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 <asm/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
+ MAX_DEV_ADDR_SIZE
);
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("Error!!!headroom=%d tailroom=%d skblen=%d hdr_len=%d\n",skb_headroom(skb
),skb_tailroom(skb
),skb
->len
,hdr_len
);
114 len
= skb
->len
- hdr_len
;
115 pos
= skb_push(skb
, 4);
116 memmove(pos
, pos
+ 4, hdr_len
);
119 klen
= 3 + wep
->key_len
;
123 /* Fluhrer, Mantin, and Shamir have reported weaknesses in the key
124 * scheduling algorithm of RC4. At least IVs (KeyByte + 3, 0xff, N)
125 * can be used to speedup attacks, so avoid using them. */
126 if ((wep
->iv
& 0xff00) == 0xff00) {
127 u8 B
= (wep
->iv
>> 16) & 0xff;
128 if (B
>= 3 && B
< klen
)
132 /* Prepend 24-bit IV to RC4 key and TX frame */
133 *pos
++ = key
[0] = (wep
->iv
>> 16) & 0xff;
134 *pos
++ = key
[1] = (wep
->iv
>> 8) & 0xff;
135 *pos
++ = key
[2] = wep
->iv
& 0xff;
136 *pos
++ = wep
->key_idx
<< 6;
138 /* Copy rest of the WEP key (the secret part) */
139 memcpy(key
+ 3, wep
->key
, wep
->key_len
);
141 if (!tcb_desc
->bHwSec
) {
143 /* Append little-endian CRC32 and encrypt it to produce ICV */
144 crc
= ~crc32_le(~0, pos
, len
);
145 icv
= skb_put(skb
, 4);
151 sg_init_one(&sg
, pos
, len
+4);
152 crypto_blkcipher_setkey(wep
->tx_tfm
, key
, klen
);
153 return crypto_blkcipher_encrypt(&desc
, &sg
, &sg
, len
+ 4);
160 /* Perform WEP decryption on given buffer. Buffer includes whole WEP part of
161 * the frame: IV (4 bytes), encrypted payload (including SNAP header),
162 * ICV (4 bytes). len includes both IV and ICV.
164 * Returns 0 if frame was decrypted successfully and ICV was correct and -1 on
165 * failure. If frame is OK, IV and ICV will be removed.
167 static int prism2_wep_decrypt(struct sk_buff
*skb
, int hdr_len
, void *priv
)
169 struct prism2_wep_data
*wep
= priv
;
171 u8 key
[WEP_KEY_LEN
+ 3];
173 struct cb_desc
*tcb_desc
= (struct cb_desc
*)(skb
->cb
+ MAX_DEV_ADDR_SIZE
);
174 struct blkcipher_desc desc
= {.tfm
= wep
->rx_tfm
};
177 struct scatterlist sg
;
178 if (skb
->len
< hdr_len
+ 8)
181 pos
= skb
->data
+ hdr_len
;
185 keyidx
= *pos
++ >> 6;
186 if (keyidx
!= wep
->key_idx
)
189 klen
= 3 + wep
->key_len
;
191 /* Copy rest of the WEP key (the secret part) */
192 memcpy(key
+ 3, wep
->key
, wep
->key_len
);
194 /* Apply RC4 to data and compute CRC32 over decrypted data */
195 plen
= skb
->len
- hdr_len
- 8;
197 if (!tcb_desc
->bHwSec
) {
198 sg_init_one(&sg
, pos
, plen
+4);
199 crypto_blkcipher_setkey(wep
->rx_tfm
, key
, klen
);
200 if (crypto_blkcipher_decrypt(&desc
, &sg
, &sg
, plen
+ 4))
202 crc
= ~crc32_le(~0, pos
, plen
);
207 if (memcmp(icv
, pos
+ plen
, 4) != 0) {
208 /* ICV mismatch - drop frame */
212 /* Remove IV and ICV */
213 memmove(skb
->data
+ 4, skb
->data
, hdr_len
);
215 skb_trim(skb
, skb
->len
- 4);
221 static int prism2_wep_set_key(void *key
, int len
, u8
*seq
, void *priv
)
223 struct prism2_wep_data
*wep
= priv
;
225 if (len
< 0 || len
> WEP_KEY_LEN
)
228 memcpy(wep
->key
, key
, len
);
235 static int prism2_wep_get_key(void *key
, int len
, u8
*seq
, void *priv
)
237 struct prism2_wep_data
*wep
= priv
;
239 if (len
< wep
->key_len
)
242 memcpy(key
, wep
->key
, wep
->key_len
);
248 static char * prism2_wep_print_stats(char *p
, void *priv
)
250 struct prism2_wep_data
*wep
= priv
;
251 p
+= sprintf(p
, "key[%d] alg=WEP len=%d\n",
252 wep
->key_idx
, wep
->key_len
);
257 static struct rtllib_crypto_ops rtllib_crypt_wep
= {
259 .init
= prism2_wep_init
,
260 .deinit
= prism2_wep_deinit
,
261 .encrypt_mpdu
= prism2_wep_encrypt
,
262 .decrypt_mpdu
= prism2_wep_decrypt
,
263 .encrypt_msdu
= NULL
,
264 .decrypt_msdu
= NULL
,
265 .set_key
= prism2_wep_set_key
,
266 .get_key
= prism2_wep_get_key
,
267 .print_stats
= prism2_wep_print_stats
,
268 .extra_prefix_len
= 4, /* IV */
269 .extra_postfix_len
= 4, /* ICV */
270 .owner
= THIS_MODULE
,
274 int __init
rtllib_crypto_wep_init(void)
276 return rtllib_register_crypto_ops(&rtllib_crypt_wep
);
280 void __exit
rtllib_crypto_wep_exit(void)
282 rtllib_unregister_crypto_ops(&rtllib_crypt_wep
);
285 void rtllib_wep_null(void)