linux/drivers/char/tty_audit.c
Al Viro 1e641743f0 Audit: Log TIOCSTI
AUDIT_TTY records currently log all data read by processes marked for
TTY input auditing, even if the data was "pushed back" using the TIOCSTI
ioctl, not typed by the user.

This patch records all TIOCSTI calls to disambiguate the input.  It
generates one audit message per character pushed back; considering
TIOCSTI is used very rarely, this simple solution is probably good
enough.  (The only program I could find that uses TIOCSTI is mailx/nail
in "header editing" mode, e.g. using the ~h escape.  mailx is used very
rarely, and the escapes are used even rarer.)

Signed-Off-By: Miloslav Trmac <mitr@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: James Morris <jmorris@namei.org>
2008-12-09 20:32:06 +11:00

349 lines
8.3 KiB
C

/*
* Creating audit events from TTY input.
*
* Copyright (C) 2007 Red Hat, Inc. All rights reserved. This copyrighted
* material is made available to anyone wishing to use, modify, copy, or
* redistribute it subject to the terms and conditions of the GNU General
* Public License v.2.
*
* Authors: Miloslav Trmac <mitr@redhat.com>
*/
#include <linux/audit.h>
#include <linux/file.h>
#include <linux/fdtable.h>
#include <linux/tty.h>
struct tty_audit_buf {
atomic_t count;
struct mutex mutex; /* Protects all data below */
int major, minor; /* 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_alloc(int major, int minor,
int icanon)
{
struct tty_audit_buf *buf;
buf = kmalloc(sizeof(*buf), GFP_KERNEL);
if (!buf)
goto err;
if (PAGE_SIZE != N_TTY_BUF_SIZE)
buf->data = kmalloc(N_TTY_BUF_SIZE, GFP_KERNEL);
else
buf->data = (unsigned char *)__get_free_page(GFP_KERNEL);
if (!buf->data)
goto err_buf;
atomic_set(&buf->count, 1);
mutex_init(&buf->mutex);
buf->major = major;
buf->minor = minor;
buf->icanon = icanon;
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);
if (PAGE_SIZE != N_TTY_BUF_SIZE)
kfree(buf->data);
else
free_page((unsigned long)buf->data);
kfree(buf);
}
static void tty_audit_buf_put(struct tty_audit_buf *buf)
{
if (atomic_dec_and_test(&buf->count))
tty_audit_buf_free(buf);
}
static void tty_audit_log(const char *description, struct task_struct *tsk,
uid_t loginuid, unsigned sessionid, int major,
int minor, unsigned char *data, size_t size)
{
struct audit_buffer *ab;
ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_TTY);
if (ab) {
char name[sizeof(tsk->comm)];
uid_t uid = task_uid(tsk);
audit_log_format(ab, "%s pid=%u uid=%u auid=%u ses=%u "
"major=%d minor=%d comm=", description,
tsk->pid, uid, loginuid, sessionid,
major, minor);
get_task_comm(name, tsk);
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
* @tsk with @loginuid. @buf->mutex must be locked.
*/
static void tty_audit_buf_push(struct task_struct *tsk, uid_t loginuid,
unsigned int sessionid,
struct tty_audit_buf *buf)
{
if (buf->valid == 0)
return;
if (audit_enabled == 0)
return;
tty_audit_log("tty", tsk, loginuid, sessionid, buf->major, buf->minor,
buf->data, buf->valid);
buf->valid = 0;
}
/**
* tty_audit_buf_push_current - 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_current(struct tty_audit_buf *buf)
{
uid_t auid = audit_get_loginuid(current);
unsigned int sessionid = audit_get_sessionid(current);
tty_audit_buf_push(current, auid, sessionid, buf);
}
/**
* 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.
*/
void tty_audit_exit(void)
{
struct tty_audit_buf *buf;
spin_lock_irq(&current->sighand->siglock);
buf = current->signal->tty_audit_buf;
current->signal->tty_audit_buf = NULL;
spin_unlock_irq(&current->sighand->siglock);
if (!buf)
return;
mutex_lock(&buf->mutex);
tty_audit_buf_push_current(buf);
mutex_unlock(&buf->mutex);
tty_audit_buf_put(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)
{
spin_lock_irq(&current->sighand->siglock);
sig->audit_tty = current->signal->audit_tty;
spin_unlock_irq(&current->sighand->siglock);
sig->tty_audit_buf = NULL;
}
/**
* tty_audit_tiocsti - Log TIOCSTI
*/
void tty_audit_tiocsti(struct tty_struct *tty, char ch)
{
struct tty_audit_buf *buf;
int major, minor, should_audit;
spin_lock_irq(&current->sighand->siglock);
should_audit = current->signal->audit_tty;
buf = current->signal->tty_audit_buf;
if (buf)
atomic_inc(&buf->count);
spin_unlock_irq(&current->sighand->siglock);
major = tty->driver->major;
minor = tty->driver->minor_start + tty->index;
if (buf) {
mutex_lock(&buf->mutex);
if (buf->major == major && buf->minor == minor)
tty_audit_buf_push_current(buf);
mutex_unlock(&buf->mutex);
tty_audit_buf_put(buf);
}
if (should_audit && audit_enabled) {
uid_t auid;
unsigned int sessionid;
auid = audit_get_loginuid(current);
sessionid = audit_get_sessionid(current);
tty_audit_log("ioctl=TIOCSTI", current, auid, sessionid, major,
minor, &ch, 1);
}
}
/**
* tty_audit_push_task - Flush task's pending audit data
*/
void tty_audit_push_task(struct task_struct *tsk, uid_t loginuid, u32 sessionid)
{
struct tty_audit_buf *buf;
spin_lock_irq(&tsk->sighand->siglock);
buf = tsk->signal->tty_audit_buf;
if (buf)
atomic_inc(&buf->count);
spin_unlock_irq(&tsk->sighand->siglock);
if (!buf)
return;
mutex_lock(&buf->mutex);
tty_audit_buf_push(tsk, loginuid, sessionid, buf);
mutex_unlock(&buf->mutex);
tty_audit_buf_put(buf);
}
/**
* tty_audit_buf_get - Get an audit buffer.
*
* Get an audit buffer for @tty, allocate it if necessary. Return %NULL
* if TTY auditing is disabled or out of memory. Otherwise, return a new
* reference to the buffer.
*/
static struct tty_audit_buf *tty_audit_buf_get(struct tty_struct *tty)
{
struct tty_audit_buf *buf, *buf2;
buf = NULL;
buf2 = NULL;
spin_lock_irq(&current->sighand->siglock);
if (likely(!current->signal->audit_tty))
goto out;
buf = current->signal->tty_audit_buf;
if (buf) {
atomic_inc(&buf->count);
goto out;
}
spin_unlock_irq(&current->sighand->siglock);
buf2 = tty_audit_buf_alloc(tty->driver->major,
tty->driver->minor_start + tty->index,
tty->icanon);
if (buf2 == NULL) {
audit_log_lost("out of memory in TTY auditing");
return NULL;
}
spin_lock_irq(&current->sighand->siglock);
if (!current->signal->audit_tty)
goto out;
buf = current->signal->tty_audit_buf;
if (!buf) {
current->signal->tty_audit_buf = buf2;
buf = buf2;
buf2 = NULL;
}
atomic_inc(&buf->count);
/* Fall through */
out:
spin_unlock_irq(&current->sighand->siglock);
if (buf2)
tty_audit_buf_free(buf2);
return buf;
}
/**
* 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, unsigned char *data,
size_t size)
{
struct tty_audit_buf *buf;
int major, minor;
if (unlikely(size == 0))
return;
if (tty->driver->type == TTY_DRIVER_TYPE_PTY
&& tty->driver->subtype == PTY_TYPE_MASTER)
return;
buf = tty_audit_buf_get(tty);
if (!buf)
return;
mutex_lock(&buf->mutex);
major = tty->driver->major;
minor = tty->driver->minor_start + tty->index;
if (buf->major != major || buf->minor != minor
|| buf->icanon != tty->icanon) {
tty_audit_buf_push_current(buf);
buf->major = major;
buf->minor = minor;
buf->icanon = tty->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_current(buf);
} while (size != 0);
mutex_unlock(&buf->mutex);
tty_audit_buf_put(buf);
}
/**
* tty_audit_push - Push buffered data out
*
* Make sure no audit data is pending for @tty on the current process.
*/
void tty_audit_push(struct tty_struct *tty)
{
struct tty_audit_buf *buf;
spin_lock_irq(&current->sighand->siglock);
if (likely(!current->signal->audit_tty)) {
spin_unlock_irq(&current->sighand->siglock);
return;
}
buf = current->signal->tty_audit_buf;
if (buf)
atomic_inc(&buf->count);
spin_unlock_irq(&current->sighand->siglock);
if (buf) {
int major, minor;
major = tty->driver->major;
minor = tty->driver->minor_start + tty->index;
mutex_lock(&buf->mutex);
if (buf->major == major && buf->minor == minor)
tty_audit_buf_push_current(buf);
mutex_unlock(&buf->mutex);
tty_audit_buf_put(buf);
}
}