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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); | |
ee18d64c DH |
173 | } |
174 | ||
de09a977 DH |
175 | /** |
176 | * get_task_cred - Get another task's objective credentials | |
177 | * @task: The task to query | |
178 | * | |
179 | * Get the objective credentials of a task, pinning them so that they can't go | |
180 | * away. Accessing a task's credentials directly is not permitted. | |
181 | * | |
182 | * The caller must also make sure task doesn't get deleted, either by holding a | |
183 | * ref on task or by holding tasklist_lock to prevent it from being unlinked. | |
184 | */ | |
185 | const struct cred *get_task_cred(struct task_struct *task) | |
186 | { | |
187 | const struct cred *cred; | |
188 | ||
189 | rcu_read_lock(); | |
190 | ||
191 | do { | |
192 | cred = __task_cred((task)); | |
193 | BUG_ON(!cred); | |
97d0fb23 | 194 | } while (!get_cred_rcu(cred)); |
de09a977 DH |
195 | |
196 | rcu_read_unlock(); | |
197 | return cred; | |
198 | } | |
a6d8e763 | 199 | EXPORT_SYMBOL(get_task_cred); |
de09a977 | 200 | |
ee18d64c DH |
201 | /* |
202 | * Allocate blank credentials, such that the credentials can be filled in at a | |
203 | * later date without risk of ENOMEM. | |
204 | */ | |
205 | struct cred *cred_alloc_blank(void) | |
206 | { | |
207 | struct cred *new; | |
208 | ||
209 | new = kmem_cache_zalloc(cred_jar, GFP_KERNEL); | |
210 | if (!new) | |
211 | return NULL; | |
212 | ||
ee18d64c | 213 | atomic_set(&new->usage, 1); |
2edeaa34 TH |
214 | #ifdef CONFIG_DEBUG_CREDENTIALS |
215 | new->magic = CRED_MAGIC; | |
216 | #endif | |
ee18d64c DH |
217 | |
218 | if (security_cred_alloc_blank(new, GFP_KERNEL) < 0) | |
219 | goto error; | |
220 | ||
ee18d64c DH |
221 | return new; |
222 | ||
223 | error: | |
224 | abort_creds(new); | |
225 | return NULL; | |
e0e81739 DH |
226 | } |
227 | ||
d84f4f99 DH |
228 | /** |
229 | * prepare_creds - Prepare a new set of credentials for modification | |
230 | * | |
231 | * Prepare a new set of task credentials for modification. A task's creds | |
232 | * shouldn't generally be modified directly, therefore this function is used to | |
233 | * prepare a new copy, which the caller then modifies and then commits by | |
234 | * calling commit_creds(). | |
235 | * | |
3b11a1de DH |
236 | * Preparation involves making a copy of the objective creds for modification. |
237 | * | |
d84f4f99 DH |
238 | * Returns a pointer to the new creds-to-be if successful, NULL otherwise. |
239 | * | |
240 | * Call commit_creds() or abort_creds() to clean up. | |
241 | */ | |
242 | struct cred *prepare_creds(void) | |
243 | { | |
244 | struct task_struct *task = current; | |
245 | const struct cred *old; | |
246 | struct cred *new; | |
247 | ||
e0e81739 | 248 | validate_process_creds(); |
d84f4f99 DH |
249 | |
250 | new = kmem_cache_alloc(cred_jar, GFP_KERNEL); | |
251 | if (!new) | |
252 | return NULL; | |
253 | ||
e0e81739 DH |
254 | kdebug("prepare_creds() alloc %p", new); |
255 | ||
d84f4f99 DH |
256 | old = task->cred; |
257 | memcpy(new, old, sizeof(struct cred)); | |
258 | ||
259 | atomic_set(&new->usage, 1); | |
e0e81739 | 260 | set_cred_subscribers(new, 0); |
d84f4f99 DH |
261 | get_group_info(new->group_info); |
262 | get_uid(new->user); | |
0093ccb6 | 263 | get_user_ns(new->user_ns); |
d84f4f99 DH |
264 | |
265 | #ifdef CONFIG_KEYS | |
3a50597d DH |
266 | key_get(new->session_keyring); |
267 | key_get(new->process_keyring); | |
d84f4f99 DH |
268 | key_get(new->thread_keyring); |
269 | key_get(new->request_key_auth); | |
d84f4f99 DH |
270 | #endif |
271 | ||
272 | #ifdef CONFIG_SECURITY | |
273 | new->security = NULL; | |
274 | #endif | |
275 | ||
276 | if (security_prepare_creds(new, old, GFP_KERNEL) < 0) | |
277 | goto error; | |
e0e81739 | 278 | validate_creds(new); |
d84f4f99 DH |
279 | return new; |
280 | ||
281 | error: | |
282 | abort_creds(new); | |
283 | return NULL; | |
284 | } | |
285 | EXPORT_SYMBOL(prepare_creds); | |
286 | ||
a6f76f23 DH |
287 | /* |
288 | * Prepare credentials for current to perform an execve() | |
9b1bf12d | 289 | * - The caller must hold ->cred_guard_mutex |
a6f76f23 DH |
290 | */ |
291 | struct cred *prepare_exec_creds(void) | |
292 | { | |
a6f76f23 DH |
293 | struct cred *new; |
294 | ||
a6f76f23 | 295 | new = prepare_creds(); |
3a50597d | 296 | if (!new) |
a6f76f23 | 297 | return new; |
a6f76f23 DH |
298 | |
299 | #ifdef CONFIG_KEYS | |
300 | /* newly exec'd tasks don't get a thread keyring */ | |
301 | key_put(new->thread_keyring); | |
302 | new->thread_keyring = NULL; | |
303 | ||
a6f76f23 | 304 | /* inherit the session keyring; new process keyring */ |
3a50597d DH |
305 | key_put(new->process_keyring); |
306 | new->process_keyring = NULL; | |
a6f76f23 DH |
307 | #endif |
308 | ||
309 | return new; | |
310 | } | |
311 | ||
f1752eec DH |
312 | /* |
313 | * Copy credentials for the new process created by fork() | |
d84f4f99 DH |
314 | * |
315 | * We share if we can, but under some circumstances we have to generate a new | |
316 | * set. | |
3b11a1de DH |
317 | * |
318 | * The new process gets the current process's subjective credentials as its | |
319 | * objective and subjective credentials | |
f1752eec DH |
320 | */ |
321 | int copy_creds(struct task_struct *p, unsigned long clone_flags) | |
322 | { | |
d84f4f99 | 323 | struct cred *new; |
18b6e041 | 324 | int ret; |
d84f4f99 | 325 | |
d84f4f99 DH |
326 | if ( |
327 | #ifdef CONFIG_KEYS | |
328 | !p->cred->thread_keyring && | |
329 | #endif | |
330 | clone_flags & CLONE_THREAD | |
331 | ) { | |
3b11a1de | 332 | p->real_cred = get_cred(p->cred); |
d84f4f99 | 333 | get_cred(p->cred); |
e0e81739 DH |
334 | alter_cred_subscribers(p->cred, 2); |
335 | kdebug("share_creds(%p{%d,%d})", | |
336 | p->cred, atomic_read(&p->cred->usage), | |
337 | read_cred_subscribers(p->cred)); | |
d84f4f99 DH |
338 | atomic_inc(&p->cred->user->processes); |
339 | return 0; | |
340 | } | |
341 | ||
342 | new = prepare_creds(); | |
343 | if (!new) | |
f1752eec DH |
344 | return -ENOMEM; |
345 | ||
18b6e041 SH |
346 | if (clone_flags & CLONE_NEWUSER) { |
347 | ret = create_user_ns(new); | |
348 | if (ret < 0) | |
349 | goto error_put; | |
350 | } | |
351 | ||
bb952bb9 | 352 | #ifdef CONFIG_KEYS |
d84f4f99 DH |
353 | /* new threads get their own thread keyrings if their parent already |
354 | * had one */ | |
355 | if (new->thread_keyring) { | |
356 | key_put(new->thread_keyring); | |
357 | new->thread_keyring = NULL; | |
358 | if (clone_flags & CLONE_THREAD) | |
359 | install_thread_keyring_to_cred(new); | |
360 | } | |
361 | ||
3a50597d DH |
362 | /* The process keyring is only shared between the threads in a process; |
363 | * anything outside of those threads doesn't inherit. | |
364 | */ | |
d84f4f99 | 365 | if (!(clone_flags & CLONE_THREAD)) { |
3a50597d DH |
366 | key_put(new->process_keyring); |
367 | new->process_keyring = NULL; | |
bb952bb9 DH |
368 | } |
369 | #endif | |
370 | ||
d84f4f99 | 371 | atomic_inc(&new->user->processes); |
3b11a1de | 372 | p->cred = p->real_cred = get_cred(new); |
e0e81739 DH |
373 | alter_cred_subscribers(new, 2); |
374 | validate_creds(new); | |
d84f4f99 | 375 | return 0; |
18b6e041 SH |
376 | |
377 | error_put: | |
378 | put_cred(new); | |
379 | return ret; | |
d84f4f99 | 380 | } |
f1752eec | 381 | |
aa6d054e EB |
382 | static bool cred_cap_issubset(const struct cred *set, const struct cred *subset) |
383 | { | |
384 | const struct user_namespace *set_ns = set->user_ns; | |
385 | const struct user_namespace *subset_ns = subset->user_ns; | |
386 | ||
387 | /* If the two credentials are in the same user namespace see if | |
388 | * the capabilities of subset are a subset of set. | |
389 | */ | |
390 | if (set_ns == subset_ns) | |
391 | return cap_issubset(subset->cap_permitted, set->cap_permitted); | |
392 | ||
393 | /* The credentials are in a different user namespaces | |
394 | * therefore one is a subset of the other only if a set is an | |
395 | * ancestor of subset and set->euid is owner of subset or one | |
396 | * of subsets ancestors. | |
397 | */ | |
398 | for (;subset_ns != &init_user_ns; subset_ns = subset_ns->parent) { | |
399 | if ((set_ns == subset_ns->parent) && | |
400 | uid_eq(subset_ns->owner, set->euid)) | |
401 | return true; | |
402 | } | |
403 | ||
404 | return false; | |
405 | } | |
406 | ||
d84f4f99 DH |
407 | /** |
408 | * commit_creds - Install new credentials upon the current task | |
409 | * @new: The credentials to be assigned | |
410 | * | |
411 | * Install a new set of credentials to the current task, using RCU to replace | |
3b11a1de DH |
412 | * the old set. Both the objective and the subjective credentials pointers are |
413 | * updated. This function may not be called if the subjective credentials are | |
414 | * in an overridden state. | |
d84f4f99 DH |
415 | * |
416 | * This function eats the caller's reference to the new credentials. | |
417 | * | |
418 | * Always returns 0 thus allowing this function to be tail-called at the end | |
419 | * of, say, sys_setgid(). | |
420 | */ | |
421 | int commit_creds(struct cred *new) | |
422 | { | |
423 | struct task_struct *task = current; | |
e0e81739 | 424 | const struct cred *old = task->real_cred; |
d84f4f99 | 425 | |
e0e81739 DH |
426 | kdebug("commit_creds(%p{%d,%d})", new, |
427 | atomic_read(&new->usage), | |
428 | read_cred_subscribers(new)); | |
429 | ||
430 | BUG_ON(task->cred != old); | |
431 | #ifdef CONFIG_DEBUG_CREDENTIALS | |
432 | BUG_ON(read_cred_subscribers(old) < 2); | |
433 | validate_creds(old); | |
434 | validate_creds(new); | |
435 | #endif | |
d84f4f99 | 436 | BUG_ON(atomic_read(&new->usage) < 1); |
d84f4f99 | 437 | |
3b11a1de DH |
438 | get_cred(new); /* we will require a ref for the subj creds too */ |
439 | ||
d84f4f99 | 440 | /* dumpability changes */ |
078de5f7 EB |
441 | if (!uid_eq(old->euid, new->euid) || |
442 | !gid_eq(old->egid, new->egid) || | |
443 | !uid_eq(old->fsuid, new->fsuid) || | |
444 | !gid_eq(old->fsgid, new->fsgid) || | |
aa6d054e | 445 | !cred_cap_issubset(old, new)) { |
b9456371 DH |
446 | if (task->mm) |
447 | set_dumpable(task->mm, suid_dumpable); | |
d84f4f99 | 448 | task->pdeath_signal = 0; |
f6581f5b JH |
449 | /* |
450 | * If a task drops privileges and becomes nondumpable, | |
451 | * the dumpability change must become visible before | |
452 | * the credential change; otherwise, a __ptrace_may_access() | |
453 | * racing with this change may be able to attach to a task it | |
454 | * shouldn't be able to attach to (as if the task had dropped | |
455 | * privileges without becoming nondumpable). | |
456 | * Pairs with a read barrier in __ptrace_may_access(). | |
457 | */ | |
d84f4f99 | 458 | smp_wmb(); |
f1752eec DH |
459 | } |
460 | ||
d84f4f99 | 461 | /* alter the thread keyring */ |
078de5f7 | 462 | if (!uid_eq(new->fsuid, old->fsuid)) |
d84f4f99 | 463 | key_fsuid_changed(task); |
078de5f7 | 464 | if (!gid_eq(new->fsgid, old->fsgid)) |
d84f4f99 DH |
465 | key_fsgid_changed(task); |
466 | ||
467 | /* do it | |
72fa5997 VK |
468 | * RLIMIT_NPROC limits on user->processes have already been checked |
469 | * in set_user(). | |
d84f4f99 | 470 | */ |
e0e81739 | 471 | alter_cred_subscribers(new, 2); |
d84f4f99 DH |
472 | if (new->user != old->user) |
473 | atomic_inc(&new->user->processes); | |
3b11a1de | 474 | rcu_assign_pointer(task->real_cred, new); |
d84f4f99 DH |
475 | rcu_assign_pointer(task->cred, new); |
476 | if (new->user != old->user) | |
477 | atomic_dec(&old->user->processes); | |
e0e81739 | 478 | alter_cred_subscribers(old, -2); |
d84f4f99 | 479 | |
d84f4f99 | 480 | /* send notifications */ |
078de5f7 EB |
481 | if (!uid_eq(new->uid, old->uid) || |
482 | !uid_eq(new->euid, old->euid) || | |
483 | !uid_eq(new->suid, old->suid) || | |
484 | !uid_eq(new->fsuid, old->fsuid)) | |
d84f4f99 | 485 | proc_id_connector(task, PROC_EVENT_UID); |
f1752eec | 486 | |
078de5f7 EB |
487 | if (!gid_eq(new->gid, old->gid) || |
488 | !gid_eq(new->egid, old->egid) || | |
489 | !gid_eq(new->sgid, old->sgid) || | |
490 | !gid_eq(new->fsgid, old->fsgid)) | |
d84f4f99 | 491 | proc_id_connector(task, PROC_EVENT_GID); |
f1752eec | 492 | |
3b11a1de DH |
493 | /* release the old obj and subj refs both */ |
494 | put_cred(old); | |
d84f4f99 | 495 | put_cred(old); |
f1752eec DH |
496 | return 0; |
497 | } | |
d84f4f99 DH |
498 | EXPORT_SYMBOL(commit_creds); |
499 | ||
500 | /** | |
501 | * abort_creds - Discard a set of credentials and unlock the current task | |
502 | * @new: The credentials that were going to be applied | |
503 | * | |
504 | * Discard a set of credentials that were under construction and unlock the | |
505 | * current task. | |
506 | */ | |
507 | void abort_creds(struct cred *new) | |
508 | { | |
e0e81739 DH |
509 | kdebug("abort_creds(%p{%d,%d})", new, |
510 | atomic_read(&new->usage), | |
511 | read_cred_subscribers(new)); | |
512 | ||
513 | #ifdef CONFIG_DEBUG_CREDENTIALS | |
514 | BUG_ON(read_cred_subscribers(new) != 0); | |
515 | #endif | |
d84f4f99 DH |
516 | BUG_ON(atomic_read(&new->usage) < 1); |
517 | put_cred(new); | |
518 | } | |
519 | EXPORT_SYMBOL(abort_creds); | |
520 | ||
521 | /** | |
3b11a1de | 522 | * override_creds - Override the current process's subjective credentials |
d84f4f99 DH |
523 | * @new: The credentials to be assigned |
524 | * | |
3b11a1de DH |
525 | * Install a set of temporary override subjective credentials on the current |
526 | * process, returning the old set for later reversion. | |
d84f4f99 DH |
527 | */ |
528 | const struct cred *override_creds(const struct cred *new) | |
529 | { | |
530 | const struct cred *old = current->cred; | |
531 | ||
e0e81739 DH |
532 | kdebug("override_creds(%p{%d,%d})", new, |
533 | atomic_read(&new->usage), | |
534 | read_cred_subscribers(new)); | |
535 | ||
536 | validate_creds(old); | |
537 | validate_creds(new); | |
538 | get_cred(new); | |
539 | alter_cred_subscribers(new, 1); | |
540 | rcu_assign_pointer(current->cred, new); | |
541 | alter_cred_subscribers(old, -1); | |
542 | ||
543 | kdebug("override_creds() = %p{%d,%d}", old, | |
544 | atomic_read(&old->usage), | |
545 | read_cred_subscribers(old)); | |
d84f4f99 DH |
546 | return old; |
547 | } | |
548 | EXPORT_SYMBOL(override_creds); | |
549 | ||
550 | /** | |
3b11a1de | 551 | * revert_creds - Revert a temporary subjective credentials override |
d84f4f99 DH |
552 | * @old: The credentials to be restored |
553 | * | |
3b11a1de DH |
554 | * Revert a temporary set of override subjective credentials to an old set, |
555 | * discarding the override set. | |
d84f4f99 DH |
556 | */ |
557 | void revert_creds(const struct cred *old) | |
558 | { | |
559 | const struct cred *override = current->cred; | |
560 | ||
e0e81739 DH |
561 | kdebug("revert_creds(%p{%d,%d})", old, |
562 | atomic_read(&old->usage), | |
563 | read_cred_subscribers(old)); | |
564 | ||
565 | validate_creds(old); | |
566 | validate_creds(override); | |
567 | alter_cred_subscribers(old, 1); | |
d84f4f99 | 568 | rcu_assign_pointer(current->cred, old); |
e0e81739 | 569 | alter_cred_subscribers(override, -1); |
d84f4f99 DH |
570 | put_cred(override); |
571 | } | |
572 | EXPORT_SYMBOL(revert_creds); | |
573 | ||
d89b22d4 N |
574 | /** |
575 | * cred_fscmp - Compare two credentials with respect to filesystem access. | |
576 | * @a: The first credential | |
577 | * @b: The second credential | |
578 | * | |
579 | * cred_cmp() will return zero if both credentials have the same | |
580 | * fsuid, fsgid, and supplementary groups. That is, if they will both | |
581 | * provide the same access to files based on mode/uid/gid. | |
582 | * If the credentials are different, then either -1 or 1 will | |
583 | * be returned depending on whether @a comes before or after @b | |
584 | * respectively in an arbitrary, but stable, ordering of credentials. | |
585 | * | |
586 | * Return: -1, 0, or 1 depending on comparison | |
587 | */ | |
588 | int cred_fscmp(const struct cred *a, const struct cred *b) | |
589 | { | |
590 | struct group_info *ga, *gb; | |
591 | int g; | |
592 | ||
593 | if (a == b) | |
594 | return 0; | |
595 | if (uid_lt(a->fsuid, b->fsuid)) | |
596 | return -1; | |
597 | if (uid_gt(a->fsuid, b->fsuid)) | |
598 | return 1; | |
599 | ||
600 | if (gid_lt(a->fsgid, b->fsgid)) | |
601 | return -1; | |
602 | if (gid_gt(a->fsgid, b->fsgid)) | |
603 | return 1; | |
604 | ||
605 | ga = a->group_info; | |
606 | gb = b->group_info; | |
607 | if (ga == gb) | |
608 | return 0; | |
609 | if (ga == NULL) | |
610 | return -1; | |
611 | if (gb == NULL) | |
612 | return 1; | |
613 | if (ga->ngroups < gb->ngroups) | |
614 | return -1; | |
615 | if (ga->ngroups > gb->ngroups) | |
616 | return 1; | |
617 | ||
618 | for (g = 0; g < ga->ngroups; g++) { | |
619 | if (gid_lt(ga->gid[g], gb->gid[g])) | |
620 | return -1; | |
621 | if (gid_gt(ga->gid[g], gb->gid[g])) | |
622 | return 1; | |
623 | } | |
624 | return 0; | |
625 | } | |
626 | EXPORT_SYMBOL(cred_fscmp); | |
627 | ||
d84f4f99 DH |
628 | /* |
629 | * initialise the credentials stuff | |
630 | */ | |
631 | void __init cred_init(void) | |
632 | { | |
633 | /* allocate a slab in which we can store credentials */ | |
5d097056 VD |
634 | cred_jar = kmem_cache_create("cred_jar", sizeof(struct cred), 0, |
635 | SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, NULL); | |
d84f4f99 | 636 | } |
3a3b7ce9 DH |
637 | |
638 | /** | |
639 | * prepare_kernel_cred - Prepare a set of credentials for a kernel service | |
640 | * @daemon: A userspace daemon to be used as a reference | |
641 | * | |
642 | * Prepare a set of credentials for a kernel service. This can then be used to | |
643 | * override a task's own credentials so that work can be done on behalf of that | |
644 | * task that requires a different subjective context. | |
645 | * | |
646 | * @daemon is used to provide a base for the security record, but can be NULL. | |
647 | * If @daemon is supplied, then the security data will be derived from that; | |
648 | * otherwise they'll be set to 0 and no groups, full capabilities and no keys. | |
649 | * | |
650 | * The caller may change these controls afterwards if desired. | |
651 | * | |
652 | * Returns the new credentials or NULL if out of memory. | |
653 | * | |
654 | * Does not take, and does not return holding current->cred_replace_mutex. | |
655 | */ | |
656 | struct cred *prepare_kernel_cred(struct task_struct *daemon) | |
657 | { | |
658 | const struct cred *old; | |
659 | struct cred *new; | |
660 | ||
661 | new = kmem_cache_alloc(cred_jar, GFP_KERNEL); | |
662 | if (!new) | |
663 | return NULL; | |
664 | ||
e0e81739 DH |
665 | kdebug("prepare_kernel_cred() alloc %p", new); |
666 | ||
3a3b7ce9 DH |
667 | if (daemon) |
668 | old = get_task_cred(daemon); | |
669 | else | |
670 | old = get_cred(&init_cred); | |
671 | ||
e0e81739 DH |
672 | validate_creds(old); |
673 | ||
43529c97 | 674 | *new = *old; |
fb2b2a1d TH |
675 | atomic_set(&new->usage, 1); |
676 | set_cred_subscribers(new, 0); | |
3a3b7ce9 | 677 | get_uid(new->user); |
0093ccb6 | 678 | get_user_ns(new->user_ns); |
3a3b7ce9 DH |
679 | get_group_info(new->group_info); |
680 | ||
681 | #ifdef CONFIG_KEYS | |
3a50597d DH |
682 | new->session_keyring = NULL; |
683 | new->process_keyring = NULL; | |
3a3b7ce9 | 684 | new->thread_keyring = NULL; |
3a50597d | 685 | new->request_key_auth = NULL; |
3a3b7ce9 DH |
686 | new->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING; |
687 | #endif | |
688 | ||
689 | #ifdef CONFIG_SECURITY | |
690 | new->security = NULL; | |
691 | #endif | |
692 | if (security_prepare_creds(new, old, GFP_KERNEL) < 0) | |
693 | goto error; | |
694 | ||
3a3b7ce9 | 695 | put_cred(old); |
e0e81739 | 696 | validate_creds(new); |
3a3b7ce9 DH |
697 | return new; |
698 | ||
699 | error: | |
700 | put_cred(new); | |
0de33681 | 701 | put_cred(old); |
3a3b7ce9 DH |
702 | return NULL; |
703 | } | |
704 | EXPORT_SYMBOL(prepare_kernel_cred); | |
705 | ||
706 | /** | |
707 | * set_security_override - Set the security ID in a set of credentials | |
708 | * @new: The credentials to alter | |
709 | * @secid: The LSM security ID to set | |
710 | * | |
711 | * Set the LSM security ID in a set of credentials so that the subjective | |
712 | * security is overridden when an alternative set of credentials is used. | |
713 | */ | |
714 | int set_security_override(struct cred *new, u32 secid) | |
715 | { | |
716 | return security_kernel_act_as(new, secid); | |
717 | } | |
718 | EXPORT_SYMBOL(set_security_override); | |
719 | ||
720 | /** | |
721 | * set_security_override_from_ctx - Set the security ID in a set of credentials | |
722 | * @new: The credentials to alter | |
723 | * @secctx: The LSM security context to generate the security ID from. | |
724 | * | |
725 | * Set the LSM security ID in a set of credentials so that the subjective | |
726 | * security is overridden when an alternative set of credentials is used. The | |
727 | * security ID is specified in string form as a security context to be | |
728 | * interpreted by the LSM. | |
729 | */ | |
730 | int set_security_override_from_ctx(struct cred *new, const char *secctx) | |
731 | { | |
732 | u32 secid; | |
733 | int ret; | |
734 | ||
735 | ret = security_secctx_to_secid(secctx, strlen(secctx), &secid); | |
736 | if (ret < 0) | |
737 | return ret; | |
738 | ||
739 | return set_security_override(new, secid); | |
740 | } | |
741 | EXPORT_SYMBOL(set_security_override_from_ctx); | |
742 | ||
743 | /** | |
744 | * set_create_files_as - Set the LSM file create context in a set of credentials | |
745 | * @new: The credentials to alter | |
746 | * @inode: The inode to take the context from | |
747 | * | |
748 | * Change the LSM file creation context in a set of credentials to be the same | |
749 | * as the object context of the specified inode, so that the new inodes have | |
750 | * the same MAC context as that inode. | |
751 | */ | |
752 | int set_create_files_as(struct cred *new, struct inode *inode) | |
753 | { | |
5f65e5ca SF |
754 | if (!uid_valid(inode->i_uid) || !gid_valid(inode->i_gid)) |
755 | return -EINVAL; | |
3a3b7ce9 DH |
756 | new->fsuid = inode->i_uid; |
757 | new->fsgid = inode->i_gid; | |
758 | return security_kernel_create_files_as(new, inode); | |
759 | } | |
760 | EXPORT_SYMBOL(set_create_files_as); | |
e0e81739 DH |
761 | |
762 | #ifdef CONFIG_DEBUG_CREDENTIALS | |
763 | ||
74908a00 AM |
764 | bool creds_are_invalid(const struct cred *cred) |
765 | { | |
766 | if (cred->magic != CRED_MAGIC) | |
767 | return true; | |
74908a00 AM |
768 | return false; |
769 | } | |
764db03f | 770 | EXPORT_SYMBOL(creds_are_invalid); |
74908a00 | 771 | |
e0e81739 DH |
772 | /* |
773 | * dump invalid credentials | |
774 | */ | |
775 | static void dump_invalid_creds(const struct cred *cred, const char *label, | |
776 | const struct task_struct *tsk) | |
777 | { | |
778 | printk(KERN_ERR "CRED: %s credentials: %p %s%s%s\n", | |
779 | label, cred, | |
780 | cred == &init_cred ? "[init]" : "", | |
781 | cred == tsk->real_cred ? "[real]" : "", | |
782 | cred == tsk->cred ? "[eff]" : ""); | |
783 | printk(KERN_ERR "CRED: ->magic=%x, put_addr=%p\n", | |
784 | cred->magic, cred->put_addr); | |
785 | printk(KERN_ERR "CRED: ->usage=%d, subscr=%d\n", | |
786 | atomic_read(&cred->usage), | |
787 | read_cred_subscribers(cred)); | |
788 | printk(KERN_ERR "CRED: ->*uid = { %d,%d,%d,%d }\n", | |
c9235f48 EB |
789 | from_kuid_munged(&init_user_ns, cred->uid), |
790 | from_kuid_munged(&init_user_ns, cred->euid), | |
791 | from_kuid_munged(&init_user_ns, cred->suid), | |
792 | from_kuid_munged(&init_user_ns, cred->fsuid)); | |
e0e81739 | 793 | printk(KERN_ERR "CRED: ->*gid = { %d,%d,%d,%d }\n", |
c9235f48 EB |
794 | from_kgid_munged(&init_user_ns, cred->gid), |
795 | from_kgid_munged(&init_user_ns, cred->egid), | |
796 | from_kgid_munged(&init_user_ns, cred->sgid), | |
797 | from_kgid_munged(&init_user_ns, cred->fsgid)); | |
e0e81739 DH |
798 | #ifdef CONFIG_SECURITY |
799 | printk(KERN_ERR "CRED: ->security is %p\n", cred->security); | |
800 | if ((unsigned long) cred->security >= PAGE_SIZE && | |
801 | (((unsigned long) cred->security & 0xffffff00) != | |
802 | (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8))) | |
803 | printk(KERN_ERR "CRED: ->security {%x, %x}\n", | |
804 | ((u32*)cred->security)[0], | |
805 | ((u32*)cred->security)[1]); | |
806 | #endif | |
807 | } | |
808 | ||
809 | /* | |
810 | * report use of invalid credentials | |
811 | */ | |
812 | void __invalid_creds(const struct cred *cred, const char *file, unsigned line) | |
813 | { | |
814 | printk(KERN_ERR "CRED: Invalid credentials\n"); | |
815 | printk(KERN_ERR "CRED: At %s:%u\n", file, line); | |
816 | dump_invalid_creds(cred, "Specified", current); | |
817 | BUG(); | |
818 | } | |
819 | EXPORT_SYMBOL(__invalid_creds); | |
820 | ||
821 | /* | |
822 | * check the credentials on a process | |
823 | */ | |
824 | void __validate_process_creds(struct task_struct *tsk, | |
825 | const char *file, unsigned line) | |
826 | { | |
827 | if (tsk->cred == tsk->real_cred) { | |
828 | if (unlikely(read_cred_subscribers(tsk->cred) < 2 || | |
829 | creds_are_invalid(tsk->cred))) | |
830 | goto invalid_creds; | |
831 | } else { | |
832 | if (unlikely(read_cred_subscribers(tsk->real_cred) < 1 || | |
833 | read_cred_subscribers(tsk->cred) < 1 || | |
834 | creds_are_invalid(tsk->real_cred) || | |
835 | creds_are_invalid(tsk->cred))) | |
836 | goto invalid_creds; | |
837 | } | |
838 | return; | |
839 | ||
840 | invalid_creds: | |
841 | printk(KERN_ERR "CRED: Invalid process credentials\n"); | |
842 | printk(KERN_ERR "CRED: At %s:%u\n", file, line); | |
843 | ||
844 | dump_invalid_creds(tsk->real_cred, "Real", tsk); | |
845 | if (tsk->cred != tsk->real_cred) | |
846 | dump_invalid_creds(tsk->cred, "Effective", tsk); | |
847 | else | |
848 | printk(KERN_ERR "CRED: Effective creds == Real creds\n"); | |
849 | BUG(); | |
850 | } | |
851 | EXPORT_SYMBOL(__validate_process_creds); | |
852 | ||
853 | /* | |
854 | * check creds for do_exit() | |
855 | */ | |
856 | void validate_creds_for_do_exit(struct task_struct *tsk) | |
857 | { | |
858 | kdebug("validate_creds_for_do_exit(%p,%p{%d,%d})", | |
859 | tsk->real_cred, tsk->cred, | |
860 | atomic_read(&tsk->cred->usage), | |
861 | read_cred_subscribers(tsk->cred)); | |
862 | ||
863 | __validate_process_creds(tsk, __FILE__, __LINE__); | |
864 | } | |
865 | ||
866 | #endif /* CONFIG_DEBUG_CREDENTIALS */ |