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[linux-2.6.19-moxart.git] / net / ieee80211 / ieee80211_crypt_wep.c
blob1b2efff11d39ff63fab9935e070b62d01897c193
1 /*
2 * Host AP crypt: host-based WEP encryption implementation for Host AP driver
4 * Copyright (c) 2002-2004, Jouni Malinen <jkmaline@cc.hut.fi>
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.
12 #include <linux/err.h>
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>
20 #include <net/ieee80211.h>
22 #include <linux/crypto.h>
23 #include <asm/scatterlist.h>
24 #include <linux/crc32.h>
26 MODULE_AUTHOR("Jouni Malinen");
27 MODULE_DESCRIPTION("Host AP crypt: WEP");
28 MODULE_LICENSE("GPL");
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_blkcipher *tx_tfm;
37 struct crypto_blkcipher *rx_tfm;
40 static void *prism2_wep_init(int keyidx)
42 struct prism2_wep_data *priv;
44 priv = kzalloc(sizeof(*priv), GFP_ATOMIC);
45 if (priv == NULL)
46 goto fail;
47 priv->key_idx = keyidx;
49 priv->tx_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0, CRYPTO_ALG_ASYNC);
50 if (IS_ERR(priv->tx_tfm)) {
51 printk(KERN_DEBUG "ieee80211_crypt_wep: could not allocate "
52 "crypto API arc4\n");
53 priv->tx_tfm = NULL;
54 goto fail;
57 priv->rx_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0, CRYPTO_ALG_ASYNC);
58 if (IS_ERR(priv->rx_tfm)) {
59 printk(KERN_DEBUG "ieee80211_crypt_wep: could not allocate "
60 "crypto API arc4\n");
61 priv->rx_tfm = NULL;
62 goto fail;
64 /* start WEP IV from a random value */
65 get_random_bytes(&priv->iv, 4);
67 return priv;
69 fail:
70 if (priv) {
71 if (priv->tx_tfm)
72 crypto_free_blkcipher(priv->tx_tfm);
73 if (priv->rx_tfm)
74 crypto_free_blkcipher(priv->rx_tfm);
75 kfree(priv);
77 return NULL;
80 static void prism2_wep_deinit(void *priv)
82 struct prism2_wep_data *_priv = priv;
83 if (_priv) {
84 if (_priv->tx_tfm)
85 crypto_free_blkcipher(_priv->tx_tfm);
86 if (_priv->rx_tfm)
87 crypto_free_blkcipher(_priv->rx_tfm);
89 kfree(priv);
92 /* Add WEP IV/key info to a frame that has at least 4 bytes of headroom */
93 static int prism2_wep_build_iv(struct sk_buff *skb, int hdr_len,
94 u8 *key, int keylen, void *priv)
96 struct prism2_wep_data *wep = priv;
97 u32 klen, len;
98 u8 *pos;
100 if (skb_headroom(skb) < 4 || skb->len < hdr_len)
101 return -1;
103 len = skb->len - hdr_len;
104 pos = skb_push(skb, 4);
105 memmove(pos, pos + 4, hdr_len);
106 pos += hdr_len;
108 klen = 3 + wep->key_len;
110 wep->iv++;
112 /* Fluhrer, Mantin, and Shamir have reported weaknesses in the key
113 * scheduling algorithm of RC4. At least IVs (KeyByte + 3, 0xff, N)
114 * can be used to speedup attacks, so avoid using them. */
115 if ((wep->iv & 0xff00) == 0xff00) {
116 u8 B = (wep->iv >> 16) & 0xff;
117 if (B >= 3 && B < klen)
118 wep->iv += 0x0100;
121 /* Prepend 24-bit IV to RC4 key and TX frame */
122 *pos++ = (wep->iv >> 16) & 0xff;
123 *pos++ = (wep->iv >> 8) & 0xff;
124 *pos++ = wep->iv & 0xff;
125 *pos++ = wep->key_idx << 6;
127 return 0;
130 /* Perform WEP encryption on given skb that has at least 4 bytes of headroom
131 * for IV and 4 bytes of tailroom for ICV. Both IV and ICV will be transmitted,
132 * so the payload length increases with 8 bytes.
134 * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data))
136 static int prism2_wep_encrypt(struct sk_buff *skb, int hdr_len, void *priv)
138 struct prism2_wep_data *wep = priv;
139 struct blkcipher_desc desc = { .tfm = wep->tx_tfm };
140 u32 crc, klen, len;
141 u8 *pos, *icv;
142 struct scatterlist sg;
143 u8 key[WEP_KEY_LEN + 3];
145 /* other checks are in prism2_wep_build_iv */
146 if (skb_tailroom(skb) < 4)
147 return -1;
149 /* add the IV to the frame */
150 if (prism2_wep_build_iv(skb, hdr_len, NULL, 0, priv))
151 return -1;
153 /* Copy the IV into the first 3 bytes of the key */
154 memcpy(key, skb->data + hdr_len, 3);
156 /* Copy rest of the WEP key (the secret part) */
157 memcpy(key + 3, wep->key, wep->key_len);
159 len = skb->len - hdr_len - 4;
160 pos = skb->data + hdr_len + 4;
161 klen = 3 + wep->key_len;
163 /* Append little-endian CRC32 over only the data and encrypt it to produce ICV */
164 crc = ~crc32_le(~0, pos, len);
165 icv = skb_put(skb, 4);
166 icv[0] = crc;
167 icv[1] = crc >> 8;
168 icv[2] = crc >> 16;
169 icv[3] = crc >> 24;
171 crypto_blkcipher_setkey(wep->tx_tfm, key, klen);
172 sg.page = virt_to_page(pos);
173 sg.offset = offset_in_page(pos);
174 sg.length = len + 4;
175 return crypto_blkcipher_encrypt(&desc, &sg, &sg, len + 4);
178 /* Perform WEP decryption on given buffer. Buffer includes whole WEP part of
179 * the frame: IV (4 bytes), encrypted payload (including SNAP header),
180 * ICV (4 bytes). len includes both IV and ICV.
182 * Returns 0 if frame was decrypted successfully and ICV was correct and -1 on
183 * failure. If frame is OK, IV and ICV will be removed.
185 static int prism2_wep_decrypt(struct sk_buff *skb, int hdr_len, void *priv)
187 struct prism2_wep_data *wep = priv;
188 struct blkcipher_desc desc = { .tfm = wep->rx_tfm };
189 u32 crc, klen, plen;
190 u8 key[WEP_KEY_LEN + 3];
191 u8 keyidx, *pos, icv[4];
192 struct scatterlist sg;
194 if (skb->len < hdr_len + 8)
195 return -1;
197 pos = skb->data + hdr_len;
198 key[0] = *pos++;
199 key[1] = *pos++;
200 key[2] = *pos++;
201 keyidx = *pos++ >> 6;
202 if (keyidx != wep->key_idx)
203 return -1;
205 klen = 3 + wep->key_len;
207 /* Copy rest of the WEP key (the secret part) */
208 memcpy(key + 3, wep->key, wep->key_len);
210 /* Apply RC4 to data and compute CRC32 over decrypted data */
211 plen = skb->len - hdr_len - 8;
213 crypto_blkcipher_setkey(wep->rx_tfm, key, klen);
214 sg.page = virt_to_page(pos);
215 sg.offset = offset_in_page(pos);
216 sg.length = plen + 4;
217 if (crypto_blkcipher_decrypt(&desc, &sg, &sg, plen + 4))
218 return -7;
220 crc = ~crc32_le(~0, pos, plen);
221 icv[0] = crc;
222 icv[1] = crc >> 8;
223 icv[2] = crc >> 16;
224 icv[3] = crc >> 24;
225 if (memcmp(icv, pos + plen, 4) != 0) {
226 /* ICV mismatch - drop frame */
227 return -2;
230 /* Remove IV and ICV */
231 memmove(skb->data + 4, skb->data, hdr_len);
232 skb_pull(skb, 4);
233 skb_trim(skb, skb->len - 4);
235 return 0;
238 static int prism2_wep_set_key(void *key, int len, u8 * seq, void *priv)
240 struct prism2_wep_data *wep = priv;
242 if (len < 0 || len > WEP_KEY_LEN)
243 return -1;
245 memcpy(wep->key, key, len);
246 wep->key_len = len;
248 return 0;
251 static int prism2_wep_get_key(void *key, int len, u8 * seq, void *priv)
253 struct prism2_wep_data *wep = priv;
255 if (len < wep->key_len)
256 return -1;
258 memcpy(key, wep->key, wep->key_len);
260 return wep->key_len;
263 static char *prism2_wep_print_stats(char *p, void *priv)
265 struct prism2_wep_data *wep = priv;
266 p += sprintf(p, "key[%d] alg=WEP len=%d\n", wep->key_idx, wep->key_len);
267 return p;
270 static struct ieee80211_crypto_ops ieee80211_crypt_wep = {
271 .name = "WEP",
272 .init = prism2_wep_init,
273 .deinit = prism2_wep_deinit,
274 .build_iv = prism2_wep_build_iv,
275 .encrypt_mpdu = prism2_wep_encrypt,
276 .decrypt_mpdu = prism2_wep_decrypt,
277 .encrypt_msdu = NULL,
278 .decrypt_msdu = NULL,
279 .set_key = prism2_wep_set_key,
280 .get_key = prism2_wep_get_key,
281 .print_stats = prism2_wep_print_stats,
282 .extra_mpdu_prefix_len = 4, /* IV */
283 .extra_mpdu_postfix_len = 4, /* ICV */
284 .owner = THIS_MODULE,
287 static int __init ieee80211_crypto_wep_init(void)
289 return ieee80211_register_crypto_ops(&ieee80211_crypt_wep);
292 static void __exit ieee80211_crypto_wep_exit(void)
294 ieee80211_unregister_crypto_ops(&ieee80211_crypt_wep);
297 module_init(ieee80211_crypto_wep_init);
298 module_exit(ieee80211_crypto_wep_exit);