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Linux/crypto/asymmetric_keys/asymmetric_type.c

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

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