1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Host AP crypt: host-based WEP encryption implementation for Host AP driver
4 *
5 * Copyright (c) 2002-2004, Jouni Malinen <jkmaline@cc.hut.fi>
6 */
7
8 #include <linux/fips.h>
9 #include <linux/module.h>
10 #include <linux/init.h>
11 #include <linux/slab.h>
12 #include <linux/random.h>
13 #include <linux/skbuff.h>
14 #include <linux/string.h>
15
16 #include "ieee80211.h"
17
18 #include <crypto/arc4.h>
19 #include <linux/crc32.h>
20
21 MODULE_AUTHOR("Jouni Malinen");
22 MODULE_DESCRIPTION("Host AP crypt: WEP");
23 MODULE_LICENSE("GPL");
24
25 struct prism2_wep_data {
26 u32 iv;
27 #define WEP_KEY_LEN 13
28 u8 key[WEP_KEY_LEN + 1];
29 u8 key_len;
30 u8 key_idx;
31 struct arc4_ctx rx_ctx_arc4;
32 struct arc4_ctx tx_ctx_arc4;
33 };
34
35
prism2_wep_init(int keyidx)36 static void *prism2_wep_init(int keyidx)
37 {
38 struct prism2_wep_data *priv;
39
40 if (fips_enabled)
41 return NULL;
42
43 priv = kzalloc(sizeof(*priv), GFP_KERNEL);
44 if (!priv)
45 return NULL;
46 priv->key_idx = keyidx;
47
48 /* start WEP IV from a random value */
49 get_random_bytes(&priv->iv, 4);
50
51 return priv;
52 }
53
54
prism2_wep_deinit(void * priv)55 static void prism2_wep_deinit(void *priv)
56 {
57 kfree_sensitive(priv);
58 }
59
60 /* Perform WEP encryption on given skb that has at least 4 bytes of headroom
61 * for IV and 4 bytes of tailroom for ICV. Both IV and ICV will be transmitted,
62 * so the payload length increases with 8 bytes.
63 *
64 * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data))
65 */
prism2_wep_encrypt(struct sk_buff * skb,int hdr_len,void * priv)66 static int prism2_wep_encrypt(struct sk_buff *skb, int hdr_len, void *priv)
67 {
68 struct prism2_wep_data *wep = priv;
69 u32 klen, len;
70 u8 key[WEP_KEY_LEN + 3];
71 u8 *pos;
72 struct cb_desc *tcb_desc = (struct cb_desc *)(skb->cb + MAX_DEV_ADDR_SIZE);
73 u32 crc;
74 u8 *icv;
75
76 if (skb_headroom(skb) < 4 || skb_tailroom(skb) < 4 ||
77 skb->len < hdr_len)
78 return -1;
79
80 len = skb->len - hdr_len;
81 pos = skb_push(skb, 4);
82 memmove(pos, pos + 4, hdr_len);
83 pos += hdr_len;
84
85 klen = 3 + wep->key_len;
86
87 wep->iv++;
88
89 /* Fluhrer, Mantin, and Shamir have reported weaknesses in the key
90 * scheduling algorithm of RC4. At least IVs (KeyByte + 3, 0xff, N)
91 * can be used to speedup attacks, so avoid using them.
92 */
93 if ((wep->iv & 0xff00) == 0xff00) {
94 u8 B = (wep->iv >> 16) & 0xff;
95
96 if (B >= 3 && B < klen)
97 wep->iv += 0x0100;
98 }
99
100 /* Prepend 24-bit IV to RC4 key and TX frame */
101 *pos++ = key[0] = (wep->iv >> 16) & 0xff;
102 *pos++ = key[1] = (wep->iv >> 8) & 0xff;
103 *pos++ = key[2] = wep->iv & 0xff;
104 *pos++ = wep->key_idx << 6;
105
106 /* Copy rest of the WEP key (the secret part) */
107 memcpy(key + 3, wep->key, wep->key_len);
108
109 if (!tcb_desc->bHwSec) {
110 /* Append little-endian CRC32 and encrypt it to produce ICV */
111 crc = ~crc32_le(~0, pos, len);
112 icv = skb_put(skb, 4);
113 icv[0] = crc;
114 icv[1] = crc >> 8;
115 icv[2] = crc >> 16;
116 icv[3] = crc >> 24;
117
118 arc4_setkey(&wep->tx_ctx_arc4, key, klen);
119 arc4_crypt(&wep->tx_ctx_arc4, pos, pos, len + 4);
120 }
121
122 return 0;
123 }
124
125
126 /* Perform WEP decryption on given buffer. Buffer includes whole WEP part of
127 * the frame: IV (4 bytes), encrypted payload (including SNAP header),
128 * ICV (4 bytes). len includes both IV and ICV.
129 *
130 * Returns 0 if frame was decrypted successfully and ICV was correct and -1 on
131 * failure. If frame is OK, IV and ICV will be removed.
132 */
prism2_wep_decrypt(struct sk_buff * skb,int hdr_len,void * priv)133 static int prism2_wep_decrypt(struct sk_buff *skb, int hdr_len, void *priv)
134 {
135 struct prism2_wep_data *wep = priv;
136 u32 klen, plen;
137 u8 key[WEP_KEY_LEN + 3];
138 u8 keyidx, *pos;
139 struct cb_desc *tcb_desc = (struct cb_desc *)(skb->cb + MAX_DEV_ADDR_SIZE);
140 u32 crc;
141 u8 icv[4];
142
143 if (skb->len < hdr_len + 8)
144 return -1;
145
146 pos = skb->data + hdr_len;
147 key[0] = *pos++;
148 key[1] = *pos++;
149 key[2] = *pos++;
150 keyidx = *pos++ >> 6;
151 if (keyidx != wep->key_idx)
152 return -1;
153
154 klen = 3 + wep->key_len;
155
156 /* Copy rest of the WEP key (the secret part) */
157 memcpy(key + 3, wep->key, wep->key_len);
158
159 /* Apply RC4 to data and compute CRC32 over decrypted data */
160 plen = skb->len - hdr_len - 8;
161
162 if (!tcb_desc->bHwSec) {
163 arc4_setkey(&wep->rx_ctx_arc4, key, klen);
164 arc4_crypt(&wep->rx_ctx_arc4, pos, pos, plen + 4);
165
166 crc = ~crc32_le(~0, pos, plen);
167 icv[0] = crc;
168 icv[1] = crc >> 8;
169 icv[2] = crc >> 16;
170 icv[3] = crc >> 24;
171 if (memcmp(icv, pos + plen, 4) != 0) {
172 /* ICV mismatch - drop frame */
173 return -2;
174 }
175 }
176 /* Remove IV and ICV */
177 memmove(skb->data + 4, skb->data, hdr_len);
178 skb_pull(skb, 4);
179 skb_trim(skb, skb->len - 4);
180
181 return 0;
182 }
183
184
prism2_wep_set_key(void * key,int len,u8 * seq,void * priv)185 static int prism2_wep_set_key(void *key, int len, u8 *seq, void *priv)
186 {
187 struct prism2_wep_data *wep = priv;
188
189 if (len < 0 || len > WEP_KEY_LEN)
190 return -1;
191
192 memcpy(wep->key, key, len);
193 wep->key_len = len;
194
195 return 0;
196 }
197
198
prism2_wep_get_key(void * key,int len,u8 * seq,void * priv)199 static int prism2_wep_get_key(void *key, int len, u8 *seq, void *priv)
200 {
201 struct prism2_wep_data *wep = priv;
202
203 if (len < wep->key_len)
204 return -1;
205
206 memcpy(key, wep->key, wep->key_len);
207
208 return wep->key_len;
209 }
210
211
prism2_wep_print_stats(char * p,void * priv)212 static char *prism2_wep_print_stats(char *p, void *priv)
213 {
214 struct prism2_wep_data *wep = priv;
215
216 p += sprintf(p, "key[%d] alg=WEP len=%d\n",
217 wep->key_idx, wep->key_len);
218 return p;
219 }
220
221
222 static struct ieee80211_crypto_ops ieee80211_crypt_wep = {
223 .name = "WEP",
224 .init = prism2_wep_init,
225 .deinit = prism2_wep_deinit,
226 .encrypt_mpdu = prism2_wep_encrypt,
227 .decrypt_mpdu = prism2_wep_decrypt,
228 .encrypt_msdu = NULL,
229 .decrypt_msdu = NULL,
230 .set_key = prism2_wep_set_key,
231 .get_key = prism2_wep_get_key,
232 .print_stats = prism2_wep_print_stats,
233 .extra_prefix_len = 4, /* IV */
234 .extra_postfix_len = 4, /* ICV */
235 .owner = THIS_MODULE,
236 };
237
ieee80211_crypto_wep_init(void)238 int __init ieee80211_crypto_wep_init(void)
239 {
240 return ieee80211_register_crypto_ops(&ieee80211_crypt_wep);
241 }
242
ieee80211_crypto_wep_exit(void)243 void __exit ieee80211_crypto_wep_exit(void)
244 {
245 ieee80211_unregister_crypto_ops(&ieee80211_crypt_wep);
246 }
247
248
