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