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 static int __init
rtllib_crypto_wep_init(void)
275 return lib80211_register_crypto_ops(&rtllib_crypt_wep
);
279 static 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");