summaryrefslogtreecommitdiffstats
path: root/fs/afs/security.c
blob: bb4ed144d0e446c627fb8b4e391664058d094b87 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
/* AFS security handling
 *
 * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 */

#include <linux/init.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include <linux/ctype.h>
#include <linux/sched.h>
#include <keys/rxrpc-type.h>
#include "internal.h"

/*
 * get a key
 */
struct key *afs_request_key(struct afs_cell *cell)
{
	struct key *key;

	_enter("{%x}", key_serial(cell->anonymous_key));

	_debug("key %s", cell->anonymous_key->description);
	key = request_key(&key_type_rxrpc, cell->anonymous_key->description,
			  NULL);
	if (IS_ERR(key)) {
		if (PTR_ERR(key) != -ENOKEY) {
			_leave(" = %ld", PTR_ERR(key));
			return key;
		}

		/* act as anonymous user */
		_leave(" = {%x} [anon]", key_serial(cell->anonymous_key));
		return key_get(cell->anonymous_key);
	} else {
		/* act as authorised user */
		_leave(" = {%x} [auth]", key_serial(key));
		return key;
	}
}

/*
 * dispose of a permits list
 */
void afs_zap_permits(struct rcu_head *rcu)
{
	struct afs_permits *permits =
		container_of(rcu, struct afs_permits, rcu);
	int loop;

	_enter("{%d}", permits->count);

	for (loop = permits->count - 1; loop >= 0; loop--)
		key_put(permits->permits[loop].key);
	kfree(permits);
}

/*
 * dispose of a permits list in which all the key pointers have been copied
 */
static void afs_dispose_of_permits(struct rcu_head *rcu)
{
	struct afs_permits *permits =
		container_of(rcu, struct afs_permits, rcu);

	_enter("{%d}", permits->count);

	kfree(permits);
}

/*
 * get the authorising vnode - this is the specified inode itself if it's a
 * directory or it's the parent directory if the specified inode is a file or
 * symlink
 * - the caller must release the ref on the inode
 */
static struct afs_vnode *afs_get_auth_inode(struct afs_vnode *vnode,
					    struct key *key)
{
	struct afs_vnode *auth_vnode;
	struct inode *auth_inode;

	_enter("");

	if (S_ISDIR(vnode->vfs_inode.i_mode)) {
		auth_inode = igrab(&vnode->vfs_inode);
		ASSERT(auth_inode != NULL);
	} else {
		auth_inode = afs_iget(vnode->vfs_inode.i_sb, key,
				      &vnode->status.parent, NULL, NULL);
		if (IS_ERR(auth_inode))
			return ERR_CAST(auth_inode);
	}

	auth_vnode = AFS_FS_I(auth_inode);
	_leave(" = {%x}", auth_vnode->fid.vnode);
	return auth_vnode;
}

/*
 * clear the permit cache on a directory vnode
 */
void afs_clear_permits(struct afs_vnode *vnode)
{
	struct afs_permits *permits;

	_enter("{%x:%u}", vnode->fid.vid, vnode->fid.vnode);

	mutex_lock(&vnode->permits_lock);
	permits = vnode->permits;
	rcu_assign_pointer(vnode->permits, NULL);
	mutex_unlock(&vnode->permits_lock);

	if (permits)
		call_rcu(&permits->rcu, afs_zap_permits);
	_leave("");
}

/*
 * add the result obtained for a vnode to its or its parent directory's cache
 * for the key used to access it
 */
void afs_cache_permit(struct afs_vnode *vnode, struct key *key, long acl_order)
{
	struct afs_permits *permits, *xpermits;
	struct afs_permit *permit;
	struct afs_vnode *auth_vnode;
	int count, loop;

	_enter("{%x:%u},%x,%lx",
	       vnode->fid.vid, vnode->fid.vnode, key_serial(key), acl_order);

	auth_vnode = afs_get_auth_inode(vnode, key);
	if (IS_ERR(auth_vnode)) {
		_leave(" [get error %ld]", PTR_ERR(auth_vnode));
		return;
	}

	mutex_lock(&auth_vnode->permits_lock);

	/* guard against a rename being detected whilst we waited for the
	 * lock */
	if (memcmp(&auth_vnode->fid, &vnode->status.parent,
		   sizeof(struct afs_fid)) != 0) {
		_debug("renamed");
		goto out_unlock;
	}

	/* have to be careful as the directory's callback may be broken between
	 * us receiving the status we're trying to cache and us getting the
	 * lock to update the cache for the status */
	if (auth_vnode->acl_order - acl_order > 0) {
		_debug("ACL changed?");
		goto out_unlock;
	}

	/* always update the anonymous mask */
	_debug("anon access %x", vnode->status.anon_access);
	auth_vnode->status.anon_access = vnode->status.anon_access;
	if (key == vnode->volume->cell->anonymous_key)
		goto out_unlock;

	xpermits = auth_vnode->permits;
	count = 0;
	if (xpermits) {
		/* see if the permit is already in the list
		 * - if it is then we just amend the list
		 */
		count = xpermits->count;
		permit = xpermits->permits;
		for (loop = count; loop > 0; loop--) {
			if (permit->key == key) {
				permit->access_mask =
					vnode->status.caller_access;
				goto out_unlock;
			}
			permit++;
		}
	}

	permits = kmalloc(sizeof(*permits) + sizeof(*permit) * (count + 1),
			  GFP_NOFS);
	if (!permits)
		goto out_unlock;

	if (xpermits)
		memcpy(permits->permits, xpermits->permits,
			count * sizeof(struct afs_permit));

	_debug("key %x access %x",
	       key_serial(key), vnode->status.caller_access);
	permits->permits[count].access_mask = vnode->status.caller_access;
	permits->permits[count].key = key_get(key);
	permits->count = count + 1;

	rcu_assign_pointer(auth_vnode->permits, permits);
	if (xpermits)
		call_rcu(&xpermits->rcu, afs_dispose_of_permits);

out_unlock:
	mutex_unlock(&auth_vnode->permits_lock);
	iput(&auth_vnode->vfs_inode);
	_leave("");
}

/*
 * check with the fileserver to see if the directory or parent directory is
 * permitted to be accessed with this authorisation, and if so, what access it
 * is granted
 */
static int afs_check_permit(struct afs_vnode *vnode, struct key *key,
			    afs_access_t *_access)
{
	struct afs_permits *permits;
	struct afs_permit *permit;
	struct afs_vnode *auth_vnode;
	bool valid;
	int loop, ret;

	_enter("{%x:%u},%x",
	       vnode->fid.vid, vnode->fid.vnode, key_serial(key));

	auth_vnode = afs_get_auth_inode(vnode, key);
	if (IS_ERR(auth_vnode)) {
		*_access = 0;
		_leave(" = %ld", PTR_ERR(auth_vnode));
		return PTR_ERR(auth_vnode);
	}

	ASSERT(S_ISDIR(auth_vnode->vfs_inode.i_mode));

	/* check the permits to see if we've got one yet */
	if (key == auth_vnode->volume->cell->anonymous_key) {
		_debug("anon");
		*_access = auth_vnode->status.anon_access;
		valid = true;
	} else {
		valid = false;
		rcu_read_lock();
		permits = rcu_dereference(auth_vnode->permits);
		if (permits) {
			permit = permits->permits;
			for (loop = permits->count; loop > 0; loop--) {
				if (permit->key == key) {
					_debug("found in cache");
					*_access = permit->access_mask;
					valid = true;
					break;
				}
				permit++;
			}
		}
		rcu_read_unlock();
	}

	if (!valid) {
		/* check the status on the file we're actually interested in
		 * (the post-processing will cache the result on auth_vnode) */
		_debug("no valid permit");

		set_bit(AFS_VNODE_CB_BROKEN, &vnode->flags);
		ret = afs_vnode_fetch_status(vnode, auth_vnode, key);
		if (ret < 0) {
			iput(&auth_vnode->vfs_inode);
			*_access = 0;
			_leave(" = %d", ret);
			return ret;
		}
		*_access = vnode->status.caller_access;
	}

	iput(&auth_vnode->vfs_inode);
	_leave(" = 0 [access %x]", *_access);
	return 0;
}

/*
 * check the permissions on an AFS file
 * - AFS ACLs are attached to directories only, and a file is controlled by its
 *   parent directory's ACL
 */
int afs_permission(struct inode *inode, int mask)
{
	struct afs_vnode *vnode = AFS_FS_I(inode);
	afs_access_t uninitialized_var(access);
	struct key *key;
	int ret;

	_enter("{{%x:%u},%lx},%x,",
	       vnode->fid.vid, vnode->fid.vnode, vnode->flags, mask);

	key = afs_request_key(vnode->volume->cell);
	if (IS_ERR(key)) {
		_leave(" = %ld [key]", PTR_ERR(key));
		return PTR_ERR(key);
	}

	/* if the promise has expired, we need to check the server again */
	if (!vnode->cb_promised) {
		_debug("not promised");
		ret = afs_vnode_fetch_status(vnode, NULL, key);
		if (ret < 0)
			goto error;
		_debug("new promise [fl=%lx]", vnode->flags);
	}

	/* check the permits to see if we've got one yet */
	ret = afs_check_permit(vnode, key, &access);
	if (ret < 0)
		goto error;

	/* interpret the access mask */
	_debug("REQ %x ACC %x on %s",
	       mask, access, S_ISDIR(inode->i_mode) ? "dir" : "file");

	if (S_ISDIR(inode->i_mode)) {
		if (mask & MAY_EXEC) {
			if (!(access & AFS_ACE_LOOKUP))
				goto permission_denied;
		} else if (mask & MAY_READ) {
			if (!(access & AFS_ACE_READ))
				goto permission_denied;
		} else if (mask & MAY_WRITE) {
			if (!(access & (AFS_ACE_DELETE | /* rmdir, unlink, rename from */
					AFS_ACE_INSERT | /* create, mkdir, symlink, rename to */
					AFS_ACE_WRITE))) /* chmod */
				goto permission_denied;
		} else {
			BUG();
		}
	} else {
		if (!(access & AFS_ACE_LOOKUP))
			goto permission_denied;
		if (mask & (MAY_EXEC | MAY_READ)) {
			if (!(access & AFS_ACE_READ))
				goto permission_denied;
		} else if (mask & MAY_WRITE) {
			if (!(access & AFS_ACE_WRITE))
				goto permission_denied;
		}
	}

	key_put(key);
	ret = generic_permission(inode, mask, NULL);
	_leave(" = %d", ret);
	return ret;

permission_denied:
	ret = -EACCES;
error:
	key_put(key);
	_leave(" = %d", ret);
	return ret;
}