2 * lib80211 crypt: host-based WEP encryption implementation for lib80211
4 * Copyright (c) 2002-2004, Jouni Malinen <j@w1.fi>
5 * Copyright (c) 2008, John W. Linville <linville@tuxdriver.com>
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License version 2 as
9 * published by the Free Software Foundation. See README and COPYING for
13 #include <linux/err.h>
14 #include <linux/module.h>
15 #include <linux/init.h>
16 #include <linux/slab.h>
17 #include <linux/random.h>
18 #include <linux/scatterlist.h>
19 #include <linux/skbuff.h>
21 #include <asm/string.h>
23 #include <net/lib80211.h>
25 #include <linux/crypto.h>
26 #include <linux/crc32.h>
28 MODULE_AUTHOR("Jouni Malinen");
29 MODULE_DESCRIPTION("lib80211 crypt: WEP");
30 MODULE_LICENSE("GPL");
32 struct lib80211_wep_data
{
34 #define WEP_KEY_LEN 13
35 u8 key
[WEP_KEY_LEN
+ 1];
38 struct crypto_cipher
*tx_tfm
;
39 struct crypto_cipher
*rx_tfm
;
42 static void *lib80211_wep_init(int keyidx
)
44 struct lib80211_wep_data
*priv
;
46 priv
= kzalloc(sizeof(*priv
), GFP_ATOMIC
);
49 priv
->key_idx
= keyidx
;
51 priv
->tx_tfm
= crypto_alloc_cipher("arc4", 0, 0);
52 if (IS_ERR(priv
->tx_tfm
)) {
57 priv
->rx_tfm
= crypto_alloc_cipher("arc4", 0, 0);
58 if (IS_ERR(priv
->rx_tfm
)) {
62 /* start WEP IV from a random value */
63 get_random_bytes(&priv
->iv
, 4);
69 crypto_free_cipher(priv
->tx_tfm
);
70 crypto_free_cipher(priv
->rx_tfm
);
76 static void lib80211_wep_deinit(void *priv
)
78 struct lib80211_wep_data
*_priv
= priv
;
80 crypto_free_cipher(_priv
->tx_tfm
);
81 crypto_free_cipher(_priv
->rx_tfm
);
86 /* Add WEP IV/key info to a frame that has at least 4 bytes of headroom */
87 static int lib80211_wep_build_iv(struct sk_buff
*skb
, int hdr_len
,
88 u8
*key
, int keylen
, void *priv
)
90 struct lib80211_wep_data
*wep
= priv
;
94 if (skb_headroom(skb
) < 4 || 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
++ = (wep
->iv
>> 16) & 0xff;
116 *pos
++ = (wep
->iv
>> 8) & 0xff;
117 *pos
++ = wep
->iv
& 0xff;
118 *pos
++ = wep
->key_idx
<< 6;
123 /* Perform WEP encryption on given skb that has at least 4 bytes of headroom
124 * for IV and 4 bytes of tailroom for ICV. Both IV and ICV will be transmitted,
125 * so the payload length increases with 8 bytes.
127 * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data))
129 static int lib80211_wep_encrypt(struct sk_buff
*skb
, int hdr_len
, void *priv
)
131 struct lib80211_wep_data
*wep
= priv
;
134 u8 key
[WEP_KEY_LEN
+ 3];
137 /* other checks are in lib80211_wep_build_iv */
138 if (skb_tailroom(skb
) < 4)
141 /* add the IV to the frame */
142 if (lib80211_wep_build_iv(skb
, hdr_len
, NULL
, 0, priv
))
145 /* Copy the IV into the first 3 bytes of the key */
146 skb_copy_from_linear_data_offset(skb
, hdr_len
, key
, 3);
148 /* Copy rest of the WEP key (the secret part) */
149 memcpy(key
+ 3, wep
->key
, wep
->key_len
);
151 len
= skb
->len
- hdr_len
- 4;
152 pos
= skb
->data
+ hdr_len
+ 4;
153 klen
= 3 + wep
->key_len
;
155 /* Append little-endian CRC32 over only the data and encrypt it to produce ICV */
156 crc
= ~crc32_le(~0, pos
, len
);
157 icv
= skb_put(skb
, 4);
163 crypto_cipher_setkey(wep
->tx_tfm
, key
, klen
);
165 for (i
= 0; i
< len
+ 4; i
++)
166 crypto_cipher_encrypt_one(wep
->tx_tfm
, pos
+ i
, pos
+ i
);
171 /* Perform WEP decryption on given buffer. Buffer includes whole WEP part of
172 * the frame: IV (4 bytes), encrypted payload (including SNAP header),
173 * ICV (4 bytes). len includes both IV and ICV.
175 * Returns 0 if frame was decrypted successfully and ICV was correct and -1 on
176 * failure. If frame is OK, IV and ICV will be removed.
178 static int lib80211_wep_decrypt(struct sk_buff
*skb
, int hdr_len
, void *priv
)
180 struct lib80211_wep_data
*wep
= priv
;
182 u8 key
[WEP_KEY_LEN
+ 3];
183 u8 keyidx
, *pos
, icv
[4];
186 if (skb
->len
< hdr_len
+ 8)
189 pos
= skb
->data
+ hdr_len
;
193 keyidx
= *pos
++ >> 6;
194 if (keyidx
!= wep
->key_idx
)
197 klen
= 3 + wep
->key_len
;
199 /* Copy rest of the WEP key (the secret part) */
200 memcpy(key
+ 3, wep
->key
, wep
->key_len
);
202 /* Apply RC4 to data and compute CRC32 over decrypted data */
203 plen
= skb
->len
- hdr_len
- 8;
205 crypto_cipher_setkey(wep
->rx_tfm
, key
, klen
);
206 for (i
= 0; i
< plen
+ 4; i
++)
207 crypto_cipher_decrypt_one(wep
->rx_tfm
, pos
+ i
, pos
+ i
);
209 crc
= ~crc32_le(~0, pos
, plen
);
214 if (memcmp(icv
, pos
+ plen
, 4) != 0) {
215 /* ICV mismatch - drop frame */
219 /* Remove IV and ICV */
220 memmove(skb
->data
+ 4, skb
->data
, hdr_len
);
222 skb_trim(skb
, skb
->len
- 4);
227 static int lib80211_wep_set_key(void *key
, int len
, u8
* seq
, void *priv
)
229 struct lib80211_wep_data
*wep
= priv
;
231 if (len
< 0 || len
> WEP_KEY_LEN
)
234 memcpy(wep
->key
, key
, len
);
240 static int lib80211_wep_get_key(void *key
, int len
, u8
* seq
, void *priv
)
242 struct lib80211_wep_data
*wep
= priv
;
244 if (len
< wep
->key_len
)
247 memcpy(key
, wep
->key
, wep
->key_len
);
252 static void lib80211_wep_print_stats(struct seq_file
*m
, void *priv
)
254 struct lib80211_wep_data
*wep
= priv
;
255 seq_printf(m
, "key[%d] alg=WEP len=%d\n", wep
->key_idx
, wep
->key_len
);
258 static struct lib80211_crypto_ops lib80211_crypt_wep
= {
260 .init
= lib80211_wep_init
,
261 .deinit
= lib80211_wep_deinit
,
262 .encrypt_mpdu
= lib80211_wep_encrypt
,
263 .decrypt_mpdu
= lib80211_wep_decrypt
,
264 .encrypt_msdu
= NULL
,
265 .decrypt_msdu
= NULL
,
266 .set_key
= lib80211_wep_set_key
,
267 .get_key
= lib80211_wep_get_key
,
268 .print_stats
= lib80211_wep_print_stats
,
269 .extra_mpdu_prefix_len
= 4, /* IV */
270 .extra_mpdu_postfix_len
= 4, /* ICV */
271 .owner
= THIS_MODULE
,
274 static int __init
lib80211_crypto_wep_init(void)
276 return lib80211_register_crypto_ops(&lib80211_crypt_wep
);
279 static void __exit
lib80211_crypto_wep_exit(void)
281 lib80211_unregister_crypto_ops(&lib80211_crypt_wep
);
284 module_init(lib80211_crypto_wep_init
);
285 module_exit(lib80211_crypto_wep_exit
);