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 | |
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(size: sizeof(*priv), GFP_ATOMIC); |
38 | if (!priv) |
39 | return NULL; |
40 | priv->key_idx = keyidx; |
41 | |
42 | /* start WEP IV from a random value */ |
43 | get_random_bytes(buf: &priv->iv, len: 4); |
44 | |
45 | return priv; |
46 | } |
47 | |
48 | static void prism2_wep_deinit(void *priv) |
49 | { |
50 | kfree_sensitive(objp: 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 | */ |
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, len: 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(crc: ~0, p: pos, len); |
108 | icv = skb_put(skb, len: 4); |
109 | icv[0] = crc; |
110 | icv[1] = crc >> 8; |
111 | icv[2] = crc >> 16; |
112 | icv[3] = crc >> 24; |
113 | |
114 | arc4_setkey(ctx: &wep->tx_ctx_arc4, in_key: key, key_len: klen); |
115 | arc4_crypt(ctx: &wep->tx_ctx_arc4, out: pos, in: pos, len: 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 | */ |
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(ctx: &wep->rx_ctx_arc4, in_key: key, key_len: klen); |
160 | arc4_crypt(ctx: &wep->rx_ctx_arc4, out: pos, in: pos, len: plen + 4); |
161 | |
162 | crc = ~crc32_le(crc: ~0, p: pos, len: plen); |
163 | icv[0] = crc; |
164 | icv[1] = crc >> 8; |
165 | icv[2] = crc >> 16; |
166 | icv[3] = crc >> 24; |
167 | if (memcmp(p: icv, q: pos + plen, size: 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, len: 4); |
175 | skb_trim(skb, len: skb->len - 4); |
176 | |
177 | return 0; |
178 | } |
179 | |
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 | |
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 | |
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, fmt: "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 | |
228 | static int __init rtllib_crypto_wep_init(void) |
229 | { |
230 | return lib80211_register_crypto_ops(ops: &rtllib_crypt_wep); |
231 | } |
232 | |
233 | static void __exit rtllib_crypto_wep_exit(void) |
234 | { |
235 | lib80211_unregister_crypto_ops(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 | |