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