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         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         keyring = keyring_alloc(desc, current_fsuid(), current_fsgid(), current,
  87                                 KEY_ALLOC_QUOTA_OVERRUN, NULL);
  88         if (IS_ERR(keyring)) {
  89                 ret = PTR_ERR(keyring);
  90                 goto error_alloc;
  91         }
  92
  93         /* attach the auth key to the session keyring */
  94         ret = __key_link(keyring, authkey);
  95         if (ret < 0)
  96                 goto error_link;
  97
  98         /* record the UID and GID */
  99         sprintf(uid_str, "%d", current_fsuid());
 100         sprintf(gid_str, "%d", current_fsgid());
 101
 102         /* we say which key is under construction */
 103         sprintf(key_str, "%d", key->serial);
 104
 105         /* we specify the process's default keyrings */
 106         sprintf(keyring_str[0], "%d",
 107                 tsk->thread_keyring ? tsk->thread_keyring->serial : 0);
 108
 109         prkey = 0;
 110         if (tsk->signal->process_keyring)
 111                 prkey = tsk->signal->process_keyring->serial;
 112
 113         sprintf(keyring_str[1], "%d", prkey);
 114
 115         if (tsk->signal->session_keyring) {
 116                 rcu_read_lock();
 117                 sskey = rcu_dereference(tsk->signal->session_keyring)->serial;
 118                 rcu_read_unlock();
 119         } else {
 120                 sskey = tsk->user->session_keyring->serial;
 121         }
 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         kleave(" = %d", ret);
 163         complete_request_key(cons, 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         struct task_struct *tsk = current;
 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 (tsk->jit_keyring) {
 236                 case KEY_REQKEY_DEFL_DEFAULT:
 237                 case KEY_REQKEY_DEFL_REQUESTOR_KEYRING:
 238                         if (tsk->request_key_auth) {
 239                                 authkey = tsk->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(tsk->thread_keyring);
 253                         if (dest_keyring)
 254                                 break;
 255
 256                 case KEY_REQKEY_DEFL_PROCESS_KEYRING:
 257                         dest_keyring = key_get(tsk->signal->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(tsk->signal->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 = key_get(tsk->user->session_keyring);
 272                         break;
 273
 274                 case KEY_REQKEY_DEFL_USER_KEYRING:
 275                         dest_keyring = key_get(tsk->user->uid_keyring);
 276                         break;
 277
 278                 case KEY_REQKEY_DEFL_GROUP_KEYRING:
 279                 default:
 280                         BUG();
 281                 }
 282         }
 283
 284         *_dest_keyring = dest_keyring;
 285         kleave(" [dk %d]", key_serial(dest_keyring));
 286         return;
 287 }
 288
 289 /*
 290  * allocate a new key in under-construction state and attempt to link it in to
 291  * the requested place
 292  * - may return a key that's already under construction instead
 293  */
 294 static int construct_alloc_key(struct key_type *type,
 295                                const char *description,
 296                                struct key *dest_keyring,
 297                                unsigned long flags,
 298                                struct key_user *user,
 299                                struct key **_key)
 300 {
 301         struct key *key;
 302         key_ref_t key_ref;
 303
 304         kenter("%s,%s,,,", type->name, description);
 305
 306         mutex_lock(&user->cons_lock);
 307
 308         key = key_alloc(type, description,
 309                         current_fsuid(), current_fsgid(), current, KEY_POS_ALL,
 310                         flags);
 311         if (IS_ERR(key))
 312                 goto alloc_failed;
 313
 314         set_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags);
 315
 316         down_write(&dest_keyring->sem);
 317
 318         /* attach the key to the destination keyring under lock, but we do need
 319          * to do another check just in case someone beat us to it whilst we
 320          * waited for locks */
 321         mutex_lock(&key_construction_mutex);
 322
 323         key_ref = search_process_keyrings(type, description, type->match,
 324                                           current);
 325         if (!IS_ERR(key_ref))
 326                 goto key_already_present;
 327
 328         __key_link(dest_keyring, key);
 329
 330         mutex_unlock(&key_construction_mutex);
 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         user = key_user_lookup(current_fsuid());
 370         if (!user)
 371                 return ERR_PTR(-ENOMEM);
 372
 373         construct_get_dest_keyring(&dest_keyring);
 374
 375         ret = construct_alloc_key(type, description, dest_keyring, flags, user,
 376                                   &key);
 377         key_user_put(user);
 378
 379         if (ret == 0) {
 380                 ret = construct_key(key, callout_info, callout_len, aux,
 381                                     dest_keyring);
 382                 if (ret < 0)
 383                         goto construction_failed;
 384         }
 385
 386         key_put(dest_keyring);
 387         return key;
 388
 389 construction_failed:
 390         key_negate_and_link(key, key_negative_timeout, NULL, NULL);
 391         key_put(key);
 392         key_put(dest_keyring);
 393         return ERR_PTR(ret);
 394 }
 395
 396 /*
 397  * request a key
 398  * - search the process's keyrings
 399  * - check the list of keys being created or updated
 400  * - call out to userspace for a key if supplementary info was provided
 401  * - cache the key in an appropriate keyring
 402  */
 403 struct key *request_key_and_link(struct key_type *type,
 404                                  const char *description,
 405                                  const void *callout_info,
 406                                  size_t callout_len,
 407                                  void *aux,
 408                                  struct key *dest_keyring,
 409                                  unsigned long flags)
 410 {
 411         struct key *key;
 412         key_ref_t key_ref;
 413
 414         kenter("%s,%s,%p,%zu,%p,%p,%lx",
 415                type->name, description, callout_info, callout_len, aux,
 416                dest_keyring, flags);
 417
 418         /* search all the process keyrings for a key */
 419         key_ref = search_process_keyrings(type, description, type->match,
 420                                           current);
 421
 422         if (!IS_ERR(key_ref)) {
 423                 key = key_ref_to_ptr(key_ref);
 424         } else if (PTR_ERR(key_ref) != -EAGAIN) {
 425                 key = ERR_CAST(key_ref);
 426         } else  {
 427                 /* the search failed, but the keyrings were searchable, so we
 428                  * should consult userspace if we can */
 429                 key = ERR_PTR(-ENOKEY);
 430                 if (!callout_info)
 431                         goto error;
 432
 433                 key = construct_key_and_link(type, description, callout_info,
 434                                              callout_len, aux, dest_keyring,
 435                                              flags);
 436         }
 437
 438 error:
 439         kleave(" = %p", key);
 440         return key;
 441 }
 442
 443 /*
 444  * wait for construction of a key to complete
 445  */
 446 int wait_for_key_construction(struct key *key, bool intr)
 447 {
 448         int ret;
 449
 450         ret = wait_on_bit(&key->flags, KEY_FLAG_USER_CONSTRUCT,
 451                           intr ? key_wait_bit_intr : key_wait_bit,
 452                           intr ? TASK_INTERRUPTIBLE : TASK_UNINTERRUPTIBLE);
 453         if (ret < 0)
 454                 return ret;
 455         return key_validate(key);
 456 }
 457 EXPORT_SYMBOL(wait_for_key_construction);
 458
 459 /*
 460  * request a key
 461  * - search the process's keyrings
 462  * - check the list of keys being created or updated
 463  * - call out to userspace for a key if supplementary info was provided
 464  * - waits uninterruptible for creation to complete
 465  */
 466 struct key *request_key(struct key_type *type,
 467                         const char *description,
 468                         const char *callout_info)
 469 {
 470         struct key *key;
 471         size_t callout_len = 0;
 472         int ret;
 473
 474         if (callout_info)
 475                 callout_len = strlen(callout_info);
 476         key = request_key_and_link(type, description, callout_info, callout_len,
 477                                    NULL, NULL, KEY_ALLOC_IN_QUOTA);
 478         if (!IS_ERR(key)) {
 479                 ret = wait_for_key_construction(key, false);
 480                 if (ret < 0) {
 481                         key_put(key);
 482                         return ERR_PTR(ret);
 483                 }
 484         }
 485         return key;
 486 }
 487 EXPORT_SYMBOL(request_key);
 488
 489 /*
 490  * request a key with auxiliary data for the upcaller
 491  * - search the process's keyrings
 492  * - check the list of keys being created or updated
 493  * - call out to userspace for a key if supplementary info was provided
 494  * - waits uninterruptible for creation to complete
 495  */
 496 struct key *request_key_with_auxdata(struct key_type *type,
 497                                      const char *description,
 498                                      const void *callout_info,
 499                                      size_t callout_len,
 500                                      void *aux)
 501 {
 502         struct key *key;
 503         int ret;
 504
 505         key = request_key_and_link(type, description, callout_info, callout_len,
 506                                    aux, NULL, KEY_ALLOC_IN_QUOTA);
 507         if (!IS_ERR(key)) {
 508                 ret = wait_for_key_construction(key, false);
 509                 if (ret < 0) {
 510                         key_put(key);
 511                         return ERR_PTR(ret);
 512                 }
 513         }
 514         return key;
 515 }
 516 EXPORT_SYMBOL(request_key_with_auxdata);
 517
 518 /*
 519  * request a key (allow async construction)
 520  * - search the process's keyrings
 521  * - check the list of keys being created or updated
 522  * - call out to userspace for a key if supplementary info was provided
 523  */
 524 struct key *request_key_async(struct key_type *type,
 525                               const char *description,
 526                               const void *callout_info,
 527                               size_t callout_len)
 528 {
 529         return request_key_and_link(type, description, callout_info,
 530                                     callout_len, NULL, NULL,
 531                                     KEY_ALLOC_IN_QUOTA);
 532 }
 533 EXPORT_SYMBOL(request_key_async);
 534
 535 /*
 536  * request a key with auxiliary data for the upcaller (allow async construction)
 537  * - search the process's keyrings
 538  * - check the list of keys being created or updated
 539  * - call out to userspace for a key if supplementary info was provided
 540  */
 541 struct key *request_key_async_with_auxdata(struct key_type *type,
 542                                            const char *description,
 543                                            const void *callout_info,
 544                                            size_t callout_len,
 545                                            void *aux)
 546 {
 547         return request_key_and_link(type, description, callout_info,
 548                                     callout_len, aux, NULL, KEY_ALLOC_IN_QUOTA);
 549 }
 550 EXPORT_SYMBOL(request_key_async_with_auxdata);