blob: 7722466e052faedeb2ec999ba0b2f67f8b300e3e [file] [log] [blame]
Miloslav Trmac522ed772007-07-15 23:40:56 -07001/*
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/file.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
Alan Cox66c6cea2008-02-08 04:18:46 -080030 buf = kmalloc(sizeof(*buf), GFP_KERNEL);
Miloslav Trmac522ed772007-07-15 23:40:56 -070031 if (!buf)
32 goto err;
33 if (PAGE_SIZE != N_TTY_BUF_SIZE)
34 buf->data = kmalloc(N_TTY_BUF_SIZE, GFP_KERNEL);
35 else
36 buf->data = (unsigned char *)__get_free_page(GFP_KERNEL);
37 if (!buf->data)
38 goto err_buf;
39 atomic_set(&buf->count, 1);
40 mutex_init(&buf->mutex);
41 buf->major = major;
42 buf->minor = minor;
43 buf->icanon = icanon;
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 if (PAGE_SIZE != N_TTY_BUF_SIZE)
57 kfree(buf->data);
58 else
59 free_page((unsigned long)buf->data);
60 kfree(buf);
61}
62
63static void tty_audit_buf_put(struct tty_audit_buf *buf)
64{
65 if (atomic_dec_and_test(&buf->count))
66 tty_audit_buf_free(buf);
67}
68
69/**
70 * tty_audit_buf_push - Push buffered data out
71 *
72 * Generate an audit message from the contents of @buf, which is owned by
73 * @tsk with @loginuid. @buf->mutex must be locked.
74 */
75static void tty_audit_buf_push(struct task_struct *tsk, uid_t loginuid,
Eric Paris4746ec52008-01-08 10:06:53 -050076 unsigned int sessionid,
Miloslav Trmac522ed772007-07-15 23:40:56 -070077 struct tty_audit_buf *buf)
78{
79 struct audit_buffer *ab;
80
81 if (buf->valid == 0)
82 return;
83 if (audit_enabled == 0)
84 return;
85 ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_TTY);
86 if (ab) {
87 char name[sizeof(tsk->comm)];
88
Eric Paris4746ec52008-01-08 10:06:53 -050089 audit_log_format(ab, "tty pid=%u uid=%u auid=%u ses=%u "
90 "major=%d minor=%d comm=", tsk->pid, tsk->uid,
91 loginuid, sessionid, buf->major, buf->minor);
Miloslav Trmac522ed772007-07-15 23:40:56 -070092 get_task_comm(name, tsk);
93 audit_log_untrustedstring(ab, name);
94 audit_log_format(ab, " data=");
95 audit_log_n_untrustedstring(ab, buf->valid, buf->data);
96 audit_log_end(ab);
97 }
98 buf->valid = 0;
99}
100
101/**
102 * tty_audit_buf_push_current - Push buffered data out
103 *
104 * Generate an audit message from the contents of @buf, which is owned by
105 * the current task. @buf->mutex must be locked.
106 */
107static void tty_audit_buf_push_current(struct tty_audit_buf *buf)
108{
Eric Paris4746ec52008-01-08 10:06:53 -0500109 uid_t auid = audit_get_loginuid(current);
110 unsigned int sessionid = audit_get_sessionid(current);
111 tty_audit_buf_push(current, auid, sessionid, buf);
Miloslav Trmac522ed772007-07-15 23:40:56 -0700112}
113
114/**
115 * tty_audit_exit - Handle a task exit
116 *
117 * Make sure all buffered data is written out and deallocate the buffer.
118 * Only needs to be called if current->signal->tty_audit_buf != %NULL.
119 */
120void tty_audit_exit(void)
121{
122 struct tty_audit_buf *buf;
123
124 spin_lock_irq(&current->sighand->siglock);
125 buf = current->signal->tty_audit_buf;
126 current->signal->tty_audit_buf = NULL;
127 spin_unlock_irq(&current->sighand->siglock);
128 if (!buf)
129 return;
130
131 mutex_lock(&buf->mutex);
132 tty_audit_buf_push_current(buf);
133 mutex_unlock(&buf->mutex);
134
135 tty_audit_buf_put(buf);
136}
137
138/**
139 * tty_audit_fork - Copy TTY audit state for a new task
140 *
141 * Set up TTY audit state in @sig from current. @sig needs no locking.
142 */
143void tty_audit_fork(struct signal_struct *sig)
144{
145 spin_lock_irq(&current->sighand->siglock);
146 sig->audit_tty = current->signal->audit_tty;
147 spin_unlock_irq(&current->sighand->siglock);
148 sig->tty_audit_buf = NULL;
149}
150
151/**
152 * tty_audit_push_task - Flush task's pending audit data
153 */
154void tty_audit_push_task(struct task_struct *tsk, uid_t loginuid)
155{
156 struct tty_audit_buf *buf;
Eric Paris4746ec52008-01-08 10:06:53 -0500157 /* FIXME I think this is correct. Check against netlink once that is
158 * I really need to read this code more closely. But that's for
159 * another patch.
160 */
161 unsigned int sessionid = audit_get_sessionid(tsk);
Miloslav Trmac522ed772007-07-15 23:40:56 -0700162
163 spin_lock_irq(&tsk->sighand->siglock);
164 buf = tsk->signal->tty_audit_buf;
165 if (buf)
166 atomic_inc(&buf->count);
167 spin_unlock_irq(&tsk->sighand->siglock);
168 if (!buf)
169 return;
170
171 mutex_lock(&buf->mutex);
Eric Paris4746ec52008-01-08 10:06:53 -0500172 tty_audit_buf_push(tsk, loginuid, sessionid, buf);
Miloslav Trmac522ed772007-07-15 23:40:56 -0700173 mutex_unlock(&buf->mutex);
174
175 tty_audit_buf_put(buf);
176}
177
178/**
179 * tty_audit_buf_get - Get an audit buffer.
180 *
181 * Get an audit buffer for @tty, allocate it if necessary. Return %NULL
182 * if TTY auditing is disabled or out of memory. Otherwise, return a new
183 * reference to the buffer.
184 */
185static struct tty_audit_buf *tty_audit_buf_get(struct tty_struct *tty)
186{
187 struct tty_audit_buf *buf, *buf2;
188
189 buf = NULL;
190 buf2 = NULL;
191 spin_lock_irq(&current->sighand->siglock);
192 if (likely(!current->signal->audit_tty))
193 goto out;
194 buf = current->signal->tty_audit_buf;
195 if (buf) {
196 atomic_inc(&buf->count);
197 goto out;
198 }
199 spin_unlock_irq(&current->sighand->siglock);
200
201 buf2 = tty_audit_buf_alloc(tty->driver->major,
202 tty->driver->minor_start + tty->index,
203 tty->icanon);
204 if (buf2 == NULL) {
205 audit_log_lost("out of memory in TTY auditing");
206 return NULL;
207 }
208
209 spin_lock_irq(&current->sighand->siglock);
210 if (!current->signal->audit_tty)
211 goto out;
212 buf = current->signal->tty_audit_buf;
213 if (!buf) {
214 current->signal->tty_audit_buf = buf2;
215 buf = buf2;
216 buf2 = NULL;
217 }
218 atomic_inc(&buf->count);
219 /* Fall through */
220 out:
221 spin_unlock_irq(&current->sighand->siglock);
222 if (buf2)
223 tty_audit_buf_free(buf2);
224 return buf;
225}
226
227/**
228 * tty_audit_add_data - Add data for TTY auditing.
229 *
230 * Audit @data of @size from @tty, if necessary.
231 */
232void tty_audit_add_data(struct tty_struct *tty, unsigned char *data,
233 size_t size)
234{
235 struct tty_audit_buf *buf;
236 int major, minor;
237
238 if (unlikely(size == 0))
239 return;
240
241 buf = tty_audit_buf_get(tty);
242 if (!buf)
243 return;
244
245 mutex_lock(&buf->mutex);
246 major = tty->driver->major;
247 minor = tty->driver->minor_start + tty->index;
248 if (buf->major != major || buf->minor != minor
249 || buf->icanon != tty->icanon) {
250 tty_audit_buf_push_current(buf);
251 buf->major = major;
252 buf->minor = minor;
253 buf->icanon = tty->icanon;
254 }
255 do {
256 size_t run;
257
258 run = N_TTY_BUF_SIZE - buf->valid;
259 if (run > size)
260 run = size;
261 memcpy(buf->data + buf->valid, data, run);
262 buf->valid += run;
263 data += run;
264 size -= run;
265 if (buf->valid == N_TTY_BUF_SIZE)
266 tty_audit_buf_push_current(buf);
267 } while (size != 0);
268 mutex_unlock(&buf->mutex);
269 tty_audit_buf_put(buf);
270}
271
272/**
273 * tty_audit_push - Push buffered data out
274 *
275 * Make sure no audit data is pending for @tty on the current process.
276 */
277void tty_audit_push(struct tty_struct *tty)
278{
279 struct tty_audit_buf *buf;
280
281 spin_lock_irq(&current->sighand->siglock);
282 if (likely(!current->signal->audit_tty)) {
283 spin_unlock_irq(&current->sighand->siglock);
284 return;
285 }
286 buf = current->signal->tty_audit_buf;
287 if (buf)
288 atomic_inc(&buf->count);
289 spin_unlock_irq(&current->sighand->siglock);
290
291 if (buf) {
292 int major, minor;
293
294 major = tty->driver->major;
295 minor = tty->driver->minor_start + tty->index;
296 mutex_lock(&buf->mutex);
297 if (buf->major == major && buf->minor == minor)
298 tty_audit_buf_push_current(buf);
299 mutex_unlock(&buf->mutex);
300 tty_audit_buf_put(buf);
301 }
302}
303
304/**
305 * tty_audit_opening - A TTY is being opened.
306 *
307 * As a special hack, tasks that close all their TTYs and open new ones
308 * are assumed to be system daemons (e.g. getty) and auditing is
309 * automatically disabled for them.
310 */
311void tty_audit_opening(void)
312{
313 int disable;
314
315 disable = 1;
316 spin_lock_irq(&current->sighand->siglock);
317 if (current->signal->audit_tty == 0)
318 disable = 0;
319 spin_unlock_irq(&current->sighand->siglock);
320 if (!disable)
321 return;
322
323 task_lock(current);
324 if (current->files) {
325 struct fdtable *fdt;
326 unsigned i;
327
328 /*
329 * We don't take a ref to the file, so we must hold ->file_lock
330 * instead.
331 */
332 spin_lock(&current->files->file_lock);
333 fdt = files_fdtable(current->files);
334 for (i = 0; i < fdt->max_fds; i++) {
335 struct file *filp;
336
337 filp = fcheck_files(current->files, i);
338 if (filp && is_tty(filp)) {
339 disable = 0;
340 break;
341 }
342 }
343 spin_unlock(&current->files->file_lock);
344 }
345 task_unlock(current);
346 if (!disable)
347 return;
348
349 spin_lock_irq(&current->sighand->siglock);
350 current->signal->audit_tty = 0;
351 spin_unlock_irq(&current->sighand->siglock);
352}