/**
   * eCryptfs: Linux filesystem encryption layer
   *
   * Copyright (C) 2008 International Business Machines Corp.
   *   Author(s): Michael A. Halcrow <mhalcrow@us.ibm.com>
   *
   * This program is free software; you can redistribute it and/or
   * modify it under the terms of the GNU General Public License version
   * 2 as published by the Free Software Foundation.
   *
   * This program is distributed in the hope that it will be useful, but
   * WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   * General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License
   * along with this program; if not, write to the Free Software
   * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
   * 02111-1307, USA.
   */
  
  #include <linux/fs.h>
  #include <linux/hash.h>
  #include <linux/random.h>
  #include <linux/miscdevice.h>
  #include <linux/poll.h>

  #include <linux/slab.h>

  #include <linux/wait.h>
  #include <linux/module.h>
  #include "ecryptfs_kernel.h"
  
  static atomic_t ecryptfs_num_miscdev_opens;
  
  /**
   * ecryptfs_miscdev_poll
   * @file: dev file (ignored)
   * @pt: dev poll table (ignored)
   *
   * Returns the poll mask
   */
  static unsigned int
  ecryptfs_miscdev_poll(struct file *file, poll_table *pt)
  {
  	struct ecryptfs_daemon *daemon;
  	unsigned int mask = 0;

  	uid_t euid = current_euid();

  	int rc;
  
  	mutex_lock(&ecryptfs_daemon_hash_mux);
  	/* TODO: Just use file->private_data? */

  	rc = ecryptfs_find_daemon_by_euid(&daemon, euid, current_user_ns());

  	BUG_ON(rc || !daemon);
  	mutex_lock(&daemon->mux);
  	mutex_unlock(&ecryptfs_daemon_hash_mux);
  	if (daemon->flags & ECRYPTFS_DAEMON_ZOMBIE) {
  		printk(KERN_WARNING "%s: Attempt to poll on zombified "
  		       "daemon
  ", __func__);
  		goto out_unlock_daemon;
  	}
  	if (daemon->flags & ECRYPTFS_DAEMON_IN_READ)
  		goto out_unlock_daemon;
  	if (daemon->flags & ECRYPTFS_DAEMON_IN_POLL)
  		goto out_unlock_daemon;
  	daemon->flags |= ECRYPTFS_DAEMON_IN_POLL;
  	mutex_unlock(&daemon->mux);
  	poll_wait(file, &daemon->wait, pt);
  	mutex_lock(&daemon->mux);
  	if (!list_empty(&daemon->msg_ctx_out_queue))
  		mask |= POLLIN | POLLRDNORM;
  out_unlock_daemon:
  	daemon->flags &= ~ECRYPTFS_DAEMON_IN_POLL;
  	mutex_unlock(&daemon->mux);
  	return mask;
  }
  
  /**
   * ecryptfs_miscdev_open
   * @inode: inode of miscdev handle (ignored)
   * @file: file for miscdev handle (ignored)
   *
   * Returns zero on success; non-zero otherwise
   */
  static int
  ecryptfs_miscdev_open(struct inode *inode, struct file *file)
  {
  	struct ecryptfs_daemon *daemon = NULL;

  	uid_t euid = current_euid();

  	int rc;
  
  	mutex_lock(&ecryptfs_daemon_hash_mux);
  	rc = try_module_get(THIS_MODULE);
  	if (rc == 0) {
  		rc = -EIO;
  		printk(KERN_ERR "%s: Error attempting to increment module use "
  		       "count; rc = [%d]
  ", __func__, rc);
  		goto out_unlock_daemon_list;
  	}

  	rc = ecryptfs_find_daemon_by_euid(&daemon, euid, current_user_ns());

  	if (rc || !daemon) {

  		rc = ecryptfs_spawn_daemon(&daemon, euid, current_user_ns(),

  					   task_pid(current));

  		if (rc) {
  			printk(KERN_ERR "%s: Error attempting to spawn daemon; "
  			       "rc = [%d]
  ", __func__, rc);
  			goto out_module_put_unlock_daemon_list;
  		}
  	}
  	mutex_lock(&daemon->mux);

  	if (daemon->pid != task_pid(current)) {

  		rc = -EINVAL;

  		printk(KERN_ERR "%s: pid [0x%p] has registered with euid [%d], "
  		       "but pid [0x%p] has attempted to open the handle "

  		       "instead
  ", __func__, daemon->pid, daemon->euid,

  		       task_pid(current));

  		goto out_unlock_daemon;
  	}
  	if (daemon->flags & ECRYPTFS_DAEMON_MISCDEV_OPEN) {
  		rc = -EBUSY;
  		printk(KERN_ERR "%s: Miscellaneous device handle may only be "

  		       "opened once per daemon; pid [0x%p] already has this "

  		       "handle open
  ", __func__, daemon->pid);
  		goto out_unlock_daemon;
  	}
  	daemon->flags |= ECRYPTFS_DAEMON_MISCDEV_OPEN;
  	atomic_inc(&ecryptfs_num_miscdev_opens);
  out_unlock_daemon:
  	mutex_unlock(&daemon->mux);
  out_module_put_unlock_daemon_list:
  	if (rc)
  		module_put(THIS_MODULE);
  out_unlock_daemon_list:
  	mutex_unlock(&ecryptfs_daemon_hash_mux);
  	return rc;
  }
  
  /**
   * ecryptfs_miscdev_release
   * @inode: inode of fs/ecryptfs/euid handle (ignored)
   * @file: file for fs/ecryptfs/euid handle (ignored)
   *
   * This keeps the daemon registered until the daemon sends another
   * ioctl to fs/ecryptfs/ctl or until the kernel module unregisters.
   *
   * Returns zero on success; non-zero otherwise
   */
  static int
  ecryptfs_miscdev_release(struct inode *inode, struct file *file)
  {
  	struct ecryptfs_daemon *daemon = NULL;

  	uid_t euid = current_euid();

  	int rc;
  
  	mutex_lock(&ecryptfs_daemon_hash_mux);

  	rc = ecryptfs_find_daemon_by_euid(&daemon, euid, current_user_ns());

  	BUG_ON(rc || !daemon);
  	mutex_lock(&daemon->mux);

  	BUG_ON(daemon->pid != task_pid(current));

  	BUG_ON(!(daemon->flags & ECRYPTFS_DAEMON_MISCDEV_OPEN));
  	daemon->flags &= ~ECRYPTFS_DAEMON_MISCDEV_OPEN;
  	atomic_dec(&ecryptfs_num_miscdev_opens);
  	mutex_unlock(&daemon->mux);
  	rc = ecryptfs_exorcise_daemon(daemon);
  	if (rc) {
  		printk(KERN_CRIT "%s: Fatal error whilst attempting to "
  		       "shut down daemon; rc = [%d]. Please report this "
  		       "bug.
  ", __func__, rc);
  		BUG();
  	}
  	module_put(THIS_MODULE);
  	mutex_unlock(&ecryptfs_daemon_hash_mux);
  	return rc;
  }
  
  /**
   * ecryptfs_send_miscdev
   * @data: Data to send to daemon; may be NULL
   * @data_size: Amount of data to send to daemon
   * @msg_ctx: Message context, which is used to handle the reply. If
   *           this is NULL, then we do not expect a reply.
   * @msg_type: Type of message
   * @msg_flags: Flags for message
   * @daemon: eCryptfs daemon object
   *
   * Add msg_ctx to queue and then, if it exists, notify the blocked
   * miscdevess about the data being available. Must be called with
   * ecryptfs_daemon_hash_mux held.
   *
   * Returns zero on success; non-zero otherwise
   */
  int ecryptfs_send_miscdev(char *data, size_t data_size,
  			  struct ecryptfs_msg_ctx *msg_ctx, u8 msg_type,
  			  u16 msg_flags, struct ecryptfs_daemon *daemon)
  {
  	int rc = 0;
  
  	mutex_lock(&msg_ctx->mux);

  	msg_ctx->msg = kmalloc((sizeof(*msg_ctx->msg) + data_size),
  			       GFP_KERNEL);
  	if (!msg_ctx->msg) {
  		rc = -ENOMEM;
  		printk(KERN_ERR "%s: Out of memory whilst attempting "
  		       "to kmalloc(%zd, GFP_KERNEL)
  ", __func__,
  		       (sizeof(*msg_ctx->msg) + data_size));
  		goto out_unlock;
  	}

  	msg_ctx->msg->index = msg_ctx->index;
  	msg_ctx->msg->data_len = data_size;
  	msg_ctx->type = msg_type;

  	memcpy(msg_ctx->msg->data, data, data_size);
  	msg_ctx->msg_size = (sizeof(*msg_ctx->msg) + data_size);

  	mutex_lock(&daemon->mux);
  	list_add_tail(&msg_ctx->daemon_out_list, &daemon->msg_ctx_out_queue);
  	daemon->num_queued_msg_ctx++;
  	wake_up_interruptible(&daemon->wait);
  	mutex_unlock(&daemon->mux);
  out_unlock:
  	mutex_unlock(&msg_ctx->mux);
  	return rc;
  }
  
  /**
   * ecryptfs_miscdev_read - format and send message from queue
   * @file: fs/ecryptfs/euid miscdevfs handle (ignored)
   * @buf: User buffer into which to copy the next message on the daemon queue
   * @count: Amount of space available in @buf
   * @ppos: Offset in file (ignored)
   *
   * Pulls the most recent message from the daemon queue, formats it for
   * being sent via a miscdevfs handle, and copies it into @buf
   *
   * Returns the number of bytes copied into the user buffer
   */

  static ssize_t

  ecryptfs_miscdev_read(struct file *file, char __user *buf, size_t count,
  		      loff_t *ppos)
  {
  	struct ecryptfs_daemon *daemon;
  	struct ecryptfs_msg_ctx *msg_ctx;
  	size_t packet_length_size;

  	char packet_length[3];
  	size_t i;
  	size_t total_length;

  	uid_t euid = current_euid();

  	int rc;
  
  	mutex_lock(&ecryptfs_daemon_hash_mux);
  	/* TODO: Just use file->private_data? */

  	rc = ecryptfs_find_daemon_by_euid(&daemon, euid, current_user_ns());

  	BUG_ON(rc || !daemon);
  	mutex_lock(&daemon->mux);
  	if (daemon->flags & ECRYPTFS_DAEMON_ZOMBIE) {
  		rc = 0;

  		mutex_unlock(&ecryptfs_daemon_hash_mux);

  		printk(KERN_WARNING "%s: Attempt to read from zombified "
  		       "daemon
  ", __func__);
  		goto out_unlock_daemon;
  	}
  	if (daemon->flags & ECRYPTFS_DAEMON_IN_READ) {
  		rc = 0;

  		mutex_unlock(&ecryptfs_daemon_hash_mux);

  		goto out_unlock_daemon;
  	}
  	/* This daemon will not go away so long as this flag is set */
  	daemon->flags |= ECRYPTFS_DAEMON_IN_READ;
  	mutex_unlock(&ecryptfs_daemon_hash_mux);
  check_list:
  	if (list_empty(&daemon->msg_ctx_out_queue)) {
  		mutex_unlock(&daemon->mux);
  		rc = wait_event_interruptible(
  			daemon->wait, !list_empty(&daemon->msg_ctx_out_queue));
  		mutex_lock(&daemon->mux);
  		if (rc < 0) {
  			rc = 0;
  			goto out_unlock_daemon;
  		}
  	}
  	if (daemon->flags & ECRYPTFS_DAEMON_ZOMBIE) {
  		rc = 0;
  		goto out_unlock_daemon;
  	}
  	if (list_empty(&daemon->msg_ctx_out_queue)) {
  		/* Something else jumped in since the
  		 * wait_event_interruptable() and removed the
  		 * message from the queue; try again */
  		goto check_list;
  	}

  	BUG_ON(euid != daemon->euid);

  	BUG_ON(current_user_ns() != daemon->user_ns);

  	BUG_ON(task_pid(current) != daemon->pid);

  	msg_ctx = list_first_entry(&daemon->msg_ctx_out_queue,
  				   struct ecryptfs_msg_ctx, daemon_out_list);
  	BUG_ON(!msg_ctx);
  	mutex_lock(&msg_ctx->mux);
  	if (msg_ctx->msg) {
  		rc = ecryptfs_write_packet_length(packet_length,
  						  msg_ctx->msg_size,
  						  &packet_length_size);
  		if (rc) {
  			rc = 0;
  			printk(KERN_WARNING "%s: Error writing packet length; "
  			       "rc = [%d]
  ", __func__, rc);
  			goto out_unlock_msg_ctx;
  		}
  	} else {
  		packet_length_size = 0;
  		msg_ctx->msg_size = 0;
  	}
  	/* miscdevfs packet format:
  	 *  Octet 0: Type
  	 *  Octets 1-4: network byte order msg_ctx->counter
  	 *  Octets 5-N0: Size of struct ecryptfs_message to follow
  	 *  Octets N0-N1: struct ecryptfs_message (including data)
  	 *
  	 *  Octets 5-N1 not written if the packet type does not
  	 *  include a message */
  	total_length = (1 + 4 + packet_length_size + msg_ctx->msg_size);
  	if (count < total_length) {
  		rc = 0;
  		printk(KERN_WARNING "%s: Only given user buffer of "

  		       "size [%zd], but we need [%zd] to read the "

  		       "pending message
  ", __func__, count, total_length);
  		goto out_unlock_msg_ctx;
  	}

  	rc = -EFAULT;
  	if (put_user(msg_ctx->type, buf))
  		goto out_unlock_msg_ctx;
  	if (put_user(cpu_to_be32(msg_ctx->counter), (__be32 __user *)(buf + 1)))
  		goto out_unlock_msg_ctx;
  	i = 5;

  	if (msg_ctx->msg) {

  		if (copy_to_user(&buf[i], packet_length, packet_length_size))
  			goto out_unlock_msg_ctx;

  		i += packet_length_size;

  		if (copy_to_user(&buf[i], msg_ctx->msg, msg_ctx->msg_size))

  			goto out_unlock_msg_ctx;

  		i += msg_ctx->msg_size;
  	}
  	rc = i;
  	list_del(&msg_ctx->daemon_out_list);
  	kfree(msg_ctx->msg);
  	msg_ctx->msg = NULL;
  	/* We do not expect a reply from the userspace daemon for any
  	 * message type other than ECRYPTFS_MSG_REQUEST */
  	if (msg_ctx->type != ECRYPTFS_MSG_REQUEST)
  		ecryptfs_msg_ctx_alloc_to_free(msg_ctx);
  out_unlock_msg_ctx:
  	mutex_unlock(&msg_ctx->mux);
  out_unlock_daemon:
  	daemon->flags &= ~ECRYPTFS_DAEMON_IN_READ;
  	mutex_unlock(&daemon->mux);
  	return rc;
  }
  
  /**

   * ecryptfs_miscdev_response - miscdevess response to message previously sent to daemon
   * @data: Bytes comprising struct ecryptfs_message
   * @data_size: sizeof(struct ecryptfs_message) + data len
   * @euid: Effective user id of miscdevess sending the miscdev response

   * @user_ns: The namespace in which @euid applies

   * @pid: Miscdevess id of miscdevess sending the miscdev response
   * @seq: Sequence number for miscdev response packet
   *
   * Returns zero on success; non-zero otherwise
   */
  static int ecryptfs_miscdev_response(char *data, size_t data_size,

  				     uid_t euid, struct user_namespace *user_ns,
  				     struct pid *pid, u32 seq)

  {
  	struct ecryptfs_message *msg = (struct ecryptfs_message *)data;
  	int rc;
  
  	if ((sizeof(*msg) + msg->data_len) != data_size) {
  		printk(KERN_WARNING "%s: (sizeof(*msg) + msg->data_len) = "

  		       "[%zd]; data_size = [%zd]. Invalid packet.
  ", __func__,

  		       (sizeof(*msg) + msg->data_len), data_size);
  		rc = -EINVAL;
  		goto out;
  	}

  	rc = ecryptfs_process_response(msg, euid, user_ns, pid, seq);

  	if (rc)
  		printk(KERN_ERR
  		       "Error processing response message; rc = [%d]
  ", rc);
  out:
  	return rc;
  }
  
  /**
   * ecryptfs_miscdev_write - handle write to daemon miscdev handle
   * @file: File for misc dev handle (ignored)
   * @buf: Buffer containing user data
   * @count: Amount of data in @buf
   * @ppos: Pointer to offset in file (ignored)
   *
   * miscdevfs packet format:
   *  Octet 0: Type
   *  Octets 1-4: network byte order msg_ctx->counter (0's for non-response)
   *  Octets 5-N0: Size of struct ecryptfs_message to follow
   *  Octets N0-N1: struct ecryptfs_message (including data)
   *
   * Returns the number of bytes read from @buf
   */
  static ssize_t
  ecryptfs_miscdev_write(struct file *file, const char __user *buf,
  		       size_t count, loff_t *ppos)
  {

  	__be32 counter_nbo;
  	u32 seq;

  	size_t packet_size, packet_size_length, i;
  	ssize_t sz = 0;
  	char *data;

  	uid_t euid = current_euid();

  	int rc;
  
  	if (count == 0)
  		goto out;

  
  	data = memdup_user(buf, count);
  	if (IS_ERR(data)) {
  		printk(KERN_ERR "%s: memdup_user returned error [%ld]
  ",
  		       __func__, PTR_ERR(data));

  		goto out;
  	}

  	sz = count;
  	i = 0;
  	switch (data[i++]) {
  	case ECRYPTFS_MSG_RESPONSE:
  		if (count < (1 + 4 + 1 + sizeof(struct ecryptfs_message))) {
  			printk(KERN_WARNING "%s: Minimum acceptable packet "

  			       "size is [%zd], but amount of data written is "
  			       "only [%zd]. Discarding response packet.
  ",

  			       __func__,
  			       (1 + 4 + 1 + sizeof(struct ecryptfs_message)),
  			       count);
  			goto out_free;
  		}

  		memcpy(&counter_nbo, &data[i], 4);

  		seq = be32_to_cpu(counter_nbo);
  		i += 4;
  		rc = ecryptfs_parse_packet_length(&data[i], &packet_size,
  						  &packet_size_length);
  		if (rc) {
  			printk(KERN_WARNING "%s: Error parsing packet length; "
  			       "rc = [%d]
  ", __func__, rc);
  			goto out_free;
  		}
  		i += packet_size_length;
  		if ((1 + 4 + packet_size_length + packet_size) != count) {

  			printk(KERN_WARNING "%s: (1 + packet_size_length([%zd])"
  			       " + packet_size([%zd]))([%zd]) != "
  			       "count([%zd]). Invalid packet format.
  ",

  			       __func__, packet_size_length, packet_size,
  			       (1 + packet_size_length + packet_size), count);
  			goto out_free;
  		}
  		rc = ecryptfs_miscdev_response(&data[i], packet_size,

  					       euid, current_user_ns(),

  					       task_pid(current), seq);

  		if (rc)
  			printk(KERN_WARNING "%s: Failed to deliver miscdev "
  			       "response to requesting operation; rc = [%d]
  ",
  			       __func__, rc);
  		break;
  	case ECRYPTFS_MSG_HELO:

  	case ECRYPTFS_MSG_QUIT:

  		break;
  	default:
  		ecryptfs_printk(KERN_WARNING, "Dropping miscdev "
  				"message of unrecognized type [%d]
  ",
  				data[0]);
  		break;
  	}
  out_free:
  	kfree(data);
  out:
  	return sz;
  }
  
  
  static const struct file_operations ecryptfs_miscdev_fops = {
  	.open    = ecryptfs_miscdev_open,
  	.poll    = ecryptfs_miscdev_poll,
  	.read    = ecryptfs_miscdev_read,
  	.write   = ecryptfs_miscdev_write,
  	.release = ecryptfs_miscdev_release,

  	.llseek  = noop_llseek,

  };
  
  static struct miscdevice ecryptfs_miscdev = {
  	.minor = MISC_DYNAMIC_MINOR,
  	.name  = "ecryptfs",
  	.fops  = &ecryptfs_miscdev_fops
  };
  
  /**
   * ecryptfs_init_ecryptfs_miscdev
   *
   * Messages sent to the userspace daemon from the kernel are placed on
   * a queue associated with the daemon. The next read against the
   * miscdev handle by that daemon will return the oldest message placed
   * on the message queue for the daemon.
   *
   * Returns zero on success; non-zero otherwise
   */

  int __init ecryptfs_init_ecryptfs_miscdev(void)

  {
  	int rc;
  
  	atomic_set(&ecryptfs_num_miscdev_opens, 0);

  	rc = misc_register(&ecryptfs_miscdev);
  	if (rc)
  		printk(KERN_ERR "%s: Failed to register miscellaneous device "
  		       "for communications with userspace daemons; rc = [%d]
  ",
  		       __func__, rc);

  	return rc;
  }
  
  /**
   * ecryptfs_destroy_ecryptfs_miscdev
   *
   * All of the daemons must be exorcised prior to calling this
   * function.
   */
  void ecryptfs_destroy_ecryptfs_miscdev(void)
  {
  	BUG_ON(atomic_read(&ecryptfs_num_miscdev_opens) != 0);
  	misc_deregister(&ecryptfs_miscdev);
  }