audit: Handle embedded NUL in TTY input auditing
[linux-2.6.git] / drivers / char / tty_audit.c
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/file.h>
14 #include <linux/fdtable.h>
15 #include <linux/tty.h>
16
17 struct tty_audit_buf {
18         atomic_t count;
19         struct mutex mutex;     /* Protects all data below */
20         int major, minor;       /* The TTY which the data is from */
21         unsigned icanon:1;
22         size_t valid;
23         unsigned char *data;    /* Allocated size N_TTY_BUF_SIZE */
24 };
25
26 static struct tty_audit_buf *tty_audit_buf_alloc(int major, int minor,
27                                                  int icanon)
28 {
29         struct tty_audit_buf *buf;
30
31         buf = kmalloc(sizeof(*buf), GFP_KERNEL);
32         if (!buf)
33                 goto err;
34         if (PAGE_SIZE != N_TTY_BUF_SIZE)
35                 buf->data = kmalloc(N_TTY_BUF_SIZE, GFP_KERNEL);
36         else
37                 buf->data = (unsigned char *)__get_free_page(GFP_KERNEL);
38         if (!buf->data)
39                 goto err_buf;
40         atomic_set(&buf->count, 1);
41         mutex_init(&buf->mutex);
42         buf->major = major;
43         buf->minor = minor;
44         buf->icanon = icanon;
45         buf->valid = 0;
46         return buf;
47
48 err_buf:
49         kfree(buf);
50 err:
51         return NULL;
52 }
53
54 static void tty_audit_buf_free(struct tty_audit_buf *buf)
55 {
56         WARN_ON(buf->valid != 0);
57         if (PAGE_SIZE != N_TTY_BUF_SIZE)
58                 kfree(buf->data);
59         else
60                 free_page((unsigned long)buf->data);
61         kfree(buf);
62 }
63
64 static void tty_audit_buf_put(struct tty_audit_buf *buf)
65 {
66         if (atomic_dec_and_test(&buf->count))
67                 tty_audit_buf_free(buf);
68 }
69
70 /**
71  *      tty_audit_buf_push      -       Push buffered data out
72  *
73  *      Generate an audit message from the contents of @buf, which is owned by
74  *      @tsk with @loginuid.  @buf->mutex must be locked.
75  */
76 static void tty_audit_buf_push(struct task_struct *tsk, uid_t loginuid,
77                                unsigned int sessionid,
78                                struct tty_audit_buf *buf)
79 {
80         struct audit_buffer *ab;
81
82         if (buf->valid == 0)
83                 return;
84         if (audit_enabled == 0)
85                 return;
86         ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_TTY);
87         if (ab) {
88                 char name[sizeof(tsk->comm)];
89
90                 audit_log_format(ab, "tty pid=%u uid=%u auid=%u ses=%u "
91                                  "major=%d minor=%d comm=", tsk->pid, tsk->uid,
92                                  loginuid, sessionid, buf->major, buf->minor);
93                 get_task_comm(name, tsk);
94                 audit_log_untrustedstring(ab, name);
95                 audit_log_format(ab, " data=");
96                 audit_log_n_hex(ab, buf->data, buf->valid);
97                 audit_log_end(ab);
98         }
99         buf->valid = 0;
100 }
101
102 /**
103  *      tty_audit_buf_push_current      -       Push buffered data out
104  *
105  *      Generate an audit message from the contents of @buf, which is owned by
106  *      the current task.  @buf->mutex must be locked.
107  */
108 static void tty_audit_buf_push_current(struct tty_audit_buf *buf)
109 {
110         uid_t auid = audit_get_loginuid(current);
111         unsigned int sessionid = audit_get_sessionid(current);
112         tty_audit_buf_push(current, auid, sessionid, buf);
113 }
114
115 /**
116  *      tty_audit_exit  -       Handle a task exit
117  *
118  *      Make sure all buffered data is written out and deallocate the buffer.
119  *      Only needs to be called if current->signal->tty_audit_buf != %NULL.
120  */
121 void tty_audit_exit(void)
122 {
123         struct tty_audit_buf *buf;
124
125         spin_lock_irq(&current->sighand->siglock);
126         buf = current->signal->tty_audit_buf;
127         current->signal->tty_audit_buf = NULL;
128         spin_unlock_irq(&current->sighand->siglock);
129         if (!buf)
130                 return;
131
132         mutex_lock(&buf->mutex);
133         tty_audit_buf_push_current(buf);
134         mutex_unlock(&buf->mutex);
135
136         tty_audit_buf_put(buf);
137 }
138
139 /**
140  *      tty_audit_fork  -       Copy TTY audit state for a new task
141  *
142  *      Set up TTY audit state in @sig from current.  @sig needs no locking.
143  */
144 void tty_audit_fork(struct signal_struct *sig)
145 {
146         spin_lock_irq(&current->sighand->siglock);
147         sig->audit_tty = current->signal->audit_tty;
148         spin_unlock_irq(&current->sighand->siglock);
149         sig->tty_audit_buf = NULL;
150 }
151
152 /**
153  *      tty_audit_push_task     -       Flush task's pending audit data
154  */
155 void tty_audit_push_task(struct task_struct *tsk, uid_t loginuid, u32 sessionid)
156 {
157         struct tty_audit_buf *buf;
158
159         spin_lock_irq(&tsk->sighand->siglock);
160         buf = tsk->signal->tty_audit_buf;
161         if (buf)
162                 atomic_inc(&buf->count);
163         spin_unlock_irq(&tsk->sighand->siglock);
164         if (!buf)
165                 return;
166
167         mutex_lock(&buf->mutex);
168         tty_audit_buf_push(tsk, loginuid, sessionid, buf);
169         mutex_unlock(&buf->mutex);
170
171         tty_audit_buf_put(buf);
172 }
173
174 /**
175  *      tty_audit_buf_get       -       Get an audit buffer.
176  *
177  *      Get an audit buffer for @tty, allocate it if necessary.  Return %NULL
178  *      if TTY auditing is disabled or out of memory.  Otherwise, return a new
179  *      reference to the buffer.
180  */
181 static struct tty_audit_buf *tty_audit_buf_get(struct tty_struct *tty)
182 {
183         struct tty_audit_buf *buf, *buf2;
184
185         buf = NULL;
186         buf2 = NULL;
187         spin_lock_irq(&current->sighand->siglock);
188         if (likely(!current->signal->audit_tty))
189                 goto out;
190         buf = current->signal->tty_audit_buf;
191         if (buf) {
192                 atomic_inc(&buf->count);
193                 goto out;
194         }
195         spin_unlock_irq(&current->sighand->siglock);
196
197         buf2 = tty_audit_buf_alloc(tty->driver->major,
198                                    tty->driver->minor_start + tty->index,
199                                    tty->icanon);
200         if (buf2 == NULL) {
201                 audit_log_lost("out of memory in TTY auditing");
202                 return NULL;
203         }
204
205         spin_lock_irq(&current->sighand->siglock);
206         if (!current->signal->audit_tty)
207                 goto out;
208         buf = current->signal->tty_audit_buf;
209         if (!buf) {
210                 current->signal->tty_audit_buf = buf2;
211                 buf = buf2;
212                 buf2 = NULL;
213         }
214         atomic_inc(&buf->count);
215         /* Fall through */
216  out:
217         spin_unlock_irq(&current->sighand->siglock);
218         if (buf2)
219                 tty_audit_buf_free(buf2);
220         return buf;
221 }
222
223 /**
224  *      tty_audit_add_data      -       Add data for TTY auditing.
225  *
226  *      Audit @data of @size from @tty, if necessary.
227  */
228 void tty_audit_add_data(struct tty_struct *tty, unsigned char *data,
229                         size_t size)
230 {
231         struct tty_audit_buf *buf;
232         int major, minor;
233
234         if (unlikely(size == 0))
235                 return;
236
237         if (tty->driver->type == TTY_DRIVER_TYPE_PTY
238             && tty->driver->subtype == PTY_TYPE_MASTER)
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  */
277 void 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 }