1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Host AP crypt: host-based WEP encryption implementation for Host AP driver
4 *
5 * Copyright (c) 2002-2004, Jouni Malinen <jkmaline@cc.hut.fi>
6 */
7
8 #include <linux/module.h>
9 #include <linux/init.h>
10 #include <linux/slab.h>
11 #include <linux/random.h>
12 #include <linux/skbuff.h>
13 #include <linux/string.h>
14
15 #include "ieee80211.h"
16
17 #include <crypto/skcipher.h>
18 #include <linux/scatterlist.h>
19 #include <linux/crc32.h>
20
21 MODULE_AUTHOR("Jouni Malinen");
22 MODULE_DESCRIPTION("Host AP crypt: WEP");
23 MODULE_LICENSE("GPL");
24
25 struct prism2_wep_data {
26 u32 iv;
27 #define WEP_KEY_LEN 13
28 u8 key[WEP_KEY_LEN + 1];
29 u8 key_len;
30 u8 key_idx;
31 struct crypto_sync_skcipher *tx_tfm;
32 struct crypto_sync_skcipher *rx_tfm;
33 };
34
35
prism2_wep_init(int keyidx)36 static void *prism2_wep_init(int keyidx)
37 {
38 struct prism2_wep_data *priv;
39
40 priv = kzalloc(sizeof(*priv), GFP_KERNEL);
41 if (!priv)
42 return NULL;
43 priv->key_idx = keyidx;
44
45 priv->tx_tfm = crypto_alloc_sync_skcipher("ecb(arc4)", 0, 0);
46 if (IS_ERR(priv->tx_tfm))
47 goto free_priv;
48 priv->rx_tfm = crypto_alloc_sync_skcipher("ecb(arc4)", 0, 0);
49 if (IS_ERR(priv->rx_tfm))
50 goto free_tx;
51
52 /* start WEP IV from a random value */
53 get_random_bytes(&priv->iv, 4);
54
55 return priv;
56 free_tx:
57 crypto_free_sync_skcipher(priv->tx_tfm);
58 free_priv:
59 kfree(priv);
60 return NULL;
61 }
62
63
prism2_wep_deinit(void * priv)64 static void prism2_wep_deinit(void *priv)
65 {
66 struct prism2_wep_data *_priv = priv;
67
68 if (_priv) {
69 crypto_free_sync_skcipher(_priv->tx_tfm);
70 crypto_free_sync_skcipher(_priv->rx_tfm);
71 }
72 kfree(priv);
73 }
74
75 /* Perform WEP encryption on given skb that has at least 4 bytes of headroom
76 * for IV and 4 bytes of tailroom for ICV. Both IV and ICV will be transmitted,
77 * so the payload length increases with 8 bytes.
78 *
79 * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data))
80 */
prism2_wep_encrypt(struct sk_buff * skb,int hdr_len,void * priv)81 static int prism2_wep_encrypt(struct sk_buff *skb, int hdr_len, void *priv)
82 {
83 struct prism2_wep_data *wep = priv;
84 u32 klen, len;
85 u8 key[WEP_KEY_LEN + 3];
86 u8 *pos;
87 struct cb_desc *tcb_desc = (struct cb_desc *)(skb->cb + MAX_DEV_ADDR_SIZE);
88 u32 crc;
89 u8 *icv;
90 struct scatterlist sg;
91 int err;
92
93 if (skb_headroom(skb) < 4 || skb_tailroom(skb) < 4 ||
94 skb->len < hdr_len)
95 return -1;
96
97 len = skb->len - hdr_len;
98 pos = skb_push(skb, 4);
99 memmove(pos, pos + 4, hdr_len);
100 pos += hdr_len;
101
102 klen = 3 + wep->key_len;
103
104 wep->iv++;
105
106 /* Fluhrer, Mantin, and Shamir have reported weaknesses in the key
107 * scheduling algorithm of RC4. At least IVs (KeyByte + 3, 0xff, N)
108 * can be used to speedup attacks, so avoid using them.
109 */
110 if ((wep->iv & 0xff00) == 0xff00) {
111 u8 B = (wep->iv >> 16) & 0xff;
112
113 if (B >= 3 && B < klen)
114 wep->iv += 0x0100;
115 }
116
117 /* Prepend 24-bit IV to RC4 key and TX frame */
118 *pos++ = key[0] = (wep->iv >> 16) & 0xff;
119 *pos++ = key[1] = (wep->iv >> 8) & 0xff;
120 *pos++ = key[2] = wep->iv & 0xff;
121 *pos++ = wep->key_idx << 6;
122
123 /* Copy rest of the WEP key (the secret part) */
124 memcpy(key + 3, wep->key, wep->key_len);
125
126 if (!tcb_desc->bHwSec) {
127 SYNC_SKCIPHER_REQUEST_ON_STACK(req, wep->tx_tfm);
128
129 /* Append little-endian CRC32 and encrypt it to produce ICV */
130 crc = ~crc32_le(~0, pos, len);
131 icv = skb_put(skb, 4);
132 icv[0] = crc;
133 icv[1] = crc >> 8;
134 icv[2] = crc >> 16;
135 icv[3] = crc >> 24;
136
137 crypto_sync_skcipher_setkey(wep->tx_tfm, key, klen);
138 sg_init_one(&sg, pos, len + 4);
139
140 skcipher_request_set_sync_tfm(req, wep->tx_tfm);
141 skcipher_request_set_callback(req, 0, NULL, NULL);
142 skcipher_request_set_crypt(req, &sg, &sg, len + 4, NULL);
143
144 err = crypto_skcipher_encrypt(req);
145 skcipher_request_zero(req);
146 return err;
147 }
148
149 return 0;
150 }
151
152
153 /* Perform WEP decryption on given buffer. Buffer includes whole WEP part of
154 * the frame: IV (4 bytes), encrypted payload (including SNAP header),
155 * ICV (4 bytes). len includes both IV and ICV.
156 *
157 * Returns 0 if frame was decrypted successfully and ICV was correct and -1 on
158 * failure. If frame is OK, IV and ICV will be removed.
159 */
prism2_wep_decrypt(struct sk_buff * skb,int hdr_len,void * priv)160 static int prism2_wep_decrypt(struct sk_buff *skb, int hdr_len, void *priv)
161 {
162 struct prism2_wep_data *wep = priv;
163 u32 klen, plen;
164 u8 key[WEP_KEY_LEN + 3];
165 u8 keyidx, *pos;
166 struct cb_desc *tcb_desc = (struct cb_desc *)(skb->cb + MAX_DEV_ADDR_SIZE);
167 u32 crc;
168 u8 icv[4];
169 struct scatterlist sg;
170 int err;
171
172 if (skb->len < hdr_len + 8)
173 return -1;
174
175 pos = skb->data + hdr_len;
176 key[0] = *pos++;
177 key[1] = *pos++;
178 key[2] = *pos++;
179 keyidx = *pos++ >> 6;
180 if (keyidx != wep->key_idx)
181 return -1;
182
183 klen = 3 + wep->key_len;
184
185 /* Copy rest of the WEP key (the secret part) */
186 memcpy(key + 3, wep->key, wep->key_len);
187
188 /* Apply RC4 to data and compute CRC32 over decrypted data */
189 plen = skb->len - hdr_len - 8;
190
191 if (!tcb_desc->bHwSec) {
192 SYNC_SKCIPHER_REQUEST_ON_STACK(req, wep->rx_tfm);
193
194 crypto_sync_skcipher_setkey(wep->rx_tfm, key, klen);
195 sg_init_one(&sg, pos, plen + 4);
196
197 skcipher_request_set_sync_tfm(req, wep->rx_tfm);
198 skcipher_request_set_callback(req, 0, NULL, NULL);
199 skcipher_request_set_crypt(req, &sg, &sg, plen + 4, NULL);
200
201 err = crypto_skcipher_decrypt(req);
202 skcipher_request_zero(req);
203 if (err)
204 return -7;
205
206 crc = ~crc32_le(~0, pos, plen);
207 icv[0] = crc;
208 icv[1] = crc >> 8;
209 icv[2] = crc >> 16;
210 icv[3] = crc >> 24;
211 if (memcmp(icv, pos + plen, 4) != 0) {
212 /* ICV mismatch - drop frame */
213 return -2;
214 }
215 }
216 /* Remove IV and ICV */
217 memmove(skb->data + 4, skb->data, hdr_len);
218 skb_pull(skb, 4);
219 skb_trim(skb, skb->len - 4);
220
221 return 0;
222 }
223
224
prism2_wep_set_key(void * key,int len,u8 * seq,void * priv)225 static int prism2_wep_set_key(void *key, int len, u8 *seq, void *priv)
226 {
227 struct prism2_wep_data *wep = priv;
228
229 if (len < 0 || len > WEP_KEY_LEN)
230 return -1;
231
232 memcpy(wep->key, key, len);
233 wep->key_len = len;
234
235 return 0;
236 }
237
238
prism2_wep_get_key(void * key,int len,u8 * seq,void * priv)239 static int prism2_wep_get_key(void *key, int len, u8 *seq, void *priv)
240 {
241 struct prism2_wep_data *wep = priv;
242
243 if (len < wep->key_len)
244 return -1;
245
246 memcpy(key, wep->key, wep->key_len);
247
248 return wep->key_len;
249 }
250
251
prism2_wep_print_stats(char * p,void * priv)252 static char *prism2_wep_print_stats(char *p, void *priv)
253 {
254 struct prism2_wep_data *wep = priv;
255
256 p += sprintf(p, "key[%d] alg=WEP len=%d\n",
257 wep->key_idx, wep->key_len);
258 return p;
259 }
260
261
262 static struct ieee80211_crypto_ops ieee80211_crypt_wep = {
263 .name = "WEP",
264 .init = prism2_wep_init,
265 .deinit = prism2_wep_deinit,
266 .encrypt_mpdu = prism2_wep_encrypt,
267 .decrypt_mpdu = prism2_wep_decrypt,
268 .encrypt_msdu = NULL,
269 .decrypt_msdu = NULL,
270 .set_key = prism2_wep_set_key,
271 .get_key = prism2_wep_get_key,
272 .print_stats = prism2_wep_print_stats,
273 .extra_prefix_len = 4, /* IV */
274 .extra_postfix_len = 4, /* ICV */
275 .owner = THIS_MODULE,
276 };
277
ieee80211_crypto_wep_init(void)278 int __init ieee80211_crypto_wep_init(void)
279 {
280 return ieee80211_register_crypto_ops(&ieee80211_crypt_wep);
281 }
282
ieee80211_crypto_wep_exit(void)283 void __exit ieee80211_crypto_wep_exit(void)
284 {
285 ieee80211_unregister_crypto_ops(&ieee80211_crypt_wep);
286 }
287
288
