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 */
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 */
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 */
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 */
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 */
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 */
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 memcpy(permits->permits, xpermits->permits,
193 count * sizeof(struct afs_permit));
194
195 _debug("key %x access %x",
196 key_serial(key), vnode->status.caller_access);
197 permits->permits[count].access_mask = vnode->status.caller_access;
198 permits->permits[count].key = key_get(key);
199 permits->count = count + 1;
200
201 rcu_assign_pointer(auth_vnode->permits, permits);
202 if (xpermits)
203 call_rcu(&xpermits->rcu, afs_dispose_of_permits);
204
205 out_unlock:
206 mutex_unlock(&auth_vnode->permits_lock);
207 iput(&auth_vnode->vfs_inode);
208 _leave("");
209 }
210
211 /*
212 * check with the fileserver to see if the directory or parent directory is
213 * permitted to be accessed with this authorisation, and if so, what access it
214 * is granted
215 */
216 static int afs_check_permit(struct afs_vnode *vnode, struct key *key,
217 afs_access_t *_access)
218 {
219 struct afs_permits *permits;
220 struct afs_permit *permit;
221 struct afs_vnode *auth_vnode;
222 bool valid;
223 int loop, ret;
224
225 _enter("{%x:%u},%x",
226 vnode->fid.vid, vnode->fid.vnode, key_serial(key));
227
228 auth_vnode = afs_get_auth_inode(vnode, key);
229 if (IS_ERR(auth_vnode)) {
230 *_access = 0;
231 _leave(" = %ld", PTR_ERR(auth_vnode));
232 return PTR_ERR(auth_vnode);
233 }
234
235 ASSERT(S_ISDIR(auth_vnode->vfs_inode.i_mode));
236
237 /* check the permits to see if we've got one yet */
238 if (key == auth_vnode->volume->cell->anonymous_key) {
239 _debug("anon");
240 *_access = auth_vnode->status.anon_access;
241 valid = true;
242 } else {
243 valid = false;
244 rcu_read_lock();
245 permits = rcu_dereference(auth_vnode->permits);
246 if (permits) {
247 permit = permits->permits;
248 for (loop = permits->count; loop > 0; loop--) {
249 if (permit->key == key) {
250 _debug("found in cache");
251 *_access = permit->access_mask;
252 valid = true;
253 break;
254 }
255 permit++;
256 }
257 }
258 rcu_read_unlock();
259 }
260
261 if (!valid) {
262 /* check the status on the file we're actually interested in
263 * (the post-processing will cache the result on auth_vnode) */
264 _debug("no valid permit");
265
266 set_bit(AFS_VNODE_CB_BROKEN, &vnode->flags);
267 ret = afs_vnode_fetch_status(vnode, auth_vnode, key);
268 if (ret < 0) {
269 iput(&auth_vnode->vfs_inode);
270 *_access = 0;
271 _leave(" = %d", ret);
272 return ret;
273 }
274 *_access = vnode->status.caller_access;
275 }
276
277 iput(&auth_vnode->vfs_inode);
278 _leave(" = 0 [access %x]", *_access);
279 return 0;
280 }
281
282 /*
283 * check the permissions on an AFS file
284 * - AFS ACLs are attached to directories only, and a file is controlled by its
285 * parent directory's ACL
286 */
287 int afs_permission(struct inode *inode, int mask, struct nameidata *nd)
288 {
289 struct afs_vnode *vnode = AFS_FS_I(inode);
290 afs_access_t uninitialized_var(access);
291 struct key *key;
292 int ret;
293
294 _enter("{{%x:%u},%lx},%x,",
295 vnode->fid.vid, vnode->fid.vnode, vnode->flags, mask);
296
297 key = afs_request_key(vnode->volume->cell);
298 if (IS_ERR(key)) {
299 _leave(" = %ld [key]", PTR_ERR(key));
300 return PTR_ERR(key);
301 }
302
303 /* if the promise has expired, we need to check the server again */
304 if (!vnode->cb_promised) {
305 _debug("not promised");
306 ret = afs_vnode_fetch_status(vnode, NULL, key);
307 if (ret < 0)
308 goto error;
309 _debug("new promise [fl=%lx]", vnode->flags);
310 }
311
312 /* check the permits to see if we've got one yet */
313 ret = afs_check_permit(vnode, key, &access);
314 if (ret < 0)
315 goto error;
316
317 /* interpret the access mask */
318 _debug("REQ %x ACC %x on %s",
319 mask, access, S_ISDIR(inode->i_mode) ? "dir" : "file");
320
321 if (S_ISDIR(inode->i_mode)) {
322 if (mask & MAY_EXEC) {
323 if (!(access & AFS_ACE_LOOKUP))
324 goto permission_denied;
325 } else if (mask & MAY_READ) {
326 if (!(access & AFS_ACE_READ))
327 goto permission_denied;
328 } else if (mask & MAY_WRITE) {
329 if (!(access & (AFS_ACE_DELETE | /* rmdir, unlink, rename from */
330 AFS_ACE_INSERT | /* create, mkdir, symlink, rename to */
331 AFS_ACE_WRITE))) /* chmod */
332 goto permission_denied;
333 } else {
334 BUG();
335 }
336 } else {
337 if (!(access & AFS_ACE_LOOKUP))
338 goto permission_denied;
339 if (mask & (MAY_EXEC | MAY_READ)) {
340 if (!(access & AFS_ACE_READ))
341 goto permission_denied;
342 } else if (mask & MAY_WRITE) {
343 if (!(access & AFS_ACE_WRITE))
344 goto permission_denied;
345 }
346 }
347
348 key_put(key);
349 ret = generic_permission(inode, mask, NULL);
350 _leave(" = %d", ret);
351 return ret;
352
353 permission_denied:
354 ret = -EACCES;
355 error:
356 key_put(key);
357 _leave(" = %d", ret);
358 return ret;
359 }
360
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