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 = kmalloc(sizeof(*priv), GFP_ATOMIC);
44 memset(priv, 0, sizeof(*priv));
45 priv->key_idx = keyidx;
47 priv->tx_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0, CRYPTO_ALG_ASYNC);
48 if (IS_ERR(priv->tx_tfm)) {
49 printk(KERN_DEBUG "rtllib_crypt_wep: could not allocate "
54 priv->rx_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0, CRYPTO_ALG_ASYNC);
55 if (IS_ERR(priv->rx_tfm)) {
56 printk(KERN_DEBUG "rtllib_crypt_wep: could not allocate "
62 /* start WEP IV from a random value */
63 get_random_bytes(&priv->iv, 4);
70 crypto_free_blkcipher(priv->tx_tfm);
72 crypto_free_blkcipher(priv->rx_tfm);
79 static void prism2_wep_deinit(void *priv)
81 struct prism2_wep_data *_priv = priv;
85 crypto_free_blkcipher(_priv->tx_tfm);
87 crypto_free_blkcipher(_priv->rx_tfm);
92 /* Perform WEP encryption on given skb that has at least 4 bytes of headroom
93 * for IV and 4 bytes of tailroom for ICV. Both IV and ICV will be transmitted,
94 * so the payload length increases with 8 bytes.
96 * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data))
98 static int prism2_wep_encrypt(struct sk_buff *skb, int hdr_len, void *priv)
100 struct prism2_wep_data *wep = priv;
102 u8 key[WEP_KEY_LEN + 3];
104 struct cb_desc *tcb_desc = (struct cb_desc *)(skb->cb +
106 struct blkcipher_desc desc = {.tfm = wep->tx_tfm};
109 struct scatterlist sg;
110 if (skb_headroom(skb) < 4 || skb_tailroom(skb) < 4 ||
112 printk(KERN_ERR "Error!!! headroom=%d tailroom=%d skblen=%d"
113 " hdr_len=%d\n", skb_headroom(skb), skb_tailroom(skb),
117 len = skb->len - hdr_len;
118 pos = skb_push(skb, 4);
119 memmove(pos, pos + 4, hdr_len);
122 klen = 3 + wep->key_len;
126 /* Fluhrer, Mantin, and Shamir have reported weaknesses in the key
127 * scheduling algorithm of RC4. At least IVs (KeyByte + 3, 0xff, N)
128 * can be used to speedup attacks, so avoid using them. */
129 if ((wep->iv & 0xff00) == 0xff00) {
130 u8 B = (wep->iv >> 16) & 0xff;
131 if (B >= 3 && B < klen)
135 /* Prepend 24-bit IV to RC4 key and TX frame */
136 *pos++ = key[0] = (wep->iv >> 16) & 0xff;
137 *pos++ = key[1] = (wep->iv >> 8) & 0xff;
138 *pos++ = key[2] = wep->iv & 0xff;
139 *pos++ = wep->key_idx << 6;
141 /* Copy rest of the WEP key (the secret part) */
142 memcpy(key + 3, wep->key, wep->key_len);
144 if (!tcb_desc->bHwSec) {
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 sg_init_one(&sg, pos, len+4);
155 crypto_blkcipher_setkey(wep->tx_tfm, key, klen);
156 return crypto_blkcipher_encrypt(&desc, &sg, &sg, len + 4);
163 /* Perform WEP decryption on given struct buffer. Buffer includes whole WEP
164 * part of the frame: IV (4 bytes), encrypted payload (including SNAP header),
165 * ICV (4 bytes). len includes both IV and ICV.
167 * Returns 0 if frame was decrypted successfully and ICV was correct and -1 on
168 * failure. If frame is OK, IV and ICV will be removed.
170 static int prism2_wep_decrypt(struct sk_buff *skb, int hdr_len, void *priv)
172 struct prism2_wep_data *wep = priv;
174 u8 key[WEP_KEY_LEN + 3];
176 struct cb_desc *tcb_desc = (struct cb_desc *)(skb->cb +
178 struct blkcipher_desc desc = {.tfm = wep->rx_tfm};
181 struct scatterlist sg;
182 if (skb->len < hdr_len + 8)
185 pos = skb->data + hdr_len;
189 keyidx = *pos++ >> 6;
190 if (keyidx != wep->key_idx)
193 klen = 3 + wep->key_len;
195 /* Copy rest of the WEP key (the secret part) */
196 memcpy(key + 3, wep->key, wep->key_len);
198 /* Apply RC4 to data and compute CRC32 over decrypted data */
199 plen = skb->len - hdr_len - 8;
201 if (!tcb_desc->bHwSec) {
202 sg_init_one(&sg, pos, plen+4);
203 crypto_blkcipher_setkey(wep->rx_tfm, key, klen);
204 if (crypto_blkcipher_decrypt(&desc, &sg, &sg, plen + 4))
206 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);
225 static int prism2_wep_set_key(void *key, int len, u8 *seq, void *priv)
227 struct prism2_wep_data *wep = priv;
229 if (len < 0 || len > WEP_KEY_LEN)
232 memcpy(wep->key, key, len);
239 static int prism2_wep_get_key(void *key, int len, u8 *seq, void *priv)
241 struct prism2_wep_data *wep = priv;
243 if (len < wep->key_len)
246 memcpy(key, wep->key, wep->key_len);
252 static char *prism2_wep_print_stats(char *p, void *priv)
254 struct prism2_wep_data *wep = priv;
255 p += sprintf(p, "key[%d] alg=WEP len=%d\n",
256 wep->key_idx, wep->key_len);
261 static struct rtllib_crypto_ops rtllib_crypt_wep = {
263 .init = prism2_wep_init,
264 .deinit = prism2_wep_deinit,
265 .encrypt_mpdu = prism2_wep_encrypt,
266 .decrypt_mpdu = prism2_wep_decrypt,
267 .encrypt_msdu = NULL,
268 .decrypt_msdu = NULL,
269 .set_key = prism2_wep_set_key,
270 .get_key = prism2_wep_get_key,
271 .print_stats = prism2_wep_print_stats,
272 .extra_prefix_len = 4, /* IV */
273 .extra_postfix_len = 4, /* ICV */
274 .owner = THIS_MODULE,
278 int __init rtllib_crypto_wep_init(void)
280 return rtllib_register_crypto_ops(&rtllib_crypt_wep);
284 void __exit rtllib_crypto_wep_exit(void)
286 rtllib_unregister_crypto_ops(&rtllib_crypt_wep);
289 void rtllib_wep_null(void)