aboutsummaryrefslogtreecommitdiff
path: root/drivers/tty/tty_audit.c
blob: ca7afd7b27165d27384b2d799a1f417b77f810a4 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
// SPDX-License-Identifier: GPL-2.0
/*
 * Creating audit events from TTY input.
 *
 * Copyright (C) 2007 Red Hat, Inc.  All rights reserved.
 *
 * Authors: Miloslav Trmac <mitr@redhat.com>
 */

#include <linux/audit.h>
#include <linux/slab.h>
#include <linux/tty.h>
#include "tty.h"

struct tty_audit_buf {
	struct mutex mutex;	/* Protects all data below */
	dev_t dev;		/* The TTY which the data is from */
	unsigned icanon:1;
	size_t valid;
	unsigned char *data;	/* Allocated size N_TTY_BUF_SIZE */
};

static struct tty_audit_buf *tty_audit_buf_ref(void)
{
	struct tty_audit_buf *buf;

	buf = current->signal->tty_audit_buf;
	WARN_ON(buf == ERR_PTR(-ESRCH));
	return buf;
}

static struct tty_audit_buf *tty_audit_buf_alloc(void)
{
	struct tty_audit_buf *buf;

	buf = kmalloc(sizeof(*buf), GFP_KERNEL);
	if (!buf)
		goto err;
	buf->data = kmalloc(N_TTY_BUF_SIZE, GFP_KERNEL);
	if (!buf->data)
		goto err_buf;
	mutex_init(&buf->mutex);
	buf->dev = MKDEV(0, 0);
	buf->icanon = 0;
	buf->valid = 0;
	return buf;

err_buf:
	kfree(buf);
err:
	return NULL;
}

static void tty_audit_buf_free(struct tty_audit_buf *buf)
{
	WARN_ON(buf->valid != 0);
	kfree(buf->data);
	kfree(buf);
}

static void tty_audit_log(const char *description, dev_t dev,
			  unsigned char *data, size_t size)
{
	struct audit_buffer *ab;
	pid_t pid = task_pid_nr(current);
	uid_t uid = from_kuid(&init_user_ns, task_uid(current));
	uid_t loginuid = from_kuid(&init_user_ns, audit_get_loginuid(current));
	unsigned int sessionid = audit_get_sessionid(current);

	ab = audit_log_start(audit_context(), GFP_KERNEL, AUDIT_TTY);
	if (ab) {
		char name[sizeof(current->comm)];

		audit_log_format(ab, "%s pid=%u uid=%u auid=%u ses=%u major=%d"
				 " minor=%d comm=", description, pid, uid,
				 loginuid, sessionid, MAJOR(dev), MINOR(dev));
		get_task_comm(name, current);
		audit_log_untrustedstring(ab, name);
		audit_log_format(ab, " data=");
		audit_log_n_hex(ab, data, size);
		audit_log_end(ab);
	}
}

/*
 *	tty_audit_buf_push	-	Push buffered data out
 *
 *	Generate an audit message from the contents of @buf, which is owned by
 *	the current task.  @buf->mutex must be locked.
 */
static void tty_audit_buf_push(struct tty_audit_buf *buf)
{
	if (buf->valid == 0)
		return;
	if (audit_enabled == AUDIT_OFF) {
		buf->valid = 0;
		return;
	}
	tty_audit_log("tty", buf->dev, buf->data, buf->valid);
	buf->valid = 0;
}

/**
 *	tty_audit_exit	-	Handle a task exit
 *
 *	Make sure all buffered data is written out and deallocate the buffer.
 *	Only needs to be called if current->signal->tty_audit_buf != %NULL.
 *
 *	The process is single-threaded at this point; no other threads share
 *	current->signal.
 */
void tty_audit_exit(void)
{
	struct tty_audit_buf *buf;

	buf = xchg(&current->signal->tty_audit_buf, ERR_PTR(-ESRCH));
	if (!buf)
		return;

	tty_audit_buf_push(buf);
	tty_audit_buf_free(buf);
}

/*
 *	tty_audit_fork	-	Copy TTY audit state for a new task
 *
 *	Set up TTY audit state in @sig from current.  @sig needs no locking.
 */
void tty_audit_fork(struct signal_struct *sig)
{
	sig->audit_tty = current->signal->audit_tty;
}

/*
 *	tty_audit_tiocsti	-	Log TIOCSTI
 */
void tty_audit_tiocsti(struct tty_struct *tty, char ch)
{
	dev_t dev;

	dev = MKDEV(tty->driver->major, tty->driver->minor_start) + tty->index;
	if (tty_audit_push())
		return;

	if (audit_enabled)
		tty_audit_log("ioctl=TIOCSTI", dev, &ch, 1);
}

/*
 *	tty_audit_push	-	Flush current's pending audit data
 *
 *	Returns 0 if success, -EPERM if tty audit is disabled
 */
int tty_audit_push(void)
{
	struct tty_audit_buf *buf;

	if (~current->signal->audit_tty & AUDIT_TTY_ENABLE)
		return -EPERM;

	buf = tty_audit_buf_ref();
	if (!IS_ERR_OR_NULL(buf)) {
		mutex_lock(&buf->mutex);
		tty_audit_buf_push(buf);
		mutex_unlock(&buf->mutex);
	}
	return 0;
}

/*
 *	tty_audit_buf_get	-	Get an audit buffer.
 *
 *	Get an audit buffer, allocate it if necessary.  Return %NULL
 *	if out of memory or ERR_PTR(-ESRCH) if tty_audit_exit() has already
 *	occurred.  Otherwise, return a new reference to the buffer.
 */
static struct tty_audit_buf *tty_audit_buf_get(void)
{
	struct tty_audit_buf *buf;

	buf = tty_audit_buf_ref();
	if (buf)
		return buf;

	buf = tty_audit_buf_alloc();
	if (buf == NULL) {
		audit_log_lost("out of memory in TTY auditing");
		return NULL;
	}

	/* Race to use this buffer, free it if another wins */
	if (cmpxchg(&current->signal->tty_audit_buf, NULL, buf) != NULL)
		tty_audit_buf_free(buf);
	return tty_audit_buf_ref();
}

/*
 *	tty_audit_add_data	-	Add data for TTY auditing.
 *
 *	Audit @data of @size from @tty, if necessary.
 */
void tty_audit_add_data(struct tty_struct *tty, const void *data, size_t size)
{
	struct tty_audit_buf *buf;
	unsigned int icanon = !!L_ICANON(tty);
	unsigned int audit_tty;
	dev_t dev;

	audit_tty = READ_ONCE(current->signal->audit_tty);
	if (~audit_tty & AUDIT_TTY_ENABLE)
		return;

	if (unlikely(size == 0))
		return;

	if (tty->driver->type == TTY_DRIVER_TYPE_PTY
	    && tty->driver->subtype == PTY_TYPE_MASTER)
		return;

	if ((~audit_tty & AUDIT_TTY_LOG_PASSWD) && icanon && !L_ECHO(tty))
		return;

	buf = tty_audit_buf_get();
	if (IS_ERR_OR_NULL(buf))
		return;

	mutex_lock(&buf->mutex);
	dev = MKDEV(tty->driver->major, tty->driver->minor_start) + tty->index;
	if (buf->dev != dev || buf->icanon != icanon) {
		tty_audit_buf_push(buf);
		buf->dev = dev;
		buf->icanon = icanon;
	}
	do {
		size_t run;

		run = N_TTY_BUF_SIZE - buf->valid;
		if (run > size)
			run = size;
		memcpy(buf->data + buf->valid, data, run);
		buf->valid += run;
		data += run;
		size -= run;
		if (buf->valid == N_TTY_BUF_SIZE)
			tty_audit_buf_push(buf);
	} while (size != 0);
	mutex_unlock(&buf->mutex);
}