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 */
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(&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 */
afs_zap_permits(struct rcu_head * rcu)51 void 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 */
afs_dispose_of_permits(struct rcu_head * rcu)67 static 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 */
afs_get_auth_inode(struct afs_vnode * vnode,struct key * key)83 static 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 */
afs_clear_permits(struct afs_vnode * vnode)109 void 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 */
afs_cache_permit(struct afs_vnode * vnode,struct key * key,long acl_order)129 void 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
206 out_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 */
afs_check_permit(struct afs_vnode * vnode,struct key * key,afs_access_t * _access)217 static 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 */
afs_permission(struct inode * inode,int mask)288 int 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
357 permission_denied:
358 ret = -EACCES;
359 error:
360 key_put(key);
361 _leave(" = %d", ret);
362 return ret;
363 }
364