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/module.h>
14 #include <linux/init.h>
15 #include <linux/slab.h>
16 #include <linux/random.h>
17 #include <linux/skbuff.h>
18 #include <asm/string.h>
20 #include "ieee80211.h"
22 #include <linux/crypto.h>
23 #include <linux/scatterlist.h>
24 #include <linux/crc32.h>
26 MODULE_AUTHOR("Jouni Malinen");
27 MODULE_DESCRIPTION("Host AP crypt: WEP");
28 MODULE_LICENSE("GPL");
32 struct prism2_wep_data {
34 #define WEP_KEY_LEN 13
35 u8 key[WEP_KEY_LEN + 1];
38 struct crypto_blkcipher *tx_tfm;
39 struct crypto_blkcipher *rx_tfm;
43 static void * prism2_wep_init(int keyidx)
45 struct prism2_wep_data *priv;
47 priv = kzalloc(sizeof(*priv), GFP_ATOMIC);
50 priv->key_idx = keyidx;
51 priv->tx_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0, CRYPTO_ALG_ASYNC);
52 if (IS_ERR(priv->tx_tfm)) {
53 printk(KERN_DEBUG "ieee80211_crypt_wep: could not allocate "
58 priv->rx_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0, CRYPTO_ALG_ASYNC);
59 if (IS_ERR(priv->rx_tfm)) {
60 printk(KERN_DEBUG "ieee80211_crypt_wep: could not allocate "
66 /* start WEP IV from a random value */
67 get_random_bytes(&priv->iv, 4);
74 crypto_free_blkcipher(priv->tx_tfm);
76 crypto_free_blkcipher(priv->rx_tfm);
84 static void prism2_wep_deinit(void *priv)
86 struct prism2_wep_data *_priv = priv;
90 crypto_free_blkcipher(_priv->tx_tfm);
92 crypto_free_blkcipher(_priv->rx_tfm);
99 /* Perform WEP encryption on given skb that has at least 4 bytes of headroom
100 * for IV and 4 bytes of tailroom for ICV. Both IV and ICV will be transmitted,
101 * so the payload length increases with 8 bytes.
103 * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data))
105 static int prism2_wep_encrypt(struct sk_buff *skb, int hdr_len, void *priv)
107 struct prism2_wep_data *wep = priv;
108 struct blkcipher_desc desc = { .tfm = wep->tx_tfm };
110 u8 key[WEP_KEY_LEN + 3];
114 struct scatterlist sg;
116 if (skb_headroom(skb) < 4 || skb_tailroom(skb) < 4 ||
120 len = skb->len - hdr_len;
121 pos = skb_push(skb, 4);
122 memmove(pos, pos + 4, hdr_len);
125 klen = 3 + wep->key_len;
129 /* Fluhrer, Mantin, and Shamir have reported weaknesses in the key
130 * scheduling algorithm of RC4. At least IVs (KeyByte + 3, 0xff, N)
131 * can be used to speedup attacks, so avoid using them. */
132 if ((wep->iv & 0xff00) == 0xff00) {
133 u8 B = (wep->iv >> 16) & 0xff;
134 if (B >= 3 && B < klen)
138 /* Prepend 24-bit IV to RC4 key and TX frame */
139 *pos++ = key[0] = (wep->iv >> 16) & 0xff;
140 *pos++ = key[1] = (wep->iv >> 8) & 0xff;
141 *pos++ = key[2] = wep->iv & 0xff;
142 *pos++ = wep->key_idx << 6;
144 /* Copy rest of the WEP key (the secret part) */
145 memcpy(key + 3, wep->key, wep->key_len);
147 /* Append little-endian CRC32 and encrypt it to produce ICV */
148 crc = ~crc32_le(~0, pos, len);
149 icv = skb_put(skb, 4);
155 crypto_blkcipher_setkey(wep->tx_tfm, key, klen);
156 sg_init_one(&sg, pos, len + 4);
158 return crypto_blkcipher_encrypt(&desc, &sg, &sg, len + 4);
162 /* Perform WEP decryption on given buffer. Buffer includes whole WEP part of
163 * the frame: IV (4 bytes), encrypted payload (including SNAP header),
164 * ICV (4 bytes). len includes both IV and ICV.
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.
169 static int prism2_wep_decrypt(struct sk_buff *skb, int hdr_len, void *priv)
171 struct prism2_wep_data *wep = priv;
172 struct blkcipher_desc desc = { .tfm = wep->rx_tfm };
174 u8 key[WEP_KEY_LEN + 3];
178 struct scatterlist sg;
180 if (skb->len < hdr_len + 8)
183 pos = skb->data + hdr_len;
187 keyidx = *pos++ >> 6;
188 if (keyidx != wep->key_idx)
191 klen = 3 + wep->key_len;
193 /* Copy rest of the WEP key (the secret part) */
194 memcpy(key + 3, wep->key, wep->key_len);
196 /* Apply RC4 to data and compute CRC32 over decrypted data */
197 plen = skb->len - hdr_len - 8;
199 crypto_blkcipher_setkey(wep->rx_tfm, key, klen);
200 sg_init_one(&sg, pos, plen + 4);
202 if (crypto_blkcipher_decrypt(&desc, &sg, &sg, plen + 4))
205 crc = ~crc32_le(~0, pos, plen);
211 if (memcmp(icv, pos + plen, 4) != 0) {
212 /* ICV mismatch - drop frame */
216 /* Remove IV and ICV */
217 memmove(skb->data + 4, skb->data, hdr_len);
219 skb_trim(skb, skb->len - 4);
224 static int prism2_wep_set_key(void *key, int len, u8 *seq, void *priv)
226 struct prism2_wep_data *wep = priv;
228 if (len < 0 || len > WEP_KEY_LEN)
231 memcpy(wep->key, key, len);
238 static int prism2_wep_get_key(void *key, int len, u8 *seq, void *priv)
240 struct prism2_wep_data *wep = priv;
242 if (len < wep->key_len)
245 memcpy(key, wep->key, wep->key_len);
251 static char * prism2_wep_print_stats(char *p, void *priv)
253 struct prism2_wep_data *wep = priv;
254 p += sprintf(p, "key[%d] alg=WEP len=%d\n",
255 wep->key_idx, wep->key_len);
260 static struct ieee80211_crypto_ops ieee80211_crypt_wep = {
262 .init = prism2_wep_init,
263 .deinit = prism2_wep_deinit,
264 .encrypt_mpdu = prism2_wep_encrypt,
265 .decrypt_mpdu = prism2_wep_decrypt,
266 .encrypt_msdu = NULL,
267 .decrypt_msdu = NULL,
268 .set_key = prism2_wep_set_key,
269 .get_key = prism2_wep_get_key,
270 .print_stats = prism2_wep_print_stats,
271 .extra_prefix_len = 4, /* IV */
272 .extra_postfix_len = 4, /* ICV */
273 .owner = THIS_MODULE,
277 int ieee80211_crypto_wep_init(void)
279 return ieee80211_register_crypto_ops(&ieee80211_crypt_wep);
283 void ieee80211_crypto_wep_exit(void)
285 ieee80211_unregister_crypto_ops(&ieee80211_crypt_wep);
289 void ieee80211_wep_null(void)
291 // printk("============>%s()\n", __func__);