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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
14struct tty_audit_buf {
15 struct mutex mutex; /* Protects all data below */
16 dev_t dev; /* The TTY which the data is from */
17 unsigned icanon:1;
18 size_t valid;
19 unsigned char *data; /* Allocated size N_TTY_BUF_SIZE */
20};
21
22static struct tty_audit_buf *tty_audit_buf_ref(void)
23{
24 struct tty_audit_buf *buf;
25
26 buf = current->signal->tty_audit_buf;
27 WARN_ON(buf == ERR_PTR(-ESRCH));
28 return buf;
29}
30
31static struct tty_audit_buf *tty_audit_buf_alloc(void)
32{
33 struct tty_audit_buf *buf;
34
35 buf = kmalloc(sizeof(*buf), GFP_KERNEL);
36 if (!buf)
37 goto err;
38 buf->data = kmalloc(N_TTY_BUF_SIZE, GFP_KERNEL);
39 if (!buf->data)
40 goto err_buf;
41 mutex_init(&buf->mutex);
42 buf->dev = MKDEV(0, 0);
43 buf->icanon = 0;
44 buf->valid = 0;
45 return buf;
46
47err_buf:
48 kfree(buf);
49err:
50 return NULL;
51}
52
53static void tty_audit_buf_free(struct tty_audit_buf *buf)
54{
55 WARN_ON(buf->valid != 0);
56 kfree(buf->data);
57 kfree(buf);
58}
59
60static void tty_audit_log(const char *description, dev_t dev,
61 unsigned char *data, size_t size)
62{
63 struct audit_buffer *ab;
64 pid_t pid = task_pid_nr(current);
65 uid_t uid = from_kuid(&init_user_ns, task_uid(current));
66 uid_t loginuid = from_kuid(&init_user_ns, audit_get_loginuid(current));
67 unsigned int sessionid = audit_get_sessionid(current);
68
69 ab = audit_log_start(audit_context(), GFP_KERNEL, AUDIT_TTY);
70 if (ab) {
71 char name[sizeof(current->comm)];
72
73 audit_log_format(ab, "%s pid=%u uid=%u auid=%u ses=%u major=%d"
74 " minor=%d comm=", description, pid, uid,
75 loginuid, sessionid, MAJOR(dev), MINOR(dev));
76 get_task_comm(name, current);
77 audit_log_untrustedstring(ab, name);
78 audit_log_format(ab, " data=");
79 audit_log_n_hex(ab, data, size);
80 audit_log_end(ab);
81 }
82}
83
84/**
85 * tty_audit_buf_push - Push buffered data out
86 *
87 * Generate an audit message from the contents of @buf, which is owned by
88 * the current task. @buf->mutex must be locked.
89 */
90static void tty_audit_buf_push(struct tty_audit_buf *buf)
91{
92 if (buf->valid == 0)
93 return;
94 if (audit_enabled == AUDIT_OFF) {
95 buf->valid = 0;
96 return;
97 }
98 tty_audit_log("tty", buf->dev, buf->data, buf->valid);
99 buf->valid = 0;
100}
101
102/**
103 * tty_audit_exit - Handle a task exit
104 *
105 * Make sure all buffered data is written out and deallocate the buffer.
106 * Only needs to be called if current->signal->tty_audit_buf != %NULL.
107 *
108 * The process is single-threaded at this point; no other threads share
109 * current->signal.
110 */
111void tty_audit_exit(void)
112{
113 struct tty_audit_buf *buf;
114
115 buf = xchg(¤t->signal->tty_audit_buf, ERR_PTR(-ESRCH));
116 if (!buf)
117 return;
118
119 tty_audit_buf_push(buf);
120 tty_audit_buf_free(buf);
121}
122
123/**
124 * tty_audit_fork - Copy TTY audit state for a new task
125 *
126 * Set up TTY audit state in @sig from current. @sig needs no locking.
127 */
128void tty_audit_fork(struct signal_struct *sig)
129{
130 sig->audit_tty = current->signal->audit_tty;
131}
132
133/**
134 * tty_audit_tiocsti - Log TIOCSTI
135 */
136void tty_audit_tiocsti(struct tty_struct *tty, char ch)
137{
138 dev_t dev;
139
140 dev = MKDEV(tty->driver->major, tty->driver->minor_start) + tty->index;
141 if (tty_audit_push())
142 return;
143
144 if (audit_enabled)
145 tty_audit_log("ioctl=TIOCSTI", dev, &ch, 1);
146}
147
148/**
149 * tty_audit_push - Flush current's pending audit data
150 *
151 * Returns 0 if success, -EPERM if tty audit is disabled
152 */
153int tty_audit_push(void)
154{
155 struct tty_audit_buf *buf;
156
157 if (~current->signal->audit_tty & AUDIT_TTY_ENABLE)
158 return -EPERM;
159
160 buf = tty_audit_buf_ref();
161 if (!IS_ERR_OR_NULL(buf)) {
162 mutex_lock(&buf->mutex);
163 tty_audit_buf_push(buf);
164 mutex_unlock(&buf->mutex);
165 }
166 return 0;
167}
168
169/**
170 * tty_audit_buf_get - Get an audit buffer.
171 *
172 * Get an audit buffer, allocate it if necessary. Return %NULL
173 * if out of memory or ERR_PTR(-ESRCH) if tty_audit_exit() has already
174 * occurred. Otherwise, return a new reference to the buffer.
175 */
176static struct tty_audit_buf *tty_audit_buf_get(void)
177{
178 struct tty_audit_buf *buf;
179
180 buf = tty_audit_buf_ref();
181 if (buf)
182 return buf;
183
184 buf = tty_audit_buf_alloc();
185 if (buf == NULL) {
186 audit_log_lost("out of memory in TTY auditing");
187 return NULL;
188 }
189
190 /* Race to use this buffer, free it if another wins */
191 if (cmpxchg(¤t->signal->tty_audit_buf, NULL, buf) != NULL)
192 tty_audit_buf_free(buf);
193 return tty_audit_buf_ref();
194}
195
196/**
197 * tty_audit_add_data - Add data for TTY auditing.
198 *
199 * Audit @data of @size from @tty, if necessary.
200 */
201void tty_audit_add_data(struct tty_struct *tty, const void *data, size_t size)
202{
203 struct tty_audit_buf *buf;
204 unsigned int icanon = !!L_ICANON(tty);
205 unsigned int audit_tty;
206 dev_t dev;
207
208 audit_tty = READ_ONCE(current->signal->audit_tty);
209 if (~audit_tty & AUDIT_TTY_ENABLE)
210 return;
211
212 if (unlikely(size == 0))
213 return;
214
215 if (tty->driver->type == TTY_DRIVER_TYPE_PTY
216 && tty->driver->subtype == PTY_TYPE_MASTER)
217 return;
218
219 if ((~audit_tty & AUDIT_TTY_LOG_PASSWD) && icanon && !L_ECHO(tty))
220 return;
221
222 buf = tty_audit_buf_get();
223 if (IS_ERR_OR_NULL(buf))
224 return;
225
226 mutex_lock(&buf->mutex);
227 dev = MKDEV(tty->driver->major, tty->driver->minor_start) + tty->index;
228 if (buf->dev != dev || buf->icanon != icanon) {
229 tty_audit_buf_push(buf);
230 buf->dev = dev;
231 buf->icanon = icanon;
232 }
233 do {
234 size_t run;
235
236 run = N_TTY_BUF_SIZE - buf->valid;
237 if (run > size)
238 run = size;
239 memcpy(buf->data + buf->valid, data, run);
240 buf->valid += run;
241 data += run;
242 size -= run;
243 if (buf->valid == N_TTY_BUF_SIZE)
244 tty_audit_buf_push(buf);
245 } while (size != 0);
246 mutex_unlock(&buf->mutex);
247}
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 int 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, struct task_struct *tsk,
64 uid_t loginuid, unsigned sessionid, int major,
65 int minor, unsigned char *data, size_t size)
66{
67 struct audit_buffer *ab;
68
69 ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_TTY);
70 if (ab) {
71 char name[sizeof(tsk->comm)];
72 uid_t uid = task_uid(tsk);
73
74 audit_log_format(ab, "%s pid=%u uid=%u auid=%u ses=%u "
75 "major=%d minor=%d comm=", description,
76 tsk->pid, uid, loginuid, sessionid,
77 major, minor);
78 get_task_comm(name, tsk);
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/**
87 * tty_audit_buf_push - Push buffered data out
88 *
89 * Generate an audit message from the contents of @buf, which is owned by
90 * @tsk with @loginuid. @buf->mutex must be locked.
91 */
92static void tty_audit_buf_push(struct task_struct *tsk, uid_t loginuid,
93 unsigned int sessionid,
94 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", tsk, loginuid, sessionid, buf->major, buf->minor,
103 buf->data, buf->valid);
104 buf->valid = 0;
105}
106
107/**
108 * tty_audit_buf_push_current - Push buffered data out
109 *
110 * Generate an audit message from the contents of @buf, which is owned by
111 * the current task. @buf->mutex must be locked.
112 */
113static void tty_audit_buf_push_current(struct tty_audit_buf *buf)
114{
115 uid_t auid = audit_get_loginuid(current);
116 unsigned int sessionid = audit_get_sessionid(current);
117 tty_audit_buf_push(current, auid, sessionid, buf);
118}
119
120/**
121 * tty_audit_exit - Handle a task exit
122 *
123 * Make sure all buffered data is written out and deallocate the buffer.
124 * Only needs to be called if current->signal->tty_audit_buf != %NULL.
125 */
126void tty_audit_exit(void)
127{
128 struct tty_audit_buf *buf;
129
130 spin_lock_irq(¤t->sighand->siglock);
131 buf = current->signal->tty_audit_buf;
132 current->signal->tty_audit_buf = NULL;
133 spin_unlock_irq(¤t->sighand->siglock);
134 if (!buf)
135 return;
136
137 mutex_lock(&buf->mutex);
138 tty_audit_buf_push_current(buf);
139 mutex_unlock(&buf->mutex);
140
141 tty_audit_buf_put(buf);
142}
143
144/**
145 * tty_audit_fork - Copy TTY audit state for a new task
146 *
147 * Set up TTY audit state in @sig from current. @sig needs no locking.
148 */
149void tty_audit_fork(struct signal_struct *sig)
150{
151 spin_lock_irq(¤t->sighand->siglock);
152 sig->audit_tty = current->signal->audit_tty;
153 spin_unlock_irq(¤t->sighand->siglock);
154}
155
156/**
157 * tty_audit_tiocsti - Log TIOCSTI
158 */
159void tty_audit_tiocsti(struct tty_struct *tty, char ch)
160{
161 struct tty_audit_buf *buf;
162 int major, minor, should_audit;
163
164 spin_lock_irq(¤t->sighand->siglock);
165 should_audit = current->signal->audit_tty;
166 buf = current->signal->tty_audit_buf;
167 if (buf)
168 atomic_inc(&buf->count);
169 spin_unlock_irq(¤t->sighand->siglock);
170
171 major = tty->driver->major;
172 minor = tty->driver->minor_start + tty->index;
173 if (buf) {
174 mutex_lock(&buf->mutex);
175 if (buf->major == major && buf->minor == minor)
176 tty_audit_buf_push_current(buf);
177 mutex_unlock(&buf->mutex);
178 tty_audit_buf_put(buf);
179 }
180
181 if (should_audit && audit_enabled) {
182 uid_t auid;
183 unsigned int sessionid;
184
185 auid = audit_get_loginuid(current);
186 sessionid = audit_get_sessionid(current);
187 tty_audit_log("ioctl=TIOCSTI", current, auid, sessionid, major,
188 minor, &ch, 1);
189 }
190}
191
192/**
193 * tty_audit_push_task - Flush task's pending audit data
194 * @tsk: task pointer
195 * @loginuid: sender login uid
196 * @sessionid: sender session id
197 *
198 * Called with a ref on @tsk held. Try to lock sighand and get a
199 * reference to the tty audit buffer if available.
200 * Flush the buffer or return an appropriate error code.
201 */
202int tty_audit_push_task(struct task_struct *tsk, uid_t loginuid, u32 sessionid)
203{
204 struct tty_audit_buf *buf = ERR_PTR(-EPERM);
205 unsigned long flags;
206
207 if (!lock_task_sighand(tsk, &flags))
208 return -ESRCH;
209
210 if (tsk->signal->audit_tty) {
211 buf = tsk->signal->tty_audit_buf;
212 if (buf)
213 atomic_inc(&buf->count);
214 }
215 unlock_task_sighand(tsk, &flags);
216
217 /*
218 * Return 0 when signal->audit_tty set
219 * but tsk->signal->tty_audit_buf == NULL.
220 */
221 if (!buf || IS_ERR(buf))
222 return PTR_ERR(buf);
223
224 mutex_lock(&buf->mutex);
225 tty_audit_buf_push(tsk, loginuid, sessionid, buf);
226 mutex_unlock(&buf->mutex);
227
228 tty_audit_buf_put(buf);
229 return 0;
230}
231
232/**
233 * tty_audit_buf_get - Get an audit buffer.
234 *
235 * Get an audit buffer for @tty, allocate it if necessary. Return %NULL
236 * if TTY auditing is disabled or out of memory. Otherwise, return a new
237 * reference to the buffer.
238 */
239static struct tty_audit_buf *tty_audit_buf_get(struct tty_struct *tty)
240{
241 struct tty_audit_buf *buf, *buf2;
242
243 buf = NULL;
244 buf2 = NULL;
245 spin_lock_irq(¤t->sighand->siglock);
246 if (likely(!current->signal->audit_tty))
247 goto out;
248 buf = current->signal->tty_audit_buf;
249 if (buf) {
250 atomic_inc(&buf->count);
251 goto out;
252 }
253 spin_unlock_irq(¤t->sighand->siglock);
254
255 buf2 = tty_audit_buf_alloc(tty->driver->major,
256 tty->driver->minor_start + tty->index,
257 tty->icanon);
258 if (buf2 == NULL) {
259 audit_log_lost("out of memory in TTY auditing");
260 return NULL;
261 }
262
263 spin_lock_irq(¤t->sighand->siglock);
264 if (!current->signal->audit_tty)
265 goto out;
266 buf = current->signal->tty_audit_buf;
267 if (!buf) {
268 current->signal->tty_audit_buf = buf2;
269 buf = buf2;
270 buf2 = NULL;
271 }
272 atomic_inc(&buf->count);
273 /* Fall through */
274 out:
275 spin_unlock_irq(¤t->sighand->siglock);
276 if (buf2)
277 tty_audit_buf_free(buf2);
278 return buf;
279}
280
281/**
282 * tty_audit_add_data - Add data for TTY auditing.
283 *
284 * Audit @data of @size from @tty, if necessary.
285 */
286void tty_audit_add_data(struct tty_struct *tty, unsigned char *data,
287 size_t size)
288{
289 struct tty_audit_buf *buf;
290 int major, minor;
291
292 if (unlikely(size == 0))
293 return;
294
295 if (tty->driver->type == TTY_DRIVER_TYPE_PTY
296 && tty->driver->subtype == PTY_TYPE_MASTER)
297 return;
298
299 buf = tty_audit_buf_get(tty);
300 if (!buf)
301 return;
302
303 mutex_lock(&buf->mutex);
304 major = tty->driver->major;
305 minor = tty->driver->minor_start + tty->index;
306 if (buf->major != major || buf->minor != minor
307 || buf->icanon != tty->icanon) {
308 tty_audit_buf_push_current(buf);
309 buf->major = major;
310 buf->minor = minor;
311 buf->icanon = tty->icanon;
312 }
313 do {
314 size_t run;
315
316 run = N_TTY_BUF_SIZE - buf->valid;
317 if (run > size)
318 run = size;
319 memcpy(buf->data + buf->valid, data, run);
320 buf->valid += run;
321 data += run;
322 size -= run;
323 if (buf->valid == N_TTY_BUF_SIZE)
324 tty_audit_buf_push_current(buf);
325 } while (size != 0);
326 mutex_unlock(&buf->mutex);
327 tty_audit_buf_put(buf);
328}
329
330/**
331 * tty_audit_push - Push buffered data out
332 *
333 * Make sure no audit data is pending for @tty on the current process.
334 */
335void tty_audit_push(struct tty_struct *tty)
336{
337 struct tty_audit_buf *buf;
338
339 spin_lock_irq(¤t->sighand->siglock);
340 if (likely(!current->signal->audit_tty)) {
341 spin_unlock_irq(¤t->sighand->siglock);
342 return;
343 }
344 buf = current->signal->tty_audit_buf;
345 if (buf)
346 atomic_inc(&buf->count);
347 spin_unlock_irq(¤t->sighand->siglock);
348
349 if (buf) {
350 int major, minor;
351
352 major = tty->driver->major;
353 minor = tty->driver->minor_start + tty->index;
354 mutex_lock(&buf->mutex);
355 if (buf->major == major && buf->minor == minor)
356 tty_audit_buf_push_current(buf);
357 mutex_unlock(&buf->mutex);
358 tty_audit_buf_put(buf);
359 }
360}