eCryptfs: introduce device handle for userspace daemon communications

/**

 * 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/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;

	int rc;

	mutex_lock(&ecryptfs_daemon_hash_mux);

	/* TODO: Just use file->private_data? */

	rc = ecryptfs_find_daemon_by_euid(&daemon, current->euid);

	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\n", __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;

	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]\n", __func__, rc);

		goto out_unlock_daemon_list;

	}

	rc = ecryptfs_find_daemon_by_euid(&daemon, current->euid);

	if (rc || !daemon) {

		rc = ecryptfs_spawn_daemon(&daemon, current->euid,

					   current->pid);

		if (rc) {

			printk(KERN_ERR "%s: Error attempting to spawn daemon; "

			       "rc = [%d]\n", __func__, rc);

			goto out_module_put_unlock_daemon_list;

		}

	}

	mutex_lock(&daemon->mux);

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

		rc = -EINVAL;

		printk(KERN_ERR "%s: pid [%d] has registered with euid [%d], "

		       "but pid [%d] has attempted to open the handle "

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

		       current->pid);

		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 [%d] already has this "

		       "handle open\n", __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;

	int rc;

	mutex_lock(&ecryptfs_daemon_hash_mux);

	rc = ecryptfs_find_daemon_by_euid(&daemon, current->euid);

	BUG_ON(rc || !daemon);

	mutex_lock(&daemon->mux);

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

	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.\n", __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);

	if (data) {

		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(%d, GFP_KERNEL)\n", __func__,

			       (sizeof(*msg_ctx->msg) + data_size));

			goto out_unlock;

		}

	} else

		msg_ctx->msg = NULL;

	msg_ctx->msg->index = msg_ctx->index;

	msg_ctx->msg->data_len = data_size;

	msg_ctx->type = msg_type;

	if (data) {

		memcpy(msg_ctx->msg->data, data, data_size);

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

	} else

		msg_ctx->msg_size = 0;

	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 int

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;

	u32 counter_nbo;

	char packet_length[3];

	size_t i;

	size_t total_length;

	int rc;

	mutex_lock(&ecryptfs_daemon_hash_mux);

	/* TODO: Just use file->private_data? */

	rc = ecryptfs_find_daemon_by_euid(&daemon, current->euid);

	BUG_ON(rc || !daemon);

	mutex_lock(&daemon->mux);

	if (daemon->flags & ECRYPTFS_DAEMON_ZOMBIE) {

		rc = 0;

		printk(KERN_WARNING "%s: Attempt to read from zombified "

		       "daemon\n", __func__);

		goto out_unlock_daemon;

	}

	if (daemon->flags & ECRYPTFS_DAEMON_IN_READ) {

		rc = 0;

		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(current->euid != daemon->euid);

	BUG_ON(current->pid != 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]\n", __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\n", __func__, count, total_length);

		goto out_unlock_msg_ctx;

	}

	i = 0;

	buf[i++] = msg_ctx->type;

	counter_nbo = cpu_to_be32(msg_ctx->counter);

	memcpy(&buf[i], (char *)&counter_nbo, 4);

	i += 4;

	if (msg_ctx->msg) {

		memcpy(&buf[i], packet_length, packet_length_size);

		i += packet_length_size;

		rc = copy_to_user(&buf[i], msg_ctx->msg, msg_ctx->msg_size);

		if (rc) {

			printk(KERN_ERR "%s: copy_to_user returned error "

			       "[%d]\n", __func__, rc);

			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_helo

 * @euid: effective user id of miscdevess sending helo packet

 * @pid: miscdevess id of miscdevess sending helo packet

 *

 * Returns zero on success; non-zero otherwise

 */

static int ecryptfs_miscdev_helo(uid_t uid, pid_t pid)

{

	int rc;

	rc = ecryptfs_process_helo(ECRYPTFS_TRANSPORT_MISCDEV, uid, pid);

	if (rc)

		printk(KERN_WARNING "Error processing HELO; rc = [%d]\n", rc);

	return rc;

}

/**

 * ecryptfs_miscdev_quit

 * @euid: effective user id of miscdevess sending quit packet

 * @pid: miscdevess id of miscdevess sending quit packet

 *

 * Returns zero on success; non-zero otherwise

 */

static int ecryptfs_miscdev_quit(uid_t euid, pid_t pid)

{

	int rc;

	rc = ecryptfs_process_quit(euid, pid);

	if (rc)

		printk(KERN_WARNING

		       "Error processing QUIT message; rc = [%d]\n", rc);

	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

 * @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, pid_t 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.\n", __func__,

		       (sizeof(*msg) + msg->data_len), data_size);

		rc = -EINVAL;

		goto out;

	}

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

	if (rc)

		printk(KERN_ERR

		       "Error processing response message; rc = [%d]\n", 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)

{

	u32 counter_nbo, seq;

	size_t packet_size, packet_size_length, i;

	ssize_t sz = 0;

	char *data;

	int rc;

	if (count == 0)

		goto out;

	data = kmalloc(count, GFP_KERNEL);

	if (!data) {

		printk(KERN_ERR "%s: Out of memory whilst attempting to "

		       "kmalloc([%Zd], GFP_KERNEL)\n", __func__, count);

		goto out;

	}

	rc = copy_from_user(data, buf, count);

	if (rc) {

		printk(KERN_ERR "%s: copy_from_user returned error [%d]\n",

		       __func__, rc);

		goto out_free;

	}

	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.\n",

			       __func__,

			       (1 + 4 + 1 + sizeof(struct ecryptfs_message)),

			       count);

			goto out_free;

		}

		memcpy((char *)&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]\n", __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.\n",

			       __func__, packet_size_length, packet_size,

			       (1 + packet_size_length + packet_size), count);

			goto out_free;

		}

		rc = ecryptfs_miscdev_response(&data[i], packet_size,

					       current->euid,

					       current->pid, seq);

		if (rc)

			printk(KERN_WARNING "%s: Failed to deliver miscdev "

			       "response to requesting operation; rc = [%d]\n",

			       __func__, rc);

		break;

	case ECRYPTFS_MSG_HELO:

		rc = ecryptfs_miscdev_helo(current->euid, current->pid);

		if (rc) {

			printk(KERN_ERR "%s: Error attempting to process "

			       "helo from pid [%d]; rc = [%d]\n", __func__,

			       current->pid, rc);

			goto out_free;

		}

		break;

	case ECRYPTFS_MSG_QUIT:

		rc = ecryptfs_miscdev_quit(current->euid, current->pid);

		if (rc) {

			printk(KERN_ERR "%s: Error attempting to process "

			       "quit from pid [%d]; rc = [%d]\n", __func__,

			       current->pid, rc);

			goto out_free;

		}

		break;

	default:

		ecryptfs_printk(KERN_WARNING, "Dropping miscdev "

				"message of unrecognized type [%d]\n",

				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,

};

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 ecryptfs_init_ecryptfs_miscdev(void)

{

	int rc;

	atomic_set(&ecryptfs_num_miscdev_opens, 0);

	mutex_lock(&ecryptfs_daemon_hash_mux);

	rc = misc_register(&ecryptfs_miscdev);

	if (rc)

		printk(KERN_ERR "%s: Failed to register miscellaneous device "

		       "for communications with userspace daemons; rc = [%d]\n",

		       __func__, rc);

	mutex_unlock(&ecryptfs_daemon_hash_mux);

	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);

}