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/module.h>
13 #include <linux/init.h>
14 #include <linux/slab.h>
15 #include <linux/random.h>
16 #include <linux/skbuff.h>
17 #include <linux/string.h>
20 #include <linux/crypto.h>
22 #include <linux/scatterlist.h>
23 #include <linux/crc32.h>
25 struct prism2_wep_data {
27 #define WEP_KEY_LEN 13
28 u8 key[WEP_KEY_LEN + 1];
31 struct crypto_blkcipher *tx_tfm;
32 struct crypto_blkcipher *rx_tfm;
36 static void *prism2_wep_init(int keyidx)
38 struct prism2_wep_data *priv;
40 priv = kzalloc(sizeof(*priv), GFP_ATOMIC);
43 priv->key_idx = keyidx;
45 priv->tx_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0, CRYPTO_ALG_ASYNC);
46 if (IS_ERR(priv->tx_tfm)) {
47 printk(KERN_DEBUG "rtllib_crypt_wep: could not allocate "
52 priv->rx_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0, CRYPTO_ALG_ASYNC);
53 if (IS_ERR(priv->rx_tfm)) {
54 printk(KERN_DEBUG "rtllib_crypt_wep: could not allocate "
60 /* start WEP IV from a random value */
61 get_random_bytes(&priv->iv, 4);
68 crypto_free_blkcipher(priv->tx_tfm);
70 crypto_free_blkcipher(priv->rx_tfm);
77 static void prism2_wep_deinit(void *priv)
79 struct prism2_wep_data *_priv = priv;
83 crypto_free_blkcipher(_priv->tx_tfm);
85 crypto_free_blkcipher(_priv->rx_tfm);
90 /* Perform WEP encryption on given skb that has at least 4 bytes of headroom
91 * for IV and 4 bytes of tailroom for ICV. Both IV and ICV will be transmitted,
92 * so the payload length increases with 8 bytes.
94 * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data))
96 static int prism2_wep_encrypt(struct sk_buff *skb, int hdr_len, void *priv)
98 struct prism2_wep_data *wep = priv;
100 u8 key[WEP_KEY_LEN + 3];
102 struct cb_desc *tcb_desc = (struct cb_desc *)(skb->cb +
104 struct blkcipher_desc desc = {.tfm = wep->tx_tfm};
107 struct scatterlist sg;
108 if (skb_headroom(skb) < 4 || skb_tailroom(skb) < 4 ||
110 printk(KERN_ERR "Error!!! headroom=%d tailroom=%d skblen=%d"
111 " hdr_len=%d\n", skb_headroom(skb), skb_tailroom(skb),
115 len = skb->len - hdr_len;
116 pos = skb_push(skb, 4);
117 memmove(pos, pos + 4, hdr_len);
120 klen = 3 + wep->key_len;
124 /* Fluhrer, Mantin, and Shamir have reported weaknesses in the key
125 * scheduling algorithm of RC4. At least IVs (KeyByte + 3, 0xff, N)
126 * can be used to speedup attacks, so avoid using them. */
127 if ((wep->iv & 0xff00) == 0xff00) {
128 u8 B = (wep->iv >> 16) & 0xff;
129 if (B >= 3 && B < klen)
133 /* Prepend 24-bit IV to RC4 key and TX frame */
134 *pos++ = key[0] = (wep->iv >> 16) & 0xff;
135 *pos++ = key[1] = (wep->iv >> 8) & 0xff;
136 *pos++ = key[2] = wep->iv & 0xff;
137 *pos++ = wep->key_idx << 6;
139 /* Copy rest of the WEP key (the secret part) */
140 memcpy(key + 3, wep->key, wep->key_len);
142 if (!tcb_desc->bHwSec) {
144 /* Append little-endian CRC32 and encrypt it to produce ICV */
145 crc = ~crc32_le(~0, pos, len);
146 icv = skb_put(skb, 4);
152 sg_init_one(&sg, pos, len+4);
153 crypto_blkcipher_setkey(wep->tx_tfm, key, klen);
154 return crypto_blkcipher_encrypt(&desc, &sg, &sg, len + 4);
161 /* Perform WEP decryption on given struct buffer. Buffer includes whole WEP
162 * part of 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;
172 u8 key[WEP_KEY_LEN + 3];
174 struct cb_desc *tcb_desc = (struct cb_desc *)(skb->cb +
176 struct blkcipher_desc desc = {.tfm = wep->rx_tfm};
179 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 if (!tcb_desc->bHwSec) {
200 sg_init_one(&sg, pos, plen+4);
201 crypto_blkcipher_setkey(wep->rx_tfm, key, klen);
202 if (crypto_blkcipher_decrypt(&desc, &sg, &sg, plen + 4))
204 crc = ~crc32_le(~0, pos, plen);
209 if (memcmp(icv, pos + plen, 4) != 0) {
210 /* ICV mismatch - drop frame */
214 /* Remove IV and ICV */
215 memmove(skb->data + 4, skb->data, hdr_len);
217 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 void prism2_wep_print_stats(struct seq_file *m, void *priv)
252 struct prism2_wep_data *wep = priv;
253 seq_printf(m, "key[%d] alg=WEP len=%d\n", wep->key_idx, wep->key_len);
256 static struct lib80211_crypto_ops rtllib_crypt_wep = {
258 .init = prism2_wep_init,
259 .deinit = prism2_wep_deinit,
260 .encrypt_mpdu = prism2_wep_encrypt,
261 .decrypt_mpdu = prism2_wep_decrypt,
262 .encrypt_msdu = NULL,
263 .decrypt_msdu = NULL,
264 .set_key = prism2_wep_set_key,
265 .get_key = prism2_wep_get_key,
266 .print_stats = prism2_wep_print_stats,
267 .extra_mpdu_prefix_len = 4, /* IV */
268 .extra_mpdu_postfix_len = 4, /* ICV */
269 .owner = THIS_MODULE,
273 int __init rtllib_crypto_wep_init(void)
275 return lib80211_register_crypto_ops(&rtllib_crypt_wep);
279 void __exit rtllib_crypto_wep_exit(void)
281 lib80211_unregister_crypto_ops(&rtllib_crypt_wep);
284 module_init(rtllib_crypto_wep_init);
285 module_exit(rtllib_crypto_wep_exit);
287 MODULE_LICENSE("GPL");