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98870ab0 | 1 | /* Task credentials management - see Documentation/credentials.txt |
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 | */ | |
11 | #include <linux/module.h> | |
12 | #include <linux/cred.h> | |
13 | #include <linux/sched.h> | |
14 | #include <linux/key.h> | |
15 | #include <linux/keyctl.h> | |
16 | #include <linux/init_task.h> | |
17 | #include <linux/security.h> | |
d84f4f99 DH |
18 | #include <linux/cn_proc.h> |
19 | #include "cred-internals.h" | |
20 | ||
e0e81739 DH |
21 | #if 0 |
22 | #define kdebug(FMT, ...) \ | |
23 | printk("[%-5.5s%5u] "FMT"\n", current->comm, current->pid ,##__VA_ARGS__) | |
24 | #else | |
25 | static inline __attribute__((format(printf, 1, 2))) | |
26 | void no_printk(const char *fmt, ...) | |
27 | { | |
28 | } | |
29 | #define kdebug(FMT, ...) \ | |
30 | no_printk("[%-5.5s%5u] "FMT"\n", current->comm, current->pid ,##__VA_ARGS__) | |
31 | #endif | |
32 | ||
d84f4f99 | 33 | static struct kmem_cache *cred_jar; |
f1752eec | 34 | |
bb952bb9 DH |
35 | /* |
36 | * The common credentials for the initial task's thread group | |
37 | */ | |
38 | #ifdef CONFIG_KEYS | |
39 | static struct thread_group_cred init_tgcred = { | |
40 | .usage = ATOMIC_INIT(2), | |
41 | .tgid = 0, | |
42 | .lock = SPIN_LOCK_UNLOCKED, | |
43 | }; | |
44 | #endif | |
45 | ||
f1752eec DH |
46 | /* |
47 | * The initial credentials for the initial task | |
48 | */ | |
49 | struct cred init_cred = { | |
3b11a1de | 50 | .usage = ATOMIC_INIT(4), |
e0e81739 DH |
51 | #ifdef CONFIG_DEBUG_CREDENTIALS |
52 | .subscribers = ATOMIC_INIT(2), | |
53 | .magic = CRED_MAGIC, | |
54 | #endif | |
f1752eec DH |
55 | .securebits = SECUREBITS_DEFAULT, |
56 | .cap_inheritable = CAP_INIT_INH_SET, | |
57 | .cap_permitted = CAP_FULL_SET, | |
58 | .cap_effective = CAP_INIT_EFF_SET, | |
59 | .cap_bset = CAP_INIT_BSET, | |
60 | .user = INIT_USER, | |
61 | .group_info = &init_groups, | |
bb952bb9 DH |
62 | #ifdef CONFIG_KEYS |
63 | .tgcred = &init_tgcred, | |
64 | #endif | |
f1752eec DH |
65 | }; |
66 | ||
e0e81739 DH |
67 | static inline void set_cred_subscribers(struct cred *cred, int n) |
68 | { | |
69 | #ifdef CONFIG_DEBUG_CREDENTIALS | |
70 | atomic_set(&cred->subscribers, n); | |
71 | #endif | |
72 | } | |
73 | ||
74 | static inline int read_cred_subscribers(const struct cred *cred) | |
75 | { | |
76 | #ifdef CONFIG_DEBUG_CREDENTIALS | |
77 | return atomic_read(&cred->subscribers); | |
78 | #else | |
79 | return 0; | |
80 | #endif | |
81 | } | |
82 | ||
83 | static inline void alter_cred_subscribers(const struct cred *_cred, int n) | |
84 | { | |
85 | #ifdef CONFIG_DEBUG_CREDENTIALS | |
86 | struct cred *cred = (struct cred *) _cred; | |
87 | ||
88 | atomic_add(n, &cred->subscribers); | |
89 | #endif | |
90 | } | |
91 | ||
bb952bb9 DH |
92 | /* |
93 | * Dispose of the shared task group credentials | |
94 | */ | |
95 | #ifdef CONFIG_KEYS | |
96 | static void release_tgcred_rcu(struct rcu_head *rcu) | |
97 | { | |
98 | struct thread_group_cred *tgcred = | |
99 | container_of(rcu, struct thread_group_cred, rcu); | |
100 | ||
101 | BUG_ON(atomic_read(&tgcred->usage) != 0); | |
102 | ||
103 | key_put(tgcred->session_keyring); | |
104 | key_put(tgcred->process_keyring); | |
105 | kfree(tgcred); | |
106 | } | |
107 | #endif | |
108 | ||
109 | /* | |
110 | * Release a set of thread group credentials. | |
111 | */ | |
a6f76f23 | 112 | static void release_tgcred(struct cred *cred) |
bb952bb9 DH |
113 | { |
114 | #ifdef CONFIG_KEYS | |
115 | struct thread_group_cred *tgcred = cred->tgcred; | |
116 | ||
117 | if (atomic_dec_and_test(&tgcred->usage)) | |
118 | call_rcu(&tgcred->rcu, release_tgcred_rcu); | |
119 | #endif | |
120 | } | |
121 | ||
f1752eec DH |
122 | /* |
123 | * The RCU callback to actually dispose of a set of credentials | |
124 | */ | |
125 | static void put_cred_rcu(struct rcu_head *rcu) | |
126 | { | |
127 | struct cred *cred = container_of(rcu, struct cred, rcu); | |
128 | ||
e0e81739 DH |
129 | kdebug("put_cred_rcu(%p)", cred); |
130 | ||
131 | #ifdef CONFIG_DEBUG_CREDENTIALS | |
132 | if (cred->magic != CRED_MAGIC_DEAD || | |
133 | atomic_read(&cred->usage) != 0 || | |
134 | read_cred_subscribers(cred) != 0) | |
135 | panic("CRED: put_cred_rcu() sees %p with" | |
136 | " mag %x, put %p, usage %d, subscr %d\n", | |
137 | cred, cred->magic, cred->put_addr, | |
138 | atomic_read(&cred->usage), | |
139 | read_cred_subscribers(cred)); | |
140 | #else | |
d84f4f99 DH |
141 | if (atomic_read(&cred->usage) != 0) |
142 | panic("CRED: put_cred_rcu() sees %p with usage %d\n", | |
143 | cred, atomic_read(&cred->usage)); | |
e0e81739 | 144 | #endif |
f1752eec | 145 | |
d84f4f99 | 146 | security_cred_free(cred); |
f1752eec DH |
147 | key_put(cred->thread_keyring); |
148 | key_put(cred->request_key_auth); | |
bb952bb9 | 149 | release_tgcred(cred); |
f1752eec DH |
150 | put_group_info(cred->group_info); |
151 | free_uid(cred->user); | |
d84f4f99 | 152 | kmem_cache_free(cred_jar, cred); |
f1752eec DH |
153 | } |
154 | ||
155 | /** | |
156 | * __put_cred - Destroy a set of credentials | |
d84f4f99 | 157 | * @cred: The record to release |
f1752eec DH |
158 | * |
159 | * Destroy a set of credentials on which no references remain. | |
160 | */ | |
161 | void __put_cred(struct cred *cred) | |
162 | { | |
e0e81739 DH |
163 | kdebug("__put_cred(%p{%d,%d})", cred, |
164 | atomic_read(&cred->usage), | |
165 | read_cred_subscribers(cred)); | |
166 | ||
d84f4f99 | 167 | BUG_ON(atomic_read(&cred->usage) != 0); |
e0e81739 DH |
168 | #ifdef CONFIG_DEBUG_CREDENTIALS |
169 | BUG_ON(read_cred_subscribers(cred) != 0); | |
170 | cred->magic = CRED_MAGIC_DEAD; | |
171 | cred->put_addr = __builtin_return_address(0); | |
172 | #endif | |
173 | BUG_ON(cred == current->cred); | |
174 | BUG_ON(cred == current->real_cred); | |
d84f4f99 | 175 | |
f1752eec DH |
176 | call_rcu(&cred->rcu, put_cred_rcu); |
177 | } | |
178 | EXPORT_SYMBOL(__put_cred); | |
179 | ||
e0e81739 DH |
180 | /* |
181 | * Clean up a task's credentials when it exits | |
182 | */ | |
183 | void exit_creds(struct task_struct *tsk) | |
184 | { | |
185 | struct cred *cred; | |
186 | ||
187 | kdebug("exit_creds(%u,%p,%p,{%d,%d})", tsk->pid, tsk->real_cred, tsk->cred, | |
188 | atomic_read(&tsk->cred->usage), | |
189 | read_cred_subscribers(tsk->cred)); | |
190 | ||
191 | cred = (struct cred *) tsk->real_cred; | |
192 | tsk->real_cred = NULL; | |
193 | validate_creds(cred); | |
194 | alter_cred_subscribers(cred, -1); | |
195 | put_cred(cred); | |
196 | ||
197 | cred = (struct cred *) tsk->cred; | |
198 | tsk->cred = NULL; | |
199 | validate_creds(cred); | |
200 | alter_cred_subscribers(cred, -1); | |
201 | put_cred(cred); | |
202 | } | |
203 | ||
d84f4f99 DH |
204 | /** |
205 | * prepare_creds - Prepare a new set of credentials for modification | |
206 | * | |
207 | * Prepare a new set of task credentials for modification. A task's creds | |
208 | * shouldn't generally be modified directly, therefore this function is used to | |
209 | * prepare a new copy, which the caller then modifies and then commits by | |
210 | * calling commit_creds(). | |
211 | * | |
3b11a1de DH |
212 | * Preparation involves making a copy of the objective creds for modification. |
213 | * | |
d84f4f99 DH |
214 | * Returns a pointer to the new creds-to-be if successful, NULL otherwise. |
215 | * | |
216 | * Call commit_creds() or abort_creds() to clean up. | |
217 | */ | |
218 | struct cred *prepare_creds(void) | |
219 | { | |
220 | struct task_struct *task = current; | |
221 | const struct cred *old; | |
222 | struct cred *new; | |
223 | ||
e0e81739 | 224 | validate_process_creds(); |
d84f4f99 DH |
225 | |
226 | new = kmem_cache_alloc(cred_jar, GFP_KERNEL); | |
227 | if (!new) | |
228 | return NULL; | |
229 | ||
e0e81739 DH |
230 | kdebug("prepare_creds() alloc %p", new); |
231 | ||
d84f4f99 DH |
232 | old = task->cred; |
233 | memcpy(new, old, sizeof(struct cred)); | |
234 | ||
235 | atomic_set(&new->usage, 1); | |
e0e81739 | 236 | set_cred_subscribers(new, 0); |
d84f4f99 DH |
237 | get_group_info(new->group_info); |
238 | get_uid(new->user); | |
239 | ||
240 | #ifdef CONFIG_KEYS | |
241 | key_get(new->thread_keyring); | |
242 | key_get(new->request_key_auth); | |
243 | atomic_inc(&new->tgcred->usage); | |
244 | #endif | |
245 | ||
246 | #ifdef CONFIG_SECURITY | |
247 | new->security = NULL; | |
248 | #endif | |
249 | ||
250 | if (security_prepare_creds(new, old, GFP_KERNEL) < 0) | |
251 | goto error; | |
e0e81739 | 252 | validate_creds(new); |
d84f4f99 DH |
253 | return new; |
254 | ||
255 | error: | |
256 | abort_creds(new); | |
257 | return NULL; | |
258 | } | |
259 | EXPORT_SYMBOL(prepare_creds); | |
260 | ||
a6f76f23 DH |
261 | /* |
262 | * Prepare credentials for current to perform an execve() | |
5e751e99 | 263 | * - The caller must hold current->cred_guard_mutex |
a6f76f23 DH |
264 | */ |
265 | struct cred *prepare_exec_creds(void) | |
266 | { | |
267 | struct thread_group_cred *tgcred = NULL; | |
268 | struct cred *new; | |
269 | ||
270 | #ifdef CONFIG_KEYS | |
271 | tgcred = kmalloc(sizeof(*tgcred), GFP_KERNEL); | |
272 | if (!tgcred) | |
273 | return NULL; | |
274 | #endif | |
275 | ||
276 | new = prepare_creds(); | |
277 | if (!new) { | |
278 | kfree(tgcred); | |
279 | return new; | |
280 | } | |
281 | ||
282 | #ifdef CONFIG_KEYS | |
283 | /* newly exec'd tasks don't get a thread keyring */ | |
284 | key_put(new->thread_keyring); | |
285 | new->thread_keyring = NULL; | |
286 | ||
287 | /* create a new per-thread-group creds for all this set of threads to | |
288 | * share */ | |
289 | memcpy(tgcred, new->tgcred, sizeof(struct thread_group_cred)); | |
290 | ||
291 | atomic_set(&tgcred->usage, 1); | |
292 | spin_lock_init(&tgcred->lock); | |
293 | ||
294 | /* inherit the session keyring; new process keyring */ | |
295 | key_get(tgcred->session_keyring); | |
296 | tgcred->process_keyring = NULL; | |
297 | ||
298 | release_tgcred(new); | |
299 | new->tgcred = tgcred; | |
300 | #endif | |
301 | ||
302 | return new; | |
303 | } | |
304 | ||
d84f4f99 DH |
305 | /* |
306 | * prepare new credentials for the usermode helper dispatcher | |
307 | */ | |
308 | struct cred *prepare_usermodehelper_creds(void) | |
309 | { | |
310 | #ifdef CONFIG_KEYS | |
311 | struct thread_group_cred *tgcred = NULL; | |
312 | #endif | |
313 | struct cred *new; | |
314 | ||
315 | #ifdef CONFIG_KEYS | |
316 | tgcred = kzalloc(sizeof(*new->tgcred), GFP_ATOMIC); | |
317 | if (!tgcred) | |
318 | return NULL; | |
319 | #endif | |
320 | ||
321 | new = kmem_cache_alloc(cred_jar, GFP_ATOMIC); | |
322 | if (!new) | |
323 | return NULL; | |
324 | ||
e0e81739 DH |
325 | kdebug("prepare_usermodehelper_creds() alloc %p", new); |
326 | ||
d84f4f99 DH |
327 | memcpy(new, &init_cred, sizeof(struct cred)); |
328 | ||
329 | atomic_set(&new->usage, 1); | |
e0e81739 | 330 | set_cred_subscribers(new, 0); |
d84f4f99 DH |
331 | get_group_info(new->group_info); |
332 | get_uid(new->user); | |
333 | ||
334 | #ifdef CONFIG_KEYS | |
335 | new->thread_keyring = NULL; | |
336 | new->request_key_auth = NULL; | |
337 | new->jit_keyring = KEY_REQKEY_DEFL_DEFAULT; | |
338 | ||
339 | atomic_set(&tgcred->usage, 1); | |
340 | spin_lock_init(&tgcred->lock); | |
341 | new->tgcred = tgcred; | |
342 | #endif | |
343 | ||
344 | #ifdef CONFIG_SECURITY | |
345 | new->security = NULL; | |
346 | #endif | |
347 | if (security_prepare_creds(new, &init_cred, GFP_ATOMIC) < 0) | |
348 | goto error; | |
e0e81739 | 349 | validate_creds(new); |
d84f4f99 DH |
350 | |
351 | BUG_ON(atomic_read(&new->usage) != 1); | |
352 | return new; | |
353 | ||
354 | error: | |
355 | put_cred(new); | |
356 | return NULL; | |
357 | } | |
358 | ||
f1752eec DH |
359 | /* |
360 | * Copy credentials for the new process created by fork() | |
d84f4f99 DH |
361 | * |
362 | * We share if we can, but under some circumstances we have to generate a new | |
363 | * set. | |
3b11a1de DH |
364 | * |
365 | * The new process gets the current process's subjective credentials as its | |
366 | * objective and subjective credentials | |
f1752eec DH |
367 | */ |
368 | int copy_creds(struct task_struct *p, unsigned long clone_flags) | |
369 | { | |
d84f4f99 DH |
370 | #ifdef CONFIG_KEYS |
371 | struct thread_group_cred *tgcred; | |
372 | #endif | |
373 | struct cred *new; | |
18b6e041 | 374 | int ret; |
d84f4f99 | 375 | |
5e751e99 | 376 | mutex_init(&p->cred_guard_mutex); |
f1752eec | 377 | |
d84f4f99 DH |
378 | if ( |
379 | #ifdef CONFIG_KEYS | |
380 | !p->cred->thread_keyring && | |
381 | #endif | |
382 | clone_flags & CLONE_THREAD | |
383 | ) { | |
3b11a1de | 384 | p->real_cred = get_cred(p->cred); |
d84f4f99 | 385 | get_cred(p->cred); |
e0e81739 DH |
386 | alter_cred_subscribers(p->cred, 2); |
387 | kdebug("share_creds(%p{%d,%d})", | |
388 | p->cred, atomic_read(&p->cred->usage), | |
389 | read_cred_subscribers(p->cred)); | |
d84f4f99 DH |
390 | atomic_inc(&p->cred->user->processes); |
391 | return 0; | |
392 | } | |
393 | ||
394 | new = prepare_creds(); | |
395 | if (!new) | |
f1752eec DH |
396 | return -ENOMEM; |
397 | ||
18b6e041 SH |
398 | if (clone_flags & CLONE_NEWUSER) { |
399 | ret = create_user_ns(new); | |
400 | if (ret < 0) | |
401 | goto error_put; | |
402 | } | |
403 | ||
bb952bb9 | 404 | #ifdef CONFIG_KEYS |
d84f4f99 DH |
405 | /* new threads get their own thread keyrings if their parent already |
406 | * had one */ | |
407 | if (new->thread_keyring) { | |
408 | key_put(new->thread_keyring); | |
409 | new->thread_keyring = NULL; | |
410 | if (clone_flags & CLONE_THREAD) | |
411 | install_thread_keyring_to_cred(new); | |
412 | } | |
413 | ||
414 | /* we share the process and session keyrings between all the threads in | |
415 | * a process - this is slightly icky as we violate COW credentials a | |
416 | * bit */ | |
417 | if (!(clone_flags & CLONE_THREAD)) { | |
418 | tgcred = kmalloc(sizeof(*tgcred), GFP_KERNEL); | |
419 | if (!tgcred) { | |
18b6e041 SH |
420 | ret = -ENOMEM; |
421 | goto error_put; | |
bb952bb9 | 422 | } |
d84f4f99 DH |
423 | atomic_set(&tgcred->usage, 1); |
424 | spin_lock_init(&tgcred->lock); | |
425 | tgcred->process_keyring = NULL; | |
426 | tgcred->session_keyring = key_get(new->tgcred->session_keyring); | |
427 | ||
428 | release_tgcred(new); | |
429 | new->tgcred = tgcred; | |
bb952bb9 DH |
430 | } |
431 | #endif | |
432 | ||
d84f4f99 | 433 | atomic_inc(&new->user->processes); |
3b11a1de | 434 | p->cred = p->real_cred = get_cred(new); |
e0e81739 DH |
435 | alter_cred_subscribers(new, 2); |
436 | validate_creds(new); | |
d84f4f99 | 437 | return 0; |
18b6e041 SH |
438 | |
439 | error_put: | |
440 | put_cred(new); | |
441 | return ret; | |
d84f4f99 | 442 | } |
f1752eec | 443 | |
d84f4f99 DH |
444 | /** |
445 | * commit_creds - Install new credentials upon the current task | |
446 | * @new: The credentials to be assigned | |
447 | * | |
448 | * Install a new set of credentials to the current task, using RCU to replace | |
3b11a1de DH |
449 | * the old set. Both the objective and the subjective credentials pointers are |
450 | * updated. This function may not be called if the subjective credentials are | |
451 | * in an overridden state. | |
d84f4f99 DH |
452 | * |
453 | * This function eats the caller's reference to the new credentials. | |
454 | * | |
455 | * Always returns 0 thus allowing this function to be tail-called at the end | |
456 | * of, say, sys_setgid(). | |
457 | */ | |
458 | int commit_creds(struct cred *new) | |
459 | { | |
460 | struct task_struct *task = current; | |
e0e81739 | 461 | const struct cred *old = task->real_cred; |
d84f4f99 | 462 | |
e0e81739 DH |
463 | kdebug("commit_creds(%p{%d,%d})", new, |
464 | atomic_read(&new->usage), | |
465 | read_cred_subscribers(new)); | |
466 | ||
467 | BUG_ON(task->cred != old); | |
468 | #ifdef CONFIG_DEBUG_CREDENTIALS | |
469 | BUG_ON(read_cred_subscribers(old) < 2); | |
470 | validate_creds(old); | |
471 | validate_creds(new); | |
472 | #endif | |
d84f4f99 | 473 | BUG_ON(atomic_read(&new->usage) < 1); |
d84f4f99 | 474 | |
d84f4f99 DH |
475 | security_commit_creds(new, old); |
476 | ||
3b11a1de DH |
477 | get_cred(new); /* we will require a ref for the subj creds too */ |
478 | ||
d84f4f99 DH |
479 | /* dumpability changes */ |
480 | if (old->euid != new->euid || | |
481 | old->egid != new->egid || | |
482 | old->fsuid != new->fsuid || | |
483 | old->fsgid != new->fsgid || | |
484 | !cap_issubset(new->cap_permitted, old->cap_permitted)) { | |
b9456371 DH |
485 | if (task->mm) |
486 | set_dumpable(task->mm, suid_dumpable); | |
d84f4f99 DH |
487 | task->pdeath_signal = 0; |
488 | smp_wmb(); | |
f1752eec DH |
489 | } |
490 | ||
d84f4f99 DH |
491 | /* alter the thread keyring */ |
492 | if (new->fsuid != old->fsuid) | |
493 | key_fsuid_changed(task); | |
494 | if (new->fsgid != old->fsgid) | |
495 | key_fsgid_changed(task); | |
496 | ||
497 | /* do it | |
498 | * - What if a process setreuid()'s and this brings the | |
499 | * new uid over his NPROC rlimit? We can check this now | |
500 | * cheaply with the new uid cache, so if it matters | |
501 | * we should be checking for it. -DaveM | |
502 | */ | |
e0e81739 | 503 | alter_cred_subscribers(new, 2); |
d84f4f99 DH |
504 | if (new->user != old->user) |
505 | atomic_inc(&new->user->processes); | |
3b11a1de | 506 | rcu_assign_pointer(task->real_cred, new); |
d84f4f99 DH |
507 | rcu_assign_pointer(task->cred, new); |
508 | if (new->user != old->user) | |
509 | atomic_dec(&old->user->processes); | |
e0e81739 | 510 | alter_cred_subscribers(old, -2); |
d84f4f99 DH |
511 | |
512 | sched_switch_user(task); | |
513 | ||
514 | /* send notifications */ | |
515 | if (new->uid != old->uid || | |
516 | new->euid != old->euid || | |
517 | new->suid != old->suid || | |
518 | new->fsuid != old->fsuid) | |
519 | proc_id_connector(task, PROC_EVENT_UID); | |
f1752eec | 520 | |
d84f4f99 DH |
521 | if (new->gid != old->gid || |
522 | new->egid != old->egid || | |
523 | new->sgid != old->sgid || | |
524 | new->fsgid != old->fsgid) | |
525 | proc_id_connector(task, PROC_EVENT_GID); | |
f1752eec | 526 | |
3b11a1de DH |
527 | /* release the old obj and subj refs both */ |
528 | put_cred(old); | |
d84f4f99 | 529 | put_cred(old); |
f1752eec DH |
530 | return 0; |
531 | } | |
d84f4f99 DH |
532 | EXPORT_SYMBOL(commit_creds); |
533 | ||
534 | /** | |
535 | * abort_creds - Discard a set of credentials and unlock the current task | |
536 | * @new: The credentials that were going to be applied | |
537 | * | |
538 | * Discard a set of credentials that were under construction and unlock the | |
539 | * current task. | |
540 | */ | |
541 | void abort_creds(struct cred *new) | |
542 | { | |
e0e81739 DH |
543 | kdebug("abort_creds(%p{%d,%d})", new, |
544 | atomic_read(&new->usage), | |
545 | read_cred_subscribers(new)); | |
546 | ||
547 | #ifdef CONFIG_DEBUG_CREDENTIALS | |
548 | BUG_ON(read_cred_subscribers(new) != 0); | |
549 | #endif | |
d84f4f99 DH |
550 | BUG_ON(atomic_read(&new->usage) < 1); |
551 | put_cred(new); | |
552 | } | |
553 | EXPORT_SYMBOL(abort_creds); | |
554 | ||
555 | /** | |
3b11a1de | 556 | * override_creds - Override the current process's subjective credentials |
d84f4f99 DH |
557 | * @new: The credentials to be assigned |
558 | * | |
3b11a1de DH |
559 | * Install a set of temporary override subjective credentials on the current |
560 | * process, returning the old set for later reversion. | |
d84f4f99 DH |
561 | */ |
562 | const struct cred *override_creds(const struct cred *new) | |
563 | { | |
564 | const struct cred *old = current->cred; | |
565 | ||
e0e81739 DH |
566 | kdebug("override_creds(%p{%d,%d})", new, |
567 | atomic_read(&new->usage), | |
568 | read_cred_subscribers(new)); | |
569 | ||
570 | validate_creds(old); | |
571 | validate_creds(new); | |
572 | get_cred(new); | |
573 | alter_cred_subscribers(new, 1); | |
574 | rcu_assign_pointer(current->cred, new); | |
575 | alter_cred_subscribers(old, -1); | |
576 | ||
577 | kdebug("override_creds() = %p{%d,%d}", old, | |
578 | atomic_read(&old->usage), | |
579 | read_cred_subscribers(old)); | |
d84f4f99 DH |
580 | return old; |
581 | } | |
582 | EXPORT_SYMBOL(override_creds); | |
583 | ||
584 | /** | |
3b11a1de | 585 | * revert_creds - Revert a temporary subjective credentials override |
d84f4f99 DH |
586 | * @old: The credentials to be restored |
587 | * | |
3b11a1de DH |
588 | * Revert a temporary set of override subjective credentials to an old set, |
589 | * discarding the override set. | |
d84f4f99 DH |
590 | */ |
591 | void revert_creds(const struct cred *old) | |
592 | { | |
593 | const struct cred *override = current->cred; | |
594 | ||
e0e81739 DH |
595 | kdebug("revert_creds(%p{%d,%d})", old, |
596 | atomic_read(&old->usage), | |
597 | read_cred_subscribers(old)); | |
598 | ||
599 | validate_creds(old); | |
600 | validate_creds(override); | |
601 | alter_cred_subscribers(old, 1); | |
d84f4f99 | 602 | rcu_assign_pointer(current->cred, old); |
e0e81739 | 603 | alter_cred_subscribers(override, -1); |
d84f4f99 DH |
604 | put_cred(override); |
605 | } | |
606 | EXPORT_SYMBOL(revert_creds); | |
607 | ||
608 | /* | |
609 | * initialise the credentials stuff | |
610 | */ | |
611 | void __init cred_init(void) | |
612 | { | |
613 | /* allocate a slab in which we can store credentials */ | |
614 | cred_jar = kmem_cache_create("cred_jar", sizeof(struct cred), | |
615 | 0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); | |
616 | } | |
3a3b7ce9 DH |
617 | |
618 | /** | |
619 | * prepare_kernel_cred - Prepare a set of credentials for a kernel service | |
620 | * @daemon: A userspace daemon to be used as a reference | |
621 | * | |
622 | * Prepare a set of credentials for a kernel service. This can then be used to | |
623 | * override a task's own credentials so that work can be done on behalf of that | |
624 | * task that requires a different subjective context. | |
625 | * | |
626 | * @daemon is used to provide a base for the security record, but can be NULL. | |
627 | * If @daemon is supplied, then the security data will be derived from that; | |
628 | * otherwise they'll be set to 0 and no groups, full capabilities and no keys. | |
629 | * | |
630 | * The caller may change these controls afterwards if desired. | |
631 | * | |
632 | * Returns the new credentials or NULL if out of memory. | |
633 | * | |
634 | * Does not take, and does not return holding current->cred_replace_mutex. | |
635 | */ | |
636 | struct cred *prepare_kernel_cred(struct task_struct *daemon) | |
637 | { | |
638 | const struct cred *old; | |
639 | struct cred *new; | |
640 | ||
641 | new = kmem_cache_alloc(cred_jar, GFP_KERNEL); | |
642 | if (!new) | |
643 | return NULL; | |
644 | ||
e0e81739 DH |
645 | kdebug("prepare_kernel_cred() alloc %p", new); |
646 | ||
3a3b7ce9 DH |
647 | if (daemon) |
648 | old = get_task_cred(daemon); | |
649 | else | |
650 | old = get_cred(&init_cred); | |
651 | ||
e0e81739 DH |
652 | validate_creds(old); |
653 | ||
43529c97 | 654 | *new = *old; |
3a3b7ce9 DH |
655 | get_uid(new->user); |
656 | get_group_info(new->group_info); | |
657 | ||
658 | #ifdef CONFIG_KEYS | |
659 | atomic_inc(&init_tgcred.usage); | |
660 | new->tgcred = &init_tgcred; | |
661 | new->request_key_auth = NULL; | |
662 | new->thread_keyring = NULL; | |
663 | new->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING; | |
664 | #endif | |
665 | ||
666 | #ifdef CONFIG_SECURITY | |
667 | new->security = NULL; | |
668 | #endif | |
669 | if (security_prepare_creds(new, old, GFP_KERNEL) < 0) | |
670 | goto error; | |
671 | ||
672 | atomic_set(&new->usage, 1); | |
e0e81739 | 673 | set_cred_subscribers(new, 0); |
3a3b7ce9 | 674 | put_cred(old); |
e0e81739 | 675 | validate_creds(new); |
3a3b7ce9 DH |
676 | return new; |
677 | ||
678 | error: | |
679 | put_cred(new); | |
0de33681 | 680 | put_cred(old); |
3a3b7ce9 DH |
681 | return NULL; |
682 | } | |
683 | EXPORT_SYMBOL(prepare_kernel_cred); | |
684 | ||
685 | /** | |
686 | * set_security_override - Set the security ID in a set of credentials | |
687 | * @new: The credentials to alter | |
688 | * @secid: The LSM security ID to set | |
689 | * | |
690 | * Set the LSM security ID in a set of credentials so that the subjective | |
691 | * security is overridden when an alternative set of credentials is used. | |
692 | */ | |
693 | int set_security_override(struct cred *new, u32 secid) | |
694 | { | |
695 | return security_kernel_act_as(new, secid); | |
696 | } | |
697 | EXPORT_SYMBOL(set_security_override); | |
698 | ||
699 | /** | |
700 | * set_security_override_from_ctx - Set the security ID in a set of credentials | |
701 | * @new: The credentials to alter | |
702 | * @secctx: The LSM security context to generate the security ID from. | |
703 | * | |
704 | * Set the LSM security ID in a set of credentials so that the subjective | |
705 | * security is overridden when an alternative set of credentials is used. The | |
706 | * security ID is specified in string form as a security context to be | |
707 | * interpreted by the LSM. | |
708 | */ | |
709 | int set_security_override_from_ctx(struct cred *new, const char *secctx) | |
710 | { | |
711 | u32 secid; | |
712 | int ret; | |
713 | ||
714 | ret = security_secctx_to_secid(secctx, strlen(secctx), &secid); | |
715 | if (ret < 0) | |
716 | return ret; | |
717 | ||
718 | return set_security_override(new, secid); | |
719 | } | |
720 | EXPORT_SYMBOL(set_security_override_from_ctx); | |
721 | ||
722 | /** | |
723 | * set_create_files_as - Set the LSM file create context in a set of credentials | |
724 | * @new: The credentials to alter | |
725 | * @inode: The inode to take the context from | |
726 | * | |
727 | * Change the LSM file creation context in a set of credentials to be the same | |
728 | * as the object context of the specified inode, so that the new inodes have | |
729 | * the same MAC context as that inode. | |
730 | */ | |
731 | int set_create_files_as(struct cred *new, struct inode *inode) | |
732 | { | |
733 | new->fsuid = inode->i_uid; | |
734 | new->fsgid = inode->i_gid; | |
735 | return security_kernel_create_files_as(new, inode); | |
736 | } | |
737 | EXPORT_SYMBOL(set_create_files_as); | |
e0e81739 DH |
738 | |
739 | #ifdef CONFIG_DEBUG_CREDENTIALS | |
740 | ||
741 | /* | |
742 | * dump invalid credentials | |
743 | */ | |
744 | static void dump_invalid_creds(const struct cred *cred, const char *label, | |
745 | const struct task_struct *tsk) | |
746 | { | |
747 | printk(KERN_ERR "CRED: %s credentials: %p %s%s%s\n", | |
748 | label, cred, | |
749 | cred == &init_cred ? "[init]" : "", | |
750 | cred == tsk->real_cred ? "[real]" : "", | |
751 | cred == tsk->cred ? "[eff]" : ""); | |
752 | printk(KERN_ERR "CRED: ->magic=%x, put_addr=%p\n", | |
753 | cred->magic, cred->put_addr); | |
754 | printk(KERN_ERR "CRED: ->usage=%d, subscr=%d\n", | |
755 | atomic_read(&cred->usage), | |
756 | read_cred_subscribers(cred)); | |
757 | printk(KERN_ERR "CRED: ->*uid = { %d,%d,%d,%d }\n", | |
758 | cred->uid, cred->euid, cred->suid, cred->fsuid); | |
759 | printk(KERN_ERR "CRED: ->*gid = { %d,%d,%d,%d }\n", | |
760 | cred->gid, cred->egid, cred->sgid, cred->fsgid); | |
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 | */ | |
775 | void __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 | } | |
782 | EXPORT_SYMBOL(__invalid_creds); | |
783 | ||
784 | /* | |
785 | * check the credentials on a process | |
786 | */ | |
787 | void __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 | ||
803 | invalid_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 | } | |
814 | EXPORT_SYMBOL(__validate_process_creds); | |
815 | ||
816 | /* | |
817 | * check creds for do_exit() | |
818 | */ | |
819 | void 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 */ |