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
15 struct tty_audit_buf {
16 struct mutex mutex; /* Protects all data below */
17 dev_t dev; /* The TTY which the data is from */
18 unsigned icanon:1;
19 size_t valid;
20 unsigned char *data; /* Allocated size N_TTY_BUF_SIZE */
21 };
22
tty_audit_buf_ref(void)23 static 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
tty_audit_buf_alloc(void)32 static struct tty_audit_buf *tty_audit_buf_alloc(void)
33 {
34 struct tty_audit_buf *buf;
35
36 buf = kmalloc(sizeof(*buf), GFP_KERNEL);
37 if (!buf)
38 goto err;
39 buf->data = kmalloc(N_TTY_BUF_SIZE, GFP_KERNEL);
40 if (!buf->data)
41 goto err_buf;
42 mutex_init(&buf->mutex);
43 buf->dev = MKDEV(0, 0);
44 buf->icanon = 0;
45 buf->valid = 0;
46 return buf;
47
48 err_buf:
49 kfree(buf);
50 err:
51 return NULL;
52 }
53
tty_audit_buf_free(struct tty_audit_buf * buf)54 static 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
tty_audit_log(const char * description,dev_t dev,unsigned char * data,size_t size)61 static void tty_audit_log(const char *description, dev_t dev,
62 unsigned char *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
70 ab = audit_log_start(audit_context(), GFP_KERNEL, AUDIT_TTY);
71 if (ab) {
72 char name[sizeof(current->comm)];
73
74 audit_log_format(ab, "%s pid=%u uid=%u auid=%u ses=%u major=%d"
75 " minor=%d comm=", description, pid, uid,
76 loginuid, sessionid, MAJOR(dev), MINOR(dev));
77 get_task_comm(name, current);
78 audit_log_untrustedstring(ab, name);
79 audit_log_format(ab, " data=");
80 audit_log_n_hex(ab, data, size);
81 audit_log_end(ab);
82 }
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 */
tty_audit_buf_push(struct tty_audit_buf * buf)91 static 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 */
tty_audit_exit(void)112 void 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 */
tty_audit_fork(struct signal_struct * sig)129 void 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 */
tty_audit_tiocsti(struct tty_struct * tty,char ch)137 void tty_audit_tiocsti(struct tty_struct *tty, char 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 */
tty_audit_push(void)154 int 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 */
tty_audit_buf_get(void)177 static 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 */
tty_audit_add_data(struct tty_struct * tty,const void * data,size_t size)202 void tty_audit_add_data(struct tty_struct *tty, const void *data, size_t size)
203 {
204 struct tty_audit_buf *buf;
205 unsigned int icanon = !!L_ICANON(tty);
206 unsigned int audit_tty;
207 dev_t dev;
208
209 audit_tty = READ_ONCE(current->signal->audit_tty);
210 if (~audit_tty & AUDIT_TTY_ENABLE)
211 return;
212
213 if (unlikely(size == 0))
214 return;
215
216 if (tty->driver->type == TTY_DRIVER_TYPE_PTY
217 && tty->driver->subtype == PTY_TYPE_MASTER)
218 return;
219
220 if ((~audit_tty & AUDIT_TTY_LOG_PASSWD) && icanon && !L_ECHO(tty))
221 return;
222
223 buf = tty_audit_buf_get();
224 if (IS_ERR_OR_NULL(buf))
225 return;
226
227 mutex_lock(&buf->mutex);
228 dev = MKDEV(tty->driver->major, tty->driver->minor_start) + tty->index;
229 if (buf->dev != dev || buf->icanon != icanon) {
230 tty_audit_buf_push(buf);
231 buf->dev = dev;
232 buf->icanon = icanon;
233 }
234 do {
235 size_t run;
236
237 run = N_TTY_BUF_SIZE - buf->valid;
238 if (run > size)
239 run = size;
240 memcpy(buf->data + buf->valid, data, run);
241 buf->valid += run;
242 data += run;
243 size -= run;
244 if (buf->valid == N_TTY_BUF_SIZE)
245 tty_audit_buf_push(buf);
246 } while (size != 0);
247 mutex_unlock(&buf->mutex);
248 }
249