aboutsummaryrefslogtreecommitdiff
path: root/boot/image-fit-sig.c
blob: 12369896fe3f614b5dedbec793a54831562a5d1c (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
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
// SPDX-License-Identifier: GPL-2.0+
/*
 * Copyright (c) 2013, Google Inc.
 */

#ifdef USE_HOSTCC
#include "mkimage.h"
#include <time.h>
#else
#include <common.h>
#include <log.h>
#include <malloc.h>
#include <asm/global_data.h>
DECLARE_GLOBAL_DATA_PTR;
#endif /* !USE_HOSTCC*/
#include <fdt_region.h>
#include <image.h>
#include <u-boot/rsa.h>
#include <u-boot/hash-checksum.h>

#define IMAGE_MAX_HASHED_NODES		100

/**
 * fit_region_make_list() - Make a list of image regions
 *
 * Given a list of fdt_regions, create a list of image_regions. This is a
 * simple conversion routine since the FDT and image code use different
 * structures.
 *
 * @fit: FIT image
 * @fdt_regions: Pointer to FDT regions
 * @count: Number of FDT regions
 * @region: Pointer to image regions, which must hold @count records. If
 * region is NULL, then (except for an SPL build) the array will be
 * allocated.
 * @return: Pointer to image regions
 */
struct image_region *fit_region_make_list(const void *fit,
					  struct fdt_region *fdt_regions,
					  int count,
					  struct image_region *region)
{
	int i;

	debug("Hash regions:\n");
	debug("%10s %10s\n", "Offset", "Size");

	/*
	 * Use malloc() except in SPL (to save code size). In SPL the caller
	 * must allocate the array.
	 */
	if (!IS_ENABLED(CONFIG_SPL_BUILD) && !region)
		region = calloc(sizeof(*region), count);
	if (!region)
		return NULL;
	for (i = 0; i < count; i++) {
		debug("%10x %10x\n", fdt_regions[i].offset,
		      fdt_regions[i].size);
		region[i].data = fit + fdt_regions[i].offset;
		region[i].size = fdt_regions[i].size;
	}

	return region;
}

static int fit_image_setup_verify(struct image_sign_info *info,
				  const void *fit, int noffset,
				  const void *key_blob, int required_keynode,
				  char **err_msgp)
{
	const char *algo_name;
	const char *padding_name;

	if (fdt_totalsize(fit) > CONFIG_VAL(FIT_SIGNATURE_MAX_SIZE)) {
		*err_msgp = "Total size too large";
		return 1;
	}
	if (fit_image_hash_get_algo(fit, noffset, &algo_name)) {
		*err_msgp = "Can't get hash algo property";
		return -1;
	}

	padding_name = fdt_getprop(fit, noffset, "padding", NULL);
	if (!padding_name)
		padding_name = RSA_DEFAULT_PADDING_NAME;

	memset(info, '\0', sizeof(*info));
	info->keyname = fdt_getprop(fit, noffset, FIT_KEY_HINT, NULL);
	info->fit = fit;
	info->node_offset = noffset;
	info->name = algo_name;
	info->checksum = image_get_checksum_algo(algo_name);
	info->crypto = image_get_crypto_algo(algo_name);
	info->padding = image_get_padding_algo(padding_name);
	info->fdt_blob = key_blob;
	info->required_keynode = required_keynode;
	printf("%s:%s", algo_name, info->keyname);

	if (!info->checksum || !info->crypto || !info->padding) {
		*err_msgp = "Unknown signature algorithm";
		return -1;
	}

	return 0;
}

int fit_image_check_sig(const void *fit, int noffset, const void *data,
			size_t size, const void *key_blob, int required_keynode,
			char **err_msgp)
{
	struct image_sign_info info;
	struct image_region region;
	uint8_t *fit_value;
	int fit_value_len;

	*err_msgp = NULL;
	if (fit_image_setup_verify(&info, fit, noffset, key_blob,
				   required_keynode, err_msgp))
		return -1;

	if (fit_image_hash_get_value(fit, noffset, &fit_value,
				     &fit_value_len)) {
		*err_msgp = "Can't get hash value property";
		return -1;
	}

	region.data = data;
	region.size = size;

	if (info.crypto->verify(&info, &region, 1, fit_value, fit_value_len)) {
		*err_msgp = "Verification failed";
		return -1;
	}

	return 0;
}

static int fit_image_verify_sig(const void *fit, int image_noffset,
				const char *data, size_t size,
				const void *key_blob, int key_offset)
{
	int noffset;
	char *err_msg = "";
	int verified = 0;
	int ret;

	/* Process all hash subnodes of the component image node */
	fdt_for_each_subnode(noffset, fit, image_noffset) {
		const char *name = fit_get_name(fit, noffset, NULL);

		/*
		 * We don't support this since libfdt considers names with the
		 * name root but different @ suffix to be equal
		 */
		if (strchr(name, '@')) {
			err_msg = "Node name contains @";
			goto error;
		}
		if (!strncmp(name, FIT_SIG_NODENAME,
			     strlen(FIT_SIG_NODENAME))) {
			ret = fit_image_check_sig(fit, noffset, data, size,
						  key_blob, -1, &err_msg);
			if (ret) {
				puts("- ");
			} else {
				puts("+ ");
				verified = 1;
				break;
			}
		}
	}

	if (noffset == -FDT_ERR_TRUNCATED || noffset == -FDT_ERR_BADSTRUCTURE) {
		err_msg = "Corrupted or truncated tree";
		goto error;
	}

	return verified ? 0 : -EPERM;

error:
	printf(" error!\n%s for '%s' hash node in '%s' image node\n",
	       err_msg, fit_get_name(fit, noffset, NULL),
	       fit_get_name(fit, image_noffset, NULL));
	return -1;
}

int fit_image_verify_required_sigs(const void *fit, int image_noffset,
				   const char *data, size_t size,
				   const void *key_blob, int *no_sigsp)
{
	int verify_count = 0;
	int noffset;
	int key_node;

	/* Work out what we need to verify */
	*no_sigsp = 1;
	key_node = fdt_subnode_offset(key_blob, 0, FIT_SIG_NODENAME);
	if (key_node < 0) {
		debug("%s: No signature node found: %s\n", __func__,
		      fdt_strerror(key_node));
		return 0;
	}

	fdt_for_each_subnode(noffset, key_blob, key_node) {
		const char *required;
		int ret;

		required = fdt_getprop(key_blob, noffset, FIT_KEY_REQUIRED,
				       NULL);
		if (!required || strcmp(required, "image"))
			continue;
		ret = fit_image_verify_sig(fit, image_noffset, data, size,
					   key_blob, noffset);
		if (ret) {
			printf("Failed to verify required signature '%s'\n",
			       fit_get_name(key_blob, noffset, NULL));
			return ret;
		}
		verify_count++;
	}

	if (verify_count)
		*no_sigsp = 0;

	return 0;
}

/**
 * fit_config_check_sig() - Check the signature of a config
 *
 * Here we are looking at a particular signature that needs verification (here
 * signature-1):
 *
 *	configurations {
 *		default = "conf-1";
 *		conf-1 {
 *			kernel = "kernel-1";
 *			fdt = "fdt-1";
 *			signature-1 {
 *				algo = "sha1,rsa2048";
 *				value = <...conf 1 signature...>;
 *			};
 *		};
 *
 * @fit: FIT to check
 * @noffset: Offset of the signature node being checked (e.g.
 *	 /configurations/conf-1/signature-1)
 * @conf_noffset: Offset of configuration node (e.g. /configurations/conf-1)
 * @key_blob: Blob containing the keys to check against
 * @required_keynode:	Offset in @key_blob of the required key node,
 *			if any. If this is given, then the configuration wil not
 *			pass verification unless that key is used. If this is
 *			-1 then any signature will do.
 * @err_msgp:		In the event of an error, this will be pointed to a
 *			help error string to display to the user.
 * Return: 0 if all verified ok, <0 on error
 */
static int fit_config_check_sig(const void *fit, int noffset, int conf_noffset,
				const void *key_blob, int required_keynode,
				char **err_msgp)
{
	static char * const exc_prop[] = {
		FIT_DATA_PROP,
		FIT_DATA_SIZE_PROP,
		FIT_DATA_POSITION_PROP,
		FIT_DATA_OFFSET_PROP,
	};

	const char *prop, *end, *name;
	struct image_sign_info info;
	const uint32_t *strings;
	const char *config_name;
	uint8_t *fit_value;
	int fit_value_len;
	bool found_config;
	int max_regions;
	int i, prop_len;
	char path[200];
	int count;

	config_name = fit_get_name(fit, conf_noffset, NULL);
	debug("%s: fdt=%p, conf='%s', sig='%s'\n", __func__, key_blob,
	      fit_get_name(fit, noffset, NULL),
	      fit_get_name(key_blob, required_keynode, NULL));
	*err_msgp = NULL;
	if (fit_image_setup_verify(&info, fit, noffset, key_blob,
				   required_keynode, err_msgp))
		return -1;

	if (fit_image_hash_get_value(fit, noffset, &fit_value,
				     &fit_value_len)) {
		*err_msgp = "Can't get hash value property";
		return -1;
	}

	/* Count the number of strings in the property */
	prop = fdt_getprop(fit, noffset, "hashed-nodes", &prop_len);
	end = prop ? prop + prop_len : prop;
	for (name = prop, count = 0; name < end; name++)
		if (!*name)
			count++;
	if (!count) {
		*err_msgp = "Can't get hashed-nodes property";
		return -1;
	}

	if (prop && prop_len > 0 && prop[prop_len - 1] != '\0') {
		*err_msgp = "hashed-nodes property must be null-terminated";
		return -1;
	}

	/* Add a sanity check here since we are using the stack */
	if (count > IMAGE_MAX_HASHED_NODES) {
		*err_msgp = "Number of hashed nodes exceeds maximum";
		return -1;
	}

	/* Create a list of node names from those strings */
	char *node_inc[count];

	debug("Hash nodes (%d):\n", count);
	found_config = false;
	for (name = prop, i = 0; name < end; name += strlen(name) + 1, i++) {
		debug("   '%s'\n", name);
		node_inc[i] = (char *)name;
		if (!strncmp(FIT_CONFS_PATH, name, strlen(FIT_CONFS_PATH)) &&
		    name[sizeof(FIT_CONFS_PATH) - 1] == '/' &&
		    !strcmp(name + sizeof(FIT_CONFS_PATH), config_name)) {
			debug("      (found config node %s)", config_name);
			found_config = true;
		}
	}
	if (!found_config) {
		*err_msgp = "Selected config not in hashed nodes";
		return -1;
	}

	/*
	 * Each node can generate one region for each sub-node. Allow for
	 * 7 sub-nodes (hash-1, signature-1, etc.) and some extra.
	 */
	max_regions = 20 + count * 7;
	struct fdt_region fdt_regions[max_regions];

	/* Get a list of regions to hash */
	count = fdt_find_regions(fit, node_inc, count,
				 exc_prop, ARRAY_SIZE(exc_prop),
				 fdt_regions, max_regions - 1,
				 path, sizeof(path), 0);
	if (count < 0) {
		*err_msgp = "Failed to hash configuration";
		return -1;
	}
	if (count == 0) {
		*err_msgp = "No data to hash";
		return -1;
	}
	if (count >= max_regions - 1) {
		*err_msgp = "Too many hash regions";
		return -1;
	}

	/* Add the strings */
	strings = fdt_getprop(fit, noffset, "hashed-strings", NULL);
	if (strings) {
		/*
		 * The strings region offset must be a static 0x0.
		 * This is set in tool/image-host.c
		 */
		fdt_regions[count].offset = fdt_off_dt_strings(fit);
		fdt_regions[count].size = fdt32_to_cpu(strings[1]);
		count++;
	}

	/* Allocate the region list on the stack */
	struct image_region region[count];

	fit_region_make_list(fit, fdt_regions, count, region);
	if (info.crypto->verify(&info, region, count, fit_value,
				fit_value_len)) {
		*err_msgp = "Verification failed";
		return -1;
	}

	return 0;
}

/**
 * fit_config_verify_key() - Verify that a configuration is signed with a key
 *
 * Here we are looking at a particular configuration that needs verification:
 *
 *	configurations {
 *		default = "conf-1";
 *		conf-1 {
 *			kernel = "kernel-1";
 *			fdt = "fdt-1";
 *			signature-1 {
 *				algo = "sha1,rsa2048";
 *				value = <...conf 1 signature...>;
 *			};
 *		};
 *
 * We must check each of the signature subnodes of conf-1. Hopefully one of them
 * will match the key at key_offset.
 *
 * @fit: FIT to check
 * @conf_noffset: Offset of the configuration node to check (e.g.
 *	/configurations/conf-1)
 * @key_blob: Blob containing the keys to check against
 * @key_offset: Offset of the key to check within @key_blob
 * @return 0 if OK, -EPERM if any signatures did not verify, or the
 *	configuration node has an invalid name
 */
static int fit_config_verify_key(const void *fit, int conf_noffset,
				 const void *key_blob, int key_offset)
{
	int noffset;
	char *err_msg = "No 'signature' subnode found";
	int verified = 0;
	int ret;

	/* Process all hash subnodes of the component conf node */
	fdt_for_each_subnode(noffset, fit, conf_noffset) {
		const char *name = fit_get_name(fit, noffset, NULL);

		if (!strncmp(name, FIT_SIG_NODENAME,
			     strlen(FIT_SIG_NODENAME))) {
			ret = fit_config_check_sig(fit, noffset, conf_noffset,
						   key_blob, key_offset,
						   &err_msg);
			if (ret) {
				puts("- ");
			} else {
				puts("+ ");
				verified = 1;
				break;
			}
		}
	}

	if (noffset == -FDT_ERR_TRUNCATED || noffset == -FDT_ERR_BADSTRUCTURE) {
		err_msg = "Corrupted or truncated tree";
		goto error;
	}

	if (verified)
		return 0;

error:
	printf(" error!\n%s for '%s' hash node in '%s' config node\n",
	       err_msg, fit_get_name(fit, noffset, NULL),
	       fit_get_name(fit, conf_noffset, NULL));
	return -EPERM;
}

/**
 * fit_config_verify_required_keys() - verify any required signatures for config
 *
 * This looks through all the signatures we expect and verifies that at least
 * all the required ones are valid signatures for the configuration
 *
 * @fit: FIT to check
 * @conf_noffset: Offset of the configuration node to check (e.g.
 *	/configurations/conf-1)
 * @key_blob: Blob containing the keys to check against
 * @return 0 if OK, -EPERM if any signatures did not verify, or the
 *	configuration node has an invalid name
 */
static int fit_config_verify_required_keys(const void *fit, int conf_noffset,
					   const void *key_blob)
{
	const char *name = fit_get_name(fit, conf_noffset, NULL);
	int noffset;
	int key_node;
	int verified = 0;
	int reqd_sigs = 0;
	bool reqd_policy_all = true;
	const char *reqd_mode;

	/*
	 * We don't support this since libfdt considers names with the
	 * name root but different @ suffix to be equal
	 */
	if (strchr(name, '@')) {
		printf("Configuration node '%s' contains '@'\n", name);
		return -EPERM;
	}

	/* Work out what we need to verify */
	key_node = fdt_subnode_offset(key_blob, 0, FIT_SIG_NODENAME);
	if (key_node < 0) {
		debug("%s: No signature node found: %s\n", __func__,
		      fdt_strerror(key_node));
		return 0;
	}

	/* Get required-mode policy property from DTB */
	reqd_mode = fdt_getprop(key_blob, key_node, "required-mode", NULL);
	if (reqd_mode && !strcmp(reqd_mode, "any"))
		reqd_policy_all = false;

	debug("%s: required-mode policy set to '%s'\n", __func__,
	      reqd_policy_all ? "all" : "any");

	/*
	 * The algorithm here is a little convoluted due to how we want it to
	 * work. Here we work through each of the signature nodes in the
	 * public-key area. These are in the U-Boot control devicetree. Each
	 * node was created by signing a configuration, so we check if it is
	 * 'required' and if so, request that it be verified.
	 */
	fdt_for_each_subnode(noffset, key_blob, key_node) {
		const char *required;
		int ret;

		required = fdt_getprop(key_blob, noffset, FIT_KEY_REQUIRED,
				       NULL);
		if (!required || strcmp(required, "conf"))
			continue;

		reqd_sigs++;

		ret = fit_config_verify_key(fit, conf_noffset, key_blob,
					    noffset);
		if (ret) {
			if (reqd_policy_all) {
				printf("Failed to verify required signature '%s'\n",
				       fit_get_name(key_blob, noffset, NULL));
				return ret;
			}
		} else {
			verified++;
			if (!reqd_policy_all)
				break;
		}
	}

	if (reqd_sigs && !verified) {
		printf("Failed to verify 'any' of the required signature(s)\n");
		return -EPERM;
	}

	return 0;
}

int fit_config_verify(const void *fit, int conf_noffset)
{
	return fit_config_verify_required_keys(fit, conf_noffset,
					       gd_fdt_blob());
}