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5
6#include "avb_vbmeta_image.h"
7#include "avb_crypto.h"
8#include "avb_rsa.h"
9#include "avb_sha.h"
10#include "avb_util.h"
11#include "avb_version.h"
12
13AvbVBMetaVerifyResult avb_vbmeta_image_verify(
14 const uint8_t* data,
15 size_t length,
16 const uint8_t** out_public_key_data,
17 size_t* out_public_key_length) {
18 AvbVBMetaVerifyResult ret;
19 AvbVBMetaImageHeader h;
20 uint8_t* computed_hash;
21 const AvbAlgorithmData* algorithm;
22 AvbSHA256Ctx sha256_ctx;
23 AvbSHA512Ctx sha512_ctx;
24 const uint8_t* header_block;
25 const uint8_t* authentication_block;
26 const uint8_t* auxiliary_block;
27 int verification_result;
28
29 ret = AVB_VBMETA_VERIFY_RESULT_INVALID_VBMETA_HEADER;
30
31 if (out_public_key_data != NULL) {
32 *out_public_key_data = NULL;
33 }
34 if (out_public_key_length != NULL) {
35 *out_public_key_length = 0;
36 }
37
38
39 if (avb_safe_memcmp(data, AVB_MAGIC, AVB_MAGIC_LEN) != 0) {
40 avb_error("Magic is incorrect.\n");
41 goto out;
42 }
43
44
45 if (length < sizeof(AvbVBMetaImageHeader)) {
46 avb_error("Length is smaller than header.\n");
47 goto out;
48 }
49 avb_vbmeta_image_header_to_host_byte_order((const AvbVBMetaImageHeader*)data,
50 &h);
51
52
53
54
55 if ((h.required_libavb_version_major != AVB_VERSION_MAJOR) ||
56 (h.required_libavb_version_minor > AVB_VERSION_MINOR)) {
57 avb_error("Mismatch between image version and libavb version.\n");
58 ret = AVB_VBMETA_VERIFY_RESULT_UNSUPPORTED_VERSION;
59 goto out;
60 }
61
62
63 if (h.release_string[AVB_RELEASE_STRING_SIZE - 1] != '\0') {
64 avb_error("Release string does not end with a NUL byte.\n");
65 goto out;
66 }
67
68
69 if ((h.authentication_data_block_size & 0x3f) != 0 ||
70 (h.auxiliary_data_block_size & 0x3f) != 0) {
71 avb_error("Block size is not a multiple of 64.\n");
72 goto out;
73 }
74
75
76 uint64_t block_total = sizeof(AvbVBMetaImageHeader);
77 if (!avb_safe_add_to(&block_total, h.authentication_data_block_size) ||
78 !avb_safe_add_to(&block_total, h.auxiliary_data_block_size)) {
79 avb_error("Overflow while computing size of boot image.\n");
80 goto out;
81 }
82 if (block_total > length) {
83 avb_error("Block sizes add up to more than given length.\n");
84 goto out;
85 }
86
87 uintptr_t data_ptr = (uintptr_t)data;
88
89 if (!avb_safe_add(NULL, (uint64_t)data_ptr, length)) {
90 avb_error("Boot image location and length mismatch.\n");
91 goto out;
92 }
93
94
95 uint64_t hash_end;
96 if (!avb_safe_add(&hash_end, h.hash_offset, h.hash_size) ||
97 hash_end > h.authentication_data_block_size) {
98 avb_error("Hash is not entirely in its block.\n");
99 goto out;
100 }
101 uint64_t signature_end;
102 if (!avb_safe_add(&signature_end, h.signature_offset, h.signature_size) ||
103 signature_end > h.authentication_data_block_size) {
104 avb_error("Signature is not entirely in its block.\n");
105 goto out;
106 }
107
108
109 uint64_t pubkey_end;
110 if (!avb_safe_add(&pubkey_end, h.public_key_offset, h.public_key_size) ||
111 pubkey_end > h.auxiliary_data_block_size) {
112 avb_error("Public key is not entirely in its block.\n");
113 goto out;
114 }
115
116
117
118 if (h.public_key_metadata_size > 0) {
119 uint64_t pubkey_md_end;
120 if (!avb_safe_add(&pubkey_md_end,
121 h.public_key_metadata_offset,
122 h.public_key_metadata_size) ||
123 pubkey_md_end > h.auxiliary_data_block_size) {
124 avb_error("Public key metadata is not entirely in its block.\n");
125 goto out;
126 }
127 }
128
129
130 if (h.algorithm_type == AVB_ALGORITHM_TYPE_NONE) {
131 ret = AVB_VBMETA_VERIFY_RESULT_OK_NOT_SIGNED;
132 goto out;
133 }
134
135
136 algorithm = avb_get_algorithm_data(h.algorithm_type);
137 if (!algorithm) {
138 avb_error("Invalid or unknown algorithm.\n");
139 goto out;
140 }
141
142
143 if (h.hash_size != algorithm->hash_len) {
144 avb_error("Embedded hash has wrong size.\n");
145 goto out;
146 }
147
148
149
150
151
152 header_block = data;
153 authentication_block = header_block + sizeof(AvbVBMetaImageHeader);
154 auxiliary_block = authentication_block + h.authentication_data_block_size;
155
156 switch (h.algorithm_type) {
157
158 case AVB_ALGORITHM_TYPE_SHA256_RSA2048:
159 case AVB_ALGORITHM_TYPE_SHA256_RSA4096:
160 case AVB_ALGORITHM_TYPE_SHA256_RSA8192:
161 avb_sha256_init(&sha256_ctx);
162 avb_sha256_update(
163 &sha256_ctx, header_block, sizeof(AvbVBMetaImageHeader));
164 avb_sha256_update(
165 &sha256_ctx, auxiliary_block, h.auxiliary_data_block_size);
166 computed_hash = avb_sha256_final(&sha256_ctx);
167 break;
168
169 case AVB_ALGORITHM_TYPE_SHA512_RSA2048:
170 case AVB_ALGORITHM_TYPE_SHA512_RSA4096:
171 case AVB_ALGORITHM_TYPE_SHA512_RSA8192:
172 avb_sha512_init(&sha512_ctx);
173 avb_sha512_update(
174 &sha512_ctx, header_block, sizeof(AvbVBMetaImageHeader));
175 avb_sha512_update(
176 &sha512_ctx, auxiliary_block, h.auxiliary_data_block_size);
177 computed_hash = avb_sha512_final(&sha512_ctx);
178 break;
179 default:
180 avb_error("Unknown algorithm.\n");
181 goto out;
182 }
183
184 if (avb_safe_memcmp(authentication_block + h.hash_offset,
185 computed_hash,
186 h.hash_size) != 0) {
187 avb_error("Hash does not match!\n");
188 ret = AVB_VBMETA_VERIFY_RESULT_HASH_MISMATCH;
189 goto out;
190 }
191
192 verification_result =
193 avb_rsa_verify(auxiliary_block + h.public_key_offset,
194 h.public_key_size,
195 authentication_block + h.signature_offset,
196 h.signature_size,
197 authentication_block + h.hash_offset,
198 h.hash_size,
199 algorithm->padding,
200 algorithm->padding_len);
201
202 if (verification_result == 0) {
203 ret = AVB_VBMETA_VERIFY_RESULT_SIGNATURE_MISMATCH;
204 goto out;
205 }
206
207 if (h.public_key_size > 0) {
208 if (out_public_key_data != NULL) {
209 *out_public_key_data = auxiliary_block + h.public_key_offset;
210 }
211 if (out_public_key_length != NULL) {
212 *out_public_key_length = h.public_key_size;
213 }
214 }
215
216 ret = AVB_VBMETA_VERIFY_RESULT_OK;
217
218out:
219 return ret;
220}
221
222void avb_vbmeta_image_header_to_host_byte_order(const AvbVBMetaImageHeader* src,
223 AvbVBMetaImageHeader* dest) {
224 avb_memcpy(dest, src, sizeof(AvbVBMetaImageHeader));
225
226 dest->required_libavb_version_major =
227 avb_be32toh(dest->required_libavb_version_major);
228 dest->required_libavb_version_minor =
229 avb_be32toh(dest->required_libavb_version_minor);
230
231 dest->authentication_data_block_size =
232 avb_be64toh(dest->authentication_data_block_size);
233 dest->auxiliary_data_block_size =
234 avb_be64toh(dest->auxiliary_data_block_size);
235
236 dest->algorithm_type = avb_be32toh(dest->algorithm_type);
237
238 dest->hash_offset = avb_be64toh(dest->hash_offset);
239 dest->hash_size = avb_be64toh(dest->hash_size);
240
241 dest->signature_offset = avb_be64toh(dest->signature_offset);
242 dest->signature_size = avb_be64toh(dest->signature_size);
243
244 dest->public_key_offset = avb_be64toh(dest->public_key_offset);
245 dest->public_key_size = avb_be64toh(dest->public_key_size);
246
247 dest->public_key_metadata_offset =
248 avb_be64toh(dest->public_key_metadata_offset);
249 dest->public_key_metadata_size = avb_be64toh(dest->public_key_metadata_size);
250
251 dest->descriptors_offset = avb_be64toh(dest->descriptors_offset);
252 dest->descriptors_size = avb_be64toh(dest->descriptors_size);
253
254 dest->rollback_index = avb_be64toh(dest->rollback_index);
255 dest->flags = avb_be32toh(dest->flags);
256}
257
258const char* avb_vbmeta_verify_result_to_string(AvbVBMetaVerifyResult result) {
259 const char* ret = NULL;
260
261 switch (result) {
262 case AVB_VBMETA_VERIFY_RESULT_OK:
263 ret = "OK";
264 break;
265 case AVB_VBMETA_VERIFY_RESULT_OK_NOT_SIGNED:
266 ret = "OK_NOT_SIGNED";
267 break;
268 case AVB_VBMETA_VERIFY_RESULT_INVALID_VBMETA_HEADER:
269 ret = "INVALID_VBMETA_HEADER";
270 break;
271 case AVB_VBMETA_VERIFY_RESULT_UNSUPPORTED_VERSION:
272 ret = "UNSUPPORTED_VERSION";
273 break;
274 case AVB_VBMETA_VERIFY_RESULT_HASH_MISMATCH:
275 ret = "HASH_MISMATCH";
276 break;
277 case AVB_VBMETA_VERIFY_RESULT_SIGNATURE_MISMATCH:
278 ret = "SIGNATURE_MISMATCH";
279 break;
280
281 }
282
283 if (ret == NULL) {
284 avb_error("Unknown AvbVBMetaVerifyResult value.\n");
285 ret = "(unknown)";
286 }
287
288 return ret;
289}
290
