, (uint64_t)data_ptr, length)) {
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avb_error("Boot image location and length mismatch.\n");
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goto out;
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}
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/* Ensure hash and signature are entirely in the Authentication data block. */
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uint64_t hash_end;
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if (!avb_safe_add(&hash_end, h.hash_offset, h.hash_size) ||
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hash_end > h.authentication_data_block_size) {
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avb_error("Hash is not entirely in its block.\n");
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goto out;
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}
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uint64_t signature_end;
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if (!avb_safe_add(&signature_end, h.signature_offset, h.signature_size) ||
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signature_end > h.authentication_data_block_size) {
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avb_error("Signature is not entirely in its block.\n");
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goto out;
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}
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/* Ensure public key is entirely in the Auxiliary data block. */
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uint64_t pubkey_end;
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if (!avb_safe_add(&pubkey_end, h.public_key_offset, h.public_key_size) ||
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pubkey_end > h.auxiliary_data_block_size) {
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avb_error("Public key is not entirely in its block.\n");
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goto out;
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}
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/* Ensure public key metadata (if set) is entirely in the Auxiliary
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* data block. */
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if (h.public_key_metadata_size > 0) {
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uint64_t pubkey_md_end;
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if (!avb_safe_add(&pubkey_md_end,
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h.public_key_metadata_offset,
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h.public_key_metadata_size) ||
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pubkey_md_end > h.auxiliary_data_block_size) {
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avb_error("Public key metadata is not entirely in its block.\n");
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goto out;
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}
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}
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/* Bail early if there's no hash or signature. */
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if (h.algorithm_type == AVB_ALGORITHM_TYPE_NONE) {
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ret = AVB_VBMETA_VERIFY_RESULT_OK_NOT_SIGNED;
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goto out;
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}
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/* Ensure algorithm field is supported. */
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algorithm = avb_get_algorithm_data(h.algorithm_type);
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if (!algorithm) {
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avb_error("Invalid or unknown algorithm.\n");
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goto out;
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}
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/* Bail if the embedded hash size doesn't match the chosen algorithm. */
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if (h.hash_size != algorithm->hash_len) {
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avb_error("Embedded hash has wrong size.\n");
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goto out;
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}
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/* No overflow checks needed from here-on after since all block
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* sizes and offsets have been verified above.
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*/
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header_block = data;
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authentication_block = header_block + sizeof(AvbVBMetaImageHeader);
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auxiliary_block = authentication_block + h.authentication_data_block_size;
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switch (h.algorithm_type) {
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/* Explicit fall-through: */
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case AVB_ALGORITHM_TYPE_SHA256_RSA2048:
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case AVB_ALGORITHM_TYPE_SHA256_RSA4096:
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case AVB_ALGORITHM_TYPE_SHA256_RSA8192:
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avb_sha256_init(&sha256_ctx);
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avb_sha256_update(
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&sha256_ctx, header_block, sizeof(AvbVBMetaImageHeader));
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avb_sha256_update(
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&sha256_ctx, auxiliary_block, h.auxiliary_data_block_size);
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computed_hash = avb_sha256_final(&sha256_ctx);
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break;
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/* Explicit fall-through: */
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case AVB_ALGORITHM_TYPE_SHA512_RSA2048:
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case AVB_ALGORITHM_TYPE_SHA512_RSA4096:
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case AVB_ALGORITHM_TYPE_SHA512_RSA8192:
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avb_sha512_init(&sha512_ctx);
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avb_sha512_update(
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&sha512_ctx, header_block, sizeof(AvbVBMetaImageHeader));
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avb_sha512_update(
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&sha512_ctx, auxiliary_block, h.auxiliary_data_block_size);
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computed_hash = avb_sha512_final(&sha512_ctx);
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break;
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default:
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avb_error("Unknown algorithm.\n");
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goto out;
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}
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if (avb_safe_memcmp(authentication_block + h.hash_offset,
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computed_hash,
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h.hash_size) != 0) {
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avb_error("Hash does not match!\n");
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ret = AVB_VBMETA_VERIFY_RESULT_HASH_MISMATCH;
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goto out;
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}
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verification_result =
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avb_rsa_verify(auxiliary_block + h.public_key_offset,
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h.public_key_size,
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authentication_block + h.signature_offset,
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h.signature_size,
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authentication_block + h.hash_offset,
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h.hash_size,
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algorithm->padding,
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algorithm->padding_len);
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if (verification_result == 0) {
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ret = AVB_VBMETA_VERIFY_RESULT_SIGNATURE_MISMATCH;
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goto out;
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}
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if (h.public_key_size > 0) {
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if (out_public_key_data != NULL) {
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*out_public_key_data = auxiliary_block + h.public_key_offset;
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}
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if (out_public_key_length != NULL) {
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*out_public_key_length = h.public_key_size;
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}
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}
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ret = AVB_VBMETA_VERIFY_RESULT_OK;
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out:
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return ret;
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}
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void avb_vbmeta_image_header_to_host_byte_order(const AvbVBMetaImageHeader* src,
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AvbVBMetaImageHeader* dest) {
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avb_memcpy(dest, src, sizeof(AvbVBMetaImageHeader));
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dest->required_libavb_version_major =
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avb_be32toh(dest->required_libavb_version_major);
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dest->required_libavb_version_minor =
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avb_be32toh(dest->required_libavb_version_minor);
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dest->authentication_data_block_size =
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avb_be64toh(dest->authentication_data_block_size);
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dest->auxiliary_data_block_size =
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avb_be64toh(dest->auxiliary_data_block_size);
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dest->algorithm_type = avb_be32toh(dest->algorithm_type);
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dest->hash_offset = avb_be64toh(dest->hash_offset);
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dest->hash_size = avb_be64toh(dest->hash_size);
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dest->signature_offset = avb_be64toh(dest->signature_offset);
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dest->signature_size = avb_be64toh(dest->signature_size);
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dest->public_key_offset = avb_be64toh(dest->public_key_offset);
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dest->public_key_size = avb_be64toh(dest->public_key_size);
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dest->public_key_metadata_offset =
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avb_be64toh(dest->public_key_metadata_offset);
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dest->public_key_metadata_size = avb_be64toh(dest->public_key_metadata_size);
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dest->descriptors_offset = avb_be64toh(dest->descriptors_offset);
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dest->descriptors_size = avb_be64toh(dest->descriptors_size);
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dest->rollback_index = avb_be64toh(dest->rollback_index);
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dest->flags = avb_be32toh(dest->flags);
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}
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const char* avb_vbmeta_verify_result_to_string(AvbVBMetaVerifyResult result) {
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const char* ret = NULL;
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switch (result) {
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case AVB_VBMETA_VERIFY_RESULT_OK:
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ret = "OK";
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break;
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case AVB_VBMETA_VERIFY_RESULT_OK_NOT_SIGNED:
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ret = "OK_NOT_SIGNED";
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break;
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case AVB_VBMETA_VERIFY_RESULT_INVALID_VBMETA_HEADER:
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ret = "INVALID_VBMETA_HEADER";
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break;
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case AVB_VBMETA_VERIFY_RESULT_UNSUPPORTED_VERSION:
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ret = "UNSUPPORTED_VERSION";
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break;
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case AVB_VBMETA_VERIFY_RESULT_HASH_MISMATCH:
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ret = "HASH_MISMATCH";
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break;
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case AVB_VBMETA_VERIFY_RESULT_SIGNATURE_MISMATCH:
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ret = "SIGNATURE_MISMATCH";
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break;
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/* Do not add a 'default:' case here because of -Wswitch. */
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}
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if (ret == NULL) {
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avb_error("Unknown AvbVBMetaVerifyResult value.\n");
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ret = "(unknown)";
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}
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return ret;
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}
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