GNU Linux-libre 5.13.14-gnu1
[releases.git] / drivers / tty / tty_audit.c
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
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
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
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
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  */
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  */
112 void tty_audit_exit(void)
113 {
114         struct tty_audit_buf *buf;
115
116         buf = xchg(&current->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  */
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  */
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  */
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  */
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(&current->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  */
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 }