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"
24 #include <linux/crypto.h>
26 #include <linux/scatterlist.h>
27 #include <linux/crc32.h>
29 MODULE_AUTHOR("Jouni Malinen");
30 MODULE_DESCRIPTION("Host AP crypt: WEP");
31 MODULE_LICENSE("GPL");
33 #define OPENSUSE_SLED 0
36 struct prism2_wep_data {
38 #define WEP_KEY_LEN 13
39 u8 key[WEP_KEY_LEN + 1];
42 struct crypto_blkcipher *tx_tfm;
43 struct crypto_blkcipher *rx_tfm;
47 static void * prism2_wep_init(int keyidx)
49 struct prism2_wep_data *priv;
51 priv = kzalloc(sizeof(*priv), GFP_ATOMIC);
54 priv->key_idx = keyidx;
56 priv->tx_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0, CRYPTO_ALG_ASYNC);
57 if (IS_ERR(priv->tx_tfm)) {
58 printk(KERN_DEBUG "ieee80211_crypt_wep: could not allocate "
63 priv->rx_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0, CRYPTO_ALG_ASYNC);
64 if (IS_ERR(priv->rx_tfm)) {
65 printk(KERN_DEBUG "ieee80211_crypt_wep: could not allocate "
71 /* start WEP IV from a random value */
72 get_random_bytes(&priv->iv, 4);
79 crypto_free_blkcipher(priv->tx_tfm);
81 crypto_free_blkcipher(priv->rx_tfm);
88 static void prism2_wep_deinit(void *priv)
90 struct prism2_wep_data *_priv = priv;
93 crypto_free_blkcipher(_priv->tx_tfm);
95 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;
110 u8 key[WEP_KEY_LEN + 3];
112 cb_desc *tcb_desc = (cb_desc *)(skb->cb + MAX_DEV_ADDR_SIZE);
113 struct blkcipher_desc desc = {.tfm = wep->tx_tfm};
116 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 if (!tcb_desc->bHwSec)
151 /* Append little-endian CRC32 and encrypt it to produce ICV */
152 crc = ~crc32_le(~0, pos, len);
153 icv = skb_put(skb, 4);
159 crypto_blkcipher_setkey(wep->tx_tfm, key, klen);
160 sg_init_one(&sg, pos, len+4);
161 return crypto_blkcipher_encrypt(&desc, &sg, &sg, len + 4);
168 /* Perform WEP decryption on given buffer. Buffer includes whole WEP part of
169 * the frame: IV (4 bytes), encrypted payload (including SNAP header),
170 * ICV (4 bytes). len includes both IV and ICV.
172 * Returns 0 if frame was decrypted successfully and ICV was correct and -1 on
173 * failure. If frame is OK, IV and ICV will be removed.
175 static int prism2_wep_decrypt(struct sk_buff *skb, int hdr_len, void *priv)
177 struct prism2_wep_data *wep = priv;
179 u8 key[WEP_KEY_LEN + 3];
181 cb_desc *tcb_desc = (cb_desc *)(skb->cb + MAX_DEV_ADDR_SIZE);
182 struct blkcipher_desc desc = {.tfm = wep->rx_tfm};
185 struct scatterlist sg;
186 if (skb->len < hdr_len + 8)
189 pos = skb->data + hdr_len;
193 keyidx = *pos++ >> 6;
194 if (keyidx != wep->key_idx)
197 klen = 3 + wep->key_len;
199 /* Copy rest of the WEP key (the secret part) */
200 memcpy(key + 3, wep->key, wep->key_len);
202 /* Apply RC4 to data and compute CRC32 over decrypted data */
203 plen = skb->len - hdr_len - 8;
205 if (!tcb_desc->bHwSec)
207 crypto_blkcipher_setkey(wep->rx_tfm, key, klen);
208 sg_init_one(&sg, pos, plen+4);
209 if (crypto_blkcipher_decrypt(&desc, &sg, &sg, plen + 4))
211 crc = ~crc32_le(~0, pos, plen);
216 if (memcmp(icv, pos + plen, 4) != 0) {
217 /* ICV mismatch - drop frame */
221 /* Remove IV and ICV */
222 memmove(skb->data + 4, skb->data, hdr_len);
224 skb_trim(skb, skb->len - 4);
230 static int prism2_wep_set_key(void *key, int len, u8 *seq, void *priv)
232 struct prism2_wep_data *wep = priv;
234 if (len < 0 || len > WEP_KEY_LEN)
237 memcpy(wep->key, key, len);
244 static int prism2_wep_get_key(void *key, int len, u8 *seq, void *priv)
246 struct prism2_wep_data *wep = priv;
248 if (len < wep->key_len)
251 memcpy(key, wep->key, wep->key_len);
257 static char * prism2_wep_print_stats(char *p, void *priv)
259 struct prism2_wep_data *wep = priv;
260 p += sprintf(p, "key[%d] alg=WEP len=%d\n",
261 wep->key_idx, wep->key_len);
266 static struct ieee80211_crypto_ops ieee80211_crypt_wep = {
268 .init = prism2_wep_init,
269 .deinit = prism2_wep_deinit,
270 .encrypt_mpdu = prism2_wep_encrypt,
271 .decrypt_mpdu = prism2_wep_decrypt,
272 .encrypt_msdu = NULL,
273 .decrypt_msdu = NULL,
274 .set_key = prism2_wep_set_key,
275 .get_key = prism2_wep_get_key,
276 .print_stats = prism2_wep_print_stats,
277 .extra_prefix_len = 4, /* IV */
278 .extra_postfix_len = 4, /* ICV */
279 .owner = THIS_MODULE,
283 int __init ieee80211_crypto_wep_init(void)
285 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)