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
16struct 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
25static 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
44err_buf:
45	kfree(buf);
46err:
47	return NULL;
48}
49
50static 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
57static 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
63static 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 */
94static 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 */
112void 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 */
133void 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 */
142void 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(&current->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(&current->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 */
181int 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 */
219static 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(&current->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(&current->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(&current->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(&current->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 */
268void tty_audit_add_data(struct tty_struct *tty, const void *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(&current->sighand->siglock, flags);
280	audit_log_tty_passwd = current->signal->audit_tty_log_passwd;
281	spin_unlock_irqrestore(&current->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 */
325void tty_audit_push(struct tty_struct *tty)
326{
327	struct tty_audit_buf *buf;
328	unsigned long flags;
329
330	spin_lock_irqsave(&current->sighand->siglock, flags);
331	if (likely(!current->signal->audit_tty)) {
332		spin_unlock_irqrestore(&current->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(&current->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