1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * Software WEP encryption implementation
4 * Copyright 2002, Jouni Malinen <jkmaline@cc.hut.fi>
5 * Copyright 2003, Instant802 Networks, Inc.
6 */
7
8 #include <linux/netdevice.h>
9 #include <linux/types.h>
10 #include <linux/random.h>
11 #include <linux/compiler.h>
12 #include <linux/crc32.h>
13 #include <linux/crypto.h>
14 #include <linux/err.h>
15 #include <linux/mm.h>
16 #include <linux/scatterlist.h>
17 #include <linux/slab.h>
18 #include <asm/unaligned.h>
19
20 #include <net/mac80211.h>
21 #include "ieee80211_i.h"
22 #include "wep.h"
23
24
ieee80211_wep_init(struct ieee80211_local * local)25 void ieee80211_wep_init(struct ieee80211_local *local)
26 {
27 /* start WEP IV from a random value */
28 get_random_bytes(&local->wep_iv, IEEE80211_WEP_IV_LEN);
29 }
30
ieee80211_wep_weak_iv(u32 iv,int keylen)31 static inline bool ieee80211_wep_weak_iv(u32 iv, int keylen)
32 {
33 /*
34 * Fluhrer, Mantin, and Shamir have reported weaknesses in the
35 * key scheduling algorithm of RC4. At least IVs (KeyByte + 3,
36 * 0xff, N) can be used to speedup attacks, so avoid using them.
37 */
38 if ((iv & 0xff00) == 0xff00) {
39 u8 B = (iv >> 16) & 0xff;
40 if (B >= 3 && B < 3 + keylen)
41 return true;
42 }
43 return false;
44 }
45
46
ieee80211_wep_get_iv(struct ieee80211_local * local,int keylen,int keyidx,u8 * iv)47 static void ieee80211_wep_get_iv(struct ieee80211_local *local,
48 int keylen, int keyidx, u8 *iv)
49 {
50 local->wep_iv++;
51 if (ieee80211_wep_weak_iv(local->wep_iv, keylen))
52 local->wep_iv += 0x0100;
53
54 if (!iv)
55 return;
56
57 *iv++ = (local->wep_iv >> 16) & 0xff;
58 *iv++ = (local->wep_iv >> 8) & 0xff;
59 *iv++ = local->wep_iv & 0xff;
60 *iv++ = keyidx << 6;
61 }
62
63
ieee80211_wep_add_iv(struct ieee80211_local * local,struct sk_buff * skb,int keylen,int keyidx)64 static u8 *ieee80211_wep_add_iv(struct ieee80211_local *local,
65 struct sk_buff *skb,
66 int keylen, int keyidx)
67 {
68 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
69 struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
70 unsigned int hdrlen;
71 u8 *newhdr;
72
73 hdr->frame_control |= cpu_to_le16(IEEE80211_FCTL_PROTECTED);
74
75 if (WARN_ON(skb_headroom(skb) < IEEE80211_WEP_IV_LEN))
76 return NULL;
77
78 hdrlen = ieee80211_hdrlen(hdr->frame_control);
79 newhdr = skb_push(skb, IEEE80211_WEP_IV_LEN);
80 memmove(newhdr, newhdr + IEEE80211_WEP_IV_LEN, hdrlen);
81
82 /* the HW only needs room for the IV, but not the actual IV */
83 if (info->control.hw_key &&
84 (info->control.hw_key->flags & IEEE80211_KEY_FLAG_PUT_IV_SPACE))
85 return newhdr + hdrlen;
86
87 ieee80211_wep_get_iv(local, keylen, keyidx, newhdr + hdrlen);
88 return newhdr + hdrlen;
89 }
90
91
ieee80211_wep_remove_iv(struct ieee80211_local * local,struct sk_buff * skb,struct ieee80211_key * key)92 static void ieee80211_wep_remove_iv(struct ieee80211_local *local,
93 struct sk_buff *skb,
94 struct ieee80211_key *key)
95 {
96 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
97 unsigned int hdrlen;
98
99 hdrlen = ieee80211_hdrlen(hdr->frame_control);
100 memmove(skb->data + IEEE80211_WEP_IV_LEN, skb->data, hdrlen);
101 skb_pull(skb, IEEE80211_WEP_IV_LEN);
102 }
103
104
105 /* Perform WEP encryption using given key. data buffer must have tailroom
106 * for 4-byte ICV. data_len must not include this ICV. Note: this function
107 * does _not_ add IV. data = RC4(data | CRC32(data)) */
ieee80211_wep_encrypt_data(struct arc4_ctx * ctx,u8 * rc4key,size_t klen,u8 * data,size_t data_len)108 int ieee80211_wep_encrypt_data(struct arc4_ctx *ctx, u8 *rc4key,
109 size_t klen, u8 *data, size_t data_len)
110 {
111 __le32 icv;
112
113 icv = cpu_to_le32(~crc32_le(~0, data, data_len));
114 put_unaligned(icv, (__le32 *)(data + data_len));
115
116 arc4_setkey(ctx, rc4key, klen);
117 arc4_crypt(ctx, data, data, data_len + IEEE80211_WEP_ICV_LEN);
118 memzero_explicit(ctx, sizeof(*ctx));
119
120 return 0;
121 }
122
123
124 /* Perform WEP encryption on given skb. 4 bytes of extra space (IV) in the
125 * beginning of the buffer 4 bytes of extra space (ICV) in the end of the
126 * buffer will be added. Both IV and ICV will be transmitted, so the
127 * payload length increases with 8 bytes.
128 *
129 * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data))
130 */
ieee80211_wep_encrypt(struct ieee80211_local * local,struct sk_buff * skb,const u8 * key,int keylen,int keyidx)131 int ieee80211_wep_encrypt(struct ieee80211_local *local,
132 struct sk_buff *skb,
133 const u8 *key, int keylen, int keyidx)
134 {
135 u8 *iv;
136 size_t len;
137 u8 rc4key[3 + WLAN_KEY_LEN_WEP104];
138
139 if (WARN_ON(skb_tailroom(skb) < IEEE80211_WEP_ICV_LEN))
140 return -1;
141
142 iv = ieee80211_wep_add_iv(local, skb, keylen, keyidx);
143 if (!iv)
144 return -1;
145
146 len = skb->len - (iv + IEEE80211_WEP_IV_LEN - skb->data);
147
148 /* Prepend 24-bit IV to RC4 key */
149 memcpy(rc4key, iv, 3);
150
151 /* Copy rest of the WEP key (the secret part) */
152 memcpy(rc4key + 3, key, keylen);
153
154 /* Add room for ICV */
155 skb_put(skb, IEEE80211_WEP_ICV_LEN);
156
157 return ieee80211_wep_encrypt_data(&local->wep_tx_ctx, rc4key, keylen + 3,
158 iv + IEEE80211_WEP_IV_LEN, len);
159 }
160
161
162 /* Perform WEP decryption using given key. data buffer includes encrypted
163 * payload, including 4-byte ICV, but _not_ IV. data_len must not include ICV.
164 * Return 0 on success and -1 on ICV mismatch. */
ieee80211_wep_decrypt_data(struct arc4_ctx * ctx,u8 * rc4key,size_t klen,u8 * data,size_t data_len)165 int ieee80211_wep_decrypt_data(struct arc4_ctx *ctx, u8 *rc4key,
166 size_t klen, u8 *data, size_t data_len)
167 {
168 __le32 crc;
169
170 arc4_setkey(ctx, rc4key, klen);
171 arc4_crypt(ctx, data, data, data_len + IEEE80211_WEP_ICV_LEN);
172 memzero_explicit(ctx, sizeof(*ctx));
173
174 crc = cpu_to_le32(~crc32_le(~0, data, data_len));
175 if (memcmp(&crc, data + data_len, IEEE80211_WEP_ICV_LEN) != 0)
176 /* ICV mismatch */
177 return -1;
178
179 return 0;
180 }
181
182
183 /* Perform WEP decryption on given skb. Buffer includes whole WEP part of
184 * the frame: IV (4 bytes), encrypted payload (including SNAP header),
185 * ICV (4 bytes). skb->len includes both IV and ICV.
186 *
187 * Returns 0 if frame was decrypted successfully and ICV was correct and -1 on
188 * failure. If frame is OK, IV and ICV will be removed, i.e., decrypted payload
189 * is moved to the beginning of the skb and skb length will be reduced.
190 */
ieee80211_wep_decrypt(struct ieee80211_local * local,struct sk_buff * skb,struct ieee80211_key * key)191 static int ieee80211_wep_decrypt(struct ieee80211_local *local,
192 struct sk_buff *skb,
193 struct ieee80211_key *key)
194 {
195 u32 klen;
196 u8 rc4key[3 + WLAN_KEY_LEN_WEP104];
197 u8 keyidx;
198 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
199 unsigned int hdrlen;
200 size_t len;
201 int ret = 0;
202
203 if (!ieee80211_has_protected(hdr->frame_control))
204 return -1;
205
206 hdrlen = ieee80211_hdrlen(hdr->frame_control);
207 if (skb->len < hdrlen + IEEE80211_WEP_IV_LEN + IEEE80211_WEP_ICV_LEN)
208 return -1;
209
210 len = skb->len - hdrlen - IEEE80211_WEP_IV_LEN - IEEE80211_WEP_ICV_LEN;
211
212 keyidx = skb->data[hdrlen + 3] >> 6;
213
214 if (!key || keyidx != key->conf.keyidx)
215 return -1;
216
217 klen = 3 + key->conf.keylen;
218
219 /* Prepend 24-bit IV to RC4 key */
220 memcpy(rc4key, skb->data + hdrlen, 3);
221
222 /* Copy rest of the WEP key (the secret part) */
223 memcpy(rc4key + 3, key->conf.key, key->conf.keylen);
224
225 if (ieee80211_wep_decrypt_data(&local->wep_rx_ctx, rc4key, klen,
226 skb->data + hdrlen +
227 IEEE80211_WEP_IV_LEN, len))
228 ret = -1;
229
230 /* Trim ICV */
231 skb_trim(skb, skb->len - IEEE80211_WEP_ICV_LEN);
232
233 /* Remove IV */
234 memmove(skb->data + IEEE80211_WEP_IV_LEN, skb->data, hdrlen);
235 skb_pull(skb, IEEE80211_WEP_IV_LEN);
236
237 return ret;
238 }
239
240 ieee80211_rx_result
ieee80211_crypto_wep_decrypt(struct ieee80211_rx_data * rx)241 ieee80211_crypto_wep_decrypt(struct ieee80211_rx_data *rx)
242 {
243 struct sk_buff *skb = rx->skb;
244 struct ieee80211_rx_status *status = IEEE80211_SKB_RXCB(skb);
245 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
246 __le16 fc = hdr->frame_control;
247
248 if (!ieee80211_is_data(fc) && !ieee80211_is_auth(fc))
249 return RX_CONTINUE;
250
251 if (!(status->flag & RX_FLAG_DECRYPTED)) {
252 if (skb_linearize(rx->skb))
253 return RX_DROP_UNUSABLE;
254 if (ieee80211_wep_decrypt(rx->local, rx->skb, rx->key))
255 return RX_DROP_UNUSABLE;
256 } else if (!(status->flag & RX_FLAG_IV_STRIPPED)) {
257 if (!pskb_may_pull(rx->skb, ieee80211_hdrlen(fc) +
258 IEEE80211_WEP_IV_LEN))
259 return RX_DROP_UNUSABLE;
260 ieee80211_wep_remove_iv(rx->local, rx->skb, rx->key);
261 /* remove ICV */
262 if (!(status->flag & RX_FLAG_ICV_STRIPPED) &&
263 pskb_trim(rx->skb, rx->skb->len - IEEE80211_WEP_ICV_LEN))
264 return RX_DROP_UNUSABLE;
265 }
266
267 return RX_CONTINUE;
268 }
269
wep_encrypt_skb(struct ieee80211_tx_data * tx,struct sk_buff * skb)270 static int wep_encrypt_skb(struct ieee80211_tx_data *tx, struct sk_buff *skb)
271 {
272 struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
273 struct ieee80211_key_conf *hw_key = info->control.hw_key;
274
275 if (!hw_key) {
276 if (ieee80211_wep_encrypt(tx->local, skb, tx->key->conf.key,
277 tx->key->conf.keylen,
278 tx->key->conf.keyidx))
279 return -1;
280 } else if ((hw_key->flags & IEEE80211_KEY_FLAG_GENERATE_IV) ||
281 (hw_key->flags & IEEE80211_KEY_FLAG_PUT_IV_SPACE)) {
282 if (!ieee80211_wep_add_iv(tx->local, skb,
283 tx->key->conf.keylen,
284 tx->key->conf.keyidx))
285 return -1;
286 }
287
288 return 0;
289 }
290
291 ieee80211_tx_result
ieee80211_crypto_wep_encrypt(struct ieee80211_tx_data * tx)292 ieee80211_crypto_wep_encrypt(struct ieee80211_tx_data *tx)
293 {
294 struct sk_buff *skb;
295
296 ieee80211_tx_set_protected(tx);
297
298 skb_queue_walk(&tx->skbs, skb) {
299 if (wep_encrypt_skb(tx, skb) < 0) {
300 I802_DEBUG_INC(tx->local->tx_handlers_drop_wep);
301 return TX_DROP;
302 }
303 }
304
305 return TX_CONTINUE;
306 }
307