~ [ source navigation ] ~ [ diff markup ] ~ [ identifier search ] ~

TOMOYO Linux Cross Reference
Linux/kernel/cred.c

Version: ~ [ linux-5.1-rc2 ] ~ [ linux-5.0.3 ] ~ [ linux-4.20.17 ] ~ [ linux-4.19.30 ] ~ [ linux-4.18.20 ] ~ [ linux-4.17.19 ] ~ [ linux-4.16.18 ] ~ [ linux-4.15.18 ] ~ [ linux-4.14.107 ] ~ [ linux-4.13.16 ] ~ [ linux-4.12.14 ] ~ [ linux-4.11.12 ] ~ [ linux-4.10.17 ] ~ [ linux-4.9.164 ] ~ [ linux-4.8.17 ] ~ [ linux-4.7.10 ] ~ [ linux-4.6.7 ] ~ [ linux-4.5.7 ] ~ [ linux-4.4.176 ] ~ [ linux-4.3.6 ] ~ [ linux-4.2.8 ] ~ [ linux-4.1.52 ] ~ [ linux-4.0.9 ] ~ [ linux-3.19.8 ] ~ [ linux-3.18.136 ] ~ [ linux-3.17.8 ] ~ [ linux-3.16.63 ] ~ [ linux-3.15.10 ] ~ [ linux-3.14.79 ] ~ [ linux-3.13.11 ] ~ [ linux-3.12.74 ] ~ [ linux-3.11.10 ] ~ [ linux-3.10.108 ] ~ [ linux-3.9.11 ] ~ [ linux-3.8.13 ] ~ [ linux-3.7.10 ] ~ [ linux-3.6.11 ] ~ [ linux-3.5.7 ] ~ [ linux-3.4.113 ] ~ [ linux-3.3.8 ] ~ [ linux-3.2.102 ] ~ [ linux-3.1.10 ] ~ [ linux-3.0.101 ] ~ [ linux-2.6.39.4 ] ~ [ linux-2.6.38.8 ] ~ [ linux-2.6.37.6 ] ~ [ linux-2.6.36.4 ] ~ [ linux-2.6.35.14 ] ~ [ linux-2.6.34.15 ] ~ [ linux-2.6.33.20 ] ~ [ linux-2.6.32.71 ] ~ [ linux-2.6.0 ] ~ [ linux-2.4.37.11 ] ~ [ unix-v6-master ] ~ [ ccs-tools-1.8.5 ] ~ [ policy-sample ] ~
Architecture: ~ [ i386 ] ~ [ alpha ] ~ [ m68k ] ~ [ mips ] ~ [ ppc ] ~ [ sparc ] ~ [ sparc64 ] ~

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

~ [ source navigation ] ~ [ diff markup ] ~ [ identifier search ] ~

kernel.org | git.kernel.org | LWN.net | Project Home | Wiki (Japanese) | Wiki (English) | SVN repository | Mail admin

Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.

osdn.jp