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Jiri Bencf0706e82007-05-05 11:45:53 -07001/*
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>
Ralf Baechle11763602007-10-23 20:42:11 +020019#include <linux/scatterlist.h>
Jiri Bencf0706e82007-05-05 11:45:53 -070020
21#include <net/mac80211.h>
22#include "ieee80211_i.h"
23#include "wep.h"
24
25
26int ieee80211_wep_init(struct ieee80211_local *local)
27{
28 /* start WEP IV from a random value */
29 get_random_bytes(&local->wep_iv, WEP_IV_LEN);
30
31 local->wep_tx_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0,
32 CRYPTO_ALG_ASYNC);
33 if (IS_ERR(local->wep_tx_tfm))
34 return -ENOMEM;
35
36 local->wep_rx_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0,
37 CRYPTO_ALG_ASYNC);
38 if (IS_ERR(local->wep_rx_tfm)) {
39 crypto_free_blkcipher(local->wep_tx_tfm);
40 return -ENOMEM;
41 }
42
43 return 0;
44}
45
46void ieee80211_wep_free(struct ieee80211_local *local)
47{
48 crypto_free_blkcipher(local->wep_tx_tfm);
49 crypto_free_blkcipher(local->wep_rx_tfm);
50}
51
52static inline int ieee80211_wep_weak_iv(u32 iv, int keylen)
53{
54 /* Fluhrer, Mantin, and Shamir have reported weaknesses in the
55 * key scheduling algorithm of RC4. At least IVs (KeyByte + 3,
56 * 0xff, N) can be used to speedup attacks, so avoid using them. */
57 if ((iv & 0xff00) == 0xff00) {
58 u8 B = (iv >> 16) & 0xff;
59 if (B >= 3 && B < 3 + keylen)
60 return 1;
61 }
62 return 0;
63}
64
65
Johannes Berg4f0d18e2007-09-26 15:19:40 +020066static void ieee80211_wep_get_iv(struct ieee80211_local *local,
67 struct ieee80211_key *key, u8 *iv)
Jiri Bencf0706e82007-05-05 11:45:53 -070068{
69 local->wep_iv++;
Johannes Berg8f20fc22007-08-28 17:01:54 -040070 if (ieee80211_wep_weak_iv(local->wep_iv, key->conf.keylen))
Jiri Bencf0706e82007-05-05 11:45:53 -070071 local->wep_iv += 0x0100;
72
73 if (!iv)
74 return;
75
76 *iv++ = (local->wep_iv >> 16) & 0xff;
77 *iv++ = (local->wep_iv >> 8) & 0xff;
78 *iv++ = local->wep_iv & 0xff;
Johannes Berg8f20fc22007-08-28 17:01:54 -040079 *iv++ = key->conf.keyidx << 6;
Jiri Bencf0706e82007-05-05 11:45:53 -070080}
81
82
Johannes Berg6a22a592007-09-26 15:19:41 +020083static u8 *ieee80211_wep_add_iv(struct ieee80211_local *local,
84 struct sk_buff *skb,
85 struct ieee80211_key *key)
Jiri Bencf0706e82007-05-05 11:45:53 -070086{
87 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
88 u16 fc;
89 int hdrlen;
90 u8 *newhdr;
91
92 fc = le16_to_cpu(hdr->frame_control);
93 fc |= IEEE80211_FCTL_PROTECTED;
94 hdr->frame_control = cpu_to_le16(fc);
95
96 if ((skb_headroom(skb) < WEP_IV_LEN ||
97 skb_tailroom(skb) < WEP_ICV_LEN)) {
98 I802_DEBUG_INC(local->tx_expand_skb_head);
99 if (unlikely(pskb_expand_head(skb, WEP_IV_LEN, WEP_ICV_LEN,
100 GFP_ATOMIC)))
101 return NULL;
102 }
103
104 hdrlen = ieee80211_get_hdrlen(fc);
105 newhdr = skb_push(skb, WEP_IV_LEN);
106 memmove(newhdr, newhdr + WEP_IV_LEN, hdrlen);
107 ieee80211_wep_get_iv(local, key, newhdr + hdrlen);
108 return newhdr + hdrlen;
109}
110
111
Johannes Berg4f0d18e2007-09-26 15:19:40 +0200112static void ieee80211_wep_remove_iv(struct ieee80211_local *local,
113 struct sk_buff *skb,
114 struct ieee80211_key *key)
Jiri Bencf0706e82007-05-05 11:45:53 -0700115{
116 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
117 u16 fc;
118 int hdrlen;
119
120 fc = le16_to_cpu(hdr->frame_control);
121 hdrlen = ieee80211_get_hdrlen(fc);
122 memmove(skb->data + WEP_IV_LEN, skb->data, hdrlen);
123 skb_pull(skb, WEP_IV_LEN);
124}
125
126
127/* Perform WEP encryption using given key. data buffer must have tailroom
128 * for 4-byte ICV. data_len must not include this ICV. Note: this function
129 * does _not_ add IV. data = RC4(data | CRC32(data)) */
130void ieee80211_wep_encrypt_data(struct crypto_blkcipher *tfm, u8 *rc4key,
131 size_t klen, u8 *data, size_t data_len)
132{
133 struct blkcipher_desc desc = { .tfm = tfm };
134 struct scatterlist sg;
135 __le32 *icv;
136
137 icv = (__le32 *)(data + data_len);
138 *icv = cpu_to_le32(~crc32_le(~0, data, data_len));
139
140 crypto_blkcipher_setkey(tfm, rc4key, klen);
Jens Axboefa05f122007-10-22 19:44:26 +0200141 sg_init_one(&sg, data, data_len + WEP_ICV_LEN);
Jiri Bencf0706e82007-05-05 11:45:53 -0700142 crypto_blkcipher_encrypt(&desc, &sg, &sg, sg.length);
143}
144
145
146/* Perform WEP encryption on given skb. 4 bytes of extra space (IV) in the
147 * beginning of the buffer 4 bytes of extra space (ICV) in the end of the
148 * buffer will be added. Both IV and ICV will be transmitted, so the
149 * payload length increases with 8 bytes.
150 *
151 * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data))
152 */
153int ieee80211_wep_encrypt(struct ieee80211_local *local, struct sk_buff *skb,
154 struct ieee80211_key *key)
155{
156 u32 klen;
157 u8 *rc4key, *iv;
158 size_t len;
159
Johannes Berg8f20fc22007-08-28 17:01:54 -0400160 if (!key || key->conf.alg != ALG_WEP)
Jiri Bencf0706e82007-05-05 11:45:53 -0700161 return -1;
162
Johannes Berg8f20fc22007-08-28 17:01:54 -0400163 klen = 3 + key->conf.keylen;
Jiri Bencf0706e82007-05-05 11:45:53 -0700164 rc4key = kmalloc(klen, GFP_ATOMIC);
165 if (!rc4key)
166 return -1;
167
168 iv = ieee80211_wep_add_iv(local, skb, key);
169 if (!iv) {
170 kfree(rc4key);
171 return -1;
172 }
173
174 len = skb->len - (iv + WEP_IV_LEN - skb->data);
175
176 /* Prepend 24-bit IV to RC4 key */
177 memcpy(rc4key, iv, 3);
178
179 /* Copy rest of the WEP key (the secret part) */
Johannes Berg8f20fc22007-08-28 17:01:54 -0400180 memcpy(rc4key + 3, key->conf.key, key->conf.keylen);
Jiri Bencf0706e82007-05-05 11:45:53 -0700181
182 /* Add room for ICV */
183 skb_put(skb, WEP_ICV_LEN);
184
185 ieee80211_wep_encrypt_data(local->wep_tx_tfm, rc4key, klen,
186 iv + WEP_IV_LEN, len);
187
188 kfree(rc4key);
189
190 return 0;
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. */
197int ieee80211_wep_decrypt_data(struct crypto_blkcipher *tfm, u8 *rc4key,
198 size_t klen, u8 *data, size_t data_len)
199{
200 struct blkcipher_desc desc = { .tfm = tfm };
201 struct scatterlist sg;
202 __le32 crc;
203
204 crypto_blkcipher_setkey(tfm, rc4key, klen);
Jens Axboefa05f122007-10-22 19:44:26 +0200205 sg_init_one(&sg, data, data_len + WEP_ICV_LEN);
Jiri Bencf0706e82007-05-05 11:45:53 -0700206 crypto_blkcipher_decrypt(&desc, &sg, &sg, sg.length);
207
208 crc = cpu_to_le32(~crc32_le(~0, data, data_len));
209 if (memcmp(&crc, data + data_len, 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 */
225int ieee80211_wep_decrypt(struct ieee80211_local *local, struct sk_buff *skb,
226 struct ieee80211_key *key)
227{
228 u32 klen;
229 u8 *rc4key;
230 u8 keyidx;
231 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
232 u16 fc;
233 int hdrlen;
234 size_t len;
235 int ret = 0;
236
237 fc = le16_to_cpu(hdr->frame_control);
238 if (!(fc & IEEE80211_FCTL_PROTECTED))
239 return -1;
240
241 hdrlen = ieee80211_get_hdrlen(fc);
242
243 if (skb->len < 8 + hdrlen)
244 return -1;
245
246 len = skb->len - hdrlen - 8;
247
248 keyidx = skb->data[hdrlen + 3] >> 6;
249
Johannes Berg8f20fc22007-08-28 17:01:54 -0400250 if (!key || keyidx != key->conf.keyidx || key->conf.alg != ALG_WEP)
Jiri Bencf0706e82007-05-05 11:45:53 -0700251 return -1;
252
Johannes Berg8f20fc22007-08-28 17:01:54 -0400253 klen = 3 + key->conf.keylen;
Jiri Bencf0706e82007-05-05 11:45:53 -0700254
255 rc4key = kmalloc(klen, GFP_ATOMIC);
256 if (!rc4key)
257 return -1;
258
259 /* Prepend 24-bit IV to RC4 key */
260 memcpy(rc4key, skb->data + hdrlen, 3);
261
262 /* Copy rest of the WEP key (the secret part) */
Johannes Berg8f20fc22007-08-28 17:01:54 -0400263 memcpy(rc4key + 3, key->conf.key, key->conf.keylen);
Jiri Bencf0706e82007-05-05 11:45:53 -0700264
265 if (ieee80211_wep_decrypt_data(local->wep_rx_tfm, rc4key, klen,
266 skb->data + hdrlen + WEP_IV_LEN,
267 len)) {
Adel Gadllah53cb4792007-11-29 17:09:41 +0100268 if (net_ratelimit())
269 printk(KERN_DEBUG "WEP decrypt failed (ICV)\n");
Jiri Bencf0706e82007-05-05 11:45:53 -0700270 ret = -1;
271 }
272
273 kfree(rc4key);
274
275 /* Trim ICV */
276 skb_trim(skb, skb->len - WEP_ICV_LEN);
277
278 /* Remove IV */
279 memmove(skb->data + WEP_IV_LEN, skb->data, hdrlen);
280 skb_pull(skb, WEP_IV_LEN);
281
282 return ret;
283}
284
285
Jiri Bencf0706e82007-05-05 11:45:53 -0700286u8 * ieee80211_wep_is_weak_iv(struct sk_buff *skb, struct ieee80211_key *key)
287{
288 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
289 u16 fc;
290 int hdrlen;
291 u8 *ivpos;
292 u32 iv;
293
294 fc = le16_to_cpu(hdr->frame_control);
295 if (!(fc & IEEE80211_FCTL_PROTECTED))
296 return NULL;
297
298 hdrlen = ieee80211_get_hdrlen(fc);
299 ivpos = skb->data + hdrlen;
300 iv = (ivpos[0] << 16) | (ivpos[1] << 8) | ivpos[2];
301
Johannes Berg8f20fc22007-08-28 17:01:54 -0400302 if (ieee80211_wep_weak_iv(iv, key->conf.keylen))
Jiri Bencf0706e82007-05-05 11:45:53 -0700303 return ivpos;
304
305 return NULL;
306}
Johannes Berg4f0d18e2007-09-26 15:19:40 +0200307
Johannes Berg9ae54c82008-01-31 19:48:20 +0100308ieee80211_rx_result
Johannes Berg5cf121c2008-02-25 16:27:43 +0100309ieee80211_crypto_wep_decrypt(struct ieee80211_rx_data *rx)
Johannes Berg4f0d18e2007-09-26 15:19:40 +0200310{
311 if ((rx->fc & IEEE80211_FCTL_FTYPE) != IEEE80211_FTYPE_DATA &&
312 ((rx->fc & IEEE80211_FCTL_FTYPE) != IEEE80211_FTYPE_MGMT ||
313 (rx->fc & IEEE80211_FCTL_STYPE) != IEEE80211_STYPE_AUTH))
Johannes Berg9ae54c82008-01-31 19:48:20 +0100314 return RX_CONTINUE;
Johannes Berg4f0d18e2007-09-26 15:19:40 +0200315
Johannes Berg5cf121c2008-02-25 16:27:43 +0100316 if (!(rx->status->flag & RX_FLAG_DECRYPTED)) {
Johannes Berg4f0d18e2007-09-26 15:19:40 +0200317 if (ieee80211_wep_decrypt(rx->local, rx->skb, rx->key)) {
John W. Linville7f3ad892007-11-06 17:12:31 -0500318#ifdef CONFIG_MAC80211_DEBUG
Johannes Berg4f0d18e2007-09-26 15:19:40 +0200319 if (net_ratelimit())
320 printk(KERN_DEBUG "%s: RX WEP frame, decrypt "
321 "failed\n", rx->dev->name);
John W. Linville7f3ad892007-11-06 17:12:31 -0500322#endif /* CONFIG_MAC80211_DEBUG */
Johannes Berge4c26ad2008-01-31 19:48:21 +0100323 return RX_DROP_UNUSABLE;
Johannes Berg4f0d18e2007-09-26 15:19:40 +0200324 }
Johannes Berg5cf121c2008-02-25 16:27:43 +0100325 } else if (!(rx->status->flag & RX_FLAG_IV_STRIPPED)) {
Johannes Berg4f0d18e2007-09-26 15:19:40 +0200326 ieee80211_wep_remove_iv(rx->local, rx->skb, rx->key);
327 /* remove ICV */
328 skb_trim(rx->skb, rx->skb->len - 4);
329 }
330
Johannes Berg9ae54c82008-01-31 19:48:20 +0100331 return RX_CONTINUE;
Johannes Berg4f0d18e2007-09-26 15:19:40 +0200332}
Johannes Berg6a22a592007-09-26 15:19:41 +0200333
Johannes Berg5cf121c2008-02-25 16:27:43 +0100334static int wep_encrypt_skb(struct ieee80211_tx_data *tx, struct sk_buff *skb)
Johannes Berg6a22a592007-09-26 15:19:41 +0200335{
336 if (!(tx->key->flags & KEY_FLAG_UPLOADED_TO_HARDWARE)) {
337 if (ieee80211_wep_encrypt(tx->local, skb, tx->key))
338 return -1;
339 } else {
Ivo van Doorn1c014422008-04-17 19:41:02 +0200340 tx->control->hw_key = &tx->key->conf;
Johannes Berg6a22a592007-09-26 15:19:41 +0200341 if (tx->key->conf.flags & IEEE80211_KEY_FLAG_GENERATE_IV) {
342 if (!ieee80211_wep_add_iv(tx->local, skb, tx->key))
343 return -1;
344 }
345 }
346 return 0;
347}
348
Johannes Berg9ae54c82008-01-31 19:48:20 +0100349ieee80211_tx_result
Johannes Berg5cf121c2008-02-25 16:27:43 +0100350ieee80211_crypto_wep_encrypt(struct ieee80211_tx_data *tx)
Johannes Berg6a22a592007-09-26 15:19:41 +0200351{
Johannes Berg5cf121c2008-02-25 16:27:43 +0100352 tx->control->iv_len = WEP_IV_LEN;
353 tx->control->icv_len = WEP_ICV_LEN;
354 ieee80211_tx_set_protected(tx);
Johannes Berg6a22a592007-09-26 15:19:41 +0200355
356 if (wep_encrypt_skb(tx, tx->skb) < 0) {
357 I802_DEBUG_INC(tx->local->tx_handlers_drop_wep);
Johannes Berg9ae54c82008-01-31 19:48:20 +0100358 return TX_DROP;
Johannes Berg6a22a592007-09-26 15:19:41 +0200359 }
360
Johannes Berg5cf121c2008-02-25 16:27:43 +0100361 if (tx->extra_frag) {
Johannes Berg6a22a592007-09-26 15:19:41 +0200362 int i;
Johannes Berg5cf121c2008-02-25 16:27:43 +0100363 for (i = 0; i < tx->num_extra_frag; i++) {
364 if (wep_encrypt_skb(tx, tx->extra_frag[i]) < 0) {
Johannes Berg6a22a592007-09-26 15:19:41 +0200365 I802_DEBUG_INC(tx->local->
366 tx_handlers_drop_wep);
Johannes Berg9ae54c82008-01-31 19:48:20 +0100367 return TX_DROP;
Johannes Berg6a22a592007-09-26 15:19:41 +0200368 }
369 }
370 }
371
Johannes Berg9ae54c82008-01-31 19:48:20 +0100372 return TX_CONTINUE;
Johannes Berg6a22a592007-09-26 15:19:41 +0200373}