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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 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}