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