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/slab.h>
14 #include <linux/tty.h>
15
16 struct tty_audit_buf {
17 atomic_t count;
18 struct mutex mutex; /* Protects all data below */
19 int major, minor; /* The TTY which the data is from */
20 unsigned icanon:1;
21 size_t valid;
22 unsigned char *data; /* Allocated size N_TTY_BUF_SIZE */
23 };
24
tty_audit_buf_alloc(int major,int minor,unsigned icanon)25 static struct tty_audit_buf *tty_audit_buf_alloc(int major, int minor,
26 unsigned icanon)
27 {
28 struct tty_audit_buf *buf;
29
30 buf = kmalloc(sizeof(*buf), GFP_KERNEL);
31 if (!buf)
32 goto err;
33 buf->data = kmalloc(N_TTY_BUF_SIZE, GFP_KERNEL);
34 if (!buf->data)
35 goto err_buf;
36 atomic_set(&buf->count, 1);
37 mutex_init(&buf->mutex);
38 buf->major = major;
39 buf->minor = minor;
40 buf->icanon = icanon;
41 buf->valid = 0;
42 return buf;
43
44 err_buf:
45 kfree(buf);
46 err:
47 return NULL;
48 }
49
tty_audit_buf_free(struct tty_audit_buf * buf)50 static void tty_audit_buf_free(struct tty_audit_buf *buf)
51 {
52 WARN_ON(buf->valid != 0);
53 kfree(buf->data);
54 kfree(buf);
55 }
56
tty_audit_buf_put(struct tty_audit_buf * buf)57 static void tty_audit_buf_put(struct tty_audit_buf *buf)
58 {
59 if (atomic_dec_and_test(&buf->count))
60 tty_audit_buf_free(buf);
61 }
62
tty_audit_log(const char * description,int major,int minor,unsigned char * data,size_t size)63 static void tty_audit_log(const char *description, int major, int minor,
64 unsigned char *data, size_t size)
65 {
66 struct audit_buffer *ab;
67 struct task_struct *tsk = current;
68 pid_t pid = task_pid_nr(tsk);
69 uid_t uid = from_kuid(&init_user_ns, task_uid(tsk));
70 uid_t loginuid = from_kuid(&init_user_ns, audit_get_loginuid(tsk));
71 unsigned int sessionid = audit_get_sessionid(tsk);
72
73 ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_TTY);
74 if (ab) {
75 char name[sizeof(tsk->comm)];
76
77 audit_log_format(ab, "%s pid=%u uid=%u auid=%u ses=%u major=%d"
78 " minor=%d comm=", description, pid, uid,
79 loginuid, sessionid, major, minor);
80 get_task_comm(name, tsk);
81 audit_log_untrustedstring(ab, name);
82 audit_log_format(ab, " data=");
83 audit_log_n_hex(ab, data, size);
84 audit_log_end(ab);
85 }
86 }
87
88 /**
89 * tty_audit_buf_push - Push buffered data out
90 *
91 * Generate an audit message from the contents of @buf, which is owned by
92 * the current task. @buf->mutex must be locked.
93 */
tty_audit_buf_push(struct tty_audit_buf * buf)94 static void tty_audit_buf_push(struct tty_audit_buf *buf)
95 {
96 if (buf->valid == 0)
97 return;
98 if (audit_enabled == 0) {
99 buf->valid = 0;
100 return;
101 }
102 tty_audit_log("tty", buf->major, buf->minor, buf->data, buf->valid);
103 buf->valid = 0;
104 }
105
106 /**
107 * tty_audit_exit - Handle a task exit
108 *
109 * Make sure all buffered data is written out and deallocate the buffer.
110 * Only needs to be called if current->signal->tty_audit_buf != %NULL.
111 */
tty_audit_exit(void)112 void tty_audit_exit(void)
113 {
114 struct tty_audit_buf *buf;
115
116 buf = current->signal->tty_audit_buf;
117 current->signal->tty_audit_buf = NULL;
118 if (!buf)
119 return;
120
121 mutex_lock(&buf->mutex);
122 tty_audit_buf_push(buf);
123 mutex_unlock(&buf->mutex);
124
125 tty_audit_buf_put(buf);
126 }
127
128 /**
129 * tty_audit_fork - Copy TTY audit state for a new task
130 *
131 * Set up TTY audit state in @sig from current. @sig needs no locking.
132 */
tty_audit_fork(struct signal_struct * sig)133 void tty_audit_fork(struct signal_struct *sig)
134 {
135 sig->audit_tty = current->signal->audit_tty;
136 sig->audit_tty_log_passwd = current->signal->audit_tty_log_passwd;
137 }
138
139 /**
140 * tty_audit_tiocsti - Log TIOCSTI
141 */
tty_audit_tiocsti(struct tty_struct * tty,char ch)142 void tty_audit_tiocsti(struct tty_struct *tty, char ch)
143 {
144 struct tty_audit_buf *buf;
145 int major, minor, should_audit;
146 unsigned long flags;
147
148 spin_lock_irqsave(¤t->sighand->siglock, flags);
149 should_audit = current->signal->audit_tty;
150 buf = current->signal->tty_audit_buf;
151 if (buf)
152 atomic_inc(&buf->count);
153 spin_unlock_irqrestore(¤t->sighand->siglock, flags);
154
155 major = tty->driver->major;
156 minor = tty->driver->minor_start + tty->index;
157 if (buf) {
158 mutex_lock(&buf->mutex);
159 if (buf->major == major && buf->minor == minor)
160 tty_audit_buf_push(buf);
161 mutex_unlock(&buf->mutex);
162 tty_audit_buf_put(buf);
163 }
164
165 if (should_audit && audit_enabled) {
166 kuid_t auid;
167 unsigned int sessionid;
168
169 auid = audit_get_loginuid(current);
170 sessionid = audit_get_sessionid(current);
171 tty_audit_log("ioctl=TIOCSTI", major, minor, &ch, 1);
172 }
173 }
174
175 /**
176 * tty_audit_push_current - Flush current's pending audit data
177 *
178 * Try to lock sighand and get a reference to the tty audit buffer if available.
179 * Flush the buffer or return an appropriate error code.
180 */
tty_audit_push_current(void)181 int tty_audit_push_current(void)
182 {
183 struct tty_audit_buf *buf = ERR_PTR(-EPERM);
184 struct task_struct *tsk = current;
185 unsigned long flags;
186
187 if (!lock_task_sighand(tsk, &flags))
188 return -ESRCH;
189
190 if (tsk->signal->audit_tty) {
191 buf = tsk->signal->tty_audit_buf;
192 if (buf)
193 atomic_inc(&buf->count);
194 }
195 unlock_task_sighand(tsk, &flags);
196
197 /*
198 * Return 0 when signal->audit_tty set
199 * but tsk->signal->tty_audit_buf == NULL.
200 */
201 if (!buf || IS_ERR(buf))
202 return PTR_ERR(buf);
203
204 mutex_lock(&buf->mutex);
205 tty_audit_buf_push(buf);
206 mutex_unlock(&buf->mutex);
207
208 tty_audit_buf_put(buf);
209 return 0;
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 */
tty_audit_buf_get(struct tty_struct * tty,unsigned icanon)219 static struct tty_audit_buf *tty_audit_buf_get(struct tty_struct *tty,
220 unsigned icanon)
221 {
222 struct tty_audit_buf *buf, *buf2;
223 unsigned long flags;
224
225 buf = NULL;
226 buf2 = NULL;
227 spin_lock_irqsave(¤t->sighand->siglock, flags);
228 if (likely(!current->signal->audit_tty))
229 goto out;
230 buf = current->signal->tty_audit_buf;
231 if (buf) {
232 atomic_inc(&buf->count);
233 goto out;
234 }
235 spin_unlock_irqrestore(¤t->sighand->siglock, flags);
236
237 buf2 = tty_audit_buf_alloc(tty->driver->major,
238 tty->driver->minor_start + tty->index,
239 icanon);
240 if (buf2 == NULL) {
241 audit_log_lost("out of memory in TTY auditing");
242 return NULL;
243 }
244
245 spin_lock_irqsave(¤t->sighand->siglock, flags);
246 if (!current->signal->audit_tty)
247 goto out;
248 buf = current->signal->tty_audit_buf;
249 if (!buf) {
250 current->signal->tty_audit_buf = buf2;
251 buf = buf2;
252 buf2 = NULL;
253 }
254 atomic_inc(&buf->count);
255 /* Fall through */
256 out:
257 spin_unlock_irqrestore(¤t->sighand->siglock, flags);
258 if (buf2)
259 tty_audit_buf_free(buf2);
260 return buf;
261 }
262
263 /**
264 * tty_audit_add_data - Add data for TTY auditing.
265 *
266 * Audit @data of @size from @tty, if necessary.
267 */
tty_audit_add_data(struct tty_struct * tty,unsigned char * data,size_t size,unsigned icanon)268 void tty_audit_add_data(struct tty_struct *tty, unsigned char *data,
269 size_t size, unsigned icanon)
270 {
271 struct tty_audit_buf *buf;
272 int major, minor;
273 int audit_log_tty_passwd;
274 unsigned long flags;
275
276 if (unlikely(size == 0))
277 return;
278
279 spin_lock_irqsave(¤t->sighand->siglock, flags);
280 audit_log_tty_passwd = current->signal->audit_tty_log_passwd;
281 spin_unlock_irqrestore(¤t->sighand->siglock, flags);
282 if (!audit_log_tty_passwd && icanon && !L_ECHO(tty))
283 return;
284
285 if (tty->driver->type == TTY_DRIVER_TYPE_PTY
286 && tty->driver->subtype == PTY_TYPE_MASTER)
287 return;
288
289 buf = tty_audit_buf_get(tty, icanon);
290 if (!buf)
291 return;
292
293 mutex_lock(&buf->mutex);
294 major = tty->driver->major;
295 minor = tty->driver->minor_start + tty->index;
296 if (buf->major != major || buf->minor != minor
297 || buf->icanon != icanon) {
298 tty_audit_buf_push(buf);
299 buf->major = major;
300 buf->minor = minor;
301 buf->icanon = icanon;
302 }
303 do {
304 size_t run;
305
306 run = N_TTY_BUF_SIZE - buf->valid;
307 if (run > size)
308 run = size;
309 memcpy(buf->data + buf->valid, data, run);
310 buf->valid += run;
311 data += run;
312 size -= run;
313 if (buf->valid == N_TTY_BUF_SIZE)
314 tty_audit_buf_push(buf);
315 } while (size != 0);
316 mutex_unlock(&buf->mutex);
317 tty_audit_buf_put(buf);
318 }
319
320 /**
321 * tty_audit_push - Push buffered data out
322 *
323 * Make sure no audit data is pending for @tty on the current process.
324 */
tty_audit_push(struct tty_struct * tty)325 void tty_audit_push(struct tty_struct *tty)
326 {
327 struct tty_audit_buf *buf;
328 unsigned long flags;
329
330 spin_lock_irqsave(¤t->sighand->siglock, flags);
331 if (likely(!current->signal->audit_tty)) {
332 spin_unlock_irqrestore(¤t->sighand->siglock, flags);
333 return;
334 }
335 buf = current->signal->tty_audit_buf;
336 if (buf)
337 atomic_inc(&buf->count);
338 spin_unlock_irqrestore(¤t->sighand->siglock, flags);
339
340 if (buf) {
341 int major, minor;
342
343 major = tty->driver->major;
344 minor = tty->driver->minor_start + tty->index;
345 mutex_lock(&buf->mutex);
346 if (buf->major == major && buf->minor == minor)
347 tty_audit_buf_push(buf);
348 mutex_unlock(&buf->mutex);
349 tty_audit_buf_put(buf);
350 }
351 }
352