1 /*
2 * Software WEP encryption implementation
3 * Copyright 2002, Jouni Malinen <jkmaline@cc.hut.fi>
4 * Copyright 2003, Instant802 Networks, Inc.
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.
9 */
10
11 #include <linux/netdevice.h>
12 #include <linux/types.h>
13 #include <linux/random.h>
14 #include <linux/compiler.h>
15 #include <linux/crc32.h>
16 #include <linux/crypto.h>
17 #include <linux/err.h>
18 #include <linux/mm.h>
19 #include <linux/scatterlist.h>
20 #include <linux/slab.h>
21 #include <asm/unaligned.h>
22
23 #include <net/mac80211.h>
24 #include "ieee80211_i.h"
25 #include "wep.h"
26
27
ieee80211_wep_init(struct ieee80211_local * local)28 int ieee80211_wep_init(struct ieee80211_local *local)
29 {
30 /* start WEP IV from a random value */
31 get_random_bytes(&local->wep_iv, IEEE80211_WEP_IV_LEN);
32
33 local->wep_tx_tfm = crypto_alloc_cipher("arc4", 0, CRYPTO_ALG_ASYNC);
34 if (IS_ERR(local->wep_tx_tfm)) {
35 local->wep_rx_tfm = ERR_PTR(-EINVAL);
36 return PTR_ERR(local->wep_tx_tfm);
37 }
38
39 local->wep_rx_tfm = crypto_alloc_cipher("arc4", 0, CRYPTO_ALG_ASYNC);
40 if (IS_ERR(local->wep_rx_tfm)) {
41 crypto_free_cipher(local->wep_tx_tfm);
42 local->wep_tx_tfm = ERR_PTR(-EINVAL);
43 return PTR_ERR(local->wep_rx_tfm);
44 }
45
46 return 0;
47 }
48
ieee80211_wep_free(struct ieee80211_local * local)49 void ieee80211_wep_free(struct ieee80211_local *local)
50 {
51 if (!IS_ERR(local->wep_tx_tfm))
52 crypto_free_cipher(local->wep_tx_tfm);
53 if (!IS_ERR(local->wep_rx_tfm))
54 crypto_free_cipher(local->wep_rx_tfm);
55 }
56
ieee80211_wep_weak_iv(u32 iv,int keylen)57 static inline bool ieee80211_wep_weak_iv(u32 iv, int keylen)
58 {
59 /*
60 * Fluhrer, Mantin, and Shamir have reported weaknesses in the
61 * key scheduling algorithm of RC4. At least IVs (KeyByte + 3,
62 * 0xff, N) can be used to speedup attacks, so avoid using them.
63 */
64 if ((iv & 0xff00) == 0xff00) {
65 u8 B = (iv >> 16) & 0xff;
66 if (B >= 3 && B < 3 + keylen)
67 return true;
68 }
69 return false;
70 }
71
72
ieee80211_wep_get_iv(struct ieee80211_local * local,int keylen,int keyidx,u8 * iv)73 static void ieee80211_wep_get_iv(struct ieee80211_local *local,
74 int keylen, int keyidx, u8 *iv)
75 {
76 local->wep_iv++;
77 if (ieee80211_wep_weak_iv(local->wep_iv, keylen))
78 local->wep_iv += 0x0100;
79
80 if (!iv)
81 return;
82
83 *iv++ = (local->wep_iv >> 16) & 0xff;
84 *iv++ = (local->wep_iv >> 8) & 0xff;
85 *iv++ = local->wep_iv & 0xff;
86 *iv++ = keyidx << 6;
87 }
88
89
ieee80211_wep_add_iv(struct ieee80211_local * local,struct sk_buff * skb,int keylen,int keyidx)90 static u8 *ieee80211_wep_add_iv(struct ieee80211_local *local,
91 struct sk_buff *skb,
92 int keylen, int keyidx)
93 {
94 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
95 struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
96 unsigned int hdrlen;
97 u8 *newhdr;
98
99 hdr->frame_control |= cpu_to_le16(IEEE80211_FCTL_PROTECTED);
100
101 if (WARN_ON(skb_headroom(skb) < IEEE80211_WEP_IV_LEN))
102 return NULL;
103
104 hdrlen = ieee80211_hdrlen(hdr->frame_control);
105 newhdr = skb_push(skb, IEEE80211_WEP_IV_LEN);
106 memmove(newhdr, newhdr + IEEE80211_WEP_IV_LEN, hdrlen);
107
108 /* the HW only needs room for the IV, but not the actual IV */
109 if (info->control.hw_key &&
110 (info->control.hw_key->flags & IEEE80211_KEY_FLAG_PUT_IV_SPACE))
111 return newhdr + hdrlen;
112
113 ieee80211_wep_get_iv(local, keylen, keyidx, newhdr + hdrlen);
114 return newhdr + hdrlen;
115 }
116
117
ieee80211_wep_remove_iv(struct ieee80211_local * local,struct sk_buff * skb,struct ieee80211_key * key)118 static void ieee80211_wep_remove_iv(struct ieee80211_local *local,
119 struct sk_buff *skb,
120 struct ieee80211_key *key)
121 {
122 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
123 unsigned int hdrlen;
124
125 hdrlen = ieee80211_hdrlen(hdr->frame_control);
126 memmove(skb->data + IEEE80211_WEP_IV_LEN, skb->data, hdrlen);
127 skb_pull(skb, IEEE80211_WEP_IV_LEN);
128 }
129
130
131 /* Perform WEP encryption using given key. data buffer must have tailroom
132 * for 4-byte ICV. data_len must not include this ICV. Note: this function
133 * does _not_ add IV. data = RC4(data | CRC32(data)) */
ieee80211_wep_encrypt_data(struct crypto_cipher * tfm,u8 * rc4key,size_t klen,u8 * data,size_t data_len)134 int ieee80211_wep_encrypt_data(struct crypto_cipher *tfm, u8 *rc4key,
135 size_t klen, u8 *data, size_t data_len)
136 {
137 __le32 icv;
138 int i;
139
140 if (IS_ERR(tfm))
141 return -1;
142
143 icv = cpu_to_le32(~crc32_le(~0, data, data_len));
144 put_unaligned(icv, (__le32 *)(data + data_len));
145
146 crypto_cipher_setkey(tfm, rc4key, klen);
147 for (i = 0; i < data_len + IEEE80211_WEP_ICV_LEN; i++)
148 crypto_cipher_encrypt_one(tfm, data + i, data + i);
149
150 return 0;
151 }
152
153
154 /* Perform WEP encryption on given skb. 4 bytes of extra space (IV) in the
155 * beginning of the buffer 4 bytes of extra space (ICV) in the end of the
156 * buffer will be added. Both IV and ICV will be transmitted, so the
157 * payload length increases with 8 bytes.
158 *
159 * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data))
160 */
ieee80211_wep_encrypt(struct ieee80211_local * local,struct sk_buff * skb,const u8 * key,int keylen,int keyidx)161 int ieee80211_wep_encrypt(struct ieee80211_local *local,
162 struct sk_buff *skb,
163 const u8 *key, int keylen, int keyidx)
164 {
165 u8 *iv;
166 size_t len;
167 u8 rc4key[3 + WLAN_KEY_LEN_WEP104];
168
169 if (WARN_ON(skb_tailroom(skb) < IEEE80211_WEP_ICV_LEN))
170 return -1;
171
172 iv = ieee80211_wep_add_iv(local, skb, keylen, keyidx);
173 if (!iv)
174 return -1;
175
176 len = skb->len - (iv + IEEE80211_WEP_IV_LEN - skb->data);
177
178 /* Prepend 24-bit IV to RC4 key */
179 memcpy(rc4key, iv, 3);
180
181 /* Copy rest of the WEP key (the secret part) */
182 memcpy(rc4key + 3, key, keylen);
183
184 /* Add room for ICV */
185 skb_put(skb, IEEE80211_WEP_ICV_LEN);
186
187 return ieee80211_wep_encrypt_data(local->wep_tx_tfm, rc4key, keylen + 3,
188 iv + IEEE80211_WEP_IV_LEN, len);
189 }
190
191
192 /* Perform WEP decryption using given key. data buffer includes encrypted
193 * payload, including 4-byte ICV, but _not_ IV. data_len must not include ICV.
194 * Return 0 on success and -1 on ICV mismatch. */
ieee80211_wep_decrypt_data(struct crypto_cipher * tfm,u8 * rc4key,size_t klen,u8 * data,size_t data_len)195 int ieee80211_wep_decrypt_data(struct crypto_cipher *tfm, u8 *rc4key,
196 size_t klen, u8 *data, size_t data_len)
197 {
198 __le32 crc;
199 int i;
200
201 if (IS_ERR(tfm))
202 return -1;
203
204 crypto_cipher_setkey(tfm, rc4key, klen);
205 for (i = 0; i < data_len + IEEE80211_WEP_ICV_LEN; i++)
206 crypto_cipher_decrypt_one(tfm, data + i, data + i);
207
208 crc = cpu_to_le32(~crc32_le(~0, data, data_len));
209 if (memcmp(&crc, data + data_len, IEEE80211_WEP_ICV_LEN) != 0)
210 /* ICV mismatch */
211 return -1;
212
213 return 0;
214 }
215
216
217 /* Perform WEP decryption on given skb. Buffer includes whole WEP part of
218 * the frame: IV (4 bytes), encrypted payload (including SNAP header),
219 * ICV (4 bytes). skb->len includes both IV and ICV.
220 *
221 * Returns 0 if frame was decrypted successfully and ICV was correct and -1 on
222 * failure. If frame is OK, IV and ICV will be removed, i.e., decrypted payload
223 * is moved to the beginning of the skb and skb length will be reduced.
224 */
ieee80211_wep_decrypt(struct ieee80211_local * local,struct sk_buff * skb,struct ieee80211_key * key)225 static int ieee80211_wep_decrypt(struct ieee80211_local *local,
226 struct sk_buff *skb,
227 struct ieee80211_key *key)
228 {
229 u32 klen;
230 u8 rc4key[3 + WLAN_KEY_LEN_WEP104];
231 u8 keyidx;
232 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
233 unsigned int hdrlen;
234 size_t len;
235 int ret = 0;
236
237 if (!ieee80211_has_protected(hdr->frame_control))
238 return -1;
239
240 hdrlen = ieee80211_hdrlen(hdr->frame_control);
241 if (skb->len < hdrlen + IEEE80211_WEP_IV_LEN + IEEE80211_WEP_ICV_LEN)
242 return -1;
243
244 len = skb->len - hdrlen - IEEE80211_WEP_IV_LEN - IEEE80211_WEP_ICV_LEN;
245
246 keyidx = skb->data[hdrlen + 3] >> 6;
247
248 if (!key || keyidx != key->conf.keyidx)
249 return -1;
250
251 klen = 3 + key->conf.keylen;
252
253 /* Prepend 24-bit IV to RC4 key */
254 memcpy(rc4key, skb->data + hdrlen, 3);
255
256 /* Copy rest of the WEP key (the secret part) */
257 memcpy(rc4key + 3, key->conf.key, key->conf.keylen);
258
259 if (ieee80211_wep_decrypt_data(local->wep_rx_tfm, rc4key, klen,
260 skb->data + hdrlen +
261 IEEE80211_WEP_IV_LEN, len))
262 ret = -1;
263
264 /* Trim ICV */
265 skb_trim(skb, skb->len - IEEE80211_WEP_ICV_LEN);
266
267 /* Remove IV */
268 memmove(skb->data + IEEE80211_WEP_IV_LEN, skb->data, hdrlen);
269 skb_pull(skb, IEEE80211_WEP_IV_LEN);
270
271 return ret;
272 }
273
274 ieee80211_rx_result
ieee80211_crypto_wep_decrypt(struct ieee80211_rx_data * rx)275 ieee80211_crypto_wep_decrypt(struct ieee80211_rx_data *rx)
276 {
277 struct sk_buff *skb = rx->skb;
278 struct ieee80211_rx_status *status = IEEE80211_SKB_RXCB(skb);
279 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
280 __le16 fc = hdr->frame_control;
281
282 if (!ieee80211_is_data(fc) && !ieee80211_is_auth(fc))
283 return RX_CONTINUE;
284
285 if (!(status->flag & RX_FLAG_DECRYPTED)) {
286 if (skb_linearize(rx->skb))
287 return RX_DROP_UNUSABLE;
288 if (ieee80211_wep_decrypt(rx->local, rx->skb, rx->key))
289 return RX_DROP_UNUSABLE;
290 } else if (!(status->flag & RX_FLAG_IV_STRIPPED)) {
291 if (!pskb_may_pull(rx->skb, ieee80211_hdrlen(fc) +
292 IEEE80211_WEP_IV_LEN))
293 return RX_DROP_UNUSABLE;
294 ieee80211_wep_remove_iv(rx->local, rx->skb, rx->key);
295 /* remove ICV */
296 if (!(status->flag & RX_FLAG_ICV_STRIPPED) &&
297 pskb_trim(rx->skb, rx->skb->len - IEEE80211_WEP_ICV_LEN))
298 return RX_DROP_UNUSABLE;
299 }
300
301 return RX_CONTINUE;
302 }
303
wep_encrypt_skb(struct ieee80211_tx_data * tx,struct sk_buff * skb)304 static int wep_encrypt_skb(struct ieee80211_tx_data *tx, struct sk_buff *skb)
305 {
306 struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
307 struct ieee80211_key_conf *hw_key = info->control.hw_key;
308
309 if (!hw_key) {
310 if (ieee80211_wep_encrypt(tx->local, skb, tx->key->conf.key,
311 tx->key->conf.keylen,
312 tx->key->conf.keyidx))
313 return -1;
314 } else if ((hw_key->flags & IEEE80211_KEY_FLAG_GENERATE_IV) ||
315 (hw_key->flags & IEEE80211_KEY_FLAG_PUT_IV_SPACE)) {
316 if (!ieee80211_wep_add_iv(tx->local, skb,
317 tx->key->conf.keylen,
318 tx->key->conf.keyidx))
319 return -1;
320 }
321
322 return 0;
323 }
324
325 ieee80211_tx_result
ieee80211_crypto_wep_encrypt(struct ieee80211_tx_data * tx)326 ieee80211_crypto_wep_encrypt(struct ieee80211_tx_data *tx)
327 {
328 struct sk_buff *skb;
329
330 ieee80211_tx_set_protected(tx);
331
332 skb_queue_walk(&tx->skbs, skb) {
333 if (wep_encrypt_skb(tx, skb) < 0) {
334 I802_DEBUG_INC(tx->local->tx_handlers_drop_wep);
335 return TX_DROP;
336 }
337 }
338
339 return TX_CONTINUE;
340 }
341
