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 <crypto/arc4.h>
9 #include <linux/fips.h>
10 #include <linux/module.h>
11 #include <linux/init.h>
12 #include <linux/slab.h>
13 #include <linux/random.h>
14 #include <linux/skbuff.h>
15 #include <linux/string.h>
16 #include "rtllib.h"
17
18 #include <linux/crc32.h>
19
20 struct prism2_wep_data {
21 u32 iv;
22 #define WEP_KEY_LEN 13
23 u8 key[WEP_KEY_LEN + 1];
24 u8 key_len;
25 u8 key_idx;
26 struct arc4_ctx rx_ctx_arc4;
27 struct arc4_ctx tx_ctx_arc4;
28 };
29
prism2_wep_init(int keyidx)30 static void *prism2_wep_init(int keyidx)
31 {
32 struct prism2_wep_data *priv;
33
34 if (fips_enabled)
35 return NULL;
36
37 priv = kzalloc(sizeof(*priv), GFP_ATOMIC);
38 if (priv == NULL)
39 return NULL;
40 priv->key_idx = keyidx;
41
42 /* start WEP IV from a random value */
43 get_random_bytes(&priv->iv, 4);
44
45 return priv;
46 }
47
prism2_wep_deinit(void * priv)48 static void prism2_wep_deinit(void *priv)
49 {
50 kfree_sensitive(priv);
51 }
52
53 /* Perform WEP encryption on given skb that has at least 4 bytes of headroom
54 * for IV and 4 bytes of tailroom for ICV. Both IV and ICV will be transmitted,
55 * so the payload length increases with 8 bytes.
56 *
57 * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data))
58 */
prism2_wep_encrypt(struct sk_buff * skb,int hdr_len,void * priv)59 static int prism2_wep_encrypt(struct sk_buff *skb, int hdr_len, void *priv)
60 {
61 struct prism2_wep_data *wep = priv;
62 u32 klen, len;
63 u8 key[WEP_KEY_LEN + 3];
64 u8 *pos;
65 struct cb_desc *tcb_desc = (struct cb_desc *)(skb->cb +
66 MAX_DEV_ADDR_SIZE);
67 u32 crc;
68 u8 *icv;
69
70 if (skb_headroom(skb) < 4 || skb_tailroom(skb) < 4 ||
71 skb->len < hdr_len){
72 pr_err("Error!!! headroom=%d tailroom=%d skblen=%d hdr_len=%d\n",
73 skb_headroom(skb), skb_tailroom(skb), skb->len, hdr_len);
74 return -1;
75 }
76 len = skb->len - hdr_len;
77 pos = skb_push(skb, 4);
78 memmove(pos, pos + 4, hdr_len);
79 pos += hdr_len;
80
81 klen = 3 + wep->key_len;
82
83 wep->iv++;
84
85 /* Fluhrer, Mantin, and Shamir have reported weaknesses in the key
86 * scheduling algorithm of RC4. At least IVs (KeyByte + 3, 0xff, N)
87 * can be used to speedup attacks, so avoid using them.
88 */
89 if ((wep->iv & 0xff00) == 0xff00) {
90 u8 B = (wep->iv >> 16) & 0xff;
91
92 if (B >= 3 && B < klen)
93 wep->iv += 0x0100;
94 }
95
96 /* Prepend 24-bit IV to RC4 key and TX frame */
97 *pos++ = key[0] = (wep->iv >> 16) & 0xff;
98 *pos++ = key[1] = (wep->iv >> 8) & 0xff;
99 *pos++ = key[2] = wep->iv & 0xff;
100 *pos++ = wep->key_idx << 6;
101
102 /* Copy rest of the WEP key (the secret part) */
103 memcpy(key + 3, wep->key, wep->key_len);
104
105 if (!tcb_desc->bHwSec) {
106 /* Append little-endian CRC32 and encrypt it to produce ICV */
107 crc = ~crc32_le(~0, pos, len);
108 icv = skb_put(skb, 4);
109 icv[0] = crc;
110 icv[1] = crc >> 8;
111 icv[2] = crc >> 16;
112 icv[3] = crc >> 24;
113
114 arc4_setkey(&wep->tx_ctx_arc4, key, klen);
115 arc4_crypt(&wep->tx_ctx_arc4, pos, pos, len + 4);
116 }
117
118 return 0;
119 }
120
121 /* Perform WEP decryption on given struct buffer. Buffer includes whole WEP
122 * part of the frame: IV (4 bytes), encrypted payload (including SNAP header),
123 * ICV (4 bytes). len includes both IV and ICV.
124 *
125 * Returns 0 if frame was decrypted successfully and ICV was correct and -1 on
126 * failure. If frame is OK, IV and ICV will be removed.
127 */
prism2_wep_decrypt(struct sk_buff * skb,int hdr_len,void * priv)128 static int prism2_wep_decrypt(struct sk_buff *skb, int hdr_len, void *priv)
129 {
130 struct prism2_wep_data *wep = priv;
131 u32 klen, plen;
132 u8 key[WEP_KEY_LEN + 3];
133 u8 keyidx, *pos;
134 struct cb_desc *tcb_desc = (struct cb_desc *)(skb->cb +
135 MAX_DEV_ADDR_SIZE);
136 u32 crc;
137 u8 icv[4];
138
139 if (skb->len < hdr_len + 8)
140 return -1;
141
142 pos = skb->data + hdr_len;
143 key[0] = *pos++;
144 key[1] = *pos++;
145 key[2] = *pos++;
146 keyidx = *pos++ >> 6;
147 if (keyidx != wep->key_idx)
148 return -1;
149
150 klen = 3 + wep->key_len;
151
152 /* Copy rest of the WEP key (the secret part) */
153 memcpy(key + 3, wep->key, wep->key_len);
154
155 /* Apply RC4 to data and compute CRC32 over decrypted data */
156 plen = skb->len - hdr_len - 8;
157
158 if (!tcb_desc->bHwSec) {
159 arc4_setkey(&wep->rx_ctx_arc4, key, klen);
160 arc4_crypt(&wep->rx_ctx_arc4, pos, pos, plen + 4);
161
162 crc = ~crc32_le(~0, pos, plen);
163 icv[0] = crc;
164 icv[1] = crc >> 8;
165 icv[2] = crc >> 16;
166 icv[3] = crc >> 24;
167 if (memcmp(icv, pos + plen, 4) != 0) {
168 /* ICV mismatch - drop frame */
169 return -2;
170 }
171 }
172 /* Remove IV and ICV */
173 memmove(skb->data + 4, skb->data, hdr_len);
174 skb_pull(skb, 4);
175 skb_trim(skb, skb->len - 4);
176
177 return 0;
178 }
179
prism2_wep_set_key(void * key,int len,u8 * seq,void * priv)180 static int prism2_wep_set_key(void *key, int len, u8 *seq, void *priv)
181 {
182 struct prism2_wep_data *wep = priv;
183
184 if (len < 0 || len > WEP_KEY_LEN)
185 return -1;
186
187 memcpy(wep->key, key, len);
188 wep->key_len = len;
189
190 return 0;
191 }
192
prism2_wep_get_key(void * key,int len,u8 * seq,void * priv)193 static int prism2_wep_get_key(void *key, int len, u8 *seq, void *priv)
194 {
195 struct prism2_wep_data *wep = priv;
196
197 if (len < wep->key_len)
198 return -1;
199
200 memcpy(key, wep->key, wep->key_len);
201
202 return wep->key_len;
203 }
204
prism2_wep_print_stats(struct seq_file * m,void * priv)205 static void prism2_wep_print_stats(struct seq_file *m, void *priv)
206 {
207 struct prism2_wep_data *wep = priv;
208
209 seq_printf(m, "key[%d] alg=WEP len=%d\n", wep->key_idx, wep->key_len);
210 }
211
212 static struct lib80211_crypto_ops rtllib_crypt_wep = {
213 .name = "R-WEP",
214 .init = prism2_wep_init,
215 .deinit = prism2_wep_deinit,
216 .encrypt_mpdu = prism2_wep_encrypt,
217 .decrypt_mpdu = prism2_wep_decrypt,
218 .encrypt_msdu = NULL,
219 .decrypt_msdu = NULL,
220 .set_key = prism2_wep_set_key,
221 .get_key = prism2_wep_get_key,
222 .print_stats = prism2_wep_print_stats,
223 .extra_mpdu_prefix_len = 4, /* IV */
224 .extra_mpdu_postfix_len = 4, /* ICV */
225 .owner = THIS_MODULE,
226 };
227
rtllib_crypto_wep_init(void)228 static int __init rtllib_crypto_wep_init(void)
229 {
230 return lib80211_register_crypto_ops(&rtllib_crypt_wep);
231 }
232
rtllib_crypto_wep_exit(void)233 static void __exit rtllib_crypto_wep_exit(void)
234 {
235 lib80211_unregister_crypto_ops(&rtllib_crypt_wep);
236 }
237
238 module_init(rtllib_crypto_wep_init);
239 module_exit(rtllib_crypto_wep_exit);
240
241 MODULE_LICENSE("GPL");
242