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 <asm/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))
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);
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 int ieee80211_wep_weak_iv(u32 iv, int keylen)
54 /* Fluhrer, Mantin, and Shamir have reported weaknesses in the
55 * key scheduling algorithm of RC4. At least IVs (KeyByte + 3,
56 * 0xff, N) can be used to speedup attacks, so avoid using them. */
57 if ((iv & 0xff00) == 0xff00) {
58 u8 B = (iv >> 16) & 0xff;
59 if (B >= 3 && B < 3 + keylen)
66 void ieee80211_wep_get_iv(struct ieee80211_local *local,
67 struct ieee80211_key *key, u8 *iv)
70 if (ieee80211_wep_weak_iv(local->wep_iv, key->keylen))
71 local->wep_iv += 0x0100;
76 *iv++ = (local->wep_iv >> 16) & 0xff;
77 *iv++ = (local->wep_iv >> 8) & 0xff;
78 *iv++ = local->wep_iv & 0xff;
79 *iv++ = key->keyidx << 6;
83 u8 * ieee80211_wep_add_iv(struct ieee80211_local *local,
85 struct ieee80211_key *key)
87 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
92 fc = le16_to_cpu(hdr->frame_control);
93 fc |= IEEE80211_FCTL_PROTECTED;
94 hdr->frame_control = cpu_to_le16(fc);
96 if ((skb_headroom(skb) < WEP_IV_LEN ||
97 skb_tailroom(skb) < WEP_ICV_LEN)) {
98 I802_DEBUG_INC(local->tx_expand_skb_head);
99 if (unlikely(pskb_expand_head(skb, WEP_IV_LEN, WEP_ICV_LEN,
104 hdrlen = ieee80211_get_hdrlen(fc);
105 newhdr = skb_push(skb, WEP_IV_LEN);
106 memmove(newhdr, newhdr + WEP_IV_LEN, hdrlen);
107 ieee80211_wep_get_iv(local, key, newhdr + hdrlen);
108 return newhdr + hdrlen;
112 void ieee80211_wep_remove_iv(struct ieee80211_local *local,
114 struct ieee80211_key *key)
116 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
120 fc = le16_to_cpu(hdr->frame_control);
121 hdrlen = ieee80211_get_hdrlen(fc);
122 memmove(skb->data + WEP_IV_LEN, skb->data, hdrlen);
123 skb_pull(skb, WEP_IV_LEN);
127 /* Perform WEP encryption using given key. data buffer must have tailroom
128 * for 4-byte ICV. data_len must not include this ICV. Note: this function
129 * does _not_ add IV. data = RC4(data | CRC32(data)) */
130 void ieee80211_wep_encrypt_data(struct crypto_blkcipher *tfm, u8 *rc4key,
131 size_t klen, u8 *data, size_t data_len)
133 struct blkcipher_desc desc = { .tfm = tfm };
134 struct scatterlist sg;
137 icv = (__le32 *)(data + data_len);
138 *icv = cpu_to_le32(~crc32_le(~0, data, data_len));
140 crypto_blkcipher_setkey(tfm, rc4key, klen);
141 sg.page = virt_to_page(data);
142 sg.offset = offset_in_page(data);
143 sg.length = data_len + WEP_ICV_LEN;
144 crypto_blkcipher_encrypt(&desc, &sg, &sg, sg.length);
148 /* Perform WEP encryption on given skb. 4 bytes of extra space (IV) in the
149 * beginning of the buffer 4 bytes of extra space (ICV) in the end of the
150 * buffer will be added. Both IV and ICV will be transmitted, so the
151 * payload length increases with 8 bytes.
153 * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data))
155 int ieee80211_wep_encrypt(struct ieee80211_local *local, struct sk_buff *skb,
156 struct ieee80211_key *key)
162 if (!key || key->alg != ALG_WEP)
165 klen = 3 + key->keylen;
166 rc4key = kmalloc(klen, GFP_ATOMIC);
170 iv = ieee80211_wep_add_iv(local, skb, key);
176 len = skb->len - (iv + WEP_IV_LEN - skb->data);
178 /* Prepend 24-bit IV to RC4 key */
179 memcpy(rc4key, iv, 3);
181 /* Copy rest of the WEP key (the secret part) */
182 memcpy(rc4key + 3, key->key, key->keylen);
184 /* Add room for ICV */
185 skb_put(skb, WEP_ICV_LEN);
187 ieee80211_wep_encrypt_data(local->wep_tx_tfm, rc4key, klen,
188 iv + WEP_IV_LEN, len);
196 /* Perform WEP decryption using given key. data buffer includes encrypted
197 * payload, including 4-byte ICV, but _not_ IV. data_len must not include ICV.
198 * Return 0 on success and -1 on ICV mismatch. */
199 int ieee80211_wep_decrypt_data(struct crypto_blkcipher *tfm, u8 *rc4key,
200 size_t klen, u8 *data, size_t data_len)
202 struct blkcipher_desc desc = { .tfm = tfm };
203 struct scatterlist sg;
206 crypto_blkcipher_setkey(tfm, rc4key, klen);
207 sg.page = virt_to_page(data);
208 sg.offset = offset_in_page(data);
209 sg.length = data_len + WEP_ICV_LEN;
210 crypto_blkcipher_decrypt(&desc, &sg, &sg, sg.length);
212 crc = cpu_to_le32(~crc32_le(~0, data, data_len));
213 if (memcmp(&crc, data + data_len, WEP_ICV_LEN) != 0)
221 /* Perform WEP decryption on given skb. Buffer includes whole WEP part of
222 * the frame: IV (4 bytes), encrypted payload (including SNAP header),
223 * ICV (4 bytes). skb->len includes both IV and ICV.
225 * Returns 0 if frame was decrypted successfully and ICV was correct and -1 on
226 * failure. If frame is OK, IV and ICV will be removed, i.e., decrypted payload
227 * is moved to the beginning of the skb and skb length will be reduced.
229 int ieee80211_wep_decrypt(struct ieee80211_local *local, struct sk_buff *skb,
230 struct ieee80211_key *key)
235 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
241 fc = le16_to_cpu(hdr->frame_control);
242 if (!(fc & IEEE80211_FCTL_PROTECTED))
245 hdrlen = ieee80211_get_hdrlen(fc);
247 if (skb->len < 8 + hdrlen)
250 len = skb->len - hdrlen - 8;
252 keyidx = skb->data[hdrlen + 3] >> 6;
254 if (!key || keyidx != key->keyidx || key->alg != ALG_WEP)
257 klen = 3 + key->keylen;
259 rc4key = kmalloc(klen, GFP_ATOMIC);
263 /* Prepend 24-bit IV to RC4 key */
264 memcpy(rc4key, skb->data + hdrlen, 3);
266 /* Copy rest of the WEP key (the secret part) */
267 memcpy(rc4key + 3, key->key, key->keylen);
269 if (ieee80211_wep_decrypt_data(local->wep_rx_tfm, rc4key, klen,
270 skb->data + hdrlen + WEP_IV_LEN,
272 printk(KERN_DEBUG "WEP decrypt failed (ICV)\n");
279 skb_trim(skb, skb->len - WEP_ICV_LEN);
282 memmove(skb->data + WEP_IV_LEN, skb->data, hdrlen);
283 skb_pull(skb, WEP_IV_LEN);
289 int ieee80211_wep_get_keyidx(struct sk_buff *skb)
291 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
295 fc = le16_to_cpu(hdr->frame_control);
296 if (!(fc & IEEE80211_FCTL_PROTECTED))
299 hdrlen = ieee80211_get_hdrlen(fc);
301 if (skb->len < 8 + hdrlen)
304 return skb->data[hdrlen + 3] >> 6;
308 u8 * ieee80211_wep_is_weak_iv(struct sk_buff *skb, struct ieee80211_key *key)
310 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
316 fc = le16_to_cpu(hdr->frame_control);
317 if (!(fc & IEEE80211_FCTL_PROTECTED))
320 hdrlen = ieee80211_get_hdrlen(fc);
321 ivpos = skb->data + hdrlen;
322 iv = (ivpos[0] << 16) | (ivpos[1] << 8) | ivpos[2];
324 if (ieee80211_wep_weak_iv(iv, key->keylen))