1/*
2 * Software WEP encryption implementation
3 * Copyright 2002, Jouni Malinen <jkmaline@cc.hut.fi>
4 * Copyright 2003, Instant802 Networks, Inc.
5 *
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.
9 */
10
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>
18#include <linux/mm.h>
19#include <linux/scatterlist.h>
20#include <linux/slab.h>
21#include <asm/unaligned.h>
22
23#include <net/mac80211.h>
24#include "ieee80211_i.h"
25#include "wep.h"
26
27
28int ieee80211_wep_init(struct ieee80211_local *local)
29{
30	/* start WEP IV from a random value */
31	get_random_bytes(&local->wep_iv, IEEE80211_WEP_IV_LEN);
32
33	local->wep_tx_tfm = crypto_alloc_cipher("arc4", 0, CRYPTO_ALG_ASYNC);
34	if (IS_ERR(local->wep_tx_tfm)) {
35		local->wep_rx_tfm = ERR_PTR(-EINVAL);
36		return PTR_ERR(local->wep_tx_tfm);
37	}
38
39	local->wep_rx_tfm = crypto_alloc_cipher("arc4", 0, CRYPTO_ALG_ASYNC);
40	if (IS_ERR(local->wep_rx_tfm)) {
41		crypto_free_cipher(local->wep_tx_tfm);
42		local->wep_tx_tfm = ERR_PTR(-EINVAL);
43		return PTR_ERR(local->wep_rx_tfm);
44	}
45
46	return 0;
47}
48
49void ieee80211_wep_free(struct ieee80211_local *local)
50{
51	if (!IS_ERR(local->wep_tx_tfm))
52		crypto_free_cipher(local->wep_tx_tfm);
53	if (!IS_ERR(local->wep_rx_tfm))
54		crypto_free_cipher(local->wep_rx_tfm);
55}
56
57static inline bool ieee80211_wep_weak_iv(u32 iv, int keylen)
58{
59	/*
60	 * Fluhrer, Mantin, and Shamir have reported weaknesses in the
61	 * key scheduling algorithm of RC4. At least IVs (KeyByte + 3,
62	 * 0xff, N) can be used to speedup attacks, so avoid using them.
63	 */
64	if ((iv & 0xff00) == 0xff00) {
65		u8 B = (iv >> 16) & 0xff;
66		if (B >= 3 && B < 3 + keylen)
67			return true;
68	}
69	return false;
70}
71
72
73static void ieee80211_wep_get_iv(struct ieee80211_local *local,
74				 int keylen, int keyidx, u8 *iv)
75{
76	local->wep_iv++;
77	if (ieee80211_wep_weak_iv(local->wep_iv, keylen))
78		local->wep_iv += 0x0100;
79
80	if (!iv)
81		return;
82
83	*iv++ = (local->wep_iv >> 16) & 0xff;
84	*iv++ = (local->wep_iv >> 8) & 0xff;
85	*iv++ = local->wep_iv & 0xff;
86	*iv++ = keyidx << 6;
87}
88
89
90static u8 *ieee80211_wep_add_iv(struct ieee80211_local *local,
91				struct sk_buff *skb,
92				int keylen, int keyidx)
93{
94	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
95	struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
96	unsigned int hdrlen;
97	u8 *newhdr;
98
99	hdr->frame_control |= cpu_to_le16(IEEE80211_FCTL_PROTECTED);
100
101	if (WARN_ON(skb_headroom(skb) < IEEE80211_WEP_IV_LEN))
102		return NULL;
103
104	hdrlen = ieee80211_hdrlen(hdr->frame_control);
105	newhdr = skb_push(skb, IEEE80211_WEP_IV_LEN);
106	memmove(newhdr, newhdr + IEEE80211_WEP_IV_LEN, hdrlen);
107
108	/* the HW only needs room for the IV, but not the actual IV */
109	if (info->control.hw_key &&
110	    (info->control.hw_key->flags & IEEE80211_KEY_FLAG_PUT_IV_SPACE))
111		return newhdr + hdrlen;
112
113	ieee80211_wep_get_iv(local, keylen, keyidx, newhdr + hdrlen);
114	return newhdr + hdrlen;
115}
116
117
118static void ieee80211_wep_remove_iv(struct ieee80211_local *local,
119				    struct sk_buff *skb,
120				    struct ieee80211_key *key)
121{
122	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
123	unsigned int hdrlen;
124
125	hdrlen = ieee80211_hdrlen(hdr->frame_control);
126	memmove(skb->data + IEEE80211_WEP_IV_LEN, skb->data, hdrlen);
127	skb_pull(skb, IEEE80211_WEP_IV_LEN);
128}
129
130
131/* Perform WEP encryption using given key. data buffer must have tailroom
132 * for 4-byte ICV. data_len must not include this ICV. Note: this function
133 * does _not_ add IV. data = RC4(data | CRC32(data)) */
134int ieee80211_wep_encrypt_data(struct crypto_cipher *tfm, u8 *rc4key,
135			       size_t klen, u8 *data, size_t data_len)
136{
137	__le32 icv;
138	int i;
139
140	if (IS_ERR(tfm))
141		return -1;
142
143	icv = cpu_to_le32(~crc32_le(~0, data, data_len));
144	put_unaligned(icv, (__le32 *)(data + data_len));
145
146	crypto_cipher_setkey(tfm, rc4key, klen);
147	for (i = 0; i < data_len + IEEE80211_WEP_ICV_LEN; i++)
148		crypto_cipher_encrypt_one(tfm, data + i, data + i);
149
150	return 0;
151}
152
153
154/* Perform WEP encryption on given skb. 4 bytes of extra space (IV) in the
155 * beginning of the buffer 4 bytes of extra space (ICV) in the end of the
156 * buffer will be added. Both IV and ICV will be transmitted, so the
157 * payload length increases with 8 bytes.
158 *
159 * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data))
160 */
161int ieee80211_wep_encrypt(struct ieee80211_local *local,
162			  struct sk_buff *skb,
163			  const u8 *key, int keylen, int keyidx)
164{
165	u8 *iv;
166	size_t len;
167	u8 rc4key[3 + WLAN_KEY_LEN_WEP104];
168
169	if (WARN_ON(skb_tailroom(skb) < IEEE80211_WEP_ICV_LEN))
170		return -1;
171
172	iv = ieee80211_wep_add_iv(local, skb, keylen, keyidx);
173	if (!iv)
174		return -1;
175
176	len = skb->len - (iv + IEEE80211_WEP_IV_LEN - skb->data);
177
178	/* Prepend 24-bit IV to RC4 key */
179	memcpy(rc4key, iv, 3);
180
181	/* Copy rest of the WEP key (the secret part) */
182	memcpy(rc4key + 3, key, keylen);
183
184	/* Add room for ICV */
185	skb_put(skb, IEEE80211_WEP_ICV_LEN);
186
187	return ieee80211_wep_encrypt_data(local->wep_tx_tfm, rc4key, keylen + 3,
188					  iv + IEEE80211_WEP_IV_LEN, len);
189}
190
191
192/* Perform WEP decryption using given key. data buffer includes encrypted
193 * payload, including 4-byte ICV, but _not_ IV. data_len must not include ICV.
194 * Return 0 on success and -1 on ICV mismatch. */
195int ieee80211_wep_decrypt_data(struct crypto_cipher *tfm, u8 *rc4key,
196			       size_t klen, u8 *data, size_t data_len)
197{
198	__le32 crc;
199	int i;
200
201	if (IS_ERR(tfm))
202		return -1;
203
204	crypto_cipher_setkey(tfm, rc4key, klen);
205	for (i = 0; i < data_len + IEEE80211_WEP_ICV_LEN; i++)
206		crypto_cipher_decrypt_one(tfm, data + i, data + i);
207
208	crc = cpu_to_le32(~crc32_le(~0, data, data_len));
209	if (memcmp(&crc, data + data_len, IEEE80211_WEP_ICV_LEN) != 0)
210		/* ICV mismatch */
211		return -1;
212
213	return 0;
214}
215
216
217/* Perform WEP decryption on given skb. Buffer includes whole WEP part of
218 * the frame: IV (4 bytes), encrypted payload (including SNAP header),
219 * ICV (4 bytes). skb->len includes both IV and ICV.
220 *
221 * Returns 0 if frame was decrypted successfully and ICV was correct and -1 on
222 * failure. If frame is OK, IV and ICV will be removed, i.e., decrypted payload
223 * is moved to the beginning of the skb and skb length will be reduced.
224 */
225static int ieee80211_wep_decrypt(struct ieee80211_local *local,
226				 struct sk_buff *skb,
227				 struct ieee80211_key *key)
228{
229	u32 klen;
230	u8 rc4key[3 + WLAN_KEY_LEN_WEP104];
231	u8 keyidx;
232	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
233	unsigned int hdrlen;
234	size_t len;
235	int ret = 0;
236
237	if (!ieee80211_has_protected(hdr->frame_control))
238		return -1;
239
240	hdrlen = ieee80211_hdrlen(hdr->frame_control);
241	if (skb->len < hdrlen + IEEE80211_WEP_IV_LEN + IEEE80211_WEP_ICV_LEN)
242		return -1;
243
244	len = skb->len - hdrlen - IEEE80211_WEP_IV_LEN - IEEE80211_WEP_ICV_LEN;
245
246	keyidx = skb->data[hdrlen + 3] >> 6;
247
248	if (!key || keyidx != key->conf.keyidx)
249		return -1;
250
251	klen = 3 + key->conf.keylen;
252
253	/* Prepend 24-bit IV to RC4 key */
254	memcpy(rc4key, skb->data + hdrlen, 3);
255
256	/* Copy rest of the WEP key (the secret part) */
257	memcpy(rc4key + 3, key->conf.key, key->conf.keylen);
258
259	if (ieee80211_wep_decrypt_data(local->wep_rx_tfm, rc4key, klen,
260				       skb->data + hdrlen +
261				       IEEE80211_WEP_IV_LEN, len))
262		ret = -1;
263
264	/* Trim ICV */
265	skb_trim(skb, skb->len - IEEE80211_WEP_ICV_LEN);
266
267	/* Remove IV */
268	memmove(skb->data + IEEE80211_WEP_IV_LEN, skb->data, hdrlen);
269	skb_pull(skb, IEEE80211_WEP_IV_LEN);
270
271	return ret;
272}
273
274ieee80211_rx_result
275ieee80211_crypto_wep_decrypt(struct ieee80211_rx_data *rx)
276{
277	struct sk_buff *skb = rx->skb;
278	struct ieee80211_rx_status *status = IEEE80211_SKB_RXCB(skb);
279	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
280	__le16 fc = hdr->frame_control;
281
282	if (!ieee80211_is_data(fc) && !ieee80211_is_auth(fc))
283		return RX_CONTINUE;
284
285	if (!(status->flag & RX_FLAG_DECRYPTED)) {
286		if (skb_linearize(rx->skb))
287			return RX_DROP_UNUSABLE;
288		if (ieee80211_wep_decrypt(rx->local, rx->skb, rx->key))
289			return RX_DROP_UNUSABLE;
290	} else if (!(status->flag & RX_FLAG_IV_STRIPPED)) {
291		if (!pskb_may_pull(rx->skb, ieee80211_hdrlen(fc) +
292					    IEEE80211_WEP_IV_LEN))
293			return RX_DROP_UNUSABLE;
294		ieee80211_wep_remove_iv(rx->local, rx->skb, rx->key);
295		/* remove ICV */
296		if (pskb_trim(rx->skb, rx->skb->len - IEEE80211_WEP_ICV_LEN))
297			return RX_DROP_UNUSABLE;
298	}
299
300	return RX_CONTINUE;
301}
302
303static int wep_encrypt_skb(struct ieee80211_tx_data *tx, struct sk_buff *skb)
304{
305	struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
306	struct ieee80211_key_conf *hw_key = info->control.hw_key;
307
308	if (!hw_key) {
309		if (ieee80211_wep_encrypt(tx->local, skb, tx->key->conf.key,
310					  tx->key->conf.keylen,
311					  tx->key->conf.keyidx))
312			return -1;
313	} else if ((hw_key->flags & IEEE80211_KEY_FLAG_GENERATE_IV) ||
314		   (hw_key->flags & IEEE80211_KEY_FLAG_PUT_IV_SPACE)) {
315		if (!ieee80211_wep_add_iv(tx->local, skb,
316					  tx->key->conf.keylen,
317					  tx->key->conf.keyidx))
318			return -1;
319	}
320
321	return 0;
322}
323
324ieee80211_tx_result
325ieee80211_crypto_wep_encrypt(struct ieee80211_tx_data *tx)
326{
327	struct sk_buff *skb;
328
329	ieee80211_tx_set_protected(tx);
330
331	skb_queue_walk(&tx->skbs, skb) {
332		if (wep_encrypt_skb(tx, skb) < 0) {
333			I802_DEBUG_INC(tx->local->tx_handlers_drop_wep);
334			return TX_DROP;
335		}
336	}
337
338	return TX_CONTINUE;
339}
340