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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Creating audit events from TTY input.
4 *
5 * Copyright (C) 2007 Red Hat, Inc. All rights reserved.
6 *
7 * Authors: Miloslav Trmac <mitr@redhat.com>
8 */
9
10#include <linux/audit.h>
11#include <linux/slab.h>
12#include <linux/tty.h>
13#include "tty.h"
14
15struct tty_audit_buf {
16 struct mutex mutex; /* Protects all data below */
17 dev_t dev; /* The TTY which the data is from */
18 bool icanon;
19 size_t valid;
20 u8 *data; /* Allocated size N_TTY_BUF_SIZE */
21};
22
23static struct tty_audit_buf *tty_audit_buf_ref(void)
24{
25 struct tty_audit_buf *buf;
26
27 buf = current->signal->tty_audit_buf;
28 WARN_ON(buf == ERR_PTR(-ESRCH));
29 return buf;
30}
31
32static struct tty_audit_buf *tty_audit_buf_alloc(void)
33{
34 struct tty_audit_buf *buf;
35
36 buf = kzalloc(sizeof(*buf), GFP_KERNEL);
37 if (!buf)
38 goto err;
39
40 buf->data = kmalloc(N_TTY_BUF_SIZE, GFP_KERNEL);
41 if (!buf->data)
42 goto err_buf;
43
44 mutex_init(&buf->mutex);
45
46 return buf;
47
48err_buf:
49 kfree(buf);
50err:
51 return NULL;
52}
53
54static void tty_audit_buf_free(struct tty_audit_buf *buf)
55{
56 WARN_ON(buf->valid != 0);
57 kfree(buf->data);
58 kfree(buf);
59}
60
61static void tty_audit_log(const char *description, dev_t dev,
62 const u8 *data, size_t size)
63{
64 struct audit_buffer *ab;
65 pid_t pid = task_pid_nr(current);
66 uid_t uid = from_kuid(&init_user_ns, task_uid(current));
67 uid_t loginuid = from_kuid(&init_user_ns, audit_get_loginuid(current));
68 unsigned int sessionid = audit_get_sessionid(current);
69 char name[TASK_COMM_LEN];
70
71 ab = audit_log_start(audit_context(), GFP_KERNEL, AUDIT_TTY);
72 if (!ab)
73 return;
74
75 audit_log_format(ab, "%s pid=%u uid=%u auid=%u ses=%u major=%d minor=%d comm=",
76 description, pid, uid, loginuid, sessionid,
77 MAJOR(dev), MINOR(dev));
78 get_task_comm(name, current);
79 audit_log_untrustedstring(ab, name);
80 audit_log_format(ab, " data=");
81 audit_log_n_hex(ab, data, size);
82 audit_log_end(ab);
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 * the current task. @buf->mutex must be locked.
90 */
91static void tty_audit_buf_push(struct tty_audit_buf *buf)
92{
93 if (buf->valid == 0)
94 return;
95 if (audit_enabled == AUDIT_OFF) {
96 buf->valid = 0;
97 return;
98 }
99 tty_audit_log("tty", buf->dev, buf->data, buf->valid);
100 buf->valid = 0;
101}
102
103/**
104 * tty_audit_exit - Handle a task exit
105 *
106 * Make sure all buffered data is written out and deallocate the buffer.
107 * Only needs to be called if current->signal->tty_audit_buf != %NULL.
108 *
109 * The process is single-threaded at this point; no other threads share
110 * current->signal.
111 */
112void tty_audit_exit(void)
113{
114 struct tty_audit_buf *buf;
115
116 buf = xchg(¤t->signal->tty_audit_buf, ERR_PTR(-ESRCH));
117 if (!buf)
118 return;
119
120 tty_audit_buf_push(buf);
121 tty_audit_buf_free(buf);
122}
123
124/*
125 * tty_audit_fork - Copy TTY audit state for a new task
126 *
127 * Set up TTY audit state in @sig from current. @sig needs no locking.
128 */
129void tty_audit_fork(struct signal_struct *sig)
130{
131 sig->audit_tty = current->signal->audit_tty;
132}
133
134/*
135 * tty_audit_tiocsti - Log TIOCSTI
136 */
137void tty_audit_tiocsti(const struct tty_struct *tty, u8 ch)
138{
139 dev_t dev;
140
141 dev = MKDEV(tty->driver->major, tty->driver->minor_start) + tty->index;
142 if (tty_audit_push())
143 return;
144
145 if (audit_enabled)
146 tty_audit_log("ioctl=TIOCSTI", dev, &ch, 1);
147}
148
149/*
150 * tty_audit_push - Flush current's pending audit data
151 *
152 * Returns 0 if success, -EPERM if tty audit is disabled
153 */
154int tty_audit_push(void)
155{
156 struct tty_audit_buf *buf;
157
158 if (~current->signal->audit_tty & AUDIT_TTY_ENABLE)
159 return -EPERM;
160
161 buf = tty_audit_buf_ref();
162 if (!IS_ERR_OR_NULL(buf)) {
163 mutex_lock(&buf->mutex);
164 tty_audit_buf_push(buf);
165 mutex_unlock(&buf->mutex);
166 }
167 return 0;
168}
169
170/*
171 * tty_audit_buf_get - Get an audit buffer.
172 *
173 * Get an audit buffer, allocate it if necessary. Return %NULL
174 * if out of memory or ERR_PTR(-ESRCH) if tty_audit_exit() has already
175 * occurred. Otherwise, return a new reference to the buffer.
176 */
177static struct tty_audit_buf *tty_audit_buf_get(void)
178{
179 struct tty_audit_buf *buf;
180
181 buf = tty_audit_buf_ref();
182 if (buf)
183 return buf;
184
185 buf = tty_audit_buf_alloc();
186 if (buf == NULL) {
187 audit_log_lost("out of memory in TTY auditing");
188 return NULL;
189 }
190
191 /* Race to use this buffer, free it if another wins */
192 if (cmpxchg(¤t->signal->tty_audit_buf, NULL, buf) != NULL)
193 tty_audit_buf_free(buf);
194 return tty_audit_buf_ref();
195}
196
197/*
198 * tty_audit_add_data - Add data for TTY auditing.
199 *
200 * Audit @data of @size from @tty, if necessary.
201 */
202void tty_audit_add_data(const struct tty_struct *tty, const void *data,
203 size_t size)
204{
205 struct tty_audit_buf *buf;
206 unsigned int audit_tty;
207 bool icanon = L_ICANON(tty);
208 dev_t dev;
209
210 audit_tty = READ_ONCE(current->signal->audit_tty);
211 if (~audit_tty & AUDIT_TTY_ENABLE)
212 return;
213
214 if (unlikely(size == 0))
215 return;
216
217 if (tty->driver->type == TTY_DRIVER_TYPE_PTY
218 && tty->driver->subtype == PTY_TYPE_MASTER)
219 return;
220
221 if ((~audit_tty & AUDIT_TTY_LOG_PASSWD) && icanon && !L_ECHO(tty))
222 return;
223
224 buf = tty_audit_buf_get();
225 if (IS_ERR_OR_NULL(buf))
226 return;
227
228 mutex_lock(&buf->mutex);
229 dev = MKDEV(tty->driver->major, tty->driver->minor_start) + tty->index;
230 if (buf->dev != dev || buf->icanon != icanon) {
231 tty_audit_buf_push(buf);
232 buf->dev = dev;
233 buf->icanon = icanon;
234 }
235 do {
236 size_t run;
237
238 run = N_TTY_BUF_SIZE - buf->valid;
239 if (run > size)
240 run = size;
241 memcpy(buf->data + buf->valid, data, run);
242 buf->valid += run;
243 data += run;
244 size -= run;
245 if (buf->valid == N_TTY_BUF_SIZE)
246 tty_audit_buf_push(buf);
247 } while (size != 0);
248 mutex_unlock(&buf->mutex);
249}
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}