// SPDX-License-Identifier: GPL-2.0-only
/**
 * eCryptfs: Linux filesystem encryption layer
 *
 * Copyright (C) 2008 International Business Machines Corp.
 *   Author(s): Michael A. Halcrow <mhalcrow@us.ibm.com>
 */

#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
 * @pt: dev poll table (ignored)
 *
 * Returns the poll mask
 */
static __poll_t
ecryptfs_miscdev_poll(struct file *file, poll_table *pt)
{
        struct ecryptfs_daemon *daemon = file->private_data;
        __poll_t mask = 0;

        mutex_lock(&daemon->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 |= EPOLLIN | EPOLLRDNORM;
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
 *
 * 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 = ecryptfs_find_daemon_by_euid(&daemon);
        if (!rc) {
                rc = -EINVAL;
                goto out_unlock_daemon_list;
        }
        rc = ecryptfs_spawn_daemon(&daemon, file);
        if (rc) {
                printk(KERN_ERR "%s: Error attempting to spawn daemon; "
                       "rc = [%d]\n", __func__, rc);
                goto out_unlock_daemon_list;
        }
        mutex_lock(&daemon->mux);
        if (daemon->flags & ECRYPTFS_DAEMON_MISCDEV_OPEN) {
                rc = -EBUSY;
                goto out_unlock_daemon;
        }
        daemon->flags |= ECRYPTFS_DAEMON_MISCDEV_OPEN;
        file->private_data = daemon;
        atomic_inc(&ecryptfs_num_miscdev_opens);
out_unlock_daemon:
        mutex_unlock(&daemon->mux);
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
 *
 * 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 = file->private_data;
        int rc;

        mutex_lock(&daemon->mux);
        BUG_ON(!(daemon->flags & ECRYPTFS_DAEMON_MISCDEV_OPEN));
        daemon->flags &= ~ECRYPTFS_DAEMON_MISCDEV_OPEN;
        atomic_dec(&ecryptfs_num_miscdev_opens);
        mutex_unlock(&daemon->mux);

        mutex_lock(&ecryptfs_daemon_hash_mux);
        rc = ecryptfs_exorcise_daemon(daemon);
        mutex_unlock(&ecryptfs_daemon_hash_mux);
        if (rc) {
                printk(KERN_CRIT "%s: Fatal error whilst attempting to "
                       "shut down daemon; rc = [%d]. Please report this "
                       "bug.\n", __func__, rc);
                BUG();
        }
        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)
{
        struct ecryptfs_message *msg;

        msg = kmalloc((sizeof(*msg) + data_size), GFP_KERNEL);
        if (!msg)
                return -ENOMEM;

        mutex_lock(&msg_ctx->mux);
        msg_ctx->msg = msg;
        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);
        list_add_tail(&msg_ctx->daemon_out_list, &daemon->msg_ctx_out_queue);
        mutex_unlock(&msg_ctx->mux);

        mutex_lock(&daemon->mux);
        daemon->num_queued_msg_ctx++;
        wake_up_interruptible(&daemon->wait);
        mutex_unlock(&daemon->mux);

        return 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
 */
#define PKT_TYPE_SIZE           1
#define PKT_CTR_SIZE            4
#define MIN_NON_MSG_PKT_SIZE    (PKT_TYPE_SIZE + PKT_CTR_SIZE)
#define MIN_MSG_PKT_SIZE        (PKT_TYPE_SIZE + PKT_CTR_SIZE \
                                 + ECRYPTFS_MIN_PKT_LEN_SIZE)
/* 4 + ECRYPTFS_MAX_ENCRYPTED_KEY_BYTES comes from tag 65 packet format */
#define MAX_MSG_PKT_SIZE        (PKT_TYPE_SIZE + PKT_CTR_SIZE \
                                 + ECRYPTFS_MAX_PKT_LEN_SIZE \
                                 + sizeof(struct ecryptfs_message) \
                                 + 4 + ECRYPTFS_MAX_ENCRYPTED_KEY_BYTES)
#define PKT_TYPE_OFFSET         0
#define PKT_CTR_OFFSET          PKT_TYPE_SIZE
#define PKT_LEN_OFFSET          (PKT_TYPE_SIZE + PKT_CTR_SIZE)

/**
 * ecryptfs_miscdev_read - format and send message from queue
 * @file: miscdevfs handle
 * @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 = file->private_data;
        struct ecryptfs_msg_ctx *msg_ctx;
        size_t packet_length_size;
        char packet_length[ECRYPTFS_MAX_PKT_LEN_SIZE];
        size_t i;
        size_t total_length;
        int rc;

        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;
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;
        }
        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;
        }
        total_length = (PKT_TYPE_SIZE + PKT_CTR_SIZE + 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;
        }
        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[PKT_CTR_OFFSET])))
                goto out_unlock_msg_ctx;
        i = PKT_TYPE_SIZE + PKT_CTR_SIZE;
        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
 * @seq: Sequence number for miscdev response packet
 *
 * Returns zero on success; non-zero otherwise
 */
static int ecryptfs_miscdev_response(struct ecryptfs_daemon *daemon, char *data,
                                     size_t data_size, 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(daemon, msg, 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
 * @buf: Buffer containing user data
 * @count: Amount of data in @buf
 * @ppos: Pointer to offset in file (ignored)
 *
 * 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;
        char *data;
        unsigned char packet_size_peek[ECRYPTFS_MAX_PKT_LEN_SIZE];
        ssize_t rc;

        if (count == 0) {
                return 0;
        } else if (count == MIN_NON_MSG_PKT_SIZE) {
                /* Likely a harmless MSG_HELO or MSG_QUIT - no packet length */
                goto memdup;
        } else if (count < MIN_MSG_PKT_SIZE || count > MAX_MSG_PKT_SIZE) {
                printk(KERN_WARNING "%s: Acceptable packet size range is "
                       "[%d-%zu], but amount of data written is [%zu].\n",
                       __func__, MIN_MSG_PKT_SIZE, MAX_MSG_PKT_SIZE, count);
                return -EINVAL;
        }

        if (copy_from_user(packet_size_peek, &buf[PKT_LEN_OFFSET],
                           sizeof(packet_size_peek))) {
                printk(KERN_WARNING "%s: Error while inspecting packet size\n",
                       __func__);
                return -EFAULT;
        }

        rc = ecryptfs_parse_packet_length(packet_size_peek, &packet_size,
                                          &packet_size_length);
        if (rc) {
                printk(KERN_WARNING "%s: Error parsing packet length; "
                       "rc = [%zd]\n", __func__, rc);
                return rc;
        }

        if ((PKT_TYPE_SIZE + PKT_CTR_SIZE + packet_size_length + packet_size)
            != count) {
                printk(KERN_WARNING "%s: Invalid packet size [%zu]\n", __func__,
                       packet_size);
                return -EINVAL;
        }

memdup:
        data = memdup_user(buf, count);
        if (IS_ERR(data)) {
                printk(KERN_ERR "%s: memdup_user returned error [%ld]\n",
                       __func__, PTR_ERR(data));
                return PTR_ERR(data);
        }
        switch (data[PKT_TYPE_OFFSET]) {
        case ECRYPTFS_MSG_RESPONSE:
                if (count < (MIN_MSG_PKT_SIZE
                             + 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__,
                               (MIN_MSG_PKT_SIZE
                                + sizeof(struct ecryptfs_message)), count);
                        rc = -EINVAL;
                        goto out_free;
                }
                memcpy(&counter_nbo, &data[PKT_CTR_OFFSET], PKT_CTR_SIZE);
                seq = be32_to_cpu(counter_nbo);
                rc = ecryptfs_miscdev_response(file->private_data,
                                &data[PKT_LEN_OFFSET + packet_size_length],
                                packet_size, seq);
                if (rc) {
                        printk(KERN_WARNING "%s: Failed to deliver miscdev "
                               "response to requesting operation; rc = [%zd]\n",
                               __func__, rc);
                        goto out_free;
                }
                break;
        case ECRYPTFS_MSG_HELO:
        case ECRYPTFS_MSG_QUIT:
                break;
        default:
                ecryptfs_printk(KERN_WARNING, "Dropping miscdev "
                                "message of unrecognized type [%d]\n",
                                data[0]);
                rc = -EINVAL;
                goto out_free;
        }
        rc = count;
out_free:
        kfree(data);
        return rc;
}


static const struct file_operations ecryptfs_miscdev_fops = {
        .owner   = THIS_MODULE,
        .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]\n",
                       __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);
}