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f0706e82 JB |
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 <asm/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 | 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->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->keyidx << 6; | |
80 | } | |
81 | ||
82 | ||
83 | 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 | 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.page = virt_to_page(data); | |
142 | sg.offset = offset_in_page(data); | |
143 | sg.length = data_len + WEP_ICV_LEN; | |
144 | crypto_blkcipher_encrypt(&desc, &sg, &sg, sg.length); | |
145 | } | |
146 | ||
147 | ||
148 | /* Perform WEP encryption on given skb. 4 bytes of extra space (IV) in the | |
149 | * beginning of the buffer 4 bytes of extra space (ICV) in the end of the | |
150 | * buffer will be added. Both IV and ICV will be transmitted, so the | |
151 | * payload length increases with 8 bytes. | |
152 | * | |
153 | * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data)) | |
154 | */ | |
155 | int ieee80211_wep_encrypt(struct ieee80211_local *local, struct sk_buff *skb, | |
156 | struct ieee80211_key *key) | |
157 | { | |
158 | u32 klen; | |
159 | u8 *rc4key, *iv; | |
160 | size_t len; | |
161 | ||
162 | if (!key || key->alg != ALG_WEP) | |
163 | return -1; | |
164 | ||
165 | klen = 3 + key->keylen; | |
166 | rc4key = kmalloc(klen, GFP_ATOMIC); | |
167 | if (!rc4key) | |
168 | return -1; | |
169 | ||
170 | iv = ieee80211_wep_add_iv(local, skb, key); | |
171 | if (!iv) { | |
172 | kfree(rc4key); | |
173 | return -1; | |
174 | } | |
175 | ||
176 | len = skb->len - (iv + 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->key, key->keylen); | |
183 | ||
184 | /* Add room for ICV */ | |
185 | skb_put(skb, WEP_ICV_LEN); | |
186 | ||
187 | ieee80211_wep_encrypt_data(local->wep_tx_tfm, rc4key, klen, | |
188 | iv + WEP_IV_LEN, len); | |
189 | ||
190 | kfree(rc4key); | |
191 | ||
192 | return 0; | |
193 | } | |
194 | ||
195 | ||
196 | /* Perform WEP decryption using given key. data buffer includes encrypted | |
197 | * payload, including 4-byte ICV, but _not_ IV. data_len must not include ICV. | |
198 | * Return 0 on success and -1 on ICV mismatch. */ | |
199 | int ieee80211_wep_decrypt_data(struct crypto_blkcipher *tfm, u8 *rc4key, | |
200 | size_t klen, u8 *data, size_t data_len) | |
201 | { | |
202 | struct blkcipher_desc desc = { .tfm = tfm }; | |
203 | struct scatterlist sg; | |
204 | __le32 crc; | |
205 | ||
206 | crypto_blkcipher_setkey(tfm, rc4key, klen); | |
207 | sg.page = virt_to_page(data); | |
208 | sg.offset = offset_in_page(data); | |
209 | sg.length = data_len + WEP_ICV_LEN; | |
210 | crypto_blkcipher_decrypt(&desc, &sg, &sg, sg.length); | |
211 | ||
212 | crc = cpu_to_le32(~crc32_le(~0, data, data_len)); | |
213 | if (memcmp(&crc, data + data_len, WEP_ICV_LEN) != 0) | |
214 | /* ICV mismatch */ | |
215 | return -1; | |
216 | ||
217 | return 0; | |
218 | } | |
219 | ||
220 | ||
221 | /* Perform WEP decryption on given skb. Buffer includes whole WEP part of | |
222 | * the frame: IV (4 bytes), encrypted payload (including SNAP header), | |
223 | * ICV (4 bytes). skb->len includes both IV and ICV. | |
224 | * | |
225 | * Returns 0 if frame was decrypted successfully and ICV was correct and -1 on | |
226 | * failure. If frame is OK, IV and ICV will be removed, i.e., decrypted payload | |
227 | * is moved to the beginning of the skb and skb length will be reduced. | |
228 | */ | |
229 | int ieee80211_wep_decrypt(struct ieee80211_local *local, struct sk_buff *skb, | |
230 | struct ieee80211_key *key) | |
231 | { | |
232 | u32 klen; | |
233 | u8 *rc4key; | |
234 | u8 keyidx; | |
235 | struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data; | |
236 | u16 fc; | |
237 | int hdrlen; | |
238 | size_t len; | |
239 | int ret = 0; | |
240 | ||
241 | fc = le16_to_cpu(hdr->frame_control); | |
242 | if (!(fc & IEEE80211_FCTL_PROTECTED)) | |
243 | return -1; | |
244 | ||
245 | hdrlen = ieee80211_get_hdrlen(fc); | |
246 | ||
247 | if (skb->len < 8 + hdrlen) | |
248 | return -1; | |
249 | ||
250 | len = skb->len - hdrlen - 8; | |
251 | ||
252 | keyidx = skb->data[hdrlen + 3] >> 6; | |
253 | ||
254 | if (!key || keyidx != key->keyidx || key->alg != ALG_WEP) | |
255 | return -1; | |
256 | ||
257 | klen = 3 + key->keylen; | |
258 | ||
259 | rc4key = kmalloc(klen, GFP_ATOMIC); | |
260 | if (!rc4key) | |
261 | return -1; | |
262 | ||
263 | /* Prepend 24-bit IV to RC4 key */ | |
264 | memcpy(rc4key, skb->data + hdrlen, 3); | |
265 | ||
266 | /* Copy rest of the WEP key (the secret part) */ | |
267 | memcpy(rc4key + 3, key->key, key->keylen); | |
268 | ||
269 | if (ieee80211_wep_decrypt_data(local->wep_rx_tfm, rc4key, klen, | |
270 | skb->data + hdrlen + WEP_IV_LEN, | |
271 | len)) { | |
272 | printk(KERN_DEBUG "WEP decrypt failed (ICV)\n"); | |
273 | ret = -1; | |
274 | } | |
275 | ||
276 | kfree(rc4key); | |
277 | ||
278 | /* Trim ICV */ | |
279 | skb_trim(skb, skb->len - WEP_ICV_LEN); | |
280 | ||
281 | /* Remove IV */ | |
282 | memmove(skb->data + WEP_IV_LEN, skb->data, hdrlen); | |
283 | skb_pull(skb, WEP_IV_LEN); | |
284 | ||
285 | return ret; | |
286 | } | |
287 | ||
288 | ||
289 | int ieee80211_wep_get_keyidx(struct sk_buff *skb) | |
290 | { | |
291 | struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data; | |
292 | u16 fc; | |
293 | int hdrlen; | |
294 | ||
295 | fc = le16_to_cpu(hdr->frame_control); | |
296 | if (!(fc & IEEE80211_FCTL_PROTECTED)) | |
297 | return -1; | |
298 | ||
299 | hdrlen = ieee80211_get_hdrlen(fc); | |
300 | ||
301 | if (skb->len < 8 + hdrlen) | |
302 | return -1; | |
303 | ||
304 | return skb->data[hdrlen + 3] >> 6; | |
305 | } | |
306 | ||
307 | ||
308 | u8 * ieee80211_wep_is_weak_iv(struct sk_buff *skb, struct ieee80211_key *key) | |
309 | { | |
310 | struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data; | |
311 | u16 fc; | |
312 | int hdrlen; | |
313 | u8 *ivpos; | |
314 | u32 iv; | |
315 | ||
316 | fc = le16_to_cpu(hdr->frame_control); | |
317 | if (!(fc & IEEE80211_FCTL_PROTECTED)) | |
318 | return NULL; | |
319 | ||
320 | hdrlen = ieee80211_get_hdrlen(fc); | |
321 | ivpos = skb->data + hdrlen; | |
322 | iv = (ivpos[0] << 16) | (ivpos[1] << 8) | ivpos[2]; | |
323 | ||
324 | if (ieee80211_wep_weak_iv(iv, key->keylen)) | |
325 | return ivpos; | |
326 | ||
327 | return NULL; | |
328 | } |