libavb/avb_property_descriptor.h

/*
 * Copyright (C) 2016 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#if !defined(AVB_INSIDE_LIBAVB_H) && !defined(AVB_COMPILATION)
#error "Never include this file directly, include libavb.h instead."
#endif

#ifndef AVB_PROPERTY_DESCRIPTOR_H_
#define AVB_PROPERTY_DESCRIPTOR_H_

#include "avb_descriptor.h"

#ifdef __cplusplus
extern "C" {
#endif

/* A descriptor for properties (free-form key/value pairs).
 *
 * Following this struct are |key_num_bytes| bytes of key data,
 * followed by a NUL byte, then |value_num_bytes| bytes of value data,
 * followed by a NUL byte and then enough padding to make the combined
 * size a multiple of 8.
 */
typedef struct AvbPropertyDescriptor {
  AvbDescriptor parent_descriptor;
  uint64_t key_num_bytes;
  uint64_t value_num_bytes;
} AVB_ATTR_PACKED AvbPropertyDescriptor;

/* Copies |src| to |dest| and validates, byte-swapping fields in the
 * process if needed. Returns true if valid, false if invalid.
 *
 * Data following the struct is not validated nor copied.
 */
bool avb_property_descriptor_validate_and_byteswap(
    const AvbPropertyDescriptor* src,
    AvbPropertyDescriptor* dest) AVB_ATTR_WARN_UNUSED_RESULT;

/* Convenience function for looking up the value for a property with
 * name |key| in a vbmeta image. If |key_size| is 0, |key| must be
 * NUL-terminated.
 *
 * The |image_data| parameter must be a pointer to a vbmeta image of
 * size |image_size|.
 *
 * This function returns a pointer to the value inside the passed-in
 * image or NULL if not found. Note that the value is always
 * guaranteed to be followed by a NUL byte.
 *
 * If the value was found and |out_value_size| is not NULL, the size
 * of the value is returned there.
 *
 * This function is O(n) in number of descriptors so if you need to
 * look up a lot of values, you may want to build a more efficient
 * lookup-table by manually walking all descriptors using
 * avb_descriptor_foreach().
 *
 * Before using this function, you MUST verify |image_data| with
 * avb_vbmeta_image_verify() and reject it unless it's signed by a
 * known good public key.
 */
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) AVB_ATTR_WARN_UNUSED_RESULT;

/* Like avb_property_lookup() but parses the intial portions of the
 * value as an unsigned 64-bit integer. Both decimal and hexadecimal
 * representations (e.g. "0x2a") are supported. Returns false on
 * failure and true on success. On success, the parsed value is
 * returned in |out_value|.
 */
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) AVB_ATTR_WARN_UNUSED_RESULT;

#ifdef __cplusplus
}
#endif

#endif /* AVB_PROPERTY_DESCRIPTOR_H_ */