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 <crypto/skcipher.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 <linux/string.h>
  19 #include "rtllib.h"
  20
  21 #include <linux/scatterlist.h>
  22 #include <linux/crc32.h>
  23
  24 struct prism2_wep_data {
  25         u32 iv;
  26 #define WEP_KEY_LEN 13
  27         u8 key[WEP_KEY_LEN + 1];
  28         u8 key_len;
  29         u8 key_idx;
  30         struct crypto_skcipher *tx_tfm;
  31         struct crypto_skcipher *rx_tfm;
  32 };
  33
  34
  35 static void *prism2_wep_init(int keyidx)
  36 {
  37         struct prism2_wep_data *priv;
  38
  39         priv = kzalloc(sizeof(*priv), GFP_ATOMIC);
  40         if (priv == NULL)
  41                 goto fail;
  42         priv->key_idx = keyidx;
  43
  44         priv->tx_tfm = crypto_alloc_skcipher("ecb(arc4)", 0, CRYPTO_ALG_ASYNC);
  45         if (IS_ERR(priv->tx_tfm)) {
  46                 pr_debug("rtllib_crypt_wep: could not allocate crypto API arc4\n");
  47                 priv->tx_tfm = NULL;
  48                 goto fail;
  49         }
  50         priv->rx_tfm = crypto_alloc_skcipher("ecb(arc4)", 0, CRYPTO_ALG_ASYNC);
  51         if (IS_ERR(priv->rx_tfm)) {
  52                 pr_debug("rtllib_crypt_wep: could not allocate crypto API arc4\n");
  53                 priv->rx_tfm = NULL;
  54                 goto fail;
  55         }
  56
  57         /* start WEP IV from a random value */
  58         get_random_bytes(&priv->iv, 4);
  59
  60         return priv;
  61
  62 fail:
  63         if (priv) {
  64                 crypto_free_skcipher(priv->tx_tfm);
  65                 crypto_free_skcipher(priv->rx_tfm);
  66                 kfree(priv);
  67         }
  68         return NULL;
  69 }
  70
  71
  72 static void prism2_wep_deinit(void *priv)
  73 {
  74         struct prism2_wep_data *_priv = priv;
  75
  76         if (_priv) {
  77                 crypto_free_skcipher(_priv->tx_tfm);
  78                 crypto_free_skcipher(_priv->rx_tfm);
  79         }
  80         kfree(priv);
  81 }
  82
  83 /* Perform WEP encryption on given skb that has at least 4 bytes of headroom
  84  * for IV and 4 bytes of tailroom for ICV. Both IV and ICV will be transmitted,
  85  * so the payload length increases with 8 bytes.
  86  *
  87  * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data))
  88  */
  89 static int prism2_wep_encrypt(struct sk_buff *skb, int hdr_len, void *priv)
  90 {
  91         struct prism2_wep_data *wep = priv;
  92         u32 klen, len;
  93         u8 key[WEP_KEY_LEN + 3];
  94         u8 *pos;
  95         struct cb_desc *tcb_desc = (struct cb_desc *)(skb->cb +
  96                                     MAX_DEV_ADDR_SIZE);
  97         u32 crc;
  98         u8 *icv;
  99         struct scatterlist sg;
 100         int err;
 101
 102         if (skb_headroom(skb) < 4 || skb_tailroom(skb) < 4 ||
 103             skb->len < hdr_len){
 104                 pr_err("Error!!! headroom=%d tailroom=%d skblen=%d hdr_len=%d\n",
 105                        skb_headroom(skb), skb_tailroom(skb), skb->len, hdr_len);
 106                 return -1;
 107         }
 108         len = skb->len - hdr_len;
 109         pos = skb_push(skb, 4);
 110         memmove(pos, pos + 4, hdr_len);
 111         pos += hdr_len;
 112
 113         klen = 3 + wep->key_len;
 114
 115         wep->iv++;
 116
 117         /* Fluhrer, Mantin, and Shamir have reported weaknesses in the key
 118          * scheduling algorithm of RC4. At least IVs (KeyByte + 3, 0xff, N)
 119          * can be used to speedup attacks, so avoid using them.
 120          */
 121         if ((wep->iv & 0xff00) == 0xff00) {
 122                 u8 B = (wep->iv >> 16) & 0xff;
 123
 124                 if (B >= 3 && B < klen)
 125                         wep->iv += 0x0100;
 126         }
 127
 128         /* Prepend 24-bit IV to RC4 key and TX frame */
 129         *pos++ = key[0] = (wep->iv >> 16) & 0xff;
 130         *pos++ = key[1] = (wep->iv >> 8) & 0xff;
 131         *pos++ = key[2] = wep->iv & 0xff;
 132         *pos++ = wep->key_idx << 6;
 133
 134         /* Copy rest of the WEP key (the secret part) */
 135         memcpy(key + 3, wep->key, wep->key_len);
 136
 137         if (!tcb_desc->bHwSec) {
 138                 SKCIPHER_REQUEST_ON_STACK(req, wep->tx_tfm);
 139
 140                 /* Append little-endian CRC32 and encrypt it to produce ICV */
 141                 crc = ~crc32_le(~0, pos, len);
 142                 icv = skb_put(skb, 4);
 143                 icv[0] = crc;
 144                 icv[1] = crc >> 8;
 145                 icv[2] = crc >> 16;
 146                 icv[3] = crc >> 24;
 147
 148                 sg_init_one(&sg, pos, len+4);
 149                 crypto_skcipher_setkey(wep->tx_tfm, key, klen);
 150                 skcipher_request_set_tfm(req, wep->tx_tfm);
 151                 skcipher_request_set_callback(req, 0, NULL, NULL);
 152                 skcipher_request_set_crypt(req, &sg, &sg, len + 4, NULL);
 153                 err = crypto_skcipher_encrypt(req);
 154                 skcipher_request_zero(req);
 155                 return err;
 156         }
 157
 158         return 0;
 159 }
 160
 161
 162 /* Perform WEP decryption on given struct buffer. Buffer includes whole WEP
 163  * part of the frame: IV (4 bytes), encrypted payload (including SNAP header),
 164  * ICV (4 bytes). len includes both IV and ICV.
 165  *
 166  * Returns 0 if frame was decrypted successfully and ICV was correct and -1 on
 167  * failure. If frame is OK, IV and ICV will be removed.
 168  */
 169 static int prism2_wep_decrypt(struct sk_buff *skb, int hdr_len, void *priv)
 170 {
 171         struct prism2_wep_data *wep = priv;
 172         u32  klen, plen;
 173         u8 key[WEP_KEY_LEN + 3];
 174         u8 keyidx, *pos;
 175         struct cb_desc *tcb_desc = (struct cb_desc *)(skb->cb +
 176                                     MAX_DEV_ADDR_SIZE);
 177         u32 crc;
 178         u8 icv[4];
 179         struct scatterlist sg;
 180         int err;
 181
 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                 SKCIPHER_REQUEST_ON_STACK(req, wep->rx_tfm);
 203
 204                 sg_init_one(&sg, pos, plen+4);
 205                 crypto_skcipher_setkey(wep->rx_tfm, key, klen);
 206                 skcipher_request_set_tfm(req, wep->rx_tfm);
 207                 skcipher_request_set_callback(req, 0, NULL, NULL);
 208                 skcipher_request_set_crypt(req, &sg, &sg, plen + 4, NULL);
 209                 err = crypto_skcipher_decrypt(req);
 210                 skcipher_request_zero(req);
 211                 if (err)
 212                         return -7;
 213                 crc = ~crc32_le(~0, pos, plen);
 214                 icv[0] = crc;
 215                 icv[1] = crc >> 8;
 216                 icv[2] = crc >> 16;
 217                 icv[3] = crc >> 24;
 218                 if (memcmp(icv, pos + plen, 4) != 0) {
 219                         /* ICV mismatch - drop frame */
 220                         return -2;
 221                 }
 222         }
 223         /* Remove IV and ICV */
 224         memmove(skb->data + 4, skb->data, hdr_len);
 225         skb_pull(skb, 4);
 226         skb_trim(skb, skb->len - 4);
 227
 228         return 0;
 229 }
 230
 231
 232 static int prism2_wep_set_key(void *key, int len, u8 *seq, void *priv)
 233 {
 234         struct prism2_wep_data *wep = priv;
 235
 236         if (len < 0 || len > WEP_KEY_LEN)
 237                 return -1;
 238
 239         memcpy(wep->key, key, len);
 240         wep->key_len = len;
 241
 242         return 0;
 243 }
 244
 245
 246 static int prism2_wep_get_key(void *key, int len, u8 *seq, void *priv)
 247 {
 248         struct prism2_wep_data *wep = priv;
 249
 250         if (len < wep->key_len)
 251                 return -1;
 252
 253         memcpy(key, wep->key, wep->key_len);
 254
 255         return wep->key_len;
 256 }
 257
 258
 259 static void prism2_wep_print_stats(struct seq_file *m, void *priv)
 260 {
 261         struct prism2_wep_data *wep = priv;
 262
 263         seq_printf(m, "key[%d] alg=WEP len=%d\n", wep->key_idx, wep->key_len);
 264 }
 265
 266 static struct lib80211_crypto_ops rtllib_crypt_wep = {
 267         .name                   = "R-WEP",
 268         .init                   = prism2_wep_init,
 269         .deinit                 = prism2_wep_deinit,
 270         .encrypt_mpdu           = prism2_wep_encrypt,
 271         .decrypt_mpdu           = prism2_wep_decrypt,
 272         .encrypt_msdu           = NULL,
 273         .decrypt_msdu           = NULL,
 274         .set_key                = prism2_wep_set_key,
 275         .get_key                = prism2_wep_get_key,
 276         .print_stats            = prism2_wep_print_stats,
 277         .extra_mpdu_prefix_len  = 4,    /* IV */
 278         .extra_mpdu_postfix_len = 4,    /* ICV */
 279         .owner                  = THIS_MODULE,
 280 };
 281
 282
 283 static int __init rtllib_crypto_wep_init(void)
 284 {
 285         return lib80211_register_crypto_ops(&rtllib_crypt_wep);
 286 }
 287
 288
 289 static void __exit rtllib_crypto_wep_exit(void)
 290 {
 291         lib80211_unregister_crypto_ops(&rtllib_crypt_wep);
 292 }
 293
 294 module_init(rtllib_crypto_wep_init);
 295 module_exit(rtllib_crypto_wep_exit);
 296
 297 MODULE_LICENSE("GPL");