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