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