security/keys/request_key.c

   1 /* Request a key from userspace
   2  *
   3  * Copyright (C) 2004-2007 Red Hat, Inc. All Rights Reserved.
   4  * Written by David Howells (dhowells@redhat.com)
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public License
   8  * as published by the Free Software Foundation; either version
   9  * 2 of the License, or (at your option) any later version.
  10  *
  11  * See Documentation/keys-request-key.txt
  12  */
  13
  14 #include <linux/module.h>
  15 #include <linux/sched.h>
  16 #include <linux/kmod.h>
  17 #include <linux/err.h>
  18 #include <linux/keyctl.h>
  19 #include <linux/slab.h>
  20 #include "internal.h"
  21
  22 #define key_negative_timeout    60      /* default timeout on a negative key's existence */
  23
  24 /*
  25  * wait_on_bit() sleep function for uninterruptible waiting
  26  */
  27 static int key_wait_bit(void *flags)
  28 {
  29         schedule();
  30         return 0;
  31 }
  32
  33 /*
  34  * wait_on_bit() sleep function for interruptible waiting
  35  */
  36 static int key_wait_bit_intr(void *flags)
  37 {
  38         schedule();
  39         return signal_pending(current) ? -ERESTARTSYS : 0;
  40 }
  41
  42 /*
  43  * call to complete the construction of a key
  44  */
  45 void complete_request_key(struct key_construction *cons, int error)
  46 {
  47         kenter("{%d,%d},%d", cons->key->serial, cons->authkey->serial, error);
  48
  49         if (error < 0)
  50                 key_negate_and_link(cons->key, key_negative_timeout, NULL,
  51                                     cons->authkey);
  52         else
  53                 key_revoke(cons->authkey);
  54
  55         key_put(cons->key);
  56         key_put(cons->authkey);
  57         kfree(cons);
  58 }
  59 EXPORT_SYMBOL(complete_request_key);
  60
  61 /*
  62  * request userspace finish the construction of a key
  63  * - execute "/sbin/request-key <op> <key> <uid> <gid> <keyring> <keyring> <keyring>"
  64  */
  65 static int call_sbin_request_key(struct key_construction *cons,
  66                                  const char *op,
  67                                  void *aux)
  68 {
  69         struct task_struct *tsk = current;
  70         key_serial_t prkey, sskey;
  71         struct key *key = cons->key, *authkey = cons->authkey, *keyring;
  72         char *argv[9], *envp[3], uid_str[12], gid_str[12];
  73         char key_str[12], keyring_str[3][12];
  74         char desc[20];
  75         int ret, i;
  76
  77         kenter("{%d},{%d},%s", key->serial, authkey->serial, op);
  78
  79         ret = install_user_keyrings();
  80         if (ret < 0)
  81                 goto error_alloc;
  82
  83         /* allocate a new session keyring */
  84         sprintf(desc, "_req.%u", key->serial);
  85
  86         keyring = keyring_alloc(desc, current_fsuid(), current_fsgid(), current,
  87                                 KEY_ALLOC_QUOTA_OVERRUN, NULL);
  88         if (IS_ERR(keyring)) {
  89                 ret = PTR_ERR(keyring);
  90                 goto error_alloc;
  91         }
  92
  93         /* attach the auth key to the session keyring */
  94         ret = __key_link(keyring, authkey);
  95         if (ret < 0)
  96                 goto error_link;
  97
  98         /* record the UID and GID */
  99         sprintf(uid_str, "%d", current_fsuid());
 100         sprintf(gid_str, "%d", current_fsgid());
 101
 102         /* we say which key is under construction */
 103         sprintf(key_str, "%d", key->serial);
 104
 105         /* we specify the process's default keyrings */
 106         sprintf(keyring_str[0], "%d",
 107                 tsk->cred->thread_keyring ?
 108                 tsk->cred->thread_keyring->serial : 0);
 109
 110         prkey = 0;
 111         if (tsk->signal->process_keyring)
 112                 prkey = tsk->signal->process_keyring->serial;
 113
 114         sprintf(keyring_str[1], "%d", prkey);
 115
 116         if (tsk->signal->session_keyring) {
 117                 rcu_read_lock();
 118                 sskey = rcu_dereference(tsk->signal->session_keyring)->serial;
 119                 rcu_read_unlock();
 120         } else {
 121                 sskey = tsk->cred->user->session_keyring->serial;
 122         }
 123
 124         sprintf(keyring_str[2], "%d", sskey);
 125
 126         /* set up a minimal environment */
 127         i = 0;
 128         envp[i++] = "HOME=/";
 129         envp[i++] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
 130         envp[i] = NULL;
 131
 132         /* set up the argument list */
 133         i = 0;
 134         argv[i++] = "/sbin/request-key";
 135         argv[i++] = (char *) op;
 136         argv[i++] = key_str;
 137         argv[i++] = uid_str;
 138         argv[i++] = gid_str;
 139         argv[i++] = keyring_str[0];
 140         argv[i++] = keyring_str[1];
 141         argv[i++] = keyring_str[2];
 142         argv[i] = NULL;
 143
 144         /* do it */
 145         ret = call_usermodehelper_keys(argv[0], argv, envp, keyring,
 146                                        UMH_WAIT_PROC);
 147         kdebug("usermode -> 0x%x", ret);
 148         if (ret >= 0) {
 149                 /* ret is the exit/wait code */
 150                 if (test_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags) ||
 151                     key_validate(key) < 0)
 152                         ret = -ENOKEY;
 153                 else
 154                         /* ignore any errors from userspace if the key was
 155                          * instantiated */
 156                         ret = 0;
 157         }
 158
 159 error_link:
 160         key_put(keyring);
 161
 162 error_alloc:
 163         kleave(" = %d", ret);
 164         complete_request_key(cons, ret);
 165         return ret;
 166 }
 167
 168 /*
 169  * call out to userspace for key construction
 170  * - we ignore program failure and go on key status instead
 171  */
 172 static int construct_key(struct key *key, const void *callout_info,
 173                          size_t callout_len, void *aux,
 174                          struct key *dest_keyring)
 175 {
 176         struct key_construction *cons;
 177         request_key_actor_t actor;
 178         struct key *authkey;
 179         int ret;
 180
 181         kenter("%d,%p,%zu,%p", key->serial, callout_info, callout_len, aux);
 182
 183         cons = kmalloc(sizeof(*cons), GFP_KERNEL);
 184         if (!cons)
 185                 return -ENOMEM;
 186
 187         /* allocate an authorisation key */
 188         authkey = request_key_auth_new(key, callout_info, callout_len,
 189                                        dest_keyring);
 190         if (IS_ERR(authkey)) {
 191                 kfree(cons);
 192                 ret = PTR_ERR(authkey);
 193                 authkey = NULL;
 194         } else {
 195                 cons->authkey = key_get(authkey);
 196                 cons->key = key_get(key);
 197
 198                 /* make the call */
 199                 actor = call_sbin_request_key;
 200                 if (key->type->request_key)
 201                         actor = key->type->request_key;
 202
 203                 ret = actor(cons, "create", aux);
 204
 205                 /* check that the actor called complete_request_key() prior to
 206                  * returning an error */
 207                 WARN_ON(ret < 0 &&
 208                         !test_bit(KEY_FLAG_REVOKED, &authkey->flags));
 209                 key_put(authkey);
 210         }
 211
 212         kleave(" = %d", ret);
 213         return ret;
 214 }
 215
 216 /*
 217  * get the appropriate destination keyring for the request
 218  * - we return whatever keyring we select with an extra reference upon it which
 219  *   the caller must release
 220  */
 221 static void construct_get_dest_keyring(struct key **_dest_keyring)
 222 {
 223         struct request_key_auth *rka;
 224         struct task_struct *tsk = current;
 225         struct key *dest_keyring = *_dest_keyring, *authkey;
 226
 227         kenter("%p", dest_keyring);
 228
 229         /* find the appropriate keyring */
 230         if (dest_keyring) {
 231                 /* the caller supplied one */
 232                 key_get(dest_keyring);
 233         } else {
 234                 /* use a default keyring; falling through the cases until we
 235                  * find one that we actually have */
 236                 switch (tsk->cred->jit_keyring) {
 237                 case KEY_REQKEY_DEFL_DEFAULT:
 238                 case KEY_REQKEY_DEFL_REQUESTOR_KEYRING:
 239                         if (tsk->cred->request_key_auth) {
 240                                 authkey = tsk->cred->request_key_auth;
 241                                 down_read(&authkey->sem);
 242                                 rka = authkey->payload.data;
 243                                 if (!test_bit(KEY_FLAG_REVOKED,
 244                                               &authkey->flags))
 245                                         dest_keyring =
 246                                                 key_get(rka->dest_keyring);
 247                                 up_read(&authkey->sem);
 248                                 if (dest_keyring)
 249                                         break;
 250                         }
 251
 252                 case KEY_REQKEY_DEFL_THREAD_KEYRING:
 253                         dest_keyring = key_get(tsk->cred->thread_keyring);
 254                         if (dest_keyring)
 255                                 break;
 256
 257                 case KEY_REQKEY_DEFL_PROCESS_KEYRING:
 258                         dest_keyring = key_get(tsk->signal->process_keyring);
 259                         if (dest_keyring)
 260                                 break;
 261
 262                 case KEY_REQKEY_DEFL_SESSION_KEYRING:
 263                         rcu_read_lock();
 264                         dest_keyring = key_get(
 265                                 rcu_dereference(tsk->signal->session_keyring));
 266                         rcu_read_unlock();
 267
 268                         if (dest_keyring)
 269                                 break;
 270
 271                 case KEY_REQKEY_DEFL_USER_SESSION_KEYRING:
 272                         dest_keyring =
 273                                 key_get(tsk->cred->user->session_keyring);
 274                         break;
 275
 276                 case KEY_REQKEY_DEFL_USER_KEYRING:
 277                         dest_keyring = key_get(tsk->cred->user->uid_keyring);
 278                         break;
 279
 280                 case KEY_REQKEY_DEFL_GROUP_KEYRING:
 281                 default:
 282                         BUG();
 283                 }
 284         }
 285
 286         *_dest_keyring = dest_keyring;
 287         kleave(" [dk %d]", key_serial(dest_keyring));
 288         return;
 289 }
 290
 291 /*
 292  * allocate a new key in under-construction state and attempt to link it in to
 293  * the requested place
 294  * - may return a key that's already under construction instead
 295  */
 296 static int construct_alloc_key(struct key_type *type,
 297                                const char *description,
 298                                struct key *dest_keyring,
 299                                unsigned long flags,
 300                                struct key_user *user,
 301                                struct key **_key)
 302 {
 303         struct key *key;
 304         key_ref_t key_ref;
 305
 306         kenter("%s,%s,,,", type->name, description);
 307
 308         mutex_lock(&user->cons_lock);
 309
 310         key = key_alloc(type, description,
 311                         current_fsuid(), current_fsgid(), current, KEY_POS_ALL,
 312                         flags);
 313         if (IS_ERR(key))
 314                 goto alloc_failed;
 315
 316         set_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags);
 317
 318         down_write(&dest_keyring->sem);
 319
 320         /* attach the key to the destination keyring under lock, but we do need
 321          * to do another check just in case someone beat us to it whilst we
 322          * waited for locks */
 323         mutex_lock(&key_construction_mutex);
 324
 325         key_ref = search_process_keyrings(type, description, type->match,
 326                                           current);
 327         if (!IS_ERR(key_ref))
 328                 goto key_already_present;
 329
 330         __key_link(dest_keyring, key);
 331
 332         mutex_unlock(&key_construction_mutex);
 333         up_write(&dest_keyring->sem);
 334         mutex_unlock(&user->cons_lock);
 335         *_key = key;
 336         kleave(" = 0 [%d]", key_serial(key));
 337         return 0;
 338
 339 key_already_present:
 340         mutex_unlock(&key_construction_mutex);
 341         if (dest_keyring)
 342                 up_write(&dest_keyring->sem);
 343         mutex_unlock(&user->cons_lock);
 344         key_put(key);
 345         *_key = key = key_ref_to_ptr(key_ref);
 346         kleave(" = -EINPROGRESS [%d]", key_serial(key));
 347         return -EINPROGRESS;
 348
 349 alloc_failed:
 350         mutex_unlock(&user->cons_lock);
 351         *_key = NULL;
 352         kleave(" = %ld", PTR_ERR(key));
 353         return PTR_ERR(key);
 354 }
 355
 356 /*
 357  * commence key construction
 358  */
 359 static struct key *construct_key_and_link(struct key_type *type,
 360                                           const char *description,
 361                                           const char *callout_info,
 362                                           size_t callout_len,
 363                                           void *aux,
 364                                           struct key *dest_keyring,
 365                                           unsigned long flags)
 366 {
 367         struct key_user *user;
 368         struct key *key;
 369         int ret;
 370
 371         user = key_user_lookup(current_fsuid());
 372         if (!user)
 373                 return ERR_PTR(-ENOMEM);
 374
 375         construct_get_dest_keyring(&dest_keyring);
 376
 377         ret = construct_alloc_key(type, description, dest_keyring, flags, user,
 378                                   &key);
 379         key_user_put(user);
 380
 381         if (ret == 0) {
 382                 ret = construct_key(key, callout_info, callout_len, aux,
 383                                     dest_keyring);
 384                 if (ret < 0)
 385                         goto construction_failed;
 386         }
 387
 388         key_put(dest_keyring);
 389         return key;
 390
 391 construction_failed:
 392         key_negate_and_link(key, key_negative_timeout, NULL, NULL);
 393         key_put(key);
 394         key_put(dest_keyring);
 395         return ERR_PTR(ret);
 396 }
 397
 398 /*
 399  * request a key
 400  * - search the process's keyrings
 401  * - check the list of keys being created or updated
 402  * - call out to userspace for a key if supplementary info was provided
 403  * - cache the key in an appropriate keyring
 404  */
 405 struct key *request_key_and_link(struct key_type *type,
 406                                  const char *description,
 407                                  const void *callout_info,
 408                                  size_t callout_len,
 409                                  void *aux,
 410                                  struct key *dest_keyring,
 411                                  unsigned long flags)
 412 {
 413         struct key *key;
 414         key_ref_t key_ref;
 415
 416         kenter("%s,%s,%p,%zu,%p,%p,%lx",
 417                type->name, description, callout_info, callout_len, aux,
 418                dest_keyring, flags);
 419
 420         /* search all the process keyrings for a key */
 421         key_ref = search_process_keyrings(type, description, type->match,
 422                                           current);
 423
 424         if (!IS_ERR(key_ref)) {
 425                 key = key_ref_to_ptr(key_ref);
 426         } else if (PTR_ERR(key_ref) != -EAGAIN) {
 427                 key = ERR_CAST(key_ref);
 428         } else  {
 429                 /* the search failed, but the keyrings were searchable, so we
 430                  * should consult userspace if we can */
 431                 key = ERR_PTR(-ENOKEY);
 432                 if (!callout_info)
 433                         goto error;
 434
 435                 key = construct_key_and_link(type, description, callout_info,
 436                                              callout_len, aux, dest_keyring,
 437                                              flags);
 438         }
 439
 440 error:
 441         kleave(" = %p", key);
 442         return key;
 443 }
 444
 445 /*
 446  * wait for construction of a key to complete
 447  */
 448 int wait_for_key_construction(struct key *key, bool intr)
 449 {
 450         int ret;
 451
 452         ret = wait_on_bit(&key->flags, KEY_FLAG_USER_CONSTRUCT,
 453                           intr ? key_wait_bit_intr : key_wait_bit,
 454                           intr ? TASK_INTERRUPTIBLE : TASK_UNINTERRUPTIBLE);
 455         if (ret < 0)
 456                 return ret;
 457         return key_validate(key);
 458 }
 459 EXPORT_SYMBOL(wait_for_key_construction);
 460
 461 /*
 462  * request a key
 463  * - search the process's keyrings
 464  * - check the list of keys being created or updated
 465  * - call out to userspace for a key if supplementary info was provided
 466  * - waits uninterruptible for creation to complete
 467  */
 468 struct key *request_key(struct key_type *type,
 469                         const char *description,
 470                         const char *callout_info)
 471 {
 472         struct key *key;
 473         size_t callout_len = 0;
 474         int ret;
 475
 476         if (callout_info)
 477                 callout_len = strlen(callout_info);
 478         key = request_key_and_link(type, description, callout_info, callout_len,
 479                                    NULL, NULL, KEY_ALLOC_IN_QUOTA);
 480         if (!IS_ERR(key)) {
 481                 ret = wait_for_key_construction(key, false);
 482                 if (ret < 0) {
 483                         key_put(key);
 484                         return ERR_PTR(ret);
 485                 }
 486         }
 487         return key;
 488 }
 489 EXPORT_SYMBOL(request_key);
 490
 491 /*
 492  * request a key with auxiliary data for the upcaller
 493  * - search the process's keyrings
 494  * - check the list of keys being created or updated
 495  * - call out to userspace for a key if supplementary info was provided
 496  * - waits uninterruptible for creation to complete
 497  */
 498 struct key *request_key_with_auxdata(struct key_type *type,
 499                                      const char *description,
 500                                      const void *callout_info,
 501                                      size_t callout_len,
 502                                      void *aux)
 503 {
 504         struct key *key;
 505         int ret;
 506
 507         key = request_key_and_link(type, description, callout_info, callout_len,
 508                                    aux, NULL, KEY_ALLOC_IN_QUOTA);
 509         if (!IS_ERR(key)) {
 510                 ret = wait_for_key_construction(key, false);
 511                 if (ret < 0) {
 512                         key_put(key);
 513                         return ERR_PTR(ret);
 514                 }
 515         }
 516         return key;
 517 }
 518 EXPORT_SYMBOL(request_key_with_auxdata);
 519
 520 /*
 521  * request a key (allow async construction)
 522  * - search the process's keyrings
 523  * - check the list of keys being created or updated
 524  * - call out to userspace for a key if supplementary info was provided
 525  */
 526 struct key *request_key_async(struct key_type *type,
 527                               const char *description,
 528                               const void *callout_info,
 529                               size_t callout_len)
 530 {
 531         return request_key_and_link(type, description, callout_info,
 532                                     callout_len, NULL, NULL,
 533                                     KEY_ALLOC_IN_QUOTA);
 534 }
 535 EXPORT_SYMBOL(request_key_async);
 536
 537 /*
 538  * request a key with auxiliary data for the upcaller (allow async construction)
 539  * - search the process's keyrings
 540  * - check the list of keys being created or updated
 541  * - call out to userspace for a key if supplementary info was provided
 542  */
 543 struct key *request_key_async_with_auxdata(struct key_type *type,
 544                                            const char *description,
 545                                            const void *callout_info,
 546                                            size_t callout_len,
 547                                            void *aux)
 548 {
 549         return request_key_and_link(type, description, callout_info,
 550                                     callout_len, aux, NULL, KEY_ALLOC_IN_QUOTA);
 551 }
 552 EXPORT_SYMBOL(request_key_async_with_auxdata);