Commit | Line | Data |
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b453872c | 1 | /* |
274bfb8d | 2 | * lib80211 crypt: host-based WEP encryption implementation for lib80211 |
b453872c | 3 | * |
85d32e7b | 4 | * Copyright (c) 2002-2004, Jouni Malinen <j@w1.fi> |
274bfb8d | 5 | * Copyright (c) 2008, John W. Linville <linville@tuxdriver.com> |
b453872c JG |
6 | * |
7 | * This program is free software; you can redistribute it and/or modify | |
8 | * it under the terms of the GNU General Public License version 2 as | |
9 | * published by the Free Software Foundation. See README and COPYING for | |
10 | * more details. | |
11 | */ | |
12 | ||
f12cc209 | 13 | #include <linux/err.h> |
b453872c JG |
14 | #include <linux/module.h> |
15 | #include <linux/init.h> | |
16 | #include <linux/slab.h> | |
17 | #include <linux/random.h> | |
11763609 | 18 | #include <linux/scatterlist.h> |
b453872c | 19 | #include <linux/skbuff.h> |
d7fe0f24 | 20 | #include <linux/mm.h> |
b453872c JG |
21 | #include <asm/string.h> |
22 | ||
274bfb8d | 23 | #include <net/lib80211.h> |
b453872c | 24 | |
b453872c | 25 | #include <linux/crypto.h> |
b453872c JG |
26 | #include <linux/crc32.h> |
27 | ||
28 | MODULE_AUTHOR("Jouni Malinen"); | |
274bfb8d | 29 | MODULE_DESCRIPTION("lib80211 crypt: WEP"); |
b453872c JG |
30 | MODULE_LICENSE("GPL"); |
31 | ||
274bfb8d | 32 | struct lib80211_wep_data { |
b453872c JG |
33 | u32 iv; |
34 | #define WEP_KEY_LEN 13 | |
35 | u8 key[WEP_KEY_LEN + 1]; | |
36 | u8 key_len; | |
37 | u8 key_idx; | |
28eb177d JG |
38 | struct crypto_blkcipher *tx_tfm; |
39 | struct crypto_blkcipher *rx_tfm; | |
b453872c JG |
40 | }; |
41 | ||
274bfb8d | 42 | static void *lib80211_wep_init(int keyidx) |
b453872c | 43 | { |
274bfb8d | 44 | struct lib80211_wep_data *priv; |
b453872c | 45 | |
0da974f4 | 46 | priv = kzalloc(sizeof(*priv), GFP_ATOMIC); |
b453872c JG |
47 | if (priv == NULL) |
48 | goto fail; | |
b453872c JG |
49 | priv->key_idx = keyidx; |
50 | ||
28eb177d JG |
51 | priv->tx_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0, CRYPTO_ALG_ASYNC); |
52 | if (IS_ERR(priv->tx_tfm)) { | |
274bfb8d | 53 | printk(KERN_DEBUG "lib80211_crypt_wep: could not allocate " |
b453872c | 54 | "crypto API arc4\n"); |
18379879 | 55 | priv->tx_tfm = NULL; |
b453872c JG |
56 | goto fail; |
57 | } | |
58 | ||
28eb177d JG |
59 | priv->rx_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0, CRYPTO_ALG_ASYNC); |
60 | if (IS_ERR(priv->rx_tfm)) { | |
274bfb8d | 61 | printk(KERN_DEBUG "lib80211_crypt_wep: could not allocate " |
5a656949 | 62 | "crypto API arc4\n"); |
18379879 | 63 | priv->rx_tfm = NULL; |
5a656949 ZY |
64 | goto fail; |
65 | } | |
b453872c JG |
66 | /* start WEP IV from a random value */ |
67 | get_random_bytes(&priv->iv, 4); | |
68 | ||
69 | return priv; | |
70 | ||
0edd5b44 | 71 | fail: |
b453872c | 72 | if (priv) { |
5a656949 | 73 | if (priv->tx_tfm) |
28eb177d | 74 | crypto_free_blkcipher(priv->tx_tfm); |
5a656949 | 75 | if (priv->rx_tfm) |
28eb177d | 76 | crypto_free_blkcipher(priv->rx_tfm); |
b453872c JG |
77 | kfree(priv); |
78 | } | |
79 | return NULL; | |
80 | } | |
81 | ||
274bfb8d | 82 | static void lib80211_wep_deinit(void *priv) |
b453872c | 83 | { |
274bfb8d | 84 | struct lib80211_wep_data *_priv = priv; |
5a656949 ZY |
85 | if (_priv) { |
86 | if (_priv->tx_tfm) | |
28eb177d | 87 | crypto_free_blkcipher(_priv->tx_tfm); |
5a656949 | 88 | if (_priv->rx_tfm) |
28eb177d | 89 | crypto_free_blkcipher(_priv->rx_tfm); |
5a656949 | 90 | } |
b453872c JG |
91 | kfree(priv); |
92 | } | |
93 | ||
a4bf26f3 | 94 | /* Add WEP IV/key info to a frame that has at least 4 bytes of headroom */ |
274bfb8d | 95 | static int lib80211_wep_build_iv(struct sk_buff *skb, int hdr_len, |
9184d934 | 96 | u8 *key, int keylen, void *priv) |
b453872c | 97 | { |
274bfb8d | 98 | struct lib80211_wep_data *wep = priv; |
6572e91d | 99 | u32 klen; |
a4bf26f3 | 100 | u8 *pos; |
64265651 | 101 | |
a4bf26f3 | 102 | if (skb_headroom(skb) < 4 || skb->len < hdr_len) |
b453872c JG |
103 | return -1; |
104 | ||
b453872c JG |
105 | pos = skb_push(skb, 4); |
106 | memmove(pos, pos + 4, hdr_len); | |
107 | pos += hdr_len; | |
108 | ||
109 | klen = 3 + wep->key_len; | |
110 | ||
111 | wep->iv++; | |
112 | ||
113 | /* Fluhrer, Mantin, and Shamir have reported weaknesses in the key | |
114 | * scheduling algorithm of RC4. At least IVs (KeyByte + 3, 0xff, N) | |
115 | * can be used to speedup attacks, so avoid using them. */ | |
116 | if ((wep->iv & 0xff00) == 0xff00) { | |
117 | u8 B = (wep->iv >> 16) & 0xff; | |
118 | if (B >= 3 && B < klen) | |
119 | wep->iv += 0x0100; | |
120 | } | |
121 | ||
122 | /* Prepend 24-bit IV to RC4 key and TX frame */ | |
a4bf26f3 JB |
123 | *pos++ = (wep->iv >> 16) & 0xff; |
124 | *pos++ = (wep->iv >> 8) & 0xff; | |
125 | *pos++ = wep->iv & 0xff; | |
b453872c JG |
126 | *pos++ = wep->key_idx << 6; |
127 | ||
a4bf26f3 JB |
128 | return 0; |
129 | } | |
130 | ||
131 | /* Perform WEP encryption on given skb that has at least 4 bytes of headroom | |
132 | * for IV and 4 bytes of tailroom for ICV. Both IV and ICV will be transmitted, | |
133 | * so the payload length increases with 8 bytes. | |
134 | * | |
135 | * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data)) | |
136 | */ | |
274bfb8d | 137 | static int lib80211_wep_encrypt(struct sk_buff *skb, int hdr_len, void *priv) |
a4bf26f3 | 138 | { |
274bfb8d | 139 | struct lib80211_wep_data *wep = priv; |
28eb177d | 140 | struct blkcipher_desc desc = { .tfm = wep->tx_tfm }; |
a4bf26f3 JB |
141 | u32 crc, klen, len; |
142 | u8 *pos, *icv; | |
143 | struct scatterlist sg; | |
144 | u8 key[WEP_KEY_LEN + 3]; | |
145 | ||
274bfb8d | 146 | /* other checks are in lib80211_wep_build_iv */ |
a4bf26f3 JB |
147 | if (skb_tailroom(skb) < 4) |
148 | return -1; | |
64265651 | 149 | |
a4bf26f3 | 150 | /* add the IV to the frame */ |
274bfb8d | 151 | if (lib80211_wep_build_iv(skb, hdr_len, NULL, 0, priv)) |
a4bf26f3 | 152 | return -1; |
64265651 | 153 | |
a4bf26f3 | 154 | /* Copy the IV into the first 3 bytes of the key */ |
d626f62b | 155 | skb_copy_from_linear_data_offset(skb, hdr_len, key, 3); |
a4bf26f3 | 156 | |
b453872c JG |
157 | /* Copy rest of the WEP key (the secret part) */ |
158 | memcpy(key + 3, wep->key, wep->key_len); | |
64265651 | 159 | |
a4bf26f3 JB |
160 | len = skb->len - hdr_len - 4; |
161 | pos = skb->data + hdr_len + 4; | |
162 | klen = 3 + wep->key_len; | |
b453872c | 163 | |
a4bf26f3 | 164 | /* Append little-endian CRC32 over only the data and encrypt it to produce ICV */ |
b453872c JG |
165 | crc = ~crc32_le(~0, pos, len); |
166 | icv = skb_put(skb, 4); | |
167 | icv[0] = crc; | |
168 | icv[1] = crc >> 8; | |
169 | icv[2] = crc >> 16; | |
170 | icv[3] = crc >> 24; | |
171 | ||
28eb177d | 172 | crypto_blkcipher_setkey(wep->tx_tfm, key, klen); |
fa05f128 | 173 | sg_init_one(&sg, pos, len + 4); |
f12cc209 | 174 | return crypto_blkcipher_encrypt(&desc, &sg, &sg, len + 4); |
b453872c JG |
175 | } |
176 | ||
b453872c JG |
177 | /* Perform WEP decryption on given buffer. Buffer includes whole WEP part of |
178 | * the frame: IV (4 bytes), encrypted payload (including SNAP header), | |
179 | * ICV (4 bytes). len includes both IV and ICV. | |
180 | * | |
181 | * Returns 0 if frame was decrypted successfully and ICV was correct and -1 on | |
182 | * failure. If frame is OK, IV and ICV will be removed. | |
183 | */ | |
274bfb8d | 184 | static int lib80211_wep_decrypt(struct sk_buff *skb, int hdr_len, void *priv) |
b453872c | 185 | { |
274bfb8d | 186 | struct lib80211_wep_data *wep = priv; |
28eb177d | 187 | struct blkcipher_desc desc = { .tfm = wep->rx_tfm }; |
b453872c JG |
188 | u32 crc, klen, plen; |
189 | u8 key[WEP_KEY_LEN + 3]; | |
190 | u8 keyidx, *pos, icv[4]; | |
191 | struct scatterlist sg; | |
192 | ||
193 | if (skb->len < hdr_len + 8) | |
194 | return -1; | |
195 | ||
196 | pos = skb->data + hdr_len; | |
197 | key[0] = *pos++; | |
198 | key[1] = *pos++; | |
199 | key[2] = *pos++; | |
200 | keyidx = *pos++ >> 6; | |
201 | if (keyidx != wep->key_idx) | |
202 | return -1; | |
203 | ||
204 | klen = 3 + wep->key_len; | |
205 | ||
206 | /* Copy rest of the WEP key (the secret part) */ | |
207 | memcpy(key + 3, wep->key, wep->key_len); | |
208 | ||
209 | /* Apply RC4 to data and compute CRC32 over decrypted data */ | |
210 | plen = skb->len - hdr_len - 8; | |
211 | ||
28eb177d | 212 | crypto_blkcipher_setkey(wep->rx_tfm, key, klen); |
fa05f128 | 213 | sg_init_one(&sg, pos, plen + 4); |
f12cc209 HX |
214 | if (crypto_blkcipher_decrypt(&desc, &sg, &sg, plen + 4)) |
215 | return -7; | |
b453872c JG |
216 | |
217 | crc = ~crc32_le(~0, pos, plen); | |
218 | icv[0] = crc; | |
219 | icv[1] = crc >> 8; | |
220 | icv[2] = crc >> 16; | |
221 | icv[3] = crc >> 24; | |
222 | if (memcmp(icv, pos + plen, 4) != 0) { | |
223 | /* ICV mismatch - drop frame */ | |
224 | return -2; | |
225 | } | |
226 | ||
227 | /* Remove IV and ICV */ | |
228 | memmove(skb->data + 4, skb->data, hdr_len); | |
229 | skb_pull(skb, 4); | |
230 | skb_trim(skb, skb->len - 4); | |
231 | ||
232 | return 0; | |
233 | } | |
234 | ||
274bfb8d | 235 | static int lib80211_wep_set_key(void *key, int len, u8 * seq, void *priv) |
b453872c | 236 | { |
274bfb8d | 237 | struct lib80211_wep_data *wep = priv; |
b453872c JG |
238 | |
239 | if (len < 0 || len > WEP_KEY_LEN) | |
240 | return -1; | |
241 | ||
242 | memcpy(wep->key, key, len); | |
243 | wep->key_len = len; | |
244 | ||
245 | return 0; | |
246 | } | |
247 | ||
274bfb8d | 248 | static int lib80211_wep_get_key(void *key, int len, u8 * seq, void *priv) |
b453872c | 249 | { |
274bfb8d | 250 | struct lib80211_wep_data *wep = priv; |
b453872c JG |
251 | |
252 | if (len < wep->key_len) | |
253 | return -1; | |
254 | ||
255 | memcpy(key, wep->key, wep->key_len); | |
256 | ||
257 | return wep->key_len; | |
258 | } | |
259 | ||
274bfb8d | 260 | static char *lib80211_wep_print_stats(char *p, void *priv) |
b453872c | 261 | { |
274bfb8d | 262 | struct lib80211_wep_data *wep = priv; |
0edd5b44 | 263 | p += sprintf(p, "key[%d] alg=WEP len=%d\n", wep->key_idx, wep->key_len); |
b453872c JG |
264 | return p; |
265 | } | |
266 | ||
274bfb8d | 267 | static struct lib80211_crypto_ops lib80211_crypt_wep = { |
74079fdc | 268 | .name = "WEP", |
274bfb8d JL |
269 | .init = lib80211_wep_init, |
270 | .deinit = lib80211_wep_deinit, | |
274bfb8d JL |
271 | .encrypt_mpdu = lib80211_wep_encrypt, |
272 | .decrypt_mpdu = lib80211_wep_decrypt, | |
74079fdc JK |
273 | .encrypt_msdu = NULL, |
274 | .decrypt_msdu = NULL, | |
274bfb8d JL |
275 | .set_key = lib80211_wep_set_key, |
276 | .get_key = lib80211_wep_get_key, | |
277 | .print_stats = lib80211_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 | ||
274bfb8d | 283 | static int __init lib80211_crypto_wep_init(void) |
b453872c | 284 | { |
274bfb8d | 285 | return lib80211_register_crypto_ops(&lib80211_crypt_wep); |
b453872c JG |
286 | } |
287 | ||
274bfb8d | 288 | static void __exit lib80211_crypto_wep_exit(void) |
b453872c | 289 | { |
274bfb8d | 290 | lib80211_unregister_crypto_ops(&lib80211_crypt_wep); |
b453872c JG |
291 | } |
292 | ||
274bfb8d JL |
293 | module_init(lib80211_crypto_wep_init); |
294 | module_exit(lib80211_crypto_wep_exit); |