1 /*
2 * Host AP crypt: host-based WEP encryption implementation for Host AP driver
3 *
4 * Copyright (c) 2002-2004, Jouni Malinen <jkmaline@cc.hut.fi>
5 *
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
9 * more details.
10 */
11
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>
18
19 #include "ieee80211.h"
20
21 #include <crypto/skcipher.h>
22 #include <linux/scatterlist.h>
23 #include <linux/crc32.h>
24
25 MODULE_AUTHOR("Jouni Malinen");
26 MODULE_DESCRIPTION("Host AP crypt: WEP");
27 MODULE_LICENSE("GPL");
28
29 struct prism2_wep_data {
30 u32 iv;
31 #define WEP_KEY_LEN 13
32 u8 key[WEP_KEY_LEN + 1];
33 u8 key_len;
34 u8 key_idx;
35 struct crypto_skcipher *tx_tfm;
36 struct crypto_skcipher *rx_tfm;
37 };
38
39
prism2_wep_init(int keyidx)40 static void *prism2_wep_init(int keyidx)
41 {
42 struct prism2_wep_data *priv;
43
44 priv = kzalloc(sizeof(*priv), GFP_KERNEL);
45 if (!priv)
46 return NULL;
47 priv->key_idx = keyidx;
48
49 priv->tx_tfm = crypto_alloc_skcipher("ecb(arc4)", 0, CRYPTO_ALG_ASYNC);
50 if (IS_ERR(priv->tx_tfm))
51 goto free_priv;
52 priv->rx_tfm = crypto_alloc_skcipher("ecb(arc4)", 0, CRYPTO_ALG_ASYNC);
53 if (IS_ERR(priv->rx_tfm))
54 goto free_tx;
55
56 /* start WEP IV from a random value */
57 get_random_bytes(&priv->iv, 4);
58
59 return priv;
60 free_tx:
61 crypto_free_skcipher(priv->tx_tfm);
62 free_priv:
63 kfree(priv);
64 return NULL;
65 }
66
67
prism2_wep_deinit(void * priv)68 static void prism2_wep_deinit(void *priv)
69 {
70 struct prism2_wep_data *_priv = priv;
71
72 if (_priv) {
73 crypto_free_skcipher(_priv->tx_tfm);
74 crypto_free_skcipher(_priv->rx_tfm);
75 }
76 kfree(priv);
77 }
78
79 /* Perform WEP encryption on given skb that has at least 4 bytes of headroom
80 * for IV and 4 bytes of tailroom for ICV. Both IV and ICV will be transmitted,
81 * so the payload length increases with 8 bytes.
82 *
83 * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data))
84 */
prism2_wep_encrypt(struct sk_buff * skb,int hdr_len,void * priv)85 static int prism2_wep_encrypt(struct sk_buff *skb, int hdr_len, void *priv)
86 {
87 struct prism2_wep_data *wep = priv;
88 u32 klen, len;
89 u8 key[WEP_KEY_LEN + 3];
90 u8 *pos;
91 struct cb_desc *tcb_desc = (struct cb_desc *)(skb->cb + MAX_DEV_ADDR_SIZE);
92 u32 crc;
93 u8 *icv;
94 struct scatterlist sg;
95 int err;
96
97 if (skb_headroom(skb) < 4 || skb_tailroom(skb) < 4 ||
98 skb->len < hdr_len)
99 return -1;
100
101 len = skb->len - hdr_len;
102 pos = skb_push(skb, 4);
103 memmove(pos, pos + 4, hdr_len);
104 pos += hdr_len;
105
106 klen = 3 + wep->key_len;
107
108 wep->iv++;
109
110 /* Fluhrer, Mantin, and Shamir have reported weaknesses in the key
111 * scheduling algorithm of RC4. At least IVs (KeyByte + 3, 0xff, N)
112 * can be used to speedup attacks, so avoid using them.
113 */
114 if ((wep->iv & 0xff00) == 0xff00) {
115 u8 B = (wep->iv >> 16) & 0xff;
116
117 if (B >= 3 && B < klen)
118 wep->iv += 0x0100;
119 }
120
121 /* Prepend 24-bit IV to RC4 key and TX frame */
122 *pos++ = key[0] = (wep->iv >> 16) & 0xff;
123 *pos++ = key[1] = (wep->iv >> 8) & 0xff;
124 *pos++ = key[2] = wep->iv & 0xff;
125 *pos++ = wep->key_idx << 6;
126
127 /* Copy rest of the WEP key (the secret part) */
128 memcpy(key + 3, wep->key, wep->key_len);
129
130 if (!tcb_desc->bHwSec) {
131 SKCIPHER_REQUEST_ON_STACK(req, wep->tx_tfm);
132
133 /* Append little-endian CRC32 and encrypt it to produce ICV */
134 crc = ~crc32_le(~0, pos, len);
135 icv = skb_put(skb, 4);
136 icv[0] = crc;
137 icv[1] = crc >> 8;
138 icv[2] = crc >> 16;
139 icv[3] = crc >> 24;
140
141 crypto_skcipher_setkey(wep->tx_tfm, key, klen);
142 sg_init_one(&sg, pos, len+4);
143
144 skcipher_request_set_tfm(req, wep->tx_tfm);
145 skcipher_request_set_callback(req, 0, NULL, NULL);
146 skcipher_request_set_crypt(req, &sg, &sg, len + 4, NULL);
147
148 err = crypto_skcipher_encrypt(req);
149 skcipher_request_zero(req);
150 return err;
151 }
152
153 return 0;
154 }
155
156
157 /* Perform WEP decryption on given buffer. Buffer includes whole WEP part of
158 * the frame: IV (4 bytes), encrypted payload (including SNAP header),
159 * ICV (4 bytes). len includes both IV and ICV.
160 *
161 * Returns 0 if frame was decrypted successfully and ICV was correct and -1 on
162 * failure. If frame is OK, IV and ICV will be removed.
163 */
prism2_wep_decrypt(struct sk_buff * skb,int hdr_len,void * priv)164 static int prism2_wep_decrypt(struct sk_buff *skb, int hdr_len, void *priv)
165 {
166 struct prism2_wep_data *wep = priv;
167 u32 klen, plen;
168 u8 key[WEP_KEY_LEN + 3];
169 u8 keyidx, *pos;
170 struct cb_desc *tcb_desc = (struct cb_desc *)(skb->cb + MAX_DEV_ADDR_SIZE);
171 u32 crc;
172 u8 icv[4];
173 struct scatterlist sg;
174 int err;
175
176 if (skb->len < hdr_len + 8)
177 return -1;
178
179 pos = skb->data + hdr_len;
180 key[0] = *pos++;
181 key[1] = *pos++;
182 key[2] = *pos++;
183 keyidx = *pos++ >> 6;
184 if (keyidx != wep->key_idx)
185 return -1;
186
187 klen = 3 + wep->key_len;
188
189 /* Copy rest of the WEP key (the secret part) */
190 memcpy(key + 3, wep->key, wep->key_len);
191
192 /* Apply RC4 to data and compute CRC32 over decrypted data */
193 plen = skb->len - hdr_len - 8;
194
195 if (!tcb_desc->bHwSec) {
196 SKCIPHER_REQUEST_ON_STACK(req, wep->rx_tfm);
197
198 crypto_skcipher_setkey(wep->rx_tfm, key, klen);
199 sg_init_one(&sg, pos, plen+4);
200
201 skcipher_request_set_tfm(req, wep->rx_tfm);
202 skcipher_request_set_callback(req, 0, NULL, NULL);
203 skcipher_request_set_crypt(req, &sg, &sg, plen + 4, NULL);
204
205 err = crypto_skcipher_decrypt(req);
206 skcipher_request_zero(req);
207 if (err)
208 return -7;
209
210 crc = ~crc32_le(~0, pos, plen);
211 icv[0] = crc;
212 icv[1] = crc >> 8;
213 icv[2] = crc >> 16;
214 icv[3] = crc >> 24;
215 if (memcmp(icv, pos + plen, 4) != 0) {
216 /* ICV mismatch - drop frame */
217 return -2;
218 }
219 }
220 /* Remove IV and ICV */
221 memmove(skb->data + 4, skb->data, hdr_len);
222 skb_pull(skb, 4);
223 skb_trim(skb, skb->len - 4);
224
225 return 0;
226 }
227
228
prism2_wep_set_key(void * key,int len,u8 * seq,void * priv)229 static int prism2_wep_set_key(void *key, int len, u8 *seq, void *priv)
230 {
231 struct prism2_wep_data *wep = priv;
232
233 if (len < 0 || len > WEP_KEY_LEN)
234 return -1;
235
236 memcpy(wep->key, key, len);
237 wep->key_len = len;
238
239 return 0;
240 }
241
242
prism2_wep_get_key(void * key,int len,u8 * seq,void * priv)243 static int prism2_wep_get_key(void *key, int len, u8 *seq, void *priv)
244 {
245 struct prism2_wep_data *wep = priv;
246
247 if (len < wep->key_len)
248 return -1;
249
250 memcpy(key, wep->key, wep->key_len);
251
252 return wep->key_len;
253 }
254
255
prism2_wep_print_stats(char * p,void * priv)256 static char *prism2_wep_print_stats(char *p, void *priv)
257 {
258 struct prism2_wep_data *wep = priv;
259
260 p += sprintf(p, "key[%d] alg=WEP len=%d\n",
261 wep->key_idx, wep->key_len);
262 return p;
263 }
264
265
266 static struct ieee80211_crypto_ops ieee80211_crypt_wep = {
267 .name = "WEP",
268 .init = prism2_wep_init,
269 .deinit = prism2_wep_deinit,
270 .encrypt_mpdu = prism2_wep_encrypt,
271 .decrypt_mpdu = prism2_wep_decrypt,
272 .encrypt_msdu = NULL,
273 .decrypt_msdu = NULL,
274 .set_key = prism2_wep_set_key,
275 .get_key = prism2_wep_get_key,
276 .print_stats = prism2_wep_print_stats,
277 .extra_prefix_len = 4, /* IV */
278 .extra_postfix_len = 4, /* ICV */
279 .owner = THIS_MODULE,
280 };
281
ieee80211_crypto_wep_init(void)282 int __init ieee80211_crypto_wep_init(void)
283 {
284 return ieee80211_register_crypto_ops(&ieee80211_crypt_wep);
285 }
286
ieee80211_crypto_wep_exit(void)287 void __exit ieee80211_crypto_wep_exit(void)
288 {
289 ieee80211_unregister_crypto_ops(&ieee80211_crypt_wep);
290 }
291
292