Merge tag 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost
[cris-mirror.git] / net / wireless / lib80211_crypt_wep.c
blobd05f58b0fd04f5f15a0d1acccaae44d2de7411df
1 /*
2 * lib80211 crypt: host-based WEP encryption implementation for lib80211
4 * Copyright (c) 2002-2004, Jouni Malinen <j@w1.fi>
5 * Copyright (c) 2008, John W. Linville <linville@tuxdriver.com>
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.
13 #include <linux/err.h>
14 #include <linux/module.h>
15 #include <linux/init.h>
16 #include <linux/slab.h>
17 #include <linux/random.h>
18 #include <linux/scatterlist.h>
19 #include <linux/skbuff.h>
20 #include <linux/mm.h>
21 #include <asm/string.h>
23 #include <net/lib80211.h>
25 #include <crypto/skcipher.h>
26 #include <linux/crc32.h>
28 MODULE_AUTHOR("Jouni Malinen");
29 MODULE_DESCRIPTION("lib80211 crypt: WEP");
30 MODULE_LICENSE("GPL");
32 struct lib80211_wep_data {
33 u32 iv;
34 #define WEP_KEY_LEN 13
35 u8 key[WEP_KEY_LEN + 1];
36 u8 key_len;
37 u8 key_idx;
38 struct crypto_skcipher *tx_tfm;
39 struct crypto_skcipher *rx_tfm;
42 static void *lib80211_wep_init(int keyidx)
44 struct lib80211_wep_data *priv;
46 priv = kzalloc(sizeof(*priv), GFP_ATOMIC);
47 if (priv == NULL)
48 goto fail;
49 priv->key_idx = keyidx;
51 priv->tx_tfm = crypto_alloc_skcipher("ecb(arc4)", 0, CRYPTO_ALG_ASYNC);
52 if (IS_ERR(priv->tx_tfm)) {
53 priv->tx_tfm = NULL;
54 goto fail;
57 priv->rx_tfm = crypto_alloc_skcipher("ecb(arc4)", 0, CRYPTO_ALG_ASYNC);
58 if (IS_ERR(priv->rx_tfm)) {
59 priv->rx_tfm = NULL;
60 goto fail;
62 /* start WEP IV from a random value */
63 get_random_bytes(&priv->iv, 4);
65 return priv;
67 fail:
68 if (priv) {
69 crypto_free_skcipher(priv->tx_tfm);
70 crypto_free_skcipher(priv->rx_tfm);
71 kfree(priv);
73 return NULL;
76 static void lib80211_wep_deinit(void *priv)
78 struct lib80211_wep_data *_priv = priv;
79 if (_priv) {
80 crypto_free_skcipher(_priv->tx_tfm);
81 crypto_free_skcipher(_priv->rx_tfm);
83 kfree(priv);
86 /* Add WEP IV/key info to a frame that has at least 4 bytes of headroom */
87 static int lib80211_wep_build_iv(struct sk_buff *skb, int hdr_len,
88 u8 *key, int keylen, void *priv)
90 struct lib80211_wep_data *wep = priv;
91 u32 klen;
92 u8 *pos;
94 if (skb_headroom(skb) < 4 || skb->len < hdr_len)
95 return -1;
97 pos = skb_push(skb, 4);
98 memmove(pos, pos + 4, hdr_len);
99 pos += hdr_len;
101 klen = 3 + wep->key_len;
103 wep->iv++;
105 /* Fluhrer, Mantin, and Shamir have reported weaknesses in the key
106 * scheduling algorithm of RC4. At least IVs (KeyByte + 3, 0xff, N)
107 * can be used to speedup attacks, so avoid using them. */
108 if ((wep->iv & 0xff00) == 0xff00) {
109 u8 B = (wep->iv >> 16) & 0xff;
110 if (B >= 3 && B < klen)
111 wep->iv += 0x0100;
114 /* Prepend 24-bit IV to RC4 key and TX frame */
115 *pos++ = (wep->iv >> 16) & 0xff;
116 *pos++ = (wep->iv >> 8) & 0xff;
117 *pos++ = wep->iv & 0xff;
118 *pos++ = wep->key_idx << 6;
120 return 0;
123 /* Perform WEP encryption on given skb that has at least 4 bytes of headroom
124 * for IV and 4 bytes of tailroom for ICV. Both IV and ICV will be transmitted,
125 * so the payload length increases with 8 bytes.
127 * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data))
129 static int lib80211_wep_encrypt(struct sk_buff *skb, int hdr_len, void *priv)
131 struct lib80211_wep_data *wep = priv;
132 SKCIPHER_REQUEST_ON_STACK(req, wep->tx_tfm);
133 u32 crc, klen, len;
134 u8 *pos, *icv;
135 struct scatterlist sg;
136 u8 key[WEP_KEY_LEN + 3];
137 int err;
139 /* other checks are in lib80211_wep_build_iv */
140 if (skb_tailroom(skb) < 4)
141 return -1;
143 /* add the IV to the frame */
144 if (lib80211_wep_build_iv(skb, hdr_len, NULL, 0, priv))
145 return -1;
147 /* Copy the IV into the first 3 bytes of the key */
148 skb_copy_from_linear_data_offset(skb, hdr_len, key, 3);
150 /* Copy rest of the WEP key (the secret part) */
151 memcpy(key + 3, wep->key, wep->key_len);
153 len = skb->len - hdr_len - 4;
154 pos = skb->data + hdr_len + 4;
155 klen = 3 + wep->key_len;
157 /* Append little-endian CRC32 over only the data and encrypt it to produce ICV */
158 crc = ~crc32_le(~0, pos, len);
159 icv = skb_put(skb, 4);
160 icv[0] = crc;
161 icv[1] = crc >> 8;
162 icv[2] = crc >> 16;
163 icv[3] = crc >> 24;
165 crypto_skcipher_setkey(wep->tx_tfm, key, klen);
166 sg_init_one(&sg, pos, len + 4);
167 skcipher_request_set_tfm(req, wep->tx_tfm);
168 skcipher_request_set_callback(req, 0, NULL, NULL);
169 skcipher_request_set_crypt(req, &sg, &sg, len + 4, NULL);
170 err = crypto_skcipher_encrypt(req);
171 skcipher_request_zero(req);
172 return err;
175 /* Perform WEP decryption on given buffer. Buffer includes whole WEP part of
176 * the frame: IV (4 bytes), encrypted payload (including SNAP header),
177 * ICV (4 bytes). len includes both IV and ICV.
179 * Returns 0 if frame was decrypted successfully and ICV was correct and -1 on
180 * failure. If frame is OK, IV and ICV will be removed.
182 static int lib80211_wep_decrypt(struct sk_buff *skb, int hdr_len, void *priv)
184 struct lib80211_wep_data *wep = priv;
185 SKCIPHER_REQUEST_ON_STACK(req, wep->rx_tfm);
186 u32 crc, klen, plen;
187 u8 key[WEP_KEY_LEN + 3];
188 u8 keyidx, *pos, icv[4];
189 struct scatterlist sg;
190 int err;
192 if (skb->len < hdr_len + 8)
193 return -1;
195 pos = skb->data + hdr_len;
196 key[0] = *pos++;
197 key[1] = *pos++;
198 key[2] = *pos++;
199 keyidx = *pos++ >> 6;
200 if (keyidx != wep->key_idx)
201 return -1;
203 klen = 3 + wep->key_len;
205 /* Copy rest of the WEP key (the secret part) */
206 memcpy(key + 3, wep->key, wep->key_len);
208 /* Apply RC4 to data and compute CRC32 over decrypted data */
209 plen = skb->len - hdr_len - 8;
211 crypto_skcipher_setkey(wep->rx_tfm, key, klen);
212 sg_init_one(&sg, pos, plen + 4);
213 skcipher_request_set_tfm(req, wep->rx_tfm);
214 skcipher_request_set_callback(req, 0, NULL, NULL);
215 skcipher_request_set_crypt(req, &sg, &sg, plen + 4, NULL);
216 err = crypto_skcipher_decrypt(req);
217 skcipher_request_zero(req);
218 if (err)
219 return -7;
221 crc = ~crc32_le(~0, pos, plen);
222 icv[0] = crc;
223 icv[1] = crc >> 8;
224 icv[2] = crc >> 16;
225 icv[3] = crc >> 24;
226 if (memcmp(icv, pos + plen, 4) != 0) {
227 /* ICV mismatch - drop frame */
228 return -2;
231 /* Remove IV and ICV */
232 memmove(skb->data + 4, skb->data, hdr_len);
233 skb_pull(skb, 4);
234 skb_trim(skb, skb->len - 4);
236 return 0;
239 static int lib80211_wep_set_key(void *key, int len, u8 * seq, void *priv)
241 struct lib80211_wep_data *wep = priv;
243 if (len < 0 || len > WEP_KEY_LEN)
244 return -1;
246 memcpy(wep->key, key, len);
247 wep->key_len = len;
249 return 0;
252 static int lib80211_wep_get_key(void *key, int len, u8 * seq, void *priv)
254 struct lib80211_wep_data *wep = priv;
256 if (len < wep->key_len)
257 return -1;
259 memcpy(key, wep->key, wep->key_len);
261 return wep->key_len;
264 static void lib80211_wep_print_stats(struct seq_file *m, void *priv)
266 struct lib80211_wep_data *wep = priv;
267 seq_printf(m, "key[%d] alg=WEP len=%d\n", wep->key_idx, wep->key_len);
270 static struct lib80211_crypto_ops lib80211_crypt_wep = {
271 .name = "WEP",
272 .init = lib80211_wep_init,
273 .deinit = lib80211_wep_deinit,
274 .encrypt_mpdu = lib80211_wep_encrypt,
275 .decrypt_mpdu = lib80211_wep_decrypt,
276 .encrypt_msdu = NULL,
277 .decrypt_msdu = NULL,
278 .set_key = lib80211_wep_set_key,
279 .get_key = lib80211_wep_get_key,
280 .print_stats = lib80211_wep_print_stats,
281 .extra_mpdu_prefix_len = 4, /* IV */
282 .extra_mpdu_postfix_len = 4, /* ICV */
283 .owner = THIS_MODULE,
286 static int __init lib80211_crypto_wep_init(void)
288 return lib80211_register_crypto_ops(&lib80211_crypt_wep);
291 static void __exit lib80211_crypto_wep_exit(void)
293 lib80211_unregister_crypto_ops(&lib80211_crypt_wep);
296 module_init(lib80211_crypto_wep_init);
297 module_exit(lib80211_crypto_wep_exit);