/*
 * eset_wap (ESET Web Access Protection module)
 * Copyright (C) 1992-2023 ESET, spol. s r.o.
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * 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, see <https://www.gnu.org/licenses/>.
 *
 * In case of any questions, you can contact us at ESET, spol. s r.o., Einsteinova 24, 851 01 Bratislava, Slovakia.
 */

#include "ewap_dev.h"
#include "eset_wap.h"

#include "ewap_connect_data.h"
#include "ewap_helpers.h"

#include <linux/device.h>
#include <linux/export.h>
#include <linux/fs.h>
#include <linux/uaccess.h>
#include <linux/version.h>

static struct class *ewap_device_class;
static struct device *ewap_device;
static dev_t ewap_dev;

static long ewap_dev_ioctl(struct file *file, unsigned int cmd,
                           unsigned long arg);

static struct file_operations ewap_ioctl_fops = {
    .owner = THIS_MODULE,
    .unlocked_ioctl = ewap_dev_ioctl,
};

#if LINUX_VERSION_CODE < KERNEL_VERSION(5, 0, 0)

#if defined(RHEL_RELEASE_CODE) && defined(RHEL_RELEASE_VERSION)

#if (RHEL_RELEASE_CODE >= RHEL_RELEASE_VERSION(8, 1))
#define ewap_access_ok(addr, size) access_ok(addr, size)
#else
#define ewap_access_ok(addr, size) access_ok(VERIFY_WRITE, addr, size)
#endif

#else
#define ewap_access_ok(addr, size) access_ok(VERIFY_WRITE, addr, size)
#endif

#else
#define ewap_access_ok(addr, size) access_ok(addr, size)
#endif

#if LINUX_VERSION_CODE < KERNEL_VERSION(6, 4, 0)

#if defined(RHEL_RELEASE_CODE) && defined(RHEL_RELEASE_VERSION)

#if (RHEL_RELEASE_CODE >= RHEL_RELEASE_VERSION(9, 4))
#define ewap_class_create(name) class_create(name)
#else
#define ewap_class_create(name) class_create(THIS_MODULE, name)
#endif

#else
#define ewap_class_create(name) class_create(THIS_MODULE, name)
#endif

#else
#define ewap_class_create(name) class_create(name)
#endif

static long ewap_dev_handle_get_connection_info_query(
    struct eset_wap_get_connection_info __user *arg) {
  struct eset_wap_get_connection_info query;
  struct ewap_connect_data data;

  unsigned long n;
  long err = 0;
  bool ok;

  n = copy_from_user(&query, arg, sizeof(struct eset_wap_get_connection_info));
  if (unlikely(n != 0)) {
    ewap_pr_log(EWAP_LOG_ERRORS,
                "EWAP_GET_CONNECTION_INFO_QUERY failed: copy_from_user of "
                "query failed");
    return -EFAULT;
  }

  if (unlikely(
          query.result.path.buffer == NULL ||
          !ewap_access_ok(query.result.path.buffer, query.result.path.size))) {
    ewap_pr_log(
        EWAP_LOG_ERRORS,
        "EWAP_GET_CONNECTION_INFO_QUERY failed: invalid pointer for path");
    return -EFAULT;
  }

  switch (query.type) {
    case EWAP_ADDRESS_TYPE_V4:
      ok = ewap_connect_data_get_v4_connection(&query.address.v4, &data);
      break;
    case EWAP_ADDRESS_TYPE_V6:
      ok = ewap_connect_data_get_v6_connection(&query.address.v6, &data);
      break;
    default:
      ewap_pr_log(
          EWAP_LOG_ERRORS,
          "EWAP_GET_CONNECTION_INFO_QUERY failed: unknown address type");
      return -EFAULT;
  }

  if (!ok) {
    ewap_pr_log(EWAP_LOG_IOCTL,
                "EWAP_GET_CONNECTION_INFO_QUERY: process not found");
    return -ENODATA;
  }

  query.result.pid = (int32_t)data.pid;
  query.result.uid = (uint32_t)data.uid;

  ewap_pr_log(EWAP_LOG_IOCTL,
              "EWAP_GET_CONNECTION_INFO_QUERY: process found (pid: %d, uid: "
              "%u, path: %s)",
              query.result.pid, query.result.uid,
              data.path ? data.path->ptr : "-");

  if (data.path) {
    if (data.path->size > query.result.path.size) {
      ewap_pr_log(EWAP_LOG_IOCTL,
                  "EWAP_GET_CONNECTION_INFO_QUERY: provided buffer for path "
                  "was too small");
      err = -ENOBUFS;
      goto end;
    }

    n = copy_to_user(query.result.path.buffer, data.path->ptr, data.path->size);
    if (unlikely(n != 0)) {
      ewap_pr_log(
          EWAP_LOG_ERRORS,
          "EWAP_GET_CONNECTION_INFO_QUERY failed: copy_to_user of path failed");
      err = -EFAULT;
      goto end;
    }
  }

  n = copy_to_user(arg, &query, sizeof(struct eset_wap_get_connection_info));
  if (unlikely(n != 0)) {
    ewap_pr_log(
        EWAP_LOG_ERRORS,
        "EWAP_GET_CONNECTION_INFO_QUERY failed: copy_to_user of query failed");
    err = -EFAULT;
    goto end;
  }

end:
  ewap_path_unref(data.path);
  return err;
}

static long ewap_dev_ioctl(struct file *file, unsigned int cmd,
                           unsigned long arg) {
  switch (cmd) {
    case EWAP_GET_CONNECTION_INFO_QUERY:
      return ewap_dev_handle_get_connection_info_query(
          (struct eset_wap_get_connection_info __user *)arg);

    default:
      ewap_pr_log(EWAP_LOG_ERRORS, "unknown ioctl call");
      break;
  }

  return -EINVAL;
}

int ewap_dev_init(void) {
  int major;

  major = register_chrdev(0, EWAP_DEVICE_NAME, &ewap_ioctl_fops);
  if (major < 0) {
    return major;
  }

  ewap_dev = MKDEV(major, 0);

  ewap_device_class = ewap_class_create(EWAP_DEVICE_NAME);
  if (IS_ERR(ewap_device_class)) {
    unregister_chrdev(major, EWAP_DEVICE_NAME);
    return PTR_ERR(ewap_device_class);
  }

  ewap_device =
      device_create(ewap_device_class, NULL, ewap_dev, NULL, EWAP_DEVICE_NAME);
  if (IS_ERR(ewap_device)) {
    class_destroy(ewap_device_class);
    unregister_chrdev(major, EWAP_DEVICE_NAME);
    return PTR_ERR(ewap_device);
  }

  return 0;
}

void ewap_dev_deinit(void) {
  device_destroy(ewap_device_class, ewap_dev);
  class_destroy(ewap_device_class);
  unregister_chrdev(MAJOR(ewap_dev), EWAP_DEVICE_NAME);
}