avb_property_descriptor.c
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// SPDX-License-Identifier: MIT
/*
* Copyright (C) 2016 The Android Open Source Project
*/
#include "avb_property_descriptor.h"
#include "avb_util.h"
bool avb_property_descriptor_validate_and_byteswap(
const AvbPropertyDescriptor* src, AvbPropertyDescriptor* dest) {
uint64_t expected_size;
avb_memcpy(dest, src, sizeof(AvbPropertyDescriptor));
if (!avb_descriptor_validate_and_byteswap((const AvbDescriptor*)src,
(AvbDescriptor*)dest))
return false;
if (dest->parent_descriptor.tag != AVB_DESCRIPTOR_TAG_PROPERTY) {
avb_error("Invalid tag for property descriptor.\n");
return false;
}
dest->key_num_bytes = avb_be64toh(dest->key_num_bytes);
dest->value_num_bytes = avb_be64toh(dest->value_num_bytes);
/* Check that key and value are fully contained. */
expected_size = sizeof(AvbPropertyDescriptor) - sizeof(AvbDescriptor) + 2;
if (!avb_safe_add_to(&expected_size, dest->key_num_bytes) ||
!avb_safe_add_to(&expected_size, dest->value_num_bytes)) {
avb_error("Overflow while adding up sizes.\n");
return false;
}
if (expected_size > dest->parent_descriptor.num_bytes_following) {
avb_error("Descriptor payload size overflow.\n");
return false;
}
return true;
}
typedef struct {
const char* key;
size_t key_size;
const char* ret_value;
size_t ret_value_size;
} PropertyIteratorData;
static bool property_lookup_desc_foreach(const AvbDescriptor* header,
void* user_data) {
PropertyIteratorData* data = (PropertyIteratorData*)user_data;
AvbPropertyDescriptor prop_desc;
const uint8_t* p;
bool ret = true;
if (header->tag != AVB_DESCRIPTOR_TAG_PROPERTY) {
goto out;
}
if (!avb_property_descriptor_validate_and_byteswap(
(const AvbPropertyDescriptor*)header, &prop_desc)) {
goto out;
}
p = (const uint8_t*)header;
if (p[sizeof(AvbPropertyDescriptor) + prop_desc.key_num_bytes] != 0) {
avb_error("No terminating NUL byte in key.\n");
goto out;
}
if (data->key_size == prop_desc.key_num_bytes) {
if (avb_memcmp(p + sizeof(AvbPropertyDescriptor),
data->key,
data->key_size) == 0) {
data->ret_value = (const char*)(p + sizeof(AvbPropertyDescriptor) +
prop_desc.key_num_bytes + 1);
data->ret_value_size = prop_desc.value_num_bytes;
/* Stop iterating. */
ret = false;
goto out;
}
}
out:
return ret;
}
const char* avb_property_lookup(const uint8_t* image_data,
size_t image_size,
const char* key,
size_t key_size,
size_t* out_value_size) {
PropertyIteratorData data;
if (key_size == 0) {
key_size = avb_strlen(key);
}
data.key = key;
data.key_size = key_size;
if (avb_descriptor_foreach(
image_data, image_size, property_lookup_desc_foreach, &data) == 0) {
if (out_value_size != NULL) {
*out_value_size = data.ret_value_size;
}
return data.ret_value;
}
if (out_value_size != NULL) {
*out_value_size = 0;
}
return NULL;
}
bool avb_property_lookup_uint64(const uint8_t* image_data,
size_t image_size,
const char* key,
size_t key_size,
uint64_t* out_value) {
const char* value;
bool ret = false;
uint64_t parsed_val;
int base;
int n;
value = avb_property_lookup(image_data, image_size, key, key_size, NULL);
if (value == NULL) {
goto out;
}
base = 10;
if (avb_memcmp(value, "0x", 2) == 0) {
base = 16;
value += 2;
}
parsed_val = 0;
for (n = 0; value[n] != '\0'; n++) {
int c = value[n];
int digit;
parsed_val *= base;
if (c >= '0' && c <= '9') {
digit = c - '0';
} else if (base == 16 && c >= 'a' && c <= 'f') {
digit = c - 'a' + 10;
} else if (base == 16 && c >= 'A' && c <= 'F') {
digit = c - 'A' + 10;
} else {
avb_error("Invalid digit.\n");
goto out;
}
parsed_val += digit;
}
ret = true;
if (out_value != NULL) {
*out_value = parsed_val;
}
out:
return ret;
}