avb_descriptor.c
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// SPDX-License-Identifier: MIT
/*
* Copyright (C) 2016 The Android Open Source Project
*/
#include "avb_descriptor.h"
#include "avb_util.h"
#include "avb_vbmeta_image.h"
bool avb_descriptor_validate_and_byteswap(const AvbDescriptor* src,
AvbDescriptor* dest) {
dest->tag = avb_be64toh(src->tag);
dest->num_bytes_following = avb_be64toh(src->num_bytes_following);
if ((dest->num_bytes_following & 0x07) != 0) {
avb_error("Descriptor size is not divisible by 8.\n");
return false;
}
return true;
}
bool avb_descriptor_foreach(const uint8_t* image_data,
size_t image_size,
AvbDescriptorForeachFunc foreach_func,
void* user_data) {
const AvbVBMetaImageHeader* header = NULL;
bool ret = false;
const uint8_t* image_end;
const uint8_t* desc_start;
const uint8_t* desc_end;
const uint8_t* p;
if (image_data == NULL) {
avb_error("image_data is NULL\n.");
goto out;
}
if (foreach_func == NULL) {
avb_error("foreach_func is NULL\n.");
goto out;
}
if (image_size < sizeof(AvbVBMetaImageHeader)) {
avb_error("Length is smaller than header.\n");
goto out;
}
/* Ensure magic is correct. */
if (avb_memcmp(image_data, AVB_MAGIC, AVB_MAGIC_LEN) != 0) {
avb_error("Magic is incorrect.\n");
goto out;
}
/* Careful, not byteswapped - also ensure it's aligned properly. */
avb_assert_aligned(image_data);
header = (const AvbVBMetaImageHeader*)image_data;
image_end = image_data + image_size;
desc_start = image_data + sizeof(AvbVBMetaImageHeader) +
avb_be64toh(header->authentication_data_block_size) +
avb_be64toh(header->descriptors_offset);
desc_end = desc_start + avb_be64toh(header->descriptors_size);
if (desc_start < image_data || desc_start > image_end ||
desc_end < image_data || desc_end > image_end || desc_end < desc_start) {
avb_error("Descriptors not inside passed-in data.\n");
goto out;
}
for (p = desc_start; p < desc_end;) {
const AvbDescriptor* dh = (const AvbDescriptor*)p;
avb_assert_aligned(dh);
uint64_t nb_following = avb_be64toh(dh->num_bytes_following);
uint64_t nb_total = sizeof(AvbDescriptor) + nb_following;
if ((nb_total & 7) != 0) {
avb_error("Invalid descriptor length.\n");
goto out;
}
if (nb_total + p < desc_start || nb_total + p > desc_end) {
avb_error("Invalid data in descriptors array.\n");
goto out;
}
if (foreach_func(dh, user_data) == 0) {
goto out;
}
p += nb_total;
}
ret = true;
out:
return ret;
}
static bool count_descriptors(const AvbDescriptor* descriptor,
void* user_data) {
size_t* num_descriptors = user_data;
*num_descriptors += 1;
return true;
}
typedef struct {
size_t descriptor_number;
const AvbDescriptor** descriptors;
} SetDescriptorData;
static bool set_descriptors(const AvbDescriptor* descriptor, void* user_data) {
SetDescriptorData* data = user_data;
data->descriptors[data->descriptor_number++] = descriptor;
return true;
}
const AvbDescriptor** avb_descriptor_get_all(const uint8_t* image_data,
size_t image_size,
size_t* out_num_descriptors) {
size_t num_descriptors = 0;
SetDescriptorData data;
avb_descriptor_foreach(
image_data, image_size, count_descriptors, &num_descriptors);
data.descriptor_number = 0;
data.descriptors =
avb_calloc(sizeof(const AvbDescriptor*) * (num_descriptors + 1));
if (data.descriptors == NULL) {
return NULL;
}
avb_descriptor_foreach(image_data, image_size, set_descriptors, &data);
avb_assert(data.descriptor_number == num_descriptors);
if (out_num_descriptors != NULL) {
*out_num_descriptors = num_descriptors;
}
return data.descriptors;
}