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 static int umh_keys_init(struct subprocess_info *info)
  62 {
  63         struct cred *cred = (struct cred*)current_cred();
  64         struct key *keyring = info->data;
  65         /*
  66          * This is called in context of freshly forked kthread before
  67          * kernel_execve(), we can just change our ->session_keyring.
  68          */
  69         return install_session_keyring_to_cred(cred, keyring);
  70 }
  71
  72 static void umh_keys_cleanup(struct subprocess_info *info)
  73 {
  74         struct key *keyring = info->data;
  75         key_put(keyring);
  76 }
  77
  78 static int call_usermodehelper_keys(char *path, char **argv, char **envp,
  79                          struct key *session_keyring, enum umh_wait wait)
  80 {
  81         gfp_t gfp_mask = (wait == UMH_NO_WAIT) ? GFP_ATOMIC : GFP_KERNEL;
  82         struct subprocess_info *info =
  83                 call_usermodehelper_setup(path, argv, envp, gfp_mask);
  84
  85         if (!info)
  86                 return -ENOMEM;
  87
  88         call_usermodehelper_setfns(info, umh_keys_init, umh_keys_cleanup,
  89                                         key_get(session_keyring));
  90         return call_usermodehelper_exec(info, wait);
  91 }
  92
  93 /*
  94  * request userspace finish the construction of a key
  95  * - execute "/sbin/request-key <op> <key> <uid> <gid> <keyring> <keyring> <keyring>"
  96  */
  97 static int call_sbin_request_key(struct key_construction *cons,
  98                                  const char *op,
  99                                  void *aux)
 100 {
 101         const struct cred *cred = current_cred();
 102         key_serial_t prkey, sskey;
 103         struct key *key = cons->key, *authkey = cons->authkey, *keyring,
 104                 *session;
 105         char *argv[9], *envp[3], uid_str[12], gid_str[12];
 106         char key_str[12], keyring_str[3][12];
 107         char desc[20];
 108         int ret, i;
 109
 110         kenter("{%d},{%d},%s", key->serial, authkey->serial, op);
 111
 112         ret = install_user_keyrings();
 113         if (ret < 0)
 114                 goto error_alloc;
 115
 116         /* allocate a new session keyring */
 117         sprintf(desc, "_req.%u", key->serial);
 118
 119         cred = get_current_cred();
 120         keyring = keyring_alloc(desc, cred->fsuid, cred->fsgid, cred,
 121                                 KEY_ALLOC_QUOTA_OVERRUN, NULL);
 122         put_cred(cred);
 123         if (IS_ERR(keyring)) {
 124                 ret = PTR_ERR(keyring);
 125                 goto error_alloc;
 126         }
 127
 128         /* attach the auth key to the session keyring */
 129         ret = key_link(keyring, authkey);
 130         if (ret < 0)
 131                 goto error_link;
 132
 133         /* record the UID and GID */
 134         sprintf(uid_str, "%d", cred->fsuid);
 135         sprintf(gid_str, "%d", cred->fsgid);
 136
 137         /* we say which key is under construction */
 138         sprintf(key_str, "%d", key->serial);
 139
 140         /* we specify the process's default keyrings */
 141         sprintf(keyring_str[0], "%d",
 142                 cred->thread_keyring ? cred->thread_keyring->serial : 0);
 143
 144         prkey = 0;
 145         if (cred->tgcred->process_keyring)
 146                 prkey = cred->tgcred->process_keyring->serial;
 147
 148         rcu_read_lock();
 149         session = rcu_dereference(cred->tgcred->session_keyring);
 150         if (!session)
 151                 session = cred->user->session_keyring;
 152         sskey = session->serial;
 153         rcu_read_unlock();
 154
 155         sprintf(keyring_str[2], "%d", sskey);
 156
 157         /* set up a minimal environment */
 158         i = 0;
 159         envp[i++] = "HOME=/";
 160         envp[i++] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
 161         envp[i] = NULL;
 162
 163         /* set up the argument list */
 164         i = 0;
 165         argv[i++] = "/sbin/request-key";
 166         argv[i++] = (char *) op;
 167         argv[i++] = key_str;
 168         argv[i++] = uid_str;
 169         argv[i++] = gid_str;
 170         argv[i++] = keyring_str[0];
 171         argv[i++] = keyring_str[1];
 172         argv[i++] = keyring_str[2];
 173         argv[i] = NULL;
 174
 175         /* do it */
 176         ret = call_usermodehelper_keys(argv[0], argv, envp, keyring,
 177                                        UMH_WAIT_PROC);
 178         kdebug("usermode -> 0x%x", ret);
 179         if (ret >= 0) {
 180                 /* ret is the exit/wait code */
 181                 if (test_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags) ||
 182                     key_validate(key) < 0)
 183                         ret = -ENOKEY;
 184                 else
 185                         /* ignore any errors from userspace if the key was
 186                          * instantiated */
 187                         ret = 0;
 188         }
 189
 190 error_link:
 191         key_put(keyring);
 192
 193 error_alloc:
 194         complete_request_key(cons, ret);
 195         kleave(" = %d", ret);
 196         return ret;
 197 }
 198
 199 /*
 200  * call out to userspace for key construction
 201  * - we ignore program failure and go on key status instead
 202  */
 203 static int construct_key(struct key *key, const void *callout_info,
 204                          size_t callout_len, void *aux,
 205                          struct key *dest_keyring)
 206 {
 207         struct key_construction *cons;
 208         request_key_actor_t actor;
 209         struct key *authkey;
 210         int ret;
 211
 212         kenter("%d,%p,%zu,%p", key->serial, callout_info, callout_len, aux);
 213
 214         cons = kmalloc(sizeof(*cons), GFP_KERNEL);
 215         if (!cons)
 216                 return -ENOMEM;
 217
 218         /* allocate an authorisation key */
 219         authkey = request_key_auth_new(key, callout_info, callout_len,
 220                                        dest_keyring);
 221         if (IS_ERR(authkey)) {
 222                 kfree(cons);
 223                 ret = PTR_ERR(authkey);
 224                 authkey = NULL;
 225         } else {
 226                 cons->authkey = key_get(authkey);
 227                 cons->key = key_get(key);
 228
 229                 /* make the call */
 230                 actor = call_sbin_request_key;
 231                 if (key->type->request_key)
 232                         actor = key->type->request_key;
 233
 234                 ret = actor(cons, "create", aux);
 235
 236                 /* check that the actor called complete_request_key() prior to
 237                  * returning an error */
 238                 WARN_ON(ret < 0 &&
 239                         !test_bit(KEY_FLAG_REVOKED, &authkey->flags));
 240                 key_put(authkey);
 241         }
 242
 243         kleave(" = %d", ret);
 244         return ret;
 245 }
 246
 247 /*
 248  * get the appropriate destination keyring for the request
 249  * - we return whatever keyring we select with an extra reference upon it which
 250  *   the caller must release
 251  */
 252 static void construct_get_dest_keyring(struct key **_dest_keyring)
 253 {
 254         struct request_key_auth *rka;
 255         const struct cred *cred = current_cred();
 256         struct key *dest_keyring = *_dest_keyring, *authkey;
 257
 258         kenter("%p", dest_keyring);
 259
 260         /* find the appropriate keyring */
 261         if (dest_keyring) {
 262                 /* the caller supplied one */
 263                 key_get(dest_keyring);
 264         } else {
 265                 /* use a default keyring; falling through the cases until we
 266                  * find one that we actually have */
 267                 switch (cred->jit_keyring) {
 268                 case KEY_REQKEY_DEFL_DEFAULT:
 269                 case KEY_REQKEY_DEFL_REQUESTOR_KEYRING:
 270                         if (cred->request_key_auth) {
 271                                 authkey = cred->request_key_auth;
 272                                 down_read(&authkey->sem);
 273                                 rka = authkey->payload.data;
 274                                 if (!test_bit(KEY_FLAG_REVOKED,
 275                                               &authkey->flags))
 276                                         dest_keyring =
 277                                                 key_get(rka->dest_keyring);
 278                                 up_read(&authkey->sem);
 279                                 if (dest_keyring)
 280                                         break;
 281                         }
 282
 283                 case KEY_REQKEY_DEFL_THREAD_KEYRING:
 284                         dest_keyring = key_get(cred->thread_keyring);
 285                         if (dest_keyring)
 286                                 break;
 287
 288                 case KEY_REQKEY_DEFL_PROCESS_KEYRING:
 289                         dest_keyring = key_get(cred->tgcred->process_keyring);
 290                         if (dest_keyring)
 291                                 break;
 292
 293                 case KEY_REQKEY_DEFL_SESSION_KEYRING:
 294                         rcu_read_lock();
 295                         dest_keyring = key_get(
 296                                 rcu_dereference(cred->tgcred->session_keyring));
 297                         rcu_read_unlock();
 298
 299                         if (dest_keyring)
 300                                 break;
 301
 302                 case KEY_REQKEY_DEFL_USER_SESSION_KEYRING:
 303                         dest_keyring =
 304                                 key_get(cred->user->session_keyring);
 305                         break;
 306
 307                 case KEY_REQKEY_DEFL_USER_KEYRING:
 308                         dest_keyring = key_get(cred->user->uid_keyring);
 309                         break;
 310
 311                 case KEY_REQKEY_DEFL_GROUP_KEYRING:
 312                 default:
 313                         BUG();
 314                 }
 315         }
 316
 317         *_dest_keyring = dest_keyring;
 318         kleave(" [dk %d]", key_serial(dest_keyring));
 319         return;
 320 }
 321
 322 /*
 323  * allocate a new key in under-construction state and attempt to link it in to
 324  * the requested place
 325  * - may return a key that's already under construction instead
 326  */
 327 static int construct_alloc_key(struct key_type *type,
 328                                const char *description,
 329                                struct key *dest_keyring,
 330                                unsigned long flags,
 331                                struct key_user *user,
 332                                struct key **_key)
 333 {
 334         struct keyring_list *prealloc;
 335         const struct cred *cred = current_cred();
 336         struct key *key;
 337         key_ref_t key_ref;
 338         int ret;
 339
 340         kenter("%s,%s,,,", type->name, description);
 341
 342         *_key = NULL;
 343         mutex_lock(&user->cons_lock);
 344
 345         key = key_alloc(type, description, cred->fsuid, cred->fsgid, cred,
 346                         KEY_POS_ALL, flags);
 347         if (IS_ERR(key))
 348                 goto alloc_failed;
 349
 350         set_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags);
 351
 352         if (dest_keyring) {
 353                 ret = __key_link_begin(dest_keyring, type, description,
 354                                        &prealloc);
 355                 if (ret < 0)
 356                         goto link_prealloc_failed;
 357         }
 358
 359         /* attach the key to the destination keyring under lock, but we do need
 360          * to do another check just in case someone beat us to it whilst we
 361          * waited for locks */
 362         mutex_lock(&key_construction_mutex);
 363
 364         key_ref = search_process_keyrings(type, description, type->match, cred);
 365         if (!IS_ERR(key_ref))
 366                 goto key_already_present;
 367
 368         if (dest_keyring)
 369                 __key_link(dest_keyring, key, &prealloc);
 370
 371         mutex_unlock(&key_construction_mutex);
 372         if (dest_keyring)
 373                 __key_link_end(dest_keyring, type, prealloc);
 374         mutex_unlock(&user->cons_lock);
 375         *_key = key;
 376         kleave(" = 0 [%d]", key_serial(key));
 377         return 0;
 378
 379         /* the key is now present - we tell the caller that we found it by
 380          * returning -EINPROGRESS  */
 381 key_already_present:
 382         key_put(key);
 383         mutex_unlock(&key_construction_mutex);
 384         key = key_ref_to_ptr(key_ref);
 385         if (dest_keyring) {
 386                 ret = __key_link_check_live_key(dest_keyring, key);
 387                 if (ret == 0)
 388                         __key_link(dest_keyring, key, &prealloc);
 389                 __key_link_end(dest_keyring, type, prealloc);
 390                 if (ret < 0)
 391                         goto link_check_failed;
 392         }
 393         mutex_unlock(&user->cons_lock);
 394         *_key = key;
 395         kleave(" = -EINPROGRESS [%d]", key_serial(key));
 396         return -EINPROGRESS;
 397
 398 link_check_failed:
 399         mutex_unlock(&user->cons_lock);
 400         key_put(key);
 401         kleave(" = %d [linkcheck]", ret);
 402         return ret;
 403
 404 link_prealloc_failed:
 405         up_write(&dest_keyring->sem);
 406         mutex_unlock(&user->cons_lock);
 407         kleave(" = %d [prelink]", ret);
 408         return ret;
 409
 410 alloc_failed:
 411         mutex_unlock(&user->cons_lock);
 412         kleave(" = %ld", PTR_ERR(key));
 413         return PTR_ERR(key);
 414 }
 415
 416 /*
 417  * commence key construction
 418  */
 419 static struct key *construct_key_and_link(struct key_type *type,
 420                                           const char *description,
 421                                           const char *callout_info,
 422                                           size_t callout_len,
 423                                           void *aux,
 424                                           struct key *dest_keyring,
 425                                           unsigned long flags)
 426 {
 427         struct key_user *user;
 428         struct key *key;
 429         int ret;
 430
 431         kenter("");
 432
 433         user = key_user_lookup(current_fsuid(), current_user_ns());
 434         if (!user)
 435                 return ERR_PTR(-ENOMEM);
 436
 437         construct_get_dest_keyring(&dest_keyring);
 438
 439         ret = construct_alloc_key(type, description, dest_keyring, flags, user,
 440                                   &key);
 441         key_user_put(user);
 442
 443         if (ret == 0) {
 444                 ret = construct_key(key, callout_info, callout_len, aux,
 445                                     dest_keyring);
 446                 if (ret < 0) {
 447                         kdebug("cons failed");
 448                         goto construction_failed;
 449                 }
 450         } else if (ret == -EINPROGRESS) {
 451                 ret = 0;
 452         } else {
 453                 key = ERR_PTR(ret);
 454         }
 455
 456         key_put(dest_keyring);
 457         kleave(" = key %d", key_serial(key));
 458         return key;
 459
 460 construction_failed:
 461         key_negate_and_link(key, key_negative_timeout, NULL, NULL);
 462         key_put(key);
 463         key_put(dest_keyring);
 464         kleave(" = %d", ret);
 465         return ERR_PTR(ret);
 466 }
 467
 468 /*
 469  * request a key
 470  * - search the process's keyrings
 471  * - check the list of keys being created or updated
 472  * - call out to userspace for a key if supplementary info was provided
 473  * - cache the key in an appropriate keyring
 474  */
 475 struct key *request_key_and_link(struct key_type *type,
 476                                  const char *description,
 477                                  const void *callout_info,
 478                                  size_t callout_len,
 479                                  void *aux,
 480                                  struct key *dest_keyring,
 481                                  unsigned long flags)
 482 {
 483         const struct cred *cred = current_cred();
 484         struct key *key;
 485         key_ref_t key_ref;
 486         int ret;
 487
 488         kenter("%s,%s,%p,%zu,%p,%p,%lx",
 489                type->name, description, callout_info, callout_len, aux,
 490                dest_keyring, flags);
 491
 492         /* search all the process keyrings for a key */
 493         key_ref = search_process_keyrings(type, description, type->match,
 494                                           cred);
 495
 496         if (!IS_ERR(key_ref)) {
 497                 key = key_ref_to_ptr(key_ref);
 498                 if (dest_keyring) {
 499                         construct_get_dest_keyring(&dest_keyring);
 500                         ret = key_link(dest_keyring, key);
 501                         key_put(dest_keyring);
 502                         if (ret < 0) {
 503                                 key_put(key);
 504                                 key = ERR_PTR(ret);
 505                                 goto error;
 506                         }
 507                 }
 508         } else if (PTR_ERR(key_ref) != -EAGAIN) {
 509                 key = ERR_CAST(key_ref);
 510         } else  {
 511                 /* the search failed, but the keyrings were searchable, so we
 512                  * should consult userspace if we can */
 513                 key = ERR_PTR(-ENOKEY);
 514                 if (!callout_info)
 515                         goto error;
 516
 517                 key = construct_key_and_link(type, description, callout_info,
 518                                              callout_len, aux, dest_keyring,
 519                                              flags);
 520         }
 521
 522 error:
 523         kleave(" = %p", key);
 524         return key;
 525 }
 526
 527 /*
 528  * wait for construction of a key to complete
 529  */
 530 int wait_for_key_construction(struct key *key, bool intr)
 531 {
 532         int ret;
 533
 534         ret = wait_on_bit(&key->flags, KEY_FLAG_USER_CONSTRUCT,
 535                           intr ? key_wait_bit_intr : key_wait_bit,
 536                           intr ? TASK_INTERRUPTIBLE : TASK_UNINTERRUPTIBLE);
 537         if (ret < 0)
 538                 return ret;
 539         return key_validate(key);
 540 }
 541 EXPORT_SYMBOL(wait_for_key_construction);
 542
 543 /*
 544  * request a key
 545  * - search the process's keyrings
 546  * - check the list of keys being created or updated
 547  * - call out to userspace for a key if supplementary info was provided
 548  * - waits uninterruptible for creation to complete
 549  */
 550 struct key *request_key(struct key_type *type,
 551                         const char *description,
 552                         const char *callout_info)
 553 {
 554         struct key *key;
 555         size_t callout_len = 0;
 556         int ret;
 557
 558         if (callout_info)
 559                 callout_len = strlen(callout_info);
 560         key = request_key_and_link(type, description, callout_info, callout_len,
 561                                    NULL, NULL, KEY_ALLOC_IN_QUOTA);
 562         if (!IS_ERR(key)) {
 563                 ret = wait_for_key_construction(key, false);
 564                 if (ret < 0) {
 565                         key_put(key);
 566                         return ERR_PTR(ret);
 567                 }
 568         }
 569         return key;
 570 }
 571 EXPORT_SYMBOL(request_key);
 572
 573 /*
 574  * request a key with auxiliary data for the upcaller
 575  * - search the process's keyrings
 576  * - check the list of keys being created or updated
 577  * - call out to userspace for a key if supplementary info was provided
 578  * - waits uninterruptible for creation to complete
 579  */
 580 struct key *request_key_with_auxdata(struct key_type *type,
 581                                      const char *description,
 582                                      const void *callout_info,
 583                                      size_t callout_len,
 584                                      void *aux)
 585 {
 586         struct key *key;
 587         int ret;
 588
 589         key = request_key_and_link(type, description, callout_info, callout_len,
 590                                    aux, NULL, KEY_ALLOC_IN_QUOTA);
 591         if (!IS_ERR(key)) {
 592                 ret = wait_for_key_construction(key, false);
 593                 if (ret < 0) {
 594                         key_put(key);
 595                         return ERR_PTR(ret);
 596                 }
 597         }
 598         return key;
 599 }
 600 EXPORT_SYMBOL(request_key_with_auxdata);
 601
 602 /*
 603  * request a key (allow async construction)
 604  * - search the process's keyrings
 605  * - check the list of keys being created or updated
 606  * - call out to userspace for a key if supplementary info was provided
 607  */
 608 struct key *request_key_async(struct key_type *type,
 609                               const char *description,
 610                               const void *callout_info,
 611                               size_t callout_len)
 612 {
 613         return request_key_and_link(type, description, callout_info,
 614                                     callout_len, NULL, NULL,
 615                                     KEY_ALLOC_IN_QUOTA);
 616 }
 617 EXPORT_SYMBOL(request_key_async);
 618
 619 /*
 620  * request a key with auxiliary data for the upcaller (allow async construction)
 621  * - search the process's keyrings
 622  * - check the list of keys being created or updated
 623  * - call out to userspace for a key if supplementary info was provided
 624  */
 625 struct key *request_key_async_with_auxdata(struct key_type *type,
 626                                            const char *description,
 627                                            const void *callout_info,
 628                                            size_t callout_len,
 629                                            void *aux)
 630 {
 631         return request_key_and_link(type, description, callout_info,
 632                                     callout_len, aux, NULL, KEY_ALLOC_IN_QUOTA);
 633 }
 634 EXPORT_SYMBOL(request_key_async_with_auxdata);