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 <asm/unaligned.h>
21
22 #include <net/mac80211.h>
23 #include "ieee80211_i.h"
24 #include "wep.h"
25
26
27 int ieee80211_wep_init(struct ieee80211_local *local)
28 {
29 /* start WEP IV from a random value */
30 get_random_bytes(&local->wep_iv, WEP_IV_LEN);
31
32 local->wep_tx_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0,
33 CRYPTO_ALG_ASYNC);
34 if (IS_ERR(local->wep_tx_tfm))
35 return PTR_ERR(local->wep_tx_tfm);
36
37 local->wep_rx_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0,
38 CRYPTO_ALG_ASYNC);
39 if (IS_ERR(local->wep_rx_tfm)) {
40 crypto_free_blkcipher(local->wep_tx_tfm);
41 return PTR_ERR(local->wep_rx_tfm);
42 }
43
44 return 0;
45 }
46
47 void ieee80211_wep_free(struct ieee80211_local *local)
48 {
49 crypto_free_blkcipher(local->wep_tx_tfm);
50 crypto_free_blkcipher(local->wep_rx_tfm);
51 }
52
53 static inline bool ieee80211_wep_weak_iv(u32 iv, int keylen)
54 {
55 /*
56 * Fluhrer, Mantin, and Shamir have reported weaknesses in the
57 * key scheduling algorithm of RC4. At least IVs (KeyByte + 3,
58 * 0xff, N) can be used to speedup attacks, so avoid using them.
59 */
60 if ((iv & 0xff00) == 0xff00) {
61 u8 B = (iv >> 16) & 0xff;
62 if (B >= 3 && B < 3 + keylen)
63 return true;
64 }
65 return false;
66 }
67
68
69 static void ieee80211_wep_get_iv(struct ieee80211_local *local,
70 struct ieee80211_key *key, u8 *iv)
71 {
72 local->wep_iv++;
73 if (ieee80211_wep_weak_iv(local->wep_iv, key->conf.keylen))
74 local->wep_iv += 0x0100;
75
76 if (!iv)
77 return;
78
79 *iv++ = (local->wep_iv >> 16) & 0xff;
80 *iv++ = (local->wep_iv >> 8) & 0xff;
81 *iv++ = local->wep_iv & 0xff;
82 *iv++ = key->conf.keyidx << 6;
83 }
84
85
86 static u8 *ieee80211_wep_add_iv(struct ieee80211_local *local,
87 struct sk_buff *skb,
88 struct ieee80211_key *key)
89 {
90 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
91 unsigned int hdrlen;
92 u8 *newhdr;
93
94 hdr->frame_control |= cpu_to_le16(IEEE80211_FCTL_PROTECTED);
95
96 if (WARN_ON(skb_tailroom(skb) < WEP_ICV_LEN ||
97 skb_headroom(skb) < WEP_IV_LEN))
98 return NULL;
99
100 hdrlen = ieee80211_hdrlen(hdr->frame_control);
101 newhdr = skb_push(skb, WEP_IV_LEN);
102 memmove(newhdr, newhdr + WEP_IV_LEN, hdrlen);
103 ieee80211_wep_get_iv(local, key, newhdr + hdrlen);
104 return newhdr + hdrlen;
105 }
106
107
108 static void ieee80211_wep_remove_iv(struct ieee80211_local *local,
109 struct sk_buff *skb,
110 struct ieee80211_key *key)
111 {
112 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
113 unsigned int hdrlen;
114
115 hdrlen = ieee80211_hdrlen(hdr->frame_control);
116 memmove(skb->data + WEP_IV_LEN, skb->data, hdrlen);
117 skb_pull(skb, WEP_IV_LEN);
118 }
119
120
121 /* Perform WEP encryption using given key. data buffer must have tailroom
122 * for 4-byte ICV. data_len must not include this ICV. Note: this function
123 * does _not_ add IV. data = RC4(data | CRC32(data)) */
124 void ieee80211_wep_encrypt_data(struct crypto_blkcipher *tfm, u8 *rc4key,
125 size_t klen, u8 *data, size_t data_len)
126 {
127 struct blkcipher_desc desc = { .tfm = tfm };
128 struct scatterlist sg;
129 __le32 icv;
130
131 icv = cpu_to_le32(~crc32_le(~0, data, data_len));
132 put_unaligned(icv, (__le32 *)(data + data_len));
133
134 crypto_blkcipher_setkey(tfm, rc4key, klen);
135 sg_init_one(&sg, data, data_len + WEP_ICV_LEN);
136 crypto_blkcipher_encrypt(&desc, &sg, &sg, sg.length);
137 }
138
139
140 /* Perform WEP encryption on given skb. 4 bytes of extra space (IV) in the
141 * beginning of the buffer 4 bytes of extra space (ICV) in the end of the
142 * buffer will be added. Both IV and ICV will be transmitted, so the
143 * payload length increases with 8 bytes.
144 *
145 * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data))
146 */
147 int ieee80211_wep_encrypt(struct ieee80211_local *local, struct sk_buff *skb,
148 struct ieee80211_key *key)
149 {
150 u32 klen;
151 u8 *rc4key, *iv;
152 size_t len;
153
154 if (!key || key->conf.alg != ALG_WEP)
155 return -1;
156
157 klen = 3 + key->conf.keylen;
158 rc4key = kmalloc(klen, GFP_ATOMIC);
159 if (!rc4key)
160 return -1;
161
162 iv = ieee80211_wep_add_iv(local, skb, key);
163 if (!iv) {
164 kfree(rc4key);
165 return -1;
166 }
167
168 len = skb->len - (iv + WEP_IV_LEN - skb->data);
169
170 /* Prepend 24-bit IV to RC4 key */
171 memcpy(rc4key, iv, 3);
172
173 /* Copy rest of the WEP key (the secret part) */
174 memcpy(rc4key + 3, key->conf.key, key->conf.keylen);
175
176 /* Add room for ICV */
177 skb_put(skb, WEP_ICV_LEN);
178
179 ieee80211_wep_encrypt_data(local->wep_tx_tfm, rc4key, klen,
180 iv + WEP_IV_LEN, len);
181
182 kfree(rc4key);
183
184 return 0;
185 }
186
187
188 /* Perform WEP decryption using given key. data buffer includes encrypted
189 * payload, including 4-byte ICV, but _not_ IV. data_len must not include ICV.
190 * Return 0 on success and -1 on ICV mismatch. */
191 int ieee80211_wep_decrypt_data(struct crypto_blkcipher *tfm, u8 *rc4key,
192 size_t klen, u8 *data, size_t data_len)
193 {
194 struct blkcipher_desc desc = { .tfm = tfm };
195 struct scatterlist sg;
196 __le32 crc;
197
198 crypto_blkcipher_setkey(tfm, rc4key, klen);
199 sg_init_one(&sg, data, data_len + WEP_ICV_LEN);
200 crypto_blkcipher_decrypt(&desc, &sg, &sg, sg.length);
201
202 crc = cpu_to_le32(~crc32_le(~0, data, data_len));
203 if (memcmp(&crc, data + data_len, WEP_ICV_LEN) != 0)
204 /* ICV mismatch */
205 return -1;
206
207 return 0;
208 }
209
210
211 /* Perform WEP decryption on given skb. Buffer includes whole WEP part of
212 * the frame: IV (4 bytes), encrypted payload (including SNAP header),
213 * ICV (4 bytes). skb->len includes both IV and ICV.
214 *
215 * Returns 0 if frame was decrypted successfully and ICV was correct and -1 on
216 * failure. If frame is OK, IV and ICV will be removed, i.e., decrypted payload
217 * is moved to the beginning of the skb and skb length will be reduced.
218 */
219 int ieee80211_wep_decrypt(struct ieee80211_local *local, struct sk_buff *skb,
220 struct ieee80211_key *key)
221 {
222 u32 klen;
223 u8 *rc4key;
224 u8 keyidx;
225 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
226 unsigned int hdrlen;
227 size_t len;
228 int ret = 0;
229
230 if (!ieee80211_has_protected(hdr->frame_control))
231 return -1;
232
233 hdrlen = ieee80211_hdrlen(hdr->frame_control);
234 if (skb->len < hdrlen + WEP_IV_LEN + WEP_ICV_LEN)
235 return -1;
236
237 len = skb->len - hdrlen - WEP_IV_LEN - WEP_ICV_LEN;
238
239 keyidx = skb->data[hdrlen + 3] >> 6;
240
241 if (!key || keyidx != key->conf.keyidx || key->conf.alg != ALG_WEP)
242 return -1;
243
244 klen = 3 + key->conf.keylen;
245
246 rc4key = kmalloc(klen, GFP_ATOMIC);
247 if (!rc4key)
248 return -1;
249
250 /* Prepend 24-bit IV to RC4 key */
251 memcpy(rc4key, skb->data + hdrlen, 3);
252
253 /* Copy rest of the WEP key (the secret part) */
254 memcpy(rc4key + 3, key->conf.key, key->conf.keylen);
255
256 if (ieee80211_wep_decrypt_data(local->wep_rx_tfm, rc4key, klen,
257 skb->data + hdrlen + WEP_IV_LEN,
258 len))
259 ret = -1;
260
261 kfree(rc4key);
262
263 /* Trim ICV */
264 skb_trim(skb, skb->len - WEP_ICV_LEN);
265
266 /* Remove IV */
267 memmove(skb->data + WEP_IV_LEN, skb->data, hdrlen);
268 skb_pull(skb, WEP_IV_LEN);
269
270 return ret;
271 }
272
273
274 bool ieee80211_wep_is_weak_iv(struct sk_buff *skb, struct ieee80211_key *key)
275 {
276 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
277 unsigned int hdrlen;
278 u8 *ivpos;
279 u32 iv;
280
281 if (!ieee80211_has_protected(hdr->frame_control))
282 return false;
283
284 hdrlen = ieee80211_hdrlen(hdr->frame_control);
285 ivpos = skb->data + hdrlen;
286 iv = (ivpos[0] << 16) | (ivpos[1] << 8) | ivpos[2];
287
288 return ieee80211_wep_weak_iv(iv, key->conf.keylen);
289 }
290
291 ieee80211_rx_result
292 ieee80211_crypto_wep_decrypt(struct ieee80211_rx_data *rx)
293 {
294 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)rx->skb->data;
295
296 if (!ieee80211_is_data(hdr->frame_control) &&
297 !ieee80211_is_auth(hdr->frame_control))
298 return RX_CONTINUE;
299
300 if (!(rx->status->flag & RX_FLAG_DECRYPTED)) {
301 if (ieee80211_wep_decrypt(rx->local, rx->skb, rx->key))
302 return RX_DROP_UNUSABLE;
303 } else if (!(rx->status->flag & RX_FLAG_IV_STRIPPED)) {
304 ieee80211_wep_remove_iv(rx->local, rx->skb, rx->key);
305 /* remove ICV */
306 skb_trim(rx->skb, rx->skb->len - WEP_ICV_LEN);
307 }
308
309 return RX_CONTINUE;
310 }
311
312 static int wep_encrypt_skb(struct ieee80211_tx_data *tx, struct sk_buff *skb)
313 {
314 struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
315
316 if (!(tx->key->flags & KEY_FLAG_UPLOADED_TO_HARDWARE)) {
317 if (ieee80211_wep_encrypt(tx->local, skb, tx->key))
318 return -1;
319 } else {
320 info->control.hw_key = &tx->key->conf;
321 if (tx->key->conf.flags & IEEE80211_KEY_FLAG_GENERATE_IV) {
322 if (!ieee80211_wep_add_iv(tx->local, skb, tx->key))
323 return -1;
324 }
325 }
326 return 0;
327 }
328
329 ieee80211_tx_result
330 ieee80211_crypto_wep_encrypt(struct ieee80211_tx_data *tx)
331 {
332 struct sk_buff *skb;
333
334 ieee80211_tx_set_protected(tx);
335
336 skb = tx->skb;
337 do {
338 if (wep_encrypt_skb(tx, skb) < 0) {
339 I802_DEBUG_INC(tx->local->tx_handlers_drop_wep);
340 return TX_DROP;
341 }
342 } while ((skb = skb->next));
343
344 return TX_CONTINUE;
345 }
346
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