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 = kmalloc(sizeof(*priv), GFP_ATOMIC);
51 memset(priv, 0, sizeof(*priv));
52 priv->key_idx = keyidx;
53 priv->tx_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0, CRYPTO_ALG_ASYNC);
54 if (IS_ERR(priv->tx_tfm)) {
55 printk(KERN_DEBUG "ieee80211_crypt_wep: could not allocate "
60 priv->rx_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0, CRYPTO_ALG_ASYNC);
61 if (IS_ERR(priv->rx_tfm)) {
62 printk(KERN_DEBUG "ieee80211_crypt_wep: could not allocate "
68 /* start WEP IV from a random value */
69 get_random_bytes(&priv->iv, 4);
76 crypto_free_blkcipher(priv->tx_tfm);
78 crypto_free_blkcipher(priv->rx_tfm);
86 static void prism2_wep_deinit(void *priv)
88 struct prism2_wep_data *_priv = priv;
92 crypto_free_blkcipher(_priv->tx_tfm);
94 crypto_free_blkcipher(_priv->rx_tfm);
101 /* Perform WEP encryption on given skb that has at least 4 bytes of headroom
102 * for IV and 4 bytes of tailroom for ICV. Both IV and ICV will be transmitted,
103 * so the payload length increases with 8 bytes.
105 * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data))
107 static int prism2_wep_encrypt(struct sk_buff *skb, int hdr_len, void *priv)
109 struct prism2_wep_data *wep = priv;
110 struct blkcipher_desc desc = { .tfm = wep->tx_tfm };
112 u8 key[WEP_KEY_LEN + 3];
116 struct scatterlist sg;
118 if (skb_headroom(skb) < 4 || skb_tailroom(skb) < 4 ||
122 len = skb->len - hdr_len;
123 pos = skb_push(skb, 4);
124 memmove(pos, pos + 4, hdr_len);
127 klen = 3 + wep->key_len;
131 /* Fluhrer, Mantin, and Shamir have reported weaknesses in the key
132 * scheduling algorithm of RC4. At least IVs (KeyByte + 3, 0xff, N)
133 * can be used to speedup attacks, so avoid using them. */
134 if ((wep->iv & 0xff00) == 0xff00) {
135 u8 B = (wep->iv >> 16) & 0xff;
136 if (B >= 3 && B < klen)
140 /* Prepend 24-bit IV to RC4 key and TX frame */
141 *pos++ = key[0] = (wep->iv >> 16) & 0xff;
142 *pos++ = key[1] = (wep->iv >> 8) & 0xff;
143 *pos++ = key[2] = wep->iv & 0xff;
144 *pos++ = wep->key_idx << 6;
146 /* Copy rest of the WEP key (the secret part) */
147 memcpy(key + 3, wep->key, wep->key_len);
149 /* Append little-endian CRC32 and encrypt it to produce ICV */
150 crc = ~crc32_le(~0, pos, len);
151 icv = skb_put(skb, 4);
157 crypto_blkcipher_setkey(wep->tx_tfm, key, klen);
158 sg_init_one(&sg, pos, len + 4);
160 return crypto_blkcipher_encrypt(&desc, &sg, &sg, len + 4);
164 /* Perform WEP decryption on given buffer. Buffer includes whole WEP part of
165 * the frame: IV (4 bytes), encrypted payload (including SNAP header),
166 * ICV (4 bytes). len includes both IV and ICV.
168 * Returns 0 if frame was decrypted successfully and ICV was correct and -1 on
169 * failure. If frame is OK, IV and ICV will be removed.
171 static int prism2_wep_decrypt(struct sk_buff *skb, int hdr_len, void *priv)
173 struct prism2_wep_data *wep = priv;
174 struct blkcipher_desc desc = { .tfm = wep->rx_tfm };
176 u8 key[WEP_KEY_LEN + 3];
180 struct scatterlist sg;
182 if (skb->len < hdr_len + 8)
185 pos = skb->data + hdr_len;
189 keyidx = *pos++ >> 6;
190 if (keyidx != wep->key_idx)
193 klen = 3 + wep->key_len;
195 /* Copy rest of the WEP key (the secret part) */
196 memcpy(key + 3, wep->key, wep->key_len);
198 /* Apply RC4 to data and compute CRC32 over decrypted data */
199 plen = skb->len - hdr_len - 8;
201 crypto_blkcipher_setkey(wep->rx_tfm, key, klen);
202 sg_init_one(&sg, pos, plen + 4);
204 if (crypto_blkcipher_decrypt(&desc, &sg, &sg, plen + 4))
207 crc = ~crc32_le(~0, pos, plen);
213 if (memcmp(icv, pos + plen, 4) != 0) {
214 /* ICV mismatch - drop frame */
218 /* Remove IV and ICV */
219 memmove(skb->data + 4, skb->data, hdr_len);
221 skb_trim(skb, skb->len - 4);
226 static int prism2_wep_set_key(void *key, int len, u8 *seq, void *priv)
228 struct prism2_wep_data *wep = priv;
230 if (len < 0 || len > WEP_KEY_LEN)
233 memcpy(wep->key, key, len);
240 static int prism2_wep_get_key(void *key, int len, u8 *seq, void *priv)
242 struct prism2_wep_data *wep = priv;
244 if (len < wep->key_len)
247 memcpy(key, wep->key, wep->key_len);
253 static char * prism2_wep_print_stats(char *p, void *priv)
255 struct prism2_wep_data *wep = priv;
256 p += sprintf(p, "key[%d] alg=WEP len=%d\n",
257 wep->key_idx, wep->key_len);
262 static struct ieee80211_crypto_ops ieee80211_crypt_wep = {
264 .init = prism2_wep_init,
265 .deinit = prism2_wep_deinit,
266 .encrypt_mpdu = prism2_wep_encrypt,
267 .decrypt_mpdu = prism2_wep_decrypt,
268 .encrypt_msdu = NULL,
269 .decrypt_msdu = NULL,
270 .set_key = prism2_wep_set_key,
271 .get_key = prism2_wep_get_key,
272 .print_stats = prism2_wep_print_stats,
273 .extra_prefix_len = 4, /* IV */
274 .extra_postfix_len = 4, /* ICV */
275 .owner = THIS_MODULE,
279 int ieee80211_crypto_wep_init(void)
281 return ieee80211_register_crypto_ops(&ieee80211_crypt_wep);
285 void ieee80211_crypto_wep_exit(void)
287 ieee80211_unregister_crypto_ops(&ieee80211_crypt_wep);
291 void ieee80211_wep_null(void)
293 // printk("============>%s()\n", __func__);