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1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Software WEP encryption implementation
4 * Copyright 2002, Jouni Malinen <[email protected]>
5 * Copyright 2003, Instant802 Networks, Inc.
6 * Copyright (C) 2023 Intel Corporation
7 */
8
9#include <linux/netdevice.h>
10#include <linux/types.h>
11#include <linux/random.h>
12#include <linux/compiler.h>
13#include <linux/crc32.h>
14#include <linux/crypto.h>
15#include <linux/err.h>
16#include <linux/mm.h>
17#include <linux/scatterlist.h>
18#include <linux/slab.h>
19#include <linux/unaligned.h>
20
21#include <net/mac80211.h>
22#include "ieee80211_i.h"
23#include "wep.h"
24
25
26void ieee80211_wep_init(struct ieee80211_local *local)
27{
28 /* start WEP IV from a random value */
29 get_random_bytes(&local->wep_iv, IEEE80211_WEP_IV_LEN);
30}
31
32static inline bool ieee80211_wep_weak_iv(u32 iv, int keylen)
33{
34 /*
35 * Fluhrer, Mantin, and Shamir have reported weaknesses in the
36 * key scheduling algorithm of RC4. At least IVs (KeyByte + 3,
37 * 0xff, N) can be used to speedup attacks, so avoid using them.
38 */
39 if ((iv & 0xff00) == 0xff00) {
40 u8 B = (iv >> 16) & 0xff;
41 if (B >= 3 && B < 3 + keylen)
42 return true;
43 }
44 return false;
45}
46
47
48static void ieee80211_wep_get_iv(struct ieee80211_local *local,
49 int keylen, int keyidx, u8 *iv)
50{
51 local->wep_iv++;
52 if (ieee80211_wep_weak_iv(local->wep_iv, keylen))
53 local->wep_iv += 0x0100;
54
55 if (!iv)
56 return;
57
58 *iv++ = (local->wep_iv >> 16) & 0xff;
59 *iv++ = (local->wep_iv >> 8) & 0xff;
60 *iv++ = local->wep_iv & 0xff;
61 *iv++ = keyidx << 6;
62}
63
64
65static u8 *ieee80211_wep_add_iv(struct ieee80211_local *local,
66 struct sk_buff *skb,
67 int keylen, int keyidx)
68{
69 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
70 struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
71 unsigned int hdrlen;
72 u8 *newhdr;
73
74 hdr->frame_control |= cpu_to_le16(IEEE80211_FCTL_PROTECTED);
75
76 if (WARN_ON(skb_headroom(skb) < IEEE80211_WEP_IV_LEN))
77 return NULL;
78
79 hdrlen = ieee80211_hdrlen(hdr->frame_control);
80 newhdr = skb_push(skb, IEEE80211_WEP_IV_LEN);
81 memmove(newhdr, newhdr + IEEE80211_WEP_IV_LEN, hdrlen);
82
83 /* the HW only needs room for the IV, but not the actual IV */
84 if (info->control.hw_key &&
85 (info->control.hw_key->flags & IEEE80211_KEY_FLAG_PUT_IV_SPACE))
86 return newhdr + hdrlen;
87
88 ieee80211_wep_get_iv(local, keylen, keyidx, newhdr + hdrlen);
89 return newhdr + hdrlen;
90}
91
92
93static void ieee80211_wep_remove_iv(struct ieee80211_local *local,
94 struct sk_buff *skb,
95 struct ieee80211_key *key)
96{
97 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
98 unsigned int hdrlen;
99
100 hdrlen = ieee80211_hdrlen(hdr->frame_control);
101 memmove(skb->data + IEEE80211_WEP_IV_LEN, skb->data, hdrlen);
102 skb_pull(skb, IEEE80211_WEP_IV_LEN);
103}
104
105
106/* Perform WEP encryption using given key. data buffer must have tailroom
107 * for 4-byte ICV. data_len must not include this ICV. Note: this function
108 * does _not_ add IV. data = RC4(data | CRC32(data)) */
109int ieee80211_wep_encrypt_data(struct arc4_ctx *ctx, u8 *rc4key,
110 size_t klen, u8 *data, size_t data_len)
111{
112 __le32 icv;
113
114 icv = cpu_to_le32(~crc32_le(~0, data, data_len));
115 put_unaligned(icv, (__le32 *)(data + data_len));
116
117 arc4_setkey(ctx, rc4key, klen);
118 arc4_crypt(ctx, data, data, data_len + IEEE80211_WEP_ICV_LEN);
119 memzero_explicit(ctx, sizeof(*ctx));
120
121 return 0;
122}
123
124
125/* Perform WEP encryption on given skb. 4 bytes of extra space (IV) in the
126 * beginning of the buffer 4 bytes of extra space (ICV) in the end of the
127 * buffer will be added. Both IV and ICV will be transmitted, so the
128 * payload length increases with 8 bytes.
129 *
130 * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data))
131 */
132int ieee80211_wep_encrypt(struct ieee80211_local *local,
133 struct sk_buff *skb,
134 const u8 *key, int keylen, int keyidx)
135{
136 u8 *iv;
137 size_t len;
138 u8 rc4key[3 + WLAN_KEY_LEN_WEP104];
139
140 if (WARN_ON(skb_tailroom(skb) < IEEE80211_WEP_ICV_LEN))
141 return -1;
142
143 iv = ieee80211_wep_add_iv(local, skb, keylen, keyidx);
144 if (!iv)
145 return -1;
146
147 len = skb->len - (iv + IEEE80211_WEP_IV_LEN - skb->data);
148
149 /* Prepend 24-bit IV to RC4 key */
150 memcpy(rc4key, iv, 3);
151
152 /* Copy rest of the WEP key (the secret part) */
153 memcpy(rc4key + 3, key, keylen);
154
155 /* Add room for ICV */
156 skb_put(skb, IEEE80211_WEP_ICV_LEN);
157
158 return ieee80211_wep_encrypt_data(&local->wep_tx_ctx, rc4key, keylen + 3,
159 iv + IEEE80211_WEP_IV_LEN, len);
160}
161
162
163/* Perform WEP decryption using given key. data buffer includes encrypted
164 * payload, including 4-byte ICV, but _not_ IV. data_len must not include ICV.
165 * Return 0 on success and -1 on ICV mismatch. */
166int ieee80211_wep_decrypt_data(struct arc4_ctx *ctx, u8 *rc4key,
167 size_t klen, u8 *data, size_t data_len)
168{
169 __le32 crc;
170
171 arc4_setkey(ctx, rc4key, klen);
172 arc4_crypt(ctx, data, data, data_len + IEEE80211_WEP_ICV_LEN);
173 memzero_explicit(ctx, sizeof(*ctx));
174
175 crc = cpu_to_le32(~crc32_le(~0, data, data_len));
176 if (memcmp(&crc, data + data_len, IEEE80211_WEP_ICV_LEN) != 0)
177 /* ICV mismatch */
178 return -1;
179
180 return 0;
181}
182
183
184/* Perform WEP decryption on given skb. Buffer includes whole WEP part of
185 * the frame: IV (4 bytes), encrypted payload (including SNAP header),
186 * ICV (4 bytes). skb->len includes both IV and ICV.
187 *
188 * Returns 0 if frame was decrypted successfully and ICV was correct and -1 on
189 * failure. If frame is OK, IV and ICV will be removed, i.e., decrypted payload
190 * is moved to the beginning of the skb and skb length will be reduced.
191 */
192static int ieee80211_wep_decrypt(struct ieee80211_local *local,
193 struct sk_buff *skb,
194 struct ieee80211_key *key)
195{
196 u32 klen;
197 u8 rc4key[3 + WLAN_KEY_LEN_WEP104];
198 u8 keyidx;
199 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
200 unsigned int hdrlen;
201 size_t len;
202 int ret = 0;
203
204 if (!ieee80211_has_protected(hdr->frame_control))
205 return -1;
206
207 hdrlen = ieee80211_hdrlen(hdr->frame_control);
208 if (skb->len < hdrlen + IEEE80211_WEP_IV_LEN + IEEE80211_WEP_ICV_LEN)
209 return -1;
210
211 len = skb->len - hdrlen - IEEE80211_WEP_IV_LEN - IEEE80211_WEP_ICV_LEN;
212
213 keyidx = skb->data[hdrlen + 3] >> 6;
214
215 if (!key || keyidx != key->conf.keyidx)
216 return -1;
217
218 klen = 3 + key->conf.keylen;
219
220 /* Prepend 24-bit IV to RC4 key */
221 memcpy(rc4key, skb->data + hdrlen, 3);
222
223 /* Copy rest of the WEP key (the secret part) */
224 memcpy(rc4key + 3, key->conf.key, key->conf.keylen);
225
226 if (ieee80211_wep_decrypt_data(&local->wep_rx_ctx, rc4key, klen,
227 skb->data + hdrlen +
228 IEEE80211_WEP_IV_LEN, len))
229 ret = -1;
230
231 /* Trim ICV */
232 skb_trim(skb, skb->len - IEEE80211_WEP_ICV_LEN);
233
234 /* Remove IV */
235 memmove(skb->data + IEEE80211_WEP_IV_LEN, skb->data, hdrlen);
236 skb_pull(skb, IEEE80211_WEP_IV_LEN);
237
238 return ret;
239}
240
241ieee80211_rx_result
242ieee80211_crypto_wep_decrypt(struct ieee80211_rx_data *rx)
243{
244 struct sk_buff *skb = rx->skb;
245 struct ieee80211_rx_status *status = IEEE80211_SKB_RXCB(skb);
246 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
247 __le16 fc = hdr->frame_control;
248
249 if (!ieee80211_is_data(fc) && !ieee80211_is_auth(fc))
250 return RX_CONTINUE;
251
252 if (!(status->flag & RX_FLAG_DECRYPTED)) {
253 if (skb_linearize(rx->skb))
254 return RX_DROP_U_OOM;
255 if (ieee80211_wep_decrypt(rx->local, rx->skb, rx->key))
256 return RX_DROP_U_WEP_DEC_FAIL;
257 } else if (!(status->flag & RX_FLAG_IV_STRIPPED)) {
258 if (!pskb_may_pull(rx->skb, ieee80211_hdrlen(fc) +
259 IEEE80211_WEP_IV_LEN))
260 return RX_DROP_U_NO_IV;
261 ieee80211_wep_remove_iv(rx->local, rx->skb, rx->key);
262 /* remove ICV */
263 if (!(status->flag & RX_FLAG_ICV_STRIPPED) &&
264 pskb_trim(rx->skb, rx->skb->len - IEEE80211_WEP_ICV_LEN))
265 return RX_DROP_U_NO_ICV;
266 }
267
268 return RX_CONTINUE;
269}
270
271static int wep_encrypt_skb(struct ieee80211_tx_data *tx, struct sk_buff *skb)
272{
273 struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
274 struct ieee80211_key_conf *hw_key = info->control.hw_key;
275
276 if (!hw_key) {
277 if (ieee80211_wep_encrypt(tx->local, skb, tx->key->conf.key,
278 tx->key->conf.keylen,
279 tx->key->conf.keyidx))
280 return -1;
281 } else if ((hw_key->flags & IEEE80211_KEY_FLAG_GENERATE_IV) ||
282 (hw_key->flags & IEEE80211_KEY_FLAG_PUT_IV_SPACE)) {
283 if (!ieee80211_wep_add_iv(tx->local, skb,
284 tx->key->conf.keylen,
285 tx->key->conf.keyidx))
286 return -1;
287 }
288
289 return 0;
290}
291
292ieee80211_tx_result
293ieee80211_crypto_wep_encrypt(struct ieee80211_tx_data *tx)
294{
295 struct sk_buff *skb;
296
297 ieee80211_tx_set_protected(tx);
298
299 skb_queue_walk(&tx->skbs, skb) {
300 if (wep_encrypt_skb(tx, skb) < 0) {
301 I802_DEBUG_INC(tx->local->tx_handlers_drop_wep);
302 return TX_DROP;
303 }
304 }
305
306 return TX_CONTINUE;
307}