/*
 * Copyright (C) 2006 toast
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
 * 02111-1307, USA.
 *
 *
 * This file involves heavy borrowing from ethereal's WEP code
 *
 */
#include <string.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdint.h>
#include <stdio.h>

#include "wep.h"

#define SSWAP(a,b) {uint8_t tmp = s[a]; s[a] = s[b]; s[b] = tmp;}

/* table for crc32 */
const uint32_t crc32_ccitt_table[256] = {
  0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
  0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
  0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
  0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
  0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
  0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
  0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
  0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
  0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
  0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
  0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
  0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
  0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
  0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
  0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
  0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
  0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
  0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
  0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
  0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
  0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
  0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
  0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
  0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
  0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
  0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
  0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
  0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
  0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
  0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
  0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
  0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
  0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
  0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
  0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
  0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
  0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
  0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
  0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
  0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
  0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
  0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
  0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
  0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
  0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
  0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
  0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
  0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
  0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
  0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
  0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
  0x2d02ef8d
};

/**
 * Initializes the s-boxes for RC4 encryption/deceryption
 */
void rc4_init(uint8_t *s, const uint8_t *key, uint32_t keylen){
  uint32_t i,j;

  /* set up the RC4 state */
  for (i = 0; i < 256; i++)
    s[i] = i;
  j = 0;
  for (i = 0; i < 256; i++) {
    j = (j + s[i] + key[i % keylen]) & 0xff;
    SSWAP(i,j);
  }
}

/**
 * Function to perform wep encryption or decryption.  Arguments:
 * src - source buffer
 * dest - destination buffer
 * len - length of the source buffer
 * wepkey - the key to use for en/decryption
 * keylen - the length of the key in bytes
 * encrypt - 1 to perform encryption, 0 to perform decryption
 **/
int32_t do_wep(const uint8_t *src, uint8_t *dest, uint32_t len,
    const uint8_t *wepkey, uint32_t keylen, uint32_t encrypt){
  uint8_t s[256], c_crc[4], key[128];
  uint32_t i,j,k,crc;
  const uint8_t *sptr;
  uint8_t *dptr;

  // copy the IV to the beginning of the key
  if(encrypt){
    //TODO: make this random perhaps..
    key[0] = 0x70;
    key[1] = 0x77;
    key[2] = 0x6e;
  }else {
    key[0] = src[0];
    key[1] = src[1];
    key[2] = src[2];
  }
  //printf("IV: 0x%02x%02x%02x len: %u\n", buf[0], buf[1], buf[2], len);

  memcpy(key+3, wepkey, keylen);

  rc4_init(s, key, keylen + 3);

  crc = ~0;
  i = j = 0;
  
  if(encrypt){
    sptr = src;
    memcpy(dest, key, 3); // copy the IV to the start of the destination
    dest[3] = 0;  // set the key ID to 0.. TODO: do we need to remember the ID?
    dptr = dest + 4; // start after the IV and key ID
  } else {
    sptr = src + 4; // start after the IV and key ID
    dptr = dest;
    len -= 8; // remove 8 bytes for IV (3) ID (1) and ICV (4)
  }
  
  for(k = 0; k < len; k++){
    i = (i + 1) & 0xff;
    j = (j + s[i]) & 0xff;
    SSWAP(i,j);

    if(encrypt){
      *dptr++ = *sptr ^ s[(s[i] + s[j]) & 0xff];
      crc = crc32_ccitt_table[(crc ^ *sptr++) & 0xff] ^ (crc >> 8);
    } else {
      *dptr = *sptr++ ^ s[(s[i] + s[j]) & 0xff];
      //printf("%02x ", *dptr);
      crc = crc32_ccitt_table[(crc ^ *dptr++) & 0xff] ^ (crc >> 8);
    }
  }
  crc = ~crc;
  
  c_crc[0] = crc;
  c_crc[1] = crc >> 8;
  c_crc[2] = crc >> 16;
  c_crc[3] = crc >> 24;

  if(encrypt){
    // write the CRC to the end of the encrypted data
    for (k = 0; k < 4; k++) {
      i = (i + 1) & 0xff;
      j = (j+s[i]) & 0xff;
      SSWAP(i,j); 

      *dptr++ = c_crc[k] ^ s[(s[i] + s[j]) & 0xff];
    }
  } else {
    /* now let's check the crc */
    for (k = 0; k < 4; k++) {
      i = (i + 1) & 0xff;
      j = (j+s[i]) & 0xff;
      SSWAP(i,j); 

      if ((*sptr++ ^ s[(s[i] + s[j]) & 0xff]) != c_crc[k]){
	/* ICV mismatch */
	return -1;
      }
    }
  }
  
  return dptr - dest;
}

int32_t wep_decrypt(const uint8_t *src, uint8_t *dest, uint32_t len, 
    		     const uint8_t *wepkey, uint32_t keylen){
  return do_wep(src, dest, len, wepkey, keylen, 0);
}

int32_t wep_encrypt(const uint8_t *src, uint8_t *dest, uint32_t len, 
    		     const uint8_t *wepkey, uint32_t keylen){
  return do_wep(src, dest, len, wepkey, keylen, 1);
}

int wep_main(){
  uint32_t i;
  uint8_t key[] = { 0x11, 0x11, 0x11, 0x11, 0x11 };
  uint8_t crypto[] = { 0x14, 0x04, 0x00, 0x00, 0x80, 0xd9, 0x3b, 0x35, 0xc0, 0x34, 0x2a, 0x2e, 0x54, 0x51, 0xb1, 0x8c, 0xa0, 0x90, 0x66, 0xa2, 0x57, 0x90, 0x64, 0x36, 0x79, 0x13, 0xf3, 0xd1, 0x99, 0x06, 0x8f, 0x76, 0x77, 0x70, 0x06, 0xcf, 0x20, 0x9e, 0x3d, 0x52, 0xf8, 0x79, 0xb6, 0x2f, 0x10, 0x63, 0xd2, 0x28, 0xca, 0x4f, 0x9f, 0xb1, 0x69, 0x0e, 0xa6, 0x3d, 0x3d, 0x89, 0x7f, 0x9c, 0xe1, 0xae, 0x83, 0x49, 0x2c, 0x95, 0xbf, 0xdf, 0x35, 0x5e, 0x11, 0xf1, 0xf6, 0x18, 0x63, 0x8a, 0x14, 0x30, 0x47, 0xd4 };
  char *text = "The quick brown goatse jumped over the lazy tubgirl.";
  uint8_t cleartext[256];
  int32_t len = sizeof(crypto) - 4;
  uint8_t tmpbuf[1024];
  
  // test a known good WEP payload
  len = wep_decrypt(crypto, cleartext, len, key, sizeof(key));
  if(len <= 0){
    printf("failed to decrypt!\n");
    return 1;
  } else {
    for(i = 0; i < len; i++){
      printf("%02x ", cleartext[i]);
    }
    printf("\n\n");
  }

  // print out encryption of a simple text
  len = wep_encrypt((uint8_t*)"test", tmpbuf, 4, key, sizeof(key));
  if(len <= 0){
    printf("failed to encrypt!\n");
    return 1;
  }
  for(i = 0; i < len; i++){
    printf("%02x ", tmpbuf[i]);
  }
  printf("\n\n");

  // test round-trip WEP encryption/decryption
  len = wep_encrypt((uint8_t*)text, tmpbuf, strlen(text) + 1, key, sizeof(key));
  if(len <= 0){
    printf("failed to encrypt!\n");
    return 1;
  }
  len = wep_decrypt(tmpbuf, cleartext, len, key, sizeof(key));
  if(len <= 0){
    printf("failed to decrypt!\n");
    return 1;
  }
  printf("round trip succesful: (%s).\n", cleartext);
  return 0;
}
