1 // SPDX-License-Identifier: (GPL-2.0 OR MPL-1.1)
2 /*
3 *
4 * WEP encode/decode for P80211.
5 *
6 * Copyright (C) 2002 AbsoluteValue Systems, Inc. All Rights Reserved.
7 * --------------------------------------------------------------------
8 *
9 * linux-wlan
10 *
11 * The contents of this file are subject to the Mozilla Public
12 * License Version 1.1 (the "License"); you may not use this file
13 * except in compliance with the License. You may obtain a copy of
14 * the License at http://www.mozilla.org/MPL/
15 *
16 * Software distributed under the License is distributed on an "AS
17 * IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
18 * implied. See the License for the specific language governing
19 * rights and limitations under the License.
20 *
21 * Alternatively, the contents of this file may be used under the
22 * terms of the GNU Public License version 2 (the "GPL"), in which
23 * case the provisions of the GPL are applicable instead of the
24 * above. If you wish to allow the use of your version of this file
25 * only under the terms of the GPL and not to allow others to use
26 * your version of this file under the MPL, indicate your decision
27 * by deleting the provisions above and replace them with the notice
28 * and other provisions required by the GPL. If you do not delete
29 * the provisions above, a recipient may use your version of this
30 * file under either the MPL or the GPL.
31 *
32 * --------------------------------------------------------------------
33 *
34 * Inquiries regarding the linux-wlan Open Source project can be
35 * made directly to:
36 *
37 * AbsoluteValue Systems Inc.
38 * info@linux-wlan.com
39 * http://www.linux-wlan.com
40 *
41 * --------------------------------------------------------------------
42 *
43 * Portions of the development of this software were funded by
44 * Intersil Corporation as part of PRISM(R) chipset product development.
45 *
46 * --------------------------------------------------------------------
47 */
48
49 /*================================================================*/
50 /* System Includes */
51
52 #include <linux/crc32.h>
53 #include <linux/netdevice.h>
54 #include <linux/wireless.h>
55 #include <linux/random.h>
56 #include <linux/kernel.h>
57 #include "p80211hdr.h"
58 #include "p80211types.h"
59 #include "p80211msg.h"
60 #include "p80211conv.h"
61 #include "p80211netdev.h"
62
63 #define WEP_KEY(x) (((x) & 0xC0) >> 6)
64
65 /* keylen in bytes! */
66
wep_change_key(struct wlandevice * wlandev,int keynum,u8 * key,int keylen)67 int wep_change_key(struct wlandevice *wlandev, int keynum, u8 *key, int keylen)
68 {
69 if (keylen < 0)
70 return -1;
71 if (keylen >= MAX_KEYLEN)
72 return -1;
73 if (!key)
74 return -1;
75 if (keynum < 0)
76 return -1;
77 if (keynum >= NUM_WEPKEYS)
78 return -1;
79
80 wlandev->wep_keylens[keynum] = keylen;
81 memcpy(wlandev->wep_keys[keynum], key, keylen);
82
83 return 0;
84 }
85
86 /*
87 * 4-byte IV at start of buffer, 4-byte ICV at end of buffer.
88 * if successful, buf start is payload begin, length -= 8;
89 */
wep_decrypt(struct wlandevice * wlandev,u8 * buf,u32 len,int key_override,u8 * iv,u8 * icv)90 int wep_decrypt(struct wlandevice *wlandev, u8 *buf, u32 len, int key_override,
91 u8 *iv, u8 *icv)
92 {
93 u32 i, j, k, crc, keylen;
94 u8 s[256], key[64], c_crc[4];
95 u8 keyidx;
96
97 /* Needs to be at least 8 bytes of payload */
98 if (len <= 0)
99 return -1;
100
101 /* initialize the first bytes of the key from the IV */
102 key[0] = iv[0];
103 key[1] = iv[1];
104 key[2] = iv[2];
105 keyidx = WEP_KEY(iv[3]);
106
107 if (key_override >= 0)
108 keyidx = key_override;
109
110 if (keyidx >= NUM_WEPKEYS)
111 return -2;
112
113 keylen = wlandev->wep_keylens[keyidx];
114
115 if (keylen == 0)
116 return -3;
117
118 /* copy the rest of the key over from the designated key */
119 memcpy(key + 3, wlandev->wep_keys[keyidx], keylen);
120
121 keylen += 3; /* add in IV bytes */
122
123 /* set up the RC4 state */
124 for (i = 0; i < 256; i++)
125 s[i] = i;
126 j = 0;
127 for (i = 0; i < 256; i++) {
128 j = (j + s[i] + key[i % keylen]) & 0xff;
129 swap(i, j);
130 }
131
132 /* Apply the RC4 to the data, update the CRC32 */
133 i = 0;
134 j = 0;
135 for (k = 0; k < len; k++) {
136 i = (i + 1) & 0xff;
137 j = (j + s[i]) & 0xff;
138 swap(i, j);
139 buf[k] ^= s[(s[i] + s[j]) & 0xff];
140 }
141 crc = ~crc32_le(~0, buf, len);
142
143 /* now let's check the crc */
144 c_crc[0] = crc;
145 c_crc[1] = crc >> 8;
146 c_crc[2] = crc >> 16;
147 c_crc[3] = crc >> 24;
148
149 for (k = 0; k < 4; k++) {
150 i = (i + 1) & 0xff;
151 j = (j + s[i]) & 0xff;
152 swap(i, j);
153 if ((c_crc[k] ^ s[(s[i] + s[j]) & 0xff]) != icv[k])
154 return -(4 | (k << 4)); /* ICV mismatch */
155 }
156
157 return 0;
158 }
159
160 /* encrypts in-place. */
wep_encrypt(struct wlandevice * wlandev,u8 * buf,u8 * dst,u32 len,int keynum,u8 * iv,u8 * icv)161 int wep_encrypt(struct wlandevice *wlandev, u8 *buf,
162 u8 *dst, u32 len, int keynum, u8 *iv, u8 *icv)
163 {
164 u32 i, j, k, crc, keylen;
165 u8 s[256], key[64];
166
167 /* no point in WEPping an empty frame */
168 if (len <= 0)
169 return -1;
170
171 /* we need to have a real key.. */
172 if (keynum >= NUM_WEPKEYS)
173 return -2;
174 keylen = wlandev->wep_keylens[keynum];
175 if (keylen <= 0)
176 return -3;
177
178 /* use a random IV. And skip known weak ones. */
179 get_random_bytes(iv, 3);
180 while ((iv[1] == 0xff) && (iv[0] >= 3) && (iv[0] < keylen))
181 get_random_bytes(iv, 3);
182
183 iv[3] = (keynum & 0x03) << 6;
184
185 key[0] = iv[0];
186 key[1] = iv[1];
187 key[2] = iv[2];
188
189 /* copy the rest of the key over from the designated key */
190 memcpy(key + 3, wlandev->wep_keys[keynum], keylen);
191
192 keylen += 3; /* add in IV bytes */
193
194 /* set up the RC4 state */
195 for (i = 0; i < 256; i++)
196 s[i] = i;
197 j = 0;
198 for (i = 0; i < 256; i++) {
199 j = (j + s[i] + key[i % keylen]) & 0xff;
200 swap(i, j);
201 }
202
203 /* Update CRC32 then apply RC4 to the data */
204 i = 0;
205 j = 0;
206 for (k = 0; k < len; k++) {
207 i = (i + 1) & 0xff;
208 j = (j + s[i]) & 0xff;
209 swap(i, j);
210 dst[k] = buf[k] ^ s[(s[i] + s[j]) & 0xff];
211 }
212 crc = ~crc32_le(~0, buf, len);
213
214 /* now let's encrypt the crc */
215 icv[0] = crc;
216 icv[1] = crc >> 8;
217 icv[2] = crc >> 16;
218 icv[3] = crc >> 24;
219
220 for (k = 0; k < 4; k++) {
221 i = (i + 1) & 0xff;
222 j = (j + s[i]) & 0xff;
223 swap(i, j);
224 icv[k] ^= s[(s[i] + s[j]) & 0xff];
225 }
226
227 return 0;
228 }
229