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-rw-r--r--kernel/auditfilter.c378
1 files changed, 378 insertions, 0 deletions
diff --git a/kernel/auditfilter.c b/kernel/auditfilter.c
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1/* auditfilter.c -- filtering of audit events
2 *
3 * Copyright 2003-2004 Red Hat, Inc.
4 * Copyright 2005 Hewlett-Packard Development Company, L.P.
5 * Copyright 2005 IBM Corporation
6 *
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License as published by
9 * the Free Software Foundation; either version 2 of the License, or
10 * (at your option) any later version.
11 *
12 * This program is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 * GNU General Public License for more details.
16 *
17 * You should have received a copy of the GNU General Public License
18 * along with this program; if not, write to the Free Software
19 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
20 */
21
22#include <linux/kernel.h>
23#include <linux/audit.h>
24#include <linux/kthread.h>
25#include <linux/netlink.h>
26#include "audit.h"
27
28/* There are three lists of rules -- one to search at task creation
29 * time, one to search at syscall entry time, and another to search at
30 * syscall exit time. */
31struct list_head audit_filter_list[AUDIT_NR_FILTERS] = {
32 LIST_HEAD_INIT(audit_filter_list[0]),
33 LIST_HEAD_INIT(audit_filter_list[1]),
34 LIST_HEAD_INIT(audit_filter_list[2]),
35 LIST_HEAD_INIT(audit_filter_list[3]),
36 LIST_HEAD_INIT(audit_filter_list[4]),
37 LIST_HEAD_INIT(audit_filter_list[5]),
38#if AUDIT_NR_FILTERS != 6
39#error Fix audit_filter_list initialiser
40#endif
41};
42
43/* Copy rule from user-space to kernel-space. Called from
44 * audit_add_rule during AUDIT_ADD. */
45static inline int audit_copy_rule(struct audit_rule *d, struct audit_rule *s)
46{
47 int i;
48
49 if (s->action != AUDIT_NEVER
50 && s->action != AUDIT_POSSIBLE
51 && s->action != AUDIT_ALWAYS)
52 return -1;
53 if (s->field_count < 0 || s->field_count > AUDIT_MAX_FIELDS)
54 return -1;
55 if ((s->flags & ~AUDIT_FILTER_PREPEND) >= AUDIT_NR_FILTERS)
56 return -1;
57
58 d->flags = s->flags;
59 d->action = s->action;
60 d->field_count = s->field_count;
61 for (i = 0; i < d->field_count; i++) {
62 d->fields[i] = s->fields[i];
63 d->values[i] = s->values[i];
64 }
65 for (i = 0; i < AUDIT_BITMASK_SIZE; i++) d->mask[i] = s->mask[i];
66 return 0;
67}
68
69/* Check to see if two rules are identical. It is called from
70 * audit_add_rule during AUDIT_ADD and
71 * audit_del_rule during AUDIT_DEL. */
72static inline int audit_compare_rule(struct audit_rule *a, struct audit_rule *b)
73{
74 int i;
75
76 if (a->flags != b->flags)
77 return 1;
78
79 if (a->action != b->action)
80 return 1;
81
82 if (a->field_count != b->field_count)
83 return 1;
84
85 for (i = 0; i < a->field_count; i++) {
86 if (a->fields[i] != b->fields[i]
87 || a->values[i] != b->values[i])
88 return 1;
89 }
90
91 for (i = 0; i < AUDIT_BITMASK_SIZE; i++)
92 if (a->mask[i] != b->mask[i])
93 return 1;
94
95 return 0;
96}
97
98/* Note that audit_add_rule and audit_del_rule are called via
99 * audit_receive() in audit.c, and are protected by
100 * audit_netlink_sem. */
101static inline int audit_add_rule(struct audit_rule *rule,
102 struct list_head *list)
103{
104 struct audit_entry *entry;
105 int i;
106
107 /* Do not use the _rcu iterator here, since this is the only
108 * addition routine. */
109 list_for_each_entry(entry, list, list) {
110 if (!audit_compare_rule(rule, &entry->rule)) {
111 return -EEXIST;
112 }
113 }
114
115 for (i = 0; i < rule->field_count; i++) {
116 if (rule->fields[i] & AUDIT_UNUSED_BITS)
117 return -EINVAL;
118 if ( rule->fields[i] & AUDIT_NEGATE )
119 rule->fields[i] |= AUDIT_NOT_EQUAL;
120 else if ( (rule->fields[i] & AUDIT_OPERATORS) == 0 )
121 rule->fields[i] |= AUDIT_EQUAL;
122 rule->fields[i] &= (~AUDIT_NEGATE);
123 }
124
125 if (!(entry = kmalloc(sizeof(*entry), GFP_KERNEL)))
126 return -ENOMEM;
127 if (audit_copy_rule(&entry->rule, rule)) {
128 kfree(entry);
129 return -EINVAL;
130 }
131
132 if (entry->rule.flags & AUDIT_FILTER_PREPEND) {
133 entry->rule.flags &= ~AUDIT_FILTER_PREPEND;
134 list_add_rcu(&entry->list, list);
135 } else {
136 list_add_tail_rcu(&entry->list, list);
137 }
138
139 return 0;
140}
141
142static inline void audit_free_rule(struct rcu_head *head)
143{
144 struct audit_entry *e = container_of(head, struct audit_entry, rcu);
145 kfree(e);
146}
147
148/* Note that audit_add_rule and audit_del_rule are called via
149 * audit_receive() in audit.c, and are protected by
150 * audit_netlink_sem. */
151static inline int audit_del_rule(struct audit_rule *rule,
152 struct list_head *list)
153{
154 struct audit_entry *e;
155
156 /* Do not use the _rcu iterator here, since this is the only
157 * deletion routine. */
158 list_for_each_entry(e, list, list) {
159 if (!audit_compare_rule(rule, &e->rule)) {
160 list_del_rcu(&e->list);
161 call_rcu(&e->rcu, audit_free_rule);
162 return 0;
163 }
164 }
165 return -ENOENT; /* No matching rule */
166}
167
168static int audit_list_rules(void *_dest)
169{
170 int pid, seq;
171 int *dest = _dest;
172 struct audit_entry *entry;
173 int i;
174
175 pid = dest[0];
176 seq = dest[1];
177 kfree(dest);
178
179 down(&audit_netlink_sem);
180
181 /* The *_rcu iterators not needed here because we are
182 always called with audit_netlink_sem held. */
183 for (i=0; i<AUDIT_NR_FILTERS; i++) {
184 list_for_each_entry(entry, &audit_filter_list[i], list)
185 audit_send_reply(pid, seq, AUDIT_LIST, 0, 1,
186 &entry->rule, sizeof(entry->rule));
187 }
188 audit_send_reply(pid, seq, AUDIT_LIST, 1, 1, NULL, 0);
189
190 up(&audit_netlink_sem);
191 return 0;
192}
193
194/**
195 * audit_receive_filter - apply all rules to the specified message type
196 * @type: audit message type
197 * @pid: target pid for netlink audit messages
198 * @uid: target uid for netlink audit messages
199 * @seq: netlink audit message sequence (serial) number
200 * @data: payload data
201 * @loginuid: loginuid of sender
202 */
203int audit_receive_filter(int type, int pid, int uid, int seq, void *data,
204 uid_t loginuid)
205{
206 struct task_struct *tsk;
207 int *dest;
208 int err = 0;
209 unsigned listnr;
210
211 switch (type) {
212 case AUDIT_LIST:
213 /* We can't just spew out the rules here because we might fill
214 * the available socket buffer space and deadlock waiting for
215 * auditctl to read from it... which isn't ever going to
216 * happen if we're actually running in the context of auditctl
217 * trying to _send_ the stuff */
218
219 dest = kmalloc(2 * sizeof(int), GFP_KERNEL);
220 if (!dest)
221 return -ENOMEM;
222 dest[0] = pid;
223 dest[1] = seq;
224
225 tsk = kthread_run(audit_list_rules, dest, "audit_list_rules");
226 if (IS_ERR(tsk)) {
227 kfree(dest);
228 err = PTR_ERR(tsk);
229 }
230 break;
231 case AUDIT_ADD:
232 listnr = ((struct audit_rule *)data)->flags & ~AUDIT_FILTER_PREPEND;
233 switch(listnr) {
234 default:
235 return -EINVAL;
236
237 case AUDIT_FILTER_USER:
238 case AUDIT_FILTER_TYPE:
239#ifdef CONFIG_AUDITSYSCALL
240 case AUDIT_FILTER_ENTRY:
241 case AUDIT_FILTER_EXIT:
242 case AUDIT_FILTER_TASK:
243#endif
244 ;
245 }
246 err = audit_add_rule(data, &audit_filter_list[listnr]);
247 if (!err)
248 audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE,
249 "auid=%u added an audit rule\n", loginuid);
250 break;
251 case AUDIT_DEL:
252 listnr =((struct audit_rule *)data)->flags & ~AUDIT_FILTER_PREPEND;
253 if (listnr >= AUDIT_NR_FILTERS)
254 return -EINVAL;
255
256 err = audit_del_rule(data, &audit_filter_list[listnr]);
257 if (!err)
258 audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE,
259 "auid=%u removed an audit rule\n", loginuid);
260 break;
261 default:
262 return -EINVAL;
263 }
264
265 return err;
266}
267
268int audit_comparator(const u32 left, const u32 op, const u32 right)
269{
270 switch (op) {
271 case AUDIT_EQUAL:
272 return (left == right);
273 case AUDIT_NOT_EQUAL:
274 return (left != right);
275 case AUDIT_LESS_THAN:
276 return (left < right);
277 case AUDIT_LESS_THAN_OR_EQUAL:
278 return (left <= right);
279 case AUDIT_GREATER_THAN:
280 return (left > right);
281 case AUDIT_GREATER_THAN_OR_EQUAL:
282 return (left >= right);
283 default:
284 return -EINVAL;
285 }
286}
287
288
289
290static int audit_filter_user_rules(struct netlink_skb_parms *cb,
291 struct audit_rule *rule,
292 enum audit_state *state)
293{
294 int i;
295
296 for (i = 0; i < rule->field_count; i++) {
297 u32 field = rule->fields[i] & ~AUDIT_OPERATORS;
298 u32 op = rule->fields[i] & AUDIT_OPERATORS;
299 u32 value = rule->values[i];
300 int result = 0;
301
302 switch (field) {
303 case AUDIT_PID:
304 result = audit_comparator(cb->creds.pid, op, value);
305 break;
306 case AUDIT_UID:
307 result = audit_comparator(cb->creds.uid, op, value);
308 break;
309 case AUDIT_GID:
310 result = audit_comparator(cb->creds.gid, op, value);
311 break;
312 case AUDIT_LOGINUID:
313 result = audit_comparator(cb->loginuid, op, value);
314 break;
315 }
316
317 if (!result)
318 return 0;
319 }
320 switch (rule->action) {
321 case AUDIT_NEVER: *state = AUDIT_DISABLED; break;
322 case AUDIT_POSSIBLE: *state = AUDIT_BUILD_CONTEXT; break;
323 case AUDIT_ALWAYS: *state = AUDIT_RECORD_CONTEXT; break;
324 }
325 return 1;
326}
327
328int audit_filter_user(struct netlink_skb_parms *cb, int type)
329{
330 struct audit_entry *e;
331 enum audit_state state;
332 int ret = 1;
333
334 rcu_read_lock();
335 list_for_each_entry_rcu(e, &audit_filter_list[AUDIT_FILTER_USER], list) {
336 if (audit_filter_user_rules(cb, &e->rule, &state)) {
337 if (state == AUDIT_DISABLED)
338 ret = 0;
339 break;
340 }
341 }
342 rcu_read_unlock();
343
344 return ret; /* Audit by default */
345}
346
347int audit_filter_type(int type)
348{
349 struct audit_entry *e;
350 int result = 0;
351
352 rcu_read_lock();
353 if (list_empty(&audit_filter_list[AUDIT_FILTER_TYPE]))
354 goto unlock_and_return;
355
356 list_for_each_entry_rcu(e, &audit_filter_list[AUDIT_FILTER_TYPE],
357 list) {
358 struct audit_rule *rule = &e->rule;
359 int i;
360 for (i = 0; i < rule->field_count; i++) {
361 u32 field = rule->fields[i] & ~AUDIT_OPERATORS;
362 u32 op = rule->fields[i] & AUDIT_OPERATORS;
363 u32 value = rule->values[i];
364 if ( field == AUDIT_MSGTYPE ) {
365 result = audit_comparator(type, op, value);
366 if (!result)
367 break;
368 }
369 }
370 if (result)
371 goto unlock_and_return;
372 }
373unlock_and_return:
374 rcu_read_unlock();
375 return result;
376}
377
378
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