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 skb_set_network_header(skb, skb_network_offset(skb) +
114 IEEE80211_WEP_IV_LEN);
115 ieee80211_wep_get_iv(local, keylen, keyidx, newhdr + hdrlen);
116 return newhdr + hdrlen;
117 }
118
119
ieee80211_wep_remove_iv(struct ieee80211_local * local,struct sk_buff * skb,struct ieee80211_key * key)120 static void ieee80211_wep_remove_iv(struct ieee80211_local *local,
121 struct sk_buff *skb,
122 struct ieee80211_key *key)
123 {
124 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
125 unsigned int hdrlen;
126
127 hdrlen = ieee80211_hdrlen(hdr->frame_control);
128 memmove(skb->data + IEEE80211_WEP_IV_LEN, skb->data, hdrlen);
129 skb_pull(skb, IEEE80211_WEP_IV_LEN);
130 }
131
132
133 /* Perform WEP encryption using given key. data buffer must have tailroom
134 * for 4-byte ICV. data_len must not include this ICV. Note: this function
135 * 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)136 int ieee80211_wep_encrypt_data(struct crypto_cipher *tfm, u8 *rc4key,
137 size_t klen, u8 *data, size_t data_len)
138 {
139 __le32 icv;
140 int i;
141
142 if (IS_ERR(tfm))
143 return -1;
144
145 icv = cpu_to_le32(~crc32_le(~0, data, data_len));
146 put_unaligned(icv, (__le32 *)(data + data_len));
147
148 crypto_cipher_setkey(tfm, rc4key, klen);
149 for (i = 0; i < data_len + IEEE80211_WEP_ICV_LEN; i++)
150 crypto_cipher_encrypt_one(tfm, data + i, data + i);
151
152 return 0;
153 }
154
155
156 /* Perform WEP encryption on given skb. 4 bytes of extra space (IV) in the
157 * beginning of the buffer 4 bytes of extra space (ICV) in the end of the
158 * buffer will be added. Both IV and ICV will be transmitted, so the
159 * payload length increases with 8 bytes.
160 *
161 * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data))
162 */
ieee80211_wep_encrypt(struct ieee80211_local * local,struct sk_buff * skb,const u8 * key,int keylen,int keyidx)163 int ieee80211_wep_encrypt(struct ieee80211_local *local,
164 struct sk_buff *skb,
165 const u8 *key, int keylen, int keyidx)
166 {
167 u8 *iv;
168 size_t len;
169 u8 rc4key[3 + WLAN_KEY_LEN_WEP104];
170
171 if (WARN_ON(skb_tailroom(skb) < IEEE80211_WEP_ICV_LEN))
172 return -1;
173
174 iv = ieee80211_wep_add_iv(local, skb, keylen, keyidx);
175 if (!iv)
176 return -1;
177
178 len = skb->len - (iv + IEEE80211_WEP_IV_LEN - skb->data);
179
180 /* Prepend 24-bit IV to RC4 key */
181 memcpy(rc4key, iv, 3);
182
183 /* Copy rest of the WEP key (the secret part) */
184 memcpy(rc4key + 3, key, keylen);
185
186 /* Add room for ICV */
187 skb_put(skb, IEEE80211_WEP_ICV_LEN);
188
189 return ieee80211_wep_encrypt_data(local->wep_tx_tfm, rc4key, keylen + 3,
190 iv + IEEE80211_WEP_IV_LEN, len);
191 }
192
193
194 /* Perform WEP decryption using given key. data buffer includes encrypted
195 * payload, including 4-byte ICV, but _not_ IV. data_len must not include ICV.
196 * 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)197 int ieee80211_wep_decrypt_data(struct crypto_cipher *tfm, u8 *rc4key,
198 size_t klen, u8 *data, size_t data_len)
199 {
200 __le32 crc;
201 int i;
202
203 if (IS_ERR(tfm))
204 return -1;
205
206 crypto_cipher_setkey(tfm, rc4key, klen);
207 for (i = 0; i < data_len + IEEE80211_WEP_ICV_LEN; i++)
208 crypto_cipher_decrypt_one(tfm, data + i, data + i);
209
210 crc = cpu_to_le32(~crc32_le(~0, data, data_len));
211 if (memcmp(&crc, data + data_len, IEEE80211_WEP_ICV_LEN) != 0)
212 /* ICV mismatch */
213 return -1;
214
215 return 0;
216 }
217
218
219 /* Perform WEP decryption on given skb. Buffer includes whole WEP part of
220 * the frame: IV (4 bytes), encrypted payload (including SNAP header),
221 * ICV (4 bytes). skb->len includes both IV and ICV.
222 *
223 * Returns 0 if frame was decrypted successfully and ICV was correct and -1 on
224 * failure. If frame is OK, IV and ICV will be removed, i.e., decrypted payload
225 * is moved to the beginning of the skb and skb length will be reduced.
226 */
ieee80211_wep_decrypt(struct ieee80211_local * local,struct sk_buff * skb,struct ieee80211_key * key)227 static int ieee80211_wep_decrypt(struct ieee80211_local *local,
228 struct sk_buff *skb,
229 struct ieee80211_key *key)
230 {
231 u32 klen;
232 u8 rc4key[3 + WLAN_KEY_LEN_WEP104];
233 u8 keyidx;
234 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
235 unsigned int hdrlen;
236 size_t len;
237 int ret = 0;
238
239 if (!ieee80211_has_protected(hdr->frame_control))
240 return -1;
241
242 hdrlen = ieee80211_hdrlen(hdr->frame_control);
243 if (skb->len < hdrlen + IEEE80211_WEP_IV_LEN + IEEE80211_WEP_ICV_LEN)
244 return -1;
245
246 len = skb->len - hdrlen - IEEE80211_WEP_IV_LEN - IEEE80211_WEP_ICV_LEN;
247
248 keyidx = skb->data[hdrlen + 3] >> 6;
249
250 if (!key || keyidx != key->conf.keyidx)
251 return -1;
252
253 klen = 3 + key->conf.keylen;
254
255 /* Prepend 24-bit IV to RC4 key */
256 memcpy(rc4key, skb->data + hdrlen, 3);
257
258 /* Copy rest of the WEP key (the secret part) */
259 memcpy(rc4key + 3, key->conf.key, key->conf.keylen);
260
261 if (ieee80211_wep_decrypt_data(local->wep_rx_tfm, rc4key, klen,
262 skb->data + hdrlen +
263 IEEE80211_WEP_IV_LEN, len))
264 ret = -1;
265
266 /* Trim ICV */
267 skb_trim(skb, skb->len - IEEE80211_WEP_ICV_LEN);
268
269 /* Remove IV */
270 memmove(skb->data + IEEE80211_WEP_IV_LEN, skb->data, hdrlen);
271 skb_pull(skb, IEEE80211_WEP_IV_LEN);
272
273 return ret;
274 }
275
276 ieee80211_rx_result
ieee80211_crypto_wep_decrypt(struct ieee80211_rx_data * rx)277 ieee80211_crypto_wep_decrypt(struct ieee80211_rx_data *rx)
278 {
279 struct sk_buff *skb = rx->skb;
280 struct ieee80211_rx_status *status = IEEE80211_SKB_RXCB(skb);
281 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
282 __le16 fc = hdr->frame_control;
283
284 if (!ieee80211_is_data(fc) && !ieee80211_is_auth(fc))
285 return RX_CONTINUE;
286
287 if (!(status->flag & RX_FLAG_DECRYPTED)) {
288 if (skb_linearize(rx->skb))
289 return RX_DROP_UNUSABLE;
290 if (ieee80211_wep_decrypt(rx->local, rx->skb, rx->key))
291 return RX_DROP_UNUSABLE;
292 } else if (!(status->flag & RX_FLAG_IV_STRIPPED)) {
293 if (!pskb_may_pull(rx->skb, ieee80211_hdrlen(fc) +
294 IEEE80211_WEP_IV_LEN))
295 return RX_DROP_UNUSABLE;
296 ieee80211_wep_remove_iv(rx->local, rx->skb, rx->key);
297 /* remove ICV */
298 if (pskb_trim(rx->skb, rx->skb->len - IEEE80211_WEP_ICV_LEN))
299 return RX_DROP_UNUSABLE;
300 }
301
302 return RX_CONTINUE;
303 }
304
wep_encrypt_skb(struct ieee80211_tx_data * tx,struct sk_buff * skb)305 static int wep_encrypt_skb(struct ieee80211_tx_data *tx, struct sk_buff *skb)
306 {
307 struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
308 struct ieee80211_key_conf *hw_key = info->control.hw_key;
309
310 if (!hw_key) {
311 if (ieee80211_wep_encrypt(tx->local, skb, tx->key->conf.key,
312 tx->key->conf.keylen,
313 tx->key->conf.keyidx))
314 return -1;
315 } else if ((hw_key->flags & IEEE80211_KEY_FLAG_GENERATE_IV) ||
316 (hw_key->flags & IEEE80211_KEY_FLAG_PUT_IV_SPACE)) {
317 if (!ieee80211_wep_add_iv(tx->local, skb,
318 tx->key->conf.keylen,
319 tx->key->conf.keyidx))
320 return -1;
321 }
322
323 return 0;
324 }
325
326 ieee80211_tx_result
ieee80211_crypto_wep_encrypt(struct ieee80211_tx_data * tx)327 ieee80211_crypto_wep_encrypt(struct ieee80211_tx_data *tx)
328 {
329 struct sk_buff *skb;
330
331 ieee80211_tx_set_protected(tx);
332
333 skb_queue_walk(&tx->skbs, skb) {
334 if (wep_encrypt_skb(tx, skb) < 0) {
335 I802_DEBUG_INC(tx->local->tx_handlers_drop_wep);
336 return TX_DROP;
337 }
338 }
339
340 return TX_CONTINUE;
341 }
342