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 /*
  23  * wait_on_bit() sleep function for uninterruptible waiting
  24  */
  25 static int key_wait_bit(void *flags)
  26 {
  27         schedule();
  28         return 0;
  29 }
  30
  31 /*
  32  * wait_on_bit() sleep function for interruptible waiting
  33  */
  34 static int key_wait_bit_intr(void *flags)
  35 {
  36         schedule();
  37         return signal_pending(current) ? -ERESTARTSYS : 0;
  38 }
  39
  40 /*
  41  * call to complete the construction of a key
  42  */
  43 void complete_request_key(struct key_construction *cons, int error)
  44 {
  45         kenter("{%d,%d},%d", cons->key->serial, cons->authkey->serial, error);
  46
  47         if (error < 0)
  48                 key_negate_and_link(cons->key, key_negative_timeout, NULL,
  49                                     cons->authkey);
  50         else
  51                 key_revoke(cons->authkey);
  52
  53         key_put(cons->key);
  54         key_put(cons->authkey);
  55         kfree(cons);
  56 }
  57 EXPORT_SYMBOL(complete_request_key);
  58
  59 /*
  60  * request userspace finish the construction of a key
  61  * - execute "/sbin/request-key <op> <key> <uid> <gid> <keyring> <keyring> <keyring>"
  62  */
  63 static int call_sbin_request_key(struct key_construction *cons,
  64                                  const char *op,
  65                                  void *aux)
  66 {
  67         struct task_struct *tsk = current;
  68         key_serial_t prkey, sskey;
  69         struct key *key = cons->key, *authkey = cons->authkey, *keyring;
  70         char *argv[9], *envp[3], uid_str[12], gid_str[12];
  71         char key_str[12], keyring_str[3][12];
  72         char desc[20];
  73         int ret, i;
  74
  75         kenter("{%d},{%d},%s", key->serial, authkey->serial, op);
  76
  77         ret = install_user_keyrings(tsk);
  78         if (ret < 0)
  79                 goto error_alloc;
  80
  81         /* allocate a new session keyring */
  82         sprintf(desc, "_req.%u", key->serial);
  83
  84         keyring = keyring_alloc(desc, current->fsuid, current->fsgid, current,
  85                                 KEY_ALLOC_QUOTA_OVERRUN, NULL);
  86         if (IS_ERR(keyring)) {
  87                 ret = PTR_ERR(keyring);
  88                 goto error_alloc;
  89         }
  90
  91         /* attach the auth key to the session keyring */
  92         ret = __key_link(keyring, authkey);
  93         if (ret < 0)
  94                 goto error_link;
  95
  96         /* record the UID and GID */
  97         sprintf(uid_str, "%d", current->fsuid);
  98         sprintf(gid_str, "%d", current->fsgid);
  99
 100         /* we say which key is under construction */
 101         sprintf(key_str, "%d", key->serial);
 102
 103         /* we specify the process's default keyrings */
 104         sprintf(keyring_str[0], "%d",
 105                 tsk->thread_keyring ? tsk->thread_keyring->serial : 0);
 106
 107         prkey = 0;
 108         if (tsk->signal->process_keyring)
 109                 prkey = tsk->signal->process_keyring->serial;
 110
 111         sprintf(keyring_str[1], "%d", prkey);
 112
 113         if (tsk->signal->session_keyring) {
 114                 rcu_read_lock();
 115                 sskey = rcu_dereference(tsk->signal->session_keyring)->serial;
 116                 rcu_read_unlock();
 117         } else {
 118                 sskey = tsk->user->session_keyring->serial;
 119         }
 120
 121         sprintf(keyring_str[2], "%d", sskey);
 122
 123         /* set up a minimal environment */
 124         i = 0;
 125         envp[i++] = "HOME=/";
 126         envp[i++] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
 127         envp[i] = NULL;
 128
 129         /* set up the argument list */
 130         i = 0;
 131         argv[i++] = "/sbin/request-key";
 132         argv[i++] = (char *) op;
 133         argv[i++] = key_str;
 134         argv[i++] = uid_str;
 135         argv[i++] = gid_str;
 136         argv[i++] = keyring_str[0];
 137         argv[i++] = keyring_str[1];
 138         argv[i++] = keyring_str[2];
 139         argv[i] = NULL;
 140
 141         /* do it */
 142         ret = call_usermodehelper_keys(argv[0], argv, envp, keyring,
 143                                        UMH_WAIT_PROC);
 144         kdebug("usermode -> 0x%x", ret);
 145         if (ret >= 0) {
 146                 /* ret is the exit/wait code */
 147                 if (test_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags) ||
 148                     key_validate(key) < 0)
 149                         ret = -ENOKEY;
 150                 else
 151                         /* ignore any errors from userspace if the key was
 152                          * instantiated */
 153                         ret = 0;
 154         }
 155
 156 error_link:
 157         key_put(keyring);
 158
 159 error_alloc:
 160         kleave(" = %d", ret);
 161         complete_request_key(cons, ret);
 162         return ret;
 163 }
 164
 165 /*
 166  * call out to userspace for key construction
 167  * - we ignore program failure and go on key status instead
 168  */
 169 static int construct_key(struct key *key, const void *callout_info,
 170                          size_t callout_len, void *aux)
 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         if (IS_ERR(authkey)) {
 186                 kfree(cons);
 187                 ret = PTR_ERR(authkey);
 188                 authkey = NULL;
 189         } else {
 190                 cons->authkey = key_get(authkey);
 191                 cons->key = key_get(key);
 192
 193                 /* make the call */
 194                 actor = call_sbin_request_key;
 195                 if (key->type->request_key)
 196                         actor = key->type->request_key;
 197
 198                 ret = actor(cons, "create", aux);
 199
 200                 /* check that the actor called complete_request_key() prior to
 201                  * returning an error */
 202                 WARN_ON(ret < 0 &&
 203                         !test_bit(KEY_FLAG_REVOKED, &authkey->flags));
 204                 key_put(authkey);
 205         }
 206
 207         kleave(" = %d", ret);
 208         return ret;
 209 }
 210
 211 /*
 212  * link a key to the appropriate destination keyring
 213  * - the caller must hold a write lock on the destination keyring
 214  */
 215 static void construct_key_make_link(struct key *key, struct key *dest_keyring)
 216 {
 217         struct task_struct *tsk = current;
 218         struct key *drop = NULL;
 219
 220         kenter("{%d},%p", key->serial, dest_keyring);
 221
 222         /* find the appropriate keyring */
 223         if (!dest_keyring) {
 224                 switch (tsk->jit_keyring) {
 225                 case KEY_REQKEY_DEFL_DEFAULT:
 226                 case KEY_REQKEY_DEFL_THREAD_KEYRING:
 227                         dest_keyring = tsk->thread_keyring;
 228                         if (dest_keyring)
 229                                 break;
 230
 231                 case KEY_REQKEY_DEFL_PROCESS_KEYRING:
 232                         dest_keyring = tsk->signal->process_keyring;
 233                         if (dest_keyring)
 234                                 break;
 235
 236                 case KEY_REQKEY_DEFL_SESSION_KEYRING:
 237                         rcu_read_lock();
 238                         dest_keyring = key_get(
 239                                 rcu_dereference(tsk->signal->session_keyring));
 240                         rcu_read_unlock();
 241                         drop = dest_keyring;
 242
 243                         if (dest_keyring)
 244                                 break;
 245
 246                 case KEY_REQKEY_DEFL_USER_SESSION_KEYRING:
 247                         dest_keyring = tsk->user->session_keyring;
 248                         break;
 249
 250                 case KEY_REQKEY_DEFL_USER_KEYRING:
 251                         dest_keyring = tsk->user->uid_keyring;
 252                         break;
 253
 254                 case KEY_REQKEY_DEFL_GROUP_KEYRING:
 255                 default:
 256                         BUG();
 257                 }
 258         }
 259
 260         /* and attach the key to it */
 261         __key_link(dest_keyring, key);
 262         key_put(drop);
 263         kleave("");
 264 }
 265
 266 /*
 267  * allocate a new key in under-construction state and attempt to link it in to
 268  * the requested place
 269  * - may return a key that's already under construction instead
 270  */
 271 static int construct_alloc_key(struct key_type *type,
 272                                const char *description,
 273                                struct key *dest_keyring,
 274                                unsigned long flags,
 275                                struct key_user *user,
 276                                struct key **_key)
 277 {
 278         struct key *key;
 279         key_ref_t key_ref;
 280
 281         kenter("%s,%s,,,", type->name, description);
 282
 283         mutex_lock(&user->cons_lock);
 284
 285         key = key_alloc(type, description,
 286                         current->fsuid, current->fsgid, current, KEY_POS_ALL,
 287                         flags);
 288         if (IS_ERR(key))
 289                 goto alloc_failed;
 290
 291         set_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags);
 292
 293         if (dest_keyring)
 294                 down_write(&dest_keyring->sem);
 295
 296         /* attach the key to the destination keyring under lock, but we do need
 297          * to do another check just in case someone beat us to it whilst we
 298          * waited for locks */
 299         mutex_lock(&key_construction_mutex);
 300
 301         key_ref = search_process_keyrings(type, description, type->match,
 302                                           current);
 303         if (!IS_ERR(key_ref))
 304                 goto key_already_present;
 305
 306         if (dest_keyring)
 307                 construct_key_make_link(key, dest_keyring);
 308
 309         mutex_unlock(&key_construction_mutex);
 310         if (dest_keyring)
 311                 up_write(&dest_keyring->sem);
 312         mutex_unlock(&user->cons_lock);
 313         *_key = key;
 314         kleave(" = 0 [%d]", key_serial(key));
 315         return 0;
 316
 317 key_already_present:
 318         mutex_unlock(&key_construction_mutex);
 319         if (dest_keyring)
 320                 up_write(&dest_keyring->sem);
 321         mutex_unlock(&user->cons_lock);
 322         key_put(key);
 323         *_key = key = key_ref_to_ptr(key_ref);
 324         kleave(" = -EINPROGRESS [%d]", key_serial(key));
 325         return -EINPROGRESS;
 326
 327 alloc_failed:
 328         mutex_unlock(&user->cons_lock);
 329         *_key = NULL;
 330         kleave(" = %ld", PTR_ERR(key));
 331         return PTR_ERR(key);
 332 }
 333
 334 /*
 335  * commence key construction
 336  */
 337 static struct key *construct_key_and_link(struct key_type *type,
 338                                           const char *description,
 339                                           const char *callout_info,
 340                                           size_t callout_len,
 341                                           void *aux,
 342                                           struct key *dest_keyring,
 343                                           unsigned long flags)
 344 {
 345         struct key_user *user;
 346         struct key *key;
 347         int ret;
 348
 349         user = key_user_lookup(current->fsuid);
 350         if (!user)
 351                 return ERR_PTR(-ENOMEM);
 352
 353         ret = construct_alloc_key(type, description, dest_keyring, flags, user,
 354                                   &key);
 355         key_user_put(user);
 356
 357         if (ret == 0) {
 358                 ret = construct_key(key, callout_info, callout_len, aux);
 359                 if (ret < 0)
 360                         goto construction_failed;
 361         }
 362
 363         return key;
 364
 365 construction_failed:
 366         key_negate_and_link(key, key_negative_timeout, NULL, NULL);
 367         key_put(key);
 368         return ERR_PTR(ret);
 369 }
 370
 371 /*
 372  * request a key
 373  * - search the process's keyrings
 374  * - check the list of keys being created or updated
 375  * - call out to userspace for a key if supplementary info was provided
 376  * - cache the key in an appropriate keyring
 377  */
 378 struct key *request_key_and_link(struct key_type *type,
 379                                  const char *description,
 380                                  const void *callout_info,
 381                                  size_t callout_len,
 382                                  void *aux,
 383                                  struct key *dest_keyring,
 384                                  unsigned long flags)
 385 {
 386         struct key *key;
 387         key_ref_t key_ref;
 388
 389         kenter("%s,%s,%p,%zu,%p,%p,%lx",
 390                type->name, description, callout_info, callout_len, aux,
 391                dest_keyring, flags);
 392
 393         /* search all the process keyrings for a key */
 394         key_ref = search_process_keyrings(type, description, type->match,
 395                                           current);
 396
 397         if (!IS_ERR(key_ref)) {
 398                 key = key_ref_to_ptr(key_ref);
 399         } else if (PTR_ERR(key_ref) != -EAGAIN) {
 400                 key = ERR_CAST(key_ref);
 401         } else  {
 402                 /* the search failed, but the keyrings were searchable, so we
 403                  * should consult userspace if we can */
 404                 key = ERR_PTR(-ENOKEY);
 405                 if (!callout_info)
 406                         goto error;
 407
 408                 key = construct_key_and_link(type, description, callout_info,
 409                                              callout_len, aux, dest_keyring,
 410                                              flags);
 411         }
 412
 413 error:
 414         kleave(" = %p", key);
 415         return key;
 416 }
 417
 418 /*
 419  * wait for construction of a key to complete
 420  */
 421 int wait_for_key_construction(struct key *key, bool intr)
 422 {
 423         int ret;
 424
 425         ret = wait_on_bit(&key->flags, KEY_FLAG_USER_CONSTRUCT,
 426                           intr ? key_wait_bit_intr : key_wait_bit,
 427                           intr ? TASK_INTERRUPTIBLE : TASK_UNINTERRUPTIBLE);
 428         if (ret < 0)
 429                 return ret;
 430         return key_validate(key);
 431 }
 432 EXPORT_SYMBOL(wait_for_key_construction);
 433
 434 /*
 435  * request a key
 436  * - search the process's keyrings
 437  * - check the list of keys being created or updated
 438  * - call out to userspace for a key if supplementary info was provided
 439  * - waits uninterruptible for creation to complete
 440  */
 441 struct key *request_key(struct key_type *type,
 442                         const char *description,
 443                         const char *callout_info)
 444 {
 445         struct key *key;
 446         size_t callout_len = 0;
 447         int ret;
 448
 449         if (callout_info)
 450                 callout_len = strlen(callout_info);
 451         key = request_key_and_link(type, description, callout_info, callout_len,
 452                                    NULL, NULL, KEY_ALLOC_IN_QUOTA);
 453         if (!IS_ERR(key)) {
 454                 ret = wait_for_key_construction(key, false);
 455                 if (ret < 0) {
 456                         key_put(key);
 457                         return ERR_PTR(ret);
 458                 }
 459         }
 460         return key;
 461 }
 462 EXPORT_SYMBOL(request_key);
 463
 464 /*
 465  * request a key with auxiliary data for the upcaller
 466  * - search the process's keyrings
 467  * - check the list of keys being created or updated
 468  * - call out to userspace for a key if supplementary info was provided
 469  * - waits uninterruptible for creation to complete
 470  */
 471 struct key *request_key_with_auxdata(struct key_type *type,
 472                                      const char *description,
 473                                      const void *callout_info,
 474                                      size_t callout_len,
 475                                      void *aux)
 476 {
 477         struct key *key;
 478         int ret;
 479
 480         key = request_key_and_link(type, description, callout_info, callout_len,
 481                                    aux, NULL, KEY_ALLOC_IN_QUOTA);
 482         if (!IS_ERR(key)) {
 483                 ret = wait_for_key_construction(key, false);
 484                 if (ret < 0) {
 485                         key_put(key);
 486                         return ERR_PTR(ret);
 487                 }
 488         }
 489         return key;
 490 }
 491 EXPORT_SYMBOL(request_key_with_auxdata);
 492
 493 /*
 494  * request a key (allow async construction)
 495  * - search the process's keyrings
 496  * - check the list of keys being created or updated
 497  * - call out to userspace for a key if supplementary info was provided
 498  */
 499 struct key *request_key_async(struct key_type *type,
 500                               const char *description,
 501                               const void *callout_info,
 502                               size_t callout_len)
 503 {
 504         return request_key_and_link(type, description, callout_info,
 505                                     callout_len, NULL, NULL,
 506                                     KEY_ALLOC_IN_QUOTA);
 507 }
 508 EXPORT_SYMBOL(request_key_async);
 509
 510 /*
 511  * request a key with auxiliary data for the upcaller (allow async construction)
 512  * - search the process's keyrings
 513  * - check the list of keys being created or updated
 514  * - call out to userspace for a key if supplementary info was provided
 515  */
 516 struct key *request_key_async_with_auxdata(struct key_type *type,
 517                                            const char *description,
 518                                            const void *callout_info,
 519                                            size_t callout_len,
 520                                            void *aux)
 521 {
 522         return request_key_and_link(type, description, callout_info,
 523                                     callout_len, aux, NULL, KEY_ALLOC_IN_QUOTA);
 524 }
 525 EXPORT_SYMBOL(request_key_async_with_auxdata);