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b453872c JG |
1 | /* |
2 | * Host AP crypt: host-based WEP encryption implementation for Host AP driver | |
3 | * | |
4 | * Copyright (c) 2002-2004, Jouni Malinen <jkmaline@cc.hut.fi> | |
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. See README and COPYING for | |
9 | * more details. | |
10 | */ | |
11 | ||
b453872c JG |
12 | #include <linux/module.h> |
13 | #include <linux/init.h> | |
14 | #include <linux/slab.h> | |
15 | #include <linux/random.h> | |
16 | #include <linux/skbuff.h> | |
17 | #include <asm/string.h> | |
18 | ||
19 | #include <net/ieee80211.h> | |
20 | ||
b453872c JG |
21 | #include <linux/crypto.h> |
22 | #include <asm/scatterlist.h> | |
23 | #include <linux/crc32.h> | |
24 | ||
25 | MODULE_AUTHOR("Jouni Malinen"); | |
26 | MODULE_DESCRIPTION("Host AP crypt: WEP"); | |
27 | MODULE_LICENSE("GPL"); | |
28 | ||
b453872c JG |
29 | struct prism2_wep_data { |
30 | u32 iv; | |
31 | #define WEP_KEY_LEN 13 | |
32 | u8 key[WEP_KEY_LEN + 1]; | |
33 | u8 key_len; | |
34 | u8 key_idx; | |
5a656949 ZY |
35 | struct crypto_tfm *tx_tfm; |
36 | struct crypto_tfm *rx_tfm; | |
b453872c JG |
37 | }; |
38 | ||
6eb6edf0 | 39 | static void *prism2_wep_init(int keyidx) |
b453872c JG |
40 | { |
41 | struct prism2_wep_data *priv; | |
42 | ||
0da974f4 | 43 | priv = kzalloc(sizeof(*priv), GFP_ATOMIC); |
b453872c JG |
44 | if (priv == NULL) |
45 | goto fail; | |
b453872c JG |
46 | priv->key_idx = keyidx; |
47 | ||
5a656949 ZY |
48 | priv->tx_tfm = crypto_alloc_tfm("arc4", 0); |
49 | if (priv->tx_tfm == NULL) { | |
b453872c JG |
50 | printk(KERN_DEBUG "ieee80211_crypt_wep: could not allocate " |
51 | "crypto API arc4\n"); | |
52 | goto fail; | |
53 | } | |
54 | ||
5a656949 ZY |
55 | priv->rx_tfm = crypto_alloc_tfm("arc4", 0); |
56 | if (priv->rx_tfm == NULL) { | |
57 | printk(KERN_DEBUG "ieee80211_crypt_wep: could not allocate " | |
58 | "crypto API arc4\n"); | |
59 | goto fail; | |
60 | } | |
b453872c JG |
61 | /* start WEP IV from a random value */ |
62 | get_random_bytes(&priv->iv, 4); | |
63 | ||
64 | return priv; | |
65 | ||
0edd5b44 | 66 | fail: |
b453872c | 67 | if (priv) { |
5a656949 ZY |
68 | if (priv->tx_tfm) |
69 | crypto_free_tfm(priv->tx_tfm); | |
70 | if (priv->rx_tfm) | |
71 | crypto_free_tfm(priv->rx_tfm); | |
b453872c JG |
72 | kfree(priv); |
73 | } | |
74 | return NULL; | |
75 | } | |
76 | ||
b453872c JG |
77 | static void prism2_wep_deinit(void *priv) |
78 | { | |
79 | struct prism2_wep_data *_priv = priv; | |
5a656949 ZY |
80 | if (_priv) { |
81 | if (_priv->tx_tfm) | |
82 | crypto_free_tfm(_priv->tx_tfm); | |
83 | if (_priv->rx_tfm) | |
84 | crypto_free_tfm(_priv->rx_tfm); | |
85 | } | |
b453872c JG |
86 | kfree(priv); |
87 | } | |
88 | ||
a4bf26f3 | 89 | /* Add WEP IV/key info to a frame that has at least 4 bytes of headroom */ |
9184d934 ZY |
90 | static int prism2_wep_build_iv(struct sk_buff *skb, int hdr_len, |
91 | u8 *key, int keylen, void *priv) | |
b453872c JG |
92 | { |
93 | struct prism2_wep_data *wep = priv; | |
a4bf26f3 JB |
94 | u32 klen, len; |
95 | u8 *pos; | |
96 | ||
97 | if (skb_headroom(skb) < 4 || skb->len < hdr_len) | |
b453872c JG |
98 | return -1; |
99 | ||
100 | len = skb->len - hdr_len; | |
101 | pos = skb_push(skb, 4); | |
102 | memmove(pos, pos + 4, hdr_len); | |
103 | pos += hdr_len; | |
104 | ||
105 | klen = 3 + wep->key_len; | |
106 | ||
107 | wep->iv++; | |
108 | ||
109 | /* Fluhrer, Mantin, and Shamir have reported weaknesses in the key | |
110 | * scheduling algorithm of RC4. At least IVs (KeyByte + 3, 0xff, N) | |
111 | * can be used to speedup attacks, so avoid using them. */ | |
112 | if ((wep->iv & 0xff00) == 0xff00) { | |
113 | u8 B = (wep->iv >> 16) & 0xff; | |
114 | if (B >= 3 && B < klen) | |
115 | wep->iv += 0x0100; | |
116 | } | |
117 | ||
118 | /* Prepend 24-bit IV to RC4 key and TX frame */ | |
a4bf26f3 JB |
119 | *pos++ = (wep->iv >> 16) & 0xff; |
120 | *pos++ = (wep->iv >> 8) & 0xff; | |
121 | *pos++ = wep->iv & 0xff; | |
b453872c JG |
122 | *pos++ = wep->key_idx << 6; |
123 | ||
a4bf26f3 JB |
124 | return 0; |
125 | } | |
126 | ||
127 | /* Perform WEP encryption on given skb that has at least 4 bytes of headroom | |
128 | * for IV and 4 bytes of tailroom for ICV. Both IV and ICV will be transmitted, | |
129 | * so the payload length increases with 8 bytes. | |
130 | * | |
131 | * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data)) | |
132 | */ | |
133 | static int prism2_wep_encrypt(struct sk_buff *skb, int hdr_len, void *priv) | |
134 | { | |
135 | struct prism2_wep_data *wep = priv; | |
136 | u32 crc, klen, len; | |
137 | u8 *pos, *icv; | |
138 | struct scatterlist sg; | |
139 | u8 key[WEP_KEY_LEN + 3]; | |
140 | ||
141 | /* other checks are in prism2_wep_build_iv */ | |
142 | if (skb_tailroom(skb) < 4) | |
143 | return -1; | |
144 | ||
145 | /* add the IV to the frame */ | |
9184d934 | 146 | if (prism2_wep_build_iv(skb, hdr_len, NULL, 0, priv)) |
a4bf26f3 JB |
147 | return -1; |
148 | ||
149 | /* Copy the IV into the first 3 bytes of the key */ | |
150 | memcpy(key, skb->data + hdr_len, 3); | |
151 | ||
b453872c JG |
152 | /* Copy rest of the WEP key (the secret part) */ |
153 | memcpy(key + 3, wep->key, wep->key_len); | |
a4bf26f3 JB |
154 | |
155 | len = skb->len - hdr_len - 4; | |
156 | pos = skb->data + hdr_len + 4; | |
157 | klen = 3 + wep->key_len; | |
b453872c | 158 | |
a4bf26f3 | 159 | /* Append little-endian CRC32 over only the data and encrypt it to produce ICV */ |
b453872c JG |
160 | crc = ~crc32_le(~0, pos, len); |
161 | icv = skb_put(skb, 4); | |
162 | icv[0] = crc; | |
163 | icv[1] = crc >> 8; | |
164 | icv[2] = crc >> 16; | |
165 | icv[3] = crc >> 24; | |
166 | ||
5a656949 | 167 | crypto_cipher_setkey(wep->tx_tfm, key, klen); |
b453872c JG |
168 | sg.page = virt_to_page(pos); |
169 | sg.offset = offset_in_page(pos); | |
170 | sg.length = len + 4; | |
5a656949 | 171 | crypto_cipher_encrypt(wep->tx_tfm, &sg, &sg, len + 4); |
b453872c JG |
172 | |
173 | return 0; | |
174 | } | |
175 | ||
b453872c JG |
176 | /* Perform WEP decryption on given buffer. Buffer includes whole WEP part of |
177 | * the frame: IV (4 bytes), encrypted payload (including SNAP header), | |
178 | * ICV (4 bytes). len includes both IV and ICV. | |
179 | * | |
180 | * Returns 0 if frame was decrypted successfully and ICV was correct and -1 on | |
181 | * failure. If frame is OK, IV and ICV will be removed. | |
182 | */ | |
183 | static int prism2_wep_decrypt(struct sk_buff *skb, int hdr_len, void *priv) | |
184 | { | |
185 | struct prism2_wep_data *wep = priv; | |
186 | u32 crc, klen, plen; | |
187 | u8 key[WEP_KEY_LEN + 3]; | |
188 | u8 keyidx, *pos, icv[4]; | |
189 | struct scatterlist sg; | |
190 | ||
191 | if (skb->len < hdr_len + 8) | |
192 | return -1; | |
193 | ||
194 | pos = skb->data + hdr_len; | |
195 | key[0] = *pos++; | |
196 | key[1] = *pos++; | |
197 | key[2] = *pos++; | |
198 | keyidx = *pos++ >> 6; | |
199 | if (keyidx != wep->key_idx) | |
200 | return -1; | |
201 | ||
202 | klen = 3 + wep->key_len; | |
203 | ||
204 | /* Copy rest of the WEP key (the secret part) */ | |
205 | memcpy(key + 3, wep->key, wep->key_len); | |
206 | ||
207 | /* Apply RC4 to data and compute CRC32 over decrypted data */ | |
208 | plen = skb->len - hdr_len - 8; | |
209 | ||
5a656949 | 210 | crypto_cipher_setkey(wep->rx_tfm, key, klen); |
b453872c JG |
211 | sg.page = virt_to_page(pos); |
212 | sg.offset = offset_in_page(pos); | |
213 | sg.length = plen + 4; | |
5a656949 | 214 | crypto_cipher_decrypt(wep->rx_tfm, &sg, &sg, plen + 4); |
b453872c JG |
215 | |
216 | crc = ~crc32_le(~0, pos, plen); | |
217 | icv[0] = crc; | |
218 | icv[1] = crc >> 8; | |
219 | icv[2] = crc >> 16; | |
220 | icv[3] = crc >> 24; | |
221 | if (memcmp(icv, pos + plen, 4) != 0) { | |
222 | /* ICV mismatch - drop frame */ | |
223 | return -2; | |
224 | } | |
225 | ||
226 | /* Remove IV and ICV */ | |
227 | memmove(skb->data + 4, skb->data, hdr_len); | |
228 | skb_pull(skb, 4); | |
229 | skb_trim(skb, skb->len - 4); | |
230 | ||
231 | return 0; | |
232 | } | |
233 | ||
0edd5b44 | 234 | static int prism2_wep_set_key(void *key, int len, u8 * seq, void *priv) |
b453872c JG |
235 | { |
236 | struct prism2_wep_data *wep = priv; | |
237 | ||
238 | if (len < 0 || len > WEP_KEY_LEN) | |
239 | return -1; | |
240 | ||
241 | memcpy(wep->key, key, len); | |
242 | wep->key_len = len; | |
243 | ||
244 | return 0; | |
245 | } | |
246 | ||
0edd5b44 | 247 | static int prism2_wep_get_key(void *key, int len, u8 * seq, void *priv) |
b453872c JG |
248 | { |
249 | struct prism2_wep_data *wep = priv; | |
250 | ||
251 | if (len < wep->key_len) | |
252 | return -1; | |
253 | ||
254 | memcpy(key, wep->key, wep->key_len); | |
255 | ||
256 | return wep->key_len; | |
257 | } | |
258 | ||
0edd5b44 | 259 | static char *prism2_wep_print_stats(char *p, void *priv) |
b453872c JG |
260 | { |
261 | struct prism2_wep_data *wep = priv; | |
0edd5b44 | 262 | p += sprintf(p, "key[%d] alg=WEP len=%d\n", wep->key_idx, wep->key_len); |
b453872c JG |
263 | return p; |
264 | } | |
265 | ||
b453872c | 266 | static struct ieee80211_crypto_ops ieee80211_crypt_wep = { |
74079fdc JK |
267 | .name = "WEP", |
268 | .init = prism2_wep_init, | |
269 | .deinit = prism2_wep_deinit, | |
a4bf26f3 | 270 | .build_iv = prism2_wep_build_iv, |
74079fdc JK |
271 | .encrypt_mpdu = prism2_wep_encrypt, |
272 | .decrypt_mpdu = prism2_wep_decrypt, | |
273 | .encrypt_msdu = NULL, | |
274 | .decrypt_msdu = NULL, | |
275 | .set_key = prism2_wep_set_key, | |
276 | .get_key = prism2_wep_get_key, | |
277 | .print_stats = prism2_wep_print_stats, | |
1264fc04 JK |
278 | .extra_mpdu_prefix_len = 4, /* IV */ |
279 | .extra_mpdu_postfix_len = 4, /* ICV */ | |
74079fdc | 280 | .owner = THIS_MODULE, |
b453872c JG |
281 | }; |
282 | ||
b453872c JG |
283 | static int __init ieee80211_crypto_wep_init(void) |
284 | { | |
285 | return ieee80211_register_crypto_ops(&ieee80211_crypt_wep); | |
286 | } | |
287 | ||
b453872c JG |
288 | static void __exit ieee80211_crypto_wep_exit(void) |
289 | { | |
290 | ieee80211_unregister_crypto_ops(&ieee80211_crypt_wep); | |
291 | } | |
292 | ||
b453872c JG |
293 | module_init(ieee80211_crypto_wep_init); |
294 | module_exit(ieee80211_crypto_wep_exit); |