wepdecap.cc

COPE the first practical network coding scheme which is developped on click

/*
 * wepdecap.{cc,hh} -- decapsultates 802.11 packets
 * John Bicket
 *
 * Copyright (c) 2004 Massachusetts Institute of Technology
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, subject to the conditions
 * listed in the Click LICENSE file. These conditions include: you must
 * preserve this copyright notice, and you cannot mention the copyright
 * holders in advertising related to the Software without their permission.
 * The Software is provided WITHOUT ANY WARRANTY, EXPRESS OR IMPLIED. This
 * notice is a summary of the Click LICENSE file; the license in that file is
 * legally binding.
 */

/*-
 * Copyright (c) 2002-2005 Sam Leffler, Errno Consulting
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * Alternatively, this software may be distributed under the terms of the
 * GNU General Public License ("GPL") version 2 as published by the Free
 * Software Foundation.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include <click/config.h>
#include "wepdecap.hh"
#include <click/etheraddress.hh>
#include <click/confparse.hh>
#include <click/error.hh>
#include <click/glue.hh>
#include <clicknet/wifi.h>
#include <clicknet/llc.h>
#include <click/crc32.h>
CLICK_DECLS

WepDecap::WepDecap()
  : Element(1, 1)
{
}

WepDecap::~WepDecap()
{
}

int
WepDecap::configure(Vector<String> &conf, ErrorHandler *errh)
{

  _debug = false;
  _strict = false;
  _keyid = 0;
  if (cp_va_parse(conf, this, errh,
		  /* not required */
		  cpOptional,
		  cpString, "key", &_key,
		  cpUnsigned, "keyid", &_keyid,
		  cpKeywords,
		  "KEYID", cpUnsigned, "keyid", &_keyid,
		  "DEBUG", cpBool, "Debug", &_debug,
		  "STRICT", cpBool, "strict header check", &_strict,
		  cpEnd) < 0)
    return -1;
  memset(&_rc4, 0,sizeof(_rc4));
  return 0;
}




Packet *
WepDecap::simple_action(Packet *p_in)
{
  WritablePacket *p = p_in->uniqueify();
  struct click_wifi *w = (struct click_wifi *) p->data();

  if (!(w->i_fc[1] & WIFI_FC1_WEP)) {
    /* not a wep packet */
    return p;
  }

  /* decrypt the packet first */

  u_int8_t rc4key[WIFI_WEP_IVLEN + WIFI_KEYBUF_SIZE];
  u_int8_t crcbuf[WIFI_WEP_CRCLEN];
  u_int8_t *icv;
  u_int8_t *icp = p->data() + sizeof(click_wifi);
  u_int32_t crc;
  u_int32_t iv;
  u_int8_t keyid = icp[WIFI_WEP_IVLEN];

  if (keyid != _keyid) {
    return p;
  }
  iv = icp[0] | (icp[1] << 8) | (icp[2] << 16) | (icp[3] << 24);

  memcpy(rc4key, icp, WIFI_WEP_IVLEN);
  memcpy(rc4key + WIFI_WEP_IVLEN, _key.cc(), _key.length());
  rc4_init(&_rc4, rc4key, WIFI_WEP_IVLEN + _key.length());

  u_int8_t *payload = p->data() + sizeof(click_wifi) + WIFI_WEP_HEADERSIZE;
  int payload_len = p->length() - (sizeof(click_wifi) + WIFI_WEP_HEADERSIZE + WIFI_WEP_CRCLEN);
  /* decrypt data */
  rc4_crypt_skip(&_rc4, payload, payload, payload_len, 0);

  /* calculate CRC over unencrypted data */
  crc = rfc_2083_crc_update(~0, payload, payload_len);

  /* decrypt ICV and compare to CRC */
  icv = payload + payload_len;
  rc4_crypt_skip(&_rc4, icv, crcbuf, WIFI_WEP_CRCLEN, 0);
  
  if (crc != ~le32_to_cpu(*(u_int32_t *)crcbuf)) {
    click_chatter("crc failed keyid %d iv %d %x wanted %x %x\n",
		  keyid,
		  iv,
		  crc, 
		  ~le32_to_cpu(*(u_int32_t *)crcbuf),
		  *(u_int32_t *)crcbuf);
    /* packet failed decrypt */
    return p;
  }
  /* strip the wep header off */
  memmove((void *)(p->data() + WIFI_WEP_HEADERSIZE), p->data(), sizeof(click_wifi));
  p->pull(WIFI_WEP_HEADERSIZE);
  /* strip the wep crc off the tail of the packet */
  p->take(WIFI_WEP_CRCLEN);

  w = (struct click_wifi *) p->data();
  w->i_fc[1] &= ~WIFI_FC1_WEP;
  return p;
}


enum {H_DEBUG, H_KEY, H_KEYID};

static String 
read_param(Element *e, void *thunk)
{
  WepDecap *td = (WepDecap *)e;
    switch ((uintptr_t) thunk) {
      case H_DEBUG: return String(td->_debug) + "\n";
    case H_KEY: return td->_key.quoted_hex() + "\n";
    case H_KEYID: return String(td->_keyid) + "\n";
    default:
      return String();
    }
}
static int 
write_param(const String &in_s, Element *e, void *vparam,
		      ErrorHandler *errh)
{
  WepDecap *f = (WepDecap *)e;
  String s = cp_uncomment(in_s);
  switch((int)vparam) {
  case H_DEBUG: {    //debug
    bool debug;
    if (!cp_bool(s, &debug)) 
      return errh->error("debug parameter must be boolean");
    f->_debug = debug;
    break;
  }
  case H_KEYID: {
    unsigned m;
    if (!cp_unsigned(s, &m)) 
      return errh->error("keyid parameter must be unsigned");
    f->_keyid = m;
    break;
  }
  case H_KEY: {
    String m;
    if (!cp_string(s, &m)) 
      return errh->error("key parameter must be unsigned");
    f->_key = m;
    break;
  }
  }
  return 0;
}
 
void
WepDecap::add_handlers()
{
  add_default_handlers(true);

  add_read_handler("debug", read_param, (void *) H_DEBUG);
  add_read_handler("key", read_param, (void *) H_KEY);
  add_read_handler("keyid", read_param, (void *) H_KEYID);

  add_write_handler("debug", write_param, (void *) H_DEBUG);
  add_write_handler("key", write_param, (void *) H_KEY);
  add_write_handler("keyid", write_param, (void *) H_KEYID);
}
CLICK_ENDDECLS
ELEMENT_REQUIRES(rc4)
EXPORT_ELEMENT(WepDecap)