drivers/staging/rtl8192u/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/module.h>
  13 #include <linux/init.h>
  14 #include <linux/slab.h>
  15 #include <linux/random.h>
  16 #include <linux/skbuff.h>
  17 #include <asm/string.h>
  18
  19 #include "ieee80211.h"
  20
  21 #include <linux/crypto.h>
  22     #include <linux/scatterlist.h>
  23 #include <linux/crc32.h>
  24
  25 MODULE_AUTHOR("Jouni Malinen");
  26 MODULE_DESCRIPTION("Host AP crypt: WEP");
  27 MODULE_LICENSE("GPL");
  28
  29 struct prism2_wep_data {
  30         u32 iv;
  31 #define WEP_KEY_LEN 13
  32         u8 key[WEP_KEY_LEN + 1];
  33         u8 key_len;
  34         u8 key_idx;
  35         struct crypto_blkcipher *tx_tfm;
  36         struct crypto_blkcipher *rx_tfm;
  37 };
  38
  39
  40 static void *prism2_wep_init(int keyidx)
  41 {
  42         struct prism2_wep_data *priv;
  43
  44         priv = kzalloc(sizeof(*priv), GFP_ATOMIC);
  45         if (priv == NULL)
  46                 goto fail;
  47         priv->key_idx = keyidx;
  48
  49         priv->tx_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0, CRYPTO_ALG_ASYNC);
  50         if (IS_ERR(priv->tx_tfm)) {
  51                 printk(KERN_DEBUG "ieee80211_crypt_wep: could not allocate "
  52                        "crypto API arc4\n");
  53                 priv->tx_tfm = NULL;
  54                 goto fail;
  55         }
  56         priv->rx_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0, CRYPTO_ALG_ASYNC);
  57         if (IS_ERR(priv->rx_tfm)) {
  58                 printk(KERN_DEBUG "ieee80211_crypt_wep: could not allocate "
  59                        "crypto API arc4\n");
  60                 priv->rx_tfm = NULL;
  61                 goto fail;
  62         }
  63
  64         /* start WEP IV from a random value */
  65         get_random_bytes(&priv->iv, 4);
  66
  67         return priv;
  68
  69 fail:
  70         if (priv) {
  71                 if (priv->tx_tfm)
  72                         crypto_free_blkcipher(priv->tx_tfm);
  73                 if (priv->rx_tfm)
  74                         crypto_free_blkcipher(priv->rx_tfm);
  75                 kfree(priv);
  76         }
  77
  78         return NULL;
  79 }
  80
  81
  82 static void prism2_wep_deinit(void *priv)
  83 {
  84         struct prism2_wep_data *_priv = priv;
  85
  86         if (_priv) {
  87                 if (_priv->tx_tfm)
  88                         crypto_free_blkcipher(_priv->tx_tfm);
  89                 if (_priv->rx_tfm)
  90                         crypto_free_blkcipher(_priv->rx_tfm);
  91         }
  92         kfree(priv);
  93 }
  94
  95 /* Perform WEP encryption on given skb that has at least 4 bytes of headroom
  96  * for IV and 4 bytes of tailroom for ICV. Both IV and ICV will be transmitted,
  97  * so the payload length increases with 8 bytes.
  98  *
  99  * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data))
 100  */
 101 static int prism2_wep_encrypt(struct sk_buff *skb, int hdr_len, void *priv)
 102 {
 103         struct prism2_wep_data *wep = priv;
 104         u32 klen, len;
 105         u8 key[WEP_KEY_LEN + 3];
 106         u8 *pos;
 107         cb_desc *tcb_desc = (cb_desc *)(skb->cb + MAX_DEV_ADDR_SIZE);
 108         struct blkcipher_desc desc = {.tfm = wep->tx_tfm};
 109         u32 crc;
 110         u8 *icv;
 111         struct scatterlist sg;
 112         if (skb_headroom(skb) < 4 || skb_tailroom(skb) < 4 ||
 113             skb->len < hdr_len)
 114                 return -1;
 115
 116         len = skb->len - hdr_len;
 117         pos = skb_push(skb, 4);
 118         memmove(pos, pos + 4, hdr_len);
 119         pos += hdr_len;
 120
 121         klen = 3 + wep->key_len;
 122
 123         wep->iv++;
 124
 125         /* Fluhrer, Mantin, and Shamir have reported weaknesses in the key
 126          * scheduling algorithm of RC4. At least IVs (KeyByte + 3, 0xff, N)
 127          * can be used to speedup attacks, so avoid using them. */
 128         if ((wep->iv & 0xff00) == 0xff00) {
 129                 u8 B = (wep->iv >> 16) & 0xff;
 130                 if (B >= 3 && B < klen)
 131                         wep->iv += 0x0100;
 132         }
 133
 134         /* Prepend 24-bit IV to RC4 key and TX frame */
 135         *pos++ = key[0] = (wep->iv >> 16) & 0xff;
 136         *pos++ = key[1] = (wep->iv >> 8) & 0xff;
 137         *pos++ = key[2] = wep->iv & 0xff;
 138         *pos++ = wep->key_idx << 6;
 139
 140         /* Copy rest of the WEP key (the secret part) */
 141         memcpy(key + 3, wep->key, wep->key_len);
 142
 143         if (!tcb_desc->bHwSec)
 144         {
 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         return 0;
 161 }
 162
 163
 164 /* Perform WEP decryption on given buffer. Buffer includes whole WEP part of
 165  * the frame: IV (4 bytes), encrypted payload (including SNAP header),
 166  * ICV (4 bytes). len includes both IV and ICV.
 167  *
 168  * Returns 0 if frame was decrypted successfully and ICV was correct and -1 on
 169  * failure. If frame is OK, IV and ICV will be removed.
 170  */
 171 static int prism2_wep_decrypt(struct sk_buff *skb, int hdr_len, void *priv)
 172 {
 173         struct prism2_wep_data *wep = priv;
 174         u32  klen, plen;
 175         u8 key[WEP_KEY_LEN + 3];
 176         u8 keyidx, *pos;
 177         cb_desc *tcb_desc = (cb_desc *)(skb->cb + MAX_DEV_ADDR_SIZE);
 178         struct blkcipher_desc desc = {.tfm = wep->rx_tfm};
 179         u32 crc;
 180         u8 icv[4];
 181         struct scatterlist sg;
 182         if (skb->len < hdr_len + 8)
 183                 return -1;
 184
 185         pos = skb->data + hdr_len;
 186         key[0] = *pos++;
 187         key[1] = *pos++;
 188         key[2] = *pos++;
 189         keyidx = *pos++ >> 6;
 190         if (keyidx != wep->key_idx)
 191                 return -1;
 192
 193         klen = 3 + wep->key_len;
 194
 195         /* Copy rest of the WEP key (the secret part) */
 196         memcpy(key + 3, wep->key, wep->key_len);
 197
 198         /* Apply RC4 to data and compute CRC32 over decrypted data */
 199         plen = skb->len - hdr_len - 8;
 200
 201         if (!tcb_desc->bHwSec)
 202         {
 203                 crypto_blkcipher_setkey(wep->rx_tfm, key, klen);
 204                 sg_init_one(&sg, pos, plen+4);
 205
 206                 if (crypto_blkcipher_decrypt(&desc, &sg, &sg, plen + 4))
 207                         return -7;
 208
 209                 crc = ~crc32_le(~0, pos, plen);
 210                 icv[0] = crc;
 211                 icv[1] = crc >> 8;
 212                 icv[2] = crc >> 16;
 213                 icv[3] = crc >> 24;
 214                 if (memcmp(icv, pos + plen, 4) != 0) {
 215                         /* ICV mismatch - drop frame */
 216                         return -2;
 217                 }
 218         }
 219         /* Remove IV and ICV */
 220         memmove(skb->data + 4, skb->data, hdr_len);
 221         skb_pull(skb, 4);
 222         skb_trim(skb, skb->len - 4);
 223
 224         return 0;
 225 }
 226
 227
 228 static int prism2_wep_set_key(void *key, int len, u8 *seq, void *priv)
 229 {
 230         struct prism2_wep_data *wep = priv;
 231
 232         if (len < 0 || len > WEP_KEY_LEN)
 233                 return -1;
 234
 235         memcpy(wep->key, key, len);
 236         wep->key_len = len;
 237
 238         return 0;
 239 }
 240
 241
 242 static int prism2_wep_get_key(void *key, int len, u8 *seq, void *priv)
 243 {
 244         struct prism2_wep_data *wep = priv;
 245
 246         if (len < wep->key_len)
 247                 return -1;
 248
 249         memcpy(key, wep->key, wep->key_len);
 250
 251         return wep->key_len;
 252 }
 253
 254
 255 static char *prism2_wep_print_stats(char *p, void *priv)
 256 {
 257         struct prism2_wep_data *wep = priv;
 258         p += sprintf(p, "key[%d] alg=WEP len=%d\n",
 259                      wep->key_idx, wep->key_len);
 260         return p;
 261 }
 262
 263
 264 static struct ieee80211_crypto_ops ieee80211_crypt_wep = {
 265         .name                   = "WEP",
 266         .init                   = prism2_wep_init,
 267         .deinit                 = prism2_wep_deinit,
 268         .encrypt_mpdu           = prism2_wep_encrypt,
 269         .decrypt_mpdu           = prism2_wep_decrypt,
 270         .encrypt_msdu           = NULL,
 271         .decrypt_msdu           = NULL,
 272         .set_key                = prism2_wep_set_key,
 273         .get_key                = prism2_wep_get_key,
 274         .print_stats            = prism2_wep_print_stats,
 275         .extra_prefix_len       = 4, /* IV */
 276         .extra_postfix_len      = 4, /* ICV */
 277         .owner                  = THIS_MODULE,
 278 };
 279
 280 int __init ieee80211_crypto_wep_init(void)
 281 {
 282         return ieee80211_register_crypto_ops(&ieee80211_crypt_wep);
 283 }
 284
 285 void __exit ieee80211_crypto_wep_exit(void)
 286 {
 287         ieee80211_unregister_crypto_ops(&ieee80211_crypt_wep);
 288 }
 289
 290 void ieee80211_wep_null(void)
 291 {
 292 //      printk("============>%s()\n", __func__);
 293         return;
 294 }