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1// SPDX-License-Identifier: GPL-2.0-or-later
2/* AFS security handling
3 *
4 * Copyright (C) 2007, 2017 Red Hat, Inc. All Rights Reserved.
5 * Written by David Howells ([email protected])
6 */
7
8#include <linux/init.h>
9#include <linux/slab.h>
10#include <linux/fs.h>
11#include <linux/ctype.h>
12#include <linux/sched.h>
13#include <linux/hashtable.h>
14#include <keys/rxrpc-type.h>
15#include "internal.h"
16
17static DEFINE_HASHTABLE(afs_permits_cache, 10);
18static DEFINE_SPINLOCK(afs_permits_lock);
19static DEFINE_MUTEX(afs_key_lock);
20
21/*
22 * Allocate a key to use as a placeholder for anonymous user security.
23 */
24static int afs_alloc_anon_key(struct afs_cell *cell)
25{
26 struct key *key;
27
28 mutex_lock(&afs_key_lock);
29 key = cell->anonymous_key;
30 if (!key) {
31 key = rxrpc_get_null_key(cell->key_desc);
32 if (!IS_ERR(key))
33 cell->anonymous_key = key;
34 }
35 mutex_unlock(&afs_key_lock);
36
37 if (IS_ERR(key))
38 return PTR_ERR(key);
39
40 _debug("anon key %p{%x}",
41 cell->anonymous_key, key_serial(cell->anonymous_key));
42 return 0;
43}
44
45/*
46 * get a key
47 */
48struct key *afs_request_key(struct afs_cell *cell)
49{
50 struct key *key;
51 int ret;
52
53 _enter("{%s}", cell->key_desc);
54
55 _debug("key %s", cell->key_desc);
56 key = request_key_net(&key_type_rxrpc, cell->key_desc,
57 cell->net->net, NULL);
58 if (IS_ERR(key)) {
59 if (PTR_ERR(key) != -ENOKEY) {
60 _leave(" = %ld", PTR_ERR(key));
61 return key;
62 }
63
64 if (!cell->anonymous_key) {
65 ret = afs_alloc_anon_key(cell);
66 if (ret < 0)
67 return ERR_PTR(ret);
68 }
69
70 /* act as anonymous user */
71 _leave(" = {%x} [anon]", key_serial(cell->anonymous_key));
72 return key_get(cell->anonymous_key);
73 } else {
74 /* act as authorised user */
75 _leave(" = {%x} [auth]", key_serial(key));
76 return key;
77 }
78}
79
80/*
81 * Get a key when pathwalk is in rcuwalk mode.
82 */
83struct key *afs_request_key_rcu(struct afs_cell *cell)
84{
85 struct key *key;
86
87 _enter("{%s}", cell->key_desc);
88
89 _debug("key %s", cell->key_desc);
90 key = request_key_net_rcu(&key_type_rxrpc, cell->key_desc,
91 cell->net->net);
92 if (IS_ERR(key)) {
93 if (PTR_ERR(key) != -ENOKEY) {
94 _leave(" = %ld", PTR_ERR(key));
95 return key;
96 }
97
98 /* act as anonymous user */
99 if (!cell->anonymous_key)
100 return NULL; /* Need to allocate */
101 _leave(" = {%x} [anon]", key_serial(cell->anonymous_key));
102 return key_get(cell->anonymous_key);
103 } else {
104 /* act as authorised user */
105 _leave(" = {%x} [auth]", key_serial(key));
106 return key;
107 }
108}
109
110/*
111 * Dispose of a list of permits.
112 */
113static void afs_permits_rcu(struct rcu_head *rcu)
114{
115 struct afs_permits *permits =
116 container_of(rcu, struct afs_permits, rcu);
117 int i;
118
119 for (i = 0; i < permits->nr_permits; i++)
120 key_put(permits->permits[i].key);
121 kfree(permits);
122}
123
124/*
125 * Discard a permission cache.
126 */
127void afs_put_permits(struct afs_permits *permits)
128{
129 if (permits && refcount_dec_and_test(&permits->usage)) {
130 spin_lock(&afs_permits_lock);
131 hash_del_rcu(&permits->hash_node);
132 spin_unlock(&afs_permits_lock);
133 call_rcu(&permits->rcu, afs_permits_rcu);
134 }
135}
136
137/*
138 * Clear a permit cache on callback break.
139 */
140void afs_clear_permits(struct afs_vnode *vnode)
141{
142 struct afs_permits *permits;
143
144 spin_lock(&vnode->lock);
145 permits = rcu_dereference_protected(vnode->permit_cache,
146 lockdep_is_held(&vnode->lock));
147 RCU_INIT_POINTER(vnode->permit_cache, NULL);
148 spin_unlock(&vnode->lock);
149
150 afs_put_permits(permits);
151}
152
153/*
154 * Hash a list of permits. Use simple addition to make it easy to add an extra
155 * one at an as-yet indeterminate position in the list.
156 */
157static void afs_hash_permits(struct afs_permits *permits)
158{
159 unsigned long h = permits->nr_permits;
160 int i;
161
162 for (i = 0; i < permits->nr_permits; i++) {
163 h += (unsigned long)permits->permits[i].key / sizeof(void *);
164 h += permits->permits[i].access;
165 }
166
167 permits->h = h;
168}
169
170/*
171 * Cache the CallerAccess result obtained from doing a fileserver operation
172 * that returned a vnode status for a particular key. If a callback break
173 * occurs whilst the operation was in progress then we have to ditch the cache
174 * as the ACL *may* have changed.
175 */
176void afs_cache_permit(struct afs_vnode *vnode, struct key *key,
177 unsigned int cb_break, struct afs_status_cb *scb)
178{
179 struct afs_permits *permits, *xpermits, *replacement, *zap, *new = NULL;
180 afs_access_t caller_access = scb->status.caller_access;
181 size_t size = 0;
182 bool changed = false;
183 int i, j;
184
185 _enter("{%llx:%llu},%x,%x",
186 vnode->fid.vid, vnode->fid.vnode, key_serial(key), caller_access);
187
188 rcu_read_lock();
189
190 /* Check for the common case first: We got back the same access as last
191 * time we tried and already have it recorded.
192 */
193 permits = rcu_dereference(vnode->permit_cache);
194 if (permits) {
195 if (!permits->invalidated) {
196 for (i = 0; i < permits->nr_permits; i++) {
197 if (permits->permits[i].key < key)
198 continue;
199 if (permits->permits[i].key > key)
200 break;
201 if (permits->permits[i].access != caller_access) {
202 changed = true;
203 break;
204 }
205
206 if (afs_cb_is_broken(cb_break, vnode)) {
207 changed = true;
208 break;
209 }
210
211 /* The cache is still good. */
212 rcu_read_unlock();
213 return;
214 }
215 }
216
217 changed |= permits->invalidated;
218 size = permits->nr_permits;
219
220 /* If this set of permits is now wrong, clear the permits
221 * pointer so that no one tries to use the stale information.
222 */
223 if (changed) {
224 spin_lock(&vnode->lock);
225 if (permits != rcu_access_pointer(vnode->permit_cache))
226 goto someone_else_changed_it_unlock;
227 RCU_INIT_POINTER(vnode->permit_cache, NULL);
228 spin_unlock(&vnode->lock);
229
230 afs_put_permits(permits);
231 permits = NULL;
232 size = 0;
233 }
234 }
235
236 if (afs_cb_is_broken(cb_break, vnode))
237 goto someone_else_changed_it;
238
239 /* We need a ref on any permits list we want to copy as we'll have to
240 * drop the lock to do memory allocation.
241 */
242 if (permits && !refcount_inc_not_zero(&permits->usage))
243 goto someone_else_changed_it;
244
245 rcu_read_unlock();
246
247 /* Speculatively create a new list with the revised permission set. We
248 * discard this if we find an extant match already in the hash, but
249 * it's easier to compare with memcmp this way.
250 *
251 * We fill in the key pointers at this time, but we don't get the refs
252 * yet.
253 */
254 size++;
255 new = kzalloc_flex(*new, permits, size, GFP_NOFS);
256 if (!new)
257 goto out_put;
258
259 refcount_set(&new->usage, 1);
260 new->nr_permits = size;
261 i = j = 0;
262 if (permits) {
263 for (i = 0; i < permits->nr_permits; i++) {
264 if (j == i && permits->permits[i].key > key) {
265 new->permits[j].key = key;
266 new->permits[j].access = caller_access;
267 j++;
268 }
269 new->permits[j].key = permits->permits[i].key;
270 new->permits[j].access = permits->permits[i].access;
271 j++;
272 }
273 }
274
275 if (j == i) {
276 new->permits[j].key = key;
277 new->permits[j].access = caller_access;
278 }
279
280 afs_hash_permits(new);
281
282 /* Now see if the permit list we want is actually already available */
283 spin_lock(&afs_permits_lock);
284
285 hash_for_each_possible(afs_permits_cache, xpermits, hash_node, new->h) {
286 if (xpermits->h != new->h ||
287 xpermits->invalidated ||
288 xpermits->nr_permits != new->nr_permits ||
289 memcmp(xpermits->permits, new->permits,
290 new->nr_permits * sizeof(struct afs_permit)) != 0)
291 continue;
292
293 if (refcount_inc_not_zero(&xpermits->usage)) {
294 replacement = xpermits;
295 goto found;
296 }
297
298 break;
299 }
300
301 for (i = 0; i < new->nr_permits; i++)
302 key_get(new->permits[i].key);
303 hash_add_rcu(afs_permits_cache, &new->hash_node, new->h);
304 replacement = new;
305 new = NULL;
306
307found:
308 spin_unlock(&afs_permits_lock);
309
310 kfree(new);
311
312 rcu_read_lock();
313 spin_lock(&vnode->lock);
314 zap = rcu_access_pointer(vnode->permit_cache);
315 if (!afs_cb_is_broken(cb_break, vnode) && zap == permits)
316 rcu_assign_pointer(vnode->permit_cache, replacement);
317 else
318 zap = replacement;
319 spin_unlock(&vnode->lock);
320 rcu_read_unlock();
321 afs_put_permits(zap);
322out_put:
323 afs_put_permits(permits);
324 return;
325
326someone_else_changed_it_unlock:
327 spin_unlock(&vnode->lock);
328someone_else_changed_it:
329 /* Someone else changed the cache under us - don't recheck at this
330 * time.
331 */
332 rcu_read_unlock();
333 return;
334}
335
336static bool afs_check_permit_rcu(struct afs_vnode *vnode, struct key *key,
337 afs_access_t *_access)
338{
339 const struct afs_permits *permits;
340 int i;
341
342 _enter("{%llx:%llu},%x",
343 vnode->fid.vid, vnode->fid.vnode, key_serial(key));
344
345 /* check the permits to see if we've got one yet */
346 if (key == vnode->volume->cell->anonymous_key) {
347 *_access = vnode->status.anon_access;
348 _leave(" = t [anon %x]", *_access);
349 return true;
350 }
351
352 permits = rcu_dereference(vnode->permit_cache);
353 if (permits) {
354 for (i = 0; i < permits->nr_permits; i++) {
355 if (permits->permits[i].key < key)
356 continue;
357 if (permits->permits[i].key > key)
358 break;
359
360 *_access = permits->permits[i].access;
361 _leave(" = %u [perm %x]", !permits->invalidated, *_access);
362 return !permits->invalidated;
363 }
364 }
365
366 _leave(" = f");
367 return false;
368}
369
370/*
371 * check with the fileserver to see if the directory or parent directory is
372 * permitted to be accessed with this authorisation, and if so, what access it
373 * is granted
374 */
375int afs_check_permit(struct afs_vnode *vnode, struct key *key,
376 afs_access_t *_access)
377{
378 struct afs_permits *permits;
379 bool valid = false;
380 int i, ret;
381
382 _enter("{%llx:%llu},%x",
383 vnode->fid.vid, vnode->fid.vnode, key_serial(key));
384
385 /* check the permits to see if we've got one yet */
386 if (key == vnode->volume->cell->anonymous_key) {
387 _debug("anon");
388 *_access = vnode->status.anon_access;
389 valid = true;
390 } else {
391 rcu_read_lock();
392 permits = rcu_dereference(vnode->permit_cache);
393 if (permits) {
394 for (i = 0; i < permits->nr_permits; i++) {
395 if (permits->permits[i].key < key)
396 continue;
397 if (permits->permits[i].key > key)
398 break;
399
400 *_access = permits->permits[i].access;
401 valid = !permits->invalidated;
402 break;
403 }
404 }
405 rcu_read_unlock();
406 }
407
408 if (!valid) {
409 /* Check the status on the file we're actually interested in
410 * (the post-processing will cache the result).
411 */
412 _debug("no valid permit");
413
414 ret = afs_fetch_status(vnode, key, false, _access);
415 if (ret < 0) {
416 *_access = 0;
417 _leave(" = %d", ret);
418 return ret;
419 }
420 }
421
422 _leave(" = 0 [access %x]", *_access);
423 return 0;
424}
425
426/*
427 * check the permissions on an AFS file
428 * - AFS ACLs are attached to directories only, and a file is controlled by its
429 * parent directory's ACL
430 */
431int afs_permission(const struct mnt_idmap *idmap, struct inode *inode,
432 int mask)
433{
434 struct afs_vnode *vnode = AFS_FS_I(inode);
435 afs_access_t access;
436 struct key *key;
437 int ret = 0;
438
439 _enter("{{%llx:%llu},%lx},%x,",
440 vnode->fid.vid, vnode->fid.vnode, vnode->flags, mask);
441
442 if (mask & MAY_NOT_BLOCK) {
443 key = afs_request_key_rcu(vnode->volume->cell);
444 if (IS_ERR_OR_NULL(key))
445 return -ECHILD;
446
447 ret = -ECHILD;
448 if (!afs_check_validity(vnode) ||
449 !afs_check_permit_rcu(vnode, key, &access))
450 goto error;
451 } else {
452 key = afs_request_key(vnode->volume->cell);
453 if (IS_ERR(key)) {
454 _leave(" = %ld [key]", PTR_ERR(key));
455 return PTR_ERR(key);
456 }
457
458 ret = afs_validate(vnode, key);
459 if (ret < 0)
460 goto error;
461
462 /* check the permits to see if we've got one yet */
463 ret = afs_check_permit(vnode, key, &access);
464 if (ret < 0)
465 goto error;
466 }
467
468 /* interpret the access mask */
469 _debug("REQ %x ACC %x on %s",
470 mask, access, S_ISDIR(inode->i_mode) ? "dir" : "file");
471
472 ret = 0;
473 if (S_ISDIR(inode->i_mode)) {
474 if (mask & (MAY_EXEC | MAY_READ | MAY_CHDIR)) {
475 if (!(access & AFS_ACE_LOOKUP))
476 goto permission_denied;
477 }
478 if (mask & MAY_WRITE) {
479 if (!(access & (AFS_ACE_DELETE | /* rmdir, unlink, rename from */
480 AFS_ACE_INSERT))) /* create, mkdir, symlink, rename to */
481 goto permission_denied;
482 }
483 } else {
484 if (!(access & AFS_ACE_LOOKUP))
485 goto permission_denied;
486 if ((mask & MAY_EXEC) && !(inode->i_mode & S_IXUSR))
487 goto permission_denied;
488 if (mask & (MAY_EXEC | MAY_READ)) {
489 if (!(access & AFS_ACE_READ))
490 goto permission_denied;
491 if (!(inode->i_mode & S_IRUSR))
492 goto permission_denied;
493 } else if (mask & MAY_WRITE) {
494 if (!(access & AFS_ACE_WRITE))
495 goto permission_denied;
496 if (!(inode->i_mode & S_IWUSR))
497 goto permission_denied;
498 }
499 }
500
501 key_put(key);
502 _leave(" = %d", ret);
503 return ret;
504
505permission_denied:
506 ret = -EACCES;
507error:
508 key_put(key);
509 _leave(" = %d", ret);
510 return ret;
511}
512
513void __exit afs_clean_up_permit_cache(void)
514{
515 int i;
516
517 for (i = 0; i < HASH_SIZE(afs_permits_cache); i++)
518 WARN_ON_ONCE(!hlist_empty(&afs_permits_cache[i]));
519
520}