security/keys/process_keys.c

   1 /* process_keys.c: management of a process's keyrings
   2  *
   3  * Copyright (C) 2004-5 Red Hat, Inc. All Rights Reserved.
   4  * Written by David Howells (dhowells@redhat.com)
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public License
   8  * as published by the Free Software Foundation; either version
   9  * 2 of the License, or (at your option) any later version.
  10  */
  11
  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 <asm/uaccess.h>
  20 #include "internal.h"
  21
  22 /* session keyring create vs join semaphore */
  23 static DECLARE_MUTEX(key_session_sem);
  24
  25 /* the root user's tracking struct */
  26 struct key_user root_key_user = {
  27         .usage          = ATOMIC_INIT(3),
  28         .consq          = LIST_HEAD_INIT(root_key_user.consq),
  29         .lock           = SPIN_LOCK_UNLOCKED,
  30         .nkeys          = ATOMIC_INIT(2),
  31         .nikeys         = ATOMIC_INIT(2),
  32         .uid            = 0,
  33 };
  34
  35 /* the root user's UID keyring */
  36 struct key root_user_keyring = {
  37         .usage          = ATOMIC_INIT(1),
  38         .serial         = 2,
  39         .type           = &key_type_keyring,
  40         .user           = &root_key_user,
  41         .sem            = __RWSEM_INITIALIZER(root_user_keyring.sem),
  42         .perm           = KEY_POS_ALL | KEY_USR_ALL,
  43         .flags          = 1 << KEY_FLAG_INSTANTIATED,
  44         .description    = "_uid.0",
  45 #ifdef KEY_DEBUGGING
  46         .magic          = KEY_DEBUG_MAGIC,
  47 #endif
  48 };
  49
  50 /* the root user's default session keyring */
  51 struct key root_session_keyring = {
  52         .usage          = ATOMIC_INIT(1),
  53         .serial         = 1,
  54         .type           = &key_type_keyring,
  55         .user           = &root_key_user,
  56         .sem            = __RWSEM_INITIALIZER(root_session_keyring.sem),
  57         .perm           = KEY_POS_ALL | KEY_USR_ALL,
  58         .flags          = 1 << KEY_FLAG_INSTANTIATED,
  59         .description    = "_uid_ses.0",
  60 #ifdef KEY_DEBUGGING
  61         .magic          = KEY_DEBUG_MAGIC,
  62 #endif
  63 };
  64
  65 /*****************************************************************************/
  66 /*
  67  * allocate the keyrings to be associated with a UID
  68  */
  69 int alloc_uid_keyring(struct user_struct *user)
  70 {
  71         struct key *uid_keyring, *session_keyring;
  72         char buf[20];
  73         int ret;
  74
  75         /* concoct a default session keyring */
  76         sprintf(buf, "_uid_ses.%u", user->uid);
  77
  78         session_keyring = keyring_alloc(buf, user->uid, (gid_t) -1, 0, NULL);
  79         if (IS_ERR(session_keyring)) {
  80                 ret = PTR_ERR(session_keyring);
  81                 goto error;
  82         }
  83
  84         /* and a UID specific keyring, pointed to by the default session
  85          * keyring */
  86         sprintf(buf, "_uid.%u", user->uid);
  87
  88         uid_keyring = keyring_alloc(buf, user->uid, (gid_t) -1, 0,
  89                                     session_keyring);
  90         if (IS_ERR(uid_keyring)) {
  91                 key_put(session_keyring);
  92                 ret = PTR_ERR(uid_keyring);
  93                 goto error;
  94         }
  95
  96         /* install the keyrings */
  97         user->uid_keyring = uid_keyring;
  98         user->session_keyring = session_keyring;
  99         ret = 0;
 100
 101 error:
 102         return ret;
 103
 104 } /* end alloc_uid_keyring() */
 105
 106 /*****************************************************************************/
 107 /*
 108  * deal with the UID changing
 109  */
 110 void switch_uid_keyring(struct user_struct *new_user)
 111 {
 112 #if 0 /* do nothing for now */
 113         struct key *old;
 114
 115         /* switch to the new user's session keyring if we were running under
 116          * root's default session keyring */
 117         if (new_user->uid != 0 &&
 118             current->session_keyring == &root_session_keyring
 119             ) {
 120                 atomic_inc(&new_user->session_keyring->usage);
 121
 122                 task_lock(current);
 123                 old = current->session_keyring;
 124                 current->session_keyring = new_user->session_keyring;
 125                 task_unlock(current);
 126
 127                 key_put(old);
 128         }
 129 #endif
 130
 131 } /* end switch_uid_keyring() */
 132
 133 /*****************************************************************************/
 134 /*
 135  * install a fresh thread keyring, discarding the old one
 136  */
 137 int install_thread_keyring(struct task_struct *tsk)
 138 {
 139         struct key *keyring, *old;
 140         char buf[20];
 141         int ret;
 142
 143         sprintf(buf, "_tid.%u", tsk->pid);
 144
 145         keyring = keyring_alloc(buf, tsk->uid, tsk->gid, 1, NULL);
 146         if (IS_ERR(keyring)) {
 147                 ret = PTR_ERR(keyring);
 148                 goto error;
 149         }
 150
 151         task_lock(tsk);
 152         old = tsk->thread_keyring;
 153         tsk->thread_keyring = keyring;
 154         task_unlock(tsk);
 155
 156         ret = 0;
 157
 158         key_put(old);
 159 error:
 160         return ret;
 161
 162 } /* end install_thread_keyring() */
 163
 164 /*****************************************************************************/
 165 /*
 166  * make sure a process keyring is installed
 167  */
 168 int install_process_keyring(struct task_struct *tsk)
 169 {
 170         unsigned long flags;
 171         struct key *keyring;
 172         char buf[20];
 173         int ret;
 174
 175         if (!tsk->signal->process_keyring) {
 176                 sprintf(buf, "_pid.%u", tsk->tgid);
 177
 178                 keyring = keyring_alloc(buf, tsk->uid, tsk->gid, 1, NULL);
 179                 if (IS_ERR(keyring)) {
 180                         ret = PTR_ERR(keyring);
 181                         goto error;
 182                 }
 183
 184                 /* attach keyring */
 185                 spin_lock_irqsave(&tsk->sighand->siglock, flags);
 186                 if (!tsk->signal->process_keyring) {
 187                         tsk->signal->process_keyring = keyring;
 188                         keyring = NULL;
 189                 }
 190                 spin_unlock_irqrestore(&tsk->sighand->siglock, flags);
 191
 192                 key_put(keyring);
 193         }
 194
 195         ret = 0;
 196 error:
 197         return ret;
 198
 199 } /* end install_process_keyring() */
 200
 201 /*****************************************************************************/
 202 /*
 203  * install a session keyring, discarding the old one
 204  * - if a keyring is not supplied, an empty one is invented
 205  */
 206 static int install_session_keyring(struct task_struct *tsk,
 207                                    struct key *keyring)
 208 {
 209         unsigned long flags;
 210         struct key *old;
 211         char buf[20];
 212         int ret;
 213
 214         /* create an empty session keyring */
 215         if (!keyring) {
 216                 sprintf(buf, "_ses.%u", tsk->tgid);
 217
 218                 keyring = keyring_alloc(buf, tsk->uid, tsk->gid, 1, NULL);
 219                 if (IS_ERR(keyring)) {
 220                         ret = PTR_ERR(keyring);
 221                         goto error;
 222                 }
 223         }
 224         else {
 225                 atomic_inc(&keyring->usage);
 226         }
 227
 228         /* install the keyring */
 229         spin_lock_irqsave(&tsk->sighand->siglock, flags);
 230         old = rcu_dereference(tsk->signal->session_keyring);
 231         rcu_assign_pointer(tsk->signal->session_keyring, keyring);
 232         spin_unlock_irqrestore(&tsk->sighand->siglock, flags);
 233
 234         ret = 0;
 235
 236         /* we're using RCU on the pointer */
 237         synchronize_rcu();
 238         key_put(old);
 239 error:
 240         return ret;
 241
 242 } /* end install_session_keyring() */
 243
 244 /*****************************************************************************/
 245 /*
 246  * copy the keys in a thread group for fork without CLONE_THREAD
 247  */
 248 int copy_thread_group_keys(struct task_struct *tsk)
 249 {
 250         key_check(current->thread_group->session_keyring);
 251         key_check(current->thread_group->process_keyring);
 252
 253         /* no process keyring yet */
 254         tsk->signal->process_keyring = NULL;
 255
 256         /* same session keyring */
 257         rcu_read_lock();
 258         tsk->signal->session_keyring =
 259                 key_get(rcu_dereference(current->signal->session_keyring));
 260         rcu_read_unlock();
 261
 262         return 0;
 263
 264 } /* end copy_thread_group_keys() */
 265
 266 /*****************************************************************************/
 267 /*
 268  * copy the keys for fork
 269  */
 270 int copy_keys(unsigned long clone_flags, struct task_struct *tsk)
 271 {
 272         key_check(tsk->thread_keyring);
 273
 274         /* no thread keyring yet */
 275         tsk->thread_keyring = NULL;
 276         return 0;
 277
 278 } /* end copy_keys() */
 279
 280 /*****************************************************************************/
 281 /*
 282  * dispose of thread group keys upon thread group destruction
 283  */
 284 void exit_thread_group_keys(struct signal_struct *tg)
 285 {
 286         key_put(tg->session_keyring);
 287         key_put(tg->process_keyring);
 288
 289 } /* end exit_thread_group_keys() */
 290
 291 /*****************************************************************************/
 292 /*
 293  * dispose of keys upon thread exit
 294  */
 295 void exit_keys(struct task_struct *tsk)
 296 {
 297         key_put(tsk->thread_keyring);
 298
 299 } /* end exit_keys() */
 300
 301 /*****************************************************************************/
 302 /*
 303  * deal with execve()
 304  */
 305 int exec_keys(struct task_struct *tsk)
 306 {
 307         unsigned long flags;
 308         struct key *old;
 309
 310         /* newly exec'd tasks don't get a thread keyring */
 311         task_lock(tsk);
 312         old = tsk->thread_keyring;
 313         tsk->thread_keyring = NULL;
 314         task_unlock(tsk);
 315
 316         key_put(old);
 317
 318         /* discard the process keyring from a newly exec'd task */
 319         spin_lock_irqsave(&tsk->sighand->siglock, flags);
 320         old = tsk->signal->process_keyring;
 321         tsk->signal->process_keyring = NULL;
 322         spin_unlock_irqrestore(&tsk->sighand->siglock, flags);
 323
 324         key_put(old);
 325
 326         return 0;
 327
 328 } /* end exec_keys() */
 329
 330 /*****************************************************************************/
 331 /*
 332  * deal with SUID programs
 333  * - we might want to make this invent a new session keyring
 334  */
 335 int suid_keys(struct task_struct *tsk)
 336 {
 337         return 0;
 338
 339 } /* end suid_keys() */
 340
 341 /*****************************************************************************/
 342 /*
 343  * the filesystem user ID changed
 344  */
 345 void key_fsuid_changed(struct task_struct *tsk)
 346 {
 347         /* update the ownership of the thread keyring */
 348         if (tsk->thread_keyring) {
 349                 down_write(&tsk->thread_keyring->sem);
 350                 tsk->thread_keyring->uid = tsk->fsuid;
 351                 up_write(&tsk->thread_keyring->sem);
 352         }
 353
 354 } /* end key_fsuid_changed() */
 355
 356 /*****************************************************************************/
 357 /*
 358  * the filesystem group ID changed
 359  */
 360 void key_fsgid_changed(struct task_struct *tsk)
 361 {
 362         /* update the ownership of the thread keyring */
 363         if (tsk->thread_keyring) {
 364                 down_write(&tsk->thread_keyring->sem);
 365                 tsk->thread_keyring->gid = tsk->fsgid;
 366                 up_write(&tsk->thread_keyring->sem);
 367         }
 368
 369 } /* end key_fsgid_changed() */
 370
 371 /*****************************************************************************/
 372 /*
 373  * search the process keyrings for the first matching key
 374  * - we use the supplied match function to see if the description (or other
 375  *   feature of interest) matches
 376  * - we return -EAGAIN if we didn't find any matching key
 377  * - we return -ENOKEY if we found only negative matching keys
 378  */
 379 key_ref_t search_process_keyrings(struct key_type *type,
 380                                   const void *description,
 381                                   key_match_func_t match,
 382                                   struct task_struct *context)
 383 {
 384         struct request_key_auth *rka;
 385         key_ref_t key_ref, ret, err, instkey_ref;
 386
 387         /* we want to return -EAGAIN or -ENOKEY if any of the keyrings were
 388          * searchable, but we failed to find a key or we found a negative key;
 389          * otherwise we want to return a sample error (probably -EACCES) if
 390          * none of the keyrings were searchable
 391          *
 392          * in terms of priority: success > -ENOKEY > -EAGAIN > other error
 393          */
 394         key_ref = NULL;
 395         ret = NULL;
 396         err = ERR_PTR(-EAGAIN);
 397
 398         /* search the thread keyring first */
 399         if (context->thread_keyring) {
 400                 key_ref = keyring_search_aux(
 401                         make_key_ref(context->thread_keyring, 1),
 402                         context, type, description, match);
 403                 if (!IS_ERR(key_ref))
 404                         goto found;
 405
 406                 switch (PTR_ERR(key_ref)) {
 407                 case -EAGAIN: /* no key */
 408                         if (ret)
 409                                 break;
 410                 case -ENOKEY: /* negative key */
 411                         ret = key_ref;
 412                         break;
 413                 default:
 414                         err = key_ref;
 415                         break;
 416                 }
 417         }
 418
 419         /* search the process keyring second */
 420         if (context->signal->process_keyring) {
 421                 key_ref = keyring_search_aux(
 422                         make_key_ref(context->signal->process_keyring, 1),
 423                         context, type, description, match);
 424                 if (!IS_ERR(key_ref))
 425                         goto found;
 426
 427                 switch (PTR_ERR(key_ref)) {
 428                 case -EAGAIN: /* no key */
 429                         if (ret)
 430                                 break;
 431                 case -ENOKEY: /* negative key */
 432                         ret = key_ref;
 433                         break;
 434                 default:
 435                         err = key_ref;
 436                         break;
 437                 }
 438         }
 439
 440         /* search the session keyring */
 441         if (context->signal->session_keyring) {
 442                 rcu_read_lock();
 443                 key_ref = keyring_search_aux(
 444                         make_key_ref(rcu_dereference(
 445                                              context->signal->session_keyring),
 446                                      1),
 447                         context, type, description, match);
 448                 rcu_read_unlock();
 449
 450                 if (!IS_ERR(key_ref))
 451                         goto found;
 452
 453                 switch (PTR_ERR(key_ref)) {
 454                 case -EAGAIN: /* no key */
 455                         if (ret)
 456                                 break;
 457                 case -ENOKEY: /* negative key */
 458                         ret = key_ref;
 459                         break;
 460                 default:
 461                         err = key_ref;
 462                         break;
 463                 }
 464
 465                 /* if this process has a session keyring and that has an
 466                  * instantiation authorisation key in the bottom level, then we
 467                  * also search the keyrings of the process mentioned there */
 468                 if (context != current)
 469                         goto no_key;
 470
 471                 rcu_read_lock();
 472                 instkey_ref = __keyring_search_one(
 473                         make_key_ref(rcu_dereference(
 474                                              context->signal->session_keyring),
 475                                      1),
 476                         &key_type_request_key_auth, NULL, 0);
 477                 rcu_read_unlock();
 478
 479                 if (IS_ERR(instkey_ref))
 480                         goto no_key;
 481
 482                 rka = key_ref_to_ptr(instkey_ref)->payload.data;
 483
 484                 key_ref = search_process_keyrings(type, description, match,
 485                                                   rka->context);
 486                 key_ref_put(instkey_ref);
 487
 488                 if (!IS_ERR(key_ref))
 489                         goto found;
 490
 491                 switch (PTR_ERR(key_ref)) {
 492                 case -EAGAIN: /* no key */
 493                         if (ret)
 494                                 break;
 495                 case -ENOKEY: /* negative key */
 496                         ret = key_ref;
 497                         break;
 498                 default:
 499                         err = key_ref;
 500                         break;
 501                 }
 502         }
 503         /* or search the user-session keyring */
 504         else {
 505                 key_ref = keyring_search_aux(
 506                         make_key_ref(context->user->session_keyring, 1),
 507                         context, type, description, match);
 508                 if (!IS_ERR(key_ref))
 509                         goto found;
 510
 511                 switch (PTR_ERR(key_ref)) {
 512                 case -EAGAIN: /* no key */
 513                         if (ret)
 514                                 break;
 515                 case -ENOKEY: /* negative key */
 516                         ret = key_ref;
 517                         break;
 518                 default:
 519                         err = key_ref;
 520                         break;
 521                 }
 522         }
 523
 524
 525 no_key:
 526         /* no key - decide on the error we're going to go for */
 527         key_ref = ret ? ret : err;
 528
 529 found:
 530         return key_ref;
 531
 532 } /* end search_process_keyrings() */
 533
 534 /*****************************************************************************/
 535 /*
 536  * see if the key we're looking at is the target key
 537  */
 538 static int lookup_user_key_possessed(const struct key *key, const void *target)
 539 {
 540         return key == target;
 541
 542 } /* end lookup_user_key_possessed() */
 543
 544 /*****************************************************************************/
 545 /*
 546  * lookup a key given a key ID from userspace with a given permissions mask
 547  * - don't create special keyrings unless so requested
 548  * - partially constructed keys aren't found unless requested
 549  */
 550 key_ref_t lookup_user_key(struct task_struct *context, key_serial_t id,
 551                           int create, int partial, key_perm_t perm)
 552 {
 553         key_ref_t key_ref, skey_ref;
 554         struct key *key;
 555         int ret;
 556
 557         if (!context)
 558                 context = current;
 559
 560         key_ref = ERR_PTR(-ENOKEY);
 561
 562         switch (id) {
 563         case KEY_SPEC_THREAD_KEYRING:
 564                 if (!context->thread_keyring) {
 565                         if (!create)
 566                                 goto error;
 567
 568                         ret = install_thread_keyring(context);
 569                         if (ret < 0) {
 570                                 key = ERR_PTR(ret);
 571                                 goto error;
 572                         }
 573                 }
 574
 575                 key = context->thread_keyring;
 576                 atomic_inc(&key->usage);
 577                 key_ref = make_key_ref(key, 1);
 578                 break;
 579
 580         case KEY_SPEC_PROCESS_KEYRING:
 581                 if (!context->signal->process_keyring) {
 582                         if (!create)
 583                                 goto error;
 584
 585                         ret = install_process_keyring(context);
 586                         if (ret < 0) {
 587                                 key = ERR_PTR(ret);
 588                                 goto error;
 589                         }
 590                 }
 591
 592                 key = context->signal->process_keyring;
 593                 atomic_inc(&key->usage);
 594                 key_ref = make_key_ref(key, 1);
 595                 break;
 596
 597         case KEY_SPEC_SESSION_KEYRING:
 598                 if (!context->signal->session_keyring) {
 599                         /* always install a session keyring upon access if one
 600                          * doesn't exist yet */
 601                         ret = install_session_keyring(
 602                                 context, context->user->session_keyring);
 603                         if (ret < 0)
 604                                 goto error;
 605                 }
 606
 607                 rcu_read_lock();
 608                 key = rcu_dereference(context->signal->session_keyring);
 609                 atomic_inc(&key->usage);
 610                 rcu_read_unlock();
 611                 key_ref = make_key_ref(key, 1);
 612                 break;
 613
 614         case KEY_SPEC_USER_KEYRING:
 615                 key = context->user->uid_keyring;
 616                 atomic_inc(&key->usage);
 617                 key_ref = make_key_ref(key, 1);
 618                 break;
 619
 620         case KEY_SPEC_USER_SESSION_KEYRING:
 621                 key = context->user->session_keyring;
 622                 atomic_inc(&key->usage);
 623                 key_ref = make_key_ref(key, 1);
 624                 break;
 625
 626         case KEY_SPEC_GROUP_KEYRING:
 627                 /* group keyrings are not yet supported */
 628                 key = ERR_PTR(-EINVAL);
 629                 goto error;
 630
 631         default:
 632                 key_ref = ERR_PTR(-EINVAL);
 633                 if (id < 1)
 634                         goto error;
 635
 636                 key = key_lookup(id);
 637                 if (IS_ERR(key)) {
 638                         key_ref = ERR_PTR(PTR_ERR(key));
 639                         goto error;
 640                 }
 641
 642                 key_ref = make_key_ref(key, 0);
 643
 644                 /* check to see if we possess the key */
 645                 skey_ref = search_process_keyrings(key->type, key,
 646                                                    lookup_user_key_possessed,
 647                                                    current);
 648
 649                 if (!IS_ERR(skey_ref)) {
 650                         key_put(key);
 651                         key_ref = skey_ref;
 652                 }
 653
 654                 break;
 655         }
 656
 657         /* check the status */
 658         if (perm) {
 659                 ret = key_validate(key);
 660                 if (ret < 0)
 661                         goto invalid_key;
 662         }
 663
 664         ret = -EIO;
 665         if (!partial && !test_bit(KEY_FLAG_INSTANTIATED, &key->flags))
 666                 goto invalid_key;
 667
 668         /* check the permissions */
 669         ret = -EACCES;
 670
 671         if (!key_task_permission(key_ref, context, perm))
 672                 goto invalid_key;
 673
 674 error:
 675         return key_ref;
 676
 677 invalid_key:
 678         key_ref_put(key_ref);
 679         key_ref = ERR_PTR(ret);
 680         goto error;
 681
 682 } /* end lookup_user_key() */
 683
 684 /*****************************************************************************/
 685 /*
 686  * join the named keyring as the session keyring if possible, or attempt to
 687  * create a new one of that name if not
 688  * - if the name is NULL, an empty anonymous keyring is installed instead
 689  * - named session keyring joining is done with a semaphore held
 690  */
 691 long join_session_keyring(const char *name)
 692 {
 693         struct task_struct *tsk = current;
 694         struct key *keyring;
 695         long ret;
 696
 697         /* if no name is provided, install an anonymous keyring */
 698         if (!name) {
 699                 ret = install_session_keyring(tsk, NULL);
 700                 if (ret < 0)
 701                         goto error;
 702
 703                 rcu_read_lock();
 704                 ret = rcu_dereference(tsk->signal->session_keyring)->serial;
 705                 rcu_read_unlock();
 706                 goto error;
 707         }
 708
 709         /* allow the user to join or create a named keyring */
 710         down(&key_session_sem);
 711
 712         /* look for an existing keyring of this name */
 713         keyring = find_keyring_by_name(name, 0);
 714         if (PTR_ERR(keyring) == -ENOKEY) {
 715                 /* not found - try and create a new one */
 716                 keyring = keyring_alloc(name, tsk->uid, tsk->gid, 0, NULL);
 717                 if (IS_ERR(keyring)) {
 718                         ret = PTR_ERR(keyring);
 719                         goto error2;
 720                 }
 721         }
 722         else if (IS_ERR(keyring)) {
 723                 ret = PTR_ERR(keyring);
 724                 goto error2;
 725         }
 726
 727         /* we've got a keyring - now to install it */
 728         ret = install_session_keyring(tsk, keyring);
 729         if (ret < 0)
 730                 goto error2;
 731
 732         ret = keyring->serial;
 733         key_put(keyring);
 734
 735 error2:
 736         up(&key_session_sem);
 737 error:
 738         return ret;
 739
 740 } /* end join_session_keyring() */