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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 <[email protected]>
8 */
9
10#include <linux/audit.h>
11#include <linux/slab.h>
12#include <linux/tty.h>
13#include "tty.h"
14
15#define TTY_AUDIT_BUF_SIZE 4096
16
17struct tty_audit_buf {
18 struct mutex mutex; /* Protects all data below */
19 dev_t dev; /* The TTY which the data is from */
20 bool icanon;
21 size_t valid;
22 u8 *data; /* Allocated size TTY_AUDIT_BUF_SIZE */
23};
24
25static struct tty_audit_buf *tty_audit_buf_ref(void)
26{
27 struct tty_audit_buf *buf;
28
29 buf = current->signal->tty_audit_buf;
30 WARN_ON(buf == ERR_PTR(-ESRCH));
31 return buf;
32}
33
34static struct tty_audit_buf *tty_audit_buf_alloc(void)
35{
36 struct tty_audit_buf *buf;
37
38 buf = kzalloc_obj(*buf);
39 if (!buf)
40 goto err;
41
42 buf->data = kmalloc(TTY_AUDIT_BUF_SIZE, GFP_KERNEL);
43 if (!buf->data)
44 goto err_buf;
45
46 mutex_init(&buf->mutex);
47
48 return buf;
49
50err_buf:
51 kfree(buf);
52err:
53 return NULL;
54}
55
56static void tty_audit_buf_free(struct tty_audit_buf *buf)
57{
58 WARN_ON(buf->valid != 0);
59 kfree(buf->data);
60 kfree(buf);
61}
62
63static void tty_audit_log(const char *description, dev_t dev,
64 const u8 *data, size_t size)
65{
66 struct audit_buffer *ab;
67 pid_t pid = task_pid_nr(current);
68 uid_t uid = from_kuid(&init_user_ns, task_uid(current));
69 uid_t loginuid = from_kuid(&init_user_ns, audit_get_loginuid(current));
70 unsigned int sessionid = audit_get_sessionid(current);
71 char name[TASK_COMM_LEN];
72
73 ab = audit_log_start(audit_context(), GFP_KERNEL, AUDIT_TTY);
74 if (!ab)
75 return;
76
77 audit_log_format(ab, "%s pid=%u uid=%u auid=%u ses=%u major=%d minor=%d comm=",
78 description, pid, uid, loginuid, sessionid,
79 MAJOR(dev), MINOR(dev));
80 get_task_comm(name, current);
81 audit_log_untrustedstring(ab, name);
82 audit_log_format(ab, " data=");
83 audit_log_n_hex(ab, data, size);
84 audit_log_end(ab);
85}
86
87/*
88 * tty_audit_buf_push - Push buffered data out
89 *
90 * Generate an audit message from the contents of @buf, which is owned by
91 * the current task. @buf->mutex must be locked.
92 */
93static void tty_audit_buf_push(struct tty_audit_buf *buf)
94{
95 if (buf->valid == 0)
96 return;
97 if (audit_enabled == AUDIT_OFF) {
98 buf->valid = 0;
99 return;
100 }
101 tty_audit_log("tty", buf->dev, buf->data, buf->valid);
102 buf->valid = 0;
103}
104
105/**
106 * tty_audit_exit - Handle a task exit
107 *
108 * Make sure all buffered data is written out and deallocate the buffer.
109 * Only needs to be called if current->signal->tty_audit_buf != %NULL.
110 *
111 * The process is single-threaded at this point; no other threads share
112 * current->signal.
113 */
114void tty_audit_exit(void)
115{
116 struct tty_audit_buf *buf;
117
118 buf = xchg(&current->signal->tty_audit_buf, ERR_PTR(-ESRCH));
119 if (!buf)
120 return;
121
122 tty_audit_buf_push(buf);
123 tty_audit_buf_free(buf);
124}
125
126/*
127 * tty_audit_fork - Copy TTY audit state for a new task
128 *
129 * Set up TTY audit state in @sig from current. @sig needs no locking.
130 */
131void tty_audit_fork(struct signal_struct *sig)
132{
133 sig->audit_tty = current->signal->audit_tty;
134}
135
136/*
137 * tty_audit_tiocsti - Log TIOCSTI
138 */
139void tty_audit_tiocsti(const struct tty_struct *tty, u8 ch)
140{
141 dev_t dev;
142
143 dev = MKDEV(tty->driver->major, tty->driver->minor_start) + tty->index;
144 if (tty_audit_push())
145 return;
146
147 if (audit_enabled)
148 tty_audit_log("ioctl=TIOCSTI", dev, &ch, 1);
149}
150
151/*
152 * tty_audit_push - Flush current's pending audit data
153 *
154 * Returns 0 if success, -EPERM if tty audit is disabled
155 */
156int tty_audit_push(void)
157{
158 struct tty_audit_buf *buf;
159
160 if (~current->signal->audit_tty & AUDIT_TTY_ENABLE)
161 return -EPERM;
162
163 buf = tty_audit_buf_ref();
164 if (!IS_ERR_OR_NULL(buf)) {
165 mutex_lock(&buf->mutex);
166 tty_audit_buf_push(buf);
167 mutex_unlock(&buf->mutex);
168 }
169 return 0;
170}
171
172/*
173 * tty_audit_buf_get - Get an audit buffer.
174 *
175 * Get an audit buffer, allocate it if necessary. Return %NULL
176 * if out of memory or ERR_PTR(-ESRCH) if tty_audit_exit() has already
177 * occurred. Otherwise, return a new reference to the buffer.
178 */
179static struct tty_audit_buf *tty_audit_buf_get(void)
180{
181 struct tty_audit_buf *buf;
182
183 buf = tty_audit_buf_ref();
184 if (buf)
185 return buf;
186
187 buf = tty_audit_buf_alloc();
188 if (buf == NULL) {
189 audit_log_lost("out of memory in TTY auditing");
190 return NULL;
191 }
192
193 /* Race to use this buffer, free it if another wins */
194 if (cmpxchg(&current->signal->tty_audit_buf, NULL, buf) != NULL)
195 tty_audit_buf_free(buf);
196 return tty_audit_buf_ref();
197}
198
199/*
200 * tty_audit_add_data - Add data for TTY auditing.
201 *
202 * Audit @data of @size from @tty, if necessary.
203 */
204void tty_audit_add_data(const struct tty_struct *tty, const void *data,
205 size_t size)
206{
207 struct tty_audit_buf *buf;
208 unsigned int audit_tty;
209 bool icanon = L_ICANON(tty);
210 dev_t dev;
211
212 audit_tty = READ_ONCE(current->signal->audit_tty);
213 if (~audit_tty & AUDIT_TTY_ENABLE)
214 return;
215
216 if (unlikely(size == 0))
217 return;
218
219 if (tty->driver->type == TTY_DRIVER_TYPE_PTY
220 && tty->driver->subtype == PTY_TYPE_MASTER)
221 return;
222
223 if ((~audit_tty & AUDIT_TTY_LOG_PASSWD) && icanon && !L_ECHO(tty))
224 return;
225
226 buf = tty_audit_buf_get();
227 if (IS_ERR_OR_NULL(buf))
228 return;
229
230 mutex_lock(&buf->mutex);
231 dev = MKDEV(tty->driver->major, tty->driver->minor_start) + tty->index;
232 if (buf->dev != dev || buf->icanon != icanon) {
233 tty_audit_buf_push(buf);
234 buf->dev = dev;
235 buf->icanon = icanon;
236 }
237 do {
238 size_t run;
239
240 run = TTY_AUDIT_BUF_SIZE - buf->valid;
241 if (run > size)
242 run = size;
243 memcpy(buf->data + buf->valid, data, run);
244 buf->valid += run;
245 data += run;
246 size -= run;
247 if (buf->valid == TTY_AUDIT_BUF_SIZE)
248 tty_audit_buf_push(buf);
249 } while (size != 0);
250 mutex_unlock(&buf->mutex);
251}