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
15struct tty_audit_buf {
16 struct mutex mutex; /* Protects all data below */
17 dev_t dev; /* The TTY which the data is from */
18 bool icanon;
19 size_t valid;
20 u8 *data; /* Allocated size N_TTY_BUF_SIZE */
21};
22
23static 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
32static struct tty_audit_buf *tty_audit_buf_alloc(void)
33{
34 struct tty_audit_buf *buf;
35
36 buf = kzalloc(size: sizeof(*buf), GFP_KERNEL);
37 if (!buf)
38 goto err;
39
40 buf->data = kmalloc(N_TTY_BUF_SIZE, GFP_KERNEL);
41 if (!buf->data)
42 goto err_buf;
43
44 mutex_init(&buf->mutex);
45
46 return buf;
47
48err_buf:
49 kfree(objp: buf);
50err:
51 return NULL;
52}
53
54static void tty_audit_buf_free(struct tty_audit_buf *buf)
55{
56 WARN_ON(buf->valid != 0);
57 kfree(objp: buf->data);
58 kfree(objp: buf);
59}
60
61static void tty_audit_log(const char *description, dev_t dev,
62 const u8 *data, size_t size)
63{
64 struct audit_buffer *ab;
65 pid_t pid = task_pid_nr(current);
66 uid_t uid = from_kuid(to: &init_user_ns, task_uid(current));
67 uid_t loginuid = from_kuid(to: &init_user_ns, uid: audit_get_loginuid(current));
68 unsigned int sessionid = audit_get_sessionid(current);
69 char name[TASK_COMM_LEN];
70
71 ab = audit_log_start(ctx: audit_context(), GFP_KERNEL, AUDIT_TTY);
72 if (!ab)
73 return;
74
75 audit_log_format(ab, fmt: "%s pid=%u uid=%u auid=%u ses=%u major=%d minor=%d comm=",
76 description, pid, uid, loginuid, sessionid,
77 MAJOR(dev), MINOR(dev));
78 get_task_comm(name, current);
79 audit_log_untrustedstring(ab, string: name);
80 audit_log_format(ab, fmt: " data=");
81 audit_log_n_hex(ab, buf: data, len: size);
82 audit_log_end(ab);
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 */
91static 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(description: "tty", dev: buf->dev, data: buf->data, size: 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 */
112void 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 */
129void 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 */
137void tty_audit_tiocsti(const struct tty_struct *tty, u8 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(description: "ioctl=TIOCSTI", dev, data: &ch, size: 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 */
154int 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(ptr: buf)) {
163 mutex_lock(&buf->mutex);
164 tty_audit_buf_push(buf);
165 mutex_unlock(lock: &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 */
177static 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(message: "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 */
202void tty_audit_add_data(const struct tty_struct *tty, const void *data,
203 size_t size)
204{
205 struct tty_audit_buf *buf;
206 unsigned int audit_tty;
207 bool icanon = L_ICANON(tty);
208 dev_t dev;
209
210 audit_tty = READ_ONCE(current->signal->audit_tty);
211 if (~audit_tty & AUDIT_TTY_ENABLE)
212 return;
213
214 if (unlikely(size == 0))
215 return;
216
217 if (tty->driver->type == TTY_DRIVER_TYPE_PTY
218 && tty->driver->subtype == PTY_TYPE_MASTER)
219 return;
220
221 if ((~audit_tty & AUDIT_TTY_LOG_PASSWD) && icanon && !L_ECHO(tty))
222 return;
223
224 buf = tty_audit_buf_get();
225 if (IS_ERR_OR_NULL(ptr: buf))
226 return;
227
228 mutex_lock(&buf->mutex);
229 dev = MKDEV(tty->driver->major, tty->driver->minor_start) + tty->index;
230 if (buf->dev != dev || buf->icanon != icanon) {
231 tty_audit_buf_push(buf);
232 buf->dev = dev;
233 buf->icanon = icanon;
234 }
235 do {
236 size_t run;
237
238 run = N_TTY_BUF_SIZE - buf->valid;
239 if (run > size)
240 run = size;
241 memcpy(buf->data + buf->valid, data, run);
242 buf->valid += run;
243 data += run;
244 size -= run;
245 if (buf->valid == N_TTY_BUF_SIZE)
246 tty_audit_buf_push(buf);
247 } while (size != 0);
248 mutex_unlock(lock: &buf->mutex);
249}
250

source code of linux/drivers/tty/tty_audit.c