path: root/libavb/avb_descriptor.c (plain)
blob: 4f8e92534e5aecab0af9ef1e90b53fcdcd74d215

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
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
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
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
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
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