drivers/staging/rtl8192su/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 //#include <linux/config.h>
  13 #include <linux/version.h>
  14 #include <linux/module.h>
  15 #include <linux/init.h>
  16 #include <linux/slab.h>
  17 #include <linux/random.h>
  18 #include <linux/skbuff.h>
  19 #include <asm/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 struct prism2_wep_data {
  32         u32 iv;
  33 #define WEP_KEY_LEN 13
  34         u8 key[WEP_KEY_LEN + 1];
  35         u8 key_len;
  36         u8 key_idx;
  37         struct crypto_blkcipher *tx_tfm;
  38         struct crypto_blkcipher *rx_tfm;
  39 };
  40
  41
  42 static void * prism2_wep_init(int keyidx)
  43 {
  44         struct prism2_wep_data *priv;
  45
  46         priv = kmalloc(sizeof(*priv), GFP_ATOMIC);
  47         if (priv == NULL)
  48                 goto fail;
  49         memset(priv, 0, sizeof(*priv));
  50         priv->key_idx = keyidx;
  51
  52         priv->tx_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0, CRYPTO_ALG_ASYNC);
  53         if (IS_ERR(priv->tx_tfm)) {
  54                 printk(KERN_DEBUG "ieee80211_crypt_wep: could not allocate "
  55                        "crypto API arc4\n");
  56                 priv->tx_tfm = NULL;
  57                 goto fail;
  58         }
  59         priv->rx_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0, CRYPTO_ALG_ASYNC);
  60         if (IS_ERR(priv->rx_tfm)) {
  61                 printk(KERN_DEBUG "ieee80211_crypt_wep: could not allocate "
  62                        "crypto API arc4\n");
  63                 priv->rx_tfm = NULL;
  64                 goto fail;
  65         }
  66
  67         /* start WEP IV from a random value */
  68         get_random_bytes(&priv->iv, 4);
  69
  70         return priv;
  71
  72 fail:
  73         if (priv) {
  74                 if (priv->tx_tfm)
  75                         crypto_free_blkcipher(priv->tx_tfm);
  76                 if (priv->rx_tfm)
  77                         crypto_free_blkcipher(priv->rx_tfm);
  78                 kfree(priv);
  79         }
  80
  81         return NULL;
  82 }
  83
  84
  85 static void prism2_wep_deinit(void *priv)
  86 {
  87         struct prism2_wep_data *_priv = priv;
  88
  89         if (_priv) {
  90                 if (_priv->tx_tfm)
  91                         crypto_free_blkcipher(_priv->tx_tfm);
  92                 if (_priv->rx_tfm)
  93                         crypto_free_blkcipher(_priv->rx_tfm);
  94         }
  95         kfree(priv);
  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         u32 klen, len;
 108         u8 key[WEP_KEY_LEN + 3];
 109         u8 *pos;
 110         cb_desc *tcb_desc = (cb_desc *)(skb->cb + MAX_DEV_ADDR_SIZE);
 111         struct blkcipher_desc desc = { .tfm = wep->tx_tfm };
 112         u32 crc;
 113         u8 *icv;
 114         struct scatterlist sg;
 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         if (!tcb_desc->bHwSec)
 147         {
 148
 149                 /* Append little-endian CRC32 and encrypt it to produce ICV */
 150                 crc = ~crc32_le(~0, pos, len);
 151                 icv = skb_put(skb, 4);
 152                 icv[0] = crc;
 153                 icv[1] = crc >> 8;
 154                 icv[2] = crc >> 16;
 155                 icv[3] = crc >> 24;
 156
 157                 crypto_blkcipher_setkey(wep->tx_tfm, key, klen);
 158                 sg_init_one(&sg, pos, len+4);
 159
 160                 return crypto_blkcipher_encrypt(&desc, &sg, &sg, len + 4);
 161         }
 162
 163         return 0;
 164 }
 165
 166
 167 /* Perform WEP decryption on given buffer. Buffer includes whole WEP part of
 168  * the frame: IV (4 bytes), encrypted payload (including SNAP header),
 169  * ICV (4 bytes). len includes both IV and ICV.
 170  *
 171  * Returns 0 if frame was decrypted successfully and ICV was correct and -1 on
 172  * failure. If frame is OK, IV and ICV will be removed.
 173  */
 174 static int prism2_wep_decrypt(struct sk_buff *skb, int hdr_len, void *priv)
 175 {
 176         struct prism2_wep_data *wep = priv;
 177         u32  klen, plen;
 178         u8 key[WEP_KEY_LEN + 3];
 179         u8 keyidx, *pos;
 180         cb_desc *tcb_desc = (cb_desc *)(skb->cb + MAX_DEV_ADDR_SIZE);
 181         struct blkcipher_desc desc = { .tfm = wep->rx_tfm };
 182         u32 crc;
 183         u8 icv[4];
 184         struct scatterlist sg;
 185         if (skb->len < hdr_len + 8)
 186                 return -1;
 187
 188         pos = skb->data + hdr_len;
 189         key[0] = *pos++;
 190         key[1] = *pos++;
 191         key[2] = *pos++;
 192         keyidx = *pos++ >> 6;
 193         if (keyidx != wep->key_idx)
 194                 return -1;
 195
 196         klen = 3 + wep->key_len;
 197
 198         /* Copy rest of the WEP key (the secret part) */
 199         memcpy(key + 3, wep->key, wep->key_len);
 200
 201         /* Apply RC4 to data and compute CRC32 over decrypted data */
 202         plen = skb->len - hdr_len - 8;
 203
 204         if (!tcb_desc->bHwSec)
 205         {
 206                 crypto_blkcipher_setkey(wep->rx_tfm, key, klen);
 207                 sg_init_one(&sg, pos, plen + 4);
 208
 209                 if (crypto_blkcipher_decrypt(&desc, &sg, &sg, plen + 4))
 210                         return -7;
 211
 212                 crc = ~crc32_le(~0, pos, plen);
 213                 icv[0] = crc;
 214                 icv[1] = crc >> 8;
 215                 icv[2] = crc >> 16;
 216                 icv[3] = crc >> 24;
 217                 if (memcmp(icv, pos + plen, 4) != 0) {
 218                         /* ICV mismatch - drop frame */
 219                         return -2;
 220                 }
 221         }
 222         /* Remove IV and ICV */
 223         memmove(skb->data + 4, skb->data, hdr_len);
 224         skb_pull(skb, 4);
 225         skb_trim(skb, skb->len - 4);
 226
 227         return 0;
 228 }
 229
 230
 231 static int prism2_wep_set_key(void *key, int len, u8 *seq, void *priv)
 232 {
 233         struct prism2_wep_data *wep = priv;
 234
 235         if (len < 0 || len > WEP_KEY_LEN)
 236                 return -1;
 237
 238         memcpy(wep->key, key, len);
 239         wep->key_len = len;
 240
 241         return 0;
 242 }
 243
 244
 245 static int prism2_wep_get_key(void *key, int len, u8 *seq, void *priv)
 246 {
 247         struct prism2_wep_data *wep = priv;
 248
 249         if (len < wep->key_len)
 250                 return -1;
 251
 252         memcpy(key, wep->key, wep->key_len);
 253
 254         return wep->key_len;
 255 }
 256
 257
 258 static char * prism2_wep_print_stats(char *p, void *priv)
 259 {
 260         struct prism2_wep_data *wep = priv;
 261         p += sprintf(p, "key[%d] alg=WEP len=%d\n",
 262                      wep->key_idx, wep->key_len);
 263         return p;
 264 }
 265
 266
 267 static struct ieee80211_crypto_ops ieee80211_crypt_wep = {
 268         .name                   = "WEP",
 269         .init                   = prism2_wep_init,
 270         .deinit                 = prism2_wep_deinit,
 271         .encrypt_mpdu           = prism2_wep_encrypt,
 272         .decrypt_mpdu           = prism2_wep_decrypt,
 273         .encrypt_msdu           = NULL,
 274         .decrypt_msdu           = NULL,
 275         .set_key                = prism2_wep_set_key,
 276         .get_key                = prism2_wep_get_key,
 277         .print_stats            = prism2_wep_print_stats,
 278         .extra_prefix_len       = 4, /* IV */
 279         .extra_postfix_len      = 4, /* ICV */
 280         .owner                  = THIS_MODULE,
 281 };
 282
 283 int __init ieee80211_crypto_wep_init(void)
 284 {
 285         return ieee80211_register_crypto_ops(&ieee80211_crypt_wep);
 286 }
 287
 288 void __exit ieee80211_crypto_wep_exit(void)
 289 {
 290         ieee80211_unregister_crypto_ops(&ieee80211_crypt_wep);
 291 }
 292
 293 void ieee80211_wep_null(void)
 294 {
 295 //      printk("============>%s()\n", __FUNCTION__);
 296         return;
 297 }