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
21 #include <net/mac80211.h>
22 #include "ieee80211_i.h"
23 #include "wep.h"
24
25
26 int 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
46 void 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
52 static 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
66 static void ieee80211_wep_get_iv(struct ieee80211_local *local,
67 struct ieee80211_key *key, u8 *iv)
68 {
69 local->wep_iv++;
70 if (ieee80211_wep_weak_iv(local->wep_iv, key->conf.keylen))
71 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;
79 *iv++ = key->conf.keyidx << 6;
80 }
81
82
83 static u8 *ieee80211_wep_add_iv(struct ieee80211_local *local,
84 struct sk_buff *skb,
85 struct ieee80211_key *key)
86 {
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
112 static void ieee80211_wep_remove_iv(struct ieee80211_local *local,
113 struct sk_buff *skb,
114 struct ieee80211_key *key)
115 {
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)) */
130 void 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);
141 sg_init_one(&sg, data, data_len + WEP_ICV_LEN);
142 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 */
153 int 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
160 if (!key || key->conf.alg != ALG_WEP)
161 return -1;
162
163 klen = 3 + key->conf.keylen;
164 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) */
180 memcpy(rc4key + 3, key->conf.key, key->conf.keylen);
181
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. */
197 int 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);
205 sg_init_one(&sg, data, data_len + WEP_ICV_LEN);
206 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 */
225 int 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
250 if (!key || keyidx != key->conf.keyidx || key->conf.alg != ALG_WEP)
251 return -1;
252
253 klen = 3 + key->conf.keylen;
254
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) */
263 memcpy(rc4key + 3, key->conf.key, key->conf.keylen);
264
265 if (ieee80211_wep_decrypt_data(local->wep_rx_tfm, rc4key, klen,
266 skb->data + hdrlen + WEP_IV_LEN,
267 len)) {
268 if (net_ratelimit())
269 printk(KERN_DEBUG "WEP decrypt failed (ICV)\n");
270 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
286 u8 * 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
302 if (ieee80211_wep_weak_iv(iv, key->conf.keylen))
303 return ivpos;
304
305 return NULL;
306 }
307
308 ieee80211_txrx_result
309 ieee80211_crypto_wep_decrypt(struct ieee80211_txrx_data *rx)
310 {
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))
314 return TXRX_CONTINUE;
315
316 if (!(rx->u.rx.status->flag & RX_FLAG_DECRYPTED)) {
317 if (ieee80211_wep_decrypt(rx->local, rx->skb, rx->key)) {
318 #ifdef CONFIG_MAC80211_DEBUG
319 if (net_ratelimit())
320 printk(KERN_DEBUG "%s: RX WEP frame, decrypt "
321 "failed\n", rx->dev->name);
322 #endif /* CONFIG_MAC80211_DEBUG */
323 return TXRX_DROP;
324 }
325 } else if (!(rx->u.rx.status->flag & RX_FLAG_IV_STRIPPED)) {
326 ieee80211_wep_remove_iv(rx->local, rx->skb, rx->key);
327 /* remove ICV */
328 skb_trim(rx->skb, rx->skb->len - 4);
329 }
330
331 return TXRX_CONTINUE;
332 }
333
334 static int wep_encrypt_skb(struct ieee80211_txrx_data *tx, struct sk_buff *skb)
335 {
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 {
340 tx->u.tx.control->key_idx = tx->key->conf.hw_key_idx;
341 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
349 ieee80211_txrx_result
350 ieee80211_crypto_wep_encrypt(struct ieee80211_txrx_data *tx)
351 {
352 tx->u.tx.control->iv_len = WEP_IV_LEN;
353 tx->u.tx.control->icv_len = WEP_ICV_LEN;
354 ieee80211_tx_set_iswep(tx);
355
356 if (wep_encrypt_skb(tx, tx->skb) < 0) {
357 I802_DEBUG_INC(tx->local->tx_handlers_drop_wep);
358 return TXRX_DROP;
359 }
360
361 if (tx->u.tx.extra_frag) {
362 int i;
363 for (i = 0; i < tx->u.tx.num_extra_frag; i++) {
364 if (wep_encrypt_skb(tx, tx->u.tx.extra_frag[i]) < 0) {
365 I802_DEBUG_INC(tx->local->
366 tx_handlers_drop_wep);
367 return TXRX_DROP;
368 }
369 }
370 }
371
372 return TXRX_CONTINUE;
373 }
374
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