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1/* AFS security handling
2 *
3 * Copyright (C) 2007, 2017 Red Hat, Inc. All Rights Reserved.
4 * Written by David Howells (dhowells@redhat.com)
5 *
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public License
8 * as published by the Free Software Foundation; either version
9 * 2 of the License, or (at your option) any later version.
10 */
11
12#include <linux/init.h>
13#include <linux/slab.h>
14#include <linux/fs.h>
15#include <linux/ctype.h>
16#include <linux/sched.h>
17#include <linux/hashtable.h>
18#include <keys/rxrpc-type.h>
19#include "internal.h"
20
21static DEFINE_HASHTABLE(afs_permits_cache, 10);
22static DEFINE_SPINLOCK(afs_permits_lock);
23
24/*
25 * get a key
26 */
27struct key *afs_request_key(struct afs_cell *cell)
28{
29 struct key *key;
30
31 _enter("{%x}", key_serial(cell->anonymous_key));
32
33 _debug("key %s", cell->anonymous_key->description);
34 key = request_key(&key_type_rxrpc, cell->anonymous_key->description,
35 NULL);
36 if (IS_ERR(key)) {
37 if (PTR_ERR(key) != -ENOKEY) {
38 _leave(" = %ld", PTR_ERR(key));
39 return key;
40 }
41
42 /* act as anonymous user */
43 _leave(" = {%x} [anon]", key_serial(cell->anonymous_key));
44 return key_get(cell->anonymous_key);
45 } else {
46 /* act as authorised user */
47 _leave(" = {%x} [auth]", key_serial(key));
48 return key;
49 }
50}
51
52/*
53 * Dispose of a list of permits.
54 */
55static void afs_permits_rcu(struct rcu_head *rcu)
56{
57 struct afs_permits *permits =
58 container_of(rcu, struct afs_permits, rcu);
59 int i;
60
61 for (i = 0; i < permits->nr_permits; i++)
62 key_put(permits->permits[i].key);
63 kfree(permits);
64}
65
66/*
67 * Discard a permission cache.
68 */
69void afs_put_permits(struct afs_permits *permits)
70{
71 if (permits && refcount_dec_and_test(&permits->usage)) {
72 spin_lock(&afs_permits_lock);
73 hash_del_rcu(&permits->hash_node);
74 spin_unlock(&afs_permits_lock);
75 call_rcu(&permits->rcu, afs_permits_rcu);
76 }
77}
78
79/*
80 * Clear a permit cache on callback break.
81 */
82void afs_clear_permits(struct afs_vnode *vnode)
83{
84 struct afs_permits *permits;
85
86 spin_lock(&vnode->lock);
87 permits = rcu_dereference_protected(vnode->permit_cache,
88 lockdep_is_held(&vnode->lock));
89 RCU_INIT_POINTER(vnode->permit_cache, NULL);
90 vnode->cb_break++;
91 spin_unlock(&vnode->lock);
92
93 if (permits)
94 afs_put_permits(permits);
95}
96
97/*
98 * Hash a list of permits. Use simple addition to make it easy to add an extra
99 * one at an as-yet indeterminate position in the list.
100 */
101static void afs_hash_permits(struct afs_permits *permits)
102{
103 unsigned long h = permits->nr_permits;
104 int i;
105
106 for (i = 0; i < permits->nr_permits; i++) {
107 h += (unsigned long)permits->permits[i].key / sizeof(void *);
108 h += permits->permits[i].access;
109 }
110
111 permits->h = h;
112}
113
114/*
115 * Cache the CallerAccess result obtained from doing a fileserver operation
116 * that returned a vnode status for a particular key. If a callback break
117 * occurs whilst the operation was in progress then we have to ditch the cache
118 * as the ACL *may* have changed.
119 */
120void afs_cache_permit(struct afs_vnode *vnode, struct key *key,
121 unsigned int cb_break)
122{
123 struct afs_permits *permits, *xpermits, *replacement, *zap, *new = NULL;
124 afs_access_t caller_access = READ_ONCE(vnode->status.caller_access);
125 size_t size = 0;
126 bool changed = false;
127 int i, j;
128
129 _enter("{%x:%u},%x,%x",
130 vnode->fid.vid, vnode->fid.vnode, key_serial(key), caller_access);
131
132 rcu_read_lock();
133
134 /* Check for the common case first: We got back the same access as last
135 * time we tried and already have it recorded.
136 */
137 permits = rcu_dereference(vnode->permit_cache);
138 if (permits) {
139 if (!permits->invalidated) {
140 for (i = 0; i < permits->nr_permits; i++) {
141 if (permits->permits[i].key < key)
142 continue;
143 if (permits->permits[i].key > key)
144 break;
145 if (permits->permits[i].access != caller_access) {
146 changed = true;
147 break;
148 }
149
150 if (cb_break != afs_cb_break_sum(vnode, vnode->cb_interest)) {
151 changed = true;
152 break;
153 }
154
155 /* The cache is still good. */
156 rcu_read_unlock();
157 return;
158 }
159 }
160
161 changed |= permits->invalidated;
162 size = permits->nr_permits;
163
164 /* If this set of permits is now wrong, clear the permits
165 * pointer so that no one tries to use the stale information.
166 */
167 if (changed) {
168 spin_lock(&vnode->lock);
169 if (permits != rcu_access_pointer(vnode->permit_cache))
170 goto someone_else_changed_it_unlock;
171 RCU_INIT_POINTER(vnode->permit_cache, NULL);
172 spin_unlock(&vnode->lock);
173
174 afs_put_permits(permits);
175 permits = NULL;
176 size = 0;
177 }
178 }
179
180 if (cb_break != afs_cb_break_sum(vnode, vnode->cb_interest))
181 goto someone_else_changed_it;
182
183 /* We need a ref on any permits list we want to copy as we'll have to
184 * drop the lock to do memory allocation.
185 */
186 if (permits && !refcount_inc_not_zero(&permits->usage))
187 goto someone_else_changed_it;
188
189 rcu_read_unlock();
190
191 /* Speculatively create a new list with the revised permission set. We
192 * discard this if we find an extant match already in the hash, but
193 * it's easier to compare with memcmp this way.
194 *
195 * We fill in the key pointers at this time, but we don't get the refs
196 * yet.
197 */
198 size++;
199 new = kzalloc(sizeof(struct afs_permits) +
200 sizeof(struct afs_permit) * size, GFP_NOFS);
201 if (!new)
202 goto out_put;
203
204 refcount_set(&new->usage, 1);
205 new->nr_permits = size;
206 i = j = 0;
207 if (permits) {
208 for (i = 0; i < permits->nr_permits; i++) {
209 if (j == i && permits->permits[i].key > key) {
210 new->permits[j].key = key;
211 new->permits[j].access = caller_access;
212 j++;
213 }
214 new->permits[j].key = permits->permits[i].key;
215 new->permits[j].access = permits->permits[i].access;
216 j++;
217 }
218 }
219
220 if (j == i) {
221 new->permits[j].key = key;
222 new->permits[j].access = caller_access;
223 }
224
225 afs_hash_permits(new);
226
227 /* Now see if the permit list we want is actually already available */
228 spin_lock(&afs_permits_lock);
229
230 hash_for_each_possible(afs_permits_cache, xpermits, hash_node, new->h) {
231 if (xpermits->h != new->h ||
232 xpermits->invalidated ||
233 xpermits->nr_permits != new->nr_permits ||
234 memcmp(xpermits->permits, new->permits,
235 new->nr_permits * sizeof(struct afs_permit)) != 0)
236 continue;
237
238 if (refcount_inc_not_zero(&xpermits->usage)) {
239 replacement = xpermits;
240 goto found;
241 }
242
243 break;
244 }
245
246 for (i = 0; i < new->nr_permits; i++)
247 key_get(new->permits[i].key);
248 hash_add_rcu(afs_permits_cache, &new->hash_node, new->h);
249 replacement = new;
250 new = NULL;
251
252found:
253 spin_unlock(&afs_permits_lock);
254
255 kfree(new);
256
257 spin_lock(&vnode->lock);
258 zap = rcu_access_pointer(vnode->permit_cache);
259 if (cb_break == afs_cb_break_sum(vnode, vnode->cb_interest) &&
260 zap == permits)
261 rcu_assign_pointer(vnode->permit_cache, replacement);
262 else
263 zap = replacement;
264 spin_unlock(&vnode->lock);
265 afs_put_permits(zap);
266out_put:
267 afs_put_permits(permits);
268 return;
269
270someone_else_changed_it_unlock:
271 spin_unlock(&vnode->lock);
272someone_else_changed_it:
273 /* Someone else changed the cache under us - don't recheck at this
274 * time.
275 */
276 rcu_read_unlock();
277 return;
278}
279
280/*
281 * check with the fileserver to see if the directory or parent directory is
282 * permitted to be accessed with this authorisation, and if so, what access it
283 * is granted
284 */
285int afs_check_permit(struct afs_vnode *vnode, struct key *key,
286 afs_access_t *_access)
287{
288 struct afs_permits *permits;
289 bool valid = false;
290 int i, ret;
291
292 _enter("{%x:%u},%x",
293 vnode->fid.vid, vnode->fid.vnode, key_serial(key));
294
295 /* check the permits to see if we've got one yet */
296 if (key == vnode->volume->cell->anonymous_key) {
297 _debug("anon");
298 *_access = vnode->status.anon_access;
299 valid = true;
300 } else {
301 rcu_read_lock();
302 permits = rcu_dereference(vnode->permit_cache);
303 if (permits) {
304 for (i = 0; i < permits->nr_permits; i++) {
305 if (permits->permits[i].key < key)
306 continue;
307 if (permits->permits[i].key > key)
308 break;
309
310 *_access = permits->permits[i].access;
311 valid = !permits->invalidated;
312 break;
313 }
314 }
315 rcu_read_unlock();
316 }
317
318 if (!valid) {
319 /* Check the status on the file we're actually interested in
320 * (the post-processing will cache the result).
321 */
322 _debug("no valid permit");
323
324 ret = afs_fetch_status(vnode, key, false);
325 if (ret < 0) {
326 *_access = 0;
327 _leave(" = %d", ret);
328 return ret;
329 }
330 *_access = vnode->status.caller_access;
331 }
332
333 _leave(" = 0 [access %x]", *_access);
334 return 0;
335}
336
337/*
338 * check the permissions on an AFS file
339 * - AFS ACLs are attached to directories only, and a file is controlled by its
340 * parent directory's ACL
341 */
342int afs_permission(struct inode *inode, int mask)
343{
344 struct afs_vnode *vnode = AFS_FS_I(inode);
345 afs_access_t uninitialized_var(access);
346 struct key *key;
347 int ret;
348
349 if (mask & MAY_NOT_BLOCK)
350 return -ECHILD;
351
352 _enter("{{%x:%u},%lx},%x,",
353 vnode->fid.vid, vnode->fid.vnode, vnode->flags, mask);
354
355 key = afs_request_key(vnode->volume->cell);
356 if (IS_ERR(key)) {
357 _leave(" = %ld [key]", PTR_ERR(key));
358 return PTR_ERR(key);
359 }
360
361 ret = afs_validate(vnode, key);
362 if (ret < 0)
363 goto error;
364
365 /* check the permits to see if we've got one yet */
366 ret = afs_check_permit(vnode, key, &access);
367 if (ret < 0)
368 goto error;
369
370 /* interpret the access mask */
371 _debug("REQ %x ACC %x on %s",
372 mask, access, S_ISDIR(inode->i_mode) ? "dir" : "file");
373
374 if (S_ISDIR(inode->i_mode)) {
375 if (mask & (MAY_EXEC | MAY_READ | MAY_CHDIR)) {
376 if (!(access & AFS_ACE_LOOKUP))
377 goto permission_denied;
378 }
379 if (mask & MAY_WRITE) {
380 if (!(access & (AFS_ACE_DELETE | /* rmdir, unlink, rename from */
381 AFS_ACE_INSERT))) /* create, mkdir, symlink, rename to */
382 goto permission_denied;
383 }
384 } else {
385 if (!(access & AFS_ACE_LOOKUP))
386 goto permission_denied;
387 if ((mask & MAY_EXEC) && !(inode->i_mode & S_IXUSR))
388 goto permission_denied;
389 if (mask & (MAY_EXEC | MAY_READ)) {
390 if (!(access & AFS_ACE_READ))
391 goto permission_denied;
392 if (!(inode->i_mode & S_IRUSR))
393 goto permission_denied;
394 } else if (mask & MAY_WRITE) {
395 if (!(access & AFS_ACE_WRITE))
396 goto permission_denied;
397 if (!(inode->i_mode & S_IWUSR))
398 goto permission_denied;
399 }
400 }
401
402 key_put(key);
403 _leave(" = %d", ret);
404 return ret;
405
406permission_denied:
407 ret = -EACCES;
408error:
409 key_put(key);
410 _leave(" = %d", ret);
411 return ret;
412}
413
414void __exit afs_clean_up_permit_cache(void)
415{
416 int i;
417
418 for (i = 0; i < HASH_SIZE(afs_permits_cache); i++)
419 WARN_ON_ONCE(!hlist_empty(&afs_permits_cache[i]));
420
421}
1/* AFS security handling
2 *
3 * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
4 * Written by David Howells (dhowells@redhat.com)
5 *
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public License
8 * as published by the Free Software Foundation; either version
9 * 2 of the License, or (at your option) any later version.
10 */
11
12#include <linux/init.h>
13#include <linux/slab.h>
14#include <linux/fs.h>
15#include <linux/ctype.h>
16#include <linux/sched.h>
17#include <keys/rxrpc-type.h>
18#include "internal.h"
19
20/*
21 * get a key
22 */
23struct 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(&key_type_rxrpc, cell->anonymous_key->description,
31 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 * dispose of a permits list
50 */
51void afs_zap_permits(struct rcu_head *rcu)
52{
53 struct afs_permits *permits =
54 container_of(rcu, struct afs_permits, rcu);
55 int loop;
56
57 _enter("{%d}", permits->count);
58
59 for (loop = permits->count - 1; loop >= 0; loop--)
60 key_put(permits->permits[loop].key);
61 kfree(permits);
62}
63
64/*
65 * dispose of a permits list in which all the key pointers have been copied
66 */
67static void afs_dispose_of_permits(struct rcu_head *rcu)
68{
69 struct afs_permits *permits =
70 container_of(rcu, struct afs_permits, rcu);
71
72 _enter("{%d}", permits->count);
73
74 kfree(permits);
75}
76
77/*
78 * get the authorising vnode - this is the specified inode itself if it's a
79 * directory or it's the parent directory if the specified inode is a file or
80 * symlink
81 * - the caller must release the ref on the inode
82 */
83static struct afs_vnode *afs_get_auth_inode(struct afs_vnode *vnode,
84 struct key *key)
85{
86 struct afs_vnode *auth_vnode;
87 struct inode *auth_inode;
88
89 _enter("");
90
91 if (S_ISDIR(vnode->vfs_inode.i_mode)) {
92 auth_inode = igrab(&vnode->vfs_inode);
93 ASSERT(auth_inode != NULL);
94 } else {
95 auth_inode = afs_iget(vnode->vfs_inode.i_sb, key,
96 &vnode->status.parent, NULL, NULL);
97 if (IS_ERR(auth_inode))
98 return ERR_CAST(auth_inode);
99 }
100
101 auth_vnode = AFS_FS_I(auth_inode);
102 _leave(" = {%x}", auth_vnode->fid.vnode);
103 return auth_vnode;
104}
105
106/*
107 * clear the permit cache on a directory vnode
108 */
109void afs_clear_permits(struct afs_vnode *vnode)
110{
111 struct afs_permits *permits;
112
113 _enter("{%x:%u}", vnode->fid.vid, vnode->fid.vnode);
114
115 mutex_lock(&vnode->permits_lock);
116 permits = vnode->permits;
117 rcu_assign_pointer(vnode->permits, NULL);
118 mutex_unlock(&vnode->permits_lock);
119
120 if (permits)
121 call_rcu(&permits->rcu, afs_zap_permits);
122 _leave("");
123}
124
125/*
126 * add the result obtained for a vnode to its or its parent directory's cache
127 * for the key used to access it
128 */
129void afs_cache_permit(struct afs_vnode *vnode, struct key *key, long acl_order)
130{
131 struct afs_permits *permits, *xpermits;
132 struct afs_permit *permit;
133 struct afs_vnode *auth_vnode;
134 int count, loop;
135
136 _enter("{%x:%u},%x,%lx",
137 vnode->fid.vid, vnode->fid.vnode, key_serial(key), acl_order);
138
139 auth_vnode = afs_get_auth_inode(vnode, key);
140 if (IS_ERR(auth_vnode)) {
141 _leave(" [get error %ld]", PTR_ERR(auth_vnode));
142 return;
143 }
144
145 mutex_lock(&auth_vnode->permits_lock);
146
147 /* guard against a rename being detected whilst we waited for the
148 * lock */
149 if (memcmp(&auth_vnode->fid, &vnode->status.parent,
150 sizeof(struct afs_fid)) != 0) {
151 _debug("renamed");
152 goto out_unlock;
153 }
154
155 /* have to be careful as the directory's callback may be broken between
156 * us receiving the status we're trying to cache and us getting the
157 * lock to update the cache for the status */
158 if (auth_vnode->acl_order - acl_order > 0) {
159 _debug("ACL changed?");
160 goto out_unlock;
161 }
162
163 /* always update the anonymous mask */
164 _debug("anon access %x", vnode->status.anon_access);
165 auth_vnode->status.anon_access = vnode->status.anon_access;
166 if (key == vnode->volume->cell->anonymous_key)
167 goto out_unlock;
168
169 xpermits = auth_vnode->permits;
170 count = 0;
171 if (xpermits) {
172 /* see if the permit is already in the list
173 * - if it is then we just amend the list
174 */
175 count = xpermits->count;
176 permit = xpermits->permits;
177 for (loop = count; loop > 0; loop--) {
178 if (permit->key == key) {
179 permit->access_mask =
180 vnode->status.caller_access;
181 goto out_unlock;
182 }
183 permit++;
184 }
185 }
186
187 permits = kmalloc(sizeof(*permits) + sizeof(*permit) * (count + 1),
188 GFP_NOFS);
189 if (!permits)
190 goto out_unlock;
191
192 if (xpermits)
193 memcpy(permits->permits, xpermits->permits,
194 count * sizeof(struct afs_permit));
195
196 _debug("key %x access %x",
197 key_serial(key), vnode->status.caller_access);
198 permits->permits[count].access_mask = vnode->status.caller_access;
199 permits->permits[count].key = key_get(key);
200 permits->count = count + 1;
201
202 rcu_assign_pointer(auth_vnode->permits, permits);
203 if (xpermits)
204 call_rcu(&xpermits->rcu, afs_dispose_of_permits);
205
206out_unlock:
207 mutex_unlock(&auth_vnode->permits_lock);
208 iput(&auth_vnode->vfs_inode);
209 _leave("");
210}
211
212/*
213 * check with the fileserver to see if the directory or parent directory is
214 * permitted to be accessed with this authorisation, and if so, what access it
215 * is granted
216 */
217static int afs_check_permit(struct afs_vnode *vnode, struct key *key,
218 afs_access_t *_access)
219{
220 struct afs_permits *permits;
221 struct afs_permit *permit;
222 struct afs_vnode *auth_vnode;
223 bool valid;
224 int loop, ret;
225
226 _enter("{%x:%u},%x",
227 vnode->fid.vid, vnode->fid.vnode, key_serial(key));
228
229 auth_vnode = afs_get_auth_inode(vnode, key);
230 if (IS_ERR(auth_vnode)) {
231 *_access = 0;
232 _leave(" = %ld", PTR_ERR(auth_vnode));
233 return PTR_ERR(auth_vnode);
234 }
235
236 ASSERT(S_ISDIR(auth_vnode->vfs_inode.i_mode));
237
238 /* check the permits to see if we've got one yet */
239 if (key == auth_vnode->volume->cell->anonymous_key) {
240 _debug("anon");
241 *_access = auth_vnode->status.anon_access;
242 valid = true;
243 } else {
244 valid = false;
245 rcu_read_lock();
246 permits = rcu_dereference(auth_vnode->permits);
247 if (permits) {
248 permit = permits->permits;
249 for (loop = permits->count; loop > 0; loop--) {
250 if (permit->key == key) {
251 _debug("found in cache");
252 *_access = permit->access_mask;
253 valid = true;
254 break;
255 }
256 permit++;
257 }
258 }
259 rcu_read_unlock();
260 }
261
262 if (!valid) {
263 /* check the status on the file we're actually interested in
264 * (the post-processing will cache the result on auth_vnode) */
265 _debug("no valid permit");
266
267 set_bit(AFS_VNODE_CB_BROKEN, &vnode->flags);
268 ret = afs_vnode_fetch_status(vnode, auth_vnode, key);
269 if (ret < 0) {
270 iput(&auth_vnode->vfs_inode);
271 *_access = 0;
272 _leave(" = %d", ret);
273 return ret;
274 }
275 *_access = vnode->status.caller_access;
276 }
277
278 iput(&auth_vnode->vfs_inode);
279 _leave(" = 0 [access %x]", *_access);
280 return 0;
281}
282
283/*
284 * check the permissions on an AFS file
285 * - AFS ACLs are attached to directories only, and a file is controlled by its
286 * parent directory's ACL
287 */
288int afs_permission(struct inode *inode, int mask)
289{
290 struct afs_vnode *vnode = AFS_FS_I(inode);
291 afs_access_t uninitialized_var(access);
292 struct key *key;
293 int ret;
294
295 if (mask & MAY_NOT_BLOCK)
296 return -ECHILD;
297
298 _enter("{{%x:%u},%lx},%x,",
299 vnode->fid.vid, vnode->fid.vnode, vnode->flags, mask);
300
301 key = afs_request_key(vnode->volume->cell);
302 if (IS_ERR(key)) {
303 _leave(" = %ld [key]", PTR_ERR(key));
304 return PTR_ERR(key);
305 }
306
307 /* if the promise has expired, we need to check the server again */
308 if (!vnode->cb_promised) {
309 _debug("not promised");
310 ret = afs_vnode_fetch_status(vnode, NULL, key);
311 if (ret < 0)
312 goto error;
313 _debug("new promise [fl=%lx]", vnode->flags);
314 }
315
316 /* check the permits to see if we've got one yet */
317 ret = afs_check_permit(vnode, key, &access);
318 if (ret < 0)
319 goto error;
320
321 /* interpret the access mask */
322 _debug("REQ %x ACC %x on %s",
323 mask, access, S_ISDIR(inode->i_mode) ? "dir" : "file");
324
325 if (S_ISDIR(inode->i_mode)) {
326 if (mask & MAY_EXEC) {
327 if (!(access & AFS_ACE_LOOKUP))
328 goto permission_denied;
329 } else if (mask & MAY_READ) {
330 if (!(access & AFS_ACE_READ))
331 goto permission_denied;
332 } else if (mask & MAY_WRITE) {
333 if (!(access & (AFS_ACE_DELETE | /* rmdir, unlink, rename from */
334 AFS_ACE_INSERT | /* create, mkdir, symlink, rename to */
335 AFS_ACE_WRITE))) /* chmod */
336 goto permission_denied;
337 } else {
338 BUG();
339 }
340 } else {
341 if (!(access & AFS_ACE_LOOKUP))
342 goto permission_denied;
343 if (mask & (MAY_EXEC | MAY_READ)) {
344 if (!(access & AFS_ACE_READ))
345 goto permission_denied;
346 } else if (mask & MAY_WRITE) {
347 if (!(access & AFS_ACE_WRITE))
348 goto permission_denied;
349 }
350 }
351
352 key_put(key);
353 ret = generic_permission(inode, mask);
354 _leave(" = %d", ret);
355 return ret;
356
357permission_denied:
358 ret = -EACCES;
359error:
360 key_put(key);
361 _leave(" = %d", ret);
362 return ret;
363}