/*
   * 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/slab.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,
  						 unsigned icanon)
  {
  	struct tty_audit_buf *buf;
  
  	buf = kmalloc(sizeof(*buf), GFP_KERNEL);
  	if (!buf)
  		goto err;
  	buf->data = kmalloc(N_TTY_BUF_SIZE, 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);
  	kfree(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, int major, int minor,
  			  unsigned char *data, size_t size)
  {
  	struct audit_buffer *ab;
  	struct task_struct *tsk = current;
  	uid_t uid = from_kuid(&init_user_ns, task_uid(tsk));
  	uid_t loginuid = from_kuid(&init_user_ns, audit_get_loginuid(tsk));
  	unsigned int sessionid = audit_get_sessionid(tsk);
  
  	ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_TTY);
  	if (ab) {
  		char name[sizeof(tsk->comm)];
  
  		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
   *	the current task.  @buf->mutex must be locked.
   */
  static void tty_audit_buf_push(struct tty_audit_buf *buf)
  {
  	if (buf->valid == 0)
  		return;
  	if (audit_enabled == 0) {
  		buf->valid = 0;
  		return;
  	}
  	tty_audit_log("tty", buf->major, buf->minor, buf->data, buf->valid);
  	buf->valid = 0;
  }
  
  /**
   *	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;
  
  	buf = current->signal->tty_audit_buf;
  	current->signal->tty_audit_buf = NULL;
  	if (!buf)
  		return;
  
  	mutex_lock(&buf->mutex);
  	tty_audit_buf_push(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)
  {
  	sig->audit_tty = current->signal->audit_tty;
  	sig->audit_tty_log_passwd = current->signal->audit_tty_log_passwd;
  }
  
  /**
   *	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;
  	unsigned long flags;
  
  	spin_lock_irqsave(&current->sighand->siglock, flags);
  	should_audit = current->signal->audit_tty;
  	buf = current->signal->tty_audit_buf;
  	if (buf)
  		atomic_inc(&buf->count);
  	spin_unlock_irqrestore(&current->sighand->siglock, flags);
  
  	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(buf);
  		mutex_unlock(&buf->mutex);
  		tty_audit_buf_put(buf);
  	}
  
  	if (should_audit && audit_enabled) {
  		kuid_t auid;
  		unsigned int sessionid;
  
  		auid = audit_get_loginuid(current);
  		sessionid = audit_get_sessionid(current);
  		tty_audit_log("ioctl=TIOCSTI", major, minor, &ch, 1);
  	}
  }
  
  /**
   * tty_audit_push_current -	Flush current's pending audit data
   *
   * Try to lock sighand and get a reference to the tty audit buffer if available.
   * Flush the buffer or return an appropriate error code.
   */
  int tty_audit_push_current(void)
  {
  	struct tty_audit_buf *buf = ERR_PTR(-EPERM);
  	struct task_struct *tsk = current;
  	unsigned long flags;
  
  	if (!lock_task_sighand(tsk, &flags))
  		return -ESRCH;
  
  	if (tsk->signal->audit_tty) {
  		buf = tsk->signal->tty_audit_buf;
  		if (buf)
  			atomic_inc(&buf->count);
  	}
  	unlock_task_sighand(tsk, &flags);
  
  	/*
  	 * Return 0 when signal->audit_tty set
  	 * but tsk->signal->tty_audit_buf == NULL.
  	 */
  	if (!buf || IS_ERR(buf))
  		return PTR_ERR(buf);
  
  	mutex_lock(&buf->mutex);
  	tty_audit_buf_push(buf);
  	mutex_unlock(&buf->mutex);
  
  	tty_audit_buf_put(buf);
  	return 0;
  }
  
  /**
   *	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,
  		unsigned icanon)
  {
  	struct tty_audit_buf *buf, *buf2;
  	unsigned long flags;
  
  	buf = NULL;
  	buf2 = NULL;
  	spin_lock_irqsave(&current->sighand->siglock, flags);
  	if (likely(!current->signal->audit_tty))
  		goto out;
  	buf = current->signal->tty_audit_buf;
  	if (buf) {
  		atomic_inc(&buf->count);
  		goto out;
  	}
  	spin_unlock_irqrestore(&current->sighand->siglock, flags);
  
  	buf2 = tty_audit_buf_alloc(tty->driver->major,
  				   tty->driver->minor_start + tty->index,
  				   icanon);
  	if (buf2 == NULL) {
  		audit_log_lost("out of memory in TTY auditing");
  		return NULL;
  	}
  
  	spin_lock_irqsave(&current->sighand->siglock, flags);
  	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_irqrestore(&current->sighand->siglock, flags);
  	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, unsigned icanon)
  {
  	struct tty_audit_buf *buf;
  	int major, minor;
  	int audit_log_tty_passwd;
  	unsigned long flags;
  
  	if (unlikely(size == 0))
  		return;
  
  	spin_lock_irqsave(&current->sighand->siglock, flags);
  	audit_log_tty_passwd = current->signal->audit_tty_log_passwd;
  	spin_unlock_irqrestore(&current->sighand->siglock, flags);
  	if (!audit_log_tty_passwd && icanon && !L_ECHO(tty))
  		return;
  
  	if (tty->driver->type == TTY_DRIVER_TYPE_PTY
  	    && tty->driver->subtype == PTY_TYPE_MASTER)
  		return;
  
  	buf = tty_audit_buf_get(tty, icanon);
  	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 != icanon) {
  		tty_audit_buf_push(buf);
  		buf->major = major;
  		buf->minor = minor;
  		buf->icanon = 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(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;
  	unsigned long flags;
  
  	spin_lock_irqsave(&current->sighand->siglock, flags);
  	if (likely(!current->signal->audit_tty)) {
  		spin_unlock_irqrestore(&current->sighand->siglock, flags);
  		return;
  	}
  	buf = current->signal->tty_audit_buf;
  	if (buf)
  		atomic_inc(&buf->count);
  	spin_unlock_irqrestore(&current->sighand->siglock, flags);
  
  	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(buf);
  		mutex_unlock(&buf->mutex);
  		tty_audit_buf_put(buf);
  	}
  }