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