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 "internal.h"
  20
  21 /*
  22  * wait_on_bit() sleep function for uninterruptible waiting
  23  */
  24 static int key_wait_bit(void *flags)
  25 {
  26         schedule();
  27         return 0;
  28 }
  29
  30 /*
  31  * wait_on_bit() sleep function for interruptible waiting
  32  */
  33 static int key_wait_bit_intr(void *flags)
  34 {
  35         schedule();
  36         return signal_pending(current) ? -ERESTARTSYS : 0;
  37 }
  38
  39 /*
  40  * call to complete the construction of a key
  41  */
  42 void complete_request_key(struct key_construction *cons, int error)
  43 {
  44         kenter("{%d,%d},%d", cons->key->serial, cons->authkey->serial, error);
  45
  46         if (error < 0)
  47                 key_negate_and_link(cons->key, key_negative_timeout, NULL,
  48                                     cons->authkey);
  49         else
  50                 key_revoke(cons->authkey);
  51
  52         key_put(cons->key);
  53         key_put(cons->authkey);
  54         kfree(cons);
  55 }
  56 EXPORT_SYMBOL(complete_request_key);
  57
  58 /*
  59  * request userspace finish the construction of a key
  60  * - execute "/sbin/request-key <op> <key> <uid> <gid> <keyring> <keyring> <keyring>"
  61  */
  62 static int call_sbin_request_key(struct key_construction *cons,
  63                                  const char *op,
  64                                  void *aux)
  65 {
  66         struct task_struct *tsk = current;
  67         key_serial_t prkey, sskey;
  68         struct key *key = cons->key, *authkey = cons->authkey, *keyring;
  69         char *argv[9], *envp[3], uid_str[12], gid_str[12];
  70         char key_str[12], keyring_str[3][12];
  71         char desc[20];
  72         int ret, i;
  73
  74         kenter("{%d},{%d},%s", key->serial, authkey->serial, op);
  75
  76         /* allocate a new session keyring */
  77         sprintf(desc, "_req.%u", key->serial);
  78
  79         keyring = keyring_alloc(desc, current->fsuid, current->fsgid, current,
  80                                 KEY_ALLOC_QUOTA_OVERRUN, NULL);
  81         if (IS_ERR(keyring)) {
  82                 ret = PTR_ERR(keyring);
  83                 goto error_alloc;
  84         }
  85
  86         /* attach the auth key to the session keyring */
  87         ret = __key_link(keyring, authkey);
  88         if (ret < 0)
  89                 goto error_link;
  90
  91         /* record the UID and GID */
  92         sprintf(uid_str, "%d", current->fsuid);
  93         sprintf(gid_str, "%d", current->fsgid);
  94
  95         /* we say which key is under construction */
  96         sprintf(key_str, "%d", key->serial);
  97
  98         /* we specify the process's default keyrings */
  99         sprintf(keyring_str[0], "%d",
 100                 tsk->thread_keyring ? tsk->thread_keyring->serial : 0);
 101
 102         prkey = 0;
 103         if (tsk->signal->process_keyring)
 104                 prkey = tsk->signal->process_keyring->serial;
 105
 106         sprintf(keyring_str[1], "%d", prkey);
 107
 108         if (tsk->signal->session_keyring) {
 109                 rcu_read_lock();
 110                 sskey = rcu_dereference(tsk->signal->session_keyring)->serial;
 111                 rcu_read_unlock();
 112         } else {
 113                 sskey = tsk->user->session_keyring->serial;
 114         }
 115
 116         sprintf(keyring_str[2], "%d", sskey);
 117
 118         /* set up a minimal environment */
 119         i = 0;
 120         envp[i++] = "HOME=/";
 121         envp[i++] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
 122         envp[i] = NULL;
 123
 124         /* set up the argument list */
 125         i = 0;
 126         argv[i++] = "/sbin/request-key";
 127         argv[i++] = (char *) op;
 128         argv[i++] = key_str;
 129         argv[i++] = uid_str;
 130         argv[i++] = gid_str;
 131         argv[i++] = keyring_str[0];
 132         argv[i++] = keyring_str[1];
 133         argv[i++] = keyring_str[2];
 134         argv[i] = NULL;
 135
 136         /* do it */
 137         ret = call_usermodehelper_keys(argv[0], argv, envp, keyring,
 138                                        UMH_WAIT_PROC);
 139         kdebug("usermode -> 0x%x", ret);
 140         if (ret >= 0) {
 141                 /* ret is the exit/wait code */
 142                 if (test_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags) ||
 143                     key_validate(key) < 0)
 144                         ret = -ENOKEY;
 145                 else
 146                         /* ignore any errors from userspace if the key was
 147                          * instantiated */
 148                         ret = 0;
 149         }
 150
 151 error_link:
 152         key_put(keyring);
 153
 154 error_alloc:
 155         kleave(" = %d", ret);
 156         complete_request_key(cons, ret);
 157         return ret;
 158 }
 159
 160 /*
 161  * call out to userspace for key construction
 162  * - we ignore program failure and go on key status instead
 163  */
 164 static int construct_key(struct key *key, const char *callout_info, void *aux)
 165 {
 166         struct key_construction *cons;
 167         request_key_actor_t actor;
 168         struct key *authkey;
 169         int ret;
 170
 171         kenter("%d,%s,%p", key->serial, callout_info, aux);
 172
 173         cons = kmalloc(sizeof(*cons), GFP_KERNEL);
 174         if (!cons)
 175                 return -ENOMEM;
 176
 177         /* allocate an authorisation key */
 178         authkey = request_key_auth_new(key, callout_info);
 179         if (IS_ERR(authkey)) {
 180                 kfree(cons);
 181                 ret = PTR_ERR(authkey);
 182                 authkey = NULL;
 183         } else {
 184                 cons->authkey = key_get(authkey);
 185                 cons->key = key_get(key);
 186
 187                 /* make the call */
 188                 actor = call_sbin_request_key;
 189                 if (key->type->request_key)
 190                         actor = key->type->request_key;
 191
 192                 ret = actor(cons, "create", aux);
 193
 194                 /* check that the actor called complete_request_key() prior to
 195                  * returning an error */
 196                 WARN_ON(ret < 0 &&
 197                         !test_bit(KEY_FLAG_REVOKED, &authkey->flags));
 198                 key_put(authkey);
 199         }
 200
 201         kleave(" = %d", ret);
 202         return ret;
 203 }
 204
 205 /*
 206  * link a key to the appropriate destination keyring
 207  * - the caller must hold a write lock on the destination keyring
 208  */
 209 static void construct_key_make_link(struct key *key, struct key *dest_keyring)
 210 {
 211         struct task_struct *tsk = current;
 212         struct key *drop = NULL;
 213
 214         kenter("{%d},%p", key->serial, dest_keyring);
 215
 216         /* find the appropriate keyring */
 217         if (!dest_keyring) {
 218                 switch (tsk->jit_keyring) {
 219                 case KEY_REQKEY_DEFL_DEFAULT:
 220                 case KEY_REQKEY_DEFL_THREAD_KEYRING:
 221                         dest_keyring = tsk->thread_keyring;
 222                         if (dest_keyring)
 223                                 break;
 224
 225                 case KEY_REQKEY_DEFL_PROCESS_KEYRING:
 226                         dest_keyring = tsk->signal->process_keyring;
 227                         if (dest_keyring)
 228                                 break;
 229
 230                 case KEY_REQKEY_DEFL_SESSION_KEYRING:
 231                         rcu_read_lock();
 232                         dest_keyring = key_get(
 233                                 rcu_dereference(tsk->signal->session_keyring));
 234                         rcu_read_unlock();
 235                         drop = dest_keyring;
 236
 237                         if (dest_keyring)
 238                                 break;
 239
 240                 case KEY_REQKEY_DEFL_USER_SESSION_KEYRING:
 241                         dest_keyring = tsk->user->session_keyring;
 242                         break;
 243
 244                 case KEY_REQKEY_DEFL_USER_KEYRING:
 245                         dest_keyring = tsk->user->uid_keyring;
 246                         break;
 247
 248                 case KEY_REQKEY_DEFL_GROUP_KEYRING:
 249                 default:
 250                         BUG();
 251                 }
 252         }
 253
 254         /* and attach the key to it */
 255         __key_link(dest_keyring, key);
 256         key_put(drop);
 257         kleave("");
 258 }
 259
 260 /*
 261  * allocate a new key in under-construction state and attempt to link it in to
 262  * the requested place
 263  * - may return a key that's already under construction instead
 264  */
 265 static int construct_alloc_key(struct key_type *type,
 266                                const char *description,
 267                                struct key *dest_keyring,
 268                                unsigned long flags,
 269                                struct key_user *user,
 270                                struct key **_key)
 271 {
 272         struct key *key;
 273         key_ref_t key_ref;
 274
 275         kenter("%s,%s,,,", type->name, description);
 276
 277         mutex_lock(&user->cons_lock);
 278
 279         key = key_alloc(type, description,
 280                         current->fsuid, current->fsgid, current, KEY_POS_ALL,
 281                         flags);
 282         if (IS_ERR(key))
 283                 goto alloc_failed;
 284
 285         set_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags);
 286
 287         if (dest_keyring)
 288                 down_write(&dest_keyring->sem);
 289
 290         /* attach the key to the destination keyring under lock, but we do need
 291          * to do another check just in case someone beat us to it whilst we
 292          * waited for locks */
 293         mutex_lock(&key_construction_mutex);
 294
 295         key_ref = search_process_keyrings(type, description, type->match,
 296                                           current);
 297         if (!IS_ERR(key_ref))
 298                 goto key_already_present;
 299
 300         if (dest_keyring)
 301                 construct_key_make_link(key, dest_keyring);
 302
 303         mutex_unlock(&key_construction_mutex);
 304         if (dest_keyring)
 305                 up_write(&dest_keyring->sem);
 306         mutex_unlock(&user->cons_lock);
 307         *_key = key;
 308         kleave(" = 0 [%d]", key_serial(key));
 309         return 0;
 310
 311 key_already_present:
 312         mutex_unlock(&key_construction_mutex);
 313         if (dest_keyring)
 314                 up_write(&dest_keyring->sem);
 315         mutex_unlock(&user->cons_lock);
 316         key_put(key);
 317         *_key = key = key_ref_to_ptr(key_ref);
 318         kleave(" = -EINPROGRESS [%d]", key_serial(key));
 319         return -EINPROGRESS;
 320
 321 alloc_failed:
 322         mutex_unlock(&user->cons_lock);
 323         *_key = NULL;
 324         kleave(" = %ld", PTR_ERR(key));
 325         return PTR_ERR(key);
 326 }
 327
 328 /*
 329  * commence key construction
 330  */
 331 static struct key *construct_key_and_link(struct key_type *type,
 332                                           const char *description,
 333                                           const char *callout_info,
 334                                           void *aux,
 335                                           struct key *dest_keyring,
 336                                           unsigned long flags)
 337 {
 338         struct key_user *user;
 339         struct key *key;
 340         int ret;
 341
 342         user = key_user_lookup(current->fsuid);
 343         if (!user)
 344                 return ERR_PTR(-ENOMEM);
 345
 346         ret = construct_alloc_key(type, description, dest_keyring, flags, user,
 347                                   &key);
 348         key_user_put(user);
 349
 350         if (ret == 0) {
 351                 ret = construct_key(key, callout_info, aux);
 352                 if (ret < 0)
 353                         goto construction_failed;
 354         }
 355
 356         return key;
 357
 358 construction_failed:
 359         key_negate_and_link(key, key_negative_timeout, NULL, NULL);
 360         key_put(key);
 361         return ERR_PTR(ret);
 362 }
 363
 364 /*
 365  * request a key
 366  * - search the process's keyrings
 367  * - check the list of keys being created or updated
 368  * - call out to userspace for a key if supplementary info was provided
 369  * - cache the key in an appropriate keyring
 370  */
 371 struct key *request_key_and_link(struct key_type *type,
 372                                  const char *description,
 373                                  const char *callout_info,
 374                                  void *aux,
 375                                  struct key *dest_keyring,
 376                                  unsigned long flags)
 377 {
 378         struct key *key;
 379         key_ref_t key_ref;
 380
 381         kenter("%s,%s,%s,%p,%p,%lx",
 382                type->name, description, callout_info, aux,
 383                dest_keyring, flags);
 384
 385         /* search all the process keyrings for a key */
 386         key_ref = search_process_keyrings(type, description, type->match,
 387                                           current);
 388
 389         if (!IS_ERR(key_ref)) {
 390                 key = key_ref_to_ptr(key_ref);
 391         } else if (PTR_ERR(key_ref) != -EAGAIN) {
 392                 key = ERR_CAST(key_ref);
 393         } else  {
 394                 /* the search failed, but the keyrings were searchable, so we
 395                  * should consult userspace if we can */
 396                 key = ERR_PTR(-ENOKEY);
 397                 if (!callout_info)
 398                         goto error;
 399
 400                 key = construct_key_and_link(type, description, callout_info,
 401                                              aux, dest_keyring, flags);
 402         }
 403
 404 error:
 405         kleave(" = %p", key);
 406         return key;
 407 }
 408
 409 /*
 410  * wait for construction of a key to complete
 411  */
 412 int wait_for_key_construction(struct key *key, bool intr)
 413 {
 414         int ret;
 415
 416         ret = wait_on_bit(&key->flags, KEY_FLAG_USER_CONSTRUCT,
 417                           intr ? key_wait_bit_intr : key_wait_bit,
 418                           intr ? TASK_INTERRUPTIBLE : TASK_UNINTERRUPTIBLE);
 419         if (ret < 0)
 420                 return ret;
 421         return key_validate(key);
 422 }
 423 EXPORT_SYMBOL(wait_for_key_construction);
 424
 425 /*
 426  * request a key
 427  * - search the process's keyrings
 428  * - check the list of keys being created or updated
 429  * - call out to userspace for a key if supplementary info was provided
 430  * - waits uninterruptible for creation to complete
 431  */
 432 struct key *request_key(struct key_type *type,
 433                         const char *description,
 434                         const char *callout_info)
 435 {
 436         struct key *key;
 437         int ret;
 438
 439         key = request_key_and_link(type, description, callout_info, NULL,
 440                                    NULL, KEY_ALLOC_IN_QUOTA);
 441         if (!IS_ERR(key)) {
 442                 ret = wait_for_key_construction(key, false);
 443                 if (ret < 0) {
 444                         key_put(key);
 445                         return ERR_PTR(ret);
 446                 }
 447         }
 448         return key;
 449 }
 450 EXPORT_SYMBOL(request_key);
 451
 452 /*
 453  * request a key with auxiliary data for the upcaller
 454  * - search the process's keyrings
 455  * - check the list of keys being created or updated
 456  * - call out to userspace for a key if supplementary info was provided
 457  * - waits uninterruptible for creation to complete
 458  */
 459 struct key *request_key_with_auxdata(struct key_type *type,
 460                                      const char *description,
 461                                      const char *callout_info,
 462                                      void *aux)
 463 {
 464         struct key *key;
 465         int ret;
 466
 467         key = request_key_and_link(type, description, callout_info, aux,
 468                                    NULL, KEY_ALLOC_IN_QUOTA);
 469         if (!IS_ERR(key)) {
 470                 ret = wait_for_key_construction(key, false);
 471                 if (ret < 0) {
 472                         key_put(key);
 473                         return ERR_PTR(ret);
 474                 }
 475         }
 476         return key;
 477 }
 478 EXPORT_SYMBOL(request_key_with_auxdata);
 479
 480 /*
 481  * request a key (allow async construction)
 482  * - search the process's keyrings
 483  * - check the list of keys being created or updated
 484  * - call out to userspace for a key if supplementary info was provided
 485  */
 486 struct key *request_key_async(struct key_type *type,
 487                               const char *description,
 488                               const char *callout_info)
 489 {
 490         return request_key_and_link(type, description, callout_info, NULL,
 491                                     NULL, KEY_ALLOC_IN_QUOTA);
 492 }
 493 EXPORT_SYMBOL(request_key_async);
 494
 495 /*
 496  * request a key with auxiliary data for the upcaller (allow async construction)
 497  * - search the process's keyrings
 498  * - check the list of keys being created or updated
 499  * - call out to userspace for a key if supplementary info was provided
 500  */
 501 struct key *request_key_async_with_auxdata(struct key_type *type,
 502                                            const char *description,
 503                                            const char *callout_info,
 504                                            void *aux)
 505 {
 506         return request_key_and_link(type, description, callout_info, aux,
 507                                     NULL, KEY_ALLOC_IN_QUOTA);
 508 }
 509 EXPORT_SYMBOL(request_key_async_with_auxdata);