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 <crypto/skcipher.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 <linux/string.h>
21 #include <linux/scatterlist.h>
22 #include <linux/crc32.h>
24 struct prism2_wep_data {
26 #define WEP_KEY_LEN 13
27 u8 key[WEP_KEY_LEN + 1];
30 struct crypto_skcipher *tx_tfm;
31 struct crypto_skcipher *rx_tfm;
35 static void *prism2_wep_init(int keyidx)
37 struct prism2_wep_data *priv;
39 priv = kzalloc(sizeof(*priv), GFP_ATOMIC);
42 priv->key_idx = keyidx;
44 priv->tx_tfm = crypto_alloc_skcipher("ecb(arc4)", 0, CRYPTO_ALG_ASYNC);
45 if (IS_ERR(priv->tx_tfm)) {
46 pr_debug("rtllib_crypt_wep: could not allocate crypto API arc4\n");
50 priv->rx_tfm = crypto_alloc_skcipher("ecb(arc4)", 0, CRYPTO_ALG_ASYNC);
51 if (IS_ERR(priv->rx_tfm)) {
52 pr_debug("rtllib_crypt_wep: could not allocate crypto API arc4\n");
57 /* start WEP IV from a random value */
58 get_random_bytes(&priv->iv, 4);
64 crypto_free_skcipher(priv->tx_tfm);
65 crypto_free_skcipher(priv->rx_tfm);
72 static void prism2_wep_deinit(void *priv)
74 struct prism2_wep_data *_priv = priv;
77 crypto_free_skcipher(_priv->tx_tfm);
78 crypto_free_skcipher(_priv->rx_tfm);
83 /* Perform WEP encryption on given skb that has at least 4 bytes of headroom
84 * for IV and 4 bytes of tailroom for ICV. Both IV and ICV will be transmitted,
85 * so the payload length increases with 8 bytes.
87 * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data))
89 static int prism2_wep_encrypt(struct sk_buff *skb, int hdr_len, void *priv)
91 struct prism2_wep_data *wep = priv;
93 u8 key[WEP_KEY_LEN + 3];
95 struct cb_desc *tcb_desc = (struct cb_desc *)(skb->cb +
99 struct scatterlist sg;
102 if (skb_headroom(skb) < 4 || skb_tailroom(skb) < 4 ||
104 pr_err("Error!!! headroom=%d tailroom=%d skblen=%d hdr_len=%d\n",
105 skb_headroom(skb), skb_tailroom(skb), skb->len, hdr_len);
108 len = skb->len - hdr_len;
109 pos = skb_push(skb, 4);
110 memmove(pos, pos + 4, hdr_len);
113 klen = 3 + wep->key_len;
117 /* Fluhrer, Mantin, and Shamir have reported weaknesses in the key
118 * scheduling algorithm of RC4. At least IVs (KeyByte + 3, 0xff, N)
119 * can be used to speedup attacks, so avoid using them.
121 if ((wep->iv & 0xff00) == 0xff00) {
122 u8 B = (wep->iv >> 16) & 0xff;
124 if (B >= 3 && B < klen)
128 /* Prepend 24-bit IV to RC4 key and TX frame */
129 *pos++ = key[0] = (wep->iv >> 16) & 0xff;
130 *pos++ = key[1] = (wep->iv >> 8) & 0xff;
131 *pos++ = key[2] = wep->iv & 0xff;
132 *pos++ = wep->key_idx << 6;
134 /* Copy rest of the WEP key (the secret part) */
135 memcpy(key + 3, wep->key, wep->key_len);
137 if (!tcb_desc->bHwSec) {
138 SKCIPHER_REQUEST_ON_STACK(req, wep->tx_tfm);
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 sg_init_one(&sg, pos, len+4);
149 crypto_skcipher_setkey(wep->tx_tfm, key, klen);
150 skcipher_request_set_tfm(req, wep->tx_tfm);
151 skcipher_request_set_callback(req, 0, NULL, NULL);
152 skcipher_request_set_crypt(req, &sg, &sg, len + 4, NULL);
153 err = crypto_skcipher_encrypt(req);
154 skcipher_request_zero(req);
162 /* Perform WEP decryption on given struct buffer. Buffer includes whole WEP
163 * part of the frame: IV (4 bytes), encrypted payload (including SNAP header),
164 * ICV (4 bytes). len includes both IV and ICV.
166 * Returns 0 if frame was decrypted successfully and ICV was correct and -1 on
167 * failure. If frame is OK, IV and ICV will be removed.
169 static int prism2_wep_decrypt(struct sk_buff *skb, int hdr_len, void *priv)
171 struct prism2_wep_data *wep = priv;
173 u8 key[WEP_KEY_LEN + 3];
175 struct cb_desc *tcb_desc = (struct cb_desc *)(skb->cb +
179 struct scatterlist sg;
182 if (skb->len < hdr_len + 8)
185 pos = skb->data + hdr_len;
189 keyidx = *pos++ >> 6;
190 if (keyidx != wep->key_idx)
193 klen = 3 + wep->key_len;
195 /* Copy rest of the WEP key (the secret part) */
196 memcpy(key + 3, wep->key, wep->key_len);
198 /* Apply RC4 to data and compute CRC32 over decrypted data */
199 plen = skb->len - hdr_len - 8;
201 if (!tcb_desc->bHwSec) {
202 SKCIPHER_REQUEST_ON_STACK(req, wep->rx_tfm);
204 sg_init_one(&sg, pos, plen+4);
205 crypto_skcipher_setkey(wep->rx_tfm, key, klen);
206 skcipher_request_set_tfm(req, wep->rx_tfm);
207 skcipher_request_set_callback(req, 0, NULL, NULL);
208 skcipher_request_set_crypt(req, &sg, &sg, plen + 4, NULL);
209 err = crypto_skcipher_decrypt(req);
210 skcipher_request_zero(req);
213 crc = ~crc32_le(~0, pos, plen);
218 if (memcmp(icv, pos + plen, 4) != 0) {
219 /* ICV mismatch - drop frame */
223 /* Remove IV and ICV */
224 memmove(skb->data + 4, skb->data, hdr_len);
226 skb_trim(skb, skb->len - 4);
232 static int prism2_wep_set_key(void *key, int len, u8 *seq, void *priv)
234 struct prism2_wep_data *wep = priv;
236 if (len < 0 || len > WEP_KEY_LEN)
239 memcpy(wep->key, key, len);
246 static int prism2_wep_get_key(void *key, int len, u8 *seq, void *priv)
248 struct prism2_wep_data *wep = priv;
250 if (len < wep->key_len)
253 memcpy(key, wep->key, wep->key_len);
259 static void prism2_wep_print_stats(struct seq_file *m, void *priv)
261 struct prism2_wep_data *wep = priv;
263 seq_printf(m, "key[%d] alg=WEP len=%d\n", wep->key_idx, wep->key_len);
266 static struct lib80211_crypto_ops rtllib_crypt_wep = {
268 .init = prism2_wep_init,
269 .deinit = prism2_wep_deinit,
270 .encrypt_mpdu = prism2_wep_encrypt,
271 .decrypt_mpdu = prism2_wep_decrypt,
272 .encrypt_msdu = NULL,
273 .decrypt_msdu = NULL,
274 .set_key = prism2_wep_set_key,
275 .get_key = prism2_wep_get_key,
276 .print_stats = prism2_wep_print_stats,
277 .extra_mpdu_prefix_len = 4, /* IV */
278 .extra_mpdu_postfix_len = 4, /* ICV */
279 .owner = THIS_MODULE,
283 static int __init rtllib_crypto_wep_init(void)
285 return lib80211_register_crypto_ops(&rtllib_crypt_wep);
289 static void __exit rtllib_crypto_wep_exit(void)
291 lib80211_unregister_crypto_ops(&rtllib_crypt_wep);
294 module_init(rtllib_crypto_wep_init);
295 module_exit(rtllib_crypto_wep_exit);
297 MODULE_LICENSE("GPL");