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/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>
19
20 #include "ieee80211.h"
21
22 #include <linux/crypto.h>
23 #include <linux/scatterlist.h>
24 #include <linux/crc32.h>
25
26 MODULE_AUTHOR("Jouni Malinen");
27 MODULE_DESCRIPTION("Host AP crypt: WEP");
28 MODULE_LICENSE("GPL");
29
30 struct prism2_wep_data {
31 u32 iv;
32 #define WEP_KEY_LEN 13
33 u8 key[WEP_KEY_LEN + 1];
34 u8 key_len;
35 u8 key_idx;
36 struct crypto_blkcipher *tx_tfm;
37 struct crypto_blkcipher *rx_tfm;
38 };
39
40
prism2_wep_init(int keyidx)41 static void *prism2_wep_init(int keyidx)
42 {
43 struct prism2_wep_data *priv;
44
45 priv = kzalloc(sizeof(*priv), GFP_ATOMIC);
46 if (priv == NULL)
47 goto fail;
48 priv->key_idx = keyidx;
49
50 priv->tx_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0, CRYPTO_ALG_ASYNC);
51 if (IS_ERR(priv->tx_tfm)) {
52 printk(KERN_DEBUG "ieee80211_crypt_wep: could not allocate "
53 "crypto API arc4\n");
54 priv->tx_tfm = NULL;
55 goto fail;
56 }
57 priv->rx_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0, CRYPTO_ALG_ASYNC);
58 if (IS_ERR(priv->rx_tfm)) {
59 printk(KERN_DEBUG "ieee80211_crypt_wep: could not allocate "
60 "crypto API arc4\n");
61 priv->rx_tfm = NULL;
62 goto fail;
63 }
64
65 /* start WEP IV from a random value */
66 get_random_bytes(&priv->iv, 4);
67
68 return priv;
69
70 fail:
71 if (priv) {
72 if (priv->tx_tfm)
73 crypto_free_blkcipher(priv->tx_tfm);
74 if (priv->rx_tfm)
75 crypto_free_blkcipher(priv->rx_tfm);
76 kfree(priv);
77 }
78
79 return NULL;
80 }
81
82
prism2_wep_deinit(void * priv)83 static void prism2_wep_deinit(void *priv)
84 {
85 struct prism2_wep_data *_priv = priv;
86
87 if (_priv) {
88 if (_priv->tx_tfm)
89 crypto_free_blkcipher(_priv->tx_tfm);
90 if (_priv->rx_tfm)
91 crypto_free_blkcipher(_priv->rx_tfm);
92 }
93 kfree(priv);
94 }
95
96 /* Perform WEP encryption on given skb that has at least 4 bytes of headroom
97 * for IV and 4 bytes of tailroom for ICV. Both IV and ICV will be transmitted,
98 * so the payload length increases with 8 bytes.
99 *
100 * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data))
101 */
prism2_wep_encrypt(struct sk_buff * skb,int hdr_len,void * priv)102 static int prism2_wep_encrypt(struct sk_buff *skb, int hdr_len, void *priv)
103 {
104 struct prism2_wep_data *wep = priv;
105 u32 klen, len;
106 u8 key[WEP_KEY_LEN + 3];
107 u8 *pos;
108 cb_desc *tcb_desc = (cb_desc *)(skb->cb + MAX_DEV_ADDR_SIZE);
109 struct blkcipher_desc desc = {.tfm = wep->tx_tfm};
110 u32 crc;
111 u8 *icv;
112 struct scatterlist sg;
113 if (skb_headroom(skb) < 4 || skb_tailroom(skb) < 4 ||
114 skb->len < hdr_len)
115 return -1;
116
117 len = skb->len - hdr_len;
118 pos = skb_push(skb, 4);
119 memmove(pos, pos + 4, hdr_len);
120 pos += hdr_len;
121
122 klen = 3 + wep->key_len;
123
124 wep->iv++;
125
126 /* Fluhrer, Mantin, and Shamir have reported weaknesses in the key
127 * scheduling algorithm of RC4. At least IVs (KeyByte + 3, 0xff, N)
128 * can be used to speedup attacks, so avoid using them. */
129 if ((wep->iv & 0xff00) == 0xff00) {
130 u8 B = (wep->iv >> 16) & 0xff;
131 if (B >= 3 && B < klen)
132 wep->iv += 0x0100;
133 }
134
135 /* Prepend 24-bit IV to RC4 key and TX frame */
136 *pos++ = key[0] = (wep->iv >> 16) & 0xff;
137 *pos++ = key[1] = (wep->iv >> 8) & 0xff;
138 *pos++ = key[2] = wep->iv & 0xff;
139 *pos++ = wep->key_idx << 6;
140
141 /* Copy rest of the WEP key (the secret part) */
142 memcpy(key + 3, wep->key, wep->key_len);
143
144 if (!tcb_desc->bHwSec)
145 {
146
147 /* Append little-endian CRC32 and encrypt it to produce ICV */
148 crc = ~crc32_le(~0, pos, len);
149 icv = skb_put(skb, 4);
150 icv[0] = crc;
151 icv[1] = crc >> 8;
152 icv[2] = crc >> 16;
153 icv[3] = crc >> 24;
154
155 crypto_blkcipher_setkey(wep->tx_tfm, key, klen);
156 sg_init_one(&sg, pos, len+4);
157
158 return crypto_blkcipher_encrypt(&desc, &sg, &sg, len + 4);
159 }
160
161 return 0;
162 }
163
164
165 /* Perform WEP decryption on given buffer. Buffer includes whole WEP part of
166 * the frame: IV (4 bytes), encrypted payload (including SNAP header),
167 * ICV (4 bytes). len includes both IV and ICV.
168 *
169 * Returns 0 if frame was decrypted successfully and ICV was correct and -1 on
170 * failure. If frame is OK, IV and ICV will be removed.
171 */
prism2_wep_decrypt(struct sk_buff * skb,int hdr_len,void * priv)172 static int prism2_wep_decrypt(struct sk_buff *skb, int hdr_len, void *priv)
173 {
174 struct prism2_wep_data *wep = priv;
175 u32 klen, plen;
176 u8 key[WEP_KEY_LEN + 3];
177 u8 keyidx, *pos;
178 cb_desc *tcb_desc = (cb_desc *)(skb->cb + MAX_DEV_ADDR_SIZE);
179 struct blkcipher_desc desc = {.tfm = wep->rx_tfm};
180 u32 crc;
181 u8 icv[4];
182 struct scatterlist sg;
183 if (skb->len < hdr_len + 8)
184 return -1;
185
186 pos = skb->data + hdr_len;
187 key[0] = *pos++;
188 key[1] = *pos++;
189 key[2] = *pos++;
190 keyidx = *pos++ >> 6;
191 if (keyidx != wep->key_idx)
192 return -1;
193
194 klen = 3 + wep->key_len;
195
196 /* Copy rest of the WEP key (the secret part) */
197 memcpy(key + 3, wep->key, wep->key_len);
198
199 /* Apply RC4 to data and compute CRC32 over decrypted data */
200 plen = skb->len - hdr_len - 8;
201
202 if (!tcb_desc->bHwSec)
203 {
204 crypto_blkcipher_setkey(wep->rx_tfm, key, klen);
205 sg_init_one(&sg, pos, plen+4);
206
207 if (crypto_blkcipher_decrypt(&desc, &sg, &sg, plen + 4))
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 p += sprintf(p, "key[%d] alg=WEP len=%d\n",
260 wep->key_idx, wep->key_len);
261 return p;
262 }
263
264
265 static struct ieee80211_crypto_ops ieee80211_crypt_wep = {
266 .name = "WEP",
267 .init = prism2_wep_init,
268 .deinit = prism2_wep_deinit,
269 .encrypt_mpdu = prism2_wep_encrypt,
270 .decrypt_mpdu = prism2_wep_decrypt,
271 .encrypt_msdu = NULL,
272 .decrypt_msdu = NULL,
273 .set_key = prism2_wep_set_key,
274 .get_key = prism2_wep_get_key,
275 .print_stats = prism2_wep_print_stats,
276 .extra_prefix_len = 4, /* IV */
277 .extra_postfix_len = 4, /* ICV */
278 .owner = THIS_MODULE,
279 };
280
ieee80211_crypto_wep_init(void)281 int __init ieee80211_crypto_wep_init(void)
282 {
283 return ieee80211_register_crypto_ops(&ieee80211_crypt_wep);
284 }
285
ieee80211_crypto_wep_exit(void)286 void __exit ieee80211_crypto_wep_exit(void)
287 {
288 ieee80211_unregister_crypto_ops(&ieee80211_crypt_wep);
289 }
290
ieee80211_wep_null(void)291 void ieee80211_wep_null(void)
292 {
293 // printk("============>%s()\n", __func__);
294 return;
295 }
296