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522ed776 MT |
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> | |
9f3acc31 | 14 | #include <linux/fdtable.h> |
522ed776 MT |
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 | ||
66c6ceae | 31 | buf = kmalloc(sizeof(*buf), GFP_KERNEL); |
522ed776 MT |
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, | |
4746ec5b | 77 | unsigned int sessionid, |
522ed776 MT |
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 | ||
4746ec5b EP |
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); | |
522ed776 MT |
93 | get_task_comm(name, tsk); |
94 | audit_log_untrustedstring(ab, name); | |
95 | audit_log_format(ab, " data="); | |
b556f8ad | 96 | audit_log_n_untrustedstring(ab, buf->data, buf->valid); |
522ed776 MT |
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 | { | |
4746ec5b EP |
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); | |
522ed776 MT |
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(¤t->sighand->siglock); | |
126 | buf = current->signal->tty_audit_buf; | |
127 | current->signal->tty_audit_buf = NULL; | |
128 | spin_unlock_irq(¤t->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(¤t->sighand->siglock); | |
147 | sig->audit_tty = current->signal->audit_tty; | |
148 | spin_unlock_irq(¤t->sighand->siglock); | |
149 | sig->tty_audit_buf = NULL; | |
150 | } | |
151 | ||
152 | /** | |
153 | * tty_audit_push_task - Flush task's pending audit data | |
154 | */ | |
2532386f | 155 | void tty_audit_push_task(struct task_struct *tsk, uid_t loginuid, u32 sessionid) |
522ed776 MT |
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); | |
4746ec5b | 168 | tty_audit_buf_push(tsk, loginuid, sessionid, buf); |
522ed776 MT |
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(¤t->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(¤t->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(¤t->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(¤t->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 | ||
41126226 MT |
237 | if (tty->driver->type == TTY_DRIVER_TYPE_PTY |
238 | && tty->driver->subtype == PTY_TYPE_MASTER) | |
239 | return; | |
240 | ||
522ed776 MT |
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(¤t->sighand->siglock); | |
282 | if (likely(!current->signal->audit_tty)) { | |
283 | spin_unlock_irq(¤t->sighand->siglock); | |
284 | return; | |
285 | } | |
286 | buf = current->signal->tty_audit_buf; | |
287 | if (buf) | |
288 | atomic_inc(&buf->count); | |
289 | spin_unlock_irq(¤t->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 | } |