1 // SPDX-License-Identifier: MIT
2 /*
3 * Copyright (C) 2016 The Android Open Source Project
4 */
5
6 #include "avb_descriptor.h"
7 #include "avb_util.h"
8 #include "avb_vbmeta_image.h"
9
avb_descriptor_validate_and_byteswap(const AvbDescriptor * src,AvbDescriptor * dest)10 bool avb_descriptor_validate_and_byteswap(const AvbDescriptor* src,
11 AvbDescriptor* dest) {
12 dest->tag = avb_be64toh(src->tag);
13 dest->num_bytes_following = avb_be64toh(src->num_bytes_following);
14
15 if ((dest->num_bytes_following & 0x07) != 0) {
16 avb_error("Descriptor size is not divisible by 8.\n");
17 return false;
18 }
19 return true;
20 }
21
avb_descriptor_foreach(const uint8_t * image_data,size_t image_size,AvbDescriptorForeachFunc foreach_func,void * user_data)22 bool avb_descriptor_foreach(const uint8_t* image_data,
23 size_t image_size,
24 AvbDescriptorForeachFunc foreach_func,
25 void* user_data) {
26 const AvbVBMetaImageHeader* header = NULL;
27 bool ret = false;
28 const uint8_t* image_end;
29 const uint8_t* desc_start;
30 const uint8_t* desc_end;
31 const uint8_t* p;
32
33 if (image_data == NULL) {
34 avb_error("image_data is NULL\n.");
35 goto out;
36 }
37
38 if (foreach_func == NULL) {
39 avb_error("foreach_func is NULL\n.");
40 goto out;
41 }
42
43 if (image_size < sizeof(AvbVBMetaImageHeader)) {
44 avb_error("Length is smaller than header.\n");
45 goto out;
46 }
47
48 /* Ensure magic is correct. */
49 if (avb_memcmp(image_data, AVB_MAGIC, AVB_MAGIC_LEN) != 0) {
50 avb_error("Magic is incorrect.\n");
51 goto out;
52 }
53
54 /* Careful, not byteswapped - also ensure it's aligned properly. */
55 avb_assert_aligned(image_data);
56 header = (const AvbVBMetaImageHeader*)image_data;
57 image_end = image_data + image_size;
58
59 desc_start = image_data + sizeof(AvbVBMetaImageHeader) +
60 avb_be64toh(header->authentication_data_block_size) +
61 avb_be64toh(header->descriptors_offset);
62
63 desc_end = desc_start + avb_be64toh(header->descriptors_size);
64
65 if (desc_start < image_data || desc_start > image_end ||
66 desc_end < image_data || desc_end > image_end || desc_end < desc_start) {
67 avb_error("Descriptors not inside passed-in data.\n");
68 goto out;
69 }
70
71 for (p = desc_start; p < desc_end;) {
72 const AvbDescriptor* dh = (const AvbDescriptor*)p;
73 avb_assert_aligned(dh);
74 uint64_t nb_following = avb_be64toh(dh->num_bytes_following);
75 uint64_t nb_total = sizeof(AvbDescriptor) + nb_following;
76
77 if ((nb_total & 7) != 0) {
78 avb_error("Invalid descriptor length.\n");
79 goto out;
80 }
81
82 if (nb_total + p < desc_start || nb_total + p > desc_end) {
83 avb_error("Invalid data in descriptors array.\n");
84 goto out;
85 }
86
87 if (foreach_func(dh, user_data) == 0) {
88 goto out;
89 }
90
91 p += nb_total;
92 }
93
94 ret = true;
95
96 out:
97 return ret;
98 }
99
count_descriptors(const AvbDescriptor * descriptor,void * user_data)100 static bool count_descriptors(const AvbDescriptor* descriptor,
101 void* user_data) {
102 size_t* num_descriptors = user_data;
103 *num_descriptors += 1;
104 return true;
105 }
106
107 typedef struct {
108 size_t descriptor_number;
109 const AvbDescriptor** descriptors;
110 } SetDescriptorData;
111
set_descriptors(const AvbDescriptor * descriptor,void * user_data)112 static bool set_descriptors(const AvbDescriptor* descriptor, void* user_data) {
113 SetDescriptorData* data = user_data;
114 data->descriptors[data->descriptor_number++] = descriptor;
115 return true;
116 }
117
avb_descriptor_get_all(const uint8_t * image_data,size_t image_size,size_t * out_num_descriptors)118 const AvbDescriptor** avb_descriptor_get_all(const uint8_t* image_data,
119 size_t image_size,
120 size_t* out_num_descriptors) {
121 size_t num_descriptors = 0;
122 SetDescriptorData data;
123
124 avb_descriptor_foreach(
125 image_data, image_size, count_descriptors, &num_descriptors);
126
127 data.descriptor_number = 0;
128 data.descriptors =
129 avb_calloc(sizeof(const AvbDescriptor*) * (num_descriptors + 1));
130 if (data.descriptors == NULL) {
131 return NULL;
132 }
133 avb_descriptor_foreach(image_data, image_size, set_descriptors, &data);
134 avb_assert(data.descriptor_number == num_descriptors);
135
136 if (out_num_descriptors != NULL) {
137 *out_num_descriptors = num_descriptors;
138 }
139
140 return data.descriptors;
141 }
142