security/keys/request_key.c

   1 /* request_key.c: request a key from userspace
   2  *
   3  * Copyright (C) 2004-5 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 {
  38         struct task_struct *tsk = current;
  39         key_serial_t prkey, sskey;
  40         struct key *keyring;
  41         char *argv[9], *envp[3], uid_str[12], gid_str[12];
  42         char key_str[12], keyring_str[3][12];
  43         char desc[20];
  44         int ret, i;
  45
  46         kenter("{%d},{%d},%s", key->serial, authkey->serial, op);
  47
  48         /* allocate a new session keyring */
  49         sprintf(desc, "_req.%u", key->serial);
  50
  51         keyring = keyring_alloc(desc, current->fsuid, current->fsgid,
  52                                 current, 1, NULL);
  53         if (IS_ERR(keyring)) {
  54                 ret = PTR_ERR(keyring);
  55                 goto error_alloc;
  56         }
  57
  58         /* attach the auth key to the session keyring */
  59         ret = __key_link(keyring, authkey);
  60         if (ret < 0)
  61                 goto error_link;
  62
  63         /* record the UID and GID */
  64         sprintf(uid_str, "%d", current->fsuid);
  65         sprintf(gid_str, "%d", current->fsgid);
  66
  67         /* we say which key is under construction */
  68         sprintf(key_str, "%d", key->serial);
  69
  70         /* we specify the process's default keyrings */
  71         sprintf(keyring_str[0], "%d",
  72                 tsk->thread_keyring ? tsk->thread_keyring->serial : 0);
  73
  74         prkey = 0;
  75         if (tsk->signal->process_keyring)
  76                 prkey = tsk->signal->process_keyring->serial;
  77
  78         sprintf(keyring_str[1], "%d", prkey);
  79
  80         if (tsk->signal->session_keyring) {
  81                 rcu_read_lock();
  82                 sskey = rcu_dereference(tsk->signal->session_keyring)->serial;
  83                 rcu_read_unlock();
  84         }
  85         else {
  86                 sskey = tsk->user->session_keyring->serial;
  87         }
  88
  89         sprintf(keyring_str[2], "%d", sskey);
  90
  91         /* set up a minimal environment */
  92         i = 0;
  93         envp[i++] = "HOME=/";
  94         envp[i++] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
  95         envp[i] = NULL;
  96
  97         /* set up the argument list */
  98         i = 0;
  99         argv[i++] = "/sbin/request-key";
 100         argv[i++] = (char *) op;
 101         argv[i++] = key_str;
 102         argv[i++] = uid_str;
 103         argv[i++] = gid_str;
 104         argv[i++] = keyring_str[0];
 105         argv[i++] = keyring_str[1];
 106         argv[i++] = keyring_str[2];
 107         argv[i] = NULL;
 108
 109         /* do it */
 110         ret = call_usermodehelper_keys(argv[0], argv, envp, keyring, 1);
 111
 112 error_link:
 113         key_put(keyring);
 114
 115 error_alloc:
 116         kleave(" = %d", ret);
 117         return ret;
 118
 119 } /* end call_sbin_request_key() */
 120
 121 /*****************************************************************************/
 122 /*
 123  * call out to userspace for the key
 124  * - called with the construction sem held, but the sem is dropped here
 125  * - we ignore program failure and go on key status instead
 126  */
 127 static struct key *__request_key_construction(struct key_type *type,
 128                                               const char *description,
 129                                               const char *callout_info)
 130 {
 131         request_key_actor_t actor;
 132         struct key_construction cons;
 133         struct timespec now;
 134         struct key *key, *authkey;
 135         int ret, negated;
 136
 137         kenter("%s,%s,%s", type->name, description, callout_info);
 138
 139         /* create a key and add it to the queue */
 140         key = key_alloc(type, description,
 141                         current->fsuid, current->fsgid,
 142                         current, KEY_POS_ALL, 0);
 143         if (IS_ERR(key))
 144                 goto alloc_failed;
 145
 146         set_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags);
 147
 148         cons.key = key;
 149         list_add_tail(&cons.link, &key->user->consq);
 150
 151         /* we drop the construction sem here on behalf of the caller */
 152         up_write(&key_construction_sem);
 153
 154         /* allocate an authorisation key */
 155         authkey = request_key_auth_new(key, callout_info);
 156         if (IS_ERR(authkey)) {
 157                 ret = PTR_ERR(authkey);
 158                 authkey = NULL;
 159                 goto alloc_authkey_failed;
 160         }
 161
 162         /* make the call */
 163         actor = call_sbin_request_key;
 164         if (type->request_key)
 165                 actor = type->request_key;
 166         ret = actor(key, authkey, "create");
 167         if (ret < 0)
 168                 goto request_failed;
 169
 170         /* if the key wasn't instantiated, then we want to give an error */
 171         ret = -ENOKEY;
 172         if (!test_bit(KEY_FLAG_INSTANTIATED, &key->flags))
 173                 goto request_failed;
 174
 175         key_revoke(authkey);
 176         key_put(authkey);
 177
 178         down_write(&key_construction_sem);
 179         list_del(&cons.link);
 180         up_write(&key_construction_sem);
 181
 182         /* also give an error if the key was negatively instantiated */
 183 check_not_negative:
 184         if (test_bit(KEY_FLAG_NEGATIVE, &key->flags)) {
 185                 key_put(key);
 186                 key = ERR_PTR(-ENOKEY);
 187         }
 188
 189 out:
 190         kleave(" = %p", key);
 191         return key;
 192
 193 request_failed:
 194         key_revoke(authkey);
 195         key_put(authkey);
 196
 197 alloc_authkey_failed:
 198         /* it wasn't instantiated
 199          * - remove from construction queue
 200          * - mark the key as dead
 201          */
 202         negated = 0;
 203         down_write(&key_construction_sem);
 204
 205         list_del(&cons.link);
 206
 207         /* check it didn't get instantiated between the check and the down */
 208         if (!test_bit(KEY_FLAG_INSTANTIATED, &key->flags)) {
 209                 set_bit(KEY_FLAG_NEGATIVE, &key->flags);
 210                 set_bit(KEY_FLAG_INSTANTIATED, &key->flags);
 211                 negated = 1;
 212         }
 213
 214         clear_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags);
 215
 216         up_write(&key_construction_sem);
 217
 218         if (!negated)
 219                 goto check_not_negative; /* surprisingly, the key got
 220                                           * instantiated */
 221
 222         /* set the timeout and store in the session keyring if we can */
 223         now = current_kernel_time();
 224         key->expiry = now.tv_sec + key_negative_timeout;
 225
 226         if (current->signal->session_keyring) {
 227                 struct key *keyring;
 228
 229                 rcu_read_lock();
 230                 keyring = rcu_dereference(current->signal->session_keyring);
 231                 atomic_inc(&keyring->usage);
 232                 rcu_read_unlock();
 233
 234                 key_link(keyring, key);
 235                 key_put(keyring);
 236         }
 237
 238         key_put(key);
 239
 240         /* notify anyone who was waiting */
 241         wake_up_all(&request_key_conswq);
 242
 243         key = ERR_PTR(ret);
 244         goto out;
 245
 246 alloc_failed:
 247         up_write(&key_construction_sem);
 248         goto out;
 249
 250 } /* end __request_key_construction() */
 251
 252 /*****************************************************************************/
 253 /*
 254  * call out to userspace to request the key
 255  * - we check the construction queue first to see if an appropriate key is
 256  *   already being constructed by userspace
 257  */
 258 static struct key *request_key_construction(struct key_type *type,
 259                                             const char *description,
 260                                             struct key_user *user,
 261                                             const char *callout_info)
 262 {
 263         struct key_construction *pcons;
 264         struct key *key, *ckey;
 265
 266         DECLARE_WAITQUEUE(myself, current);
 267
 268         kenter("%s,%s,{%d},%s",
 269                type->name, description, user->uid, callout_info);
 270
 271         /* see if there's such a key under construction already */
 272         down_write(&key_construction_sem);
 273
 274         list_for_each_entry(pcons, &user->consq, link) {
 275                 ckey = pcons->key;
 276
 277                 if (ckey->type != type)
 278                         continue;
 279
 280                 if (type->match(ckey, description))
 281                         goto found_key_under_construction;
 282         }
 283
 284         /* see about getting userspace to construct the key */
 285         key = __request_key_construction(type, description, callout_info);
 286  error:
 287         kleave(" = %p", key);
 288         return key;
 289
 290         /* someone else has the same key under construction
 291          * - we want to keep an eye on their key
 292          */
 293  found_key_under_construction:
 294         atomic_inc(&ckey->usage);
 295         up_write(&key_construction_sem);
 296
 297         /* wait for the key to be completed one way or another */
 298         add_wait_queue(&request_key_conswq, &myself);
 299
 300         for (;;) {
 301                 set_current_state(TASK_INTERRUPTIBLE);
 302                 if (!test_bit(KEY_FLAG_USER_CONSTRUCT, &ckey->flags))
 303                         break;
 304                 if (signal_pending(current))
 305                         break;
 306                 schedule();
 307         }
 308
 309         set_current_state(TASK_RUNNING);
 310         remove_wait_queue(&request_key_conswq, &myself);
 311
 312         /* we'll need to search this process's keyrings to see if the key is
 313          * now there since we can't automatically assume it's also available
 314          * there */
 315         key_put(ckey);
 316         ckey = NULL;
 317
 318         key = NULL; /* request a retry */
 319         goto error;
 320
 321 } /* end request_key_construction() */
 322
 323 /*****************************************************************************/
 324 /*
 325  * link a freshly minted key to an appropriate destination keyring
 326  */
 327 static void request_key_link(struct key *key, struct key *dest_keyring)
 328 {
 329         struct task_struct *tsk = current;
 330         struct key *drop = NULL;
 331
 332         kenter("{%d},%p", key->serial, dest_keyring);
 333
 334         /* find the appropriate keyring */
 335         if (!dest_keyring) {
 336                 switch (tsk->jit_keyring) {
 337                 case KEY_REQKEY_DEFL_DEFAULT:
 338                 case KEY_REQKEY_DEFL_THREAD_KEYRING:
 339                         dest_keyring = tsk->thread_keyring;
 340                         if (dest_keyring)
 341                                 break;
 342
 343                 case KEY_REQKEY_DEFL_PROCESS_KEYRING:
 344                         dest_keyring = tsk->signal->process_keyring;
 345                         if (dest_keyring)
 346                                 break;
 347
 348                 case KEY_REQKEY_DEFL_SESSION_KEYRING:
 349                         rcu_read_lock();
 350                         dest_keyring = key_get(
 351                                 rcu_dereference(tsk->signal->session_keyring));
 352                         rcu_read_unlock();
 353                         drop = dest_keyring;
 354
 355                         if (dest_keyring)
 356                                 break;
 357
 358                 case KEY_REQKEY_DEFL_USER_SESSION_KEYRING:
 359                         dest_keyring = current->user->session_keyring;
 360                         break;
 361
 362                 case KEY_REQKEY_DEFL_USER_KEYRING:
 363                         dest_keyring = current->user->uid_keyring;
 364                         break;
 365
 366                 case KEY_REQKEY_DEFL_GROUP_KEYRING:
 367                 default:
 368                         BUG();
 369                 }
 370         }
 371
 372         /* and attach the key to it */
 373         key_link(dest_keyring, key);
 374
 375         key_put(drop);
 376
 377         kleave("");
 378
 379 } /* end request_key_link() */
 380
 381 /*****************************************************************************/
 382 /*
 383  * request a key
 384  * - search the process's keyrings
 385  * - check the list of keys being created or updated
 386  * - call out to userspace for a key if supplementary info was provided
 387  * - cache the key in an appropriate keyring
 388  */
 389 struct key *request_key_and_link(struct key_type *type,
 390                                  const char *description,
 391                                  const char *callout_info,
 392                                  struct key *dest_keyring)
 393 {
 394         struct key_user *user;
 395         struct key *key;
 396         key_ref_t key_ref;
 397
 398         kenter("%s,%s,%s,%p",
 399                type->name, description, callout_info, dest_keyring);
 400
 401         /* search all the process keyrings for a key */
 402         key_ref = search_process_keyrings(type, description, type->match,
 403                                           current);
 404
 405         kdebug("search 1: %p", key_ref);
 406
 407         if (!IS_ERR(key_ref)) {
 408                 key = key_ref_to_ptr(key_ref);
 409         }
 410         else if (PTR_ERR(key_ref) != -EAGAIN) {
 411                 key = ERR_PTR(PTR_ERR(key_ref));
 412         }
 413         else  {
 414                 /* the search failed, but the keyrings were searchable, so we
 415                  * should consult userspace if we can */
 416                 key = ERR_PTR(-ENOKEY);
 417                 if (!callout_info)
 418                         goto error;
 419
 420                 /* - get hold of the user's construction queue */
 421                 user = key_user_lookup(current->fsuid);
 422                 if (!user)
 423                         goto nomem;
 424
 425                 for (;;) {
 426                         if (signal_pending(current))
 427                                 goto interrupted;
 428
 429                         /* ask userspace (returns NULL if it waited on a key
 430                          * being constructed) */
 431                         key = request_key_construction(type, description,
 432                                                        user, callout_info);
 433                         if (key)
 434                                 break;
 435
 436                         /* someone else made the key we want, so we need to
 437                          * search again as it might now be available to us */
 438                         key_ref = search_process_keyrings(type, description,
 439                                                           type->match,
 440                                                           current);
 441
 442                         kdebug("search 2: %p", key_ref);
 443
 444                         if (!IS_ERR(key_ref)) {
 445                                 key = key_ref_to_ptr(key_ref);
 446                                 break;
 447                         }
 448
 449                         if (PTR_ERR(key_ref) != -EAGAIN) {
 450                                 key = ERR_PTR(PTR_ERR(key_ref));
 451                                 break;
 452                         }
 453                 }
 454
 455                 key_user_put(user);
 456
 457                 /* link the new key into the appropriate keyring */
 458                 if (!IS_ERR(key))
 459                         request_key_link(key, dest_keyring);
 460         }
 461
 462 error:
 463         kleave(" = %p", key);
 464         return key;
 465
 466 nomem:
 467         key = ERR_PTR(-ENOMEM);
 468         goto error;
 469
 470 interrupted:
 471         key_user_put(user);
 472         key = ERR_PTR(-EINTR);
 473         goto error;
 474
 475 } /* end request_key_and_link() */
 476
 477 /*****************************************************************************/
 478 /*
 479  * request a key
 480  * - search the process's keyrings
 481  * - check the list of keys being created or updated
 482  * - call out to userspace for a key if supplementary info was provided
 483  */
 484 struct key *request_key(struct key_type *type,
 485                         const char *description,
 486                         const char *callout_info)
 487 {
 488         return request_key_and_link(type, description, callout_info, NULL);
 489
 490 } /* end request_key() */
 491
 492 EXPORT_SYMBOL(request_key);