summaryrefslogtreecommitdiff
path: root/lib/libavb/avb_descriptor.c
blob: 86b8d1b99430e74841224674a95761016a8d863b (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
// 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"
#include <malloc.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 = 0;
    if (!avb_safe_add(&nb_total, sizeof(AvbDescriptor), nb_following)) {
      avb_error("Invalid descriptor length.\n");
      goto out;
    }

    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;
    }

    if (!avb_safe_add_to((uint64_t*)(&p), nb_total)) {
      avb_error("Invalid descriptor length.\n");
      goto out;
    }
  }

  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;
}