p80211wep.c

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/* src/p80211/p80211wep.c
*
* WEP encode/decode for P80211.
*
* Copyright (C) 2002 AbsoluteValue Systems, Inc.  All Rights Reserved.
* --------------------------------------------------------------------
*
* linux-wlan
*
*   The contents of this file are subject to the Mozilla Public
*   License Version 1.1 (the "License"); you may not use this file
*   except in compliance with the License. You may obtain a copy of
*   the License at http://www.mozilla.org/MPL/
*
*   Software distributed under the License is distributed on an "AS
*   IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
*   implied. See the License for the specific language governing
*   rights and limitations under the License.
*
*   Alternatively, the contents of this file may be used under the
*   terms of the GNU Public License version 2 (the "GPL"), in which
*   case the provisions of the GPL are applicable instead of the
*   above.  If you wish to allow the use of your version of this file
*   only under the terms of the GPL and not to allow others to use
*   your version of this file under the MPL, indicate your decision
*   by deleting the provisions above and replace them with the notice
*   and other provisions required by the GPL.  If you do not delete
*   the provisions above, a recipient may use your version of this
*   file under either the MPL or the GPL.
*
* --------------------------------------------------------------------
*
* Inquiries regarding the linux-wlan Open Source project can be
* made directly to:
*
* AbsoluteValue Systems Inc.
* [email protected]
* http://www.linux-wlan.com
*
* --------------------------------------------------------------------
*
* Portions of the development of this software were funded by
* Intersil Corporation as part of PRISM(R) chipset product development.
*
* --------------------------------------------------------------------
*/

/*================================================================*/
/* System Includes */

#include <linux/netdevice.h>
#include <linux/wireless.h>
#include <linux/random.h>
#include <linux/kernel.h>

/* #define WEP_DEBUG    */

#include "p80211hdr.h"
#include "p80211types.h"
#include "p80211msg.h"
#include "p80211conv.h"
#include "p80211netdev.h"

#define WEP_KEY(x)       (((x) & 0xC0) >> 6)

static const u32 wep_crc32_table[256] = {
    0x00000000L, 0x77073096L, 0xee0e612cL, 0x990951baL, 0x076dc419L,
    0x706af48fL, 0xe963a535L, 0x9e6495a3L, 0x0edb8832L, 0x79dcb8a4L,
    0xe0d5e91eL, 0x97d2d988L, 0x09b64c2bL, 0x7eb17cbdL, 0xe7b82d07L,
    0x90bf1d91L, 0x1db71064L, 0x6ab020f2L, 0xf3b97148L, 0x84be41deL,
    0x1adad47dL, 0x6ddde4ebL, 0xf4d4b551L, 0x83d385c7L, 0x136c9856L,
    0x646ba8c0L, 0xfd62f97aL, 0x8a65c9ecL, 0x14015c4fL, 0x63066cd9L,
    0xfa0f3d63L, 0x8d080df5L, 0x3b6e20c8L, 0x4c69105eL, 0xd56041e4L,
    0xa2677172L, 0x3c03e4d1L, 0x4b04d447L, 0xd20d85fdL, 0xa50ab56bL,
    0x35b5a8faL, 0x42b2986cL, 0xdbbbc9d6L, 0xacbcf940L, 0x32d86ce3L,
    0x45df5c75L, 0xdcd60dcfL, 0xabd13d59L, 0x26d930acL, 0x51de003aL,
    0xc8d75180L, 0xbfd06116L, 0x21b4f4b5L, 0x56b3c423L, 0xcfba9599L,
    0xb8bda50fL, 0x2802b89eL, 0x5f058808L, 0xc60cd9b2L, 0xb10be924L,
    0x2f6f7c87L, 0x58684c11L, 0xc1611dabL, 0xb6662d3dL, 0x76dc4190L,
    0x01db7106L, 0x98d220bcL, 0xefd5102aL, 0x71b18589L, 0x06b6b51fL,
    0x9fbfe4a5L, 0xe8b8d433L, 0x7807c9a2L, 0x0f00f934L, 0x9609a88eL,
    0xe10e9818L, 0x7f6a0dbbL, 0x086d3d2dL, 0x91646c97L, 0xe6635c01L,
    0x6b6b51f4L, 0x1c6c6162L, 0x856530d8L, 0xf262004eL, 0x6c0695edL,
    0x1b01a57bL, 0x8208f4c1L, 0xf50fc457L, 0x65b0d9c6L, 0x12b7e950L,
    0x8bbeb8eaL, 0xfcb9887cL, 0x62dd1ddfL, 0x15da2d49L, 0x8cd37cf3L,
    0xfbd44c65L, 0x4db26158L, 0x3ab551ceL, 0xa3bc0074L, 0xd4bb30e2L,
    0x4adfa541L, 0x3dd895d7L, 0xa4d1c46dL, 0xd3d6f4fbL, 0x4369e96aL,
    0x346ed9fcL, 0xad678846L, 0xda60b8d0L, 0x44042d73L, 0x33031de5L,
    0xaa0a4c5fL, 0xdd0d7cc9L, 0x5005713cL, 0x270241aaL, 0xbe0b1010L,
    0xc90c2086L, 0x5768b525L, 0x206f85b3L, 0xb966d409L, 0xce61e49fL,
    0x5edef90eL, 0x29d9c998L, 0xb0d09822L, 0xc7d7a8b4L, 0x59b33d17L,
    0x2eb40d81L, 0xb7bd5c3bL, 0xc0ba6cadL, 0xedb88320L, 0x9abfb3b6L,
    0x03b6e20cL, 0x74b1d29aL, 0xead54739L, 0x9dd277afL, 0x04db2615L,
    0x73dc1683L, 0xe3630b12L, 0x94643b84L, 0x0d6d6a3eL, 0x7a6a5aa8L,
    0xe40ecf0bL, 0x9309ff9dL, 0x0a00ae27L, 0x7d079eb1L, 0xf00f9344L,
    0x8708a3d2L, 0x1e01f268L, 0x6906c2feL, 0xf762575dL, 0x806567cbL,
    0x196c3671L, 0x6e6b06e7L, 0xfed41b76L, 0x89d32be0L, 0x10da7a5aL,
    0x67dd4accL, 0xf9b9df6fL, 0x8ebeeff9L, 0x17b7be43L, 0x60b08ed5L,
    0xd6d6a3e8L, 0xa1d1937eL, 0x38d8c2c4L, 0x4fdff252L, 0xd1bb67f1L,
    0xa6bc5767L, 0x3fb506ddL, 0x48b2364bL, 0xd80d2bdaL, 0xaf0a1b4cL,
    0x36034af6L, 0x41047a60L, 0xdf60efc3L, 0xa867df55L, 0x316e8eefL,
    0x4669be79L, 0xcb61b38cL, 0xbc66831aL, 0x256fd2a0L, 0x5268e236L,
    0xcc0c7795L, 0xbb0b4703L, 0x220216b9L, 0x5505262fL, 0xc5ba3bbeL,
    0xb2bd0b28L, 0x2bb45a92L, 0x5cb36a04L, 0xc2d7ffa7L, 0xb5d0cf31L,
    0x2cd99e8bL, 0x5bdeae1dL, 0x9b64c2b0L, 0xec63f226L, 0x756aa39cL,
    0x026d930aL, 0x9c0906a9L, 0xeb0e363fL, 0x72076785L, 0x05005713L,
    0x95bf4a82L, 0xe2b87a14L, 0x7bb12baeL, 0x0cb61b38L, 0x92d28e9bL,
    0xe5d5be0dL, 0x7cdcefb7L, 0x0bdbdf21L, 0x86d3d2d4L, 0xf1d4e242L,
    0x68ddb3f8L, 0x1fda836eL, 0x81be16cdL, 0xf6b9265bL, 0x6fb077e1L,
    0x18b74777L, 0x88085ae6L, 0xff0f6a70L, 0x66063bcaL, 0x11010b5cL,
    0x8f659effL, 0xf862ae69L, 0x616bffd3L, 0x166ccf45L, 0xa00ae278L,
    0xd70dd2eeL, 0x4e048354L, 0x3903b3c2L, 0xa7672661L, 0xd06016f7L,
    0x4969474dL, 0x3e6e77dbL, 0xaed16a4aL, 0xd9d65adcL, 0x40df0b66L,
    0x37d83bf0L, 0xa9bcae53L, 0xdebb9ec5L, 0x47b2cf7fL, 0x30b5ffe9L,
    0xbdbdf21cL, 0xcabac28aL, 0x53b39330L, 0x24b4a3a6L, 0xbad03605L,
    0xcdd70693L, 0x54de5729L, 0x23d967bfL, 0xb3667a2eL, 0xc4614ab8L,
    0x5d681b02L, 0x2a6f2b94L, 0xb40bbe37L, 0xc30c8ea1L, 0x5a05df1bL,
    0x2d02ef8dL
};

/* keylen in bytes! */

int wep_change_key(wlandevice_t *wlandev, int keynum, u8 *key, int keylen)
{
    if (keylen < 0)
        return -1;
    if (keylen >= MAX_KEYLEN)
        return -1;
    if (key == NULL)
        return -1;
    if (keynum < 0)
        return -1;
    if (keynum >= NUM_WEPKEYS)
        return -1;

#ifdef WEP_DEBUG
    printk(KERN_DEBUG "WEP key %d len %d = %*phC\n", keynum, keylen,
              8, key);
#endif

    wlandev->wep_keylens[keynum] = keylen;
    memcpy(wlandev->wep_keys[keynum], key, keylen);

    return 0;
}

/*
  4-byte IV at start of buffer, 4-byte ICV at end of buffer.
  if successful, buf start is payload begin, length -= 8;
 */
int wep_decrypt(wlandevice_t *wlandev, u8 *buf, u32 len, int key_override,
        u8 *iv, u8 *icv)
{
    u32 i, j, k, crc, keylen;
    u8 s[256], key[64], c_crc[4];
    u8 keyidx;

    /* Needs to be at least 8 bytes of payload */
    if (len <= 0)
        return -1;

    /* initialize the first bytes of the key from the IV */
    key[0] = iv[0];
    key[1] = iv[1];
    key[2] = iv[2];
    keyidx = WEP_KEY(iv[3]);

    if (key_override >= 0)
        keyidx = key_override;

    if (keyidx >= NUM_WEPKEYS)
        return -2;

    keylen = wlandev->wep_keylens[keyidx];

    if (keylen == 0)
        return -3;

    /* copy the rest of the key over from the designated key */
    memcpy(key + 3, wlandev->wep_keys[keyidx], keylen);

    keylen += 3;        /* add in IV bytes */

#ifdef WEP_DEBUG
    printk(KERN_DEBUG "D %d: %*ph (%d %d) %*phC\n", len, 3, key,
              keyidx, keylen, 5, key + 3);
#endif

    /* 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;
        swap(i, j);
    }

    /* Apply the RC4 to the data, update the CRC32 */
    crc = ~0;
    i = j = 0;
    for (k = 0; k < len; k++) {
        i = (i + 1) & 0xff;
        j = (j + s[i]) & 0xff;
        swap(i, j);
        buf[k] ^= s[(s[i] + s[j]) & 0xff];
        crc = wep_crc32_table[(crc ^ buf[k]) & 0xff] ^ (crc >> 8);
    }
    crc = ~crc;

    /* now let's check the crc */
    c_crc[0] = crc;
    c_crc[1] = crc >> 8;
    c_crc[2] = crc >> 16;
    c_crc[3] = crc >> 24;

    for (k = 0; k < 4; k++) {
        i = (i + 1) & 0xff;
        j = (j + s[i]) & 0xff;
        swap(i, j);
        if ((c_crc[k] ^ s[(s[i] + s[j]) & 0xff]) != icv[k])
            return -(4 | (k << 4)); /* ICV mismatch */
    }

    return 0;
}

/* encrypts in-place. */
int wep_encrypt(wlandevice_t *wlandev, u8 *buf, u8 *dst, u32 len, int keynum,
        u8 *iv, u8 *icv)
{
    u32 i, j, k, crc, keylen;
    u8 s[256], key[64];

    /* no point in WEPping an empty frame */
    if (len <= 0)
        return -1;

    /* we need to have a real key.. */
    if (keynum >= NUM_WEPKEYS)
        return -2;
    keylen = wlandev->wep_keylens[keynum];
    if (keylen <= 0)
        return -3;

    /* use a random IV.  And skip known weak ones. */
    get_random_bytes(iv, 3);
    while ((iv[1] == 0xff) && (iv[0] >= 3) && (iv[0] < keylen))
        get_random_bytes(iv, 3);

    iv[3] = (keynum & 0x03) << 6;

    key[0] = iv[0];
    key[1] = iv[1];
    key[2] = iv[2];

    /* copy the rest of the key over from the designated key */
    memcpy(key + 3, wlandev->wep_keys[keynum], keylen);

    keylen += 3;        /* add in IV bytes */

#ifdef WEP_DEBUG
    printk(KERN_DEBUG "E %d (%d/%d %d) %*ph %*phC\n", len,
              iv[3], keynum, keylen, 3, key, 5, key + 3);
#endif

    /* 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;
        swap(i, j);
    }

    /* Update CRC32 then apply RC4 to the data */
    crc = ~0;
    i = j = 0;
    for (k = 0; k < len; k++) {
        crc = wep_crc32_table[(crc ^ buf[k]) & 0xff] ^ (crc >> 8);
        i = (i + 1) & 0xff;
        j = (j + s[i]) & 0xff;
        swap(i, j);
        dst[k] = buf[k] ^ s[(s[i] + s[j]) & 0xff];
    }
    crc = ~crc;

    /* now let's encrypt the crc */
    icv[0] = crc;
    icv[1] = crc >> 8;
    icv[2] = crc >> 16;
    icv[3] = crc >> 24;

    for (k = 0; k < 4; k++) {
        i = (i + 1) & 0xff;
        j = (j + s[i]) & 0xff;
        swap(i, j);
        icv[k] ^= s[(s[i] + s[j]) & 0xff];
    }

    return 0;
}