1 /* Asymmetric public-key cryptography key type
2  *
3  * See Documentation/crypto/asymmetric-keys.txt
4  *
5  * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
6  * Written by David Howells (dhowells@redhat.com)
7  *
8  * This program is free software; you can redistribute it and/or
9  * modify it under the terms of the GNU General Public Licence
10  * as published by the Free Software Foundation; either version
11  * 2 of the Licence, or (at your option) any later version.
12  */
13 #include <keys/asymmetric-subtype.h>
14 #include <keys/asymmetric-parser.h>
15 #include <crypto/public_key.h>
16 #include <linux/seq_file.h>
17 #include <linux/module.h>
18 #include <linux/slab.h>
19 #include <linux/ctype.h>
20 #include <keys/system_keyring.h>
21 #include "asymmetric_keys.h"
22 
23 MODULE_LICENSE("GPL");
24 
25 const char *const key_being_used_for[NR__KEY_BEING_USED_FOR] = {
26 	[VERIFYING_MODULE_SIGNATURE]		= "mod sig",
27 	[VERIFYING_FIRMWARE_SIGNATURE]		= "firmware sig",
28 	[VERIFYING_KEXEC_PE_SIGNATURE]		= "kexec PE sig",
29 	[VERIFYING_KEY_SIGNATURE]		= "key sig",
30 	[VERIFYING_KEY_SELF_SIGNATURE]		= "key self sig",
31 	[VERIFYING_UNSPECIFIED_SIGNATURE]	= "unspec sig",
32 };
33 EXPORT_SYMBOL_GPL(key_being_used_for);
34 
35 static LIST_HEAD(asymmetric_key_parsers);
36 static DECLARE_RWSEM(asymmetric_key_parsers_sem);
37 
38 /**
39  * find_asymmetric_key - Find a key by ID.
40  * @keyring: The keys to search.
41  * @id_0: The first ID to look for or NULL.
42  * @id_1: The second ID to look for or NULL.
43  * @partial: Use partial match if true, exact if false.
44  *
45  * Find a key in the given keyring by identifier.  The preferred identifier is
46  * the id_0 and the fallback identifier is the id_1.  If both are given, the
47  * lookup is by the former, but the latter must also match.
48  */
find_asymmetric_key(struct key * keyring,const struct asymmetric_key_id * id_0,const struct asymmetric_key_id * id_1,bool partial)49 struct key *find_asymmetric_key(struct key *keyring,
50 				const struct asymmetric_key_id *id_0,
51 				const struct asymmetric_key_id *id_1,
52 				bool partial)
53 {
54 	struct key *key;
55 	key_ref_t ref;
56 	const char *lookup;
57 	char *req, *p;
58 	int len;
59 
60 	BUG_ON(!id_0 && !id_1);
61 
62 	if (id_0) {
63 		lookup = id_0->data;
64 		len = id_0->len;
65 	} else {
66 		lookup = id_1->data;
67 		len = id_1->len;
68 	}
69 
70 	/* Construct an identifier "id:<keyid>". */
71 	p = req = kmalloc(2 + 1 + len * 2 + 1, GFP_KERNEL);
72 	if (!req)
73 		return ERR_PTR(-ENOMEM);
74 
75 	if (partial) {
76 		*p++ = 'i';
77 		*p++ = 'd';
78 	} else {
79 		*p++ = 'e';
80 		*p++ = 'x';
81 	}
82 	*p++ = ':';
83 	p = bin2hex(p, lookup, len);
84 	*p = 0;
85 
86 	pr_debug("Look up: \"%s\"\n", req);
87 
88 	ref = keyring_search(make_key_ref(keyring, 1),
89 			     &key_type_asymmetric, req);
90 	if (IS_ERR(ref))
91 		pr_debug("Request for key '%s' err %ld\n", req, PTR_ERR(ref));
92 	kfree(req);
93 
94 	if (IS_ERR(ref)) {
95 		switch (PTR_ERR(ref)) {
96 			/* Hide some search errors */
97 		case -EACCES:
98 		case -ENOTDIR:
99 		case -EAGAIN:
100 			return ERR_PTR(-ENOKEY);
101 		default:
102 			return ERR_CAST(ref);
103 		}
104 	}
105 
106 	key = key_ref_to_ptr(ref);
107 	if (id_0 && id_1) {
108 		const struct asymmetric_key_ids *kids = asymmetric_key_ids(key);
109 
110 		if (!kids->id[1]) {
111 			pr_debug("First ID matches, but second is missing\n");
112 			goto reject;
113 		}
114 		if (!asymmetric_key_id_same(id_1, kids->id[1])) {
115 			pr_debug("First ID matches, but second does not\n");
116 			goto reject;
117 		}
118 	}
119 
120 	pr_devel("<==%s() = 0 [%x]\n", __func__, key_serial(key));
121 	return key;
122 
123 reject:
124 	key_put(key);
125 	return ERR_PTR(-EKEYREJECTED);
126 }
127 EXPORT_SYMBOL_GPL(find_asymmetric_key);
128 
129 /**
130  * asymmetric_key_generate_id: Construct an asymmetric key ID
131  * @val_1: First binary blob
132  * @len_1: Length of first binary blob
133  * @val_2: Second binary blob
134  * @len_2: Length of second binary blob
135  *
136  * Construct an asymmetric key ID from a pair of binary blobs.
137  */
asymmetric_key_generate_id(const void * val_1,size_t len_1,const void * val_2,size_t len_2)138 struct asymmetric_key_id *asymmetric_key_generate_id(const void *val_1,
139 						     size_t len_1,
140 						     const void *val_2,
141 						     size_t len_2)
142 {
143 	struct asymmetric_key_id *kid;
144 
145 	kid = kmalloc(sizeof(struct asymmetric_key_id) + len_1 + len_2,
146 		      GFP_KERNEL);
147 	if (!kid)
148 		return ERR_PTR(-ENOMEM);
149 	kid->len = len_1 + len_2;
150 	memcpy(kid->data, val_1, len_1);
151 	memcpy(kid->data + len_1, val_2, len_2);
152 	return kid;
153 }
154 EXPORT_SYMBOL_GPL(asymmetric_key_generate_id);
155 
156 /**
157  * asymmetric_key_id_same - Return true if two asymmetric keys IDs are the same.
158  * @kid_1, @kid_2: The key IDs to compare
159  */
asymmetric_key_id_same(const struct asymmetric_key_id * kid1,const struct asymmetric_key_id * kid2)160 bool asymmetric_key_id_same(const struct asymmetric_key_id *kid1,
161 			    const struct asymmetric_key_id *kid2)
162 {
163 	if (!kid1 || !kid2)
164 		return false;
165 	if (kid1->len != kid2->len)
166 		return false;
167 	return memcmp(kid1->data, kid2->data, kid1->len) == 0;
168 }
169 EXPORT_SYMBOL_GPL(asymmetric_key_id_same);
170 
171 /**
172  * asymmetric_key_id_partial - Return true if two asymmetric keys IDs
173  * partially match
174  * @kid_1, @kid_2: The key IDs to compare
175  */
asymmetric_key_id_partial(const struct asymmetric_key_id * kid1,const struct asymmetric_key_id * kid2)176 bool asymmetric_key_id_partial(const struct asymmetric_key_id *kid1,
177 			       const struct asymmetric_key_id *kid2)
178 {
179 	if (!kid1 || !kid2)
180 		return false;
181 	if (kid1->len < kid2->len)
182 		return false;
183 	return memcmp(kid1->data + (kid1->len - kid2->len),
184 		      kid2->data, kid2->len) == 0;
185 }
186 EXPORT_SYMBOL_GPL(asymmetric_key_id_partial);
187 
188 /**
189  * asymmetric_match_key_ids - Search asymmetric key IDs
190  * @kids: The list of key IDs to check
191  * @match_id: The key ID we're looking for
192  * @match: The match function to use
193  */
asymmetric_match_key_ids(const struct asymmetric_key_ids * kids,const struct asymmetric_key_id * match_id,bool (* match)(const struct asymmetric_key_id * kid1,const struct asymmetric_key_id * kid2))194 static bool asymmetric_match_key_ids(
195 	const struct asymmetric_key_ids *kids,
196 	const struct asymmetric_key_id *match_id,
197 	bool (*match)(const struct asymmetric_key_id *kid1,
198 		      const struct asymmetric_key_id *kid2))
199 {
200 	int i;
201 
202 	if (!kids || !match_id)
203 		return false;
204 	for (i = 0; i < ARRAY_SIZE(kids->id); i++)
205 		if (match(kids->id[i], match_id))
206 			return true;
207 	return false;
208 }
209 
210 /* helper function can be called directly with pre-allocated memory */
__asymmetric_key_hex_to_key_id(const char * id,struct asymmetric_key_id * match_id,size_t hexlen)211 inline int __asymmetric_key_hex_to_key_id(const char *id,
212 				   struct asymmetric_key_id *match_id,
213 				   size_t hexlen)
214 {
215 	match_id->len = hexlen;
216 	return hex2bin(match_id->data, id, hexlen);
217 }
218 
219 /**
220  * asymmetric_key_hex_to_key_id - Convert a hex string into a key ID.
221  * @id: The ID as a hex string.
222  */
asymmetric_key_hex_to_key_id(const char * id)223 struct asymmetric_key_id *asymmetric_key_hex_to_key_id(const char *id)
224 {
225 	struct asymmetric_key_id *match_id;
226 	size_t asciihexlen;
227 	int ret;
228 
229 	if (!*id)
230 		return ERR_PTR(-EINVAL);
231 	asciihexlen = strlen(id);
232 	if (asciihexlen & 1)
233 		return ERR_PTR(-EINVAL);
234 
235 	match_id = kmalloc(sizeof(struct asymmetric_key_id) + asciihexlen / 2,
236 			   GFP_KERNEL);
237 	if (!match_id)
238 		return ERR_PTR(-ENOMEM);
239 	ret = __asymmetric_key_hex_to_key_id(id, match_id, asciihexlen / 2);
240 	if (ret < 0) {
241 		kfree(match_id);
242 		return ERR_PTR(-EINVAL);
243 	}
244 	return match_id;
245 }
246 
247 /*
248  * Match asymmetric keys by an exact match on an ID.
249  */
asymmetric_key_cmp(const struct key * key,const struct key_match_data * match_data)250 static bool asymmetric_key_cmp(const struct key *key,
251 			       const struct key_match_data *match_data)
252 {
253 	const struct asymmetric_key_ids *kids = asymmetric_key_ids(key);
254 	const struct asymmetric_key_id *match_id = match_data->preparsed;
255 
256 	return asymmetric_match_key_ids(kids, match_id,
257 					asymmetric_key_id_same);
258 }
259 
260 /*
261  * Match asymmetric keys by a partial match on an IDs.
262  */
asymmetric_key_cmp_partial(const struct key * key,const struct key_match_data * match_data)263 static bool asymmetric_key_cmp_partial(const struct key *key,
264 				       const struct key_match_data *match_data)
265 {
266 	const struct asymmetric_key_ids *kids = asymmetric_key_ids(key);
267 	const struct asymmetric_key_id *match_id = match_data->preparsed;
268 
269 	return asymmetric_match_key_ids(kids, match_id,
270 					asymmetric_key_id_partial);
271 }
272 
273 /*
274  * Preparse the match criterion.  If we don't set lookup_type and cmp,
275  * the default will be an exact match on the key description.
276  *
277  * There are some specifiers for matching key IDs rather than by the key
278  * description:
279  *
280  *	"id:<id>" - find a key by partial match on any available ID
281  *	"ex:<id>" - find a key by exact match on any available ID
282  *
283  * These have to be searched by iteration rather than by direct lookup because
284  * the key is hashed according to its description.
285  */
asymmetric_key_match_preparse(struct key_match_data * match_data)286 static int asymmetric_key_match_preparse(struct key_match_data *match_data)
287 {
288 	struct asymmetric_key_id *match_id;
289 	const char *spec = match_data->raw_data;
290 	const char *id;
291 	bool (*cmp)(const struct key *, const struct key_match_data *) =
292 		asymmetric_key_cmp;
293 
294 	if (!spec || !*spec)
295 		return -EINVAL;
296 	if (spec[0] == 'i' &&
297 	    spec[1] == 'd' &&
298 	    spec[2] == ':') {
299 		id = spec + 3;
300 		cmp = asymmetric_key_cmp_partial;
301 	} else if (spec[0] == 'e' &&
302 		   spec[1] == 'x' &&
303 		   spec[2] == ':') {
304 		id = spec + 3;
305 	} else {
306 		goto default_match;
307 	}
308 
309 	match_id = asymmetric_key_hex_to_key_id(id);
310 	if (IS_ERR(match_id))
311 		return PTR_ERR(match_id);
312 
313 	match_data->preparsed = match_id;
314 	match_data->cmp = cmp;
315 	match_data->lookup_type = KEYRING_SEARCH_LOOKUP_ITERATE;
316 	return 0;
317 
318 default_match:
319 	return 0;
320 }
321 
322 /*
323  * Free the preparsed the match criterion.
324  */
asymmetric_key_match_free(struct key_match_data * match_data)325 static void asymmetric_key_match_free(struct key_match_data *match_data)
326 {
327 	kfree(match_data->preparsed);
328 }
329 
330 /*
331  * Describe the asymmetric key
332  */
asymmetric_key_describe(const struct key * key,struct seq_file * m)333 static void asymmetric_key_describe(const struct key *key, struct seq_file *m)
334 {
335 	const struct asymmetric_key_subtype *subtype = asymmetric_key_subtype(key);
336 	const struct asymmetric_key_ids *kids = asymmetric_key_ids(key);
337 	const struct asymmetric_key_id *kid;
338 	const unsigned char *p;
339 	int n;
340 
341 	seq_puts(m, key->description);
342 
343 	if (subtype) {
344 		seq_puts(m, ": ");
345 		subtype->describe(key, m);
346 
347 		if (kids && kids->id[1]) {
348 			kid = kids->id[1];
349 			seq_putc(m, ' ');
350 			n = kid->len;
351 			p = kid->data;
352 			if (n > 4) {
353 				p += n - 4;
354 				n = 4;
355 			}
356 			seq_printf(m, "%*phN", n, p);
357 		}
358 
359 		seq_puts(m, " [");
360 		/* put something here to indicate the key's capabilities */
361 		seq_putc(m, ']');
362 	}
363 }
364 
365 /*
366  * Preparse a asymmetric payload to get format the contents appropriately for the
367  * internal payload to cut down on the number of scans of the data performed.
368  *
369  * We also generate a proposed description from the contents of the key that
370  * can be used to name the key if the user doesn't want to provide one.
371  */
asymmetric_key_preparse(struct key_preparsed_payload * prep)372 static int asymmetric_key_preparse(struct key_preparsed_payload *prep)
373 {
374 	struct asymmetric_key_parser *parser;
375 	int ret;
376 
377 	pr_devel("==>%s()\n", __func__);
378 
379 	if (prep->datalen == 0)
380 		return -EINVAL;
381 
382 	down_read(&asymmetric_key_parsers_sem);
383 
384 	ret = -EBADMSG;
385 	list_for_each_entry(parser, &asymmetric_key_parsers, link) {
386 		pr_debug("Trying parser '%s'\n", parser->name);
387 
388 		ret = parser->parse(prep);
389 		if (ret != -EBADMSG) {
390 			pr_debug("Parser recognised the format (ret %d)\n",
391 				 ret);
392 			break;
393 		}
394 	}
395 
396 	up_read(&asymmetric_key_parsers_sem);
397 	pr_devel("<==%s() = %d\n", __func__, ret);
398 	return ret;
399 }
400 
401 /*
402  * Clean up the key ID list
403  */
asymmetric_key_free_kids(struct asymmetric_key_ids * kids)404 static void asymmetric_key_free_kids(struct asymmetric_key_ids *kids)
405 {
406 	int i;
407 
408 	if (kids) {
409 		for (i = 0; i < ARRAY_SIZE(kids->id); i++)
410 			kfree(kids->id[i]);
411 		kfree(kids);
412 	}
413 }
414 
415 /*
416  * Clean up the preparse data
417  */
asymmetric_key_free_preparse(struct key_preparsed_payload * prep)418 static void asymmetric_key_free_preparse(struct key_preparsed_payload *prep)
419 {
420 	struct asymmetric_key_subtype *subtype = prep->payload.data[asym_subtype];
421 	struct asymmetric_key_ids *kids = prep->payload.data[asym_key_ids];
422 
423 	pr_devel("==>%s()\n", __func__);
424 
425 	if (subtype) {
426 		subtype->destroy(prep->payload.data[asym_crypto],
427 				 prep->payload.data[asym_auth]);
428 		module_put(subtype->owner);
429 	}
430 	asymmetric_key_free_kids(kids);
431 	kfree(prep->description);
432 }
433 
434 /*
435  * dispose of the data dangling from the corpse of a asymmetric key
436  */
asymmetric_key_destroy(struct key * key)437 static void asymmetric_key_destroy(struct key *key)
438 {
439 	struct asymmetric_key_subtype *subtype = asymmetric_key_subtype(key);
440 	struct asymmetric_key_ids *kids = key->payload.data[asym_key_ids];
441 	void *data = key->payload.data[asym_crypto];
442 	void *auth = key->payload.data[asym_auth];
443 
444 	key->payload.data[asym_crypto] = NULL;
445 	key->payload.data[asym_subtype] = NULL;
446 	key->payload.data[asym_key_ids] = NULL;
447 	key->payload.data[asym_auth] = NULL;
448 
449 	if (subtype) {
450 		subtype->destroy(data, auth);
451 		module_put(subtype->owner);
452 	}
453 
454 	asymmetric_key_free_kids(kids);
455 }
456 
asymmetric_restriction_alloc(key_restrict_link_func_t check,struct key * key)457 static struct key_restriction *asymmetric_restriction_alloc(
458 	key_restrict_link_func_t check,
459 	struct key *key)
460 {
461 	struct key_restriction *keyres =
462 		kzalloc(sizeof(struct key_restriction), GFP_KERNEL);
463 
464 	if (!keyres)
465 		return ERR_PTR(-ENOMEM);
466 
467 	keyres->check = check;
468 	keyres->key = key;
469 	keyres->keytype = &key_type_asymmetric;
470 
471 	return keyres;
472 }
473 
474 /*
475  * look up keyring restrict functions for asymmetric keys
476  */
asymmetric_lookup_restriction(const char * restriction)477 static struct key_restriction *asymmetric_lookup_restriction(
478 	const char *restriction)
479 {
480 	char *restrict_method;
481 	char *parse_buf;
482 	char *next;
483 	struct key_restriction *ret = ERR_PTR(-EINVAL);
484 
485 	if (strcmp("builtin_trusted", restriction) == 0)
486 		return asymmetric_restriction_alloc(
487 			restrict_link_by_builtin_trusted, NULL);
488 
489 	if (strcmp("builtin_and_secondary_trusted", restriction) == 0)
490 		return asymmetric_restriction_alloc(
491 			restrict_link_by_builtin_and_secondary_trusted, NULL);
492 
493 	parse_buf = kstrndup(restriction, PAGE_SIZE, GFP_KERNEL);
494 	if (!parse_buf)
495 		return ERR_PTR(-ENOMEM);
496 
497 	next = parse_buf;
498 	restrict_method = strsep(&next, ":");
499 
500 	if ((strcmp(restrict_method, "key_or_keyring") == 0) && next) {
501 		char *key_text;
502 		key_serial_t serial;
503 		struct key *key;
504 		key_restrict_link_func_t link_fn =
505 			restrict_link_by_key_or_keyring;
506 		bool allow_null_key = false;
507 
508 		key_text = strsep(&next, ":");
509 
510 		if (next) {
511 			if (strcmp(next, "chain") != 0)
512 				goto out;
513 
514 			link_fn = restrict_link_by_key_or_keyring_chain;
515 			allow_null_key = true;
516 		}
517 
518 		if (kstrtos32(key_text, 0, &serial) < 0)
519 			goto out;
520 
521 		if ((serial == 0) && allow_null_key) {
522 			key = NULL;
523 		} else {
524 			key = key_lookup(serial);
525 			if (IS_ERR(key)) {
526 				ret = ERR_CAST(key);
527 				goto out;
528 			}
529 		}
530 
531 		ret = asymmetric_restriction_alloc(link_fn, key);
532 		if (IS_ERR(ret))
533 			key_put(key);
534 	}
535 
536 out:
537 	kfree(parse_buf);
538 	return ret;
539 }
540 
541 struct key_type key_type_asymmetric = {
542 	.name			= "asymmetric",
543 	.preparse		= asymmetric_key_preparse,
544 	.free_preparse		= asymmetric_key_free_preparse,
545 	.instantiate		= generic_key_instantiate,
546 	.match_preparse		= asymmetric_key_match_preparse,
547 	.match_free		= asymmetric_key_match_free,
548 	.destroy		= asymmetric_key_destroy,
549 	.describe		= asymmetric_key_describe,
550 	.lookup_restriction	= asymmetric_lookup_restriction,
551 };
552 EXPORT_SYMBOL_GPL(key_type_asymmetric);
553 
554 /**
555  * register_asymmetric_key_parser - Register a asymmetric key blob parser
556  * @parser: The parser to register
557  */
register_asymmetric_key_parser(struct asymmetric_key_parser * parser)558 int register_asymmetric_key_parser(struct asymmetric_key_parser *parser)
559 {
560 	struct asymmetric_key_parser *cursor;
561 	int ret;
562 
563 	down_write(&asymmetric_key_parsers_sem);
564 
565 	list_for_each_entry(cursor, &asymmetric_key_parsers, link) {
566 		if (strcmp(cursor->name, parser->name) == 0) {
567 			pr_err("Asymmetric key parser '%s' already registered\n",
568 			       parser->name);
569 			ret = -EEXIST;
570 			goto out;
571 		}
572 	}
573 
574 	list_add_tail(&parser->link, &asymmetric_key_parsers);
575 
576 	pr_notice("Asymmetric key parser '%s' registered\n", parser->name);
577 	ret = 0;
578 
579 out:
580 	up_write(&asymmetric_key_parsers_sem);
581 	return ret;
582 }
583 EXPORT_SYMBOL_GPL(register_asymmetric_key_parser);
584 
585 /**
586  * unregister_asymmetric_key_parser - Unregister a asymmetric key blob parser
587  * @parser: The parser to unregister
588  */
unregister_asymmetric_key_parser(struct asymmetric_key_parser * parser)589 void unregister_asymmetric_key_parser(struct asymmetric_key_parser *parser)
590 {
591 	down_write(&asymmetric_key_parsers_sem);
592 	list_del(&parser->link);
593 	up_write(&asymmetric_key_parsers_sem);
594 
595 	pr_notice("Asymmetric key parser '%s' unregistered\n", parser->name);
596 }
597 EXPORT_SYMBOL_GPL(unregister_asymmetric_key_parser);
598 
599 /*
600  * Module stuff
601  */
asymmetric_key_init(void)602 static int __init asymmetric_key_init(void)
603 {
604 	return register_key_type(&key_type_asymmetric);
605 }
606 
asymmetric_key_cleanup(void)607 static void __exit asymmetric_key_cleanup(void)
608 {
609 	unregister_key_type(&key_type_asymmetric);
610 }
611 
612 module_init(asymmetric_key_init);
613 module_exit(asymmetric_key_cleanup);
614