hostap_crypt_wep.c

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/*
 * Host AP crypt: host-based WEP encryption implementation for Host AP driver
 *
 * Copyright (c) 2002-2004, Jouni Malinen <jkmaline@cc.hut.fi>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation. See README and COPYING for
 * more details.
 */

#include <linux/config.h>
#include <linux/version.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/random.h>
#if (LINUX_VERSION_CODE < KERNEL_VERSION(2,5,44))
#include <linux/tqueue.h>
#else
#include <linux/workqueue.h>
#endif
#include <asm/string.h>

#include "hostap_crypt.h"
#include "hostap_compat.h"

MODULE_AUTHOR("Jouni Malinen");
MODULE_DESCRIPTION("Host AP crypt: WEP");
MODULE_LICENSE("GPL");


struct prism2_wep_data {
        u32 iv;
#define WEP_KEYS 4
#define WEP_KEY_LEN 13
        u8 keys[WEP_KEYS][WEP_KEY_LEN + 1];
        u8 key_lens[WEP_KEYS];
        int tx_key;
};

static const __u32 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
};


static void * prism2_wep_init(void)
{
        struct prism2_wep_data *priv;

#ifdef NEW_MODULE_CODE
        if (!try_module_get(THIS_MODULE))
                return NULL;
#else
        MOD_INC_USE_COUNT;
#endif

        priv = (struct prism2_wep_data *) kmalloc(sizeof(*priv), GFP_ATOMIC);
        if (priv == NULL) {
#ifdef NEW_MODULE_CODE
                module_put(THIS_MODULE);
#else
                MOD_DEC_USE_COUNT;
#endif
                return NULL;
        }
        memset(priv, 0, sizeof(*priv));

        /* start WEP IV from a random value */
        get_random_bytes(&priv->iv, 4);

        return priv;
}


static void prism2_wep_deinit(void *priv)
{
        kfree(priv);
#ifdef NEW_MODULE_CODE
        module_put(THIS_MODULE);
#else
        MOD_DEC_USE_COUNT;
#endif
}


/* Perform WEP encryption on given buffer. Buffer needs to has 4 bytes of
 * extra space (IV) in the beginning, then len bytes of data, and finally
 * 4 bytes of extra space (ICV). Both IV and ICV will be transmitted, so the
 * payload length increases with 8 bytes.
 *
 * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data))
 */
static int prism2_wep_encrypt(u8 *buf, int len, void *priv)
{
        struct prism2_wep_data *wep = priv;
        u32 i, j, k, crc, klen;
        u8 S[256], key[WEP_KEY_LEN + 3];
        u8 kpos, *pos;
#define S_SWAP(a,b) do { u8 t = S[a]; S[a] = S[b]; S[b] = t; } while(0)

        klen = 3 + wep->key_lens[wep->tx_key];

        wep->iv++;

        /* Fluhrer, Mantin, and Shamir have reported weaknesses in the key
         * scheduling algorithm of RC4. At least IVs (KeyByte + 3, 0xff, N)
         * can be used to speedup attacks, so avoid using them. */
        if ((wep->iv & 0xff00) == 0xff00) {
                u8 B = (wep->iv >> 16) & 0xff;
                if (B >= 3 && B < klen)
                        wep->iv += 0x0100;
        }

        /* Prepend 24-bit IV to RC4 key and TX frame */
        pos = buf;
        *pos++ = key[0] = (wep->iv >> 16) & 0xff;
        *pos++ = key[1] = (wep->iv >> 8) & 0xff;
        *pos++ = key[2] = wep->iv & 0xff;
        *pos++ = wep->tx_key << 6;

        /* Copy rest of the WEP key (the secret part) */
        memcpy(key + 3, wep->keys[wep->tx_key],
               wep->key_lens[wep->tx_key]);

        /* Setup RC4 state */
        for (i = 0; i < 256; i++)
                S[i] = i;
        j = 0;
        kpos = 0;
        for (i = 0; i < 256; i++) {
                j = (j + S[i] + key[kpos]) & 0xff;
                kpos++;
                if (kpos >= klen)
                        kpos = 0;
                S_SWAP(i, j);
        }

        /* Compute CRC32 over unencrypted data and apply RC4 to data */
        crc = ~0;
        i = j = 0;
        for (k = 0; k < len; k++) {
                crc = crc32_table[(crc ^ *pos) & 0xff] ^ (crc >> 8);
                i = (i + 1) & 0xff;
                j = (j + S[i]) & 0xff;
                S_SWAP(i, j);
                *pos++ ^= S[(S[i] + S[j]) & 0xff];
        }
        crc = ~crc;

        /* Append little-endian CRC32 and encrypt it to produce ICV */
        pos[0] = crc;
        pos[1] = crc >> 8;
        pos[2] = crc >> 16;
        pos[3] = crc >> 24;
        for (k = 0; k < 4; k++) {
                i = (i + 1) & 0xff;
                j = (j + S[i]) & 0xff;
                S_SWAP(i, j);
                *pos++ ^= S[(S[i] + S[j]) & 0xff];
        }

        return len + 8;
}


/* Perform WEP decryption on given buffer. Buffer includes whole WEP part of
 * the frame: IV (4 bytes), encrypted payload (including SNAP header),
 * ICV (4 bytes). len includes both IV and ICV.
 *
 * Returns 0 if frame was decrypted successfully and ICV was correct and -1 on
 * failure. If frame is OK, IV and ICV will be removed, i.e., decrypted payload
 * is moved to beginning of buf and last 8 bytes of buf should be ignored.
 */
static int prism2_wep_decrypt(u8 *buf, int len, void *priv)
{
        struct prism2_wep_data *wep = priv;
        u32 i, j, k, crc, klen;
        u8 S[256], key[WEP_KEY_LEN + 3];
        u8 keyidx, kpos, *dpos, *cpos;

        if (len < 8)
                return -1;

        key[0] = buf[0];
        key[1] = buf[1];
        key[2] = buf[2];
        keyidx = buf[3] >> 6;

        klen = 3 + wep->key_lens[keyidx];

        /* Copy rest of the WEP key (the secret part) */
        memcpy(key + 3, wep->keys[keyidx], wep->key_lens[keyidx]);

        /* Setup RC4 state */
        for (i = 0; i < 256; i++)
                S[i] = i;
        j = 0;
        kpos = 0;
        for (i = 0; i < 256; i++) {
                j = (j + S[i] + key[kpos]) & 0xff;
                kpos++;
                if (kpos >= klen)
                        kpos = 0;
                S_SWAP(i, j);
        }

        /* Apply RC4 to data and compute CRC32 over decrypted data */
        dpos = buf;
        cpos = buf + 4;
        crc = ~0;
        i = j = 0;
        for (k = 0; k < len - 8; k++) {
                i = (i + 1) & 0xff;
                j = (j + S[i]) & 0xff;
                S_SWAP(i, j);
                *dpos = *cpos++ ^ S[(S[i] + S[j]) & 0xff];
                crc = crc32_table[(crc ^ *dpos++) & 0xff] ^ (crc >> 8);
        }
        crc = ~crc;

        /* Encrypt little-endian CRC32 and verify that it matches with the
         * received ICV */
        dpos[0] = crc;
        dpos[1] = crc >> 8;
        dpos[2] = crc >> 16;
        dpos[3] = crc >> 24;
        for (k = 0; k < 4; k++) {
                i = (i + 1) & 0xff;
                j = (j + S[i]) & 0xff;
                S_SWAP(i, j);
                if ((*dpos++ ^ S[(S[i] + S[j]) & 0xff]) != *cpos++) {
                        /* ICV mismatch - drop frame */
                        return -1;
                }
        }

        return len - 8;
}


static int prism2_wep_set_key(int idx, void *key, int len, void *priv)
{
        struct prism2_wep_data *wep = priv;

        if (idx < 0 || idx >= WEP_KEYS || len < 0 || len > WEP_KEY_LEN)
                return -1;

        memcpy(wep->keys[idx], key, len);
        wep->key_lens[idx] = len;

        return 0;
}


static int prism2_wep_get_key(int idx, void *key, int len, void *priv)
{
        struct prism2_wep_data *wep = priv;

        if (idx < 0 || idx >= WEP_KEYS || len < wep->key_lens[idx])
                return -1;

        memcpy(key, wep->keys[idx], wep->key_lens[idx]);

        return wep->key_lens[idx];
}


static int prism2_wep_set_key_idx(int idx, void *priv)
{
        struct prism2_wep_data *wep = priv;

        if (idx < 0 || idx >= WEP_KEYS || wep->key_lens[idx] == 0)
                return -1;

        wep->tx_key = idx;

        return 0;
}


static int prism2_wep_get_key_idx(void *priv)
{
        struct prism2_wep_data *wep = priv;
        return wep->tx_key;
}


static struct hostap_crypto_ops hostap_crypt_wep = {
        .name                   = "WEP",
        .init                   = prism2_wep_init,
        .deinit                 = prism2_wep_deinit,
        .encrypt                = prism2_wep_encrypt,
        .decrypt                = prism2_wep_decrypt,
        .set_key                = prism2_wep_set_key,
        .get_key                = prism2_wep_get_key,
        .set_key_idx            = prism2_wep_set_key_idx,
        .get_key_idx            = prism2_wep_get_key_idx,
        .extra_prefix_len       = 4 /* IV */,
        .extra_postfix_len      = 4 /* ICV */
};


static int __init hostap_crypto_wep_init(void)
{
        if (hostap_register_crypto_ops(&hostap_crypt_wep) < 0)
                return -1;

        return 0;
}


static void __exit hostap_crypto_wep_exit(void)
{
        hostap_unregister_crypto_ops(&hostap_crypt_wep);
}


module_init(hostap_crypto_wep_init);
module_exit(hostap_crypto_wep_exit);

---