blob: d222012c1b0ca039a4c41c6f7a450a4fbe2ba8a0 [file] [log] [blame]
/*
* 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/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);
}
/**
* 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,
struct tty_audit_buf *buf)
{
struct audit_buffer *ab;
if (buf->valid == 0)
return;
if (audit_enabled == 0)
return;
ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_TTY);
if (ab) {
char name[sizeof(tsk->comm)];
audit_log_format(ab, "tty pid=%u uid=%u auid=%u major=%d "
"minor=%d comm=", tsk->pid, tsk->uid,
loginuid, buf->major, buf->minor);
get_task_comm(name, tsk);
audit_log_untrustedstring(ab, name);
audit_log_format(ab, " data=");
audit_log_n_untrustedstring(ab, buf->valid, buf->data);
audit_log_end(ab);
}
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)
{
tty_audit_buf_push(current, audit_get_loginuid(current->audit_context),
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_push_task - Flush task's pending audit data
*/
void tty_audit_push_task(struct task_struct *tsk, uid_t loginuid)
{
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, 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;
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);
}
}
/**
* tty_audit_opening - A TTY is being opened.
*
* As a special hack, tasks that close all their TTYs and open new ones
* are assumed to be system daemons (e.g. getty) and auditing is
* automatically disabled for them.
*/
void tty_audit_opening(void)
{
int disable;
disable = 1;
spin_lock_irq(&current->sighand->siglock);
if (current->signal->audit_tty == 0)
disable = 0;
spin_unlock_irq(&current->sighand->siglock);
if (!disable)
return;
task_lock(current);
if (current->files) {
struct fdtable *fdt;
unsigned i;
/*
* We don't take a ref to the file, so we must hold ->file_lock
* instead.
*/
spin_lock(&current->files->file_lock);
fdt = files_fdtable(current->files);
for (i = 0; i < fdt->max_fds; i++) {
struct file *filp;
filp = fcheck_files(current->files, i);
if (filp && is_tty(filp)) {
disable = 0;
break;
}
}
spin_unlock(&current->files->file_lock);
}
task_unlock(current);
if (!disable)
return;
spin_lock_irq(&current->sighand->siglock);
current->signal->audit_tty = 0;
spin_unlock_irq(&current->sighand->siglock);
}