drivers/staging/rtl8187se/ieee80211/ieee80211_crypt_wep.c

   1 /*
   2  * Host AP crypt: host-based WEP encryption implementation for Host AP driver
   3  *
   4  * Copyright (c) 2002-2004, Jouni Malinen <jkmaline@cc.hut.fi>
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License version 2 as
   8  * published by the Free Software Foundation. See README and COPYING for
   9  * more details.
  10  */
  11
  12 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  13
  14 //#include <linux/config.h>
  15 #include <linux/module.h>
  16 #include <linux/slab.h>
  17 #include <linux/random.h>
  18 #include <linux/skbuff.h>
  19 #include <linux/string.h>
  20
  21 #include "ieee80211.h"
  22
  23 #include <linux/crypto.h>
  24 #include <linux/scatterlist.h>
  25 #include <linux/crc32.h>
  26
  27 MODULE_AUTHOR("Jouni Malinen");
  28 MODULE_DESCRIPTION("Host AP crypt: WEP");
  29 MODULE_LICENSE("GPL");
  30
  31
  32
  33 struct prism2_wep_data {
  34         u32 iv;
  35 #define WEP_KEY_LEN 13
  36         u8 key[WEP_KEY_LEN + 1];
  37         u8 key_len;
  38         u8 key_idx;
  39         struct crypto_blkcipher *tx_tfm;
  40         struct crypto_blkcipher *rx_tfm;
  41 };
  42
  43
  44 static void *prism2_wep_init(int keyidx)
  45 {
  46         struct prism2_wep_data *priv;
  47
  48         priv = kzalloc(sizeof(*priv), GFP_ATOMIC);
  49         if (priv == NULL)
  50                 goto fail;
  51         priv->key_idx = keyidx;
  52         priv->tx_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0, CRYPTO_ALG_ASYNC);
  53         if (IS_ERR(priv->tx_tfm)) {
  54                 pr_debug("could not allocate crypto API arc4\n");
  55                 priv->tx_tfm = NULL;
  56                 goto fail;
  57         }
  58         priv->rx_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0, CRYPTO_ALG_ASYNC);
  59         if (IS_ERR(priv->rx_tfm)) {
  60                 pr_debug("could not allocate crypto API arc4\n");
  61                 priv->rx_tfm = NULL;
  62                 goto fail;
  63         }
  64
  65         /* start WEP IV from a random value */
  66         get_random_bytes(&priv->iv, 4);
  67
  68         return priv;
  69
  70 fail:
  71         if (priv) {
  72                 if (priv->tx_tfm)
  73                         crypto_free_blkcipher(priv->tx_tfm);
  74                 if (priv->rx_tfm)
  75                         crypto_free_blkcipher(priv->rx_tfm);
  76                 kfree(priv);
  77         }
  78
  79         return NULL;
  80 }
  81
  82
  83 static void prism2_wep_deinit(void *priv)
  84 {
  85         struct prism2_wep_data *_priv = priv;
  86
  87         if (_priv) {
  88                 if (_priv->tx_tfm)
  89                         crypto_free_blkcipher(_priv->tx_tfm);
  90                 if (_priv->rx_tfm)
  91                         crypto_free_blkcipher(_priv->rx_tfm);
  92         }
  93
  94         kfree(priv);
  95 }
  96
  97
  98 /* Perform WEP encryption on given skb that has at least 4 bytes of headroom
  99  * for IV and 4 bytes of tailroom for ICV. Both IV and ICV will be transmitted,
 100  * so the payload length increases with 8 bytes.
 101  *
 102  * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data))
 103  */
 104 static int prism2_wep_encrypt(struct sk_buff *skb, int hdr_len, void *priv)
 105 {
 106         struct prism2_wep_data *wep = priv;
 107         struct blkcipher_desc desc = { .tfm = wep->tx_tfm };
 108         u32 klen, len;
 109         u8 key[WEP_KEY_LEN + 3];
 110         u8 *pos;
 111         u32 crc;
 112         u8 *icv;
 113         struct scatterlist sg;
 114
 115         if (skb_headroom(skb) < 4 || skb_tailroom(skb) < 4 ||
 116             skb->len < hdr_len)
 117                 return -1;
 118
 119         len = skb->len - hdr_len;
 120         pos = skb_push(skb, 4);
 121         memmove(pos, pos + 4, hdr_len);
 122         pos += hdr_len;
 123
 124         klen = 3 + wep->key_len;
 125
 126         wep->iv++;
 127
 128         /* Fluhrer, Mantin, and Shamir have reported weaknesses in the key
 129          * scheduling algorithm of RC4. At least IVs (KeyByte + 3, 0xff, N)
 130          * can be used to speedup attacks, so avoid using them. */
 131         if ((wep->iv & 0xff00) == 0xff00) {
 132                 u8 B = (wep->iv >> 16) & 0xff;
 133                 if (B >= 3 && B < klen)
 134                         wep->iv += 0x0100;
 135         }
 136
 137         /* Prepend 24-bit IV to RC4 key and TX frame */
 138         *pos++ = key[0] = (wep->iv >> 16) & 0xff;
 139         *pos++ = key[1] = (wep->iv >> 8) & 0xff;
 140         *pos++ = key[2] = wep->iv & 0xff;
 141         *pos++ = wep->key_idx << 6;
 142
 143         /* Copy rest of the WEP key (the secret part) */
 144         memcpy(key + 3, wep->key, wep->key_len);
 145
 146         /* Append little-endian CRC32 and encrypt it to produce ICV */
 147         crc = ~crc32_le(~0, pos, len);
 148         icv = skb_put(skb, 4);
 149         icv[0] = crc;
 150         icv[1] = crc >> 8;
 151         icv[2] = crc >> 16;
 152         icv[3] = crc >> 24;
 153
 154         crypto_blkcipher_setkey(wep->tx_tfm, key, klen);
 155         sg_init_one(&sg, pos, len + 4);
 156
 157         return crypto_blkcipher_encrypt(&desc, &sg, &sg, len + 4);
 158 }
 159
 160
 161 /* Perform WEP decryption on given buffer. Buffer includes whole WEP part of
 162  * the frame: IV (4 bytes), encrypted payload (including SNAP header),
 163  * ICV (4 bytes). len includes both IV and ICV.
 164  *
 165  * Returns 0 if frame was decrypted successfully and ICV was correct and -1 on
 166  * failure. If frame is OK, IV and ICV will be removed.
 167  */
 168 static int prism2_wep_decrypt(struct sk_buff *skb, int hdr_len, void *priv)
 169 {
 170         struct prism2_wep_data *wep = priv;
 171         struct blkcipher_desc desc = { .tfm = wep->rx_tfm };
 172         u32 klen, plen;
 173         u8 key[WEP_KEY_LEN + 3];
 174         u8 keyidx, *pos;
 175         u32 crc;
 176         u8 icv[4];
 177         struct scatterlist sg;
 178
 179         if (skb->len < hdr_len + 8)
 180                 return -1;
 181
 182         pos = skb->data + hdr_len;
 183         key[0] = *pos++;
 184         key[1] = *pos++;
 185         key[2] = *pos++;
 186         keyidx = *pos++ >> 6;
 187         if (keyidx != wep->key_idx)
 188                 return -1;
 189
 190         klen = 3 + wep->key_len;
 191
 192         /* Copy rest of the WEP key (the secret part) */
 193         memcpy(key + 3, wep->key, wep->key_len);
 194
 195         /* Apply RC4 to data and compute CRC32 over decrypted data */
 196         plen = skb->len - hdr_len - 8;
 197
 198         crypto_blkcipher_setkey(wep->rx_tfm, key, klen);
 199         sg_init_one(&sg, pos, plen + 4);
 200
 201         if (crypto_blkcipher_decrypt(&desc, &sg, &sg, plen + 4))
 202                 return -7;
 203
 204         crc = ~crc32_le(~0, pos, plen);
 205         icv[0] = crc;
 206         icv[1] = crc >> 8;
 207         icv[2] = crc >> 16;
 208         icv[3] = crc >> 24;
 209
 210         if (memcmp(icv, pos + plen, 4) != 0) {
 211                 /* ICV mismatch - drop frame */
 212                 return -2;
 213         }
 214
 215         /* Remove IV and ICV */
 216         memmove(skb->data + 4, skb->data, hdr_len);
 217         skb_pull(skb, 4);
 218         skb_trim(skb, skb->len - 4);
 219         return 0;
 220 }
 221
 222
 223 static int prism2_wep_set_key(void *key, int len, u8 *seq, void *priv)
 224 {
 225         struct prism2_wep_data *wep = priv;
 226
 227         if (len < 0 || len > WEP_KEY_LEN)
 228                 return -1;
 229
 230         memcpy(wep->key, key, len);
 231         wep->key_len = len;
 232
 233         return 0;
 234 }
 235
 236
 237 static int prism2_wep_get_key(void *key, int len, u8 *seq, void *priv)
 238 {
 239         struct prism2_wep_data *wep = priv;
 240
 241         if (len < wep->key_len)
 242                 return -1;
 243
 244         memcpy(key, wep->key, wep->key_len);
 245
 246         return wep->key_len;
 247 }
 248
 249
 250 static char *prism2_wep_print_stats(char *p, void *priv)
 251 {
 252         struct prism2_wep_data *wep = priv;
 253         p += sprintf(p, "key[%d] alg=WEP len=%d\n",
 254                      wep->key_idx, wep->key_len);
 255         return p;
 256 }
 257
 258
 259 static struct ieee80211_crypto_ops ieee80211_crypt_wep = {
 260         .name                   = "WEP",
 261         .init                   = prism2_wep_init,
 262         .deinit                 = prism2_wep_deinit,
 263         .encrypt_mpdu           = prism2_wep_encrypt,
 264         .decrypt_mpdu           = prism2_wep_decrypt,
 265         .encrypt_msdu           = NULL,
 266         .decrypt_msdu           = NULL,
 267         .set_key                = prism2_wep_set_key,
 268         .get_key                = prism2_wep_get_key,
 269         .print_stats            = prism2_wep_print_stats,
 270         .extra_prefix_len       = 4, /* IV */
 271         .extra_postfix_len      = 4, /* ICV */
 272         .owner                  = THIS_MODULE,
 273 };
 274
 275
 276 int ieee80211_crypto_wep_init(void)
 277 {
 278         return ieee80211_register_crypto_ops(&ieee80211_crypt_wep);
 279 }
 280
 281
 282 void ieee80211_crypto_wep_exit(void)
 283 {
 284         ieee80211_unregister_crypto_ops(&ieee80211_crypt_wep);
 285 }
 286
 287
 288 void ieee80211_wep_null(void)
 289 {
 290 //      printk("============>%s()\n", __func__);
 291         return;
 292 }