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 <linux/crypto.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_blkcipher *tx_tfm;
36 struct crypto_blkcipher *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_ATOMIC);
45 if (priv == NULL)
46 return NULL;
47 priv->key_idx = keyidx;
48
49 priv->tx_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0, CRYPTO_ALG_ASYNC);
50 if (IS_ERR(priv->tx_tfm))
51 goto free_priv;
52 priv->rx_tfm = crypto_alloc_blkcipher("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_blkcipher(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 if (_priv->tx_tfm)
74 crypto_free_blkcipher(_priv->tx_tfm);
75 if (_priv->rx_tfm)
76 crypto_free_blkcipher(_priv->rx_tfm);
77 }
78 kfree(priv);
79 }
80
81 /* Perform WEP encryption on given skb that has at least 4 bytes of headroom
82 * for IV and 4 bytes of tailroom for ICV. Both IV and ICV will be transmitted,
83 * so the payload length increases with 8 bytes.
84 *
85 * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data))
86 */
prism2_wep_encrypt(struct sk_buff * skb,int hdr_len,void * priv)87 static int prism2_wep_encrypt(struct sk_buff *skb, int hdr_len, void *priv)
88 {
89 struct prism2_wep_data *wep = priv;
90 u32 klen, len;
91 u8 key[WEP_KEY_LEN + 3];
92 u8 *pos;
93 cb_desc *tcb_desc = (cb_desc *)(skb->cb + MAX_DEV_ADDR_SIZE);
94 struct blkcipher_desc desc = {.tfm = wep->tx_tfm};
95 u32 crc;
96 u8 *icv;
97 struct scatterlist sg;
98
99 if (skb_headroom(skb) < 4 || skb_tailroom(skb) < 4 ||
100 skb->len < hdr_len)
101 return -1;
102
103 len = skb->len - hdr_len;
104 pos = skb_push(skb, 4);
105 memmove(pos, pos + 4, hdr_len);
106 pos += hdr_len;
107
108 klen = 3 + wep->key_len;
109
110 wep->iv++;
111
112 /* Fluhrer, Mantin, and Shamir have reported weaknesses in the key
113 * scheduling algorithm of RC4. At least IVs (KeyByte + 3, 0xff, N)
114 * can be used to speedup attacks, so avoid using them. */
115 if ((wep->iv & 0xff00) == 0xff00) {
116 u8 B = (wep->iv >> 16) & 0xff;
117
118 if (B >= 3 && B < klen)
119 wep->iv += 0x0100;
120 }
121
122 /* Prepend 24-bit IV to RC4 key and TX frame */
123 *pos++ = key[0] = (wep->iv >> 16) & 0xff;
124 *pos++ = key[1] = (wep->iv >> 8) & 0xff;
125 *pos++ = key[2] = wep->iv & 0xff;
126 *pos++ = wep->key_idx << 6;
127
128 /* Copy rest of the WEP key (the secret part) */
129 memcpy(key + 3, wep->key, wep->key_len);
130
131 if (!tcb_desc->bHwSec) {
132 /* Append little-endian CRC32 and encrypt it to produce ICV */
133 crc = ~crc32_le(~0, pos, len);
134 icv = skb_put(skb, 4);
135 icv[0] = crc;
136 icv[1] = crc >> 8;
137 icv[2] = crc >> 16;
138 icv[3] = crc >> 24;
139
140 crypto_blkcipher_setkey(wep->tx_tfm, key, klen);
141 sg_init_one(&sg, pos, len+4);
142
143 return crypto_blkcipher_encrypt(&desc, &sg, &sg, len + 4);
144 }
145
146 return 0;
147 }
148
149
150 /* Perform WEP decryption on given buffer. Buffer includes whole WEP part of
151 * the frame: IV (4 bytes), encrypted payload (including SNAP header),
152 * ICV (4 bytes). len includes both IV and ICV.
153 *
154 * Returns 0 if frame was decrypted successfully and ICV was correct and -1 on
155 * failure. If frame is OK, IV and ICV will be removed.
156 */
prism2_wep_decrypt(struct sk_buff * skb,int hdr_len,void * priv)157 static int prism2_wep_decrypt(struct sk_buff *skb, int hdr_len, void *priv)
158 {
159 struct prism2_wep_data *wep = priv;
160 u32 klen, plen;
161 u8 key[WEP_KEY_LEN + 3];
162 u8 keyidx, *pos;
163 cb_desc *tcb_desc = (cb_desc *)(skb->cb + MAX_DEV_ADDR_SIZE);
164 struct blkcipher_desc desc = {.tfm = wep->rx_tfm};
165 u32 crc;
166 u8 icv[4];
167 struct scatterlist sg;
168
169 if (skb->len < hdr_len + 8)
170 return -1;
171
172 pos = skb->data + hdr_len;
173 key[0] = *pos++;
174 key[1] = *pos++;
175 key[2] = *pos++;
176 keyidx = *pos++ >> 6;
177 if (keyidx != wep->key_idx)
178 return -1;
179
180 klen = 3 + wep->key_len;
181
182 /* Copy rest of the WEP key (the secret part) */
183 memcpy(key + 3, wep->key, wep->key_len);
184
185 /* Apply RC4 to data and compute CRC32 over decrypted data */
186 plen = skb->len - hdr_len - 8;
187
188 if (!tcb_desc->bHwSec) {
189 crypto_blkcipher_setkey(wep->rx_tfm, key, klen);
190 sg_init_one(&sg, pos, plen+4);
191
192 if (crypto_blkcipher_decrypt(&desc, &sg, &sg, plen + 4))
193 return -7;
194
195 crc = ~crc32_le(~0, pos, plen);
196 icv[0] = crc;
197 icv[1] = crc >> 8;
198 icv[2] = crc >> 16;
199 icv[3] = crc >> 24;
200 if (memcmp(icv, pos + plen, 4) != 0) {
201 /* ICV mismatch - drop frame */
202 return -2;
203 }
204 }
205 /* Remove IV and ICV */
206 memmove(skb->data + 4, skb->data, hdr_len);
207 skb_pull(skb, 4);
208 skb_trim(skb, skb->len - 4);
209
210 return 0;
211 }
212
213
prism2_wep_set_key(void * key,int len,u8 * seq,void * priv)214 static int prism2_wep_set_key(void *key, int len, u8 *seq, void *priv)
215 {
216 struct prism2_wep_data *wep = priv;
217
218 if (len < 0 || len > WEP_KEY_LEN)
219 return -1;
220
221 memcpy(wep->key, key, len);
222 wep->key_len = len;
223
224 return 0;
225 }
226
227
prism2_wep_get_key(void * key,int len,u8 * seq,void * priv)228 static int prism2_wep_get_key(void *key, int len, u8 *seq, void *priv)
229 {
230 struct prism2_wep_data *wep = priv;
231
232 if (len < wep->key_len)
233 return -1;
234
235 memcpy(key, wep->key, wep->key_len);
236
237 return wep->key_len;
238 }
239
240
prism2_wep_print_stats(char * p,void * priv)241 static char *prism2_wep_print_stats(char *p, void *priv)
242 {
243 struct prism2_wep_data *wep = priv;
244
245 p += sprintf(p, "key[%d] alg=WEP len=%d\n",
246 wep->key_idx, wep->key_len);
247 return p;
248 }
249
250
251 static struct ieee80211_crypto_ops ieee80211_crypt_wep = {
252 .name = "WEP",
253 .init = prism2_wep_init,
254 .deinit = prism2_wep_deinit,
255 .encrypt_mpdu = prism2_wep_encrypt,
256 .decrypt_mpdu = prism2_wep_decrypt,
257 .encrypt_msdu = NULL,
258 .decrypt_msdu = NULL,
259 .set_key = prism2_wep_set_key,
260 .get_key = prism2_wep_get_key,
261 .print_stats = prism2_wep_print_stats,
262 .extra_prefix_len = 4, /* IV */
263 .extra_postfix_len = 4, /* ICV */
264 .owner = THIS_MODULE,
265 };
266
ieee80211_crypto_wep_init(void)267 int __init ieee80211_crypto_wep_init(void)
268 {
269 return ieee80211_register_crypto_ops(&ieee80211_crypt_wep);
270 }
271
ieee80211_crypto_wep_exit(void)272 void __exit ieee80211_crypto_wep_exit(void)
273 {
274 ieee80211_unregister_crypto_ops(&ieee80211_crypt_wep);
275 }
276
ieee80211_wep_null(void)277 void ieee80211_wep_null(void)
278 {
279 }
280