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 #include "avb_descriptor.h"
26 #include "avb_util.h"
27 #include "avb_vbmeta_image.h"
28 
avb_descriptor_validate_and_byteswap(const AvbDescriptor * src,AvbDescriptor * dest)29 bool avb_descriptor_validate_and_byteswap(const AvbDescriptor* src,
30                                           AvbDescriptor* dest) {
31   dest->tag = avb_be64toh(src->tag);
32   dest->num_bytes_following = avb_be64toh(src->num_bytes_following);
33 
34   if ((dest->num_bytes_following & 0x07) != 0) {
35     avb_error("Descriptor size is not divisible by 8.\n");
36     return false;
37   }
38   return true;
39 }
40 
avb_descriptor_foreach(const uint8_t * image_data,size_t image_size,AvbDescriptorForeachFunc foreach_func,void * user_data)41 bool avb_descriptor_foreach(const uint8_t* image_data,
42                             size_t image_size,
43                             AvbDescriptorForeachFunc foreach_func,
44                             void* user_data) {
45   const AvbVBMetaImageHeader* header = NULL;
46   bool ret = false;
47   const uint8_t* image_end;
48   const uint8_t* desc_start;
49   const uint8_t* desc_end;
50   const uint8_t* p;
51 
52   if (image_data == NULL) {
53     avb_error("image_data is NULL\n.");
54     goto out;
55   }
56 
57   if (foreach_func == NULL) {
58     avb_error("foreach_func is NULL\n.");
59     goto out;
60   }
61 
62   if (image_size < sizeof(AvbVBMetaImageHeader)) {
63     avb_error("Length is smaller than header.\n");
64     goto out;
65   }
66 
67   /* Ensure magic is correct. */
68   if (avb_memcmp(image_data, AVB_MAGIC, AVB_MAGIC_LEN) != 0) {
69     avb_error("Magic is incorrect.\n");
70     goto out;
71   }
72 
73   /* Careful, not byteswapped - also ensure it's aligned properly. */
74   avb_assert_aligned(image_data);
75   header = (const AvbVBMetaImageHeader*)image_data;
76   image_end = image_data + image_size;
77 
78   desc_start = image_data + sizeof(AvbVBMetaImageHeader) +
79                avb_be64toh(header->authentication_data_block_size) +
80                avb_be64toh(header->descriptors_offset);
81 
82   desc_end = desc_start + avb_be64toh(header->descriptors_size);
83 
84   if (desc_start < image_data || desc_start > image_end ||
85       desc_end < image_data || desc_end > image_end || desc_end < desc_start) {
86     avb_error("Descriptors not inside passed-in data.\n");
87     goto out;
88   }
89 
90   for (p = desc_start; p < desc_end;) {
91     const AvbDescriptor* dh = (const AvbDescriptor*)p;
92     avb_assert_aligned(dh);
93     uint64_t nb_following = avb_be64toh(dh->num_bytes_following);
94     uint64_t nb_total = sizeof(AvbDescriptor) + nb_following;
95 
96     if ((nb_total & 7) != 0) {
97       avb_error("Invalid descriptor length.\n");
98       goto out;
99     }
100 
101     if (nb_total + p < desc_start || nb_total + p > desc_end) {
102       avb_error("Invalid data in descriptors array.\n");
103       goto out;
104     }
105 
106     if (foreach_func(dh, user_data) == 0) {
107       goto out;
108     }
109 
110     p += nb_total;
111   }
112 
113   ret = true;
114 
115 out:
116   return ret;
117 }
118 
count_descriptors(const AvbDescriptor * descriptor,void * user_data)119 static bool count_descriptors(const AvbDescriptor* descriptor,
120                               void* user_data) {
121   size_t* num_descriptors = user_data;
122   *num_descriptors += 1;
123   return true;
124 }
125 
126 typedef struct {
127   size_t descriptor_number;
128   const AvbDescriptor** descriptors;
129 } SetDescriptorData;
130 
set_descriptors(const AvbDescriptor * descriptor,void * user_data)131 static bool set_descriptors(const AvbDescriptor* descriptor, void* user_data) {
132   SetDescriptorData* data = user_data;
133   data->descriptors[data->descriptor_number++] = descriptor;
134   return true;
135 }
136 
avb_descriptor_get_all(const uint8_t * image_data,size_t image_size,size_t * out_num_descriptors)137 const AvbDescriptor** avb_descriptor_get_all(const uint8_t* image_data,
138                                              size_t image_size,
139                                              size_t* out_num_descriptors) {
140   size_t num_descriptors = 0;
141   SetDescriptorData data;
142 
143   avb_descriptor_foreach(
144       image_data, image_size, count_descriptors, &num_descriptors);
145 
146   data.descriptor_number = 0;
147   data.descriptors =
148       avb_calloc(sizeof(const AvbDescriptor*) * (num_descriptors + 1));
149   if (data.descriptors == NULL) {
150     return NULL;
151   }
152   avb_descriptor_foreach(image_data, image_size, set_descriptors, &data);
153   avb_assert(data.descriptor_number == num_descriptors);
154 
155   if (out_num_descriptors != NULL) {
156     *out_num_descriptors = num_descriptors;
157   }
158 
159   return data.descriptors;
160 }
161