crypto/asymmetric_keys/asymmetric_type.c

   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 <linux/seq_file.h>
  16 #include <linux/module.h>
  17 #include <linux/slab.h>
  18 #include <linux/ctype.h>
  19 #include "asymmetric_keys.h"
  20
  21 MODULE_LICENSE("GPL");
  22
  23 static LIST_HEAD(asymmetric_key_parsers);
  24 static DECLARE_RWSEM(asymmetric_key_parsers_sem);
  25
  26 /**
  27  * asymmetric_key_generate_id: Construct an asymmetric key ID
  28  * @val_1: First binary blob
  29  * @len_1: Length of first binary blob
  30  * @val_2: Second binary blob
  31  * @len_2: Length of second binary blob
  32  *
  33  * Construct an asymmetric key ID from a pair of binary blobs.
  34  */
  35 struct asymmetric_key_id *asymmetric_key_generate_id(const void *val_1,
  36                                                      size_t len_1,
  37                                                      const void *val_2,
  38                                                      size_t len_2)
  39 {
  40         struct asymmetric_key_id *kid;
  41
  42         kid = kmalloc(sizeof(struct asymmetric_key_id) + len_1 + len_2,
  43                       GFP_KERNEL);
  44         if (!kid)
  45                 return ERR_PTR(-ENOMEM);
  46         kid->len = len_1 + len_2;
  47         memcpy(kid->data, val_1, len_1);
  48         memcpy(kid->data + len_1, val_2, len_2);
  49         return kid;
  50 }
  51 EXPORT_SYMBOL_GPL(asymmetric_key_generate_id);
  52
  53 /**
  54  * asymmetric_key_id_same - Return true if two asymmetric keys IDs are the same.
  55  * @kid_1, @kid_2: The key IDs to compare
  56  */
  57 bool asymmetric_key_id_same(const struct asymmetric_key_id *kid1,
  58                             const struct asymmetric_key_id *kid2)
  59 {
  60         if (!kid1 || !kid2)
  61                 return false;
  62         if (kid1->len != kid2->len)
  63                 return false;
  64         return memcmp(kid1->data, kid2->data, kid1->len) == 0;
  65 }
  66 EXPORT_SYMBOL_GPL(asymmetric_key_id_same);
  67
  68 /**
  69  * asymmetric_key_id_partial - Return true if two asymmetric keys IDs
  70  * partially match
  71  * @kid_1, @kid_2: The key IDs to compare
  72  */
  73 bool asymmetric_key_id_partial(const struct asymmetric_key_id *kid1,
  74                                const struct asymmetric_key_id *kid2)
  75 {
  76         if (!kid1 || !kid2)
  77                 return false;
  78         if (kid1->len < kid2->len)
  79                 return false;
  80         return memcmp(kid1->data + (kid1->len - kid2->len),
  81                       kid2->data, kid2->len) == 0;
  82 }
  83 EXPORT_SYMBOL_GPL(asymmetric_key_id_partial);
  84
  85 /**
  86  * asymmetric_match_key_ids - Search asymmetric key IDs
  87  * @kids: The list of key IDs to check
  88  * @match_id: The key ID we're looking for
  89  * @match: The match function to use
  90  */
  91 static bool asymmetric_match_key_ids(
  92         const struct asymmetric_key_ids *kids,
  93         const struct asymmetric_key_id *match_id,
  94         bool (*match)(const struct asymmetric_key_id *kid1,
  95                       const struct asymmetric_key_id *kid2))
  96 {
  97         int i;
  98
  99         if (!kids || !match_id)
 100                 return false;
 101         for (i = 0; i < ARRAY_SIZE(kids->id); i++)
 102                 if (match(kids->id[i], match_id))
 103                         return true;
 104         return false;
 105 }
 106
 107 /* helper function can be called directly with pre-allocated memory */
 108 inline int __asymmetric_key_hex_to_key_id(const char *id,
 109                                    struct asymmetric_key_id *match_id,
 110                                    size_t hexlen)
 111 {
 112         match_id->len = hexlen;
 113         return hex2bin(match_id->data, id, hexlen);
 114 }
 115
 116 /**
 117  * asymmetric_key_hex_to_key_id - Convert a hex string into a key ID.
 118  * @id: The ID as a hex string.
 119  */
 120 struct asymmetric_key_id *asymmetric_key_hex_to_key_id(const char *id)
 121 {
 122         struct asymmetric_key_id *match_id;
 123         size_t asciihexlen;
 124         int ret;
 125
 126         if (!*id)
 127                 return ERR_PTR(-EINVAL);
 128         asciihexlen = strlen(id);
 129         if (asciihexlen & 1)
 130                 return ERR_PTR(-EINVAL);
 131
 132         match_id = kmalloc(sizeof(struct asymmetric_key_id) + asciihexlen / 2,
 133                            GFP_KERNEL);
 134         if (!match_id)
 135                 return ERR_PTR(-ENOMEM);
 136         ret = __asymmetric_key_hex_to_key_id(id, match_id, asciihexlen / 2);
 137         if (ret < 0) {
 138                 kfree(match_id);
 139                 return ERR_PTR(-EINVAL);
 140         }
 141         return match_id;
 142 }
 143
 144 /*
 145  * Match asymmetric keys by an exact match on an ID.
 146  */
 147 static bool asymmetric_key_cmp(const struct key *key,
 148                                const struct key_match_data *match_data)
 149 {
 150         const struct asymmetric_key_ids *kids = asymmetric_key_ids(key);
 151         const struct asymmetric_key_id *match_id = match_data->preparsed;
 152
 153         return asymmetric_match_key_ids(kids, match_id,
 154                                         asymmetric_key_id_same);
 155 }
 156
 157 /*
 158  * Match asymmetric keys by a partial match on an IDs.
 159  */
 160 static bool asymmetric_key_cmp_partial(const struct key *key,
 161                                        const struct key_match_data *match_data)
 162 {
 163         const struct asymmetric_key_ids *kids = asymmetric_key_ids(key);
 164         const struct asymmetric_key_id *match_id = match_data->preparsed;
 165
 166         return asymmetric_match_key_ids(kids, match_id,
 167                                         asymmetric_key_id_partial);
 168 }
 169
 170 /*
 171  * Preparse the match criterion.  If we don't set lookup_type and cmp,
 172  * the default will be an exact match on the key description.
 173  *
 174  * There are some specifiers for matching key IDs rather than by the key
 175  * description:
 176  *
 177  *      "id:<id>" - find a key by partial match on any available ID
 178  *      "ex:<id>" - find a key by exact match on any available ID
 179  *
 180  * These have to be searched by iteration rather than by direct lookup because
 181  * the key is hashed according to its description.
 182  */
 183 static int asymmetric_key_match_preparse(struct key_match_data *match_data)
 184 {
 185         struct asymmetric_key_id *match_id;
 186         const char *spec = match_data->raw_data;
 187         const char *id;
 188         bool (*cmp)(const struct key *, const struct key_match_data *) =
 189                 asymmetric_key_cmp;
 190
 191         if (!spec || !*spec)
 192                 return -EINVAL;
 193         if (spec[0] == 'i' &&
 194             spec[1] == 'd' &&
 195             spec[2] == ':') {
 196                 id = spec + 3;
 197                 cmp = asymmetric_key_cmp_partial;
 198         } else if (spec[0] == 'e' &&
 199                    spec[1] == 'x' &&
 200                    spec[2] == ':') {
 201                 id = spec + 3;
 202         } else {
 203                 goto default_match;
 204         }
 205
 206         match_id = asymmetric_key_hex_to_key_id(id);
 207         if (IS_ERR(match_id))
 208                 return PTR_ERR(match_id);
 209
 210         match_data->preparsed = match_id;
 211         match_data->cmp = cmp;
 212         match_data->lookup_type = KEYRING_SEARCH_LOOKUP_ITERATE;
 213         return 0;
 214
 215 default_match:
 216         return 0;
 217 }
 218
 219 /*
 220  * Free the preparsed the match criterion.
 221  */
 222 static void asymmetric_key_match_free(struct key_match_data *match_data)
 223 {
 224         kfree(match_data->preparsed);
 225 }
 226
 227 /*
 228  * Describe the asymmetric key
 229  */
 230 static void asymmetric_key_describe(const struct key *key, struct seq_file *m)
 231 {
 232         const struct asymmetric_key_subtype *subtype = asymmetric_key_subtype(key);
 233         const struct asymmetric_key_ids *kids = asymmetric_key_ids(key);
 234         const struct asymmetric_key_id *kid;
 235         const unsigned char *p;
 236         int n;
 237
 238         seq_puts(m, key->description);
 239
 240         if (subtype) {
 241                 seq_puts(m, ": ");
 242                 subtype->describe(key, m);
 243
 244                 if (kids && kids->id[1]) {
 245                         kid = kids->id[1];
 246                         seq_putc(m, ' ');
 247                         n = kid->len;
 248                         p = kid->data;
 249                         if (n > 4) {
 250                                 p += n - 4;
 251                                 n = 4;
 252                         }
 253                         seq_printf(m, "%*phN", n, p);
 254                 }
 255
 256                 seq_puts(m, " [");
 257                 /* put something here to indicate the key's capabilities */
 258                 seq_putc(m, ']');
 259         }
 260 }
 261
 262 /*
 263  * Preparse a asymmetric payload to get format the contents appropriately for the
 264  * internal payload to cut down on the number of scans of the data performed.
 265  *
 266  * We also generate a proposed description from the contents of the key that
 267  * can be used to name the key if the user doesn't want to provide one.
 268  */
 269 static int asymmetric_key_preparse(struct key_preparsed_payload *prep)
 270 {
 271         struct asymmetric_key_parser *parser;
 272         int ret;
 273
 274         pr_devel("==>%s()\n", __func__);
 275
 276         if (prep->datalen == 0)
 277                 return -EINVAL;
 278
 279         down_read(&asymmetric_key_parsers_sem);
 280
 281         ret = -EBADMSG;
 282         list_for_each_entry(parser, &asymmetric_key_parsers, link) {
 283                 pr_debug("Trying parser '%s'\n", parser->name);
 284
 285                 ret = parser->parse(prep);
 286                 if (ret != -EBADMSG) {
 287                         pr_debug("Parser recognised the format (ret %d)\n",
 288                                  ret);
 289                         break;
 290                 }
 291         }
 292
 293         up_read(&asymmetric_key_parsers_sem);
 294         pr_devel("<==%s() = %d\n", __func__, ret);
 295         return ret;
 296 }
 297
 298 /*
 299  * Clean up the preparse data
 300  */
 301 static void asymmetric_key_free_preparse(struct key_preparsed_payload *prep)
 302 {
 303         struct asymmetric_key_subtype *subtype = prep->type_data[0];
 304         struct asymmetric_key_ids *kids = prep->type_data[1];
 305         int i;
 306
 307         pr_devel("==>%s()\n", __func__);
 308
 309         if (subtype) {
 310                 subtype->destroy(prep->payload[0]);
 311                 module_put(subtype->owner);
 312         }
 313         if (kids) {
 314                 for (i = 0; i < ARRAY_SIZE(kids->id); i++)
 315                         kfree(kids->id[i]);
 316                 kfree(kids);
 317         }
 318         kfree(prep->description);
 319 }
 320
 321 /*
 322  * dispose of the data dangling from the corpse of a asymmetric key
 323  */
 324 static void asymmetric_key_destroy(struct key *key)
 325 {
 326         struct asymmetric_key_subtype *subtype = asymmetric_key_subtype(key);
 327         struct asymmetric_key_ids *kids = key->type_data.p[1];
 328
 329         if (subtype) {
 330                 subtype->destroy(key->payload.data);
 331                 module_put(subtype->owner);
 332                 key->type_data.p[0] = NULL;
 333         }
 334
 335         if (kids) {
 336                 kfree(kids->id[0]);
 337                 kfree(kids->id[1]);
 338                 kfree(kids);
 339                 key->type_data.p[1] = NULL;
 340         }
 341 }
 342
 343 struct key_type key_type_asymmetric = {
 344         .name           = "asymmetric",
 345         .preparse       = asymmetric_key_preparse,
 346         .free_preparse  = asymmetric_key_free_preparse,
 347         .instantiate    = generic_key_instantiate,
 348         .match_preparse = asymmetric_key_match_preparse,
 349         .match_free     = asymmetric_key_match_free,
 350         .destroy        = asymmetric_key_destroy,
 351         .describe       = asymmetric_key_describe,
 352 };
 353 EXPORT_SYMBOL_GPL(key_type_asymmetric);
 354
 355 /**
 356  * register_asymmetric_key_parser - Register a asymmetric key blob parser
 357  * @parser: The parser to register
 358  */
 359 int register_asymmetric_key_parser(struct asymmetric_key_parser *parser)
 360 {
 361         struct asymmetric_key_parser *cursor;
 362         int ret;
 363
 364         down_write(&asymmetric_key_parsers_sem);
 365
 366         list_for_each_entry(cursor, &asymmetric_key_parsers, link) {
 367                 if (strcmp(cursor->name, parser->name) == 0) {
 368                         pr_err("Asymmetric key parser '%s' already registered\n",
 369                                parser->name);
 370                         ret = -EEXIST;
 371                         goto out;
 372                 }
 373         }
 374
 375         list_add_tail(&parser->link, &asymmetric_key_parsers);
 376
 377         pr_notice("Asymmetric key parser '%s' registered\n", parser->name);
 378         ret = 0;
 379
 380 out:
 381         up_write(&asymmetric_key_parsers_sem);
 382         return ret;
 383 }
 384 EXPORT_SYMBOL_GPL(register_asymmetric_key_parser);
 385
 386 /**
 387  * unregister_asymmetric_key_parser - Unregister a asymmetric key blob parser
 388  * @parser: The parser to unregister
 389  */
 390 void unregister_asymmetric_key_parser(struct asymmetric_key_parser *parser)
 391 {
 392         down_write(&asymmetric_key_parsers_sem);
 393         list_del(&parser->link);
 394         up_write(&asymmetric_key_parsers_sem);
 395
 396         pr_notice("Asymmetric key parser '%s' unregistered\n", parser->name);
 397 }
 398 EXPORT_SYMBOL_GPL(unregister_asymmetric_key_parser);
 399
 400 /*
 401  * Module stuff
 402  */
 403 static int __init asymmetric_key_init(void)
 404 {
 405         return register_key_type(&key_type_asymmetric);
 406 }
 407
 408 static void __exit asymmetric_key_cleanup(void)
 409 {
 410         unregister_key_type(&key_type_asymmetric);
 411 }
 412
 413 module_init(asymmetric_key_init);
 414 module_exit(asymmetric_key_cleanup);