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Jeff Garzikb4538722005-05-12 22:48:20 -04001/*
2 * Host AP crypt: host-based WEP encryption implementation for Host AP driver
3 *
Jouni Malinen85d32e72007-03-24 17:15:30 -07004 * Copyright (c) 2002-2004, Jouni Malinen <j@w1.fi>
Jeff Garzikb4538722005-05-12 22:48:20 -04005 *
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
Herbert Xuf12cc202006-08-22 20:36:13 +100012#include <linux/err.h>
Jeff Garzikb4538722005-05-12 22:48:20 -040013#include <linux/module.h>
14#include <linux/init.h>
15#include <linux/slab.h>
16#include <linux/random.h>
Ralf Baechle11763602007-10-23 20:42:11 +020017#include <linux/scatterlist.h>
Jeff Garzikb4538722005-05-12 22:48:20 -040018#include <linux/skbuff.h>
Al Virod7fe0f22006-12-03 23:15:30 -050019#include <linux/mm.h>
Jeff Garzikb4538722005-05-12 22:48:20 -040020#include <asm/string.h>
21
22#include <net/ieee80211.h>
23
Jeff Garzikb4538722005-05-12 22:48:20 -040024#include <linux/crypto.h>
Jeff Garzikb4538722005-05-12 22:48:20 -040025#include <linux/crc32.h>
26
27MODULE_AUTHOR("Jouni Malinen");
28MODULE_DESCRIPTION("Host AP crypt: WEP");
29MODULE_LICENSE("GPL");
30
Jeff Garzikb4538722005-05-12 22:48:20 -040031struct 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;
Jeff Garzik28eb1772006-09-22 20:10:23 -040037 struct crypto_blkcipher *tx_tfm;
38 struct crypto_blkcipher *rx_tfm;
Jeff Garzikb4538722005-05-12 22:48:20 -040039};
40
James Ketrenos6eb6edf2005-09-22 10:34:15 +000041static void *prism2_wep_init(int keyidx)
Jeff Garzikb4538722005-05-12 22:48:20 -040042{
43 struct prism2_wep_data *priv;
44
Panagiotis Issaris0da974f2006-07-21 14:51:30 -070045 priv = kzalloc(sizeof(*priv), GFP_ATOMIC);
Jeff Garzikb4538722005-05-12 22:48:20 -040046 if (priv == NULL)
47 goto fail;
Jeff Garzikb4538722005-05-12 22:48:20 -040048 priv->key_idx = keyidx;
49
Jeff Garzik28eb1772006-09-22 20:10:23 -040050 priv->tx_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0, CRYPTO_ALG_ASYNC);
51 if (IS_ERR(priv->tx_tfm)) {
Jeff Garzikb4538722005-05-12 22:48:20 -040052 printk(KERN_DEBUG "ieee80211_crypt_wep: could not allocate "
53 "crypto API arc4\n");
Jeff Garzik18379872006-09-22 21:19:05 -040054 priv->tx_tfm = NULL;
Jeff Garzikb4538722005-05-12 22:48:20 -040055 goto fail;
56 }
57
Jeff Garzik28eb1772006-09-22 20:10:23 -040058 priv->rx_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0, CRYPTO_ALG_ASYNC);
59 if (IS_ERR(priv->rx_tfm)) {
Zhu Yi5a656942006-08-21 11:33:56 +080060 printk(KERN_DEBUG "ieee80211_crypt_wep: could not allocate "
61 "crypto API arc4\n");
Jeff Garzik18379872006-09-22 21:19:05 -040062 priv->rx_tfm = NULL;
Zhu Yi5a656942006-08-21 11:33:56 +080063 goto fail;
64 }
Jeff Garzikb4538722005-05-12 22:48:20 -040065 /* start WEP IV from a random value */
66 get_random_bytes(&priv->iv, 4);
67
68 return priv;
69
Jeff Garzik0edd5b42005-09-07 00:48:31 -040070 fail:
Jeff Garzikb4538722005-05-12 22:48:20 -040071 if (priv) {
Zhu Yi5a656942006-08-21 11:33:56 +080072 if (priv->tx_tfm)
Jeff Garzik28eb1772006-09-22 20:10:23 -040073 crypto_free_blkcipher(priv->tx_tfm);
Zhu Yi5a656942006-08-21 11:33:56 +080074 if (priv->rx_tfm)
Jeff Garzik28eb1772006-09-22 20:10:23 -040075 crypto_free_blkcipher(priv->rx_tfm);
Jeff Garzikb4538722005-05-12 22:48:20 -040076 kfree(priv);
77 }
78 return NULL;
79}
80
Jeff Garzikb4538722005-05-12 22:48:20 -040081static void prism2_wep_deinit(void *priv)
82{
83 struct prism2_wep_data *_priv = priv;
Zhu Yi5a656942006-08-21 11:33:56 +080084 if (_priv) {
85 if (_priv->tx_tfm)
Jeff Garzik28eb1772006-09-22 20:10:23 -040086 crypto_free_blkcipher(_priv->tx_tfm);
Zhu Yi5a656942006-08-21 11:33:56 +080087 if (_priv->rx_tfm)
Jeff Garzik28eb1772006-09-22 20:10:23 -040088 crypto_free_blkcipher(_priv->rx_tfm);
Zhu Yi5a656942006-08-21 11:33:56 +080089 }
Jeff Garzikb4538722005-05-12 22:48:20 -040090 kfree(priv);
91}
92
Johannes Berga4bf26f2005-12-31 11:35:20 +010093/* Add WEP IV/key info to a frame that has at least 4 bytes of headroom */
Zhu Yi9184d932006-01-19 16:22:32 +080094static int prism2_wep_build_iv(struct sk_buff *skb, int hdr_len,
95 u8 *key, int keylen, void *priv)
Jeff Garzikb4538722005-05-12 22:48:20 -040096{
97 struct prism2_wep_data *wep = priv;
Johannes Berga4bf26f2005-12-31 11:35:20 +010098 u32 klen, len;
99 u8 *pos;
YOSHIFUJI Hideaki64265652007-02-09 23:24:46 +0900100
Johannes Berga4bf26f2005-12-31 11:35:20 +0100101 if (skb_headroom(skb) < 4 || skb->len < hdr_len)
Jeff Garzikb4538722005-05-12 22:48:20 -0400102 return -1;
103
104 len = skb->len - hdr_len;
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 */
Johannes Berga4bf26f2005-12-31 11:35:20 +0100123 *pos++ = (wep->iv >> 16) & 0xff;
124 *pos++ = (wep->iv >> 8) & 0xff;
125 *pos++ = wep->iv & 0xff;
Jeff Garzikb4538722005-05-12 22:48:20 -0400126 *pos++ = wep->key_idx << 6;
127
Johannes Berga4bf26f2005-12-31 11:35:20 +0100128 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 */
137static int prism2_wep_encrypt(struct sk_buff *skb, int hdr_len, void *priv)
138{
139 struct prism2_wep_data *wep = priv;
Jeff Garzik28eb1772006-09-22 20:10:23 -0400140 struct blkcipher_desc desc = { .tfm = wep->tx_tfm };
Johannes Berga4bf26f2005-12-31 11:35:20 +0100141 u32 crc, klen, len;
142 u8 *pos, *icv;
143 struct scatterlist sg;
144 u8 key[WEP_KEY_LEN + 3];
145
146 /* other checks are in prism2_wep_build_iv */
147 if (skb_tailroom(skb) < 4)
148 return -1;
YOSHIFUJI Hideaki64265652007-02-09 23:24:46 +0900149
Johannes Berga4bf26f2005-12-31 11:35:20 +0100150 /* add the IV to the frame */
Zhu Yi9184d932006-01-19 16:22:32 +0800151 if (prism2_wep_build_iv(skb, hdr_len, NULL, 0, priv))
Johannes Berga4bf26f2005-12-31 11:35:20 +0100152 return -1;
YOSHIFUJI Hideaki64265652007-02-09 23:24:46 +0900153
Johannes Berga4bf26f2005-12-31 11:35:20 +0100154 /* Copy the IV into the first 3 bytes of the key */
Arnaldo Carvalho de Melod626f622007-03-27 18:55:52 -0300155 skb_copy_from_linear_data_offset(skb, hdr_len, key, 3);
Johannes Berga4bf26f2005-12-31 11:35:20 +0100156
Jeff Garzikb4538722005-05-12 22:48:20 -0400157 /* Copy rest of the WEP key (the secret part) */
158 memcpy(key + 3, wep->key, wep->key_len);
YOSHIFUJI Hideaki64265652007-02-09 23:24:46 +0900159
Johannes Berga4bf26f2005-12-31 11:35:20 +0100160 len = skb->len - hdr_len - 4;
161 pos = skb->data + hdr_len + 4;
162 klen = 3 + wep->key_len;
Jeff Garzikb4538722005-05-12 22:48:20 -0400163
Johannes Berga4bf26f2005-12-31 11:35:20 +0100164 /* Append little-endian CRC32 over only the data and encrypt it to produce ICV */
Jeff Garzikb4538722005-05-12 22:48:20 -0400165 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
Jeff Garzik28eb1772006-09-22 20:10:23 -0400172 crypto_blkcipher_setkey(wep->tx_tfm, key, klen);
Jens Axboefa05f122007-10-22 19:44:26 +0200173 sg_init_one(&sg, pos, len + 4);
Herbert Xuf12cc202006-08-22 20:36:13 +1000174 return crypto_blkcipher_encrypt(&desc, &sg, &sg, len + 4);
Jeff Garzikb4538722005-05-12 22:48:20 -0400175}
176
Jeff Garzikb4538722005-05-12 22:48:20 -0400177/* 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 */
184static int prism2_wep_decrypt(struct sk_buff *skb, int hdr_len, void *priv)
185{
186 struct prism2_wep_data *wep = priv;
Jeff Garzik28eb1772006-09-22 20:10:23 -0400187 struct blkcipher_desc desc = { .tfm = wep->rx_tfm };
Jeff Garzikb4538722005-05-12 22:48:20 -0400188 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
Jeff Garzik28eb1772006-09-22 20:10:23 -0400212 crypto_blkcipher_setkey(wep->rx_tfm, key, klen);
Jens Axboefa05f122007-10-22 19:44:26 +0200213 sg_init_one(&sg, pos, plen + 4);
Herbert Xuf12cc202006-08-22 20:36:13 +1000214 if (crypto_blkcipher_decrypt(&desc, &sg, &sg, plen + 4))
215 return -7;
Jeff Garzikb4538722005-05-12 22:48:20 -0400216
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
Jeff Garzik0edd5b42005-09-07 00:48:31 -0400235static int prism2_wep_set_key(void *key, int len, u8 * seq, void *priv)
Jeff Garzikb4538722005-05-12 22:48:20 -0400236{
237 struct prism2_wep_data *wep = priv;
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
Jeff Garzik0edd5b42005-09-07 00:48:31 -0400248static int prism2_wep_get_key(void *key, int len, u8 * seq, void *priv)
Jeff Garzikb4538722005-05-12 22:48:20 -0400249{
250 struct prism2_wep_data *wep = priv;
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
Jeff Garzik0edd5b42005-09-07 00:48:31 -0400260static char *prism2_wep_print_stats(char *p, void *priv)
Jeff Garzikb4538722005-05-12 22:48:20 -0400261{
262 struct prism2_wep_data *wep = priv;
Jeff Garzik0edd5b42005-09-07 00:48:31 -0400263 p += sprintf(p, "key[%d] alg=WEP len=%d\n", wep->key_idx, wep->key_len);
Jeff Garzikb4538722005-05-12 22:48:20 -0400264 return p;
265}
266
Jeff Garzikb4538722005-05-12 22:48:20 -0400267static struct ieee80211_crypto_ops ieee80211_crypt_wep = {
James Ketrenos74079fd2005-09-13 17:35:21 -0500268 .name = "WEP",
269 .init = prism2_wep_init,
270 .deinit = prism2_wep_deinit,
Johannes Berga4bf26f2005-12-31 11:35:20 +0100271 .build_iv = prism2_wep_build_iv,
James Ketrenos74079fd2005-09-13 17:35:21 -0500272 .encrypt_mpdu = prism2_wep_encrypt,
273 .decrypt_mpdu = prism2_wep_decrypt,
274 .encrypt_msdu = NULL,
275 .decrypt_msdu = NULL,
276 .set_key = prism2_wep_set_key,
277 .get_key = prism2_wep_get_key,
278 .print_stats = prism2_wep_print_stats,
James Ketrenos1264fc02005-09-21 11:54:53 -0500279 .extra_mpdu_prefix_len = 4, /* IV */
280 .extra_mpdu_postfix_len = 4, /* ICV */
James Ketrenos74079fd2005-09-13 17:35:21 -0500281 .owner = THIS_MODULE,
Jeff Garzikb4538722005-05-12 22:48:20 -0400282};
283
Jeff Garzikb4538722005-05-12 22:48:20 -0400284static int __init ieee80211_crypto_wep_init(void)
285{
286 return ieee80211_register_crypto_ops(&ieee80211_crypt_wep);
287}
288
Jeff Garzikb4538722005-05-12 22:48:20 -0400289static void __exit ieee80211_crypto_wep_exit(void)
290{
291 ieee80211_unregister_crypto_ops(&ieee80211_crypt_wep);
292}
293
Jeff Garzikb4538722005-05-12 22:48:20 -0400294module_init(ieee80211_crypto_wep_init);
295module_exit(ieee80211_crypto_wep_exit);