security/keys/process_keys.c

   1 /* Manage a process's keyrings
   2  *
   3  * Copyright (C) 2004-2005, 2008 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
  12 #include <linux/module.h>
  13 #include <linux/init.h>
  14 #include <linux/sched.h>
  15 #include <linux/keyctl.h>
  16 #include <linux/fs.h>
  17 #include <linux/err.h>
  18 #include <linux/mutex.h>
  19 #include <linux/security.h>
  20 #include <linux/user_namespace.h>
  21 #include <asm/uaccess.h>
  22 #include "internal.h"
  23
  24 /* Session keyring create vs join semaphore */
  25 static DEFINE_MUTEX(key_session_mutex);
  26
  27 /* User keyring creation semaphore */
  28 static DEFINE_MUTEX(key_user_keyring_mutex);
  29
  30 /* The root user's tracking struct */
  31 struct key_user root_key_user = {
  32         .usage          = ATOMIC_INIT(3),
  33         .cons_lock      = __MUTEX_INITIALIZER(root_key_user.cons_lock),
  34         .lock           = __SPIN_LOCK_UNLOCKED(root_key_user.lock),
  35         .nkeys          = ATOMIC_INIT(2),
  36         .nikeys         = ATOMIC_INIT(2),
  37         .uid            = 0,
  38         .user_ns        = &init_user_ns,
  39 };
  40
  41 /*
  42  * Install the user and user session keyrings for the current process's UID.
  43  */
  44 int install_user_keyrings(void)
  45 {
  46         struct user_struct *user;
  47         const struct cred *cred;
  48         struct key *uid_keyring, *session_keyring;
  49         char buf[20];
  50         int ret;
  51
  52         cred = current_cred();
  53         user = cred->user;
  54
  55         kenter("%p{%u}", user, user->uid);
  56
  57         if (user->uid_keyring && user->session_keyring) {
  58                 kleave(" = 0 [exist]");
  59                 return 0;
  60         }
  61
  62         mutex_lock(&key_user_keyring_mutex);
  63         ret = 0;
  64
  65         if (!user->uid_keyring) {
  66                 /* get the UID-specific keyring
  67                  * - there may be one in existence already as it may have been
  68                  *   pinned by a session, but the user_struct pointing to it
  69                  *   may have been destroyed by setuid */
  70                 sprintf(buf, "_uid.%u", user->uid);
  71
  72                 uid_keyring = find_keyring_by_name(buf, true);
  73                 if (IS_ERR(uid_keyring)) {
  74                         uid_keyring = keyring_alloc(buf, user->uid, (gid_t) -1,
  75                                                     cred,
  76                                                     KEY_ALLOC_UID_KEYRING |
  77                                                         KEY_ALLOC_IN_QUOTA,
  78                                                     NULL);
  79                         if (IS_ERR(uid_keyring)) {
  80                                 ret = PTR_ERR(uid_keyring);
  81                                 goto error;
  82                         }
  83                 }
  84
  85                 /* get a default session keyring (which might also exist
  86                  * already) */
  87                 sprintf(buf, "_uid_ses.%u", user->uid);
  88
  89                 session_keyring = find_keyring_by_name(buf, true);
  90                 if (IS_ERR(session_keyring)) {
  91                         session_keyring =
  92                                 keyring_alloc(buf, user->uid, (gid_t) -1,
  93                                               cred,
  94                                               KEY_ALLOC_UID_KEYRING |
  95                                                   KEY_ALLOC_IN_QUOTA,
  96                                               NULL);
  97                         if (IS_ERR(session_keyring)) {
  98                                 ret = PTR_ERR(session_keyring);
  99                                 goto error_release;
 100                         }
 101
 102                         /* we install a link from the user session keyring to
 103                          * the user keyring */
 104                         ret = key_link(session_keyring, uid_keyring);
 105                         if (ret < 0)
 106                                 goto error_release_both;
 107                 }
 108
 109                 /* install the keyrings */
 110                 user->uid_keyring = uid_keyring;
 111                 user->session_keyring = session_keyring;
 112         }
 113
 114         mutex_unlock(&key_user_keyring_mutex);
 115         kleave(" = 0");
 116         return 0;
 117
 118 error_release_both:
 119         key_put(session_keyring);
 120 error_release:
 121         key_put(uid_keyring);
 122 error:
 123         mutex_unlock(&key_user_keyring_mutex);
 124         kleave(" = %d", ret);
 125         return ret;
 126 }
 127
 128 /*
 129  * Install a thread keyring to the given credentials struct if it didn't have
 130  * one already.  This is allowed to overrun the quota.
 131  *
 132  * Return: 0 if a thread keyring is now present; -errno on failure.
 133  */
 134 int install_thread_keyring_to_cred(struct cred *new)
 135 {
 136         struct key *keyring;
 137
 138         if (new->thread_keyring)
 139                 return 0;
 140
 141         keyring = keyring_alloc("_tid", new->uid, new->gid, new,
 142                                 KEY_ALLOC_QUOTA_OVERRUN, NULL);
 143         if (IS_ERR(keyring))
 144                 return PTR_ERR(keyring);
 145
 146         new->thread_keyring = keyring;
 147         return 0;
 148 }
 149
 150 /*
 151  * Install a thread keyring to the current task if it didn't have one already.
 152  *
 153  * Return: 0 if a thread keyring is now present; -errno on failure.
 154  */
 155 static int install_thread_keyring(void)
 156 {
 157         struct cred *new;
 158         int ret;
 159
 160         new = prepare_creds();
 161         if (!new)
 162                 return -ENOMEM;
 163
 164         ret = install_thread_keyring_to_cred(new);
 165         if (ret < 0) {
 166                 abort_creds(new);
 167                 return ret;
 168         }
 169
 170         return commit_creds(new);
 171 }
 172
 173 /*
 174  * Install a process keyring to the given credentials struct if it didn't have
 175  * one already.  This is allowed to overrun the quota.
 176  *
 177  * Return: 0 if a process keyring is now present; -errno on failure.
 178  */
 179 int install_process_keyring_to_cred(struct cred *new)
 180 {
 181         struct key *keyring;
 182         int ret;
 183
 184         if (new->tgcred->process_keyring)
 185                 return 0;
 186
 187         keyring = keyring_alloc("_pid", new->uid, new->gid,
 188                                 new, KEY_ALLOC_QUOTA_OVERRUN, NULL);
 189         if (IS_ERR(keyring))
 190                 return PTR_ERR(keyring);
 191
 192         spin_lock_irq(&new->tgcred->lock);
 193         if (!new->tgcred->process_keyring) {
 194                 new->tgcred->process_keyring = keyring;
 195                 keyring = NULL;
 196                 ret = 0;
 197         } else {
 198                 ret = -EEXIST;
 199         }
 200         spin_unlock_irq(&new->tgcred->lock);
 201         key_put(keyring);
 202         return ret;
 203 }
 204
 205 /*
 206  * Install a process keyring to the current task if it didn't have one already.
 207  *
 208  * Return: 0 if a process keyring is now present; -errno on failure.
 209  */
 210 static int install_process_keyring(void)
 211 {
 212         struct cred *new;
 213         int ret;
 214
 215         new = prepare_creds();
 216         if (!new)
 217                 return -ENOMEM;
 218
 219         ret = install_process_keyring_to_cred(new);
 220         if (ret < 0) {
 221                 abort_creds(new);
 222                 return ret;
 223         }
 224
 225         return commit_creds(new);
 226 }
 227
 228 /*
 229  * Install the given keyring as the session keyring of the given credentials
 230  * struct, replacing the existing one if any.  If the given keyring is NULL,
 231  * then install a new anonymous session keyring.
 232  *
 233  * Return: 0 on success; -errno on failure.
 234  */
 235 int install_session_keyring_to_cred(struct cred *cred, struct key *keyring)
 236 {
 237         unsigned long flags;
 238         struct key *old;
 239
 240         might_sleep();
 241
 242         /* create an empty session keyring */
 243         if (!keyring) {
 244                 flags = KEY_ALLOC_QUOTA_OVERRUN;
 245                 if (cred->tgcred->session_keyring)
 246                         flags = KEY_ALLOC_IN_QUOTA;
 247
 248                 keyring = keyring_alloc("_ses", cred->uid, cred->gid,
 249                                         cred, flags, NULL);
 250                 if (IS_ERR(keyring))
 251                         return PTR_ERR(keyring);
 252         } else {
 253                 atomic_inc(&keyring->usage);
 254         }
 255
 256         /* install the keyring */
 257         spin_lock_irq(&cred->tgcred->lock);
 258         old = cred->tgcred->session_keyring;
 259         rcu_assign_pointer(cred->tgcred->session_keyring, keyring);
 260         spin_unlock_irq(&cred->tgcred->lock);
 261
 262         /* we're using RCU on the pointer, but there's no point synchronising
 263          * on it if it didn't previously point to anything */
 264         if (old) {
 265                 synchronize_rcu();
 266                 key_put(old);
 267         }
 268
 269         return 0;
 270 }
 271
 272 /*
 273  * Install the given keyring as the session keyring of the current task,
 274  * replacing the existing one if any.  If the given keyring is NULL, then
 275  * install a new anonymous session keyring.
 276  *
 277  * Return: 0 on success; -errno on failure.
 278  */
 279 static int install_session_keyring(struct key *keyring)
 280 {
 281         struct cred *new;
 282         int ret;
 283
 284         new = prepare_creds();
 285         if (!new)
 286                 return -ENOMEM;
 287
 288         ret = install_session_keyring_to_cred(new, keyring);
 289         if (ret < 0) {
 290                 abort_creds(new);
 291                 return ret;
 292         }
 293
 294         return commit_creds(new);
 295 }
 296
 297 /*
 298  * Handle the fsuid changing.
 299  */
 300 void key_fsuid_changed(struct task_struct *tsk)
 301 {
 302         /* update the ownership of the thread keyring */
 303         BUG_ON(!tsk->cred);
 304         if (tsk->cred->thread_keyring) {
 305                 down_write(&tsk->cred->thread_keyring->sem);
 306                 tsk->cred->thread_keyring->uid = tsk->cred->fsuid;
 307                 up_write(&tsk->cred->thread_keyring->sem);
 308         }
 309 }
 310
 311 /*
 312  * Handle the fsgid changing.
 313  */
 314 void key_fsgid_changed(struct task_struct *tsk)
 315 {
 316         /* update the ownership of the thread keyring */
 317         BUG_ON(!tsk->cred);
 318         if (tsk->cred->thread_keyring) {
 319                 down_write(&tsk->cred->thread_keyring->sem);
 320                 tsk->cred->thread_keyring->gid = tsk->cred->fsgid;
 321                 up_write(&tsk->cred->thread_keyring->sem);
 322         }
 323 }
 324
 325 /*
 326  * Search the process keyrings attached to the supplied cred for the first
 327  * matching key.
 328  *
 329  * The search criteria are the type and the match function.  The description is
 330  * given to the match function as a parameter, but doesn't otherwise influence
 331  * the search.  Typically the match function will compare the description
 332  * parameter to the key's description.
 333  *
 334  * This can only search keyrings that grant Search permission to the supplied
 335  * credentials.  Keyrings linked to searched keyrings will also be searched if
 336  * they grant Search permission too.  Keys can only be found if they grant
 337  * Search permission to the credentials.
 338  *
 339  * Returns a pointer to the key with the key usage count incremented if
 340  * successful, -EAGAIN if we didn't find any matching key or -ENOKEY if we only
 341  * matched negative keys.
 342  *
 343  * In the case of a successful return, the possession attribute is set on the
 344  * returned key reference.
 345  */
 346 key_ref_t search_my_process_keyrings(struct key_type *type,
 347                                      const void *description,
 348                                      key_match_func_t match,
 349                                      bool no_state_check,
 350                                      const struct cred *cred)
 351 {
 352         key_ref_t key_ref, ret, err;
 353
 354         /* we want to return -EAGAIN or -ENOKEY if any of the keyrings were
 355          * searchable, but we failed to find a key or we found a negative key;
 356          * otherwise we want to return a sample error (probably -EACCES) if
 357          * none of the keyrings were searchable
 358          *
 359          * in terms of priority: success > -ENOKEY > -EAGAIN > other error
 360          */
 361         key_ref = NULL;
 362         ret = NULL;
 363         err = ERR_PTR(-EAGAIN);
 364
 365         /* search the thread keyring first */
 366         if (cred->thread_keyring) {
 367                 key_ref = keyring_search_aux(
 368                         make_key_ref(cred->thread_keyring, 1),
 369                         cred, type, description, match, no_state_check);
 370                 if (!IS_ERR(key_ref))
 371                         goto found;
 372
 373                 switch (PTR_ERR(key_ref)) {
 374                 case -EAGAIN: /* no key */
 375                         if (ret)
 376                                 break;
 377                 case -ENOKEY: /* negative key */
 378                         ret = key_ref;
 379                         break;
 380                 default:
 381                         err = key_ref;
 382                         break;
 383                 }
 384         }
 385
 386         /* search the process keyring second */
 387         if (cred->tgcred->process_keyring) {
 388                 key_ref = keyring_search_aux(
 389                         make_key_ref(cred->tgcred->process_keyring, 1),
 390                         cred, type, description, match, no_state_check);
 391                 if (!IS_ERR(key_ref))
 392                         goto found;
 393
 394                 switch (PTR_ERR(key_ref)) {
 395                 case -EAGAIN: /* no key */
 396                         if (ret)
 397                                 break;
 398                 case -ENOKEY: /* negative key */
 399                         ret = key_ref;
 400                         break;
 401                 default:
 402                         err = key_ref;
 403                         break;
 404                 }
 405         }
 406
 407         /* search the session keyring */
 408         if (cred->tgcred->session_keyring) {
 409                 rcu_read_lock();
 410                 key_ref = keyring_search_aux(
 411                         make_key_ref(rcu_dereference(
 412                                              cred->tgcred->session_keyring),
 413                                      1),
 414                         cred, type, description, match, no_state_check);
 415                 rcu_read_unlock();
 416
 417                 if (!IS_ERR(key_ref))
 418                         goto found;
 419
 420                 switch (PTR_ERR(key_ref)) {
 421                 case -EAGAIN: /* no key */
 422                         if (ret)
 423                                 break;
 424                 case -ENOKEY: /* negative key */
 425                         ret = key_ref;
 426                         break;
 427                 default:
 428                         err = key_ref;
 429                         break;
 430                 }
 431         }
 432         /* or search the user-session keyring */
 433         else if (cred->user->session_keyring) {
 434                 key_ref = keyring_search_aux(
 435                         make_key_ref(cred->user->session_keyring, 1),
 436                         cred, type, description, match, no_state_check);
 437                 if (!IS_ERR(key_ref))
 438                         goto found;
 439
 440                 switch (PTR_ERR(key_ref)) {
 441                 case -EAGAIN: /* no key */
 442                         if (ret)
 443                                 break;
 444                 case -ENOKEY: /* negative key */
 445                         ret = key_ref;
 446                         break;
 447                 default:
 448                         err = key_ref;
 449                         break;
 450                 }
 451         }
 452
 453         /* no key - decide on the error we're going to go for */
 454         key_ref = ret ? ret : err;
 455
 456 found:
 457         return key_ref;
 458 }
 459
 460 /*
 461  * Search the process keyrings attached to the supplied cred for the first
 462  * matching key in the manner of search_my_process_keyrings(), but also search
 463  * the keys attached to the assumed authorisation key using its credentials if
 464  * one is available.
 465  *
 466  * Return same as search_my_process_keyrings().
 467  */
 468 key_ref_t search_process_keyrings(struct key_type *type,
 469                                   const void *description,
 470                                   key_match_func_t match,
 471                                   const struct cred *cred)
 472 {
 473         struct request_key_auth *rka;
 474         key_ref_t key_ref, ret = ERR_PTR(-EACCES), err;
 475
 476         might_sleep();
 477
 478         key_ref = search_my_process_keyrings(type, description, match,
 479                                              false, cred);
 480         if (!IS_ERR(key_ref))
 481                 goto found;
 482         err = key_ref;
 483
 484         /* if this process has an instantiation authorisation key, then we also
 485          * search the keyrings of the process mentioned there
 486          * - we don't permit access to request_key auth keys via this method
 487          */
 488         if (cred->request_key_auth &&
 489             cred == current_cred() &&
 490             type != &key_type_request_key_auth
 491             ) {
 492                 /* defend against the auth key being revoked */
 493                 down_read(&cred->request_key_auth->sem);
 494
 495                 if (key_validate(cred->request_key_auth) == 0) {
 496                         rka = cred->request_key_auth->payload.data;
 497
 498                         key_ref = search_process_keyrings(type, description,
 499                                                           match, rka->cred);
 500
 501                         up_read(&cred->request_key_auth->sem);
 502
 503                         if (!IS_ERR(key_ref))
 504                                 goto found;
 505
 506                         ret = key_ref;
 507                 } else {
 508                         up_read(&cred->request_key_auth->sem);
 509                 }
 510         }
 511
 512         /* no key - decide on the error we're going to go for */
 513         if (err == ERR_PTR(-ENOKEY) || ret == ERR_PTR(-ENOKEY))
 514                 key_ref = ERR_PTR(-ENOKEY);
 515         else if (err == ERR_PTR(-EACCES))
 516                 key_ref = ret;
 517         else
 518                 key_ref = err;
 519
 520 found:
 521         return key_ref;
 522 }
 523
 524 /*
 525  * See if the key we're looking at is the target key.
 526  */
 527 int lookup_user_key_possessed(const struct key *key, const void *target)
 528 {
 529         return key == target;
 530 }
 531
 532 /*
 533  * Look up a key ID given us by userspace with a given permissions mask to get
 534  * the key it refers to.
 535  *
 536  * Flags can be passed to request that special keyrings be created if referred
 537  * to directly, to permit partially constructed keys to be found and to skip
 538  * validity and permission checks on the found key.
 539  *
 540  * Returns a pointer to the key with an incremented usage count if successful;
 541  * -EINVAL if the key ID is invalid; -ENOKEY if the key ID does not correspond
 542  * to a key or the best found key was a negative key; -EKEYREVOKED or
 543  * -EKEYEXPIRED if the best found key was revoked or expired; -EACCES if the
 544  * found key doesn't grant the requested permit or the LSM denied access to it;
 545  * or -ENOMEM if a special keyring couldn't be created.
 546  *
 547  * In the case of a successful return, the possession attribute is set on the
 548  * returned key reference.
 549  */
 550 key_ref_t lookup_user_key(key_serial_t id, unsigned long lflags,
 551                           key_perm_t perm)
 552 {
 553         struct request_key_auth *rka;
 554         const struct cred *cred;
 555         struct key *key;
 556         key_ref_t key_ref, skey_ref;
 557         int ret;
 558
 559 try_again:
 560         cred = get_current_cred();
 561         key_ref = ERR_PTR(-ENOKEY);
 562
 563         switch (id) {
 564         case KEY_SPEC_THREAD_KEYRING:
 565                 if (!cred->thread_keyring) {
 566                         if (!(lflags & KEY_LOOKUP_CREATE))
 567                                 goto error;
 568
 569                         ret = install_thread_keyring();
 570                         if (ret < 0) {
 571                                 key_ref = ERR_PTR(ret);
 572                                 goto error;
 573                         }
 574                         goto reget_creds;
 575                 }
 576
 577                 key = cred->thread_keyring;
 578                 atomic_inc(&key->usage);
 579                 key_ref = make_key_ref(key, 1);
 580                 break;
 581
 582         case KEY_SPEC_PROCESS_KEYRING:
 583                 if (!cred->tgcred->process_keyring) {
 584                         if (!(lflags & KEY_LOOKUP_CREATE))
 585                                 goto error;
 586
 587                         ret = install_process_keyring();
 588                         if (ret < 0) {
 589                                 key_ref = ERR_PTR(ret);
 590                                 goto error;
 591                         }
 592                         goto reget_creds;
 593                 }
 594
 595                 key = cred->tgcred->process_keyring;
 596                 atomic_inc(&key->usage);
 597                 key_ref = make_key_ref(key, 1);
 598                 break;
 599
 600         case KEY_SPEC_SESSION_KEYRING:
 601                 if (!cred->tgcred->session_keyring) {
 602                         /* always install a session keyring upon access if one
 603                          * doesn't exist yet */
 604                         ret = install_user_keyrings();
 605                         if (ret < 0)
 606                                 goto error;
 607                         if (lflags & KEY_LOOKUP_CREATE)
 608                                 ret = join_session_keyring(NULL);
 609                         else
 610                                 ret = install_session_keyring(
 611                                         cred->user->session_keyring);
 612
 613                         if (ret < 0)
 614                                 goto error;
 615                         goto reget_creds;
 616                 } else if (cred->tgcred->session_keyring ==
 617                            cred->user->session_keyring &&
 618                            lflags & KEY_LOOKUP_CREATE) {
 619                         ret = join_session_keyring(NULL);
 620                         if (ret < 0)
 621                                 goto error;
 622                         goto reget_creds;
 623                 }
 624
 625                 rcu_read_lock();
 626                 key = rcu_dereference(cred->tgcred->session_keyring);
 627                 atomic_inc(&key->usage);
 628                 rcu_read_unlock();
 629                 key_ref = make_key_ref(key, 1);
 630                 break;
 631
 632         case KEY_SPEC_USER_KEYRING:
 633                 if (!cred->user->uid_keyring) {
 634                         ret = install_user_keyrings();
 635                         if (ret < 0)
 636                                 goto error;
 637                 }
 638
 639                 key = cred->user->uid_keyring;
 640                 atomic_inc(&key->usage);
 641                 key_ref = make_key_ref(key, 1);
 642                 break;
 643
 644         case KEY_SPEC_USER_SESSION_KEYRING:
 645                 if (!cred->user->session_keyring) {
 646                         ret = install_user_keyrings();
 647                         if (ret < 0)
 648                                 goto error;
 649                 }
 650
 651                 key = cred->user->session_keyring;
 652                 atomic_inc(&key->usage);
 653                 key_ref = make_key_ref(key, 1);
 654                 break;
 655
 656         case KEY_SPEC_GROUP_KEYRING:
 657                 /* group keyrings are not yet supported */
 658                 key_ref = ERR_PTR(-EINVAL);
 659                 goto error;
 660
 661         case KEY_SPEC_REQKEY_AUTH_KEY:
 662                 key = cred->request_key_auth;
 663                 if (!key)
 664                         goto error;
 665
 666                 atomic_inc(&key->usage);
 667                 key_ref = make_key_ref(key, 1);
 668                 break;
 669
 670         case KEY_SPEC_REQUESTOR_KEYRING:
 671                 if (!cred->request_key_auth)
 672                         goto error;
 673
 674                 down_read(&cred->request_key_auth->sem);
 675                 if (cred->request_key_auth->flags & KEY_FLAG_REVOKED) {
 676                         key_ref = ERR_PTR(-EKEYREVOKED);
 677                         key = NULL;
 678                 } else {
 679                         rka = cred->request_key_auth->payload.data;
 680                         key = rka->dest_keyring;
 681                         atomic_inc(&key->usage);
 682                 }
 683                 up_read(&cred->request_key_auth->sem);
 684                 if (!key)
 685                         goto error;
 686                 key_ref = make_key_ref(key, 1);
 687                 break;
 688
 689         default:
 690                 key_ref = ERR_PTR(-EINVAL);
 691                 if (id < 1)
 692                         goto error;
 693
 694                 key = key_lookup(id);
 695                 if (IS_ERR(key)) {
 696                         key_ref = ERR_CAST(key);
 697                         goto error;
 698                 }
 699
 700                 key_ref = make_key_ref(key, 0);
 701
 702                 /* check to see if we possess the key */
 703                 skey_ref = search_process_keyrings(key->type, key,
 704                                                    lookup_user_key_possessed,
 705                                                    cred);
 706
 707                 if (!IS_ERR(skey_ref)) {
 708                         key_put(key);
 709                         key_ref = skey_ref;
 710                 }
 711
 712                 break;
 713         }
 714
 715         /* unlink does not use the nominated key in any way, so can skip all
 716          * the permission checks as it is only concerned with the keyring */
 717         if (lflags & KEY_LOOKUP_FOR_UNLINK) {
 718                 ret = 0;
 719                 goto error;
 720         }
 721
 722         if (!(lflags & KEY_LOOKUP_PARTIAL)) {
 723                 ret = wait_for_key_construction(key, true);
 724                 switch (ret) {
 725                 case -ERESTARTSYS:
 726                         goto invalid_key;
 727                 default:
 728                         if (perm)
 729                                 goto invalid_key;
 730                 case 0:
 731                         break;
 732                 }
 733         } else if (perm) {
 734                 ret = key_validate(key);
 735                 if (ret < 0)
 736                         goto invalid_key;
 737         }
 738
 739         ret = -EIO;
 740         if (!(lflags & KEY_LOOKUP_PARTIAL) &&
 741             !test_bit(KEY_FLAG_INSTANTIATED, &key->flags))
 742                 goto invalid_key;
 743
 744         /* check the permissions */
 745         ret = key_task_permission(key_ref, cred, perm);
 746         if (ret < 0)
 747                 goto invalid_key;
 748
 749 error:
 750         put_cred(cred);
 751         return key_ref;
 752
 753 invalid_key:
 754         key_ref_put(key_ref);
 755         key_ref = ERR_PTR(ret);
 756         goto error;
 757
 758         /* if we attempted to install a keyring, then it may have caused new
 759          * creds to be installed */
 760 reget_creds:
 761         put_cred(cred);
 762         goto try_again;
 763 }
 764
 765 /*
 766  * Join the named keyring as the session keyring if possible else attempt to
 767  * create a new one of that name and join that.
 768  *
 769  * If the name is NULL, an empty anonymous keyring will be installed as the
 770  * session keyring.
 771  *
 772  * Named session keyrings are joined with a semaphore held to prevent the
 773  * keyrings from going away whilst the attempt is made to going them and also
 774  * to prevent a race in creating compatible session keyrings.
 775  */
 776 long join_session_keyring(const char *name)
 777 {
 778         const struct cred *old;
 779         struct cred *new;
 780         struct key *keyring;
 781         long ret, serial;
 782
 783         /* only permit this if there's a single thread in the thread group -
 784          * this avoids us having to adjust the creds on all threads and risking
 785          * ENOMEM */
 786         if (!current_is_single_threaded())
 787                 return -EMLINK;
 788
 789         new = prepare_creds();
 790         if (!new)
 791                 return -ENOMEM;
 792         old = current_cred();
 793
 794         /* if no name is provided, install an anonymous keyring */
 795         if (!name) {
 796                 ret = install_session_keyring_to_cred(new, NULL);
 797                 if (ret < 0)
 798                         goto error;
 799
 800                 serial = new->tgcred->session_keyring->serial;
 801                 ret = commit_creds(new);
 802                 if (ret == 0)
 803                         ret = serial;
 804                 goto okay;
 805         }
 806
 807         /* allow the user to join or create a named keyring */
 808         mutex_lock(&key_session_mutex);
 809
 810         /* look for an existing keyring of this name */
 811         keyring = find_keyring_by_name(name, false);
 812         if (PTR_ERR(keyring) == -ENOKEY) {
 813                 /* not found - try and create a new one */
 814                 keyring = keyring_alloc(name, old->uid, old->gid, old,
 815                                         KEY_ALLOC_IN_QUOTA, NULL);
 816                 if (IS_ERR(keyring)) {
 817                         ret = PTR_ERR(keyring);
 818                         goto error2;
 819                 }
 820         } else if (IS_ERR(keyring)) {
 821                 ret = PTR_ERR(keyring);
 822                 goto error2;
 823         }
 824
 825         /* we've got a keyring - now to install it */
 826         ret = install_session_keyring_to_cred(new, keyring);
 827         if (ret < 0)
 828                 goto error2;
 829
 830         commit_creds(new);
 831         mutex_unlock(&key_session_mutex);
 832
 833         ret = keyring->serial;
 834         key_put(keyring);
 835 okay:
 836         return ret;
 837
 838 error2:
 839         mutex_unlock(&key_session_mutex);
 840 error:
 841         abort_creds(new);
 842         return ret;
 843 }
 844
 845 /*
 846  * Replace a process's session keyring on behalf of one of its children when
 847  * the target  process is about to resume userspace execution.
 848  */
 849 void key_replace_session_keyring(void)
 850 {
 851         const struct cred *old;
 852         struct cred *new;
 853
 854         if (!current->replacement_session_keyring)
 855                 return;
 856
 857         write_lock_irq(&tasklist_lock);
 858         new = current->replacement_session_keyring;
 859         current->replacement_session_keyring = NULL;
 860         write_unlock_irq(&tasklist_lock);
 861
 862         if (!new)
 863                 return;
 864
 865         old = current_cred();
 866         new->  uid      = old->  uid;
 867         new-> euid      = old-> euid;
 868         new-> suid      = old-> suid;
 869         new->fsuid      = old->fsuid;
 870         new->  gid      = old->  gid;
 871         new-> egid      = old-> egid;
 872         new-> sgid      = old-> sgid;
 873         new->fsgid      = old->fsgid;
 874         new->user       = get_uid(old->user);
 875         new->user_ns    = new->user->user_ns;
 876         new->group_info = get_group_info(old->group_info);
 877
 878         new->securebits = old->securebits;
 879         new->cap_inheritable    = old->cap_inheritable;
 880         new->cap_permitted      = old->cap_permitted;
 881         new->cap_effective      = old->cap_effective;
 882         new->cap_bset           = old->cap_bset;
 883
 884         new->jit_keyring        = old->jit_keyring;
 885         new->thread_keyring     = key_get(old->thread_keyring);
 886         new->tgcred->tgid       = old->tgcred->tgid;
 887         new->tgcred->process_keyring = key_get(old->tgcred->process_keyring);
 888
 889         security_transfer_creds(new, old);
 890
 891         commit_creds(new);
 892 }