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/config.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>
20 #include <net/ieee80211.h>
22 #include <linux/crypto.h>
23 #include <asm/scatterlist.h>
24 #include <linux/crc32.h>
26 MODULE_AUTHOR("Jouni Malinen");
27 MODULE_DESCRIPTION("Host AP crypt: WEP");
28 MODULE_LICENSE("GPL");
30 struct prism2_wep_data
{
32 #define WEP_KEY_LEN 13
33 u8 key
[WEP_KEY_LEN
+ 1];
36 struct crypto_tfm
*tfm
;
39 static void *prism2_wep_init(int keyidx
)
41 struct prism2_wep_data
*priv
;
43 priv
= kmalloc(sizeof(*priv
), GFP_ATOMIC
);
46 memset(priv
, 0, sizeof(*priv
));
47 priv
->key_idx
= keyidx
;
49 priv
->tfm
= crypto_alloc_tfm("arc4", 0);
50 if (priv
->tfm
== NULL
) {
51 printk(KERN_DEBUG
"ieee80211_crypt_wep: could not allocate "
56 /* start WEP IV from a random value */
57 get_random_bytes(&priv
->iv
, 4);
64 crypto_free_tfm(priv
->tfm
);
70 static void prism2_wep_deinit(void *priv
)
72 struct prism2_wep_data
*_priv
= priv
;
73 if (_priv
&& _priv
->tfm
)
74 crypto_free_tfm(_priv
->tfm
);
78 /* Perform WEP encryption on given skb that has at least 4 bytes of headroom
79 * for IV and 4 bytes of tailroom for ICV. Both IV and ICV will be transmitted,
80 * so the payload length increases with 8 bytes.
82 * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data))
84 static int prism2_wep_encrypt(struct sk_buff
*skb
, int hdr_len
, void *priv
)
86 struct prism2_wep_data
*wep
= priv
;
88 u8 key
[WEP_KEY_LEN
+ 3];
90 struct scatterlist sg
;
92 if (skb_headroom(skb
) < 4 || skb_tailroom(skb
) < 4 ||
96 len
= skb
->len
- hdr_len
;
97 pos
= skb_push(skb
, 4);
98 memmove(pos
, pos
+ 4, hdr_len
);
101 klen
= 3 + wep
->key_len
;
105 /* Fluhrer, Mantin, and Shamir have reported weaknesses in the key
106 * scheduling algorithm of RC4. At least IVs (KeyByte + 3, 0xff, N)
107 * can be used to speedup attacks, so avoid using them. */
108 if ((wep
->iv
& 0xff00) == 0xff00) {
109 u8 B
= (wep
->iv
>> 16) & 0xff;
110 if (B
>= 3 && B
< klen
)
114 /* Prepend 24-bit IV to RC4 key and TX frame */
115 *pos
++ = key
[0] = (wep
->iv
>> 16) & 0xff;
116 *pos
++ = key
[1] = (wep
->iv
>> 8) & 0xff;
117 *pos
++ = key
[2] = wep
->iv
& 0xff;
118 *pos
++ = wep
->key_idx
<< 6;
120 /* Copy rest of the WEP key (the secret part) */
121 memcpy(key
+ 3, wep
->key
, wep
->key_len
);
123 /* Append little-endian CRC32 and encrypt it to produce ICV */
124 crc
= ~crc32_le(~0, pos
, len
);
125 icv
= skb_put(skb
, 4);
131 crypto_cipher_setkey(wep
->tfm
, key
, klen
);
132 sg
.page
= virt_to_page(pos
);
133 sg
.offset
= offset_in_page(pos
);
135 crypto_cipher_encrypt(wep
->tfm
, &sg
, &sg
, len
+ 4);
140 /* Perform WEP decryption on given buffer. Buffer includes whole WEP part of
141 * the frame: IV (4 bytes), encrypted payload (including SNAP header),
142 * ICV (4 bytes). len includes both IV and ICV.
144 * Returns 0 if frame was decrypted successfully and ICV was correct and -1 on
145 * failure. If frame is OK, IV and ICV will be removed.
147 static int prism2_wep_decrypt(struct sk_buff
*skb
, int hdr_len
, void *priv
)
149 struct prism2_wep_data
*wep
= priv
;
151 u8 key
[WEP_KEY_LEN
+ 3];
152 u8 keyidx
, *pos
, icv
[4];
153 struct scatterlist sg
;
155 if (skb
->len
< hdr_len
+ 8)
158 pos
= skb
->data
+ hdr_len
;
162 keyidx
= *pos
++ >> 6;
163 if (keyidx
!= wep
->key_idx
)
166 klen
= 3 + wep
->key_len
;
168 /* Copy rest of the WEP key (the secret part) */
169 memcpy(key
+ 3, wep
->key
, wep
->key_len
);
171 /* Apply RC4 to data and compute CRC32 over decrypted data */
172 plen
= skb
->len
- hdr_len
- 8;
174 crypto_cipher_setkey(wep
->tfm
, key
, klen
);
175 sg
.page
= virt_to_page(pos
);
176 sg
.offset
= offset_in_page(pos
);
177 sg
.length
= plen
+ 4;
178 crypto_cipher_decrypt(wep
->tfm
, &sg
, &sg
, plen
+ 4);
180 crc
= ~crc32_le(~0, pos
, plen
);
185 if (memcmp(icv
, pos
+ plen
, 4) != 0) {
186 /* ICV mismatch - drop frame */
190 /* Remove IV and ICV */
191 memmove(skb
->data
+ 4, skb
->data
, hdr_len
);
193 skb_trim(skb
, skb
->len
- 4);
198 static int prism2_wep_set_key(void *key
, int len
, u8
* seq
, void *priv
)
200 struct prism2_wep_data
*wep
= priv
;
202 if (len
< 0 || len
> WEP_KEY_LEN
)
205 memcpy(wep
->key
, key
, len
);
211 static int prism2_wep_get_key(void *key
, int len
, u8
* seq
, void *priv
)
213 struct prism2_wep_data
*wep
= priv
;
215 if (len
< wep
->key_len
)
218 memcpy(key
, wep
->key
, wep
->key_len
);
223 static char *prism2_wep_print_stats(char *p
, void *priv
)
225 struct prism2_wep_data
*wep
= priv
;
226 p
+= sprintf(p
, "key[%d] alg=WEP len=%d\n", wep
->key_idx
, wep
->key_len
);
230 static struct ieee80211_crypto_ops ieee80211_crypt_wep
= {
232 .init
= prism2_wep_init
,
233 .deinit
= prism2_wep_deinit
,
234 .encrypt_mpdu
= prism2_wep_encrypt
,
235 .decrypt_mpdu
= prism2_wep_decrypt
,
236 .encrypt_msdu
= NULL
,
237 .decrypt_msdu
= NULL
,
238 .set_key
= prism2_wep_set_key
,
239 .get_key
= prism2_wep_get_key
,
240 .print_stats
= prism2_wep_print_stats
,
241 .extra_mpdu_prefix_len
= 4, /* IV */
242 .extra_mpdu_postfix_len
= 4, /* ICV */
243 .owner
= THIS_MODULE
,
246 static int __init
ieee80211_crypto_wep_init(void)
248 return ieee80211_register_crypto_ops(&ieee80211_crypt_wep
);
251 static void __exit
ieee80211_crypto_wep_exit(void)
253 ieee80211_unregister_crypto_ops(&ieee80211_crypt_wep
);
256 module_init(ieee80211_crypto_wep_init
);
257 module_exit(ieee80211_crypto_wep_exit
);