tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
1/*
2 * lib80211 crypt: host-based WEP encryption implementation for lib80211
3 *
4 * Copyright (c) 2002-2004, Jouni Malinen <j@w1.fi>
5 * Copyright (c) 2008, John W. Linville <linville@tuxdriver.com>
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
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>
22
23#include <net/lib80211.h>
24
25#include <linux/crypto.h>
26#include <linux/crc32.h>
27
28MODULE_AUTHOR("Jouni Malinen");
29MODULE_DESCRIPTION("lib80211 crypt: WEP");
30MODULE_LICENSE("GPL");
31
32struct 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_cipher *tx_tfm;
39 struct crypto_cipher *rx_tfm;
40};
41
42static void *lib80211_wep_init(int keyidx)
43{
44 struct lib80211_wep_data *priv;
45
46 priv = kzalloc(sizeof(*priv), GFP_ATOMIC);
47 if (priv == NULL)
48 goto fail;
49 priv->key_idx = keyidx;
50
51 priv->tx_tfm = crypto_alloc_cipher("arc4", 0, 0);
52 if (IS_ERR(priv->tx_tfm)) {
53 priv->tx_tfm = NULL;
54 goto fail;
55 }
56
57 priv->rx_tfm = crypto_alloc_cipher("arc4", 0, 0);
58 if (IS_ERR(priv->rx_tfm)) {
59 priv->rx_tfm = NULL;
60 goto fail;
61 }
62 /* start WEP IV from a random value */
63 get_random_bytes(&priv->iv, 4);
64
65 return priv;
66
67 fail:
68 if (priv) {
69 crypto_free_cipher(priv->tx_tfm);
70 crypto_free_cipher(priv->rx_tfm);
71 kfree(priv);
72 }
73 return NULL;
74}
75
76static void lib80211_wep_deinit(void *priv)
77{
78 struct lib80211_wep_data *_priv = priv;
79 if (_priv) {
80 crypto_free_cipher(_priv->tx_tfm);
81 crypto_free_cipher(_priv->rx_tfm);
82 }
83 kfree(priv);
84}
85
86/* Add WEP IV/key info to a frame that has at least 4 bytes of headroom */
87static int lib80211_wep_build_iv(struct sk_buff *skb, int hdr_len,
88 u8 *key, int keylen, void *priv)
89{
90 struct lib80211_wep_data *wep = priv;
91 u32 klen;
92 u8 *pos;
93
94 if (skb_headroom(skb) < 4 || skb->len < hdr_len)
95 return -1;
96
97 pos = skb_push(skb, 4);
98 memmove(pos, pos + 4, hdr_len);
99 pos += hdr_len;
100
101 klen = 3 + wep->key_len;
102
103 wep->iv++;
104
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;
112 }
113
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;
119
120 return 0;
121}
122
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.
126 *
127 * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data))
128 */
129static int lib80211_wep_encrypt(struct sk_buff *skb, int hdr_len, void *priv)
130{
131 struct lib80211_wep_data *wep = priv;
132 u32 crc, klen, len;
133 u8 *pos, *icv;
134 u8 key[WEP_KEY_LEN + 3];
135 int i;
136
137 /* other checks are in lib80211_wep_build_iv */
138 if (skb_tailroom(skb) < 4)
139 return -1;
140
141 /* add the IV to the frame */
142 if (lib80211_wep_build_iv(skb, hdr_len, NULL, 0, priv))
143 return -1;
144
145 /* Copy the IV into the first 3 bytes of the key */
146 skb_copy_from_linear_data_offset(skb, hdr_len, key, 3);
147
148 /* Copy rest of the WEP key (the secret part) */
149 memcpy(key + 3, wep->key, wep->key_len);
150
151 len = skb->len - hdr_len - 4;
152 pos = skb->data + hdr_len + 4;
153 klen = 3 + wep->key_len;
154
155 /* Append little-endian CRC32 over only the data and encrypt it to produce ICV */
156 crc = ~crc32_le(~0, pos, len);
157 icv = skb_put(skb, 4);
158 icv[0] = crc;
159 icv[1] = crc >> 8;
160 icv[2] = crc >> 16;
161 icv[3] = crc >> 24;
162
163 crypto_cipher_setkey(wep->tx_tfm, key, klen);
164
165 for (i = 0; i < len + 4; i++)
166 crypto_cipher_encrypt_one(wep->tx_tfm, pos + i, pos + i);
167
168 return 0;
169}
170
171/* Perform WEP decryption on given buffer. Buffer includes whole WEP part of
172 * the frame: IV (4 bytes), encrypted payload (including SNAP header),
173 * ICV (4 bytes). len includes both IV and ICV.
174 *
175 * Returns 0 if frame was decrypted successfully and ICV was correct and -1 on
176 * failure. If frame is OK, IV and ICV will be removed.
177 */
178static int lib80211_wep_decrypt(struct sk_buff *skb, int hdr_len, void *priv)
179{
180 struct lib80211_wep_data *wep = priv;
181 u32 crc, klen, plen;
182 u8 key[WEP_KEY_LEN + 3];
183 u8 keyidx, *pos, icv[4];
184 int i;
185
186 if (skb->len < hdr_len + 8)
187 return -1;
188
189 pos = skb->data + hdr_len;
190 key[0] = *pos++;
191 key[1] = *pos++;
192 key[2] = *pos++;
193 keyidx = *pos++ >> 6;
194 if (keyidx != wep->key_idx)
195 return -1;
196
197 klen = 3 + wep->key_len;
198
199 /* Copy rest of the WEP key (the secret part) */
200 memcpy(key + 3, wep->key, wep->key_len);
201
202 /* Apply RC4 to data and compute CRC32 over decrypted data */
203 plen = skb->len - hdr_len - 8;
204
205 crypto_cipher_setkey(wep->rx_tfm, key, klen);
206 for (i = 0; i < plen + 4; i++)
207 crypto_cipher_decrypt_one(wep->rx_tfm, pos + i, pos + i);
208
209 crc = ~crc32_le(~0, pos, plen);
210 icv[0] = crc;
211 icv[1] = crc >> 8;
212 icv[2] = crc >> 16;
213 icv[3] = crc >> 24;
214 if (memcmp(icv, pos + plen, 4) != 0) {
215 /* ICV mismatch - drop frame */
216 return -2;
217 }
218
219 /* Remove IV and ICV */
220 memmove(skb->data + 4, skb->data, hdr_len);
221 skb_pull(skb, 4);
222 skb_trim(skb, skb->len - 4);
223
224 return 0;
225}
226
227static int lib80211_wep_set_key(void *key, int len, u8 * seq, void *priv)
228{
229 struct lib80211_wep_data *wep = priv;
230
231 if (len < 0 || len > WEP_KEY_LEN)
232 return -1;
233
234 memcpy(wep->key, key, len);
235 wep->key_len = len;
236
237 return 0;
238}
239
240static int lib80211_wep_get_key(void *key, int len, u8 * seq, void *priv)
241{
242 struct lib80211_wep_data *wep = priv;
243
244 if (len < wep->key_len)
245 return -1;
246
247 memcpy(key, wep->key, wep->key_len);
248
249 return wep->key_len;
250}
251
252static void lib80211_wep_print_stats(struct seq_file *m, void *priv)
253{
254 struct lib80211_wep_data *wep = priv;
255 seq_printf(m, "key[%d] alg=WEP len=%d\n", wep->key_idx, wep->key_len);
256}
257
258static struct lib80211_crypto_ops lib80211_crypt_wep = {
259 .name = "WEP",
260 .init = lib80211_wep_init,
261 .deinit = lib80211_wep_deinit,
262 .encrypt_mpdu = lib80211_wep_encrypt,
263 .decrypt_mpdu = lib80211_wep_decrypt,
264 .encrypt_msdu = NULL,
265 .decrypt_msdu = NULL,
266 .set_key = lib80211_wep_set_key,
267 .get_key = lib80211_wep_get_key,
268 .print_stats = lib80211_wep_print_stats,
269 .extra_mpdu_prefix_len = 4, /* IV */
270 .extra_mpdu_postfix_len = 4, /* ICV */
271 .owner = THIS_MODULE,
272};
273
274static int __init lib80211_crypto_wep_init(void)
275{
276 return lib80211_register_crypto_ops(&lib80211_crypt_wep);
277}
278
279static void __exit lib80211_crypto_wep_exit(void)
280{
281 lib80211_unregister_crypto_ops(&lib80211_crypt_wep);
282}
283
284module_init(lib80211_crypto_wep_init);
285module_exit(lib80211_crypto_wep_exit);