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/version.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 <linux/string.h>
21 #include <linux/crypto.h>
23 #include <linux/scatterlist.h>
24 #include <linux/crc32.h>
26 struct prism2_wep_data {
28 #define WEP_KEY_LEN 13
29 u8 key[WEP_KEY_LEN + 1];
32 struct crypto_blkcipher *tx_tfm;
33 struct crypto_blkcipher *rx_tfm;
37 static void *prism2_wep_init(int keyidx)
39 struct prism2_wep_data *priv;
41 priv = kzalloc(sizeof(*priv), GFP_ATOMIC);
44 priv->key_idx = keyidx;
46 priv->tx_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0, CRYPTO_ALG_ASYNC);
47 if (IS_ERR(priv->tx_tfm)) {
48 printk(KERN_DEBUG "rtllib_crypt_wep: could not allocate "
53 priv->rx_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0, CRYPTO_ALG_ASYNC);
54 if (IS_ERR(priv->rx_tfm)) {
55 printk(KERN_DEBUG "rtllib_crypt_wep: could not allocate "
61 /* start WEP IV from a random value */
62 get_random_bytes(&priv->iv, 4);
69 crypto_free_blkcipher(priv->tx_tfm);
71 crypto_free_blkcipher(priv->rx_tfm);
78 static void prism2_wep_deinit(void *priv)
80 struct prism2_wep_data *_priv = priv;
84 crypto_free_blkcipher(_priv->tx_tfm);
86 crypto_free_blkcipher(_priv->rx_tfm);
91 /* Perform WEP encryption on given skb that has at least 4 bytes of headroom
92 * for IV and 4 bytes of tailroom for ICV. Both IV and ICV will be transmitted,
93 * so the payload length increases with 8 bytes.
95 * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data))
97 static int prism2_wep_encrypt(struct sk_buff *skb, int hdr_len, void *priv)
99 struct prism2_wep_data *wep = priv;
101 u8 key[WEP_KEY_LEN + 3];
103 struct cb_desc *tcb_desc = (struct cb_desc *)(skb->cb +
105 struct blkcipher_desc desc = {.tfm = wep->tx_tfm};
108 struct scatterlist sg;
109 if (skb_headroom(skb) < 4 || skb_tailroom(skb) < 4 ||
111 printk(KERN_ERR "Error!!! headroom=%d tailroom=%d skblen=%d"
112 " hdr_len=%d\n", skb_headroom(skb), skb_tailroom(skb),
116 len = skb->len - hdr_len;
117 pos = skb_push(skb, 4);
118 memmove(pos, pos + 4, hdr_len);
121 klen = 3 + wep->key_len;
125 /* Fluhrer, Mantin, and Shamir have reported weaknesses in the key
126 * scheduling algorithm of RC4. At least IVs (KeyByte + 3, 0xff, N)
127 * can be used to speedup attacks, so avoid using them. */
128 if ((wep->iv & 0xff00) == 0xff00) {
129 u8 B = (wep->iv >> 16) & 0xff;
130 if (B >= 3 && B < klen)
134 /* Prepend 24-bit IV to RC4 key and TX frame */
135 *pos++ = key[0] = (wep->iv >> 16) & 0xff;
136 *pos++ = key[1] = (wep->iv >> 8) & 0xff;
137 *pos++ = key[2] = wep->iv & 0xff;
138 *pos++ = wep->key_idx << 6;
140 /* Copy rest of the WEP key (the secret part) */
141 memcpy(key + 3, wep->key, wep->key_len);
143 if (!tcb_desc->bHwSec) {
145 /* Append little-endian CRC32 and encrypt it to produce ICV */
146 crc = ~crc32_le(~0, pos, len);
147 icv = skb_put(skb, 4);
153 sg_init_one(&sg, pos, len+4);
154 crypto_blkcipher_setkey(wep->tx_tfm, key, klen);
155 return crypto_blkcipher_encrypt(&desc, &sg, &sg, len + 4);
162 /* Perform WEP decryption on given struct buffer. Buffer includes whole WEP
163 * part of 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;
173 u8 key[WEP_KEY_LEN + 3];
175 struct cb_desc *tcb_desc = (struct cb_desc *)(skb->cb +
177 struct blkcipher_desc desc = {.tfm = wep->rx_tfm};
180 struct scatterlist sg;
181 if (skb->len < hdr_len + 8)
184 pos = skb->data + hdr_len;
188 keyidx = *pos++ >> 6;
189 if (keyidx != wep->key_idx)
192 klen = 3 + wep->key_len;
194 /* Copy rest of the WEP key (the secret part) */
195 memcpy(key + 3, wep->key, wep->key_len);
197 /* Apply RC4 to data and compute CRC32 over decrypted data */
198 plen = skb->len - hdr_len - 8;
200 if (!tcb_desc->bHwSec) {
201 sg_init_one(&sg, pos, plen+4);
202 crypto_blkcipher_setkey(wep->rx_tfm, key, klen);
203 if (crypto_blkcipher_decrypt(&desc, &sg, &sg, plen + 4))
205 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);
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);
259 static struct rtllib_crypto_ops rtllib_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 __init rtllib_crypto_wep_init(void)
278 return rtllib_register_crypto_ops(&rtllib_crypt_wep);
282 void __exit rtllib_crypto_wep_exit(void)
284 rtllib_unregister_crypto_ops(&rtllib_crypt_wep);
287 module_init(rtllib_crypto_wep_init);
288 module_exit(rtllib_crypto_wep_exit);
290 MODULE_LICENSE("GPL");