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 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
14 #include <linux/module.h>
15 #include <linux/slab.h>
16 #include <linux/random.h>
17 #include <linux/skbuff.h>
18 #include <linux/string.h>
20 #include "ieee80211.h"
22 #include <linux/crypto.h>
23 #include <linux/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 {
32 #define WEP_KEY_LEN 13
33 u8 key[WEP_KEY_LEN + 1];
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);
47 priv->key_idx = keyidx;
48 priv->tx_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0, CRYPTO_ALG_ASYNC);
49 if (IS_ERR(priv->tx_tfm)) {
50 pr_debug("could not allocate crypto API arc4\n");
54 priv->rx_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0, CRYPTO_ALG_ASYNC);
55 if (IS_ERR(priv->rx_tfm)) {
56 pr_debug("could not allocate crypto API arc4\n");
61 /* start WEP IV from a random value */
62 get_random_bytes(&priv->iv, 4);
69 crypto_free_blkcipher(priv->tx_tfm);
71 crypto_free_blkcipher(priv->rx_tfm);
78 static void prism2_wep_deinit(void *priv)
80 struct prism2_wep_data *_priv = priv;
84 crypto_free_blkcipher(_priv->tx_tfm);
86 crypto_free_blkcipher(_priv->rx_tfm);
92 /* Perform WEP encryption on given skb that has at least 4 bytes of headroom
93 * for IV and 4 bytes of tailroom for ICV. Both IV and ICV will be transmitted,
94 * so the payload length increases with 8 bytes.
96 * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data))
98 static int prism2_wep_encrypt(struct sk_buff *skb, int hdr_len, void *priv)
100 struct prism2_wep_data *wep = priv;
101 struct blkcipher_desc desc = { .tfm = wep->tx_tfm };
103 u8 key[WEP_KEY_LEN + 3];
107 struct scatterlist sg;
109 if (skb_headroom(skb) < 4 || skb_tailroom(skb) < 4 ||
113 len = skb->len - hdr_len;
114 pos = skb_push(skb, 4);
115 memmove(pos, pos + 4, hdr_len);
118 klen = 3 + wep->key_len;
122 /* Fluhrer, Mantin, and Shamir have reported weaknesses in the key
123 * scheduling algorithm of RC4. At least IVs (KeyByte + 3, 0xff, N)
124 * can be used to speedup attacks, so avoid using them. */
125 if ((wep->iv & 0xff00) == 0xff00) {
126 u8 B = (wep->iv >> 16) & 0xff;
127 if (B >= 3 && B < klen)
131 /* Prepend 24-bit IV to RC4 key and TX frame */
132 *pos++ = key[0] = (wep->iv >> 16) & 0xff;
133 *pos++ = key[1] = (wep->iv >> 8) & 0xff;
134 *pos++ = key[2] = wep->iv & 0xff;
135 *pos++ = wep->key_idx << 6;
137 /* Copy rest of the WEP key (the secret part) */
138 memcpy(key + 3, wep->key, wep->key_len);
140 /* Append little-endian CRC32 and encrypt it to produce ICV */
141 crc = ~crc32_le(~0, pos, len);
142 icv = skb_put(skb, 4);
148 crypto_blkcipher_setkey(wep->tx_tfm, key, klen);
149 sg_init_one(&sg, pos, len + 4);
151 return crypto_blkcipher_encrypt(&desc, &sg, &sg, len + 4);
154 /* Perform WEP decryption on given buffer. Buffer includes whole WEP part of
155 * the frame: IV (4 bytes), encrypted payload (including SNAP header),
156 * ICV (4 bytes). len includes both IV and ICV.
158 * Returns 0 if frame was decrypted successfully and ICV was correct and -1 on
159 * failure. If frame is OK, IV and ICV will be removed.
161 static int prism2_wep_decrypt(struct sk_buff *skb, int hdr_len, void *priv)
163 struct prism2_wep_data *wep = priv;
164 struct blkcipher_desc desc = { .tfm = wep->rx_tfm };
166 u8 key[WEP_KEY_LEN + 3];
170 struct scatterlist sg;
172 if (skb->len < hdr_len + 8)
175 pos = skb->data + hdr_len;
179 keyidx = *pos++ >> 6;
180 if (keyidx != wep->key_idx)
183 klen = 3 + wep->key_len;
185 /* Copy rest of the WEP key (the secret part) */
186 memcpy(key + 3, wep->key, wep->key_len);
188 /* Apply RC4 to data and compute CRC32 over decrypted data */
189 plen = skb->len - hdr_len - 8;
191 crypto_blkcipher_setkey(wep->rx_tfm, key, klen);
192 sg_init_one(&sg, pos, plen + 4);
194 if (crypto_blkcipher_decrypt(&desc, &sg, &sg, plen + 4))
197 crc = ~crc32_le(~0, pos, plen);
203 if (memcmp(icv, pos + plen, 4) != 0) {
204 /* ICV mismatch - drop frame */
208 /* Remove IV and ICV */
209 memmove(skb->data + 4, skb->data, hdr_len);
211 skb_trim(skb, skb->len - 4);
215 static int prism2_wep_set_key(void *key, int len, u8 *seq, void *priv)
217 struct prism2_wep_data *wep = priv;
219 if (len < 0 || len > WEP_KEY_LEN)
222 memcpy(wep->key, key, len);
228 static int prism2_wep_get_key(void *key, int len, u8 *seq, void *priv)
230 struct prism2_wep_data *wep = priv;
232 if (len < wep->key_len)
235 memcpy(key, wep->key, wep->key_len);
240 static char *prism2_wep_print_stats(char *p, void *priv)
242 struct prism2_wep_data *wep = priv;
243 p += sprintf(p, "key[%d] alg=WEP len=%d\n",
244 wep->key_idx, wep->key_len);
248 static struct ieee80211_crypto_ops ieee80211_crypt_wep = {
250 .init = prism2_wep_init,
251 .deinit = prism2_wep_deinit,
252 .encrypt_mpdu = prism2_wep_encrypt,
253 .decrypt_mpdu = prism2_wep_decrypt,
254 .encrypt_msdu = NULL,
255 .decrypt_msdu = NULL,
256 .set_key = prism2_wep_set_key,
257 .get_key = prism2_wep_get_key,
258 .print_stats = prism2_wep_print_stats,
259 .extra_prefix_len = 4, /* IV */
260 .extra_postfix_len = 4, /* ICV */
261 .owner = THIS_MODULE,
264 int ieee80211_crypto_wep_init(void)
266 return ieee80211_register_crypto_ops(&ieee80211_crypt_wep);
269 void ieee80211_crypto_wep_exit(void)
271 ieee80211_unregister_crypto_ops(&ieee80211_crypt_wep);
274 void ieee80211_wep_null(void)