drivers/staging/rtl8192e/rtllib_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 <linux/string.h>
  18 #include "rtllib.h"
  19
  20 #include <linux/crypto.h>
  21
  22 #include <linux/scatterlist.h>
  23 #include <linux/crc32.h>
  24
  25 struct prism2_wep_data {
  26         u32 iv;
  27 #define WEP_KEY_LEN 13
  28         u8 key[WEP_KEY_LEN + 1];
  29         u8 key_len;
  30         u8 key_idx;
  31         struct crypto_blkcipher *tx_tfm;
  32         struct crypto_blkcipher *rx_tfm;
  33 };
  34
  35
  36 static void *prism2_wep_init(int keyidx)
  37 {
  38         struct prism2_wep_data *priv;
  39
  40         priv = kzalloc(sizeof(*priv), GFP_ATOMIC);
  41         if (priv == NULL)
  42                 goto fail;
  43         priv->key_idx = keyidx;
  44
  45         priv->tx_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0, CRYPTO_ALG_ASYNC);
  46         if (IS_ERR(priv->tx_tfm)) {
  47                 printk(KERN_DEBUG "rtllib_crypt_wep: could not allocate "
  48                        "crypto API arc4\n");
  49                 priv->tx_tfm = NULL;
  50                 goto fail;
  51         }
  52         priv->rx_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0, CRYPTO_ALG_ASYNC);
  53         if (IS_ERR(priv->rx_tfm)) {
  54                 printk(KERN_DEBUG "rtllib_crypt_wep: could not allocate "
  55                        "crypto API arc4\n");
  56                 priv->rx_tfm = NULL;
  57                 goto fail;
  58         }
  59
  60         /* start WEP IV from a random value */
  61         get_random_bytes(&priv->iv, 4);
  62
  63         return priv;
  64
  65 fail:
  66         if (priv) {
  67                 if (priv->tx_tfm)
  68                         crypto_free_blkcipher(priv->tx_tfm);
  69                 if (priv->rx_tfm)
  70                         crypto_free_blkcipher(priv->rx_tfm);
  71                 kfree(priv);
  72         }
  73         return NULL;
  74 }
  75
  76
  77 static void prism2_wep_deinit(void *priv)
  78 {
  79         struct prism2_wep_data *_priv = priv;
  80
  81         if (_priv) {
  82                 if (_priv->tx_tfm)
  83                         crypto_free_blkcipher(_priv->tx_tfm);
  84                 if (_priv->rx_tfm)
  85                         crypto_free_blkcipher(_priv->rx_tfm);
  86         }
  87         kfree(priv);
  88 }
  89
  90 /* Perform WEP encryption on given skb that has at least 4 bytes of headroom
  91  * for IV and 4 bytes of tailroom for ICV. Both IV and ICV will be transmitted,
  92  * so the payload length increases with 8 bytes.
  93  *
  94  * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data))
  95  */
  96 static int prism2_wep_encrypt(struct sk_buff *skb, int hdr_len, void *priv)
  97 {
  98         struct prism2_wep_data *wep = priv;
  99         u32 klen, len;
 100         u8 key[WEP_KEY_LEN + 3];
 101         u8 *pos;
 102         struct cb_desc *tcb_desc = (struct cb_desc *)(skb->cb +
 103                                     MAX_DEV_ADDR_SIZE);
 104         struct blkcipher_desc desc = {.tfm = wep->tx_tfm};
 105         u32 crc;
 106         u8 *icv;
 107         struct scatterlist sg;
 108         if (skb_headroom(skb) < 4 || skb_tailroom(skb) < 4 ||
 109             skb->len < hdr_len){
 110                 printk(KERN_ERR "Error!!! headroom=%d tailroom=%d skblen=%d"
 111                        " hdr_len=%d\n", skb_headroom(skb), skb_tailroom(skb),
 112                        skb->len, hdr_len);
 113                 return -1;
 114         }
 115         len = skb->len - hdr_len;
 116         pos = skb_push(skb, 4);
 117         memmove(pos, pos + 4, hdr_len);
 118         pos += hdr_len;
 119
 120         klen = 3 + wep->key_len;
 121
 122         wep->iv++;
 123
 124         /* Fluhrer, Mantin, and Shamir have reported weaknesses in the key
 125          * scheduling algorithm of RC4. At least IVs (KeyByte + 3, 0xff, N)
 126          * can be used to speedup attacks, so avoid using them. */
 127         if ((wep->iv & 0xff00) == 0xff00) {
 128                 u8 B = (wep->iv >> 16) & 0xff;
 129                 if (B >= 3 && B < klen)
 130                         wep->iv += 0x0100;
 131         }
 132
 133         /* Prepend 24-bit IV to RC4 key and TX frame */
 134         *pos++ = key[0] = (wep->iv >> 16) & 0xff;
 135         *pos++ = key[1] = (wep->iv >> 8) & 0xff;
 136         *pos++ = key[2] = wep->iv & 0xff;
 137         *pos++ = wep->key_idx << 6;
 138
 139         /* Copy rest of the WEP key (the secret part) */
 140         memcpy(key + 3, wep->key, wep->key_len);
 141
 142         if (!tcb_desc->bHwSec) {
 143
 144                 /* Append little-endian CRC32 and encrypt it to produce ICV */
 145                 crc = ~crc32_le(~0, pos, len);
 146                 icv = skb_put(skb, 4);
 147                 icv[0] = crc;
 148                 icv[1] = crc >> 8;
 149                 icv[2] = crc >> 16;
 150                 icv[3] = crc >> 24;
 151
 152                 sg_init_one(&sg, pos, len+4);
 153                 crypto_blkcipher_setkey(wep->tx_tfm, key, klen);
 154                 return crypto_blkcipher_encrypt(&desc, &sg, &sg, len + 4);
 155         }
 156
 157         return 0;
 158 }
 159
 160
 161 /* Perform WEP decryption on given struct buffer. Buffer includes whole WEP
 162  * part of 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         u32  klen, plen;
 172         u8 key[WEP_KEY_LEN + 3];
 173         u8 keyidx, *pos;
 174         struct cb_desc *tcb_desc = (struct cb_desc *)(skb->cb +
 175                                     MAX_DEV_ADDR_SIZE);
 176         struct blkcipher_desc desc = {.tfm = wep->rx_tfm};
 177         u32 crc;
 178         u8 icv[4];
 179         struct scatterlist sg;
 180         if (skb->len < hdr_len + 8)
 181                 return -1;
 182
 183         pos = skb->data + hdr_len;
 184         key[0] = *pos++;
 185         key[1] = *pos++;
 186         key[2] = *pos++;
 187         keyidx = *pos++ >> 6;
 188         if (keyidx != wep->key_idx)
 189                 return -1;
 190
 191         klen = 3 + wep->key_len;
 192
 193         /* Copy rest of the WEP key (the secret part) */
 194         memcpy(key + 3, wep->key, wep->key_len);
 195
 196         /* Apply RC4 to data and compute CRC32 over decrypted data */
 197         plen = skb->len - hdr_len - 8;
 198
 199         if (!tcb_desc->bHwSec) {
 200                 sg_init_one(&sg, pos, plen+4);
 201                 crypto_blkcipher_setkey(wep->rx_tfm, key, klen);
 202                 if (crypto_blkcipher_decrypt(&desc, &sg, &sg, plen + 4))
 203                         return -7;
 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                 if (memcmp(icv, pos + plen, 4) != 0) {
 210                         /* ICV mismatch - drop frame */
 211                         return -2;
 212                 }
 213         }
 214         /* Remove IV and ICV */
 215         memmove(skb->data + 4, skb->data, hdr_len);
 216         skb_pull(skb, 4);
 217         skb_trim(skb, skb->len - 4);
 218
 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 static struct lib80211_crypto_ops rtllib_crypt_wep = {
 259         .name                   = "R-WEP",
 260         .init                   = prism2_wep_init,
 261         .deinit                 = prism2_wep_deinit,
 262         .encrypt_mpdu           = prism2_wep_encrypt,
 263         .decrypt_mpdu           = prism2_wep_decrypt,
 264         .encrypt_msdu           = NULL,
 265         .decrypt_msdu           = NULL,
 266         .set_key                = prism2_wep_set_key,
 267         .get_key                = prism2_wep_get_key,
 268         .print_stats            = prism2_wep_print_stats,
 269         .extra_mpdu_prefix_len  = 4,    /* IV */
 270         .extra_mpdu_postfix_len = 4,    /* ICV */
 271         .owner                  = THIS_MODULE,
 272 };
 273
 274
 275 int __init rtllib_crypto_wep_init(void)
 276 {
 277         return lib80211_register_crypto_ops(&rtllib_crypt_wep);
 278 }
 279
 280
 281 void __exit rtllib_crypto_wep_exit(void)
 282 {
 283         lib80211_unregister_crypto_ops(&rtllib_crypt_wep);
 284 }
 285
 286 module_init(rtllib_crypto_wep_init);
 287 module_exit(rtllib_crypto_wep_exit);
 288
 289 MODULE_LICENSE("GPL");