security/keys/request_key.c

   1 /* request_key.c: request a key from userspace
   2  *
   3  * Copyright (C) 2004-6 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 "internal.h"
  20
  21 struct key_construction {
  22         struct list_head        link;   /* link in construction queue */
  23         struct key              *key;   /* key being constructed */
  24 };
  25
  26 /* when waiting for someone else's keys, you get added to this */
  27 DECLARE_WAIT_QUEUE_HEAD(request_key_conswq);
  28
  29 /*****************************************************************************/
  30 /*
  31  * request userspace finish the construction of a key
  32  * - execute "/sbin/request-key <op> <key> <uid> <gid> <keyring> <keyring> <keyring>"
  33  */
  34 static int call_sbin_request_key(struct key *key,
  35                                  struct key *authkey,
  36                                  const char *op,
  37                                  void *aux)
  38 {
  39         struct task_struct *tsk = current;
  40         key_serial_t prkey, sskey;
  41         struct key *keyring;
  42         char *argv[9], *envp[3], uid_str[12], gid_str[12];
  43         char key_str[12], keyring_str[3][12];
  44         char desc[20];
  45         int ret, i;
  46
  47         kenter("{%d},{%d},%s", key->serial, authkey->serial, op);
  48
  49         /* allocate a new session keyring */
  50         sprintf(desc, "_req.%u", key->serial);
  51
  52         keyring = keyring_alloc(desc, current->fsuid, current->fsgid, current,
  53                                 KEY_ALLOC_QUOTA_OVERRUN, NULL);
  54         if (IS_ERR(keyring)) {
  55                 ret = PTR_ERR(keyring);
  56                 goto error_alloc;
  57         }
  58
  59         /* attach the auth key to the session keyring */
  60         ret = __key_link(keyring, authkey);
  61         if (ret < 0)
  62                 goto error_link;
  63
  64         /* record the UID and GID */
  65         sprintf(uid_str, "%d", current->fsuid);
  66         sprintf(gid_str, "%d", current->fsgid);
  67
  68         /* we say which key is under construction */
  69         sprintf(key_str, "%d", key->serial);
  70
  71         /* we specify the process's default keyrings */
  72         sprintf(keyring_str[0], "%d",
  73                 tsk->thread_keyring ? tsk->thread_keyring->serial : 0);
  74
  75         prkey = 0;
  76         if (tsk->signal->process_keyring)
  77                 prkey = tsk->signal->process_keyring->serial;
  78
  79         sprintf(keyring_str[1], "%d", prkey);
  80
  81         if (tsk->signal->session_keyring) {
  82                 rcu_read_lock();
  83                 sskey = rcu_dereference(tsk->signal->session_keyring)->serial;
  84                 rcu_read_unlock();
  85         }
  86         else {
  87                 sskey = tsk->user->session_keyring->serial;
  88         }
  89
  90         sprintf(keyring_str[2], "%d", sskey);
  91
  92         /* set up a minimal environment */
  93         i = 0;
  94         envp[i++] = "HOME=/";
  95         envp[i++] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
  96         envp[i] = NULL;
  97
  98         /* set up the argument list */
  99         i = 0;
 100         argv[i++] = "/sbin/request-key";
 101         argv[i++] = (char *) op;
 102         argv[i++] = key_str;
 103         argv[i++] = uid_str;
 104         argv[i++] = gid_str;
 105         argv[i++] = keyring_str[0];
 106         argv[i++] = keyring_str[1];
 107         argv[i++] = keyring_str[2];
 108         argv[i] = NULL;
 109
 110         /* do it */
 111         ret = call_usermodehelper_keys(argv[0], argv, envp, keyring, 1);
 112
 113 error_link:
 114         key_put(keyring);
 115
 116 error_alloc:
 117         kleave(" = %d", ret);
 118         return ret;
 119
 120 } /* end call_sbin_request_key() */
 121
 122 /*****************************************************************************/
 123 /*
 124  * call out to userspace for the key
 125  * - called with the construction sem held, but the sem is dropped here
 126  * - we ignore program failure and go on key status instead
 127  */
 128 static struct key *__request_key_construction(struct key_type *type,
 129                                               const char *description,
 130                                               const char *callout_info,
 131                                               void *aux,
 132                                               unsigned long flags)
 133 {
 134         request_key_actor_t actor;
 135         struct key_construction cons;
 136         struct timespec now;
 137         struct key *key, *authkey;
 138         int ret, negated;
 139
 140         kenter("%s,%s,%s,%lx", type->name, description, callout_info, flags);
 141
 142         /* create a key and add it to the queue */
 143         key = key_alloc(type, description,
 144                         current->fsuid, current->fsgid, current, KEY_POS_ALL,
 145                         flags);
 146         if (IS_ERR(key))
 147                 goto alloc_failed;
 148
 149         set_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags);
 150
 151         cons.key = key;
 152         list_add_tail(&cons.link, &key->user->consq);
 153
 154         /* we drop the construction sem here on behalf of the caller */
 155         up_write(&key_construction_sem);
 156
 157         /* allocate an authorisation key */
 158         authkey = request_key_auth_new(key, callout_info);
 159         if (IS_ERR(authkey)) {
 160                 ret = PTR_ERR(authkey);
 161                 authkey = NULL;
 162                 goto alloc_authkey_failed;
 163         }
 164
 165         /* make the call */
 166         actor = call_sbin_request_key;
 167         if (type->request_key)
 168                 actor = type->request_key;
 169         ret = actor(key, authkey, "create", aux);
 170         if (ret < 0)
 171                 goto request_failed;
 172
 173         /* if the key wasn't instantiated, then we want to give an error */
 174         ret = -ENOKEY;
 175         if (!test_bit(KEY_FLAG_INSTANTIATED, &key->flags))
 176                 goto request_failed;
 177
 178         key_revoke(authkey);
 179         key_put(authkey);
 180
 181         down_write(&key_construction_sem);
 182         list_del(&cons.link);
 183         up_write(&key_construction_sem);
 184
 185         /* also give an error if the key was negatively instantiated */
 186 check_not_negative:
 187         if (test_bit(KEY_FLAG_NEGATIVE, &key->flags)) {
 188                 key_put(key);
 189                 key = ERR_PTR(-ENOKEY);
 190         }
 191
 192 out:
 193         kleave(" = %p", key);
 194         return key;
 195
 196 request_failed:
 197         key_revoke(authkey);
 198         key_put(authkey);
 199
 200 alloc_authkey_failed:
 201         /* it wasn't instantiated
 202          * - remove from construction queue
 203          * - mark the key as dead
 204          */
 205         negated = 0;
 206         down_write(&key_construction_sem);
 207
 208         list_del(&cons.link);
 209
 210         /* check it didn't get instantiated between the check and the down */
 211         if (!test_bit(KEY_FLAG_INSTANTIATED, &key->flags)) {
 212                 set_bit(KEY_FLAG_NEGATIVE, &key->flags);
 213                 set_bit(KEY_FLAG_INSTANTIATED, &key->flags);
 214                 negated = 1;
 215         }
 216
 217         clear_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags);
 218
 219         up_write(&key_construction_sem);
 220
 221         if (!negated)
 222                 goto check_not_negative; /* surprisingly, the key got
 223                                           * instantiated */
 224
 225         /* set the timeout and store in the session keyring if we can */
 226         now = current_kernel_time();
 227         key->expiry = now.tv_sec + key_negative_timeout;
 228
 229         if (current->signal->session_keyring) {
 230                 struct key *keyring;
 231
 232                 rcu_read_lock();
 233                 keyring = rcu_dereference(current->signal->session_keyring);
 234                 atomic_inc(&keyring->usage);
 235                 rcu_read_unlock();
 236
 237                 key_link(keyring, key);
 238                 key_put(keyring);
 239         }
 240
 241         key_put(key);
 242
 243         /* notify anyone who was waiting */
 244         wake_up_all(&request_key_conswq);
 245
 246         key = ERR_PTR(ret);
 247         goto out;
 248
 249 alloc_failed:
 250         up_write(&key_construction_sem);
 251         goto out;
 252
 253 } /* end __request_key_construction() */
 254
 255 /*****************************************************************************/
 256 /*
 257  * call out to userspace to request the key
 258  * - we check the construction queue first to see if an appropriate key is
 259  *   already being constructed by userspace
 260  */
 261 static struct key *request_key_construction(struct key_type *type,
 262                                             const char *description,
 263                                             const char *callout_info,
 264                                             void *aux,
 265                                             struct key_user *user,
 266                                             unsigned long flags)
 267 {
 268         struct key_construction *pcons;
 269         struct key *key, *ckey;
 270
 271         DECLARE_WAITQUEUE(myself, current);
 272
 273         kenter("%s,%s,{%d},%s,%lx",
 274                type->name, description, user->uid, callout_info, flags);
 275
 276         /* see if there's such a key under construction already */
 277         down_write(&key_construction_sem);
 278
 279         list_for_each_entry(pcons, &user->consq, link) {
 280                 ckey = pcons->key;
 281
 282                 if (ckey->type != type)
 283                         continue;
 284
 285                 if (type->match(ckey, description))
 286                         goto found_key_under_construction;
 287         }
 288
 289         /* see about getting userspace to construct the key */
 290         key = __request_key_construction(type, description, callout_info, aux,
 291                                          flags);
 292  error:
 293         kleave(" = %p", key);
 294         return key;
 295
 296         /* someone else has the same key under construction
 297          * - we want to keep an eye on their key
 298          */
 299  found_key_under_construction:
 300         atomic_inc(&ckey->usage);
 301         up_write(&key_construction_sem);
 302
 303         /* wait for the key to be completed one way or another */
 304         add_wait_queue(&request_key_conswq, &myself);
 305
 306         for (;;) {
 307                 set_current_state(TASK_INTERRUPTIBLE);
 308                 if (!test_bit(KEY_FLAG_USER_CONSTRUCT, &ckey->flags))
 309                         break;
 310                 if (signal_pending(current))
 311                         break;
 312                 schedule();
 313         }
 314
 315         set_current_state(TASK_RUNNING);
 316         remove_wait_queue(&request_key_conswq, &myself);
 317
 318         /* we'll need to search this process's keyrings to see if the key is
 319          * now there since we can't automatically assume it's also available
 320          * there */
 321         key_put(ckey);
 322         ckey = NULL;
 323
 324         key = NULL; /* request a retry */
 325         goto error;
 326
 327 } /* end request_key_construction() */
 328
 329 /*****************************************************************************/
 330 /*
 331  * link a freshly minted key to an appropriate destination keyring
 332  */
 333 static void request_key_link(struct key *key, struct key *dest_keyring)
 334 {
 335         struct task_struct *tsk = current;
 336         struct key *drop = NULL;
 337
 338         kenter("{%d},%p", key->serial, dest_keyring);
 339
 340         /* find the appropriate keyring */
 341         if (!dest_keyring) {
 342                 switch (tsk->jit_keyring) {
 343                 case KEY_REQKEY_DEFL_DEFAULT:
 344                 case KEY_REQKEY_DEFL_THREAD_KEYRING:
 345                         dest_keyring = tsk->thread_keyring;
 346                         if (dest_keyring)
 347                                 break;
 348
 349                 case KEY_REQKEY_DEFL_PROCESS_KEYRING:
 350                         dest_keyring = tsk->signal->process_keyring;
 351                         if (dest_keyring)
 352                                 break;
 353
 354                 case KEY_REQKEY_DEFL_SESSION_KEYRING:
 355                         rcu_read_lock();
 356                         dest_keyring = key_get(
 357                                 rcu_dereference(tsk->signal->session_keyring));
 358                         rcu_read_unlock();
 359                         drop = dest_keyring;
 360
 361                         if (dest_keyring)
 362                                 break;
 363
 364                 case KEY_REQKEY_DEFL_USER_SESSION_KEYRING:
 365                         dest_keyring = current->user->session_keyring;
 366                         break;
 367
 368                 case KEY_REQKEY_DEFL_USER_KEYRING:
 369                         dest_keyring = current->user->uid_keyring;
 370                         break;
 371
 372                 case KEY_REQKEY_DEFL_GROUP_KEYRING:
 373                 default:
 374                         BUG();
 375                 }
 376         }
 377
 378         /* and attach the key to it */
 379         key_link(dest_keyring, key);
 380
 381         key_put(drop);
 382
 383         kleave("");
 384
 385 } /* end request_key_link() */
 386
 387 /*****************************************************************************/
 388 /*
 389  * request a key
 390  * - search the process's keyrings
 391  * - check the list of keys being created or updated
 392  * - call out to userspace for a key if supplementary info was provided
 393  * - cache the key in an appropriate keyring
 394  */
 395 struct key *request_key_and_link(struct key_type *type,
 396                                  const char *description,
 397                                  const char *callout_info,
 398                                  void *aux,
 399                                  struct key *dest_keyring,
 400                                  unsigned long flags)
 401 {
 402         struct key_user *user;
 403         struct key *key;
 404         key_ref_t key_ref;
 405
 406         kenter("%s,%s,%s,%p,%p,%lx",
 407                type->name, description, callout_info, aux,
 408                dest_keyring, flags);
 409
 410         /* search all the process keyrings for a key */
 411         key_ref = search_process_keyrings(type, description, type->match,
 412                                           current);
 413
 414         kdebug("search 1: %p", key_ref);
 415
 416         if (!IS_ERR(key_ref)) {
 417                 key = key_ref_to_ptr(key_ref);
 418         }
 419         else if (PTR_ERR(key_ref) != -EAGAIN) {
 420                 key = ERR_PTR(PTR_ERR(key_ref));
 421         }
 422         else  {
 423                 /* the search failed, but the keyrings were searchable, so we
 424                  * should consult userspace if we can */
 425                 key = ERR_PTR(-ENOKEY);
 426                 if (!callout_info)
 427                         goto error;
 428
 429                 /* - get hold of the user's construction queue */
 430                 user = key_user_lookup(current->fsuid);
 431                 if (!user)
 432                         goto nomem;
 433
 434                 for (;;) {
 435                         if (signal_pending(current))
 436                                 goto interrupted;
 437
 438                         /* ask userspace (returns NULL if it waited on a key
 439                          * being constructed) */
 440                         key = request_key_construction(type, description,
 441                                                        callout_info, aux,
 442                                                        user, flags);
 443                         if (key)
 444                                 break;
 445
 446                         /* someone else made the key we want, so we need to
 447                          * search again as it might now be available to us */
 448                         key_ref = search_process_keyrings(type, description,
 449                                                           type->match,
 450                                                           current);
 451
 452                         kdebug("search 2: %p", key_ref);
 453
 454                         if (!IS_ERR(key_ref)) {
 455                                 key = key_ref_to_ptr(key_ref);
 456                                 break;
 457                         }
 458
 459                         if (PTR_ERR(key_ref) != -EAGAIN) {
 460                                 key = ERR_PTR(PTR_ERR(key_ref));
 461                                 break;
 462                         }
 463                 }
 464
 465                 key_user_put(user);
 466
 467                 /* link the new key into the appropriate keyring */
 468                 if (!IS_ERR(key))
 469                         request_key_link(key, dest_keyring);
 470         }
 471
 472 error:
 473         kleave(" = %p", key);
 474         return key;
 475
 476 nomem:
 477         key = ERR_PTR(-ENOMEM);
 478         goto error;
 479
 480 interrupted:
 481         key_user_put(user);
 482         key = ERR_PTR(-EINTR);
 483         goto error;
 484
 485 } /* end request_key_and_link() */
 486
 487 /*****************************************************************************/
 488 /*
 489  * request a key
 490  * - search the process's keyrings
 491  * - check the list of keys being created or updated
 492  * - call out to userspace for a key if supplementary info was provided
 493  */
 494 struct key *request_key(struct key_type *type,
 495                         const char *description,
 496                         const char *callout_info)
 497 {
 498         return request_key_and_link(type, description, callout_info, NULL,
 499                                     NULL, KEY_ALLOC_IN_QUOTA);
 500
 501 } /* end request_key() */
 502
 503 EXPORT_SYMBOL(request_key);
 504
 505 /*****************************************************************************/
 506 /*
 507  * request a key with auxiliary data for the upcaller
 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_with_auxdata(struct key_type *type,
 513                                      const char *description,
 514                                      const char *callout_info,
 515                                      void *aux)
 516 {
 517         return request_key_and_link(type, description, callout_info, aux,
 518                                     NULL, KEY_ALLOC_IN_QUOTA);
 519
 520 } /* end request_key_with_auxdata() */
 521
 522 EXPORT_SYMBOL(request_key_with_auxdata);