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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 struct mutex mutex; /* Protects all data below */
18 dev_t dev; /* 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
24static struct tty_audit_buf *tty_audit_buf_ref(void)
25{
26 struct tty_audit_buf *buf;
27
28 buf = current->signal->tty_audit_buf;
29 WARN_ON(buf == ERR_PTR(-ESRCH));
30 return buf;
31}
32
33static struct tty_audit_buf *tty_audit_buf_alloc(void)
34{
35 struct tty_audit_buf *buf;
36
37 buf = kmalloc(sizeof(*buf), GFP_KERNEL);
38 if (!buf)
39 goto err;
40 buf->data = kmalloc(N_TTY_BUF_SIZE, GFP_KERNEL);
41 if (!buf->data)
42 goto err_buf;
43 mutex_init(&buf->mutex);
44 buf->dev = MKDEV(0, 0);
45 buf->icanon = 0;
46 buf->valid = 0;
47 return buf;
48
49err_buf:
50 kfree(buf);
51err:
52 return NULL;
53}
54
55static void tty_audit_buf_free(struct tty_audit_buf *buf)
56{
57 WARN_ON(buf->valid != 0);
58 kfree(buf->data);
59 kfree(buf);
60}
61
62static void tty_audit_log(const char *description, dev_t dev,
63 unsigned char *data, size_t size)
64{
65 struct audit_buffer *ab;
66 struct task_struct *tsk = current;
67 pid_t pid = task_pid_nr(tsk);
68 uid_t uid = from_kuid(&init_user_ns, task_uid(tsk));
69 uid_t loginuid = from_kuid(&init_user_ns, audit_get_loginuid(tsk));
70 unsigned int sessionid = audit_get_sessionid(tsk);
71
72 ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_TTY);
73 if (ab) {
74 char name[sizeof(tsk->comm)];
75
76 audit_log_format(ab, "%s pid=%u uid=%u auid=%u ses=%u major=%d"
77 " minor=%d comm=", description, pid, uid,
78 loginuid, sessionid, MAJOR(dev), MINOR(dev));
79 get_task_comm(name, tsk);
80 audit_log_untrustedstring(ab, name);
81 audit_log_format(ab, " data=");
82 audit_log_n_hex(ab, data, size);
83 audit_log_end(ab);
84 }
85}
86
87/**
88 * tty_audit_buf_push - Push buffered data out
89 *
90 * Generate an audit message from the contents of @buf, which is owned by
91 * the current task. @buf->mutex must be locked.
92 */
93static void tty_audit_buf_push(struct tty_audit_buf *buf)
94{
95 if (buf->valid == 0)
96 return;
97 if (audit_enabled == 0) {
98 buf->valid = 0;
99 return;
100 }
101 tty_audit_log("tty", buf->dev, buf->data, buf->valid);
102 buf->valid = 0;
103}
104
105/**
106 * tty_audit_exit - Handle a task exit
107 *
108 * Make sure all buffered data is written out and deallocate the buffer.
109 * Only needs to be called if current->signal->tty_audit_buf != %NULL.
110 *
111 * The process is single-threaded at this point; no other threads share
112 * current->signal.
113 */
114void tty_audit_exit(void)
115{
116 struct tty_audit_buf *buf;
117
118 buf = xchg(¤t->signal->tty_audit_buf, ERR_PTR(-ESRCH));
119 if (!buf)
120 return;
121
122 tty_audit_buf_push(buf);
123 tty_audit_buf_free(buf);
124}
125
126/**
127 * tty_audit_fork - Copy TTY audit state for a new task
128 *
129 * Set up TTY audit state in @sig from current. @sig needs no locking.
130 */
131void tty_audit_fork(struct signal_struct *sig)
132{
133 sig->audit_tty = current->signal->audit_tty;
134}
135
136/**
137 * tty_audit_tiocsti - Log TIOCSTI
138 */
139void tty_audit_tiocsti(struct tty_struct *tty, char ch)
140{
141 dev_t dev;
142
143 dev = MKDEV(tty->driver->major, tty->driver->minor_start) + tty->index;
144 if (tty_audit_push())
145 return;
146
147 if (audit_enabled)
148 tty_audit_log("ioctl=TIOCSTI", dev, &ch, 1);
149}
150
151/**
152 * tty_audit_push - Flush current's pending audit data
153 *
154 * Returns 0 if success, -EPERM if tty audit is disabled
155 */
156int tty_audit_push(void)
157{
158 struct tty_audit_buf *buf;
159
160 if (~current->signal->audit_tty & AUDIT_TTY_ENABLE)
161 return -EPERM;
162
163 buf = tty_audit_buf_ref();
164 if (!IS_ERR_OR_NULL(buf)) {
165 mutex_lock(&buf->mutex);
166 tty_audit_buf_push(buf);
167 mutex_unlock(&buf->mutex);
168 }
169 return 0;
170}
171
172/**
173 * tty_audit_buf_get - Get an audit buffer.
174 *
175 * Get an audit buffer, allocate it if necessary. Return %NULL
176 * if out of memory or ERR_PTR(-ESRCH) if tty_audit_exit() has already
177 * occurred. Otherwise, return a new reference to the buffer.
178 */
179static struct tty_audit_buf *tty_audit_buf_get(void)
180{
181 struct tty_audit_buf *buf;
182
183 buf = tty_audit_buf_ref();
184 if (buf)
185 return buf;
186
187 buf = tty_audit_buf_alloc();
188 if (buf == NULL) {
189 audit_log_lost("out of memory in TTY auditing");
190 return NULL;
191 }
192
193 /* Race to use this buffer, free it if another wins */
194 if (cmpxchg(¤t->signal->tty_audit_buf, NULL, buf) != NULL)
195 tty_audit_buf_free(buf);
196 return tty_audit_buf_ref();
197}
198
199/**
200 * tty_audit_add_data - Add data for TTY auditing.
201 *
202 * Audit @data of @size from @tty, if necessary.
203 */
204void tty_audit_add_data(struct tty_struct *tty, const void *data, size_t size)
205{
206 struct tty_audit_buf *buf;
207 unsigned int icanon = !!L_ICANON(tty);
208 unsigned int audit_tty;
209 dev_t dev;
210
211 audit_tty = READ_ONCE(current->signal->audit_tty);
212 if (~audit_tty & AUDIT_TTY_ENABLE)
213 return;
214
215 if (unlikely(size == 0))
216 return;
217
218 if (tty->driver->type == TTY_DRIVER_TYPE_PTY
219 && tty->driver->subtype == PTY_TYPE_MASTER)
220 return;
221
222 if ((~audit_tty & AUDIT_TTY_LOG_PASSWD) && icanon && !L_ECHO(tty))
223 return;
224
225 buf = tty_audit_buf_get();
226 if (IS_ERR_OR_NULL(buf))
227 return;
228
229 mutex_lock(&buf->mutex);
230 dev = MKDEV(tty->driver->major, tty->driver->minor_start) + tty->index;
231 if (buf->dev != dev || buf->icanon != icanon) {
232 tty_audit_buf_push(buf);
233 buf->dev = dev;
234 buf->icanon = icanon;
235 }
236 do {
237 size_t run;
238
239 run = N_TTY_BUF_SIZE - buf->valid;
240 if (run > size)
241 run = size;
242 memcpy(buf->data + buf->valid, data, run);
243 buf->valid += run;
244 data += run;
245 size -= run;
246 if (buf->valid == N_TTY_BUF_SIZE)
247 tty_audit_buf_push(buf);
248 } while (size != 0);
249 mutex_unlock(&buf->mutex);
250}
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(¤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 */
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(¤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 */
268void 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 */
325void 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}