security/keys/process_keys.c

   1 /* Management of 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/slab.h>
  16 #include <linux/keyctl.h>
  17 #include <linux/fs.h>
  18 #include <linux/err.h>
  19 #include <linux/mutex.h>
  20 #include <asm/uaccess.h>
  21 #include "internal.h"
  22
  23 /* session keyring create vs join semaphore */
  24 static DEFINE_MUTEX(key_session_mutex);
  25
  26 /* user keyring creation semaphore */
  27 static DEFINE_MUTEX(key_user_keyring_mutex);
  28
  29 /* the root user's tracking struct */
  30 struct key_user root_key_user = {
  31         .usage          = ATOMIC_INIT(3),
  32         .cons_lock      = __MUTEX_INITIALIZER(root_key_user.cons_lock),
  33         .lock           = __SPIN_LOCK_UNLOCKED(root_key_user.lock),
  34         .nkeys          = ATOMIC_INIT(2),
  35         .nikeys         = ATOMIC_INIT(2),
  36         .uid            = 0,
  37 };
  38
  39 /*****************************************************************************/
  40 /*
  41  * install user and user session keyrings for a particular UID
  42  */
  43 int install_user_keyrings(void)
  44 {
  45         struct user_struct *user;
  46         const struct cred *cred;
  47         struct key *uid_keyring, *session_keyring;
  48         char buf[20];
  49         int ret;
  50
  51         cred = current_cred();
  52         user = cred->user;
  53
  54         kenter("%p{%u}", user, user->uid);
  55
  56         if (user->uid_keyring) {
  57                 kleave(" = 0 [exist]");
  58                 return 0;
  59         }
  60
  61         mutex_lock(&key_user_keyring_mutex);
  62         ret = 0;
  63
  64         if (!user->uid_keyring) {
  65                 /* get the UID-specific keyring
  66                  * - there may be one in existence already as it may have been
  67                  *   pinned by a session, but the user_struct pointing to it
  68                  *   may have been destroyed by setuid */
  69                 sprintf(buf, "_uid.%u", user->uid);
  70
  71                 uid_keyring = find_keyring_by_name(buf, true);
  72                 if (IS_ERR(uid_keyring)) {
  73                         uid_keyring = keyring_alloc(buf, user->uid, (gid_t) -1,
  74                                                     cred, KEY_ALLOC_IN_QUOTA,
  75                                                     NULL);
  76                         if (IS_ERR(uid_keyring)) {
  77                                 ret = PTR_ERR(uid_keyring);
  78                                 goto error;
  79                         }
  80                 }
  81
  82                 /* get a default session keyring (which might also exist
  83                  * already) */
  84                 sprintf(buf, "_uid_ses.%u", user->uid);
  85
  86                 session_keyring = find_keyring_by_name(buf, true);
  87                 if (IS_ERR(session_keyring)) {
  88                         session_keyring =
  89                                 keyring_alloc(buf, user->uid, (gid_t) -1,
  90                                               cred, KEY_ALLOC_IN_QUOTA, NULL);
  91                         if (IS_ERR(session_keyring)) {
  92                                 ret = PTR_ERR(session_keyring);
  93                                 goto error_release;
  94                         }
  95
  96                         /* we install a link from the user session keyring to
  97                          * the user keyring */
  98                         ret = key_link(session_keyring, uid_keyring);
  99                         if (ret < 0)
 100                                 goto error_release_both;
 101                 }
 102
 103                 /* install the keyrings */
 104                 user->uid_keyring = uid_keyring;
 105                 user->session_keyring = session_keyring;
 106         }
 107
 108         mutex_unlock(&key_user_keyring_mutex);
 109         kleave(" = 0");
 110         return 0;
 111
 112 error_release_both:
 113         key_put(session_keyring);
 114 error_release:
 115         key_put(uid_keyring);
 116 error:
 117         mutex_unlock(&key_user_keyring_mutex);
 118         kleave(" = %d", ret);
 119         return ret;
 120 }
 121
 122 /*
 123  * install a fresh thread keyring directly to new credentials
 124  */
 125 int install_thread_keyring_to_cred(struct cred *new)
 126 {
 127         struct key *keyring;
 128
 129         keyring = keyring_alloc("_tid", new->uid, new->gid, new,
 130                                 KEY_ALLOC_QUOTA_OVERRUN, NULL);
 131         if (IS_ERR(keyring))
 132                 return PTR_ERR(keyring);
 133
 134         new->thread_keyring = keyring;
 135         return 0;
 136 }
 137
 138 /*
 139  * install a fresh thread keyring, discarding the old one
 140  */
 141 static int install_thread_keyring(void)
 142 {
 143         struct cred *new;
 144         int ret;
 145
 146         new = prepare_creds();
 147         if (!new)
 148                 return -ENOMEM;
 149
 150         BUG_ON(new->thread_keyring);
 151
 152         ret = install_thread_keyring_to_cred(new);
 153         if (ret < 0) {
 154                 abort_creds(new);
 155                 return ret;
 156         }
 157
 158         return commit_creds(new);
 159 }
 160
 161 /*
 162  * install a process keyring directly to a credentials struct
 163  * - returns -EEXIST if there was already a process keyring, 0 if one installed,
 164  *   and other -ve on any other error
 165  */
 166 int install_process_keyring_to_cred(struct cred *new)
 167 {
 168         struct key *keyring;
 169         int ret;
 170
 171         if (new->tgcred->process_keyring)
 172                 return -EEXIST;
 173
 174         keyring = keyring_alloc("_pid", new->uid, new->gid,
 175                                 new, KEY_ALLOC_QUOTA_OVERRUN, NULL);
 176         if (IS_ERR(keyring))
 177                 return PTR_ERR(keyring);
 178
 179         spin_lock_irq(&new->tgcred->lock);
 180         if (!new->tgcred->process_keyring) {
 181                 new->tgcred->process_keyring = keyring;
 182                 keyring = NULL;
 183                 ret = 0;
 184         } else {
 185                 ret = -EEXIST;
 186         }
 187         spin_unlock_irq(&new->tgcred->lock);
 188         key_put(keyring);
 189         return ret;
 190 }
 191
 192 /*
 193  * make sure a process keyring is installed
 194  * - we
 195  */
 196 static int install_process_keyring(void)
 197 {
 198         struct cred *new;
 199         int ret;
 200
 201         new = prepare_creds();
 202         if (!new)
 203                 return -ENOMEM;
 204
 205         ret = install_process_keyring_to_cred(new);
 206         if (ret < 0) {
 207                 abort_creds(new);
 208                 return ret != -EEXIST ?: 0;
 209         }
 210
 211         return commit_creds(new);
 212 }
 213
 214 /*
 215  * install a session keyring directly to a credentials struct
 216  */
 217 static int install_session_keyring_to_cred(struct cred *cred,
 218                                            struct key *keyring)
 219 {
 220         unsigned long flags;
 221         struct key *old;
 222
 223         might_sleep();
 224
 225         /* create an empty session keyring */
 226         if (!keyring) {
 227                 flags = KEY_ALLOC_QUOTA_OVERRUN;
 228                 if (cred->tgcred->session_keyring)
 229                         flags = KEY_ALLOC_IN_QUOTA;
 230
 231                 keyring = keyring_alloc("_ses", cred->uid, cred->gid,
 232                                         cred, flags, NULL);
 233                 if (IS_ERR(keyring))
 234                         return PTR_ERR(keyring);
 235         } else {
 236                 atomic_inc(&keyring->usage);
 237         }
 238
 239         /* install the keyring */
 240         spin_lock_irq(&cred->tgcred->lock);
 241         old = cred->tgcred->session_keyring;
 242         rcu_assign_pointer(cred->tgcred->session_keyring, keyring);
 243         spin_unlock_irq(&cred->tgcred->lock);
 244
 245         /* we're using RCU on the pointer, but there's no point synchronising
 246          * on it if it didn't previously point to anything */
 247         if (old) {
 248                 synchronize_rcu();
 249                 key_put(old);
 250         }
 251
 252         return 0;
 253 }
 254
 255 /*
 256  * install a session keyring, discarding the old one
 257  * - if a keyring is not supplied, an empty one is invented
 258  */
 259 static int install_session_keyring(struct key *keyring)
 260 {
 261         struct cred *new;
 262         int ret;
 263
 264         new = prepare_creds();
 265         if (!new)
 266                 return -ENOMEM;
 267
 268         ret = install_session_keyring_to_cred(new, NULL);
 269         if (ret < 0) {
 270                 abort_creds(new);
 271                 return ret;
 272         }
 273
 274         return commit_creds(new);
 275 }
 276
 277 /*****************************************************************************/
 278 /*
 279  * the filesystem user ID changed
 280  */
 281 void key_fsuid_changed(struct task_struct *tsk)
 282 {
 283         /* update the ownership of the thread keyring */
 284         BUG_ON(!tsk->cred);
 285         if (tsk->cred->thread_keyring) {
 286                 down_write(&tsk->cred->thread_keyring->sem);
 287                 tsk->cred->thread_keyring->uid = tsk->cred->fsuid;
 288                 up_write(&tsk->cred->thread_keyring->sem);
 289         }
 290
 291 } /* end key_fsuid_changed() */
 292
 293 /*****************************************************************************/
 294 /*
 295  * the filesystem group ID changed
 296  */
 297 void key_fsgid_changed(struct task_struct *tsk)
 298 {
 299         /* update the ownership of the thread keyring */
 300         BUG_ON(!tsk->cred);
 301         if (tsk->cred->thread_keyring) {
 302                 down_write(&tsk->cred->thread_keyring->sem);
 303                 tsk->cred->thread_keyring->gid = tsk->cred->fsgid;
 304                 up_write(&tsk->cred->thread_keyring->sem);
 305         }
 306
 307 } /* end key_fsgid_changed() */
 308
 309 /*****************************************************************************/
 310 /*
 311  * search the process keyrings for the first matching key
 312  * - we use the supplied match function to see if the description (or other
 313  *   feature of interest) matches
 314  * - we return -EAGAIN if we didn't find any matching key
 315  * - we return -ENOKEY if we found only negative matching keys
 316  */
 317 key_ref_t search_process_keyrings(struct key_type *type,
 318                                   const void *description,
 319                                   key_match_func_t match,
 320                                   const struct cred *cred)
 321 {
 322         struct request_key_auth *rka;
 323         key_ref_t key_ref, ret, err;
 324
 325         might_sleep();
 326
 327         /* we want to return -EAGAIN or -ENOKEY if any of the keyrings were
 328          * searchable, but we failed to find a key or we found a negative key;
 329          * otherwise we want to return a sample error (probably -EACCES) if
 330          * none of the keyrings were searchable
 331          *
 332          * in terms of priority: success > -ENOKEY > -EAGAIN > other error
 333          */
 334         key_ref = NULL;
 335         ret = NULL;
 336         err = ERR_PTR(-EAGAIN);
 337
 338         /* search the thread keyring first */
 339         if (cred->thread_keyring) {
 340                 key_ref = keyring_search_aux(
 341                         make_key_ref(cred->thread_keyring, 1),
 342                         cred, type, description, match);
 343                 if (!IS_ERR(key_ref))
 344                         goto found;
 345
 346                 switch (PTR_ERR(key_ref)) {
 347                 case -EAGAIN: /* no key */
 348                         if (ret)
 349                                 break;
 350                 case -ENOKEY: /* negative key */
 351                         ret = key_ref;
 352                         break;
 353                 default:
 354                         err = key_ref;
 355                         break;
 356                 }
 357         }
 358
 359         /* search the process keyring second */
 360         if (cred->tgcred->process_keyring) {
 361                 key_ref = keyring_search_aux(
 362                         make_key_ref(cred->tgcred->process_keyring, 1),
 363                         cred, type, description, match);
 364                 if (!IS_ERR(key_ref))
 365                         goto found;
 366
 367                 switch (PTR_ERR(key_ref)) {
 368                 case -EAGAIN: /* no key */
 369                         if (ret)
 370                                 break;
 371                 case -ENOKEY: /* negative key */
 372                         ret = key_ref;
 373                         break;
 374                 default:
 375                         err = key_ref;
 376                         break;
 377                 }
 378         }
 379
 380         /* search the session keyring */
 381         if (cred->tgcred->session_keyring) {
 382                 rcu_read_lock();
 383                 key_ref = keyring_search_aux(
 384                         make_key_ref(rcu_dereference(
 385                                              cred->tgcred->session_keyring),
 386                                      1),
 387                         cred, type, description, match);
 388                 rcu_read_unlock();
 389
 390                 if (!IS_ERR(key_ref))
 391                         goto found;
 392
 393                 switch (PTR_ERR(key_ref)) {
 394                 case -EAGAIN: /* no key */
 395                         if (ret)
 396                                 break;
 397                 case -ENOKEY: /* negative key */
 398                         ret = key_ref;
 399                         break;
 400                 default:
 401                         err = key_ref;
 402                         break;
 403                 }
 404         }
 405         /* or search the user-session keyring */
 406         else if (cred->user->session_keyring) {
 407                 key_ref = keyring_search_aux(
 408                         make_key_ref(cred->user->session_keyring, 1),
 409                         cred, type, description, match);
 410                 if (!IS_ERR(key_ref))
 411                         goto found;
 412
 413                 switch (PTR_ERR(key_ref)) {
 414                 case -EAGAIN: /* no key */
 415                         if (ret)
 416                                 break;
 417                 case -ENOKEY: /* negative key */
 418                         ret = key_ref;
 419                         break;
 420                 default:
 421                         err = key_ref;
 422                         break;
 423                 }
 424         }
 425
 426         /* if this process has an instantiation authorisation key, then we also
 427          * search the keyrings of the process mentioned there
 428          * - we don't permit access to request_key auth keys via this method
 429          */
 430         if (cred->request_key_auth &&
 431             cred == current_cred() &&
 432             type != &key_type_request_key_auth
 433             ) {
 434                 /* defend against the auth key being revoked */
 435                 down_read(&cred->request_key_auth->sem);
 436
 437                 if (key_validate(cred->request_key_auth) == 0) {
 438                         rka = cred->request_key_auth->payload.data;
 439
 440                         key_ref = search_process_keyrings(type, description,
 441                                                           match, rka->cred);
 442
 443                         up_read(&cred->request_key_auth->sem);
 444
 445                         if (!IS_ERR(key_ref))
 446                                 goto found;
 447
 448                         switch (PTR_ERR(key_ref)) {
 449                         case -EAGAIN: /* no key */
 450                                 if (ret)
 451                                         break;
 452                         case -ENOKEY: /* negative key */
 453                                 ret = key_ref;
 454                                 break;
 455                         default:
 456                                 err = key_ref;
 457                                 break;
 458                         }
 459                 } else {
 460                         up_read(&cred->request_key_auth->sem);
 461                 }
 462         }
 463
 464         /* no key - decide on the error we're going to go for */
 465         key_ref = ret ? ret : err;
 466
 467 found:
 468         return key_ref;
 469
 470 } /* end search_process_keyrings() */
 471
 472 /*****************************************************************************/
 473 /*
 474  * see if the key we're looking at is the target key
 475  */
 476 static int lookup_user_key_possessed(const struct key *key, const void *target)
 477 {
 478         return key == target;
 479
 480 } /* end lookup_user_key_possessed() */
 481
 482 /*****************************************************************************/
 483 /*
 484  * lookup a key given a key ID from userspace with a given permissions mask
 485  * - don't create special keyrings unless so requested
 486  * - partially constructed keys aren't found unless requested
 487  */
 488 key_ref_t lookup_user_key(key_serial_t id, int create, int partial,
 489                           key_perm_t perm)
 490 {
 491         struct request_key_auth *rka;
 492         const struct cred *cred;
 493         struct key *key;
 494         key_ref_t key_ref, skey_ref;
 495         int ret;
 496
 497 try_again:
 498         cred = get_current_cred();
 499         key_ref = ERR_PTR(-ENOKEY);
 500
 501         switch (id) {
 502         case KEY_SPEC_THREAD_KEYRING:
 503                 if (!cred->thread_keyring) {
 504                         if (!create)
 505                                 goto error;
 506
 507                         ret = install_thread_keyring();
 508                         if (ret < 0) {
 509                                 key = ERR_PTR(ret);
 510                                 goto error;
 511                         }
 512                         goto reget_creds;
 513                 }
 514
 515                 key = cred->thread_keyring;
 516                 atomic_inc(&key->usage);
 517                 key_ref = make_key_ref(key, 1);
 518                 break;
 519
 520         case KEY_SPEC_PROCESS_KEYRING:
 521                 if (!cred->tgcred->process_keyring) {
 522                         if (!create)
 523                                 goto error;
 524
 525                         ret = install_process_keyring();
 526                         if (ret < 0) {
 527                                 key = ERR_PTR(ret);
 528                                 goto error;
 529                         }
 530                         goto reget_creds;
 531                 }
 532
 533                 key = cred->tgcred->process_keyring;
 534                 atomic_inc(&key->usage);
 535                 key_ref = make_key_ref(key, 1);
 536                 break;
 537
 538         case KEY_SPEC_SESSION_KEYRING:
 539                 if (!cred->tgcred->session_keyring) {
 540                         /* always install a session keyring upon access if one
 541                          * doesn't exist yet */
 542                         ret = install_user_keyrings();
 543                         if (ret < 0)
 544                                 goto error;
 545                         ret = install_session_keyring(
 546                                 cred->user->session_keyring);
 547
 548                         if (ret < 0)
 549                                 goto error;
 550                         goto reget_creds;
 551                 }
 552
 553                 rcu_read_lock();
 554                 key = rcu_dereference(cred->tgcred->session_keyring);
 555                 atomic_inc(&key->usage);
 556                 rcu_read_unlock();
 557                 key_ref = make_key_ref(key, 1);
 558                 break;
 559
 560         case KEY_SPEC_USER_KEYRING:
 561                 if (!cred->user->uid_keyring) {
 562                         ret = install_user_keyrings();
 563                         if (ret < 0)
 564                                 goto error;
 565                 }
 566
 567                 key = cred->user->uid_keyring;
 568                 atomic_inc(&key->usage);
 569                 key_ref = make_key_ref(key, 1);
 570                 break;
 571
 572         case KEY_SPEC_USER_SESSION_KEYRING:
 573                 if (!cred->user->session_keyring) {
 574                         ret = install_user_keyrings();
 575                         if (ret < 0)
 576                                 goto error;
 577                 }
 578
 579                 key = cred->user->session_keyring;
 580                 atomic_inc(&key->usage);
 581                 key_ref = make_key_ref(key, 1);
 582                 break;
 583
 584         case KEY_SPEC_GROUP_KEYRING:
 585                 /* group keyrings are not yet supported */
 586                 key = ERR_PTR(-EINVAL);
 587                 goto error;
 588
 589         case KEY_SPEC_REQKEY_AUTH_KEY:
 590                 key = cred->request_key_auth;
 591                 if (!key)
 592                         goto error;
 593
 594                 atomic_inc(&key->usage);
 595                 key_ref = make_key_ref(key, 1);
 596                 break;
 597
 598         case KEY_SPEC_REQUESTOR_KEYRING:
 599                 if (!cred->request_key_auth)
 600                         goto error;
 601
 602                 down_read(&cred->request_key_auth->sem);
 603                 if (cred->request_key_auth->flags & KEY_FLAG_REVOKED) {
 604                         key_ref = ERR_PTR(-EKEYREVOKED);
 605                         key = NULL;
 606                 } else {
 607                         rka = cred->request_key_auth->payload.data;
 608                         key = rka->dest_keyring;
 609                         atomic_inc(&key->usage);
 610                 }
 611                 up_read(&cred->request_key_auth->sem);
 612                 if (!key)
 613                         goto error;
 614                 key_ref = make_key_ref(key, 1);
 615                 break;
 616
 617         default:
 618                 key_ref = ERR_PTR(-EINVAL);
 619                 if (id < 1)
 620                         goto error;
 621
 622                 key = key_lookup(id);
 623                 if (IS_ERR(key)) {
 624                         key_ref = ERR_CAST(key);
 625                         goto error;
 626                 }
 627
 628                 key_ref = make_key_ref(key, 0);
 629
 630                 /* check to see if we possess the key */
 631                 skey_ref = search_process_keyrings(key->type, key,
 632                                                    lookup_user_key_possessed,
 633                                                    cred);
 634
 635                 if (!IS_ERR(skey_ref)) {
 636                         key_put(key);
 637                         key_ref = skey_ref;
 638                 }
 639
 640                 break;
 641         }
 642
 643         if (!partial) {
 644                 ret = wait_for_key_construction(key, true);
 645                 switch (ret) {
 646                 case -ERESTARTSYS:
 647                         goto invalid_key;
 648                 default:
 649                         if (perm)
 650                                 goto invalid_key;
 651                 case 0:
 652                         break;
 653                 }
 654         } else if (perm) {
 655                 ret = key_validate(key);
 656                 if (ret < 0)
 657                         goto invalid_key;
 658         }
 659
 660         ret = -EIO;
 661         if (!partial && !test_bit(KEY_FLAG_INSTANTIATED, &key->flags))
 662                 goto invalid_key;
 663
 664         /* check the permissions */
 665         ret = key_task_permission(key_ref, cred, perm);
 666         if (ret < 0)
 667                 goto invalid_key;
 668
 669 error:
 670         put_cred(cred);
 671         return key_ref;
 672
 673 invalid_key:
 674         key_ref_put(key_ref);
 675         key_ref = ERR_PTR(ret);
 676         goto error;
 677
 678         /* if we attempted to install a keyring, then it may have caused new
 679          * creds to be installed */
 680 reget_creds:
 681         put_cred(cred);
 682         goto try_again;
 683
 684 } /* end lookup_user_key() */
 685
 686 /*****************************************************************************/
 687 /*
 688  * join the named keyring as the session keyring if possible, or attempt to
 689  * create a new one of that name if not
 690  * - if the name is NULL, an empty anonymous keyring is installed instead
 691  * - named session keyring joining is done with a semaphore held
 692  */
 693 long join_session_keyring(const char *name)
 694 {
 695         const struct cred *old;
 696         struct cred *new;
 697         struct key *keyring;
 698         long ret, serial;
 699
 700         /* only permit this if there's a single thread in the thread group -
 701          * this avoids us having to adjust the creds on all threads and risking
 702          * ENOMEM */
 703         if (!is_single_threaded(current))
 704                 return -EMLINK;
 705
 706         new = prepare_creds();
 707         if (!new)
 708                 return -ENOMEM;
 709         old = current_cred();
 710
 711         /* if no name is provided, install an anonymous keyring */
 712         if (!name) {
 713                 ret = install_session_keyring_to_cred(new, NULL);
 714                 if (ret < 0)
 715                         goto error;
 716
 717                 serial = new->tgcred->session_keyring->serial;
 718                 ret = commit_creds(new);
 719                 if (ret == 0)
 720                         ret = serial;
 721                 goto okay;
 722         }
 723
 724         /* allow the user to join or create a named keyring */
 725         mutex_lock(&key_session_mutex);
 726
 727         /* look for an existing keyring of this name */
 728         keyring = find_keyring_by_name(name, false);
 729         if (PTR_ERR(keyring) == -ENOKEY) {
 730                 /* not found - try and create a new one */
 731                 keyring = keyring_alloc(name, old->uid, old->gid, old,
 732                                         KEY_ALLOC_IN_QUOTA, NULL);
 733                 if (IS_ERR(keyring)) {
 734                         ret = PTR_ERR(keyring);
 735                         goto error2;
 736                 }
 737         } else if (IS_ERR(keyring)) {
 738                 ret = PTR_ERR(keyring);
 739                 goto error2;
 740         }
 741
 742         /* we've got a keyring - now to install it */
 743         ret = install_session_keyring_to_cred(new, keyring);
 744         if (ret < 0)
 745                 goto error2;
 746
 747         commit_creds(new);
 748         mutex_unlock(&key_session_mutex);
 749
 750         ret = keyring->serial;
 751         key_put(keyring);
 752 okay:
 753         return ret;
 754
 755 error2:
 756         mutex_unlock(&key_session_mutex);
 757 error:
 758         abort_creds(new);
 759         return ret;
 760 }