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