2 * Host AP crypt: host-based WEP encryption implementation for Host AP driver
4 * Copyright (c) 2002-2004, Jouni Malinen <jkmaline@cc.hut.fi>
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
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>
19 #include "ieee80211.h"
21 #include <linux/crypto.h>
22 #include <linux/scatterlist.h>
23 #include <linux/crc32.h>
25 MODULE_AUTHOR("Jouni Malinen");
26 MODULE_DESCRIPTION("Host AP crypt: WEP");
27 MODULE_LICENSE("GPL");
29 struct prism2_wep_data {
31 #define WEP_KEY_LEN 13
32 u8 key[WEP_KEY_LEN + 1];
35 struct crypto_blkcipher *tx_tfm;
36 struct crypto_blkcipher *rx_tfm;
40 static void *prism2_wep_init(int keyidx)
42 struct prism2_wep_data *priv;
44 priv = kzalloc(sizeof(*priv), GFP_ATOMIC);
47 priv->key_idx = keyidx;
49 priv->tx_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0, CRYPTO_ALG_ASYNC);
50 if (IS_ERR(priv->tx_tfm)) {
51 pr_debug("ieee80211_crypt_wep: could not allocate "
56 priv->rx_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0, CRYPTO_ALG_ASYNC);
57 if (IS_ERR(priv->rx_tfm)) {
58 pr_debug("ieee80211_crypt_wep: could not allocate "
64 /* start WEP IV from a random value */
65 get_random_bytes(&priv->iv, 4);
72 crypto_free_blkcipher(priv->tx_tfm);
74 crypto_free_blkcipher(priv->rx_tfm);
82 static void prism2_wep_deinit(void *priv)
84 struct prism2_wep_data *_priv = priv;
88 crypto_free_blkcipher(_priv->tx_tfm);
90 crypto_free_blkcipher(_priv->rx_tfm);
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.
99 * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data))
101 static int prism2_wep_encrypt(struct sk_buff *skb, int hdr_len, void *priv)
103 struct prism2_wep_data *wep = priv;
105 u8 key[WEP_KEY_LEN + 3];
107 cb_desc *tcb_desc = (cb_desc *)(skb->cb + MAX_DEV_ADDR_SIZE);
108 struct blkcipher_desc desc = {.tfm = wep->tx_tfm};
111 struct scatterlist sg;
113 if (skb_headroom(skb) < 4 || skb_tailroom(skb) < 4 ||
117 len = skb->len - hdr_len;
118 pos = skb_push(skb, 4);
119 memmove(pos, pos + 4, hdr_len);
122 klen = 3 + wep->key_len;
126 /* Fluhrer, Mantin, and Shamir have reported weaknesses in the key
127 * scheduling algorithm of RC4. At least IVs (KeyByte + 3, 0xff, N)
128 * can be used to speedup attacks, so avoid using them. */
129 if ((wep->iv & 0xff00) == 0xff00) {
130 u8 B = (wep->iv >> 16) & 0xff;
132 if (B >= 3 && B < klen)
136 /* Prepend 24-bit IV to RC4 key and TX frame */
137 *pos++ = key[0] = (wep->iv >> 16) & 0xff;
138 *pos++ = key[1] = (wep->iv >> 8) & 0xff;
139 *pos++ = key[2] = wep->iv & 0xff;
140 *pos++ = wep->key_idx << 6;
142 /* Copy rest of the WEP key (the secret part) */
143 memcpy(key + 3, wep->key, wep->key_len);
145 if (!tcb_desc->bHwSec)
148 /* Append little-endian CRC32 and encrypt it to produce ICV */
149 crc = ~crc32_le(~0, pos, len);
150 icv = skb_put(skb, 4);
156 crypto_blkcipher_setkey(wep->tx_tfm, key, klen);
157 sg_init_one(&sg, pos, len+4);
159 return crypto_blkcipher_encrypt(&desc, &sg, &sg, len + 4);
166 /* Perform WEP decryption on given buffer. Buffer includes whole WEP part of
167 * the frame: IV (4 bytes), encrypted payload (including SNAP header),
168 * ICV (4 bytes). len includes both IV and ICV.
170 * Returns 0 if frame was decrypted successfully and ICV was correct and -1 on
171 * failure. If frame is OK, IV and ICV will be removed.
173 static int prism2_wep_decrypt(struct sk_buff *skb, int hdr_len, void *priv)
175 struct prism2_wep_data *wep = priv;
177 u8 key[WEP_KEY_LEN + 3];
179 cb_desc *tcb_desc = (cb_desc *)(skb->cb + MAX_DEV_ADDR_SIZE);
180 struct blkcipher_desc desc = {.tfm = wep->rx_tfm};
183 struct scatterlist sg;
185 if (skb->len < hdr_len + 8)
188 pos = skb->data + hdr_len;
192 keyidx = *pos++ >> 6;
193 if (keyidx != wep->key_idx)
196 klen = 3 + wep->key_len;
198 /* Copy rest of the WEP key (the secret part) */
199 memcpy(key + 3, wep->key, wep->key_len);
201 /* Apply RC4 to data and compute CRC32 over decrypted data */
202 plen = skb->len - hdr_len - 8;
204 if (!tcb_desc->bHwSec)
206 crypto_blkcipher_setkey(wep->rx_tfm, key, klen);
207 sg_init_one(&sg, pos, plen+4);
209 if (crypto_blkcipher_decrypt(&desc, &sg, &sg, plen + 4))
212 crc = ~crc32_le(~0, pos, plen);
217 if (memcmp(icv, pos + plen, 4) != 0) {
218 /* ICV mismatch - drop frame */
222 /* Remove IV and ICV */
223 memmove(skb->data + 4, skb->data, hdr_len);
225 skb_trim(skb, skb->len - 4);
231 static int prism2_wep_set_key(void *key, int len, u8 *seq, void *priv)
233 struct prism2_wep_data *wep = priv;
235 if (len < 0 || len > WEP_KEY_LEN)
238 memcpy(wep->key, key, len);
245 static int prism2_wep_get_key(void *key, int len, u8 *seq, void *priv)
247 struct prism2_wep_data *wep = priv;
249 if (len < wep->key_len)
252 memcpy(key, wep->key, wep->key_len);
258 static char *prism2_wep_print_stats(char *p, void *priv)
260 struct prism2_wep_data *wep = priv;
262 p += sprintf(p, "key[%d] alg=WEP len=%d\n",
263 wep->key_idx, wep->key_len);
268 static struct ieee80211_crypto_ops ieee80211_crypt_wep = {
270 .init = prism2_wep_init,
271 .deinit = prism2_wep_deinit,
272 .encrypt_mpdu = prism2_wep_encrypt,
273 .decrypt_mpdu = prism2_wep_decrypt,
274 .encrypt_msdu = NULL,
275 .decrypt_msdu = NULL,
276 .set_key = prism2_wep_set_key,
277 .get_key = prism2_wep_get_key,
278 .print_stats = prism2_wep_print_stats,
279 .extra_prefix_len = 4, /* IV */
280 .extra_postfix_len = 4, /* ICV */
281 .owner = THIS_MODULE,
284 int __init ieee80211_crypto_wep_init(void)
286 return ieee80211_register_crypto_ops(&ieee80211_crypt_wep);
289 void __exit ieee80211_crypto_wep_exit(void)
291 ieee80211_unregister_crypto_ops(&ieee80211_crypt_wep);
294 void ieee80211_wep_null(void)
296 // printk("============>%s()\n", __func__);