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 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
14 //#include <linux/config.h>
15 #include <linux/module.h>
16 #include <linux/slab.h>
17 #include <linux/random.h>
18 #include <linux/skbuff.h>
19 #include <linux/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 pr_debug("could not allocate crypto API arc4\n");
58 priv->rx_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0, CRYPTO_ALG_ASYNC);
59 if (IS_ERR(priv->rx_tfm)) {
60 pr_debug("could not allocate crypto API arc4\n");
65 /* start WEP IV from a random value */
66 get_random_bytes(&priv->iv, 4);
73 crypto_free_blkcipher(priv->tx_tfm);
75 crypto_free_blkcipher(priv->rx_tfm);
83 static void prism2_wep_deinit(void *priv)
85 struct prism2_wep_data *_priv = priv;
89 crypto_free_blkcipher(_priv->tx_tfm);
91 crypto_free_blkcipher(_priv->rx_tfm);
98 /* Perform WEP encryption on given skb that has at least 4 bytes of headroom
99 * for IV and 4 bytes of tailroom for ICV. Both IV and ICV will be transmitted,
100 * so the payload length increases with 8 bytes.
102 * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data))
104 static int prism2_wep_encrypt(struct sk_buff *skb, int hdr_len, void *priv)
106 struct prism2_wep_data *wep = priv;
107 struct blkcipher_desc desc = { .tfm = wep->tx_tfm };
109 u8 key[WEP_KEY_LEN + 3];
113 struct scatterlist sg;
115 if (skb_headroom(skb) < 4 || skb_tailroom(skb) < 4 ||
119 len = skb->len - hdr_len;
120 pos = skb_push(skb, 4);
121 memmove(pos, pos + 4, hdr_len);
124 klen = 3 + wep->key_len;
128 /* Fluhrer, Mantin, and Shamir have reported weaknesses in the key
129 * scheduling algorithm of RC4. At least IVs (KeyByte + 3, 0xff, N)
130 * can be used to speedup attacks, so avoid using them. */
131 if ((wep->iv & 0xff00) == 0xff00) {
132 u8 B = (wep->iv >> 16) & 0xff;
133 if (B >= 3 && B < klen)
137 /* Prepend 24-bit IV to RC4 key and TX frame */
138 *pos++ = key[0] = (wep->iv >> 16) & 0xff;
139 *pos++ = key[1] = (wep->iv >> 8) & 0xff;
140 *pos++ = key[2] = wep->iv & 0xff;
141 *pos++ = wep->key_idx << 6;
143 /* Copy rest of the WEP key (the secret part) */
144 memcpy(key + 3, wep->key, wep->key_len);
146 /* Append little-endian CRC32 and encrypt it to produce ICV */
147 crc = ~crc32_le(~0, pos, len);
148 icv = skb_put(skb, 4);
154 crypto_blkcipher_setkey(wep->tx_tfm, key, klen);
155 sg_init_one(&sg, pos, len + 4);
157 return crypto_blkcipher_encrypt(&desc, &sg, &sg, len + 4);
161 /* Perform WEP decryption on given buffer. Buffer includes whole WEP part of
162 * the frame: IV (4 bytes), encrypted payload (including SNAP header),
163 * ICV (4 bytes). len includes both IV and ICV.
165 * Returns 0 if frame was decrypted successfully and ICV was correct and -1 on
166 * failure. If frame is OK, IV and ICV will be removed.
168 static int prism2_wep_decrypt(struct sk_buff *skb, int hdr_len, void *priv)
170 struct prism2_wep_data *wep = priv;
171 struct blkcipher_desc desc = { .tfm = wep->rx_tfm };
173 u8 key[WEP_KEY_LEN + 3];
177 struct scatterlist sg;
179 if (skb->len < hdr_len + 8)
182 pos = skb->data + hdr_len;
186 keyidx = *pos++ >> 6;
187 if (keyidx != wep->key_idx)
190 klen = 3 + wep->key_len;
192 /* Copy rest of the WEP key (the secret part) */
193 memcpy(key + 3, wep->key, wep->key_len);
195 /* Apply RC4 to data and compute CRC32 over decrypted data */
196 plen = skb->len - hdr_len - 8;
198 crypto_blkcipher_setkey(wep->rx_tfm, key, klen);
199 sg_init_one(&sg, pos, plen + 4);
201 if (crypto_blkcipher_decrypt(&desc, &sg, &sg, plen + 4))
204 crc = ~crc32_le(~0, pos, plen);
210 if (memcmp(icv, pos + plen, 4) != 0) {
211 /* ICV mismatch - drop frame */
215 /* Remove IV and ICV */
216 memmove(skb->data + 4, skb->data, hdr_len);
218 skb_trim(skb, skb->len - 4);
223 static int prism2_wep_set_key(void *key, int len, u8 *seq, void *priv)
225 struct prism2_wep_data *wep = priv;
227 if (len < 0 || len > WEP_KEY_LEN)
230 memcpy(wep->key, key, len);
237 static int prism2_wep_get_key(void *key, int len, u8 *seq, void *priv)
239 struct prism2_wep_data *wep = priv;
241 if (len < wep->key_len)
244 memcpy(key, wep->key, wep->key_len);
250 static char *prism2_wep_print_stats(char *p, void *priv)
252 struct prism2_wep_data *wep = priv;
253 p += sprintf(p, "key[%d] alg=WEP len=%d\n",
254 wep->key_idx, wep->key_len);
259 static struct ieee80211_crypto_ops ieee80211_crypt_wep = {
261 .init = prism2_wep_init,
262 .deinit = prism2_wep_deinit,
263 .encrypt_mpdu = prism2_wep_encrypt,
264 .decrypt_mpdu = prism2_wep_decrypt,
265 .encrypt_msdu = NULL,
266 .decrypt_msdu = NULL,
267 .set_key = prism2_wep_set_key,
268 .get_key = prism2_wep_get_key,
269 .print_stats = prism2_wep_print_stats,
270 .extra_prefix_len = 4, /* IV */
271 .extra_postfix_len = 4, /* ICV */
272 .owner = THIS_MODULE,
276 int ieee80211_crypto_wep_init(void)
278 return ieee80211_register_crypto_ops(&ieee80211_crypt_wep);
282 void ieee80211_crypto_wep_exit(void)
284 ieee80211_unregister_crypto_ops(&ieee80211_crypt_wep);
288 void ieee80211_wep_null(void)
290 // printk("============>%s()\n", __func__);