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/config.h>
13 #include <linux/version.h>
14 #include <linux/module.h>
15 #include <linux/init.h>
16 #include <linux/slab.h>
17 #include <linux/random.h>
18 #include <linux/skbuff.h>
19 #include <asm/string.h>
21 #include "ieee80211.h"
23 #include <linux/crypto.h>
24 #include <linux/scatterlist.h>
25 #include <linux/crc32.h>
27 MODULE_AUTHOR("Jouni Malinen");
28 MODULE_DESCRIPTION("Host AP crypt: WEP");
29 MODULE_LICENSE("GPL");
33 struct prism2_wep_data {
35 #define WEP_KEY_LEN 13
36 u8 key[WEP_KEY_LEN + 1];
39 struct crypto_blkcipher *tx_tfm;
40 struct crypto_blkcipher *rx_tfm;
44 static void * prism2_wep_init(int keyidx)
46 struct prism2_wep_data *priv;
48 priv = kzalloc(sizeof(*priv), GFP_ATOMIC);
51 priv->key_idx = keyidx;
52 priv->tx_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0, CRYPTO_ALG_ASYNC);
53 if (IS_ERR(priv->tx_tfm)) {
54 printk(KERN_DEBUG "ieee80211_crypt_wep: could not allocate "
59 priv->rx_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0, CRYPTO_ALG_ASYNC);
60 if (IS_ERR(priv->rx_tfm)) {
61 printk(KERN_DEBUG "ieee80211_crypt_wep: could not allocate "
67 /* start WEP IV from a random value */
68 get_random_bytes(&priv->iv, 4);
75 crypto_free_blkcipher(priv->tx_tfm);
77 crypto_free_blkcipher(priv->rx_tfm);
85 static void prism2_wep_deinit(void *priv)
87 struct prism2_wep_data *_priv = priv;
91 crypto_free_blkcipher(_priv->tx_tfm);
93 crypto_free_blkcipher(_priv->rx_tfm);
100 /* Perform WEP encryption on given skb that has at least 4 bytes of headroom
101 * for IV and 4 bytes of tailroom for ICV. Both IV and ICV will be transmitted,
102 * so the payload length increases with 8 bytes.
104 * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data))
106 static int prism2_wep_encrypt(struct sk_buff *skb, int hdr_len, void *priv)
108 struct prism2_wep_data *wep = priv;
109 struct blkcipher_desc desc = { .tfm = wep->tx_tfm };
111 u8 key[WEP_KEY_LEN + 3];
115 struct scatterlist sg;
117 if (skb_headroom(skb) < 4 || skb_tailroom(skb) < 4 ||
121 len = skb->len - hdr_len;
122 pos = skb_push(skb, 4);
123 memmove(pos, pos + 4, hdr_len);
126 klen = 3 + wep->key_len;
130 /* Fluhrer, Mantin, and Shamir have reported weaknesses in the key
131 * scheduling algorithm of RC4. At least IVs (KeyByte + 3, 0xff, N)
132 * can be used to speedup attacks, so avoid using them. */
133 if ((wep->iv & 0xff00) == 0xff00) {
134 u8 B = (wep->iv >> 16) & 0xff;
135 if (B >= 3 && B < klen)
139 /* Prepend 24-bit IV to RC4 key and TX frame */
140 *pos++ = key[0] = (wep->iv >> 16) & 0xff;
141 *pos++ = key[1] = (wep->iv >> 8) & 0xff;
142 *pos++ = key[2] = wep->iv & 0xff;
143 *pos++ = wep->key_idx << 6;
145 /* Copy rest of the WEP key (the secret part) */
146 memcpy(key + 3, wep->key, wep->key_len);
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);
163 /* Perform WEP decryption on given buffer. Buffer includes whole WEP part of
164 * the frame: IV (4 bytes), encrypted payload (including SNAP header),
165 * ICV (4 bytes). len includes both IV and ICV.
167 * Returns 0 if frame was decrypted successfully and ICV was correct and -1 on
168 * failure. If frame is OK, IV and ICV will be removed.
170 static int prism2_wep_decrypt(struct sk_buff *skb, int hdr_len, void *priv)
172 struct prism2_wep_data *wep = priv;
173 struct blkcipher_desc desc = { .tfm = wep->rx_tfm };
175 u8 key[WEP_KEY_LEN + 3];
179 struct scatterlist sg;
181 if (skb->len < hdr_len + 8)
184 pos = skb->data + hdr_len;
188 keyidx = *pos++ >> 6;
189 if (keyidx != wep->key_idx)
192 klen = 3 + wep->key_len;
194 /* Copy rest of the WEP key (the secret part) */
195 memcpy(key + 3, wep->key, wep->key_len);
197 /* Apply RC4 to data and compute CRC32 over decrypted data */
198 plen = skb->len - hdr_len - 8;
200 crypto_blkcipher_setkey(wep->rx_tfm, key, klen);
201 sg_init_one(&sg, pos, plen + 4);
203 if (crypto_blkcipher_decrypt(&desc, &sg, &sg, plen + 4))
206 crc = ~crc32_le(~0, pos, plen);
212 if (memcmp(icv, pos + plen, 4) != 0) {
213 /* ICV mismatch - drop frame */
217 /* Remove IV and ICV */
218 memmove(skb->data + 4, skb->data, hdr_len);
220 skb_trim(skb, skb->len - 4);
225 static int prism2_wep_set_key(void *key, int len, u8 *seq, void *priv)
227 struct prism2_wep_data *wep = priv;
229 if (len < 0 || len > WEP_KEY_LEN)
232 memcpy(wep->key, key, len);
239 static int prism2_wep_get_key(void *key, int len, u8 *seq, void *priv)
241 struct prism2_wep_data *wep = priv;
243 if (len < wep->key_len)
246 memcpy(key, wep->key, wep->key_len);
252 static char * prism2_wep_print_stats(char *p, void *priv)
254 struct prism2_wep_data *wep = priv;
255 p += sprintf(p, "key[%d] alg=WEP len=%d\n",
256 wep->key_idx, wep->key_len);
261 static struct ieee80211_crypto_ops ieee80211_crypt_wep = {
263 .init = prism2_wep_init,
264 .deinit = prism2_wep_deinit,
265 .encrypt_mpdu = prism2_wep_encrypt,
266 .decrypt_mpdu = prism2_wep_decrypt,
267 .encrypt_msdu = NULL,
268 .decrypt_msdu = NULL,
269 .set_key = prism2_wep_set_key,
270 .get_key = prism2_wep_get_key,
271 .print_stats = prism2_wep_print_stats,
272 .extra_prefix_len = 4, /* IV */
273 .extra_postfix_len = 4, /* ICV */
274 .owner = THIS_MODULE,
278 int ieee80211_crypto_wep_init(void)
280 return ieee80211_register_crypto_ops(&ieee80211_crypt_wep);
284 void ieee80211_crypto_wep_exit(void)
286 ieee80211_unregister_crypto_ops(&ieee80211_crypt_wep);
290 void ieee80211_wep_null(void)
292 // printk("============>%s()\n", __func__);