security/keys/request_key.c

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