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
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>
21 #include <net/ieee80211.h>
23 #include <linux/crypto.h>
24 #include <asm/scatterlist.h>
25 #include <linux/crc32.h>
27 MODULE_AUTHOR("Jouni Malinen");
28 MODULE_DESCRIPTION("Host AP crypt: WEP");
29 MODULE_LICENSE("GPL");
31 struct prism2_wep_data {
33 #define WEP_KEY_LEN 13
34 u8 key[WEP_KEY_LEN + 1];
37 struct crypto_tfm *tfm;
40 static void *prism2_wep_init(struct ieee80211_device *ieee, int keyidx)
42 struct prism2_wep_data *priv;
44 priv = kmalloc(sizeof(*priv), GFP_ATOMIC);
47 memset(priv, 0, sizeof(*priv));
48 priv->key_idx = keyidx;
50 priv->tfm = crypto_alloc_tfm("arc4", 0);
51 if (priv->tfm == NULL) {
52 printk(KERN_DEBUG "ieee80211_crypt_wep: could not allocate "
57 /* start WEP IV from a random value */
58 get_random_bytes(&priv->iv, 4);
65 crypto_free_tfm(priv->tfm);
71 static void prism2_wep_deinit(void *priv)
73 struct prism2_wep_data *_priv = priv;
74 if (_priv && _priv->tfm)
75 crypto_free_tfm(_priv->tfm);
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.
83 * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data))
85 static int prism2_wep_encrypt(struct sk_buff *skb, int hdr_len, void *priv)
87 struct prism2_wep_data *wep = priv;
89 u8 key[WEP_KEY_LEN + 3];
91 struct scatterlist sg;
93 if (skb_headroom(skb) < 4 || skb_tailroom(skb) < 4 ||
97 len = skb->len - hdr_len;
98 pos = skb_push(skb, 4);
99 memmove(pos, pos + 4, hdr_len);
102 klen = 3 + wep->key_len;
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)
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;
121 /* Copy rest of the WEP key (the secret part) */
122 memcpy(key + 3, wep->key, wep->key_len);
124 /* Append little-endian CRC32 and encrypt it to produce ICV */
125 crc = ~crc32_le(~0, pos, len);
126 icv = skb_put(skb, 4);
132 crypto_cipher_setkey(wep->tfm, key, klen);
133 sg.page = virt_to_page(pos);
134 sg.offset = offset_in_page(pos);
136 crypto_cipher_encrypt(wep->tfm, &sg, &sg, len + 4);
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.
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.
148 static int prism2_wep_decrypt(struct sk_buff *skb, int hdr_len, void *priv)
150 struct prism2_wep_data *wep = priv;
152 u8 key[WEP_KEY_LEN + 3];
153 u8 keyidx, *pos, icv[4];
154 struct scatterlist sg;
156 if (skb->len < hdr_len + 8)
159 pos = skb->data + hdr_len;
163 keyidx = *pos++ >> 6;
164 if (keyidx != wep->key_idx)
167 klen = 3 + wep->key_len;
169 /* Copy rest of the WEP key (the secret part) */
170 memcpy(key + 3, wep->key, wep->key_len);
172 /* Apply RC4 to data and compute CRC32 over decrypted data */
173 plen = skb->len - hdr_len - 8;
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);
181 crc = ~crc32_le(~0, pos, plen);
186 if (memcmp(icv, pos + plen, 4) != 0) {
187 /* ICV mismatch - drop frame */
191 /* Remove IV and ICV */
192 memmove(skb->data + 4, skb->data, hdr_len);
194 skb_trim(skb, skb->len - 4);
199 static int prism2_wep_set_key(void *key, int len, u8 * seq, void *priv)
201 struct prism2_wep_data *wep = priv;
203 if (len < 0 || len > WEP_KEY_LEN)
206 memcpy(wep->key, key, len);
212 static int prism2_wep_get_key(void *key, int len, u8 * seq, void *priv)
214 struct prism2_wep_data *wep = priv;
216 if (len < wep->key_len)
219 memcpy(key, wep->key, wep->key_len);
224 static char *prism2_wep_print_stats(char *p, void *priv)
226 struct prism2_wep_data *wep = priv;
227 p += sprintf(p, "key[%d] alg=WEP len=%d\n", wep->key_idx, wep->key_len);
231 static struct ieee80211_crypto_ops ieee80211_crypt_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,
242 .extra_prefix_len = 4, /* IV */
243 .extra_postfix_len = 4, /* ICV */
244 .owner = THIS_MODULE,
247 static int __init ieee80211_crypto_wep_init(void)
249 return ieee80211_register_crypto_ops(&ieee80211_crypt_wep);
252 static void __exit ieee80211_crypto_wep_exit(void)
254 ieee80211_unregister_crypto_ops(&ieee80211_crypt_wep);
257 module_init(ieee80211_crypto_wep_init);
258 module_exit(ieee80211_crypto_wep_exit);