1 // SPDX-License-Identifier: GPL-2.0
3 * Creating audit events from TTY input.
5 * Copyright (C) 2007 Red Hat, Inc. All rights reserved.
7 * Authors: Miloslav Trmac <mitr@redhat.com>
10 #include <linux/audit.h>
11 #include <linux/slab.h>
12 #include <linux/tty.h>
15 struct tty_audit_buf {
16 struct mutex mutex; /* Protects all data below */
17 dev_t dev; /* The TTY which the data is from */
20 u8 *data; /* Allocated size N_TTY_BUF_SIZE */
23 static struct tty_audit_buf *tty_audit_buf_ref(void)
25 struct tty_audit_buf *buf;
27 buf = current->signal->tty_audit_buf;
28 WARN_ON(buf == ERR_PTR(-ESRCH));
32 static struct tty_audit_buf *tty_audit_buf_alloc(void)
34 struct tty_audit_buf *buf;
36 buf = kzalloc(sizeof(*buf), GFP_KERNEL);
40 buf->data = kmalloc(N_TTY_BUF_SIZE, GFP_KERNEL);
44 mutex_init(&buf->mutex);
54 static void tty_audit_buf_free(struct tty_audit_buf *buf)
56 WARN_ON(buf->valid != 0);
61 static void tty_audit_log(const char *description, dev_t dev,
62 const u8 *data, size_t size)
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 char name[TASK_COMM_LEN];
71 ab = audit_log_start(audit_context(), GFP_KERNEL, AUDIT_TTY);
75 audit_log_format(ab, "%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, name);
80 audit_log_format(ab, " data=");
81 audit_log_n_hex(ab, data, size);
86 * tty_audit_buf_push - Push buffered data out
88 * Generate an audit message from the contents of @buf, which is owned by
89 * the current task. @buf->mutex must be locked.
91 static void tty_audit_buf_push(struct tty_audit_buf *buf)
95 if (audit_enabled == AUDIT_OFF) {
99 tty_audit_log("tty", buf->dev, buf->data, buf->valid);
104 * tty_audit_exit - Handle a task exit
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.
109 * The process is single-threaded at this point; no other threads share
112 void tty_audit_exit(void)
114 struct tty_audit_buf *buf;
116 buf = xchg(¤t->signal->tty_audit_buf, ERR_PTR(-ESRCH));
120 tty_audit_buf_push(buf);
121 tty_audit_buf_free(buf);
125 * tty_audit_fork - Copy TTY audit state for a new task
127 * Set up TTY audit state in @sig from current. @sig needs no locking.
129 void tty_audit_fork(struct signal_struct *sig)
131 sig->audit_tty = current->signal->audit_tty;
135 * tty_audit_tiocsti - Log TIOCSTI
137 void tty_audit_tiocsti(const struct tty_struct *tty, u8 ch)
141 dev = MKDEV(tty->driver->major, tty->driver->minor_start) + tty->index;
142 if (tty_audit_push())
146 tty_audit_log("ioctl=TIOCSTI", dev, &ch, 1);
150 * tty_audit_push - Flush current's pending audit data
152 * Returns 0 if success, -EPERM if tty audit is disabled
154 int tty_audit_push(void)
156 struct tty_audit_buf *buf;
158 if (~current->signal->audit_tty & AUDIT_TTY_ENABLE)
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);
171 * tty_audit_buf_get - Get an audit buffer.
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.
177 static struct tty_audit_buf *tty_audit_buf_get(void)
179 struct tty_audit_buf *buf;
181 buf = tty_audit_buf_ref();
185 buf = tty_audit_buf_alloc();
187 audit_log_lost("out of memory in TTY auditing");
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();
198 * tty_audit_add_data - Add data for TTY auditing.
200 * Audit @data of @size from @tty, if necessary.
202 void tty_audit_add_data(const struct tty_struct *tty, const void *data,
205 struct tty_audit_buf *buf;
206 unsigned int audit_tty;
207 bool icanon = L_ICANON(tty);
210 audit_tty = READ_ONCE(current->signal->audit_tty);
211 if (~audit_tty & AUDIT_TTY_ENABLE)
214 if (unlikely(size == 0))
217 if (tty->driver->type == TTY_DRIVER_TYPE_PTY
218 && tty->driver->subtype == PTY_TYPE_MASTER)
221 if ((~audit_tty & AUDIT_TTY_LOG_PASSWD) && icanon && !L_ECHO(tty))
224 buf = tty_audit_buf_get();
225 if (IS_ERR_OR_NULL(buf))
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);
233 buf->icanon = icanon;
238 run = N_TTY_BUF_SIZE - buf->valid;
241 memcpy(buf->data + buf->valid, data, run);
245 if (buf->valid == N_TTY_BUF_SIZE)
246 tty_audit_buf_push(buf);
248 mutex_unlock(&buf->mutex);