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      1 /*
      2  * Copyright (C) 2016 The Android Open Source Project
      3  *
      4  * Permission is hereby granted, free of charge, to any person
      5  * obtaining a copy of this software and associated documentation
      6  * files (the "Software"), to deal in the Software without
      7  * restriction, including without limitation the rights to use, copy,
      8  * modify, merge, publish, distribute, sublicense, and/or sell copies
      9  * of the Software, and to permit persons to whom the Software is
     10  * furnished to do so, subject to the following conditions:
     11  *
     12  * The above copyright notice and this permission notice shall be
     13  * included in all copies or substantial portions of the Software.
     14  *
     15  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
     16  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
     17  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
     18  * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
     19  * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
     20  * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
     21  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
     22  * SOFTWARE.
     23  */
     24 
     25 #if !defined(AVB_INSIDE_LIBAVB_H) && !defined(AVB_COMPILATION)
     26 #error "Never include this file directly, include libavb.h instead."
     27 #endif
     28 
     29 #ifndef AVB_DESCRIPTOR_H_
     30 #define AVB_DESCRIPTOR_H_
     31 
     32 #include "avb_sysdeps.h"
     33 
     34 #ifdef __cplusplus
     35 extern "C" {
     36 #endif
     37 
     38 /* Well-known descriptor tags.
     39  *
     40  * AVB_DESCRIPTOR_TAG_PROPERTY: see |AvbPropertyDescriptor| struct.
     41  * AVB_DESCRIPTOR_TAG_HASHTREE: see |AvbHashtreeDescriptor| struct.
     42  * AVB_DESCRIPTOR_TAG_HASH: see |AvbHashDescriptor| struct.
     43  * AVB_DESCRIPTOR_TAG_KERNEL_CMDLINE: see |AvbKernelCmdlineDescriptor| struct.
     44  * AVB_DESCRIPTOR_TAG_CHAIN_PARTITION: see |AvbChainPartitionDescriptor| struct.
     45  */
     46 typedef enum {
     47   AVB_DESCRIPTOR_TAG_PROPERTY,
     48   AVB_DESCRIPTOR_TAG_HASHTREE,
     49   AVB_DESCRIPTOR_TAG_HASH,
     50   AVB_DESCRIPTOR_TAG_KERNEL_CMDLINE,
     51   AVB_DESCRIPTOR_TAG_CHAIN_PARTITION,
     52 } AvbDescriptorTag;
     53 
     54 /* The header for a serialized descriptor.
     55  *
     56  * A descriptor always have two fields, a |tag| (denoting its type,
     57  * see the |AvbDescriptorTag| enumeration) and the size of the bytes
     58  * following, |num_bytes_following|.
     59  *
     60  * For padding, |num_bytes_following| is always a multiple of 8.
     61  */
     62 typedef struct AvbDescriptor {
     63   uint64_t tag;
     64   uint64_t num_bytes_following;
     65 } AVB_ATTR_PACKED AvbDescriptor;
     66 
     67 /* Copies |src| to |dest| and validates, byte-swapping fields in the
     68  * process if needed. Returns true if valid, false if invalid.
     69  *
     70  * Data following the struct is not validated nor copied.
     71  */
     72 bool avb_descriptor_validate_and_byteswap(
     73     const AvbDescriptor* src, AvbDescriptor* dest) AVB_ATTR_WARN_UNUSED_RESULT;
     74 
     75 /* Signature for callback function used in avb_descriptor_foreach().
     76  * The passed in descriptor is given by |descriptor| and the
     77  * |user_data| passed to avb_descriptor_foreach() function is in
     78  * |user_data|. Return true to continue iterating, false to stop
     79  * iterating.
     80  *
     81  * Note that |descriptor| points into the image passed to
     82  * avb_descriptor_foreach() - all fields need to be byteswapped!
     83  */
     84 typedef bool AvbDescriptorForeachFunc(const AvbDescriptor* descriptor,
     85                                       void* user_data);
     86 
     87 /* Convenience function to iterate over all descriptors in an vbmeta
     88  * image.
     89  *
     90  * The function given by |foreach_func| will be called for each
     91  * descriptor. The given function should return true to continue
     92  * iterating, false to stop.
     93  *
     94  * The |user_data| parameter will be passed to |foreach_func|.
     95  *
     96  * Returns false if the iteration was short-circuited, that is if
     97  * an invocation of |foreach_func| returned false.
     98  *
     99  * Before using this function, you MUST verify |image_data| with
    100  * avb_vbmeta_image_verify() and reject it unless it's signed by a known
    101  * good public key. Additionally, |image_data| must be word-aligned.
    102  */
    103 bool avb_descriptor_foreach(const uint8_t* image_data,
    104                             size_t image_size,
    105                             AvbDescriptorForeachFunc foreach_func,
    106                             void* user_data);
    107 
    108 /* Gets all descriptors in a vbmeta image.
    109  *
    110  * The return value is a NULL-pointer terminated array of
    111  * AvbDescriptor pointers. Free with avb_free() when you are done with
    112  * it. If |out_num_descriptors| is non-NULL, the number of descriptors
    113  * will be returned there.
    114  *
    115  * Note that each AvbDescriptor pointer in the array points into
    116  * |image_data| - all fields need to be byteswapped!
    117  *
    118  * Before using this function, you MUST verify |image_data| with
    119  * avb_vbmeta_image_verify() and reject it unless it's signed by a known
    120  * good public key. Additionally, |image_data| must be word-aligned.
    121  */
    122 const AvbDescriptor** avb_descriptor_get_all(const uint8_t* image_data,
    123                                              size_t image_size,
    124                                              size_t* out_num_descriptors)
    125     AVB_ATTR_WARN_UNUSED_RESULT;
    126 
    127 #ifdef __cplusplus
    128 }
    129 #endif
    130 
    131 #endif /* AVB_DESCRIPTOR_H_ */
    132