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