1 /*
2 * Creating audit events from TTY input.
3 *
4 * Copyright (C) 2007 Red Hat, Inc. All rights reserved. This copyrighted
5 * material is made available to anyone wishing to use, modify, copy, or
6 * redistribute it subject to the terms and conditions of the GNU General
7 * Public License v.2.
8 *
9 * Authors: Miloslav Trmac <mitr@redhat.com>
10 */
11
12 #include <linux/audit.h>
13 #include <linux/tty.h>
14
15 struct tty_audit_buf {
16 atomic_t count;
17 struct mutex mutex; /* Protects all data below */
18 int major, minor; /* The TTY which the data is from */
19 unsigned icanon:1;
20 size_t valid;
21 unsigned char *data; /* Allocated size N_TTY_BUF_SIZE */
22 };
23
24 static struct tty_audit_buf *tty_audit_buf_alloc(int major, int minor,
25 int icanon)
26 {
27 struct tty_audit_buf *buf;
28
29 buf = kmalloc(sizeof(*buf), GFP_KERNEL);
30 if (!buf)
31 goto err;
32 buf->data = kmalloc(N_TTY_BUF_SIZE, GFP_KERNEL);
33 if (!buf->data)
34 goto err_buf;
35 atomic_set(&buf->count, 1);
36 mutex_init(&buf->mutex);
37 buf->major = major;
38 buf->minor = minor;
39 buf->icanon = icanon;
40 buf->valid = 0;
41 return buf;
42
43 err_buf:
44 kfree(buf);
45 err:
46 return NULL;
47 }
48
49 static void tty_audit_buf_free(struct tty_audit_buf *buf)
50 {
51 WARN_ON(buf->valid != 0);
52 kfree(buf->data);
53 kfree(buf);
54 }
55
56 static void tty_audit_buf_put(struct tty_audit_buf *buf)
57 {
58 if (atomic_dec_and_test(&buf->count))
59 tty_audit_buf_free(buf);
60 }
61
62 static void tty_audit_log(const char *description, struct task_struct *tsk,
63 uid_t loginuid, unsigned sessionid, int major,
64 int minor, unsigned char *data, size_t size)
65 {
66 struct audit_buffer *ab;
67
68 ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_TTY);
69 if (ab) {
70 char name[sizeof(tsk->comm)];
71 uid_t uid = task_uid(tsk);
72
73 audit_log_format(ab, "%s pid=%u uid=%u auid=%u ses=%u "
74 "major=%d minor=%d comm=", description,
75 tsk->pid, uid, loginuid, sessionid,
76 major, minor);
77 get_task_comm(name, tsk);
78 audit_log_untrustedstring(ab, name);
79 audit_log_format(ab, " data=");
80 audit_log_n_hex(ab, data, size);
81 audit_log_end(ab);
82 }
83 }
84
85 /**
86 * tty_audit_buf_push - Push buffered data out
87 *
88 * Generate an audit message from the contents of @buf, which is owned by
89 * @tsk with @loginuid. @buf->mutex must be locked.
90 */
91 static void tty_audit_buf_push(struct task_struct *tsk, uid_t loginuid,
92 unsigned int sessionid,
93 struct tty_audit_buf *buf)
94 {
95 if (buf->valid == 0)
96 return;
97 if (audit_enabled == 0)
98 return;
99 tty_audit_log("tty", tsk, loginuid, sessionid, buf->major, buf->minor,
100 buf->data, buf->valid);
101 buf->valid = 0;
102 }
103
104 /**
105 * tty_audit_buf_push_current - Push buffered data out
106 *
107 * Generate an audit message from the contents of @buf, which is owned by
108 * the current task. @buf->mutex must be locked.
109 */
110 static void tty_audit_buf_push_current(struct tty_audit_buf *buf)
111 {
112 uid_t auid = audit_get_loginuid(current);
113 unsigned int sessionid = audit_get_sessionid(current);
114 tty_audit_buf_push(current, auid, sessionid, buf);
115 }
116
117 /**
118 * tty_audit_exit - Handle a task exit
119 *
120 * Make sure all buffered data is written out and deallocate the buffer.
121 * Only needs to be called if current->signal->tty_audit_buf != %NULL.
122 */
123 void tty_audit_exit(void)
124 {
125 struct tty_audit_buf *buf;
126
127 spin_lock_irq(¤t->sighand->siglock);
128 buf = current->signal->tty_audit_buf;
129 current->signal->tty_audit_buf = NULL;
130 spin_unlock_irq(¤t->sighand->siglock);
131 if (!buf)
132 return;
133
134 mutex_lock(&buf->mutex);
135 tty_audit_buf_push_current(buf);
136 mutex_unlock(&buf->mutex);
137
138 tty_audit_buf_put(buf);
139 }
140
141 /**
142 * tty_audit_fork - Copy TTY audit state for a new task
143 *
144 * Set up TTY audit state in @sig from current. @sig needs no locking.
145 */
146 void tty_audit_fork(struct signal_struct *sig)
147 {
148 spin_lock_irq(¤t->sighand->siglock);
149 sig->audit_tty = current->signal->audit_tty;
150 spin_unlock_irq(¤t->sighand->siglock);
151 sig->tty_audit_buf = NULL;
152 }
153
154 /**
155 * tty_audit_tiocsti - Log TIOCSTI
156 */
157 void tty_audit_tiocsti(struct tty_struct *tty, char ch)
158 {
159 struct tty_audit_buf *buf;
160 int major, minor, should_audit;
161
162 spin_lock_irq(¤t->sighand->siglock);
163 should_audit = current->signal->audit_tty;
164 buf = current->signal->tty_audit_buf;
165 if (buf)
166 atomic_inc(&buf->count);
167 spin_unlock_irq(¤t->sighand->siglock);
168
169 major = tty->driver->major;
170 minor = tty->driver->minor_start + tty->index;
171 if (buf) {
172 mutex_lock(&buf->mutex);
173 if (buf->major == major && buf->minor == minor)
174 tty_audit_buf_push_current(buf);
175 mutex_unlock(&buf->mutex);
176 tty_audit_buf_put(buf);
177 }
178
179 if (should_audit && audit_enabled) {
180 uid_t auid;
181 unsigned int sessionid;
182
183 auid = audit_get_loginuid(current);
184 sessionid = audit_get_sessionid(current);
185 tty_audit_log("ioctl=TIOCSTI", current, auid, sessionid, major,
186 minor, &ch, 1);
187 }
188 }
189
190 /**
191 * tty_audit_push_task - Flush task's pending audit data
192 */
193 void tty_audit_push_task(struct task_struct *tsk, uid_t loginuid, u32 sessionid)
194 {
195 struct tty_audit_buf *buf;
196
197 spin_lock_irq(&tsk->sighand->siglock);
198 buf = tsk->signal->tty_audit_buf;
199 if (buf)
200 atomic_inc(&buf->count);
201 spin_unlock_irq(&tsk->sighand->siglock);
202 if (!buf)
203 return;
204
205 mutex_lock(&buf->mutex);
206 tty_audit_buf_push(tsk, loginuid, sessionid, buf);
207 mutex_unlock(&buf->mutex);
208
209 tty_audit_buf_put(buf);
210 }
211
212 /**
213 * tty_audit_buf_get - Get an audit buffer.
214 *
215 * Get an audit buffer for @tty, allocate it if necessary. Return %NULL
216 * if TTY auditing is disabled or out of memory. Otherwise, return a new
217 * reference to the buffer.
218 */
219 static struct tty_audit_buf *tty_audit_buf_get(struct tty_struct *tty)
220 {
221 struct tty_audit_buf *buf, *buf2;
222
223 buf = NULL;
224 buf2 = NULL;
225 spin_lock_irq(¤t->sighand->siglock);
226 if (likely(!current->signal->audit_tty))
227 goto out;
228 buf = current->signal->tty_audit_buf;
229 if (buf) {
230 atomic_inc(&buf->count);
231 goto out;
232 }
233 spin_unlock_irq(¤t->sighand->siglock);
234
235 buf2 = tty_audit_buf_alloc(tty->driver->major,
236 tty->driver->minor_start + tty->index,
237 tty->icanon);
238 if (buf2 == NULL) {
239 audit_log_lost("out of memory in TTY auditing");
240 return NULL;
241 }
242
243 spin_lock_irq(¤t->sighand->siglock);
244 if (!current->signal->audit_tty)
245 goto out;
246 buf = current->signal->tty_audit_buf;
247 if (!buf) {
248 current->signal->tty_audit_buf = buf2;
249 buf = buf2;
250 buf2 = NULL;
251 }
252 atomic_inc(&buf->count);
253 /* Fall through */
254 out:
255 spin_unlock_irq(¤t->sighand->siglock);
256 if (buf2)
257 tty_audit_buf_free(buf2);
258 return buf;
259 }
260
261 /**
262 * tty_audit_add_data - Add data for TTY auditing.
263 *
264 * Audit @data of @size from @tty, if necessary.
265 */
266 void tty_audit_add_data(struct tty_struct *tty, unsigned char *data,
267 size_t size)
268 {
269 struct tty_audit_buf *buf;
270 int major, minor;
271
272 if (unlikely(size == 0))
273 return;
274
275 if (tty->driver->type == TTY_DRIVER_TYPE_PTY
276 && tty->driver->subtype == PTY_TYPE_MASTER)
277 return;
278
279 buf = tty_audit_buf_get(tty);
280 if (!buf)
281 return;
282
283 mutex_lock(&buf->mutex);
284 major = tty->driver->major;
285 minor = tty->driver->minor_start + tty->index;
286 if (buf->major != major || buf->minor != minor
287 || buf->icanon != tty->icanon) {
288 tty_audit_buf_push_current(buf);
289 buf->major = major;
290 buf->minor = minor;
291 buf->icanon = tty->icanon;
292 }
293 do {
294 size_t run;
295
296 run = N_TTY_BUF_SIZE - buf->valid;
297 if (run > size)
298 run = size;
299 memcpy(buf->data + buf->valid, data, run);
300 buf->valid += run;
301 data += run;
302 size -= run;
303 if (buf->valid == N_TTY_BUF_SIZE)
304 tty_audit_buf_push_current(buf);
305 } while (size != 0);
306 mutex_unlock(&buf->mutex);
307 tty_audit_buf_put(buf);
308 }
309
310 /**
311 * tty_audit_push - Push buffered data out
312 *
313 * Make sure no audit data is pending for @tty on the current process.
314 */
315 void tty_audit_push(struct tty_struct *tty)
316 {
317 struct tty_audit_buf *buf;
318
319 spin_lock_irq(¤t->sighand->siglock);
320 if (likely(!current->signal->audit_tty)) {
321 spin_unlock_irq(¤t->sighand->siglock);
322 return;
323 }
324 buf = current->signal->tty_audit_buf;
325 if (buf)
326 atomic_inc(&buf->count);
327 spin_unlock_irq(¤t->sighand->siglock);
328
329 if (buf) {
330 int major, minor;
331
332 major = tty->driver->major;
333 minor = tty->driver->minor_start + tty->index;
334 mutex_lock(&buf->mutex);
335 if (buf->major == major && buf->minor == minor)
336 tty_audit_buf_push_current(buf);
337 mutex_unlock(&buf->mutex);
338 tty_audit_buf_put(buf);
339 }
340 }
341
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