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 0;
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 ieee80211_crypto_wep_exit(void)
244 {
245 	ieee80211_unregister_crypto_ops(&ieee80211_crypt_wep);
246 }
247 
248