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         sprintf(keyring_str[1], "%d", prkey);
 148
 149         rcu_read_lock();
 150         session = rcu_dereference(cred->tgcred->session_keyring);
 151         if (!session)
 152                 session = cred->user->session_keyring;
 153         sskey = session->serial;
 154         rcu_read_unlock();
 155
 156         sprintf(keyring_str[2], "%d", sskey);
 157
 158         /* set up a minimal environment */
 159         i = 0;
 160         envp[i++] = "HOME=/";
 161         envp[i++] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
 162         envp[i] = NULL;
 163
 164         /* set up the argument list */
 165         i = 0;
 166         argv[i++] = "/sbin/request-key";
 167         argv[i++] = (char *) op;
 168         argv[i++] = key_str;
 169         argv[i++] = uid_str;
 170         argv[i++] = gid_str;
 171         argv[i++] = keyring_str[0];
 172         argv[i++] = keyring_str[1];
 173         argv[i++] = keyring_str[2];
 174         argv[i] = NULL;
 175
 176         /* do it */
 177         ret = call_usermodehelper_keys(argv[0], argv, envp, keyring,
 178                                        UMH_WAIT_PROC);
 179         kdebug("usermode -> 0x%x", ret);
 180         if (ret >= 0) {
 181                 /* ret is the exit/wait code */
 182                 if (test_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags) ||
 183                     key_validate(key) < 0)
 184                         ret = -ENOKEY;
 185                 else
 186                         /* ignore any errors from userspace if the key was
 187                          * instantiated */
 188                         ret = 0;
 189         }
 190
 191 error_link:
 192         key_put(keyring);
 193
 194 error_alloc:
 195         complete_request_key(cons, ret);
 196         kleave(" = %d", ret);
 197         return ret;
 198 }
 199
 200 /*
 201  * call out to userspace for key construction
 202  * - we ignore program failure and go on key status instead
 203  */
 204 static int construct_key(struct key *key, const void *callout_info,
 205                          size_t callout_len, void *aux,
 206                          struct key *dest_keyring)
 207 {
 208         struct key_construction *cons;
 209         request_key_actor_t actor;
 210         struct key *authkey;
 211         int ret;
 212
 213         kenter("%d,%p,%zu,%p", key->serial, callout_info, callout_len, aux);
 214
 215         cons = kmalloc(sizeof(*cons), GFP_KERNEL);
 216         if (!cons)
 217                 return -ENOMEM;
 218
 219         /* allocate an authorisation key */
 220         authkey = request_key_auth_new(key, callout_info, callout_len,
 221                                        dest_keyring);
 222         if (IS_ERR(authkey)) {
 223                 kfree(cons);
 224                 ret = PTR_ERR(authkey);
 225                 authkey = NULL;
 226         } else {
 227                 cons->authkey = key_get(authkey);
 228                 cons->key = key_get(key);
 229
 230                 /* make the call */
 231                 actor = call_sbin_request_key;
 232                 if (key->type->request_key)
 233                         actor = key->type->request_key;
 234
 235                 ret = actor(cons, "create", aux);
 236
 237                 /* check that the actor called complete_request_key() prior to
 238                  * returning an error */
 239                 WARN_ON(ret < 0 &&
 240                         !test_bit(KEY_FLAG_REVOKED, &authkey->flags));
 241                 key_put(authkey);
 242         }
 243
 244         kleave(" = %d", ret);
 245         return ret;
 246 }
 247
 248 /*
 249  * get the appropriate destination keyring for the request
 250  * - we return whatever keyring we select with an extra reference upon it which
 251  *   the caller must release
 252  */
 253 static void construct_get_dest_keyring(struct key **_dest_keyring)
 254 {
 255         struct request_key_auth *rka;
 256         const struct cred *cred = current_cred();
 257         struct key *dest_keyring = *_dest_keyring, *authkey;
 258
 259         kenter("%p", dest_keyring);
 260
 261         /* find the appropriate keyring */
 262         if (dest_keyring) {
 263                 /* the caller supplied one */
 264                 key_get(dest_keyring);
 265         } else {
 266                 /* use a default keyring; falling through the cases until we
 267                  * find one that we actually have */
 268                 switch (cred->jit_keyring) {
 269                 case KEY_REQKEY_DEFL_DEFAULT:
 270                 case KEY_REQKEY_DEFL_REQUESTOR_KEYRING:
 271                         if (cred->request_key_auth) {
 272                                 authkey = cred->request_key_auth;
 273                                 down_read(&authkey->sem);
 274                                 rka = authkey->payload.data;
 275                                 if (!test_bit(KEY_FLAG_REVOKED,
 276                                               &authkey->flags))
 277                                         dest_keyring =
 278                                                 key_get(rka->dest_keyring);
 279                                 up_read(&authkey->sem);
 280                                 if (dest_keyring)
 281                                         break;
 282                         }
 283
 284                 case KEY_REQKEY_DEFL_THREAD_KEYRING:
 285                         dest_keyring = key_get(cred->thread_keyring);
 286                         if (dest_keyring)
 287                                 break;
 288
 289                 case KEY_REQKEY_DEFL_PROCESS_KEYRING:
 290                         dest_keyring = key_get(cred->tgcred->process_keyring);
 291                         if (dest_keyring)
 292                                 break;
 293
 294                 case KEY_REQKEY_DEFL_SESSION_KEYRING:
 295                         rcu_read_lock();
 296                         dest_keyring = key_get(
 297                                 rcu_dereference(cred->tgcred->session_keyring));
 298                         rcu_read_unlock();
 299
 300                         if (dest_keyring)
 301                                 break;
 302
 303                 case KEY_REQKEY_DEFL_USER_SESSION_KEYRING:
 304                         dest_keyring =
 305                                 key_get(cred->user->session_keyring);
 306                         break;
 307
 308                 case KEY_REQKEY_DEFL_USER_KEYRING:
 309                         dest_keyring = key_get(cred->user->uid_keyring);
 310                         break;
 311
 312                 case KEY_REQKEY_DEFL_GROUP_KEYRING:
 313                 default:
 314                         BUG();
 315                 }
 316         }
 317
 318         *_dest_keyring = dest_keyring;
 319         kleave(" [dk %d]", key_serial(dest_keyring));
 320         return;
 321 }
 322
 323 /*
 324  * allocate a new key in under-construction state and attempt to link it in to
 325  * the requested place
 326  * - may return a key that's already under construction instead
 327  */
 328 static int construct_alloc_key(struct key_type *type,
 329                                const char *description,
 330                                struct key *dest_keyring,
 331                                unsigned long flags,
 332                                struct key_user *user,
 333                                struct key **_key)
 334 {
 335         struct keyring_list *prealloc;
 336         const struct cred *cred = current_cred();
 337         struct key *key;
 338         key_ref_t key_ref;
 339         int ret;
 340
 341         kenter("%s,%s,,,", type->name, description);
 342
 343         *_key = NULL;
 344         mutex_lock(&user->cons_lock);
 345
 346         key = key_alloc(type, description, cred->fsuid, cred->fsgid, cred,
 347                         KEY_POS_ALL, flags);
 348         if (IS_ERR(key))
 349                 goto alloc_failed;
 350
 351         set_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags);
 352
 353         if (dest_keyring) {
 354                 ret = __key_link_begin(dest_keyring, type, description,
 355                                        &prealloc);
 356                 if (ret < 0)
 357                         goto link_prealloc_failed;
 358         }
 359
 360         /* attach the key to the destination keyring under lock, but we do need
 361          * to do another check just in case someone beat us to it whilst we
 362          * waited for locks */
 363         mutex_lock(&key_construction_mutex);
 364
 365         key_ref = search_process_keyrings(type, description, type->match, cred);
 366         if (!IS_ERR(key_ref))
 367                 goto key_already_present;
 368
 369         if (dest_keyring)
 370                 __key_link(dest_keyring, key, &prealloc);
 371
 372         mutex_unlock(&key_construction_mutex);
 373         if (dest_keyring)
 374                 __key_link_end(dest_keyring, type, prealloc);
 375         mutex_unlock(&user->cons_lock);
 376         *_key = key;
 377         kleave(" = 0 [%d]", key_serial(key));
 378         return 0;
 379
 380         /* the key is now present - we tell the caller that we found it by
 381          * returning -EINPROGRESS  */
 382 key_already_present:
 383         key_put(key);
 384         mutex_unlock(&key_construction_mutex);
 385         key = key_ref_to_ptr(key_ref);
 386         if (dest_keyring) {
 387                 ret = __key_link_check_live_key(dest_keyring, key);
 388                 if (ret == 0)
 389                         __key_link(dest_keyring, key, &prealloc);
 390                 __key_link_end(dest_keyring, type, prealloc);
 391                 if (ret < 0)
 392                         goto link_check_failed;
 393         }
 394         mutex_unlock(&user->cons_lock);
 395         *_key = key;
 396         kleave(" = -EINPROGRESS [%d]", key_serial(key));
 397         return -EINPROGRESS;
 398
 399 link_check_failed:
 400         mutex_unlock(&user->cons_lock);
 401         key_put(key);
 402         kleave(" = %d [linkcheck]", ret);
 403         return ret;
 404
 405 link_prealloc_failed:
 406         up_write(&dest_keyring->sem);
 407         mutex_unlock(&user->cons_lock);
 408         kleave(" = %d [prelink]", ret);
 409         return ret;
 410
 411 alloc_failed:
 412         mutex_unlock(&user->cons_lock);
 413         kleave(" = %ld", PTR_ERR(key));
 414         return PTR_ERR(key);
 415 }
 416
 417 /*
 418  * commence key construction
 419  */
 420 static struct key *construct_key_and_link(struct key_type *type,
 421                                           const char *description,
 422                                           const char *callout_info,
 423                                           size_t callout_len,
 424                                           void *aux,
 425                                           struct key *dest_keyring,
 426                                           unsigned long flags)
 427 {
 428         struct key_user *user;
 429         struct key *key;
 430         int ret;
 431
 432         kenter("");
 433
 434         user = key_user_lookup(current_fsuid(), current_user_ns());
 435         if (!user)
 436                 return ERR_PTR(-ENOMEM);
 437
 438         construct_get_dest_keyring(&dest_keyring);
 439
 440         ret = construct_alloc_key(type, description, dest_keyring, flags, user,
 441                                   &key);
 442         key_user_put(user);
 443
 444         if (ret == 0) {
 445                 ret = construct_key(key, callout_info, callout_len, aux,
 446                                     dest_keyring);
 447                 if (ret < 0) {
 448                         kdebug("cons failed");
 449                         goto construction_failed;
 450                 }
 451         } else if (ret == -EINPROGRESS) {
 452                 ret = 0;
 453         } else {
 454                 key = ERR_PTR(ret);
 455         }
 456
 457         key_put(dest_keyring);
 458         kleave(" = key %d", key_serial(key));
 459         return key;
 460
 461 construction_failed:
 462         key_negate_and_link(key, key_negative_timeout, NULL, NULL);
 463         key_put(key);
 464         key_put(dest_keyring);
 465         kleave(" = %d", ret);
 466         return ERR_PTR(ret);
 467 }
 468
 469 /*
 470  * request a key
 471  * - search the process's keyrings
 472  * - check the list of keys being created or updated
 473  * - call out to userspace for a key if supplementary info was provided
 474  * - cache the key in an appropriate keyring
 475  */
 476 struct key *request_key_and_link(struct key_type *type,
 477                                  const char *description,
 478                                  const void *callout_info,
 479                                  size_t callout_len,
 480                                  void *aux,
 481                                  struct key *dest_keyring,
 482                                  unsigned long flags)
 483 {
 484         const struct cred *cred = current_cred();
 485         struct key *key;
 486         key_ref_t key_ref;
 487         int ret;
 488
 489         kenter("%s,%s,%p,%zu,%p,%p,%lx",
 490                type->name, description, callout_info, callout_len, aux,
 491                dest_keyring, flags);
 492
 493         /* search all the process keyrings for a key */
 494         key_ref = search_process_keyrings(type, description, type->match,
 495                                           cred);
 496
 497         if (!IS_ERR(key_ref)) {
 498                 key = key_ref_to_ptr(key_ref);
 499                 if (dest_keyring) {
 500                         construct_get_dest_keyring(&dest_keyring);
 501                         ret = key_link(dest_keyring, key);
 502                         key_put(dest_keyring);
 503                         if (ret < 0) {
 504                                 key_put(key);
 505                                 key = ERR_PTR(ret);
 506                                 goto error;
 507                         }
 508                 }
 509         } else if (PTR_ERR(key_ref) != -EAGAIN) {
 510                 key = ERR_CAST(key_ref);
 511         } else  {
 512                 /* the search failed, but the keyrings were searchable, so we
 513                  * should consult userspace if we can */
 514                 key = ERR_PTR(-ENOKEY);
 515                 if (!callout_info)
 516                         goto error;
 517
 518                 key = construct_key_and_link(type, description, callout_info,
 519                                              callout_len, aux, dest_keyring,
 520                                              flags);
 521         }
 522
 523 error:
 524         kleave(" = %p", key);
 525         return key;
 526 }
 527
 528 /*
 529  * wait for construction of a key to complete
 530  */
 531 int wait_for_key_construction(struct key *key, bool intr)
 532 {
 533         int ret;
 534
 535         ret = wait_on_bit(&key->flags, KEY_FLAG_USER_CONSTRUCT,
 536                           intr ? key_wait_bit_intr : key_wait_bit,
 537                           intr ? TASK_INTERRUPTIBLE : TASK_UNINTERRUPTIBLE);
 538         if (ret < 0)
 539                 return ret;
 540         if (test_bit(KEY_FLAG_NEGATIVE, &key->flags))
 541                 return -ENOKEY;
 542         return key_validate(key);
 543 }
 544 EXPORT_SYMBOL(wait_for_key_construction);
 545
 546 /*
 547  * request a key
 548  * - search the process's keyrings
 549  * - check the list of keys being created or updated
 550  * - call out to userspace for a key if supplementary info was provided
 551  * - waits uninterruptible for creation to complete
 552  */
 553 struct key *request_key(struct key_type *type,
 554                         const char *description,
 555                         const char *callout_info)
 556 {
 557         struct key *key;
 558         size_t callout_len = 0;
 559         int ret;
 560
 561         if (callout_info)
 562                 callout_len = strlen(callout_info);
 563         key = request_key_and_link(type, description, callout_info, callout_len,
 564                                    NULL, NULL, KEY_ALLOC_IN_QUOTA);
 565         if (!IS_ERR(key)) {
 566                 ret = wait_for_key_construction(key, false);
 567                 if (ret < 0) {
 568                         key_put(key);
 569                         return ERR_PTR(ret);
 570                 }
 571         }
 572         return key;
 573 }
 574 EXPORT_SYMBOL(request_key);
 575
 576 /*
 577  * request a key with auxiliary data for the upcaller
 578  * - search the process's keyrings
 579  * - check the list of keys being created or updated
 580  * - call out to userspace for a key if supplementary info was provided
 581  * - waits uninterruptible for creation to complete
 582  */
 583 struct key *request_key_with_auxdata(struct key_type *type,
 584                                      const char *description,
 585                                      const void *callout_info,
 586                                      size_t callout_len,
 587                                      void *aux)
 588 {
 589         struct key *key;
 590         int ret;
 591
 592         key = request_key_and_link(type, description, callout_info, callout_len,
 593                                    aux, NULL, KEY_ALLOC_IN_QUOTA);
 594         if (!IS_ERR(key)) {
 595                 ret = wait_for_key_construction(key, false);
 596                 if (ret < 0) {
 597                         key_put(key);
 598                         return ERR_PTR(ret);
 599                 }
 600         }
 601         return key;
 602 }
 603 EXPORT_SYMBOL(request_key_with_auxdata);
 604
 605 /*
 606  * request a key (allow async construction)
 607  * - search the process's keyrings
 608  * - check the list of keys being created or updated
 609  * - call out to userspace for a key if supplementary info was provided
 610  */
 611 struct key *request_key_async(struct key_type *type,
 612                               const char *description,
 613                               const void *callout_info,
 614                               size_t callout_len)
 615 {
 616         return request_key_and_link(type, description, callout_info,
 617                                     callout_len, NULL, NULL,
 618                                     KEY_ALLOC_IN_QUOTA);
 619 }
 620 EXPORT_SYMBOL(request_key_async);
 621
 622 /*
 623  * request a key with auxiliary data for the upcaller (allow async construction)
 624  * - search the process's keyrings
 625  * - check the list of keys being created or updated
 626  * - call out to userspace for a key if supplementary info was provided
 627  */
 628 struct key *request_key_async_with_auxdata(struct key_type *type,
 629                                            const char *description,
 630                                            const void *callout_info,
 631                                            size_t callout_len,
 632                                            void *aux)
 633 {
 634         return request_key_and_link(type, description, callout_info,
 635                                     callout_len, aux, NULL, KEY_ALLOC_IN_QUOTA);
 636 }
 637 EXPORT_SYMBOL(request_key_async_with_auxdata);