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         might_sleep();
 395
 396         /* we want to return -EAGAIN or -ENOKEY if any of the keyrings were
 397          * searchable, but we failed to find a key or we found a negative key;
 398          * otherwise we want to return a sample error (probably -EACCES) if
 399          * none of the keyrings were searchable
 400          *
 401          * in terms of priority: success > -ENOKEY > -EAGAIN > other error
 402          */
 403         key_ref = NULL;
 404         ret = NULL;
 405         err = ERR_PTR(-EAGAIN);
 406
 407         /* search the thread keyring first */
 408         if (context->thread_keyring) {
 409                 key_ref = keyring_search_aux(
 410                         make_key_ref(context->thread_keyring, 1),
 411                         context, type, description, match);
 412                 if (!IS_ERR(key_ref))
 413                         goto found;
 414
 415                 switch (PTR_ERR(key_ref)) {
 416                 case -EAGAIN: /* no key */
 417                         if (ret)
 418                                 break;
 419                 case -ENOKEY: /* negative key */
 420                         ret = key_ref;
 421                         break;
 422                 default:
 423                         err = key_ref;
 424                         break;
 425                 }
 426         }
 427
 428         /* search the process keyring second */
 429         if (context->signal->process_keyring) {
 430                 key_ref = keyring_search_aux(
 431                         make_key_ref(context->signal->process_keyring, 1),
 432                         context, type, description, match);
 433                 if (!IS_ERR(key_ref))
 434                         goto found;
 435
 436                 switch (PTR_ERR(key_ref)) {
 437                 case -EAGAIN: /* no key */
 438                         if (ret)
 439                                 break;
 440                 case -ENOKEY: /* negative key */
 441                         ret = key_ref;
 442                         break;
 443                 default:
 444                         err = key_ref;
 445                         break;
 446                 }
 447         }
 448
 449         /* search the session keyring */
 450         if (context->signal->session_keyring) {
 451                 rcu_read_lock();
 452                 key_ref = keyring_search_aux(
 453                         make_key_ref(rcu_dereference(
 454                                              context->signal->session_keyring),
 455                                      1),
 456                         context, type, description, match);
 457                 rcu_read_unlock();
 458
 459                 if (!IS_ERR(key_ref))
 460                         goto found;
 461
 462                 switch (PTR_ERR(key_ref)) {
 463                 case -EAGAIN: /* no key */
 464                         if (ret)
 465                                 break;
 466                 case -ENOKEY: /* negative key */
 467                         ret = key_ref;
 468                         break;
 469                 default:
 470                         err = key_ref;
 471                         break;
 472                 }
 473         }
 474         /* or search the user-session keyring */
 475         else {
 476                 key_ref = keyring_search_aux(
 477                         make_key_ref(context->user->session_keyring, 1),
 478                         context, type, description, match);
 479                 if (!IS_ERR(key_ref))
 480                         goto found;
 481
 482                 switch (PTR_ERR(key_ref)) {
 483                 case -EAGAIN: /* no key */
 484                         if (ret)
 485                                 break;
 486                 case -ENOKEY: /* negative key */
 487                         ret = key_ref;
 488                         break;
 489                 default:
 490                         err = key_ref;
 491                         break;
 492                 }
 493         }
 494
 495         /* if this process has an instantiation authorisation key, then we also
 496          * search the keyrings of the process mentioned there
 497          * - we don't permit access to request_key auth keys via this method
 498          */
 499         if (context->request_key_auth &&
 500             context == current &&
 501             type != &key_type_request_key_auth
 502             ) {
 503                 /* defend against the auth key being revoked */
 504                 down_read(&context->request_key_auth->sem);
 505
 506                 if (key_validate(context->request_key_auth) == 0) {
 507                         rka = context->request_key_auth->payload.data;
 508
 509                         key_ref = search_process_keyrings(type, description,
 510                                                           match, rka->context);
 511
 512                         up_read(&context->request_key_auth->sem);
 513
 514                         if (!IS_ERR(key_ref))
 515                                 goto found;
 516
 517                         switch (PTR_ERR(key_ref)) {
 518                         case -EAGAIN: /* no key */
 519                                 if (ret)
 520                                         break;
 521                         case -ENOKEY: /* negative key */
 522                                 ret = key_ref;
 523                                 break;
 524                         default:
 525                                 err = key_ref;
 526                                 break;
 527                         }
 528                 } else {
 529                         up_read(&context->request_key_auth->sem);
 530                 }
 531         }
 532
 533         /* no key - decide on the error we're going to go for */
 534         key_ref = ret ? ret : err;
 535
 536 found:
 537         return key_ref;
 538
 539 } /* end search_process_keyrings() */
 540
 541 /*****************************************************************************/
 542 /*
 543  * see if the key we're looking at is the target key
 544  */
 545 static int lookup_user_key_possessed(const struct key *key, const void *target)
 546 {
 547         return key == target;
 548
 549 } /* end lookup_user_key_possessed() */
 550
 551 /*****************************************************************************/
 552 /*
 553  * lookup a key given a key ID from userspace with a given permissions mask
 554  * - don't create special keyrings unless so requested
 555  * - partially constructed keys aren't found unless requested
 556  */
 557 key_ref_t lookup_user_key(struct task_struct *context, key_serial_t id,
 558                           int create, int partial, key_perm_t perm)
 559 {
 560         key_ref_t key_ref, skey_ref;
 561         struct key *key;
 562         int ret;
 563
 564         if (!context)
 565                 context = current;
 566
 567         key_ref = ERR_PTR(-ENOKEY);
 568
 569         switch (id) {
 570         case KEY_SPEC_THREAD_KEYRING:
 571                 if (!context->thread_keyring) {
 572                         if (!create)
 573                                 goto error;
 574
 575                         ret = install_thread_keyring(context);
 576                         if (ret < 0) {
 577                                 key = ERR_PTR(ret);
 578                                 goto error;
 579                         }
 580                 }
 581
 582                 key = context->thread_keyring;
 583                 atomic_inc(&key->usage);
 584                 key_ref = make_key_ref(key, 1);
 585                 break;
 586
 587         case KEY_SPEC_PROCESS_KEYRING:
 588                 if (!context->signal->process_keyring) {
 589                         if (!create)
 590                                 goto error;
 591
 592                         ret = install_process_keyring(context);
 593                         if (ret < 0) {
 594                                 key = ERR_PTR(ret);
 595                                 goto error;
 596                         }
 597                 }
 598
 599                 key = context->signal->process_keyring;
 600                 atomic_inc(&key->usage);
 601                 key_ref = make_key_ref(key, 1);
 602                 break;
 603
 604         case KEY_SPEC_SESSION_KEYRING:
 605                 if (!context->signal->session_keyring) {
 606                         /* always install a session keyring upon access if one
 607                          * doesn't exist yet */
 608                         ret = install_session_keyring(
 609                                 context, context->user->session_keyring);
 610                         if (ret < 0)
 611                                 goto error;
 612                 }
 613
 614                 rcu_read_lock();
 615                 key = rcu_dereference(context->signal->session_keyring);
 616                 atomic_inc(&key->usage);
 617                 rcu_read_unlock();
 618                 key_ref = make_key_ref(key, 1);
 619                 break;
 620
 621         case KEY_SPEC_USER_KEYRING:
 622                 key = context->user->uid_keyring;
 623                 atomic_inc(&key->usage);
 624                 key_ref = make_key_ref(key, 1);
 625                 break;
 626
 627         case KEY_SPEC_USER_SESSION_KEYRING:
 628                 key = context->user->session_keyring;
 629                 atomic_inc(&key->usage);
 630                 key_ref = make_key_ref(key, 1);
 631                 break;
 632
 633         case KEY_SPEC_GROUP_KEYRING:
 634                 /* group keyrings are not yet supported */
 635                 key = ERR_PTR(-EINVAL);
 636                 goto error;
 637
 638         case KEY_SPEC_REQKEY_AUTH_KEY:
 639                 key = context->request_key_auth;
 640                 if (!key)
 641                         goto error;
 642
 643                 atomic_inc(&key->usage);
 644                 key_ref = make_key_ref(key, 1);
 645                 break;
 646
 647         default:
 648                 key_ref = ERR_PTR(-EINVAL);
 649                 if (id < 1)
 650                         goto error;
 651
 652                 key = key_lookup(id);
 653                 if (IS_ERR(key)) {
 654                         key_ref = ERR_PTR(PTR_ERR(key));
 655                         goto error;
 656                 }
 657
 658                 key_ref = make_key_ref(key, 0);
 659
 660                 /* check to see if we possess the key */
 661                 skey_ref = search_process_keyrings(key->type, key,
 662                                                    lookup_user_key_possessed,
 663                                                    current);
 664
 665                 if (!IS_ERR(skey_ref)) {
 666                         key_put(key);
 667                         key_ref = skey_ref;
 668                 }
 669
 670                 break;
 671         }
 672
 673         /* check the status */
 674         if (perm) {
 675                 ret = key_validate(key);
 676                 if (ret < 0)
 677                         goto invalid_key;
 678         }
 679
 680         ret = -EIO;
 681         if (!partial && !test_bit(KEY_FLAG_INSTANTIATED, &key->flags))
 682                 goto invalid_key;
 683
 684         /* check the permissions */
 685         ret = key_task_permission(key_ref, context, perm);
 686         if (ret < 0)
 687                 goto invalid_key;
 688
 689 error:
 690         return key_ref;
 691
 692 invalid_key:
 693         key_ref_put(key_ref);
 694         key_ref = ERR_PTR(ret);
 695         goto error;
 696
 697 } /* end lookup_user_key() */
 698
 699 /*****************************************************************************/
 700 /*
 701  * join the named keyring as the session keyring if possible, or attempt to
 702  * create a new one of that name if not
 703  * - if the name is NULL, an empty anonymous keyring is installed instead
 704  * - named session keyring joining is done with a semaphore held
 705  */
 706 long join_session_keyring(const char *name)
 707 {
 708         struct task_struct *tsk = current;
 709         struct key *keyring;
 710         long ret;
 711
 712         /* if no name is provided, install an anonymous keyring */
 713         if (!name) {
 714                 ret = install_session_keyring(tsk, NULL);
 715                 if (ret < 0)
 716                         goto error;
 717
 718                 rcu_read_lock();
 719                 ret = rcu_dereference(tsk->signal->session_keyring)->serial;
 720                 rcu_read_unlock();
 721                 goto error;
 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, 0);
 729         if (PTR_ERR(keyring) == -ENOKEY) {
 730                 /* not found - try and create a new one */
 731                 keyring = keyring_alloc(name, tsk->uid, tsk->gid, tsk, 0, NULL);
 732                 if (IS_ERR(keyring)) {
 733                         ret = PTR_ERR(keyring);
 734                         goto error2;
 735                 }
 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(tsk, keyring);
 744         if (ret < 0)
 745                 goto error2;
 746
 747         ret = keyring->serial;
 748         key_put(keyring);
 749
 750 error2:
 751         mutex_unlock(&key_session_mutex);
 752 error:
 753         return ret;
 754
 755 } /* end join_session_keyring() */