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
14 struct 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
tty_audit_buf_ref(void)22 static 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
tty_audit_buf_alloc(void)31 static 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
47 err_buf:
48 kfree(buf);
49 err:
50 return NULL;
51 }
52
tty_audit_buf_free(struct tty_audit_buf * buf)53 static 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
tty_audit_log(const char * description,dev_t dev,unsigned char * data,size_t size)60 static 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 */
tty_audit_buf_push(struct tty_audit_buf * buf)90 static 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 */
tty_audit_exit(void)111 void 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 */
tty_audit_fork(struct signal_struct * sig)128 void 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 */
tty_audit_tiocsti(struct tty_struct * tty,char ch)136 void 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 */
tty_audit_push(void)153 int 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 */
tty_audit_buf_get(void)176 static 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 */
tty_audit_add_data(struct tty_struct * tty,const void * data,size_t size)201 void 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 }
248