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