security/keys/process_keys.c

   1 /* process_keys.c: management of a process's keyrings
   2  *
   3  * Copyright (C) 2004 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         .lock           = RW_LOCK_UNLOCKED,
  42         .sem            = __RWSEM_INITIALIZER(root_user_keyring.sem),
  43         .perm           = KEY_USR_ALL,
  44         .flags          = 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         .lock           = RW_LOCK_UNLOCKED,
  58         .sem            = __RWSEM_INITIALIZER(root_session_keyring.sem),
  59         .perm           = KEY_USR_ALL,
  60         .flags          = KEY_FLAG_INSTANTIATED,
  61         .description    = "_uid_ses.0",
  62 #ifdef KEY_DEBUGGING
  63         .magic          = KEY_DEBUG_MAGIC,
  64 #endif
  65 };
  66
  67 /*****************************************************************************/
  68 /*
  69  * allocate the keyrings to be associated with a UID
  70  */
  71 int alloc_uid_keyring(struct user_struct *user)
  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, 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, 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, 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  * install a fresh process keyring, discarding the old one
 169  */
 170 static int install_process_keyring(struct task_struct *tsk)
 171 {
 172         struct key *keyring, *old;
 173         char buf[20];
 174         int ret;
 175
 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         task_lock(tsk);
 185         old = tsk->process_keyring;
 186         tsk->process_keyring = keyring;
 187         task_unlock(tsk);
 188
 189         ret = 0;
 190
 191         key_put(old);
 192  error:
 193         return ret;
 194
 195 } /* end install_process_keyring() */
 196
 197 /*****************************************************************************/
 198 /*
 199  * install a session keyring, discarding the old one
 200  * - if a keyring is not supplied, an empty one is invented
 201  */
 202 static int install_session_keyring(struct task_struct *tsk,
 203                                    struct key *keyring)
 204 {
 205         struct key *old;
 206         char buf[20];
 207         int ret;
 208
 209         /* create an empty session keyring */
 210         if (!keyring) {
 211                 sprintf(buf, "_ses.%u", tsk->tgid);
 212
 213                 keyring = keyring_alloc(buf, tsk->uid, tsk->gid, 1, NULL);
 214                 if (IS_ERR(keyring)) {
 215                         ret = PTR_ERR(keyring);
 216                         goto error;
 217                 }
 218         }
 219         else {
 220                 atomic_inc(&keyring->usage);
 221         }
 222
 223         /* install the keyring */
 224         task_lock(tsk);
 225         old = tsk->session_keyring;
 226         tsk->session_keyring = keyring;
 227         task_unlock(tsk);
 228
 229         ret = 0;
 230
 231         key_put(old);
 232  error:
 233         return ret;
 234
 235 } /* end install_session_keyring() */
 236
 237 /*****************************************************************************/
 238 /*
 239  * copy the keys for fork
 240  */
 241 int copy_keys(unsigned long clone_flags, struct task_struct *tsk)
 242 {
 243         int ret = 0;
 244
 245         key_check(tsk->session_keyring);
 246         key_check(tsk->process_keyring);
 247         key_check(tsk->thread_keyring);
 248
 249         if (tsk->session_keyring)
 250                 atomic_inc(&tsk->session_keyring->usage);
 251
 252         if (tsk->process_keyring) {
 253                 if (clone_flags & CLONE_THREAD) {
 254                         atomic_inc(&tsk->process_keyring->usage);
 255                 }
 256                 else {
 257                         tsk->process_keyring = NULL;
 258                         ret = install_process_keyring(tsk);
 259                 }
 260         }
 261
 262         tsk->thread_keyring = NULL;
 263         return ret;
 264
 265 } /* end copy_keys() */
 266
 267 /*****************************************************************************/
 268 /*
 269  * dispose of keys upon exit
 270  */
 271 void exit_keys(struct task_struct *tsk)
 272 {
 273         key_put(tsk->session_keyring);
 274         key_put(tsk->process_keyring);
 275         key_put(tsk->thread_keyring);
 276
 277 } /* end exit_keys() */
 278
 279 /*****************************************************************************/
 280 /*
 281  * deal with execve()
 282  */
 283 int exec_keys(struct task_struct *tsk)
 284 {
 285         struct key *old;
 286
 287         /* newly exec'd tasks don't get a thread keyring */
 288         task_lock(tsk);
 289         old = tsk->thread_keyring;
 290         tsk->thread_keyring = NULL;
 291         task_unlock(tsk);
 292
 293         key_put(old);
 294
 295         /* newly exec'd tasks get a fresh process keyring */
 296         return install_process_keyring(tsk);
 297
 298 } /* end exec_keys() */
 299
 300 /*****************************************************************************/
 301 /*
 302  * deal with SUID programs
 303  * - we might want to make this invent a new session keyring
 304  */
 305 int suid_keys(struct task_struct *tsk)
 306 {
 307         return 0;
 308
 309 } /* end suid_keys() */
 310
 311 /*****************************************************************************/
 312 /*
 313  * the filesystem user ID changed
 314  */
 315 void key_fsuid_changed(struct task_struct *tsk)
 316 {
 317         /* update the ownership of the process keyring */
 318         if (tsk->process_keyring) {
 319                 down_write(&tsk->process_keyring->sem);
 320                 write_lock(&tsk->process_keyring->lock);
 321                 tsk->process_keyring->uid = tsk->fsuid;
 322                 write_unlock(&tsk->process_keyring->lock);
 323                 up_write(&tsk->process_keyring->sem);
 324         }
 325
 326         /* update the ownership of the thread keyring */
 327         if (tsk->thread_keyring) {
 328                 down_write(&tsk->thread_keyring->sem);
 329                 write_lock(&tsk->thread_keyring->lock);
 330                 tsk->thread_keyring->uid = tsk->fsuid;
 331                 write_unlock(&tsk->thread_keyring->lock);
 332                 up_write(&tsk->thread_keyring->sem);
 333         }
 334
 335 } /* end key_fsuid_changed() */
 336
 337 /*****************************************************************************/
 338 /*
 339  * the filesystem group ID changed
 340  */
 341 void key_fsgid_changed(struct task_struct *tsk)
 342 {
 343         /* update the ownership of the process keyring */
 344         if (tsk->process_keyring) {
 345                 down_write(&tsk->process_keyring->sem);
 346                 write_lock(&tsk->process_keyring->lock);
 347                 tsk->process_keyring->gid = tsk->fsgid;
 348                 write_unlock(&tsk->process_keyring->lock);
 349                 up_write(&tsk->process_keyring->sem);
 350         }
 351
 352         /* update the ownership of the thread keyring */
 353         if (tsk->thread_keyring) {
 354                 down_write(&tsk->thread_keyring->sem);
 355                 write_lock(&tsk->thread_keyring->lock);
 356                 tsk->thread_keyring->gid = tsk->fsgid;
 357                 write_unlock(&tsk->thread_keyring->lock);
 358                 up_write(&tsk->thread_keyring->sem);
 359         }
 360
 361 } /* end key_fsgid_changed() */
 362
 363 /*****************************************************************************/
 364 /*
 365  * search the process keyrings for the first matching key
 366  * - we use the supplied match function to see if the description (or other
 367  *   feature of interest) matches
 368  * - we return -EAGAIN if we didn't find any matching key
 369  * - we return -ENOKEY if we found only negative matching keys
 370  */
 371 struct key *search_process_keyrings_aux(struct key_type *type,
 372                                         const void *description,
 373                                         key_match_func_t match)
 374 {
 375         struct task_struct *tsk = current;
 376         struct key *key, *ret, *err, *session;
 377
 378         /* we want to return -EAGAIN or -ENOKEY if any of the keyrings were
 379          * searchable, but we failed to find a key or we found a negative key;
 380          * otherwise we want to return a sample error (probably -EACCES) if
 381          * none of the keyrings were searchable
 382          *
 383          * in terms of priority: success > -ENOKEY > -EAGAIN > other error
 384          */
 385         key = NULL;
 386         ret = NULL;
 387         err = ERR_PTR(-EAGAIN);
 388
 389         /* search the thread keyring first */
 390         if (tsk->thread_keyring) {
 391                 key = keyring_search_aux(tsk->thread_keyring, type,
 392                                          description, match);
 393                 if (!IS_ERR(key))
 394                         goto found;
 395
 396                 switch (PTR_ERR(key)) {
 397                 case -EAGAIN: /* no key */
 398                         if (ret)
 399                                 break;
 400                 case -ENOKEY: /* negative key */
 401                         ret = key;
 402                         break;
 403                 default:
 404                         err = key;
 405                         break;
 406                 }
 407         }
 408
 409         /* search the process keyring second */
 410         if (tsk->process_keyring) {
 411                 key = keyring_search_aux(tsk->process_keyring, type,
 412                                          description, match);
 413                 if (!IS_ERR(key))
 414                         goto found;
 415
 416                 switch (PTR_ERR(key)) {
 417                 case -EAGAIN: /* no key */
 418                         if (ret)
 419                                 break;
 420                 case -ENOKEY: /* negative key */
 421                         ret = key;
 422                         break;
 423                 default:
 424                         err = key;
 425                         break;
 426                 }
 427         }
 428
 429         /* search the session keyring last */
 430         session = tsk->session_keyring;
 431         if (!session)
 432                 session = tsk->user->session_keyring;
 433
 434         key = keyring_search_aux(session, type,
 435                                  description, match);
 436         if (!IS_ERR(key))
 437                 goto found;
 438
 439         switch (PTR_ERR(key)) {
 440         case -EAGAIN: /* no key */
 441                 if (ret)
 442                         break;
 443         case -ENOKEY: /* negative key */
 444                 ret = key;
 445                 break;
 446         default:
 447                 err = key;
 448                 break;
 449         }
 450
 451         /* no key - decide on the error we're going to go for */
 452         key = ret ? ret : err;
 453
 454  found:
 455         return key;
 456
 457 } /* end search_process_keyrings_aux() */
 458
 459 /*****************************************************************************/
 460 /*
 461  * search the process keyrings for the first matching key
 462  * - we return -EAGAIN if we didn't find any matching key
 463  * - we return -ENOKEY if we found only negative matching keys
 464  */
 465 struct key *search_process_keyrings(struct key_type *type,
 466                                     const char *description)
 467 {
 468         return search_process_keyrings_aux(type, description, type->match);
 469
 470 } /* end search_process_keyrings() */
 471
 472 /*****************************************************************************/
 473 /*
 474  * lookup a key given a key ID from userspace with a given permissions mask
 475  * - don't create special keyrings unless so requested
 476  * - partially constructed keys aren't found unless requested
 477  */
 478 struct key *lookup_user_key(key_serial_t id, int create, int partial,
 479                             key_perm_t perm)
 480 {
 481         struct task_struct *tsk = current;
 482         struct key *key;
 483         int ret;
 484
 485         key = ERR_PTR(-ENOKEY);
 486
 487         switch (id) {
 488         case KEY_SPEC_THREAD_KEYRING:
 489                 if (!tsk->thread_keyring) {
 490                         if (!create)
 491                                 goto error;
 492
 493                         ret = install_thread_keyring(tsk);
 494                         if (ret < 0) {
 495                                 key = ERR_PTR(ret);
 496                                 goto error;
 497                         }
 498                 }
 499
 500                 key = tsk->thread_keyring;
 501                 atomic_inc(&key->usage);
 502                 break;
 503
 504         case KEY_SPEC_PROCESS_KEYRING:
 505                 if (!tsk->process_keyring) {
 506                         if (!create)
 507                                 goto error;
 508
 509                         ret = install_process_keyring(tsk);
 510                         if (ret < 0) {
 511                                 key = ERR_PTR(ret);
 512                                 goto error;
 513                         }
 514                 }
 515
 516                 key = tsk->process_keyring;
 517                 atomic_inc(&key->usage);
 518                 break;
 519
 520         case KEY_SPEC_SESSION_KEYRING:
 521                 if (!tsk->session_keyring) {
 522                         /* always install a session keyring upon access if one
 523                          * doesn't exist yet */
 524                         ret = install_session_keyring(
 525                                tsk, tsk->user->session_keyring);
 526                         if (ret < 0)
 527                                 goto error;
 528                 }
 529
 530                 key = tsk->session_keyring;
 531                 atomic_inc(&key->usage);
 532                 break;
 533
 534         case KEY_SPEC_USER_KEYRING:
 535                 key = tsk->user->uid_keyring;
 536                 atomic_inc(&key->usage);
 537                 break;
 538
 539         case KEY_SPEC_USER_SESSION_KEYRING:
 540                 key = tsk->user->session_keyring;
 541                 atomic_inc(&key->usage);
 542                 break;
 543
 544         case KEY_SPEC_GROUP_KEYRING:
 545                 /* group keyrings are not yet supported */
 546                 key = ERR_PTR(-EINVAL);
 547                 goto error;
 548
 549         default:
 550                 key = ERR_PTR(-EINVAL);
 551                 if (id < 1)
 552                         goto error;
 553
 554                 key = key_lookup(id);
 555                 if (IS_ERR(key))
 556                         goto error;
 557                 break;
 558         }
 559
 560         /* check the status and permissions */
 561         if (perm) {
 562                 ret = key_validate(key);
 563                 if (ret < 0)
 564                         goto invalid_key;
 565         }
 566
 567         ret = -EIO;
 568         if (!partial && !(key->flags & KEY_FLAG_INSTANTIATED))
 569                 goto invalid_key;
 570
 571         ret = -EACCES;
 572         if (!key_permission(key, perm))
 573                 goto invalid_key;
 574
 575  error:
 576         return key;
 577
 578  invalid_key:
 579         key_put(key);
 580         key = ERR_PTR(ret);
 581         goto error;
 582
 583 } /* end lookup_user_key() */
 584
 585 /*****************************************************************************/
 586 /*
 587  * join the named keyring as the session keyring if possible, or attempt to
 588  * create a new one of that name if not
 589  * - if the name is NULL, an empty anonymous keyring is installed instead
 590  * - named session keyring joining is done with a semaphore held
 591  */
 592 long join_session_keyring(const char *name)
 593 {
 594         struct task_struct *tsk = current;
 595         struct key *keyring;
 596         long ret;
 597
 598         /* if no name is provided, install an anonymous keyring */
 599         if (!name) {
 600                 ret = install_session_keyring(tsk, NULL);
 601                 if (ret < 0)
 602                         goto error;
 603
 604                 ret = tsk->session_keyring->serial;
 605                 goto error;
 606         }
 607
 608         /* allow the user to join or create a named keyring */
 609         down(&key_session_sem);
 610
 611         /* look for an existing keyring of this name */
 612         keyring = find_keyring_by_name(name, 0);
 613         if (PTR_ERR(keyring) == -ENOKEY) {
 614                 /* not found - try and create a new one */
 615                 keyring = keyring_alloc(name, tsk->uid, tsk->gid, 0, NULL);
 616                 if (IS_ERR(keyring)) {
 617                         ret = PTR_ERR(keyring);
 618                         goto error;
 619                 }
 620         }
 621         else if (IS_ERR(keyring)) {
 622                 ret = PTR_ERR(keyring);
 623                 goto error2;
 624         }
 625
 626         /* we've got a keyring - now to install it */
 627         ret = install_session_keyring(tsk, keyring);
 628         if (ret < 0)
 629                 goto error2;
 630
 631         key_put(keyring);
 632
 633         ret = tsk->session_keyring->serial;
 634
 635  error2:
 636         up(&key_session_sem);
 637  error:
 638         return ret;
 639
 640 } /* end join_session_keyring() */