2 * Software WEP encryption implementation
3 * Copyright 2002, Jouni Malinen <jkmaline@cc.hut.fi>
4 * Copyright 2003, Instant802 Networks, Inc.
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.
11 #include <linux/netdevice.h>
12 #include <linux/types.h>
13 #include <linux/random.h>
14 #include <linux/compiler.h>
15 #include <linux/crc32.h>
16 #include <linux/crypto.h>
17 #include <linux/err.h>
19 #include <linux/scatterlist.h>
21 #include <net/mac80211.h>
22 #include "ieee80211_i.h"
26 int ieee80211_wep_init(struct ieee80211_local *local)
28 /* start WEP IV from a random value */
29 get_random_bytes(&local->wep_iv, WEP_IV_LEN);
31 local->wep_tx_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0,
33 if (IS_ERR(local->wep_tx_tfm))
34 return PTR_ERR(local->wep_tx_tfm);
36 local->wep_rx_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0,
38 if (IS_ERR(local->wep_rx_tfm)) {
39 crypto_free_blkcipher(local->wep_tx_tfm);
40 return PTR_ERR(local->wep_rx_tfm);
46 void ieee80211_wep_free(struct ieee80211_local *local)
48 crypto_free_blkcipher(local->wep_tx_tfm);
49 crypto_free_blkcipher(local->wep_rx_tfm);
52 static inline bool ieee80211_wep_weak_iv(u32 iv, int keylen)
55 * Fluhrer, Mantin, and Shamir have reported weaknesses in the
56 * key scheduling algorithm of RC4. At least IVs (KeyByte + 3,
57 * 0xff, N) can be used to speedup attacks, so avoid using them.
59 if ((iv & 0xff00) == 0xff00) {
60 u8 B = (iv >> 16) & 0xff;
61 if (B >= 3 && B < 3 + keylen)
68 static void ieee80211_wep_get_iv(struct ieee80211_local *local,
69 struct ieee80211_key *key, u8 *iv)
72 if (ieee80211_wep_weak_iv(local->wep_iv, key->conf.keylen))
73 local->wep_iv += 0x0100;
78 *iv++ = (local->wep_iv >> 16) & 0xff;
79 *iv++ = (local->wep_iv >> 8) & 0xff;
80 *iv++ = local->wep_iv & 0xff;
81 *iv++ = key->conf.keyidx << 6;
85 static u8 *ieee80211_wep_add_iv(struct ieee80211_local *local,
87 struct ieee80211_key *key)
89 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
93 hdr->frame_control |= cpu_to_le16(IEEE80211_FCTL_PROTECTED);
95 if (WARN_ON(skb_tailroom(skb) < WEP_ICV_LEN ||
96 skb_headroom(skb) < WEP_IV_LEN))
99 hdrlen = ieee80211_hdrlen(hdr->frame_control);
100 newhdr = skb_push(skb, WEP_IV_LEN);
101 memmove(newhdr, newhdr + WEP_IV_LEN, hdrlen);
102 ieee80211_wep_get_iv(local, key, newhdr + hdrlen);
103 return newhdr + hdrlen;
107 static void ieee80211_wep_remove_iv(struct ieee80211_local *local,
109 struct ieee80211_key *key)
111 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
114 hdrlen = ieee80211_hdrlen(hdr->frame_control);
115 memmove(skb->data + WEP_IV_LEN, skb->data, hdrlen);
116 skb_pull(skb, WEP_IV_LEN);
120 /* Perform WEP encryption using given key. data buffer must have tailroom
121 * for 4-byte ICV. data_len must not include this ICV. Note: this function
122 * does _not_ add IV. data = RC4(data | CRC32(data)) */
123 void ieee80211_wep_encrypt_data(struct crypto_blkcipher *tfm, u8 *rc4key,
124 size_t klen, u8 *data, size_t data_len)
126 struct blkcipher_desc desc = { .tfm = tfm };
127 struct scatterlist sg;
130 icv = (__le32 *)(data + data_len);
131 *icv = cpu_to_le32(~crc32_le(~0, data, data_len));
133 crypto_blkcipher_setkey(tfm, rc4key, klen);
134 sg_init_one(&sg, data, data_len + WEP_ICV_LEN);
135 crypto_blkcipher_encrypt(&desc, &sg, &sg, sg.length);
139 /* Perform WEP encryption on given skb. 4 bytes of extra space (IV) in the
140 * beginning of the buffer 4 bytes of extra space (ICV) in the end of the
141 * buffer will be added. Both IV and ICV will be transmitted, so the
142 * payload length increases with 8 bytes.
144 * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data))
146 int ieee80211_wep_encrypt(struct ieee80211_local *local, struct sk_buff *skb,
147 struct ieee80211_key *key)
153 if (!key || key->conf.alg != ALG_WEP)
156 klen = 3 + key->conf.keylen;
157 rc4key = kmalloc(klen, GFP_ATOMIC);
161 iv = ieee80211_wep_add_iv(local, skb, key);
167 len = skb->len - (iv + WEP_IV_LEN - skb->data);
169 /* Prepend 24-bit IV to RC4 key */
170 memcpy(rc4key, iv, 3);
172 /* Copy rest of the WEP key (the secret part) */
173 memcpy(rc4key + 3, key->conf.key, key->conf.keylen);
175 /* Add room for ICV */
176 skb_put(skb, WEP_ICV_LEN);
178 ieee80211_wep_encrypt_data(local->wep_tx_tfm, rc4key, klen,
179 iv + WEP_IV_LEN, len);
187 /* Perform WEP decryption using given key. data buffer includes encrypted
188 * payload, including 4-byte ICV, but _not_ IV. data_len must not include ICV.
189 * Return 0 on success and -1 on ICV mismatch. */
190 int ieee80211_wep_decrypt_data(struct crypto_blkcipher *tfm, u8 *rc4key,
191 size_t klen, u8 *data, size_t data_len)
193 struct blkcipher_desc desc = { .tfm = tfm };
194 struct scatterlist sg;
197 crypto_blkcipher_setkey(tfm, rc4key, klen);
198 sg_init_one(&sg, data, data_len + WEP_ICV_LEN);
199 crypto_blkcipher_decrypt(&desc, &sg, &sg, sg.length);
201 crc = cpu_to_le32(~crc32_le(~0, data, data_len));
202 if (memcmp(&crc, data + data_len, WEP_ICV_LEN) != 0)
210 /* Perform WEP decryption on given skb. Buffer includes whole WEP part of
211 * the frame: IV (4 bytes), encrypted payload (including SNAP header),
212 * ICV (4 bytes). skb->len includes both IV and ICV.
214 * Returns 0 if frame was decrypted successfully and ICV was correct and -1 on
215 * failure. If frame is OK, IV and ICV will be removed, i.e., decrypted payload
216 * is moved to the beginning of the skb and skb length will be reduced.
218 int ieee80211_wep_decrypt(struct ieee80211_local *local, struct sk_buff *skb,
219 struct ieee80211_key *key)
224 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
229 if (!ieee80211_has_protected(hdr->frame_control))
232 hdrlen = ieee80211_hdrlen(hdr->frame_control);
233 if (skb->len < hdrlen + WEP_IV_LEN + WEP_ICV_LEN)
236 len = skb->len - hdrlen - WEP_IV_LEN - WEP_ICV_LEN;
238 keyidx = skb->data[hdrlen + 3] >> 6;
240 if (!key || keyidx != key->conf.keyidx || key->conf.alg != ALG_WEP)
243 klen = 3 + key->conf.keylen;
245 rc4key = kmalloc(klen, GFP_ATOMIC);
249 /* Prepend 24-bit IV to RC4 key */
250 memcpy(rc4key, skb->data + hdrlen, 3);
252 /* Copy rest of the WEP key (the secret part) */
253 memcpy(rc4key + 3, key->conf.key, key->conf.keylen);
255 if (ieee80211_wep_decrypt_data(local->wep_rx_tfm, rc4key, klen,
256 skb->data + hdrlen + WEP_IV_LEN,
263 skb_trim(skb, skb->len - WEP_ICV_LEN);
266 memmove(skb->data + WEP_IV_LEN, skb->data, hdrlen);
267 skb_pull(skb, WEP_IV_LEN);
273 bool ieee80211_wep_is_weak_iv(struct sk_buff *skb, struct ieee80211_key *key)
275 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
280 if (!ieee80211_has_protected(hdr->frame_control))
283 hdrlen = ieee80211_hdrlen(hdr->frame_control);
284 ivpos = skb->data + hdrlen;
285 iv = (ivpos[0] << 16) | (ivpos[1] << 8) | ivpos[2];
287 return ieee80211_wep_weak_iv(iv, key->conf.keylen);
291 ieee80211_crypto_wep_decrypt(struct ieee80211_rx_data *rx)
293 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)rx->skb->data;
295 if (!ieee80211_is_data(hdr->frame_control) &&
296 !ieee80211_is_auth(hdr->frame_control))
299 if (!(rx->status->flag & RX_FLAG_DECRYPTED)) {
300 if (ieee80211_wep_decrypt(rx->local, rx->skb, rx->key))
301 return RX_DROP_UNUSABLE;
302 } else if (!(rx->status->flag & RX_FLAG_IV_STRIPPED)) {
303 ieee80211_wep_remove_iv(rx->local, rx->skb, rx->key);
305 skb_trim(rx->skb, rx->skb->len - WEP_ICV_LEN);
311 static int wep_encrypt_skb(struct ieee80211_tx_data *tx, struct sk_buff *skb)
313 struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
315 if (!(tx->key->flags & KEY_FLAG_UPLOADED_TO_HARDWARE)) {
316 if (ieee80211_wep_encrypt(tx->local, skb, tx->key))
319 info->control.hw_key = &tx->key->conf;
320 if (tx->key->conf.flags & IEEE80211_KEY_FLAG_GENERATE_IV) {
321 if (!ieee80211_wep_add_iv(tx->local, skb, tx->key))
329 ieee80211_crypto_wep_encrypt(struct ieee80211_tx_data *tx)
333 ieee80211_tx_set_protected(tx);
335 if (wep_encrypt_skb(tx, tx->skb) < 0) {
336 I802_DEBUG_INC(tx->local->tx_handlers_drop_wep);
340 if (tx->extra_frag) {
341 for (i = 0; i < tx->num_extra_frag; i++) {
342 if (wep_encrypt_skb(tx, tx->extra_frag[i])) {
343 I802_DEBUG_INC(tx->local->
344 tx_handlers_drop_wep);