drivers/staging/rtl8192e/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/version.h>
  13 #include <linux/module.h>
  14 #include <linux/init.h>
  15 #include <linux/slab.h>
  16 #include <linux/random.h>
  17 #include <linux/skbuff.h>
  18 #include <asm/string.h>
  19
  20 #include "ieee80211.h"
  21
  22
  23 #include <linux/crypto.h>
  24
  25 #include <linux/scatterlist.h>
  26 #include <linux/crc32.h>
  27
  28 MODULE_AUTHOR("Jouni Malinen");
  29 MODULE_DESCRIPTION("Host AP crypt: WEP");
  30 MODULE_LICENSE("GPL");
  31 #ifndef OPENSUSE_SLED
  32 #define OPENSUSE_SLED 0
  33 #endif
  34
  35 struct prism2_wep_data {
  36         u32 iv;
  37 #define WEP_KEY_LEN 13
  38         u8 key[WEP_KEY_LEN + 1];
  39         u8 key_len;
  40         u8 key_idx;
  41         struct crypto_blkcipher *tx_tfm;
  42         struct crypto_blkcipher *rx_tfm;
  43 };
  44
  45
  46 static void * prism2_wep_init(int keyidx)
  47 {
  48         struct prism2_wep_data *priv;
  49
  50         priv = kzalloc(sizeof(*priv), GFP_ATOMIC);
  51         if (priv == NULL)
  52                 goto fail;
  53         priv->key_idx = keyidx;
  54
  55         priv->tx_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0, CRYPTO_ALG_ASYNC);
  56         if (IS_ERR(priv->tx_tfm)) {
  57                 printk(KERN_DEBUG "ieee80211_crypt_wep: could not allocate "
  58                        "crypto API arc4\n");
  59                 priv->tx_tfm = NULL;
  60                 goto fail;
  61         }
  62         priv->rx_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0, CRYPTO_ALG_ASYNC);
  63         if (IS_ERR(priv->rx_tfm)) {
  64                 printk(KERN_DEBUG "ieee80211_crypt_wep: could not allocate "
  65                        "crypto API arc4\n");
  66                 priv->rx_tfm = NULL;
  67                 goto fail;
  68         }
  69
  70         /* start WEP IV from a random value */
  71         get_random_bytes(&priv->iv, 4);
  72
  73         return priv;
  74
  75 fail:
  76         if (priv) {
  77                 if (priv->tx_tfm)
  78                         crypto_free_blkcipher(priv->tx_tfm);
  79                 if (priv->rx_tfm)
  80                         crypto_free_blkcipher(priv->rx_tfm);
  81                 kfree(priv);
  82         }
  83         return NULL;
  84 }
  85
  86
  87 static void prism2_wep_deinit(void *priv)
  88 {
  89         struct prism2_wep_data *_priv = priv;
  90         if (_priv) {
  91                 if (_priv->tx_tfm)
  92                         crypto_free_blkcipher(_priv->tx_tfm);
  93                 if (_priv->rx_tfm)
  94                         crypto_free_blkcipher(_priv->rx_tfm);
  95         }
  96         kfree(priv);
  97 }
  98
  99 /* Perform WEP encryption on given skb that has at least 4 bytes of headroom
 100  * for IV and 4 bytes of tailroom for ICV. Both IV and ICV will be transmitted,
 101  * so the payload length increases with 8 bytes.
 102  *
 103  * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data))
 104  */
 105 static int prism2_wep_encrypt(struct sk_buff *skb, int hdr_len, void *priv)
 106 {
 107         struct prism2_wep_data *wep = priv;
 108         u32 klen, len;
 109         u8 key[WEP_KEY_LEN + 3];
 110         u8 *pos;
 111         cb_desc *tcb_desc = (cb_desc *)(skb->cb + MAX_DEV_ADDR_SIZE);
 112         struct blkcipher_desc desc = {.tfm = wep->tx_tfm};
 113         u32 crc;
 114         u8 *icv;
 115         struct scatterlist sg;
 116         if (skb_headroom(skb) < 4 || skb_tailroom(skb) < 4 ||
 117             skb->len < hdr_len)
 118                 return -1;
 119
 120         len = skb->len - hdr_len;
 121         pos = skb_push(skb, 4);
 122         memmove(pos, pos + 4, hdr_len);
 123         pos += hdr_len;
 124
 125         klen = 3 + wep->key_len;
 126
 127         wep->iv++;
 128
 129         /* Fluhrer, Mantin, and Shamir have reported weaknesses in the key
 130          * scheduling algorithm of RC4. At least IVs (KeyByte + 3, 0xff, N)
 131          * can be used to speedup attacks, so avoid using them. */
 132         if ((wep->iv & 0xff00) == 0xff00) {
 133                 u8 B = (wep->iv >> 16) & 0xff;
 134                 if (B >= 3 && B < klen)
 135                         wep->iv += 0x0100;
 136         }
 137
 138         /* Prepend 24-bit IV to RC4 key and TX frame */
 139         *pos++ = key[0] = (wep->iv >> 16) & 0xff;
 140         *pos++ = key[1] = (wep->iv >> 8) & 0xff;
 141         *pos++ = key[2] = wep->iv & 0xff;
 142         *pos++ = wep->key_idx << 6;
 143
 144         /* Copy rest of the WEP key (the secret part) */
 145         memcpy(key + 3, wep->key, wep->key_len);
 146
 147         if (!tcb_desc->bHwSec)
 148         {
 149
 150                 /* Append little-endian CRC32 and encrypt it to produce ICV */
 151                 crc = ~crc32_le(~0, pos, len);
 152                 icv = skb_put(skb, 4);
 153                 icv[0] = crc;
 154                 icv[1] = crc >> 8;
 155                 icv[2] = crc >> 16;
 156                 icv[3] = crc >> 24;
 157
 158                 crypto_blkcipher_setkey(wep->tx_tfm, key, klen);
 159                 sg_init_one(&sg, pos, len+4);
 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                 if (crypto_blkcipher_decrypt(&desc, &sg, &sg, plen + 4))
 209                         return -7;
 210                 crc = ~crc32_le(~0, pos, plen);
 211                 icv[0] = crc;
 212                 icv[1] = crc >> 8;
 213                 icv[2] = crc >> 16;
 214                 icv[3] = crc >> 24;
 215                 if (memcmp(icv, pos + plen, 4) != 0) {
 216                         /* ICV mismatch - drop frame */
 217                         return -2;
 218                 }
 219         }
 220         /* Remove IV and ICV */
 221         memmove(skb->data + 4, skb->data, hdr_len);
 222         skb_pull(skb, 4);
 223         skb_trim(skb, skb->len - 4);
 224
 225         return 0;
 226 }
 227
 228
 229 static int prism2_wep_set_key(void *key, int len, u8 *seq, void *priv)
 230 {
 231         struct prism2_wep_data *wep = priv;
 232
 233         if (len < 0 || len > WEP_KEY_LEN)
 234                 return -1;
 235
 236         memcpy(wep->key, key, len);
 237         wep->key_len = len;
 238
 239         return 0;
 240 }
 241
 242
 243 static int prism2_wep_get_key(void *key, int len, u8 *seq, void *priv)
 244 {
 245         struct prism2_wep_data *wep = priv;
 246
 247         if (len < wep->key_len)
 248                 return -1;
 249
 250         memcpy(key, wep->key, wep->key_len);
 251
 252         return wep->key_len;
 253 }
 254
 255
 256 static char * prism2_wep_print_stats(char *p, void *priv)
 257 {
 258         struct prism2_wep_data *wep = priv;
 259         p += sprintf(p, "key[%d] alg=WEP len=%d\n",
 260                      wep->key_idx, wep->key_len);
 261         return p;
 262 }
 263
 264
 265 static struct ieee80211_crypto_ops ieee80211_crypt_wep = {
 266         .name                   = "WEP",
 267         .init                   = prism2_wep_init,
 268         .deinit                 = prism2_wep_deinit,
 269         .encrypt_mpdu           = prism2_wep_encrypt,
 270         .decrypt_mpdu           = prism2_wep_decrypt,
 271         .encrypt_msdu           = NULL,
 272         .decrypt_msdu           = NULL,
 273         .set_key                = prism2_wep_set_key,
 274         .get_key                = prism2_wep_get_key,
 275         .print_stats            = prism2_wep_print_stats,
 276         .extra_prefix_len       = 4, /* IV */
 277         .extra_postfix_len      = 4, /* ICV */
 278         .owner                  = THIS_MODULE,
 279 };
 280
 281
 282 int __init ieee80211_crypto_wep_init(void)
 283 {
 284         return ieee80211_register_crypto_ops(&ieee80211_crypt_wep);
 285 }
 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         return;
 296 }
 297