linux/kernel/cred.c
<<
>>
Prefs
   1/* Task credentials management - see Documentation/security/credentials.txt
   2 *
   3 * Copyright (C) 2008 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 Licence
   8 * as published by the Free Software Foundation; either version
   9 * 2 of the Licence, or (at your option) any later version.
  10 */
  11#include <linux/export.h>
  12#include <linux/cred.h>
  13#include <linux/slab.h>
  14#include <linux/sched.h>
  15#include <linux/key.h>
  16#include <linux/keyctl.h>
  17#include <linux/init_task.h>
  18#include <linux/security.h>
  19#include <linux/cn_proc.h>
  20
  21#if 0
  22#define kdebug(FMT, ...) \
  23        printk("[%-5.5s%5u] "FMT"\n", current->comm, current->pid ,##__VA_ARGS__)
  24#else
  25#define kdebug(FMT, ...) \
  26        no_printk("[%-5.5s%5u] "FMT"\n", current->comm, current->pid ,##__VA_ARGS__)
  27#endif
  28
  29static struct kmem_cache *cred_jar;
  30
  31/*
  32 * The common credentials for the initial task's thread group
  33 */
  34#ifdef CONFIG_KEYS
  35static struct thread_group_cred init_tgcred = {
  36        .usage  = ATOMIC_INIT(2),
  37        .tgid   = 0,
  38        .lock   = __SPIN_LOCK_UNLOCKED(init_cred.tgcred.lock),
  39};
  40#endif
  41
  42/*
  43 * The initial credentials for the initial task
  44 */
  45struct cred init_cred = {
  46        .usage                  = ATOMIC_INIT(4),
  47#ifdef CONFIG_DEBUG_CREDENTIALS
  48        .subscribers            = ATOMIC_INIT(2),
  49        .magic                  = CRED_MAGIC,
  50#endif
  51        .securebits             = SECUREBITS_DEFAULT,
  52        .cap_inheritable        = CAP_EMPTY_SET,
  53        .cap_permitted          = CAP_FULL_SET,
  54        .cap_effective          = CAP_FULL_SET,
  55        .cap_bset               = CAP_FULL_SET,
  56        .user                   = INIT_USER,
  57        .user_ns                = &init_user_ns,
  58        .group_info             = &init_groups,
  59#ifdef CONFIG_KEYS
  60        .tgcred                 = &init_tgcred,
  61#endif
  62};
  63
  64static inline void set_cred_subscribers(struct cred *cred, int n)
  65{
  66#ifdef CONFIG_DEBUG_CREDENTIALS
  67        atomic_set(&cred->subscribers, n);
  68#endif
  69}
  70
  71static inline int read_cred_subscribers(const struct cred *cred)
  72{
  73#ifdef CONFIG_DEBUG_CREDENTIALS
  74        return atomic_read(&cred->subscribers);
  75#else
  76        return 0;
  77#endif
  78}
  79
  80static inline void alter_cred_subscribers(const struct cred *_cred, int n)
  81{
  82#ifdef CONFIG_DEBUG_CREDENTIALS
  83        struct cred *cred = (struct cred *) _cred;
  84
  85        atomic_add(n, &cred->subscribers);
  86#endif
  87}
  88
  89/*
  90 * Dispose of the shared task group credentials
  91 */
  92#ifdef CONFIG_KEYS
  93static void release_tgcred_rcu(struct rcu_head *rcu)
  94{
  95        struct thread_group_cred *tgcred =
  96                container_of(rcu, struct thread_group_cred, rcu);
  97
  98        BUG_ON(atomic_read(&tgcred->usage) != 0);
  99
 100        key_put(tgcred->session_keyring);
 101        key_put(tgcred->process_keyring);
 102        kfree(tgcred);
 103}
 104#endif
 105
 106/*
 107 * Release a set of thread group credentials.
 108 */
 109static void release_tgcred(struct cred *cred)
 110{
 111#ifdef CONFIG_KEYS
 112        struct thread_group_cred *tgcred = cred->tgcred;
 113
 114        if (atomic_dec_and_test(&tgcred->usage))
 115                call_rcu(&tgcred->rcu, release_tgcred_rcu);
 116#endif
 117}
 118
 119/*
 120 * The RCU callback to actually dispose of a set of credentials
 121 */
 122static void put_cred_rcu(struct rcu_head *rcu)
 123{
 124        struct cred *cred = container_of(rcu, struct cred, rcu);
 125
 126        kdebug("put_cred_rcu(%p)", cred);
 127
 128#ifdef CONFIG_DEBUG_CREDENTIALS
 129        if (cred->magic != CRED_MAGIC_DEAD ||
 130            atomic_read(&cred->usage) != 0 ||
 131            read_cred_subscribers(cred) != 0)
 132                panic("CRED: put_cred_rcu() sees %p with"
 133                      " mag %x, put %p, usage %d, subscr %d\n",
 134                      cred, cred->magic, cred->put_addr,
 135                      atomic_read(&cred->usage),
 136                      read_cred_subscribers(cred));
 137#else
 138        if (atomic_read(&cred->usage) != 0)
 139                panic("CRED: put_cred_rcu() sees %p with usage %d\n",
 140                      cred, atomic_read(&cred->usage));
 141#endif
 142
 143        security_cred_free(cred);
 144        key_put(cred->thread_keyring);
 145        key_put(cred->request_key_auth);
 146        release_tgcred(cred);
 147        if (cred->group_info)
 148                put_group_info(cred->group_info);
 149        free_uid(cred->user);
 150        kmem_cache_free(cred_jar, cred);
 151}
 152
 153/**
 154 * __put_cred - Destroy a set of credentials
 155 * @cred: The record to release
 156 *
 157 * Destroy a set of credentials on which no references remain.
 158 */
 159void __put_cred(struct cred *cred)
 160{
 161        kdebug("__put_cred(%p{%d,%d})", cred,
 162               atomic_read(&cred->usage),
 163               read_cred_subscribers(cred));
 164
 165        BUG_ON(atomic_read(&cred->usage) != 0);
 166#ifdef CONFIG_DEBUG_CREDENTIALS
 167        BUG_ON(read_cred_subscribers(cred) != 0);
 168        cred->magic = CRED_MAGIC_DEAD;
 169        cred->put_addr = __builtin_return_address(0);
 170#endif
 171        BUG_ON(cred == current->cred);
 172        BUG_ON(cred == current->real_cred);
 173
 174        call_rcu(&cred->rcu, put_cred_rcu);
 175}
 176EXPORT_SYMBOL(__put_cred);
 177
 178/*
 179 * Clean up a task's credentials when it exits
 180 */
 181void exit_creds(struct task_struct *tsk)
 182{
 183        struct cred *cred;
 184
 185        kdebug("exit_creds(%u,%p,%p,{%d,%d})", tsk->pid, tsk->real_cred, tsk->cred,
 186               atomic_read(&tsk->cred->usage),
 187               read_cred_subscribers(tsk->cred));
 188
 189        cred = (struct cred *) tsk->real_cred;
 190        tsk->real_cred = NULL;
 191        validate_creds(cred);
 192        alter_cred_subscribers(cred, -1);
 193        put_cred(cred);
 194
 195        cred = (struct cred *) tsk->cred;
 196        tsk->cred = NULL;
 197        validate_creds(cred);
 198        alter_cred_subscribers(cred, -1);
 199        put_cred(cred);
 200
 201        cred = (struct cred *) tsk->replacement_session_keyring;
 202        if (cred) {
 203                tsk->replacement_session_keyring = NULL;
 204                validate_creds(cred);
 205                put_cred(cred);
 206        }
 207}
 208
 209/**
 210 * get_task_cred - Get another task's objective credentials
 211 * @task: The task to query
 212 *
 213 * Get the objective credentials of a task, pinning them so that they can't go
 214 * away.  Accessing a task's credentials directly is not permitted.
 215 *
 216 * The caller must also make sure task doesn't get deleted, either by holding a
 217 * ref on task or by holding tasklist_lock to prevent it from being unlinked.
 218 */
 219const struct cred *get_task_cred(struct task_struct *task)
 220{
 221        const struct cred *cred;
 222
 223        rcu_read_lock();
 224
 225        do {
 226                cred = __task_cred((task));
 227                BUG_ON(!cred);
 228        } while (!atomic_inc_not_zero(&((struct cred *)cred)->usage));
 229
 230        rcu_read_unlock();
 231        return cred;
 232}
 233
 234/*
 235 * Allocate blank credentials, such that the credentials can be filled in at a
 236 * later date without risk of ENOMEM.
 237 */
 238struct cred *cred_alloc_blank(void)
 239{
 240        struct cred *new;
 241
 242        new = kmem_cache_zalloc(cred_jar, GFP_KERNEL);
 243        if (!new)
 244                return NULL;
 245
 246#ifdef CONFIG_KEYS
 247        new->tgcred = kzalloc(sizeof(*new->tgcred), GFP_KERNEL);
 248        if (!new->tgcred) {
 249                kmem_cache_free(cred_jar, new);
 250                return NULL;
 251        }
 252        atomic_set(&new->tgcred->usage, 1);
 253#endif
 254
 255        atomic_set(&new->usage, 1);
 256#ifdef CONFIG_DEBUG_CREDENTIALS
 257        new->magic = CRED_MAGIC;
 258#endif
 259
 260        if (security_cred_alloc_blank(new, GFP_KERNEL) < 0)
 261                goto error;
 262
 263        return new;
 264
 265error:
 266        abort_creds(new);
 267        return NULL;
 268}
 269
 270/**
 271 * prepare_creds - Prepare a new set of credentials for modification
 272 *
 273 * Prepare a new set of task credentials for modification.  A task's creds
 274 * shouldn't generally be modified directly, therefore this function is used to
 275 * prepare a new copy, which the caller then modifies and then commits by
 276 * calling commit_creds().
 277 *
 278 * Preparation involves making a copy of the objective creds for modification.
 279 *
 280 * Returns a pointer to the new creds-to-be if successful, NULL otherwise.
 281 *
 282 * Call commit_creds() or abort_creds() to clean up.
 283 */
 284struct cred *prepare_creds(void)
 285{
 286        struct task_struct *task = current;
 287        const struct cred *old;
 288        struct cred *new;
 289
 290        validate_process_creds();
 291
 292        new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
 293        if (!new)
 294                return NULL;
 295
 296        kdebug("prepare_creds() alloc %p", new);
 297
 298        old = task->cred;
 299        memcpy(new, old, sizeof(struct cred));
 300
 301        atomic_set(&new->usage, 1);
 302        set_cred_subscribers(new, 0);
 303        get_group_info(new->group_info);
 304        get_uid(new->user);
 305
 306#ifdef CONFIG_KEYS
 307        key_get(new->thread_keyring);
 308        key_get(new->request_key_auth);
 309        atomic_inc(&new->tgcred->usage);
 310#endif
 311
 312#ifdef CONFIG_SECURITY
 313        new->security = NULL;
 314#endif
 315
 316        if (security_prepare_creds(new, old, GFP_KERNEL) < 0)
 317                goto error;
 318        validate_creds(new);
 319        return new;
 320
 321error:
 322        abort_creds(new);
 323        return NULL;
 324}
 325EXPORT_SYMBOL(prepare_creds);
 326
 327/*
 328 * Prepare credentials for current to perform an execve()
 329 * - The caller must hold ->cred_guard_mutex
 330 */
 331struct cred *prepare_exec_creds(void)
 332{
 333        struct thread_group_cred *tgcred = NULL;
 334        struct cred *new;
 335
 336#ifdef CONFIG_KEYS
 337        tgcred = kmalloc(sizeof(*tgcred), GFP_KERNEL);
 338        if (!tgcred)
 339                return NULL;
 340#endif
 341
 342        new = prepare_creds();
 343        if (!new) {
 344                kfree(tgcred);
 345                return new;
 346        }
 347
 348#ifdef CONFIG_KEYS
 349        /* newly exec'd tasks don't get a thread keyring */
 350        key_put(new->thread_keyring);
 351        new->thread_keyring = NULL;
 352
 353        /* create a new per-thread-group creds for all this set of threads to
 354         * share */
 355        memcpy(tgcred, new->tgcred, sizeof(struct thread_group_cred));
 356
 357        atomic_set(&tgcred->usage, 1);
 358        spin_lock_init(&tgcred->lock);
 359
 360        /* inherit the session keyring; new process keyring */
 361        key_get(tgcred->session_keyring);
 362        tgcred->process_keyring = NULL;
 363
 364        release_tgcred(new);
 365        new->tgcred = tgcred;
 366#endif
 367
 368        return new;
 369}
 370
 371/*
 372 * Copy credentials for the new process created by fork()
 373 *
 374 * We share if we can, but under some circumstances we have to generate a new
 375 * set.
 376 *
 377 * The new process gets the current process's subjective credentials as its
 378 * objective and subjective credentials
 379 */
 380int copy_creds(struct task_struct *p, unsigned long clone_flags)
 381{
 382#ifdef CONFIG_KEYS
 383        struct thread_group_cred *tgcred;
 384#endif
 385        struct cred *new;
 386        int ret;
 387
 388        p->replacement_session_keyring = NULL;
 389
 390        if (
 391#ifdef CONFIG_KEYS
 392                !p->cred->thread_keyring &&
 393#endif
 394                clone_flags & CLONE_THREAD
 395            ) {
 396                p->real_cred = get_cred(p->cred);
 397                get_cred(p->cred);
 398                alter_cred_subscribers(p->cred, 2);
 399                kdebug("share_creds(%p{%d,%d})",
 400                       p->cred, atomic_read(&p->cred->usage),
 401                       read_cred_subscribers(p->cred));
 402                atomic_inc(&p->cred->user->processes);
 403                return 0;
 404        }
 405
 406        new = prepare_creds();
 407        if (!new)
 408                return -ENOMEM;
 409
 410        if (clone_flags & CLONE_NEWUSER) {
 411                ret = create_user_ns(new);
 412                if (ret < 0)
 413                        goto error_put;
 414        }
 415
 416        /* cache user_ns in cred.  Doesn't need a refcount because it will
 417         * stay pinned by cred->user
 418         */
 419        new->user_ns = new->user->user_ns;
 420
 421#ifdef CONFIG_KEYS
 422        /* new threads get their own thread keyrings if their parent already
 423         * had one */
 424        if (new->thread_keyring) {
 425                key_put(new->thread_keyring);
 426                new->thread_keyring = NULL;
 427                if (clone_flags & CLONE_THREAD)
 428                        install_thread_keyring_to_cred(new);
 429        }
 430
 431        /* we share the process and session keyrings between all the threads in
 432         * a process - this is slightly icky as we violate COW credentials a
 433         * bit */
 434        if (!(clone_flags & CLONE_THREAD)) {
 435                tgcred = kmalloc(sizeof(*tgcred), GFP_KERNEL);
 436                if (!tgcred) {
 437                        ret = -ENOMEM;
 438                        goto error_put;
 439                }
 440                atomic_set(&tgcred->usage, 1);
 441                spin_lock_init(&tgcred->lock);
 442                tgcred->process_keyring = NULL;
 443                tgcred->session_keyring = key_get(new->tgcred->session_keyring);
 444
 445                release_tgcred(new);
 446                new->tgcred = tgcred;
 447        }
 448#endif
 449
 450        atomic_inc(&new->user->processes);
 451        p->cred = p->real_cred = get_cred(new);
 452        alter_cred_subscribers(new, 2);
 453        validate_creds(new);
 454        return 0;
 455
 456error_put:
 457        put_cred(new);
 458        return ret;
 459}
 460
 461/**
 462 * commit_creds - Install new credentials upon the current task
 463 * @new: The credentials to be assigned
 464 *
 465 * Install a new set of credentials to the current task, using RCU to replace
 466 * the old set.  Both the objective and the subjective credentials pointers are
 467 * updated.  This function may not be called if the subjective credentials are
 468 * in an overridden state.
 469 *
 470 * This function eats the caller's reference to the new credentials.
 471 *
 472 * Always returns 0 thus allowing this function to be tail-called at the end
 473 * of, say, sys_setgid().
 474 */
 475int commit_creds(struct cred *new)
 476{
 477        struct task_struct *task = current;
 478        const struct cred *old = task->real_cred;
 479
 480        kdebug("commit_creds(%p{%d,%d})", new,
 481               atomic_read(&new->usage),
 482               read_cred_subscribers(new));
 483
 484        BUG_ON(task->cred != old);
 485#ifdef CONFIG_DEBUG_CREDENTIALS
 486        BUG_ON(read_cred_subscribers(old) < 2);
 487        validate_creds(old);
 488        validate_creds(new);
 489#endif
 490        BUG_ON(atomic_read(&new->usage) < 1);
 491
 492        get_cred(new); /* we will require a ref for the subj creds too */
 493
 494        /* dumpability changes */
 495        if (old->euid != new->euid ||
 496            old->egid != new->egid ||
 497            old->fsuid != new->fsuid ||
 498            old->fsgid != new->fsgid ||
 499            !cap_issubset(new->cap_permitted, old->cap_permitted)) {
 500                if (task->mm)
 501                        set_dumpable(task->mm, suid_dumpable);
 502                task->pdeath_signal = 0;
 503                smp_wmb();
 504        }
 505
 506        /* alter the thread keyring */
 507        if (new->fsuid != old->fsuid)
 508                key_fsuid_changed(task);
 509        if (new->fsgid != old->fsgid)
 510                key_fsgid_changed(task);
 511
 512        /* do it
 513         * RLIMIT_NPROC limits on user->processes have already been checked
 514         * in set_user().
 515         */
 516        alter_cred_subscribers(new, 2);
 517        if (new->user != old->user)
 518                atomic_inc(&new->user->processes);
 519        rcu_assign_pointer(task->real_cred, new);
 520        rcu_assign_pointer(task->cred, new);
 521        if (new->user != old->user)
 522                atomic_dec(&old->user->processes);
 523        alter_cred_subscribers(old, -2);
 524
 525        /* send notifications */
 526        if (new->uid   != old->uid  ||
 527            new->euid  != old->euid ||
 528            new->suid  != old->suid ||
 529            new->fsuid != old->fsuid)
 530                proc_id_connector(task, PROC_EVENT_UID);
 531
 532        if (new->gid   != old->gid  ||
 533            new->egid  != old->egid ||
 534            new->sgid  != old->sgid ||
 535            new->fsgid != old->fsgid)
 536                proc_id_connector(task, PROC_EVENT_GID);
 537
 538        /* release the old obj and subj refs both */
 539        put_cred(old);
 540        put_cred(old);
 541        return 0;
 542}
 543EXPORT_SYMBOL(commit_creds);
 544
 545/**
 546 * abort_creds - Discard a set of credentials and unlock the current task
 547 * @new: The credentials that were going to be applied
 548 *
 549 * Discard a set of credentials that were under construction and unlock the
 550 * current task.
 551 */
 552void abort_creds(struct cred *new)
 553{
 554        kdebug("abort_creds(%p{%d,%d})", new,
 555               atomic_read(&new->usage),
 556               read_cred_subscribers(new));
 557
 558#ifdef CONFIG_DEBUG_CREDENTIALS
 559        BUG_ON(read_cred_subscribers(new) != 0);
 560#endif
 561        BUG_ON(atomic_read(&new->usage) < 1);
 562        put_cred(new);
 563}
 564EXPORT_SYMBOL(abort_creds);
 565
 566/**
 567 * override_creds - Override the current process's subjective credentials
 568 * @new: The credentials to be assigned
 569 *
 570 * Install a set of temporary override subjective credentials on the current
 571 * process, returning the old set for later reversion.
 572 */
 573const struct cred *override_creds(const struct cred *new)
 574{
 575        const struct cred *old = current->cred;
 576
 577        kdebug("override_creds(%p{%d,%d})", new,
 578               atomic_read(&new->usage),
 579               read_cred_subscribers(new));
 580
 581        validate_creds(old);
 582        validate_creds(new);
 583        get_cred(new);
 584        alter_cred_subscribers(new, 1);
 585        rcu_assign_pointer(current->cred, new);
 586        alter_cred_subscribers(old, -1);
 587
 588        kdebug("override_creds() = %p{%d,%d}", old,
 589               atomic_read(&old->usage),
 590               read_cred_subscribers(old));
 591        return old;
 592}
 593EXPORT_SYMBOL(override_creds);
 594
 595/**
 596 * revert_creds - Revert a temporary subjective credentials override
 597 * @old: The credentials to be restored
 598 *
 599 * Revert a temporary set of override subjective credentials to an old set,
 600 * discarding the override set.
 601 */
 602void revert_creds(const struct cred *old)
 603{
 604        const struct cred *override = current->cred;
 605
 606        kdebug("revert_creds(%p{%d,%d})", old,
 607               atomic_read(&old->usage),
 608               read_cred_subscribers(old));
 609
 610        validate_creds(old);
 611        validate_creds(override);
 612        alter_cred_subscribers(old, 1);
 613        rcu_assign_pointer(current->cred, old);
 614        alter_cred_subscribers(override, -1);
 615        put_cred(override);
 616}
 617EXPORT_SYMBOL(revert_creds);
 618
 619/*
 620 * initialise the credentials stuff
 621 */
 622void __init cred_init(void)
 623{
 624        /* allocate a slab in which we can store credentials */
 625        cred_jar = kmem_cache_create("cred_jar", sizeof(struct cred),
 626                                     0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
 627}
 628
 629/**
 630 * prepare_kernel_cred - Prepare a set of credentials for a kernel service
 631 * @daemon: A userspace daemon to be used as a reference
 632 *
 633 * Prepare a set of credentials for a kernel service.  This can then be used to
 634 * override a task's own credentials so that work can be done on behalf of that
 635 * task that requires a different subjective context.
 636 *
 637 * @daemon is used to provide a base for the security record, but can be NULL.
 638 * If @daemon is supplied, then the security data will be derived from that;
 639 * otherwise they'll be set to 0 and no groups, full capabilities and no keys.
 640 *
 641 * The caller may change these controls afterwards if desired.
 642 *
 643 * Returns the new credentials or NULL if out of memory.
 644 *
 645 * Does not take, and does not return holding current->cred_replace_mutex.
 646 */
 647struct cred *prepare_kernel_cred(struct task_struct *daemon)
 648{
 649#ifdef CONFIG_KEYS
 650        struct thread_group_cred *tgcred;
 651#endif
 652        const struct cred *old;
 653        struct cred *new;
 654
 655        new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
 656        if (!new)
 657                return NULL;
 658
 659#ifdef CONFIG_KEYS
 660        tgcred = kmalloc(sizeof(*tgcred), GFP_KERNEL);
 661        if (!tgcred) {
 662                kmem_cache_free(cred_jar, new);
 663                return NULL;
 664        }
 665#endif
 666
 667        kdebug("prepare_kernel_cred() alloc %p", new);
 668
 669        if (daemon)
 670                old = get_task_cred(daemon);
 671        else
 672                old = get_cred(&init_cred);
 673
 674        validate_creds(old);
 675
 676        *new = *old;
 677        atomic_set(&new->usage, 1);
 678        set_cred_subscribers(new, 0);
 679        get_uid(new->user);
 680        get_group_info(new->group_info);
 681
 682#ifdef CONFIG_KEYS
 683        atomic_set(&tgcred->usage, 1);
 684        spin_lock_init(&tgcred->lock);
 685        tgcred->process_keyring = NULL;
 686        tgcred->session_keyring = NULL;
 687        new->tgcred = tgcred;
 688        new->request_key_auth = NULL;
 689        new->thread_keyring = NULL;
 690        new->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING;
 691#endif
 692
 693#ifdef CONFIG_SECURITY
 694        new->security = NULL;
 695#endif
 696        if (security_prepare_creds(new, old, GFP_KERNEL) < 0)
 697                goto error;
 698
 699        put_cred(old);
 700        validate_creds(new);
 701        return new;
 702
 703error:
 704        put_cred(new);
 705        put_cred(old);
 706        return NULL;
 707}
 708EXPORT_SYMBOL(prepare_kernel_cred);
 709
 710/**
 711 * set_security_override - Set the security ID in a set of credentials
 712 * @new: The credentials to alter
 713 * @secid: The LSM security ID to set
 714 *
 715 * Set the LSM security ID in a set of credentials so that the subjective
 716 * security is overridden when an alternative set of credentials is used.
 717 */
 718int set_security_override(struct cred *new, u32 secid)
 719{
 720        return security_kernel_act_as(new, secid);
 721}
 722EXPORT_SYMBOL(set_security_override);
 723
 724/**
 725 * set_security_override_from_ctx - Set the security ID in a set of credentials
 726 * @new: The credentials to alter
 727 * @secctx: The LSM security context to generate the security ID from.
 728 *
 729 * Set the LSM security ID in a set of credentials so that the subjective
 730 * security is overridden when an alternative set of credentials is used.  The
 731 * security ID is specified in string form as a security context to be
 732 * interpreted by the LSM.
 733 */
 734int set_security_override_from_ctx(struct cred *new, const char *secctx)
 735{
 736        u32 secid;
 737        int ret;
 738
 739        ret = security_secctx_to_secid(secctx, strlen(secctx), &secid);
 740        if (ret < 0)
 741                return ret;
 742
 743        return set_security_override(new, secid);
 744}
 745EXPORT_SYMBOL(set_security_override_from_ctx);
 746
 747/**
 748 * set_create_files_as - Set the LSM file create context in a set of credentials
 749 * @new: The credentials to alter
 750 * @inode: The inode to take the context from
 751 *
 752 * Change the LSM file creation context in a set of credentials to be the same
 753 * as the object context of the specified inode, so that the new inodes have
 754 * the same MAC context as that inode.
 755 */
 756int set_create_files_as(struct cred *new, struct inode *inode)
 757{
 758        new->fsuid = inode->i_uid;
 759        new->fsgid = inode->i_gid;
 760        return security_kernel_create_files_as(new, inode);
 761}
 762EXPORT_SYMBOL(set_create_files_as);
 763
 764#ifdef CONFIG_DEBUG_CREDENTIALS
 765
 766bool creds_are_invalid(const struct cred *cred)
 767{
 768        if (cred->magic != CRED_MAGIC)
 769                return true;
 770#ifdef CONFIG_SECURITY_SELINUX
 771        /*
 772         * cred->security == NULL if security_cred_alloc_blank() or
 773         * security_prepare_creds() returned an error.
 774         */
 775        if (selinux_is_enabled() && cred->security) {
 776                if ((unsigned long) cred->security < PAGE_SIZE)
 777                        return true;
 778                if ((*(u32 *)cred->security & 0xffffff00) ==
 779                    (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8))
 780                        return true;
 781        }
 782#endif
 783        return false;
 784}
 785EXPORT_SYMBOL(creds_are_invalid);
 786
 787/*
 788 * dump invalid credentials
 789 */
 790static void dump_invalid_creds(const struct cred *cred, const char *label,
 791                               const struct task_struct *tsk)
 792{
 793        printk(KERN_ERR "CRED: %s credentials: %p %s%s%s\n",
 794               label, cred,
 795               cred == &init_cred ? "[init]" : "",
 796               cred == tsk->real_cred ? "[real]" : "",
 797               cred == tsk->cred ? "[eff]" : "");
 798        printk(KERN_ERR "CRED: ->magic=%x, put_addr=%p\n",
 799               cred->magic, cred->put_addr);
 800        printk(KERN_ERR "CRED: ->usage=%d, subscr=%d\n",
 801               atomic_read(&cred->usage),
 802               read_cred_subscribers(cred));
 803        printk(KERN_ERR "CRED: ->*uid = { %d,%d,%d,%d }\n",
 804               cred->uid, cred->euid, cred->suid, cred->fsuid);
 805        printk(KERN_ERR "CRED: ->*gid = { %d,%d,%d,%d }\n",
 806               cred->gid, cred->egid, cred->sgid, cred->fsgid);
 807#ifdef CONFIG_SECURITY
 808        printk(KERN_ERR "CRED: ->security is %p\n", cred->security);
 809        if ((unsigned long) cred->security >= PAGE_SIZE &&
 810            (((unsigned long) cred->security & 0xffffff00) !=
 811             (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8)))
 812                printk(KERN_ERR "CRED: ->security {%x, %x}\n",
 813                       ((u32*)cred->security)[0],
 814                       ((u32*)cred->security)[1]);
 815#endif
 816}
 817
 818/*
 819 * report use of invalid credentials
 820 */
 821void __invalid_creds(const struct cred *cred, const char *file, unsigned line)
 822{
 823        printk(KERN_ERR "CRED: Invalid credentials\n");
 824        printk(KERN_ERR "CRED: At %s:%u\n", file, line);
 825        dump_invalid_creds(cred, "Specified", current);
 826        BUG();
 827}
 828EXPORT_SYMBOL(__invalid_creds);
 829
 830/*
 831 * check the credentials on a process
 832 */
 833void __validate_process_creds(struct task_struct *tsk,
 834                              const char *file, unsigned line)
 835{
 836        if (tsk->cred == tsk->real_cred) {
 837                if (unlikely(read_cred_subscribers(tsk->cred) < 2 ||
 838                             creds_are_invalid(tsk->cred)))
 839                        goto invalid_creds;
 840        } else {
 841                if (unlikely(read_cred_subscribers(tsk->real_cred) < 1 ||
 842                             read_cred_subscribers(tsk->cred) < 1 ||
 843                             creds_are_invalid(tsk->real_cred) ||
 844                             creds_are_invalid(tsk->cred)))
 845                        goto invalid_creds;
 846        }
 847        return;
 848
 849invalid_creds:
 850        printk(KERN_ERR "CRED: Invalid process credentials\n");
 851        printk(KERN_ERR "CRED: At %s:%u\n", file, line);
 852
 853        dump_invalid_creds(tsk->real_cred, "Real", tsk);
 854        if (tsk->cred != tsk->real_cred)
 855                dump_invalid_creds(tsk->cred, "Effective", tsk);
 856        else
 857                printk(KERN_ERR "CRED: Effective creds == Real creds\n");
 858        BUG();
 859}
 860EXPORT_SYMBOL(__validate_process_creds);
 861
 862/*
 863 * check creds for do_exit()
 864 */
 865void validate_creds_for_do_exit(struct task_struct *tsk)
 866{
 867        kdebug("validate_creds_for_do_exit(%p,%p{%d,%d})",
 868               tsk->real_cred, tsk->cred,
 869               atomic_read(&tsk->cred->usage),
 870               read_cred_subscribers(tsk->cred));
 871
 872        __validate_process_creds(tsk, __FILE__, __LINE__);
 873}
 874
 875#endif /* CONFIG_DEBUG_CREDENTIALS */
 876