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