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af777cd1 1/* Task credentials management - see Documentation/security/credentials.rst
f1752eec
DH
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 */
9984de1a 11#include <linux/export.h>
f1752eec 12#include <linux/cred.h>
5a0e3ad6 13#include <linux/slab.h>
f1752eec 14#include <linux/sched.h>
f7ccbae4 15#include <linux/sched/coredump.h>
f1752eec
DH
16#include <linux/key.h>
17#include <linux/keyctl.h>
18#include <linux/init_task.h>
19#include <linux/security.h>
40401530 20#include <linux/binfmts.h>
d84f4f99 21#include <linux/cn_proc.h>
d84f4f99 22
e0e81739 23#if 0
52aa8536
JP
24#define kdebug(FMT, ...) \
25 printk("[%-5.5s%5u] " FMT "\n", \
26 current->comm, current->pid, ##__VA_ARGS__)
e0e81739 27#else
52aa8536
JP
28#define kdebug(FMT, ...) \
29do { \
30 if (0) \
31 no_printk("[%-5.5s%5u] " FMT "\n", \
32 current->comm, current->pid, ##__VA_ARGS__); \
33} while (0)
e0e81739
DH
34#endif
35
d84f4f99 36static struct kmem_cache *cred_jar;
f1752eec 37
2813893f
IM
38/* init to 2 - one for init_task, one to ensure it is never freed */
39struct group_info init_groups = { .usage = ATOMIC_INIT(2) };
40
f1752eec
DH
41/*
42 * The initial credentials for the initial task
43 */
44struct cred init_cred = {
3b11a1de 45 .usage = ATOMIC_INIT(4),
e0e81739
DH
46#ifdef CONFIG_DEBUG_CREDENTIALS
47 .subscribers = ATOMIC_INIT(2),
48 .magic = CRED_MAGIC,
49#endif
078de5f7
EB
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,
f1752eec 58 .securebits = SECUREBITS_DEFAULT,
a3232d2f 59 .cap_inheritable = CAP_EMPTY_SET,
f1752eec 60 .cap_permitted = CAP_FULL_SET,
a3232d2f
EP
61 .cap_effective = CAP_FULL_SET,
62 .cap_bset = CAP_FULL_SET,
f1752eec 63 .user = INIT_USER,
47a150ed 64 .user_ns = &init_user_ns,
f1752eec
DH
65 .group_info = &init_groups,
66};
67
e0e81739
DH
68static 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
75static 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
84static 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
f1752eec
DH
93/*
94 * The RCU callback to actually dispose of a set of credentials
95 */
96static void put_cred_rcu(struct rcu_head *rcu)
97{
98 struct cred *cred = container_of(rcu, struct cred, rcu);
99
e0e81739
DH
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
d84f4f99
DH
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));
e0e81739 115#endif
f1752eec 116
d84f4f99 117 security_cred_free(cred);
3a50597d
DH
118 key_put(cred->session_keyring);
119 key_put(cred->process_keyring);
f1752eec
DH
120 key_put(cred->thread_keyring);
121 key_put(cred->request_key_auth);
4a5d6ba1
DH
122 if (cred->group_info)
123 put_group_info(cred->group_info);
f1752eec 124 free_uid(cred->user);
0093ccb6 125 put_user_ns(cred->user_ns);
d84f4f99 126 kmem_cache_free(cred_jar, cred);
f1752eec
DH
127}
128
129/**
130 * __put_cred - Destroy a set of credentials
d84f4f99 131 * @cred: The record to release
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DH
132 *
133 * Destroy a set of credentials on which no references remain.
134 */
135void __put_cred(struct cred *cred)
136{
e0e81739
DH
137 kdebug("__put_cred(%p{%d,%d})", cred,
138 atomic_read(&cred->usage),
139 read_cred_subscribers(cred));
140
d84f4f99 141 BUG_ON(atomic_read(&cred->usage) != 0);
e0e81739
DH
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);
d84f4f99 149
f1752eec
DH
150 call_rcu(&cred->rcu, put_cred_rcu);
151}
152EXPORT_SYMBOL(__put_cred);
153
e0e81739
DH
154/*
155 * Clean up a task's credentials when it exits
156 */
157void 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);
ee18d64c
DH
176}
177
de09a977
DH
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 */
188const 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
ee18d64c
DH
203/*
204 * Allocate blank credentials, such that the credentials can be filled in at a
205 * later date without risk of ENOMEM.
206 */
207struct 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
ee18d64c 215 atomic_set(&new->usage, 1);
2edeaa34
TH
216#ifdef CONFIG_DEBUG_CREDENTIALS
217 new->magic = CRED_MAGIC;
218#endif
ee18d64c
DH
219
220 if (security_cred_alloc_blank(new, GFP_KERNEL) < 0)
221 goto error;
222
ee18d64c
DH
223 return new;
224
225error:
226 abort_creds(new);
227 return NULL;
e0e81739
DH
228}
229
d84f4f99
DH
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 *
3b11a1de
DH
238 * Preparation involves making a copy of the objective creds for modification.
239 *
d84f4f99
DH
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 */
244struct cred *prepare_creds(void)
245{
246 struct task_struct *task = current;
247 const struct cred *old;
248 struct cred *new;
249
e0e81739 250 validate_process_creds();
d84f4f99
DH
251
252 new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
253 if (!new)
254 return NULL;
255
e0e81739
DH
256 kdebug("prepare_creds() alloc %p", new);
257
d84f4f99
DH
258 old = task->cred;
259 memcpy(new, old, sizeof(struct cred));
260
261 atomic_set(&new->usage, 1);
e0e81739 262 set_cred_subscribers(new, 0);
d84f4f99
DH
263 get_group_info(new->group_info);
264 get_uid(new->user);
0093ccb6 265 get_user_ns(new->user_ns);
d84f4f99
DH
266
267#ifdef CONFIG_KEYS
3a50597d
DH
268 key_get(new->session_keyring);
269 key_get(new->process_keyring);
d84f4f99
DH
270 key_get(new->thread_keyring);
271 key_get(new->request_key_auth);
d84f4f99
DH
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;
e0e81739 280 validate_creds(new);
d84f4f99
DH
281 return new;
282
283error:
284 abort_creds(new);
285 return NULL;
286}
287EXPORT_SYMBOL(prepare_creds);
288
a6f76f23
DH
289/*
290 * Prepare credentials for current to perform an execve()
9b1bf12d 291 * - The caller must hold ->cred_guard_mutex
a6f76f23
DH
292 */
293struct cred *prepare_exec_creds(void)
294{
a6f76f23
DH
295 struct cred *new;
296
a6f76f23 297 new = prepare_creds();
3a50597d 298 if (!new)
a6f76f23 299 return new;
a6f76f23
DH
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
a6f76f23 306 /* inherit the session keyring; new process keyring */
3a50597d
DH
307 key_put(new->process_keyring);
308 new->process_keyring = NULL;
a6f76f23
DH
309#endif
310
311 return new;
312}
313
f1752eec
DH
314/*
315 * Copy credentials for the new process created by fork()
d84f4f99
DH
316 *
317 * We share if we can, but under some circumstances we have to generate a new
318 * set.
3b11a1de
DH
319 *
320 * The new process gets the current process's subjective credentials as its
321 * objective and subjective credentials
f1752eec
DH
322 */
323int copy_creds(struct task_struct *p, unsigned long clone_flags)
324{
d84f4f99 325 struct cred *new;
18b6e041 326 int ret;
d84f4f99 327
d84f4f99
DH
328 if (
329#ifdef CONFIG_KEYS
330 !p->cred->thread_keyring &&
331#endif
332 clone_flags & CLONE_THREAD
333 ) {
3b11a1de 334 p->real_cred = get_cred(p->cred);
d84f4f99 335 get_cred(p->cred);
e0e81739
DH
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));
d84f4f99
DH
340 atomic_inc(&p->cred->user->processes);
341 return 0;
342 }
343
344 new = prepare_creds();
345 if (!new)
f1752eec
DH
346 return -ENOMEM;
347
18b6e041
SH
348 if (clone_flags & CLONE_NEWUSER) {
349 ret = create_user_ns(new);
350 if (ret < 0)
351 goto error_put;
352 }
353
bb952bb9 354#ifdef CONFIG_KEYS
d84f4f99
DH
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
3a50597d
DH
364 /* The process keyring is only shared between the threads in a process;
365 * anything outside of those threads doesn't inherit.
366 */
d84f4f99 367 if (!(clone_flags & CLONE_THREAD)) {
3a50597d
DH
368 key_put(new->process_keyring);
369 new->process_keyring = NULL;
bb952bb9
DH
370 }
371#endif
372
d84f4f99 373 atomic_inc(&new->user->processes);
3b11a1de 374 p->cred = p->real_cred = get_cred(new);
e0e81739
DH
375 alter_cred_subscribers(new, 2);
376 validate_creds(new);
d84f4f99 377 return 0;
18b6e041
SH
378
379error_put:
380 put_cred(new);
381 return ret;
d84f4f99 382}
f1752eec 383
aa6d054e
EB
384static 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
d84f4f99
DH
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
3b11a1de
DH
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.
d84f4f99
DH
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 */
423int commit_creds(struct cred *new)
424{
425 struct task_struct *task = current;
e0e81739 426 const struct cred *old = task->real_cred;
d84f4f99 427
e0e81739
DH
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
d84f4f99 438 BUG_ON(atomic_read(&new->usage) < 1);
d84f4f99 439
3b11a1de
DH
440 get_cred(new); /* we will require a ref for the subj creds too */
441
d84f4f99 442 /* dumpability changes */
078de5f7
EB
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) ||
aa6d054e 447 !cred_cap_issubset(old, new)) {
b9456371
DH
448 if (task->mm)
449 set_dumpable(task->mm, suid_dumpable);
d84f4f99
DH
450 task->pdeath_signal = 0;
451 smp_wmb();
f1752eec
DH
452 }
453
d84f4f99 454 /* alter the thread keyring */
078de5f7 455 if (!uid_eq(new->fsuid, old->fsuid))
d84f4f99 456 key_fsuid_changed(task);
078de5f7 457 if (!gid_eq(new->fsgid, old->fsgid))
d84f4f99
DH
458 key_fsgid_changed(task);
459
460 /* do it
72fa5997
VK
461 * RLIMIT_NPROC limits on user->processes have already been checked
462 * in set_user().
d84f4f99 463 */
e0e81739 464 alter_cred_subscribers(new, 2);
d84f4f99
DH
465 if (new->user != old->user)
466 atomic_inc(&new->user->processes);
3b11a1de 467 rcu_assign_pointer(task->real_cred, new);
d84f4f99
DH
468 rcu_assign_pointer(task->cred, new);
469 if (new->user != old->user)
470 atomic_dec(&old->user->processes);
e0e81739 471 alter_cred_subscribers(old, -2);
d84f4f99 472
d84f4f99 473 /* send notifications */
078de5f7
EB
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))
d84f4f99 478 proc_id_connector(task, PROC_EVENT_UID);
f1752eec 479
078de5f7
EB
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))
d84f4f99 484 proc_id_connector(task, PROC_EVENT_GID);
f1752eec 485
3b11a1de
DH
486 /* release the old obj and subj refs both */
487 put_cred(old);
d84f4f99 488 put_cred(old);
f1752eec
DH
489 return 0;
490}
d84f4f99
DH
491EXPORT_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 */
500void abort_creds(struct cred *new)
501{
e0e81739
DH
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
d84f4f99
DH
509 BUG_ON(atomic_read(&new->usage) < 1);
510 put_cred(new);
511}
512EXPORT_SYMBOL(abort_creds);
513
514/**
3b11a1de 515 * override_creds - Override the current process's subjective credentials
d84f4f99
DH
516 * @new: The credentials to be assigned
517 *
3b11a1de
DH
518 * Install a set of temporary override subjective credentials on the current
519 * process, returning the old set for later reversion.
d84f4f99
DH
520 */
521const struct cred *override_creds(const struct cred *new)
522{
523 const struct cred *old = current->cred;
524
e0e81739
DH
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));
d84f4f99
DH
539 return old;
540}
541EXPORT_SYMBOL(override_creds);
542
543/**
3b11a1de 544 * revert_creds - Revert a temporary subjective credentials override
d84f4f99
DH
545 * @old: The credentials to be restored
546 *
3b11a1de
DH
547 * Revert a temporary set of override subjective credentials to an old set,
548 * discarding the override set.
d84f4f99
DH
549 */
550void revert_creds(const struct cred *old)
551{
552 const struct cred *override = current->cred;
553
e0e81739
DH
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);
d84f4f99 561 rcu_assign_pointer(current->cred, old);
e0e81739 562 alter_cred_subscribers(override, -1);
d84f4f99
DH
563 put_cred(override);
564}
565EXPORT_SYMBOL(revert_creds);
566
567/*
568 * initialise the credentials stuff
569 */
570void __init cred_init(void)
571{
572 /* allocate a slab in which we can store credentials */
5d097056
VD
573 cred_jar = kmem_cache_create("cred_jar", sizeof(struct cred), 0,
574 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, NULL);
d84f4f99 575}
3a3b7ce9
DH
576
577/**
750ab83b
SF
578 * clone_cred - Create a new copy of a set of credentials
579 * @old: Credentials to be copied
3a3b7ce9 580 *
750ab83b
SF
581 * Prepare a new set of credentials that is an exact copy of @old. This can
582 * optionally be modified and used to override a task's own credentials so
583 * that work can be done on behalf of that task that requires a different
584 * subjective context.
3a3b7ce9 585 *
750ab83b 586 * Returns the new credentials or NULL if @old is NULL or if out of memory.
3a3b7ce9
DH
587 *
588 * Does not take, and does not return holding current->cred_replace_mutex.
589 */
750ab83b 590struct cred *clone_cred(const struct cred *old)
3a3b7ce9 591{
3a3b7ce9
DH
592 struct cred *new;
593
750ab83b
SF
594 if (!old)
595 return NULL;
596
3a3b7ce9
DH
597 new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
598 if (!new)
599 return NULL;
600
750ab83b 601 kdebug("clone_cred() alloc %p", new);
3a3b7ce9 602
e0e81739
DH
603 validate_creds(old);
604
43529c97 605 *new = *old;
fb2b2a1d
TH
606 atomic_set(&new->usage, 1);
607 set_cred_subscribers(new, 0);
3a3b7ce9 608 get_uid(new->user);
0093ccb6 609 get_user_ns(new->user_ns);
3a3b7ce9
DH
610 get_group_info(new->group_info);
611
612#ifdef CONFIG_KEYS
3a50597d
DH
613 new->session_keyring = NULL;
614 new->process_keyring = NULL;
3a3b7ce9 615 new->thread_keyring = NULL;
3a50597d 616 new->request_key_auth = NULL;
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DH
617 new->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING;
618#endif
619
620#ifdef CONFIG_SECURITY
621 new->security = NULL;
622#endif
623 if (security_prepare_creds(new, old, GFP_KERNEL) < 0)
624 goto error;
625
e0e81739 626 validate_creds(new);
3a3b7ce9
DH
627 return new;
628
629error:
630 put_cred(new);
631 return NULL;
632}
750ab83b
SF
633EXPORT_SYMBOL(clone_cred);
634
635/**
636 * prepare_kernel_cred - Prepare a set of credentials for a kernel service
637 * @daemon: A userspace daemon to be used as a reference
638 *
639 * Prepare a set of credentials for a kernel service. This can then be used to
640 * override a task's own credentials so that work can be done on behalf of that
641 * task that requires a different subjective context.
642 *
643 * @daemon is used to provide a base for the security record, but can be NULL.
644 * If @daemon is supplied, then the security data will be derived from that;
645 * otherwise they'll be set to 0 and no groups, full capabilities and no keys.
646 *
647 * The caller may change these controls afterwards if desired.
648 *
649 * Returns the new credentials or NULL if out of memory.
650 *
651 * Does not take, and does not return holding current->cred_replace_mutex.
652 */
653struct cred *prepare_kernel_cred(struct task_struct *daemon)
654{
655 const struct cred *old;
656 struct cred *new;
657
658 if (daemon)
659 old = get_task_cred(daemon);
660 else
661 old = get_cred(&init_cred);
662
663 new = clone_cred(old);
664 put_cred(old);
665 return new;
666}
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DH
667EXPORT_SYMBOL(prepare_kernel_cred);
668
669/**
670 * set_security_override - Set the security ID in a set of credentials
671 * @new: The credentials to alter
672 * @secid: The LSM security ID to set
673 *
674 * Set the LSM security ID in a set of credentials so that the subjective
675 * security is overridden when an alternative set of credentials is used.
676 */
677int set_security_override(struct cred *new, u32 secid)
678{
679 return security_kernel_act_as(new, secid);
680}
681EXPORT_SYMBOL(set_security_override);
682
683/**
684 * set_security_override_from_ctx - Set the security ID in a set of credentials
685 * @new: The credentials to alter
686 * @secctx: The LSM security context to generate the security ID from.
687 *
688 * Set the LSM security ID in a set of credentials so that the subjective
689 * security is overridden when an alternative set of credentials is used. The
690 * security ID is specified in string form as a security context to be
691 * interpreted by the LSM.
692 */
693int set_security_override_from_ctx(struct cred *new, const char *secctx)
694{
695 u32 secid;
696 int ret;
697
698 ret = security_secctx_to_secid(secctx, strlen(secctx), &secid);
699 if (ret < 0)
700 return ret;
701
702 return set_security_override(new, secid);
703}
704EXPORT_SYMBOL(set_security_override_from_ctx);
705
706/**
707 * set_create_files_as - Set the LSM file create context in a set of credentials
708 * @new: The credentials to alter
709 * @inode: The inode to take the context from
710 *
711 * Change the LSM file creation context in a set of credentials to be the same
712 * as the object context of the specified inode, so that the new inodes have
713 * the same MAC context as that inode.
714 */
715int set_create_files_as(struct cred *new, struct inode *inode)
716{
5f65e5ca
SF
717 if (!uid_valid(inode->i_uid) || !gid_valid(inode->i_gid))
718 return -EINVAL;
3a3b7ce9
DH
719 new->fsuid = inode->i_uid;
720 new->fsgid = inode->i_gid;
721 return security_kernel_create_files_as(new, inode);
722}
723EXPORT_SYMBOL(set_create_files_as);
e0e81739
DH
724
725#ifdef CONFIG_DEBUG_CREDENTIALS
726
74908a00
AM
727bool creds_are_invalid(const struct cred *cred)
728{
729 if (cred->magic != CRED_MAGIC)
730 return true;
74908a00
AM
731 return false;
732}
764db03f 733EXPORT_SYMBOL(creds_are_invalid);
74908a00 734
e0e81739
DH
735/*
736 * dump invalid credentials
737 */
738static void dump_invalid_creds(const struct cred *cred, const char *label,
739 const struct task_struct *tsk)
740{
741 printk(KERN_ERR "CRED: %s credentials: %p %s%s%s\n",
742 label, cred,
743 cred == &init_cred ? "[init]" : "",
744 cred == tsk->real_cred ? "[real]" : "",
745 cred == tsk->cred ? "[eff]" : "");
746 printk(KERN_ERR "CRED: ->magic=%x, put_addr=%p\n",
747 cred->magic, cred->put_addr);
748 printk(KERN_ERR "CRED: ->usage=%d, subscr=%d\n",
749 atomic_read(&cred->usage),
750 read_cred_subscribers(cred));
751 printk(KERN_ERR "CRED: ->*uid = { %d,%d,%d,%d }\n",
c9235f48
EB
752 from_kuid_munged(&init_user_ns, cred->uid),
753 from_kuid_munged(&init_user_ns, cred->euid),
754 from_kuid_munged(&init_user_ns, cred->suid),
755 from_kuid_munged(&init_user_ns, cred->fsuid));
e0e81739 756 printk(KERN_ERR "CRED: ->*gid = { %d,%d,%d,%d }\n",
c9235f48
EB
757 from_kgid_munged(&init_user_ns, cred->gid),
758 from_kgid_munged(&init_user_ns, cred->egid),
759 from_kgid_munged(&init_user_ns, cred->sgid),
760 from_kgid_munged(&init_user_ns, cred->fsgid));
e0e81739
DH
761#ifdef CONFIG_SECURITY
762 printk(KERN_ERR "CRED: ->security is %p\n", cred->security);
763 if ((unsigned long) cred->security >= PAGE_SIZE &&
764 (((unsigned long) cred->security & 0xffffff00) !=
765 (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8)))
766 printk(KERN_ERR "CRED: ->security {%x, %x}\n",
767 ((u32*)cred->security)[0],
768 ((u32*)cred->security)[1]);
769#endif
770}
771
772/*
773 * report use of invalid credentials
774 */
775void __invalid_creds(const struct cred *cred, const char *file, unsigned line)
776{
777 printk(KERN_ERR "CRED: Invalid credentials\n");
778 printk(KERN_ERR "CRED: At %s:%u\n", file, line);
779 dump_invalid_creds(cred, "Specified", current);
780 BUG();
781}
782EXPORT_SYMBOL(__invalid_creds);
783
784/*
785 * check the credentials on a process
786 */
787void __validate_process_creds(struct task_struct *tsk,
788 const char *file, unsigned line)
789{
790 if (tsk->cred == tsk->real_cred) {
791 if (unlikely(read_cred_subscribers(tsk->cred) < 2 ||
792 creds_are_invalid(tsk->cred)))
793 goto invalid_creds;
794 } else {
795 if (unlikely(read_cred_subscribers(tsk->real_cred) < 1 ||
796 read_cred_subscribers(tsk->cred) < 1 ||
797 creds_are_invalid(tsk->real_cred) ||
798 creds_are_invalid(tsk->cred)))
799 goto invalid_creds;
800 }
801 return;
802
803invalid_creds:
804 printk(KERN_ERR "CRED: Invalid process credentials\n");
805 printk(KERN_ERR "CRED: At %s:%u\n", file, line);
806
807 dump_invalid_creds(tsk->real_cred, "Real", tsk);
808 if (tsk->cred != tsk->real_cred)
809 dump_invalid_creds(tsk->cred, "Effective", tsk);
810 else
811 printk(KERN_ERR "CRED: Effective creds == Real creds\n");
812 BUG();
813}
814EXPORT_SYMBOL(__validate_process_creds);
815
816/*
817 * check creds for do_exit()
818 */
819void validate_creds_for_do_exit(struct task_struct *tsk)
820{
821 kdebug("validate_creds_for_do_exit(%p,%p{%d,%d})",
822 tsk->real_cred, tsk->cred,
823 atomic_read(&tsk->cred->usage),
824 read_cred_subscribers(tsk->cred));
825
826 __validate_process_creds(tsk, __FILE__, __LINE__);
827}
828
829#endif /* CONFIG_DEBUG_CREDENTIALS */