]>
Commit | Line | Data |
---|---|---|
b4d0d230 | 1 | // SPDX-License-Identifier: GPL-2.0-or-later |
af777cd1 | 2 | /* Task credentials management - see Documentation/security/credentials.rst |
f1752eec DH |
3 | * |
4 | * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved. | |
5 | * Written by David Howells (dhowells@redhat.com) | |
f1752eec | 6 | */ |
9984de1a | 7 | #include <linux/export.h> |
f1752eec | 8 | #include <linux/cred.h> |
5a0e3ad6 | 9 | #include <linux/slab.h> |
f1752eec | 10 | #include <linux/sched.h> |
f7ccbae4 | 11 | #include <linux/sched/coredump.h> |
f1752eec DH |
12 | #include <linux/key.h> |
13 | #include <linux/keyctl.h> | |
14 | #include <linux/init_task.h> | |
15 | #include <linux/security.h> | |
40401530 | 16 | #include <linux/binfmts.h> |
d84f4f99 | 17 | #include <linux/cn_proc.h> |
d89b22d4 | 18 | #include <linux/uidgid.h> |
d84f4f99 | 19 | |
e0e81739 | 20 | #if 0 |
52aa8536 JP |
21 | #define kdebug(FMT, ...) \ |
22 | printk("[%-5.5s%5u] " FMT "\n", \ | |
23 | current->comm, current->pid, ##__VA_ARGS__) | |
e0e81739 | 24 | #else |
52aa8536 JP |
25 | #define kdebug(FMT, ...) \ |
26 | do { \ | |
27 | if (0) \ | |
28 | no_printk("[%-5.5s%5u] " FMT "\n", \ | |
29 | current->comm, current->pid, ##__VA_ARGS__); \ | |
30 | } while (0) | |
e0e81739 DH |
31 | #endif |
32 | ||
d84f4f99 | 33 | static struct kmem_cache *cred_jar; |
f1752eec | 34 | |
2813893f IM |
35 | /* init to 2 - one for init_task, one to ensure it is never freed */ |
36 | struct group_info init_groups = { .usage = ATOMIC_INIT(2) }; | |
37 | ||
f1752eec DH |
38 | /* |
39 | * The initial credentials for the initial task | |
40 | */ | |
41 | struct cred init_cred = { | |
3b11a1de | 42 | .usage = ATOMIC_INIT(4), |
e0e81739 DH |
43 | #ifdef CONFIG_DEBUG_CREDENTIALS |
44 | .subscribers = ATOMIC_INIT(2), | |
45 | .magic = CRED_MAGIC, | |
46 | #endif | |
078de5f7 EB |
47 | .uid = GLOBAL_ROOT_UID, |
48 | .gid = GLOBAL_ROOT_GID, | |
49 | .suid = GLOBAL_ROOT_UID, | |
50 | .sgid = GLOBAL_ROOT_GID, | |
51 | .euid = GLOBAL_ROOT_UID, | |
52 | .egid = GLOBAL_ROOT_GID, | |
53 | .fsuid = GLOBAL_ROOT_UID, | |
54 | .fsgid = GLOBAL_ROOT_GID, | |
f1752eec | 55 | .securebits = SECUREBITS_DEFAULT, |
a3232d2f | 56 | .cap_inheritable = CAP_EMPTY_SET, |
f1752eec | 57 | .cap_permitted = CAP_FULL_SET, |
a3232d2f EP |
58 | .cap_effective = CAP_FULL_SET, |
59 | .cap_bset = CAP_FULL_SET, | |
f1752eec | 60 | .user = INIT_USER, |
47a150ed | 61 | .user_ns = &init_user_ns, |
f1752eec DH |
62 | .group_info = &init_groups, |
63 | }; | |
64 | ||
e0e81739 DH |
65 | static inline void set_cred_subscribers(struct cred *cred, int n) |
66 | { | |
67 | #ifdef CONFIG_DEBUG_CREDENTIALS | |
68 | atomic_set(&cred->subscribers, n); | |
69 | #endif | |
70 | } | |
71 | ||
72 | static inline int read_cred_subscribers(const struct cred *cred) | |
73 | { | |
74 | #ifdef CONFIG_DEBUG_CREDENTIALS | |
75 | return atomic_read(&cred->subscribers); | |
76 | #else | |
77 | return 0; | |
78 | #endif | |
79 | } | |
80 | ||
81 | static inline void alter_cred_subscribers(const struct cred *_cred, int n) | |
82 | { | |
83 | #ifdef CONFIG_DEBUG_CREDENTIALS | |
84 | struct cred *cred = (struct cred *) _cred; | |
85 | ||
86 | atomic_add(n, &cred->subscribers); | |
87 | #endif | |
88 | } | |
89 | ||
f1752eec DH |
90 | /* |
91 | * The RCU callback to actually dispose of a set of credentials | |
92 | */ | |
93 | static void put_cred_rcu(struct rcu_head *rcu) | |
94 | { | |
95 | struct cred *cred = container_of(rcu, struct cred, rcu); | |
96 | ||
e0e81739 DH |
97 | kdebug("put_cred_rcu(%p)", cred); |
98 | ||
99 | #ifdef CONFIG_DEBUG_CREDENTIALS | |
100 | if (cred->magic != CRED_MAGIC_DEAD || | |
101 | atomic_read(&cred->usage) != 0 || | |
102 | read_cred_subscribers(cred) != 0) | |
103 | panic("CRED: put_cred_rcu() sees %p with" | |
104 | " mag %x, put %p, usage %d, subscr %d\n", | |
105 | cred, cred->magic, cred->put_addr, | |
106 | atomic_read(&cred->usage), | |
107 | read_cred_subscribers(cred)); | |
108 | #else | |
d84f4f99 DH |
109 | if (atomic_read(&cred->usage) != 0) |
110 | panic("CRED: put_cred_rcu() sees %p with usage %d\n", | |
111 | cred, atomic_read(&cred->usage)); | |
e0e81739 | 112 | #endif |
f1752eec | 113 | |
d84f4f99 | 114 | security_cred_free(cred); |
3a50597d DH |
115 | key_put(cred->session_keyring); |
116 | key_put(cred->process_keyring); | |
f1752eec DH |
117 | key_put(cred->thread_keyring); |
118 | key_put(cred->request_key_auth); | |
4a5d6ba1 DH |
119 | if (cred->group_info) |
120 | put_group_info(cred->group_info); | |
f1752eec | 121 | free_uid(cred->user); |
0093ccb6 | 122 | put_user_ns(cred->user_ns); |
d84f4f99 | 123 | kmem_cache_free(cred_jar, cred); |
f1752eec DH |
124 | } |
125 | ||
126 | /** | |
127 | * __put_cred - Destroy a set of credentials | |
d84f4f99 | 128 | * @cred: The record to release |
f1752eec DH |
129 | * |
130 | * Destroy a set of credentials on which no references remain. | |
131 | */ | |
132 | void __put_cred(struct cred *cred) | |
133 | { | |
e0e81739 DH |
134 | kdebug("__put_cred(%p{%d,%d})", cred, |
135 | atomic_read(&cred->usage), | |
136 | read_cred_subscribers(cred)); | |
137 | ||
d84f4f99 | 138 | BUG_ON(atomic_read(&cred->usage) != 0); |
e0e81739 DH |
139 | #ifdef CONFIG_DEBUG_CREDENTIALS |
140 | BUG_ON(read_cred_subscribers(cred) != 0); | |
141 | cred->magic = CRED_MAGIC_DEAD; | |
142 | cred->put_addr = __builtin_return_address(0); | |
143 | #endif | |
144 | BUG_ON(cred == current->cred); | |
145 | BUG_ON(cred == current->real_cred); | |
d84f4f99 | 146 | |
f1752eec DH |
147 | call_rcu(&cred->rcu, put_cred_rcu); |
148 | } | |
149 | EXPORT_SYMBOL(__put_cred); | |
150 | ||
e0e81739 DH |
151 | /* |
152 | * Clean up a task's credentials when it exits | |
153 | */ | |
154 | void exit_creds(struct task_struct *tsk) | |
155 | { | |
156 | struct cred *cred; | |
157 | ||
158 | kdebug("exit_creds(%u,%p,%p,{%d,%d})", tsk->pid, tsk->real_cred, tsk->cred, | |
159 | atomic_read(&tsk->cred->usage), | |
160 | read_cred_subscribers(tsk->cred)); | |
161 | ||
162 | cred = (struct cred *) tsk->real_cred; | |
163 | tsk->real_cred = NULL; | |
164 | validate_creds(cred); | |
165 | alter_cred_subscribers(cred, -1); | |
166 | put_cred(cred); | |
167 | ||
168 | cred = (struct cred *) tsk->cred; | |
169 | tsk->cred = NULL; | |
170 | validate_creds(cred); | |
171 | alter_cred_subscribers(cred, -1); | |
172 | put_cred(cred); | |
7743c48e DH |
173 | |
174 | #ifdef CONFIG_KEYS_REQUEST_CACHE | |
175 | key_put(current->cached_requested_key); | |
176 | current->cached_requested_key = NULL; | |
177 | #endif | |
ee18d64c DH |
178 | } |
179 | ||
de09a977 DH |
180 | /** |
181 | * get_task_cred - Get another task's objective credentials | |
182 | * @task: The task to query | |
183 | * | |
184 | * Get the objective credentials of a task, pinning them so that they can't go | |
185 | * away. Accessing a task's credentials directly is not permitted. | |
186 | * | |
187 | * The caller must also make sure task doesn't get deleted, either by holding a | |
188 | * ref on task or by holding tasklist_lock to prevent it from being unlinked. | |
189 | */ | |
190 | const struct cred *get_task_cred(struct task_struct *task) | |
191 | { | |
192 | const struct cred *cred; | |
193 | ||
194 | rcu_read_lock(); | |
195 | ||
196 | do { | |
197 | cred = __task_cred((task)); | |
198 | BUG_ON(!cred); | |
97d0fb23 | 199 | } while (!get_cred_rcu(cred)); |
de09a977 DH |
200 | |
201 | rcu_read_unlock(); | |
202 | return cred; | |
203 | } | |
a6d8e763 | 204 | EXPORT_SYMBOL(get_task_cred); |
de09a977 | 205 | |
ee18d64c DH |
206 | /* |
207 | * Allocate blank credentials, such that the credentials can be filled in at a | |
208 | * later date without risk of ENOMEM. | |
209 | */ | |
210 | struct cred *cred_alloc_blank(void) | |
211 | { | |
212 | struct cred *new; | |
213 | ||
214 | new = kmem_cache_zalloc(cred_jar, GFP_KERNEL); | |
215 | if (!new) | |
216 | return NULL; | |
217 | ||
ee18d64c | 218 | atomic_set(&new->usage, 1); |
2edeaa34 TH |
219 | #ifdef CONFIG_DEBUG_CREDENTIALS |
220 | new->magic = CRED_MAGIC; | |
221 | #endif | |
ee18d64c DH |
222 | |
223 | if (security_cred_alloc_blank(new, GFP_KERNEL) < 0) | |
224 | goto error; | |
225 | ||
ee18d64c DH |
226 | return new; |
227 | ||
228 | error: | |
229 | abort_creds(new); | |
230 | return NULL; | |
e0e81739 DH |
231 | } |
232 | ||
d84f4f99 DH |
233 | /** |
234 | * prepare_creds - Prepare a new set of credentials for modification | |
235 | * | |
236 | * Prepare a new set of task credentials for modification. A task's creds | |
237 | * shouldn't generally be modified directly, therefore this function is used to | |
238 | * prepare a new copy, which the caller then modifies and then commits by | |
239 | * calling commit_creds(). | |
240 | * | |
3b11a1de DH |
241 | * Preparation involves making a copy of the objective creds for modification. |
242 | * | |
d84f4f99 DH |
243 | * Returns a pointer to the new creds-to-be if successful, NULL otherwise. |
244 | * | |
245 | * Call commit_creds() or abort_creds() to clean up. | |
246 | */ | |
247 | struct cred *prepare_creds(void) | |
248 | { | |
249 | struct task_struct *task = current; | |
250 | const struct cred *old; | |
251 | struct cred *new; | |
252 | ||
e0e81739 | 253 | validate_process_creds(); |
d84f4f99 DH |
254 | |
255 | new = kmem_cache_alloc(cred_jar, GFP_KERNEL); | |
256 | if (!new) | |
257 | return NULL; | |
258 | ||
e0e81739 DH |
259 | kdebug("prepare_creds() alloc %p", new); |
260 | ||
d84f4f99 DH |
261 | old = task->cred; |
262 | memcpy(new, old, sizeof(struct cred)); | |
263 | ||
264 | atomic_set(&new->usage, 1); | |
e0e81739 | 265 | set_cred_subscribers(new, 0); |
d84f4f99 DH |
266 | get_group_info(new->group_info); |
267 | get_uid(new->user); | |
0093ccb6 | 268 | get_user_ns(new->user_ns); |
d84f4f99 DH |
269 | |
270 | #ifdef CONFIG_KEYS | |
3a50597d DH |
271 | key_get(new->session_keyring); |
272 | key_get(new->process_keyring); | |
d84f4f99 DH |
273 | key_get(new->thread_keyring); |
274 | key_get(new->request_key_auth); | |
d84f4f99 DH |
275 | #endif |
276 | ||
277 | #ifdef CONFIG_SECURITY | |
278 | new->security = NULL; | |
279 | #endif | |
280 | ||
281 | if (security_prepare_creds(new, old, GFP_KERNEL) < 0) | |
282 | goto error; | |
e0e81739 | 283 | validate_creds(new); |
d84f4f99 DH |
284 | return new; |
285 | ||
286 | error: | |
287 | abort_creds(new); | |
288 | return NULL; | |
289 | } | |
290 | EXPORT_SYMBOL(prepare_creds); | |
291 | ||
a6f76f23 DH |
292 | /* |
293 | * Prepare credentials for current to perform an execve() | |
9b1bf12d | 294 | * - The caller must hold ->cred_guard_mutex |
a6f76f23 DH |
295 | */ |
296 | struct cred *prepare_exec_creds(void) | |
297 | { | |
a6f76f23 DH |
298 | struct cred *new; |
299 | ||
a6f76f23 | 300 | new = prepare_creds(); |
3a50597d | 301 | if (!new) |
a6f76f23 | 302 | return new; |
a6f76f23 DH |
303 | |
304 | #ifdef CONFIG_KEYS | |
305 | /* newly exec'd tasks don't get a thread keyring */ | |
306 | key_put(new->thread_keyring); | |
307 | new->thread_keyring = NULL; | |
308 | ||
a6f76f23 | 309 | /* inherit the session keyring; new process keyring */ |
3a50597d DH |
310 | key_put(new->process_keyring); |
311 | new->process_keyring = NULL; | |
a6f76f23 DH |
312 | #endif |
313 | ||
314 | return new; | |
315 | } | |
316 | ||
f1752eec DH |
317 | /* |
318 | * Copy credentials for the new process created by fork() | |
d84f4f99 DH |
319 | * |
320 | * We share if we can, but under some circumstances we have to generate a new | |
321 | * set. | |
3b11a1de DH |
322 | * |
323 | * The new process gets the current process's subjective credentials as its | |
324 | * objective and subjective credentials | |
f1752eec DH |
325 | */ |
326 | int copy_creds(struct task_struct *p, unsigned long clone_flags) | |
327 | { | |
d84f4f99 | 328 | struct cred *new; |
18b6e041 | 329 | int ret; |
d84f4f99 | 330 | |
7743c48e DH |
331 | #ifdef CONFIG_KEYS_REQUEST_CACHE |
332 | p->cached_requested_key = NULL; | |
333 | #endif | |
334 | ||
d84f4f99 DH |
335 | if ( |
336 | #ifdef CONFIG_KEYS | |
337 | !p->cred->thread_keyring && | |
338 | #endif | |
339 | clone_flags & CLONE_THREAD | |
340 | ) { | |
3b11a1de | 341 | p->real_cred = get_cred(p->cred); |
d84f4f99 | 342 | get_cred(p->cred); |
e0e81739 DH |
343 | alter_cred_subscribers(p->cred, 2); |
344 | kdebug("share_creds(%p{%d,%d})", | |
345 | p->cred, atomic_read(&p->cred->usage), | |
346 | read_cred_subscribers(p->cred)); | |
d84f4f99 DH |
347 | atomic_inc(&p->cred->user->processes); |
348 | return 0; | |
349 | } | |
350 | ||
351 | new = prepare_creds(); | |
352 | if (!new) | |
f1752eec DH |
353 | return -ENOMEM; |
354 | ||
18b6e041 SH |
355 | if (clone_flags & CLONE_NEWUSER) { |
356 | ret = create_user_ns(new); | |
357 | if (ret < 0) | |
358 | goto error_put; | |
359 | } | |
360 | ||
bb952bb9 | 361 | #ifdef CONFIG_KEYS |
d84f4f99 DH |
362 | /* new threads get their own thread keyrings if their parent already |
363 | * had one */ | |
364 | if (new->thread_keyring) { | |
365 | key_put(new->thread_keyring); | |
366 | new->thread_keyring = NULL; | |
367 | if (clone_flags & CLONE_THREAD) | |
368 | install_thread_keyring_to_cred(new); | |
369 | } | |
370 | ||
3a50597d DH |
371 | /* The process keyring is only shared between the threads in a process; |
372 | * anything outside of those threads doesn't inherit. | |
373 | */ | |
d84f4f99 | 374 | if (!(clone_flags & CLONE_THREAD)) { |
3a50597d DH |
375 | key_put(new->process_keyring); |
376 | new->process_keyring = NULL; | |
bb952bb9 DH |
377 | } |
378 | #endif | |
379 | ||
d84f4f99 | 380 | atomic_inc(&new->user->processes); |
3b11a1de | 381 | p->cred = p->real_cred = get_cred(new); |
e0e81739 DH |
382 | alter_cred_subscribers(new, 2); |
383 | validate_creds(new); | |
d84f4f99 | 384 | return 0; |
18b6e041 SH |
385 | |
386 | error_put: | |
387 | put_cred(new); | |
388 | return ret; | |
d84f4f99 | 389 | } |
f1752eec | 390 | |
aa6d054e EB |
391 | static bool cred_cap_issubset(const struct cred *set, const struct cred *subset) |
392 | { | |
393 | const struct user_namespace *set_ns = set->user_ns; | |
394 | const struct user_namespace *subset_ns = subset->user_ns; | |
395 | ||
396 | /* If the two credentials are in the same user namespace see if | |
397 | * the capabilities of subset are a subset of set. | |
398 | */ | |
399 | if (set_ns == subset_ns) | |
400 | return cap_issubset(subset->cap_permitted, set->cap_permitted); | |
401 | ||
402 | /* The credentials are in a different user namespaces | |
403 | * therefore one is a subset of the other only if a set is an | |
404 | * ancestor of subset and set->euid is owner of subset or one | |
405 | * of subsets ancestors. | |
406 | */ | |
407 | for (;subset_ns != &init_user_ns; subset_ns = subset_ns->parent) { | |
408 | if ((set_ns == subset_ns->parent) && | |
409 | uid_eq(subset_ns->owner, set->euid)) | |
410 | return true; | |
411 | } | |
412 | ||
413 | return false; | |
414 | } | |
415 | ||
d84f4f99 DH |
416 | /** |
417 | * commit_creds - Install new credentials upon the current task | |
418 | * @new: The credentials to be assigned | |
419 | * | |
420 | * Install a new set of credentials to the current task, using RCU to replace | |
3b11a1de DH |
421 | * the old set. Both the objective and the subjective credentials pointers are |
422 | * updated. This function may not be called if the subjective credentials are | |
423 | * in an overridden state. | |
d84f4f99 DH |
424 | * |
425 | * This function eats the caller's reference to the new credentials. | |
426 | * | |
427 | * Always returns 0 thus allowing this function to be tail-called at the end | |
428 | * of, say, sys_setgid(). | |
429 | */ | |
430 | int commit_creds(struct cred *new) | |
431 | { | |
432 | struct task_struct *task = current; | |
e0e81739 | 433 | const struct cred *old = task->real_cred; |
d84f4f99 | 434 | |
e0e81739 DH |
435 | kdebug("commit_creds(%p{%d,%d})", new, |
436 | atomic_read(&new->usage), | |
437 | read_cred_subscribers(new)); | |
438 | ||
439 | BUG_ON(task->cred != old); | |
440 | #ifdef CONFIG_DEBUG_CREDENTIALS | |
441 | BUG_ON(read_cred_subscribers(old) < 2); | |
442 | validate_creds(old); | |
443 | validate_creds(new); | |
444 | #endif | |
d84f4f99 | 445 | BUG_ON(atomic_read(&new->usage) < 1); |
d84f4f99 | 446 | |
3b11a1de DH |
447 | get_cred(new); /* we will require a ref for the subj creds too */ |
448 | ||
d84f4f99 | 449 | /* dumpability changes */ |
078de5f7 EB |
450 | if (!uid_eq(old->euid, new->euid) || |
451 | !gid_eq(old->egid, new->egid) || | |
452 | !uid_eq(old->fsuid, new->fsuid) || | |
453 | !gid_eq(old->fsgid, new->fsgid) || | |
aa6d054e | 454 | !cred_cap_issubset(old, new)) { |
b9456371 DH |
455 | if (task->mm) |
456 | set_dumpable(task->mm, suid_dumpable); | |
d84f4f99 | 457 | task->pdeath_signal = 0; |
f6581f5b JH |
458 | /* |
459 | * If a task drops privileges and becomes nondumpable, | |
460 | * the dumpability change must become visible before | |
461 | * the credential change; otherwise, a __ptrace_may_access() | |
462 | * racing with this change may be able to attach to a task it | |
463 | * shouldn't be able to attach to (as if the task had dropped | |
464 | * privileges without becoming nondumpable). | |
465 | * Pairs with a read barrier in __ptrace_may_access(). | |
466 | */ | |
d84f4f99 | 467 | smp_wmb(); |
f1752eec DH |
468 | } |
469 | ||
d84f4f99 | 470 | /* alter the thread keyring */ |
078de5f7 | 471 | if (!uid_eq(new->fsuid, old->fsuid)) |
2e21865f | 472 | key_fsuid_changed(new); |
078de5f7 | 473 | if (!gid_eq(new->fsgid, old->fsgid)) |
2e21865f | 474 | key_fsgid_changed(new); |
d84f4f99 DH |
475 | |
476 | /* do it | |
72fa5997 VK |
477 | * RLIMIT_NPROC limits on user->processes have already been checked |
478 | * in set_user(). | |
d84f4f99 | 479 | */ |
e0e81739 | 480 | alter_cred_subscribers(new, 2); |
d84f4f99 DH |
481 | if (new->user != old->user) |
482 | atomic_inc(&new->user->processes); | |
3b11a1de | 483 | rcu_assign_pointer(task->real_cred, new); |
d84f4f99 DH |
484 | rcu_assign_pointer(task->cred, new); |
485 | if (new->user != old->user) | |
486 | atomic_dec(&old->user->processes); | |
e0e81739 | 487 | alter_cred_subscribers(old, -2); |
d84f4f99 | 488 | |
d84f4f99 | 489 | /* send notifications */ |
078de5f7 EB |
490 | if (!uid_eq(new->uid, old->uid) || |
491 | !uid_eq(new->euid, old->euid) || | |
492 | !uid_eq(new->suid, old->suid) || | |
493 | !uid_eq(new->fsuid, old->fsuid)) | |
d84f4f99 | 494 | proc_id_connector(task, PROC_EVENT_UID); |
f1752eec | 495 | |
078de5f7 EB |
496 | if (!gid_eq(new->gid, old->gid) || |
497 | !gid_eq(new->egid, old->egid) || | |
498 | !gid_eq(new->sgid, old->sgid) || | |
499 | !gid_eq(new->fsgid, old->fsgid)) | |
d84f4f99 | 500 | proc_id_connector(task, PROC_EVENT_GID); |
f1752eec | 501 | |
3b11a1de DH |
502 | /* release the old obj and subj refs both */ |
503 | put_cred(old); | |
d84f4f99 | 504 | put_cred(old); |
f1752eec DH |
505 | return 0; |
506 | } | |
d84f4f99 DH |
507 | EXPORT_SYMBOL(commit_creds); |
508 | ||
509 | /** | |
510 | * abort_creds - Discard a set of credentials and unlock the current task | |
511 | * @new: The credentials that were going to be applied | |
512 | * | |
513 | * Discard a set of credentials that were under construction and unlock the | |
514 | * current task. | |
515 | */ | |
516 | void abort_creds(struct cred *new) | |
517 | { | |
e0e81739 DH |
518 | kdebug("abort_creds(%p{%d,%d})", new, |
519 | atomic_read(&new->usage), | |
520 | read_cred_subscribers(new)); | |
521 | ||
522 | #ifdef CONFIG_DEBUG_CREDENTIALS | |
523 | BUG_ON(read_cred_subscribers(new) != 0); | |
524 | #endif | |
d84f4f99 DH |
525 | BUG_ON(atomic_read(&new->usage) < 1); |
526 | put_cred(new); | |
527 | } | |
528 | EXPORT_SYMBOL(abort_creds); | |
529 | ||
530 | /** | |
3b11a1de | 531 | * override_creds - Override the current process's subjective credentials |
d84f4f99 DH |
532 | * @new: The credentials to be assigned |
533 | * | |
3b11a1de DH |
534 | * Install a set of temporary override subjective credentials on the current |
535 | * process, returning the old set for later reversion. | |
d84f4f99 DH |
536 | */ |
537 | const struct cred *override_creds(const struct cred *new) | |
538 | { | |
539 | const struct cred *old = current->cred; | |
540 | ||
e0e81739 DH |
541 | kdebug("override_creds(%p{%d,%d})", new, |
542 | atomic_read(&new->usage), | |
543 | read_cred_subscribers(new)); | |
544 | ||
545 | validate_creds(old); | |
546 | validate_creds(new); | |
547 | get_cred(new); | |
548 | alter_cred_subscribers(new, 1); | |
549 | rcu_assign_pointer(current->cred, new); | |
550 | alter_cred_subscribers(old, -1); | |
551 | ||
552 | kdebug("override_creds() = %p{%d,%d}", old, | |
553 | atomic_read(&old->usage), | |
554 | read_cred_subscribers(old)); | |
d84f4f99 DH |
555 | return old; |
556 | } | |
557 | EXPORT_SYMBOL(override_creds); | |
558 | ||
559 | /** | |
3b11a1de | 560 | * revert_creds - Revert a temporary subjective credentials override |
d84f4f99 DH |
561 | * @old: The credentials to be restored |
562 | * | |
3b11a1de DH |
563 | * Revert a temporary set of override subjective credentials to an old set, |
564 | * discarding the override set. | |
d84f4f99 DH |
565 | */ |
566 | void revert_creds(const struct cred *old) | |
567 | { | |
568 | const struct cred *override = current->cred; | |
569 | ||
e0e81739 DH |
570 | kdebug("revert_creds(%p{%d,%d})", old, |
571 | atomic_read(&old->usage), | |
572 | read_cred_subscribers(old)); | |
573 | ||
574 | validate_creds(old); | |
575 | validate_creds(override); | |
576 | alter_cred_subscribers(old, 1); | |
d84f4f99 | 577 | rcu_assign_pointer(current->cred, old); |
e0e81739 | 578 | alter_cred_subscribers(override, -1); |
d84f4f99 DH |
579 | put_cred(override); |
580 | } | |
581 | EXPORT_SYMBOL(revert_creds); | |
582 | ||
d89b22d4 N |
583 | /** |
584 | * cred_fscmp - Compare two credentials with respect to filesystem access. | |
585 | * @a: The first credential | |
586 | * @b: The second credential | |
587 | * | |
588 | * cred_cmp() will return zero if both credentials have the same | |
589 | * fsuid, fsgid, and supplementary groups. That is, if they will both | |
590 | * provide the same access to files based on mode/uid/gid. | |
591 | * If the credentials are different, then either -1 or 1 will | |
592 | * be returned depending on whether @a comes before or after @b | |
593 | * respectively in an arbitrary, but stable, ordering of credentials. | |
594 | * | |
595 | * Return: -1, 0, or 1 depending on comparison | |
596 | */ | |
597 | int cred_fscmp(const struct cred *a, const struct cred *b) | |
598 | { | |
599 | struct group_info *ga, *gb; | |
600 | int g; | |
601 | ||
602 | if (a == b) | |
603 | return 0; | |
604 | if (uid_lt(a->fsuid, b->fsuid)) | |
605 | return -1; | |
606 | if (uid_gt(a->fsuid, b->fsuid)) | |
607 | return 1; | |
608 | ||
609 | if (gid_lt(a->fsgid, b->fsgid)) | |
610 | return -1; | |
611 | if (gid_gt(a->fsgid, b->fsgid)) | |
612 | return 1; | |
613 | ||
614 | ga = a->group_info; | |
615 | gb = b->group_info; | |
616 | if (ga == gb) | |
617 | return 0; | |
618 | if (ga == NULL) | |
619 | return -1; | |
620 | if (gb == NULL) | |
621 | return 1; | |
622 | if (ga->ngroups < gb->ngroups) | |
623 | return -1; | |
624 | if (ga->ngroups > gb->ngroups) | |
625 | return 1; | |
626 | ||
627 | for (g = 0; g < ga->ngroups; g++) { | |
628 | if (gid_lt(ga->gid[g], gb->gid[g])) | |
629 | return -1; | |
630 | if (gid_gt(ga->gid[g], gb->gid[g])) | |
631 | return 1; | |
632 | } | |
633 | return 0; | |
634 | } | |
635 | EXPORT_SYMBOL(cred_fscmp); | |
636 | ||
d84f4f99 DH |
637 | /* |
638 | * initialise the credentials stuff | |
639 | */ | |
640 | void __init cred_init(void) | |
641 | { | |
642 | /* allocate a slab in which we can store credentials */ | |
5d097056 VD |
643 | cred_jar = kmem_cache_create("cred_jar", sizeof(struct cred), 0, |
644 | SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, NULL); | |
d84f4f99 | 645 | } |
3a3b7ce9 DH |
646 | |
647 | /** | |
648 | * prepare_kernel_cred - Prepare a set of credentials for a kernel service | |
649 | * @daemon: A userspace daemon to be used as a reference | |
650 | * | |
651 | * Prepare a set of credentials for a kernel service. This can then be used to | |
652 | * override a task's own credentials so that work can be done on behalf of that | |
653 | * task that requires a different subjective context. | |
654 | * | |
655 | * @daemon is used to provide a base for the security record, but can be NULL. | |
656 | * If @daemon is supplied, then the security data will be derived from that; | |
657 | * otherwise they'll be set to 0 and no groups, full capabilities and no keys. | |
658 | * | |
659 | * The caller may change these controls afterwards if desired. | |
660 | * | |
661 | * Returns the new credentials or NULL if out of memory. | |
662 | * | |
663 | * Does not take, and does not return holding current->cred_replace_mutex. | |
664 | */ | |
665 | struct cred *prepare_kernel_cred(struct task_struct *daemon) | |
666 | { | |
667 | const struct cred *old; | |
668 | struct cred *new; | |
669 | ||
670 | new = kmem_cache_alloc(cred_jar, GFP_KERNEL); | |
671 | if (!new) | |
672 | return NULL; | |
673 | ||
e0e81739 DH |
674 | kdebug("prepare_kernel_cred() alloc %p", new); |
675 | ||
3a3b7ce9 DH |
676 | if (daemon) |
677 | old = get_task_cred(daemon); | |
678 | else | |
679 | old = get_cred(&init_cred); | |
680 | ||
e0e81739 DH |
681 | validate_creds(old); |
682 | ||
43529c97 | 683 | *new = *old; |
fb2b2a1d TH |
684 | atomic_set(&new->usage, 1); |
685 | set_cred_subscribers(new, 0); | |
3a3b7ce9 | 686 | get_uid(new->user); |
0093ccb6 | 687 | get_user_ns(new->user_ns); |
3a3b7ce9 DH |
688 | get_group_info(new->group_info); |
689 | ||
690 | #ifdef CONFIG_KEYS | |
3a50597d DH |
691 | new->session_keyring = NULL; |
692 | new->process_keyring = NULL; | |
3a3b7ce9 | 693 | new->thread_keyring = NULL; |
3a50597d | 694 | new->request_key_auth = NULL; |
3a3b7ce9 DH |
695 | new->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING; |
696 | #endif | |
697 | ||
698 | #ifdef CONFIG_SECURITY | |
699 | new->security = NULL; | |
700 | #endif | |
701 | if (security_prepare_creds(new, old, GFP_KERNEL) < 0) | |
702 | goto error; | |
703 | ||
3a3b7ce9 | 704 | put_cred(old); |
e0e81739 | 705 | validate_creds(new); |
3a3b7ce9 DH |
706 | return new; |
707 | ||
708 | error: | |
709 | put_cred(new); | |
0de33681 | 710 | put_cred(old); |
3a3b7ce9 DH |
711 | return NULL; |
712 | } | |
713 | EXPORT_SYMBOL(prepare_kernel_cred); | |
714 | ||
715 | /** | |
716 | * set_security_override - Set the security ID in a set of credentials | |
717 | * @new: The credentials to alter | |
718 | * @secid: The LSM security ID to set | |
719 | * | |
720 | * Set the LSM security ID in a set of credentials so that the subjective | |
721 | * security is overridden when an alternative set of credentials is used. | |
722 | */ | |
723 | int set_security_override(struct cred *new, u32 secid) | |
724 | { | |
725 | return security_kernel_act_as(new, secid); | |
726 | } | |
727 | EXPORT_SYMBOL(set_security_override); | |
728 | ||
729 | /** | |
730 | * set_security_override_from_ctx - Set the security ID in a set of credentials | |
731 | * @new: The credentials to alter | |
732 | * @secctx: The LSM security context to generate the security ID from. | |
733 | * | |
734 | * Set the LSM security ID in a set of credentials so that the subjective | |
735 | * security is overridden when an alternative set of credentials is used. The | |
736 | * security ID is specified in string form as a security context to be | |
737 | * interpreted by the LSM. | |
738 | */ | |
739 | int set_security_override_from_ctx(struct cred *new, const char *secctx) | |
740 | { | |
741 | u32 secid; | |
742 | int ret; | |
743 | ||
744 | ret = security_secctx_to_secid(secctx, strlen(secctx), &secid); | |
745 | if (ret < 0) | |
746 | return ret; | |
747 | ||
748 | return set_security_override(new, secid); | |
749 | } | |
750 | EXPORT_SYMBOL(set_security_override_from_ctx); | |
751 | ||
752 | /** | |
753 | * set_create_files_as - Set the LSM file create context in a set of credentials | |
754 | * @new: The credentials to alter | |
755 | * @inode: The inode to take the context from | |
756 | * | |
757 | * Change the LSM file creation context in a set of credentials to be the same | |
758 | * as the object context of the specified inode, so that the new inodes have | |
759 | * the same MAC context as that inode. | |
760 | */ | |
761 | int set_create_files_as(struct cred *new, struct inode *inode) | |
762 | { | |
5f65e5ca SF |
763 | if (!uid_valid(inode->i_uid) || !gid_valid(inode->i_gid)) |
764 | return -EINVAL; | |
3a3b7ce9 DH |
765 | new->fsuid = inode->i_uid; |
766 | new->fsgid = inode->i_gid; | |
767 | return security_kernel_create_files_as(new, inode); | |
768 | } | |
769 | EXPORT_SYMBOL(set_create_files_as); | |
e0e81739 DH |
770 | |
771 | #ifdef CONFIG_DEBUG_CREDENTIALS | |
772 | ||
74908a00 AM |
773 | bool creds_are_invalid(const struct cred *cred) |
774 | { | |
775 | if (cred->magic != CRED_MAGIC) | |
776 | return true; | |
74908a00 AM |
777 | return false; |
778 | } | |
764db03f | 779 | EXPORT_SYMBOL(creds_are_invalid); |
74908a00 | 780 | |
e0e81739 DH |
781 | /* |
782 | * dump invalid credentials | |
783 | */ | |
784 | static void dump_invalid_creds(const struct cred *cred, const char *label, | |
785 | const struct task_struct *tsk) | |
786 | { | |
787 | printk(KERN_ERR "CRED: %s credentials: %p %s%s%s\n", | |
788 | label, cred, | |
789 | cred == &init_cred ? "[init]" : "", | |
790 | cred == tsk->real_cred ? "[real]" : "", | |
791 | cred == tsk->cred ? "[eff]" : ""); | |
792 | printk(KERN_ERR "CRED: ->magic=%x, put_addr=%p\n", | |
793 | cred->magic, cred->put_addr); | |
794 | printk(KERN_ERR "CRED: ->usage=%d, subscr=%d\n", | |
795 | atomic_read(&cred->usage), | |
796 | read_cred_subscribers(cred)); | |
797 | printk(KERN_ERR "CRED: ->*uid = { %d,%d,%d,%d }\n", | |
c9235f48 EB |
798 | from_kuid_munged(&init_user_ns, cred->uid), |
799 | from_kuid_munged(&init_user_ns, cred->euid), | |
800 | from_kuid_munged(&init_user_ns, cred->suid), | |
801 | from_kuid_munged(&init_user_ns, cred->fsuid)); | |
e0e81739 | 802 | printk(KERN_ERR "CRED: ->*gid = { %d,%d,%d,%d }\n", |
c9235f48 EB |
803 | from_kgid_munged(&init_user_ns, cred->gid), |
804 | from_kgid_munged(&init_user_ns, cred->egid), | |
805 | from_kgid_munged(&init_user_ns, cred->sgid), | |
806 | from_kgid_munged(&init_user_ns, cred->fsgid)); | |
e0e81739 DH |
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 | */ | |
821 | void __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 | } | |
828 | EXPORT_SYMBOL(__invalid_creds); | |
829 | ||
830 | /* | |
831 | * check the credentials on a process | |
832 | */ | |
833 | void __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 | ||
849 | invalid_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 | } | |
860 | EXPORT_SYMBOL(__validate_process_creds); | |
861 | ||
862 | /* | |
863 | * check creds for do_exit() | |
864 | */ | |
865 | void 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 */ |