asymmetric_type.c

  1// SPDX-License-Identifier: GPL-2.0-or-later
  2/* Asymmetric public-key cryptography key type
  3 *
  4 * See Documentation/crypto/asymmetric-keys.rst
  5 *
  6 * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
  7 * Written by David Howells (dhowells@redhat.com)
  8 */
  9#include <keys/asymmetric-subtype.h>
 10#include <keys/asymmetric-parser.h>
 11#include <crypto/public_key.h>
 12#include <linux/seq_file.h>
 13#include <linux/module.h>
 14#include <linux/overflow.h>
 15#include <linux/slab.h>
 16#include <linux/ctype.h>
 17#include <keys/system_keyring.h>
 18#include <keys/user-type.h>
 19#include "asymmetric_keys.h"
 20
 21
 22static LIST_HEAD(asymmetric_key_parsers);
 23static DECLARE_RWSEM(asymmetric_key_parsers_sem);
 24
 25/**
 26 * find_asymmetric_key - Find a key by ID.
 27 * @keyring: The keys to search.
 28 * @id_0: The first ID to look for or NULL.
 29 * @id_1: The second ID to look for or NULL, matched together with @id_0
 30 * against @keyring keys' id[0] and id[1].
 31 * @id_2: The fallback ID to match against @keyring keys' id[2] if both of the
 32 * other IDs are NULL.
 33 * @partial: Use partial match for @id_0 and @id_1 if true, exact if false.
 34 *
 35 * Find a key in the given keyring by identifier.  The preferred identifier is
 36 * the id_0 and the fallback identifier is the id_1.  If both are given, the
 37 * former is matched (exactly or partially) against either of the sought key's
 38 * identifiers and the latter must match the found key's second identifier
 39 * exactly.  If both are missing, id_2 must match the sought key's third
 40 * identifier exactly.
 41 */
 42struct key *find_asymmetric_key(struct key *keyring,
 43				const struct asymmetric_key_id *id_0,
 44				const struct asymmetric_key_id *id_1,
 45				const struct asymmetric_key_id *id_2,
 46				bool partial)
 47{
 48	struct key *key;
 49	key_ref_t ref;
 50	const char *lookup;
 51	char *req, *p;
 52	int len;
 53
 54	if (id_0) {
 55		lookup = id_0->data;
 56		len = id_0->len;
 57	} else if (id_1) {
 58		lookup = id_1->data;
 59		len = id_1->len;
 60	} else if (id_2) {
 61		lookup = id_2->data;
 62		len = id_2->len;
 63	} else {
 64		WARN_ON(1);
 65		return ERR_PTR(-EINVAL);
 66	}
 67
 68	/* Construct an identifier "id:<keyid>". */
 69	p = req = kmalloc(2 + 1 + len * 2 + 1, GFP_KERNEL);
 70	if (!req)
 71		return ERR_PTR(-ENOMEM);
 72
 73	if (!id_0 && !id_1) {
 74		*p++ = 'd';
 75		*p++ = 'n';
 76	} else if (partial) {
 77		*p++ = 'i';
 78		*p++ = 'd';
 79	} else {
 80		*p++ = 'e';
 81		*p++ = 'x';
 82	}
 83	*p++ = ':';
 84	p = bin2hex(p, lookup, len);
 85	*p = 0;
 86
 87	pr_debug("Look up: \"%s\"\n", req);
 88
 89	ref = keyring_search(make_key_ref(keyring, 1),
 90			     &key_type_asymmetric, req, true);
 91	if (IS_ERR(ref))
 92		pr_debug("Request for key '%s' err %ld\n", req, PTR_ERR(ref));
 93	kfree(req);
 94
 95	if (IS_ERR(ref)) {
 96		switch (PTR_ERR(ref)) {
 97			/* Hide some search errors */
 98		case -EACCES:
 99		case -ENOTDIR:
100		case -EAGAIN:
101			return ERR_PTR(-ENOKEY);
102		default:
103			return ERR_CAST(ref);
104		}
105	}
106
107	key = key_ref_to_ptr(ref);
108	if (id_0 && id_1) {
109		const struct asymmetric_key_ids *kids = asymmetric_key_ids(key);
110
111		if (!kids->id[1]) {
112			pr_debug("First ID matches, but second is missing\n");
113			goto reject;
114		}
115		if (!asymmetric_key_id_same(id_1, kids->id[1])) {
116			pr_debug("First ID matches, but second does not\n");
117			goto reject;
118		}
119	}
120
121	pr_devel("<==%s() = 0 [%x]\n", __func__, key_serial(key));
122	return key;
123
124reject:
125	key_put(key);
126	return ERR_PTR(-EKEYREJECTED);
127}
128EXPORT_SYMBOL_GPL(find_asymmetric_key);
129
130/**
131 * asymmetric_key_generate_id: Construct an asymmetric key ID
132 * @val_1: First binary blob
133 * @len_1: Length of first binary blob
134 * @val_2: Second binary blob
135 * @len_2: Length of second binary blob
136 *
137 * Construct an asymmetric key ID from a pair of binary blobs.
138 */
139struct asymmetric_key_id *asymmetric_key_generate_id(const void *val_1,
140						     size_t len_1,
141						     const void *val_2,
142						     size_t len_2)
143{
144	struct asymmetric_key_id *kid;
145	size_t kid_sz;
146	size_t len;
147
148	if (check_add_overflow(len_1, len_2, &len))
149		return ERR_PTR(-EOVERFLOW);
150	if (check_add_overflow(sizeof(struct asymmetric_key_id), len, &kid_sz))
151		return ERR_PTR(-EOVERFLOW);
152	kid = kmalloc(kid_sz, GFP_KERNEL);
153	if (!kid)
154		return ERR_PTR(-ENOMEM);
155	kid->len = len;
156	memcpy(kid->data, val_1, len_1);
157	memcpy(kid->data + len_1, val_2, len_2);
158	return kid;
159}
160EXPORT_SYMBOL_GPL(asymmetric_key_generate_id);
161
162/**
163 * asymmetric_key_id_same - Return true if two asymmetric keys IDs are the same.
164 * @kid1: The key ID to compare
165 * @kid2: The key ID to compare
166 */
167bool asymmetric_key_id_same(const struct asymmetric_key_id *kid1,
168			    const struct asymmetric_key_id *kid2)
169{
170	if (!kid1 || !kid2)
171		return false;
172	if (kid1->len != kid2->len)
173		return false;
174	return memcmp(kid1->data, kid2->data, kid1->len) == 0;
175}
176EXPORT_SYMBOL_GPL(asymmetric_key_id_same);
177
178/**
179 * asymmetric_key_id_partial - Return true if two asymmetric keys IDs
180 * partially match
181 * @kid1: The key ID to compare
182 * @kid2: The key ID to compare
183 */
184bool asymmetric_key_id_partial(const struct asymmetric_key_id *kid1,
185			       const struct asymmetric_key_id *kid2)
186{
187	if (!kid1 || !kid2)
188		return false;
189	if (kid1->len < kid2->len)
190		return false;
191	return memcmp(kid1->data + (kid1->len - kid2->len),
192		      kid2->data, kid2->len) == 0;
193}
194EXPORT_SYMBOL_GPL(asymmetric_key_id_partial);
195
196/**
197 * asymmetric_match_key_ids - Search asymmetric key IDs 1 & 2
198 * @kids: The pair of key IDs to check
199 * @match_id: The key ID we're looking for
200 * @match: The match function to use
201 */
202static bool asymmetric_match_key_ids(
203	const struct asymmetric_key_ids *kids,
204	const struct asymmetric_key_id *match_id,
205	bool (*match)(const struct asymmetric_key_id *kid1,
206		      const struct asymmetric_key_id *kid2))
207{
208	int i;
209
210	if (!kids || !match_id)
211		return false;
212	for (i = 0; i < 2; i++)
213		if (match(kids->id[i], match_id))
214			return true;
215	return false;
216}
217
218/* helper function can be called directly with pre-allocated memory */
219inline int __asymmetric_key_hex_to_key_id(const char *id,
220				   struct asymmetric_key_id *match_id,
221				   size_t hexlen)
222{
223	match_id->len = hexlen;
224	return hex2bin(match_id->data, id, hexlen);
225}
226
227/**
228 * asymmetric_key_hex_to_key_id - Convert a hex string into a key ID.
229 * @id: The ID as a hex string.
230 */
231struct asymmetric_key_id *asymmetric_key_hex_to_key_id(const char *id)
232{
233	struct asymmetric_key_id *match_id;
234	size_t asciihexlen;
235	int ret;
236
237	if (!*id)
238		return ERR_PTR(-EINVAL);
239	asciihexlen = strlen(id);
240	if (asciihexlen & 1)
241		return ERR_PTR(-EINVAL);
242
243	match_id = kmalloc(sizeof(struct asymmetric_key_id) + asciihexlen / 2,
244			   GFP_KERNEL);
245	if (!match_id)
246		return ERR_PTR(-ENOMEM);
247	ret = __asymmetric_key_hex_to_key_id(id, match_id, asciihexlen / 2);
248	if (ret < 0) {
249		kfree(match_id);
250		return ERR_PTR(-EINVAL);
251	}
252	return match_id;
253}
254
255/*
256 * Match asymmetric keys by an exact match on one of the first two IDs.
257 */
258static bool asymmetric_key_cmp(const struct key *key,
259			       const struct key_match_data *match_data)
260{
261	const struct asymmetric_key_ids *kids = asymmetric_key_ids(key);
262	const struct asymmetric_key_id *match_id = match_data->preparsed;
263
264	return asymmetric_match_key_ids(kids, match_id,
265					asymmetric_key_id_same);
266}
267
268/*
269 * Match asymmetric keys by a partial match on one of the first two IDs.
270 */
271static bool asymmetric_key_cmp_partial(const struct key *key,
272				       const struct key_match_data *match_data)
273{
274	const struct asymmetric_key_ids *kids = asymmetric_key_ids(key);
275	const struct asymmetric_key_id *match_id = match_data->preparsed;
276
277	return asymmetric_match_key_ids(kids, match_id,
278					asymmetric_key_id_partial);
279}
280
281/*
282 * Match asymmetric keys by an exact match on the third IDs.
283 */
284static bool asymmetric_key_cmp_name(const struct key *key,
285				    const struct key_match_data *match_data)
286{
287	const struct asymmetric_key_ids *kids = asymmetric_key_ids(key);
288	const struct asymmetric_key_id *match_id = match_data->preparsed;
289
290	return kids && asymmetric_key_id_same(kids->id[2], match_id);
291}
292
293/*
294 * Preparse the match criterion.  If we don't set lookup_type and cmp,
295 * the default will be an exact match on the key description.
296 *
297 * There are some specifiers for matching key IDs rather than by the key
298 * description:
299 *
300 *	"id:<id>" - find a key by partial match on one of the first two IDs
301 *	"ex:<id>" - find a key by exact match on one of the first two IDs
302 *	"dn:<id>" - find a key by exact match on the third ID
303 *
304 * These have to be searched by iteration rather than by direct lookup because
305 * the key is hashed according to its description.
306 */
307static int asymmetric_key_match_preparse(struct key_match_data *match_data)
308{
309	struct asymmetric_key_id *match_id;
310	const char *spec = match_data->raw_data;
311	const char *id;
312	bool (*cmp)(const struct key *, const struct key_match_data *) =
313		asymmetric_key_cmp;
314
315	if (!spec || !*spec)
316		return -EINVAL;
317	if (spec[0] == 'i' &&
318	    spec[1] == 'd' &&
319	    spec[2] == ':') {
320		id = spec + 3;
321		cmp = asymmetric_key_cmp_partial;
322	} else if (spec[0] == 'e' &&
323		   spec[1] == 'x' &&
324		   spec[2] == ':') {
325		id = spec + 3;
326	} else if (spec[0] == 'd' &&
327		   spec[1] == 'n' &&
328		   spec[2] == ':') {
329		id = spec + 3;
330		cmp = asymmetric_key_cmp_name;
331	} else {
332		goto default_match;
333	}
334
335	match_id = asymmetric_key_hex_to_key_id(id);
336	if (IS_ERR(match_id))
337		return PTR_ERR(match_id);
338
339	match_data->preparsed = match_id;
340	match_data->cmp = cmp;
341	match_data->lookup_type = KEYRING_SEARCH_LOOKUP_ITERATE;
342	return 0;
343
344default_match:
345	return 0;
346}
347
348/*
349 * Free the preparsed the match criterion.
350 */
351static void asymmetric_key_match_free(struct key_match_data *match_data)
352{
353	kfree(match_data->preparsed);
354}
355
356/*
357 * Describe the asymmetric key
358 */
359static void asymmetric_key_describe(const struct key *key, struct seq_file *m)
360{
361	const struct asymmetric_key_subtype *subtype = asymmetric_key_subtype(key);
362	const struct asymmetric_key_ids *kids = asymmetric_key_ids(key);
363	const struct asymmetric_key_id *kid;
364	const unsigned char *p;
365	int n;
366
367	seq_puts(m, key->description);
368
369	if (subtype) {
370		seq_puts(m, ": ");
371		subtype->describe(key, m);
372
373		if (kids && kids->id[1]) {
374			kid = kids->id[1];
375			seq_putc(m, ' ');
376			n = kid->len;
377			p = kid->data;
378			if (n > 4) {
379				p += n - 4;
380				n = 4;
381			}
382			seq_printf(m, "%*phN", n, p);
383		}
384
385		seq_puts(m, " [");
386		/* put something here to indicate the key's capabilities */
387		seq_putc(m, ']');
388	}
389}
390
391/*
392 * Preparse a asymmetric payload to get format the contents appropriately for the
393 * internal payload to cut down on the number of scans of the data performed.
394 *
395 * We also generate a proposed description from the contents of the key that
396 * can be used to name the key if the user doesn't want to provide one.
397 */
398static int asymmetric_key_preparse(struct key_preparsed_payload *prep)
399{
400	struct asymmetric_key_parser *parser;
401	int ret;
402
403	pr_devel("==>%s()\n", __func__);
404
405	if (prep->datalen == 0)
406		return -EINVAL;
407
408	down_read(&asymmetric_key_parsers_sem);
409
410	ret = -EBADMSG;
411	list_for_each_entry(parser, &asymmetric_key_parsers, link) {
412		pr_debug("Trying parser '%s'\n", parser->name);
413
414		ret = parser->parse(prep);
415		if (ret != -EBADMSG) {
416			pr_debug("Parser recognised the format (ret %d)\n",
417				 ret);
418			break;
419		}
420	}
421
422	up_read(&asymmetric_key_parsers_sem);
423	pr_devel("<==%s() = %d\n", __func__, ret);
424	return ret;
425}
426
427/*
428 * Clean up the key ID list
429 */
430static void asymmetric_key_free_kids(struct asymmetric_key_ids *kids)
431{
432	int i;
433
434	if (kids) {
435		for (i = 0; i < ARRAY_SIZE(kids->id); i++)
436			kfree(kids->id[i]);
437		kfree(kids);
438	}
439}
440
441/*
442 * Clean up the preparse data
443 */
444static void asymmetric_key_free_preparse(struct key_preparsed_payload *prep)
445{
446	struct asymmetric_key_subtype *subtype = prep->payload.data[asym_subtype];
447	struct asymmetric_key_ids *kids = prep->payload.data[asym_key_ids];
448
449	pr_devel("==>%s()\n", __func__);
450
451	if (subtype) {
452		subtype->destroy(prep->payload.data[asym_crypto],
453				 prep->payload.data[asym_auth]);
454		module_put(subtype->owner);
455	}
456	asymmetric_key_free_kids(kids);
457	kfree(prep->description);
458}
459
460/*
461 * dispose of the data dangling from the corpse of a asymmetric key
462 */
463static void asymmetric_key_destroy(struct key *key)
464{
465	struct asymmetric_key_subtype *subtype = asymmetric_key_subtype(key);
466	struct asymmetric_key_ids *kids = key->payload.data[asym_key_ids];
467	void *data = key->payload.data[asym_crypto];
468	void *auth = key->payload.data[asym_auth];
469
470	key->payload.data[asym_crypto] = NULL;
471	key->payload.data[asym_subtype] = NULL;
472	key->payload.data[asym_key_ids] = NULL;
473	key->payload.data[asym_auth] = NULL;
474
475	if (subtype) {
476		subtype->destroy(data, auth);
477		module_put(subtype->owner);
478	}
479
480	asymmetric_key_free_kids(kids);
481}
482
483static struct key_restriction *asymmetric_restriction_alloc(
484	key_restrict_link_func_t check,
485	struct key *key)
486{
487	struct key_restriction *keyres =
488		kzalloc(sizeof(struct key_restriction), GFP_KERNEL);
489
490	if (!keyres)
491		return ERR_PTR(-ENOMEM);
492
493	keyres->check = check;
494	keyres->key = key;
495	keyres->keytype = &key_type_asymmetric;
496
497	return keyres;
498}
499
500/*
501 * look up keyring restrict functions for asymmetric keys
502 */
503static struct key_restriction *asymmetric_lookup_restriction(
504	const char *restriction)
505{
506	char *restrict_method;
507	char *parse_buf;
508	char *next;
509	struct key_restriction *ret = ERR_PTR(-EINVAL);
510
511	if (strcmp("builtin_trusted", restriction) == 0)
512		return asymmetric_restriction_alloc(
513			restrict_link_by_builtin_trusted, NULL);
514
515	if (strcmp("builtin_and_secondary_trusted", restriction) == 0)
516		return asymmetric_restriction_alloc(
517			restrict_link_by_builtin_and_secondary_trusted, NULL);
518
519	parse_buf = kstrndup(restriction, PAGE_SIZE, GFP_KERNEL);
520	if (!parse_buf)
521		return ERR_PTR(-ENOMEM);
522
523	next = parse_buf;
524	restrict_method = strsep(&next, ":");
525
526	if ((strcmp(restrict_method, "key_or_keyring") == 0) && next) {
527		char *key_text;
528		key_serial_t serial;
529		struct key *key;
530		key_restrict_link_func_t link_fn =
531			restrict_link_by_key_or_keyring;
532		bool allow_null_key = false;
533
534		key_text = strsep(&next, ":");
535
536		if (next) {
537			if (strcmp(next, "chain") != 0)
538				goto out;
539
540			link_fn = restrict_link_by_key_or_keyring_chain;
541			allow_null_key = true;
542		}
543
544		if (kstrtos32(key_text, 0, &serial) < 0)
545			goto out;
546
547		if ((serial == 0) && allow_null_key) {
548			key = NULL;
549		} else {
550			key = key_lookup(serial);
551			if (IS_ERR(key)) {
552				ret = ERR_CAST(key);
553				goto out;
554			}
555		}
556
557		ret = asymmetric_restriction_alloc(link_fn, key);
558		if (IS_ERR(ret))
559			key_put(key);
560	}
561
562out:
563	kfree(parse_buf);
564	return ret;
565}
566
567int asymmetric_key_eds_op(struct kernel_pkey_params *params,
568			  const void *in, void *out)
569{
570	const struct asymmetric_key_subtype *subtype;
571	struct key *key = params->key;
572	int ret;
573
574	pr_devel("==>%s()\n", __func__);
575
576	if (key->type != &key_type_asymmetric)
577		return -EINVAL;
578	subtype = asymmetric_key_subtype(key);
579	if (!subtype ||
580	    !key->payload.data[0])
581		return -EINVAL;
582	if (!subtype->eds_op)
583		return -ENOTSUPP;
584
585	ret = subtype->eds_op(params, in, out);
586
587	pr_devel("<==%s() = %d\n", __func__, ret);
588	return ret;
589}
590
591static int asymmetric_key_verify_signature(struct kernel_pkey_params *params,
592					   const void *in, const void *in2)
593{
594	struct public_key_signature sig = {
595		.s_size		= params->in2_len,
596		.digest_size	= params->in_len,
597		.encoding	= params->encoding,
598		.hash_algo	= params->hash_algo,
599		.digest		= (void *)in,
600		.s		= (void *)in2,
601	};
602
603	return verify_signature(params->key, &sig);
604}
605
606struct key_type key_type_asymmetric = {
607	.name			= "asymmetric",
608	.preparse		= asymmetric_key_preparse,
609	.free_preparse		= asymmetric_key_free_preparse,
610	.instantiate		= generic_key_instantiate,
611	.match_preparse		= asymmetric_key_match_preparse,
612	.match_free		= asymmetric_key_match_free,
613	.destroy		= asymmetric_key_destroy,
614	.describe		= asymmetric_key_describe,
615	.lookup_restriction	= asymmetric_lookup_restriction,
616	.asym_query		= query_asymmetric_key,
617	.asym_eds_op		= asymmetric_key_eds_op,
618	.asym_verify_signature	= asymmetric_key_verify_signature,
619};
620EXPORT_SYMBOL_GPL(key_type_asymmetric);
621
622/**
623 * register_asymmetric_key_parser - Register a asymmetric key blob parser
624 * @parser: The parser to register
625 */
626int register_asymmetric_key_parser(struct asymmetric_key_parser *parser)
627{
628	struct asymmetric_key_parser *cursor;
629	int ret;
630
631	down_write(&asymmetric_key_parsers_sem);
632
633	list_for_each_entry(cursor, &asymmetric_key_parsers, link) {
634		if (strcmp(cursor->name, parser->name) == 0) {
635			pr_err("Asymmetric key parser '%s' already registered\n",
636			       parser->name);
637			ret = -EEXIST;
638			goto out;
639		}
640	}
641
642	list_add_tail(&parser->link, &asymmetric_key_parsers);
643
644	pr_notice("Asymmetric key parser '%s' registered\n", parser->name);
645	ret = 0;
646
647out:
648	up_write(&asymmetric_key_parsers_sem);
649	return ret;
650}
651EXPORT_SYMBOL_GPL(register_asymmetric_key_parser);
652
653/**
654 * unregister_asymmetric_key_parser - Unregister a asymmetric key blob parser
655 * @parser: The parser to unregister
656 */
657void unregister_asymmetric_key_parser(struct asymmetric_key_parser *parser)
658{
659	down_write(&asymmetric_key_parsers_sem);
660	list_del(&parser->link);
661	up_write(&asymmetric_key_parsers_sem);
662
663	pr_notice("Asymmetric key parser '%s' unregistered\n", parser->name);
664}
665EXPORT_SYMBOL_GPL(unregister_asymmetric_key_parser);
666
667/*
668 * Module stuff
669 */
670static int __init asymmetric_key_init(void)
671{
672	return register_key_type(&key_type_asymmetric);
673}
674
675static void __exit asymmetric_key_cleanup(void)
676{
677	unregister_key_type(&key_type_asymmetric);
678}
679
680module_init(asymmetric_key_init);
681module_exit(asymmetric_key_cleanup);