1 | // SPDX-License-Identifier: GPL-2.0-only |
2 | /* |
3 | * lib80211 crypt: host-based WEP encryption implementation for lib80211 |
4 | * |
5 | * Copyright (c) 2002-2004, Jouni Malinen <j@w1.fi> |
6 | * Copyright (c) 2008, John W. Linville <linville@tuxdriver.com> |
7 | */ |
8 | |
9 | #include <linux/err.h> |
10 | #include <linux/fips.h> |
11 | #include <linux/module.h> |
12 | #include <linux/init.h> |
13 | #include <linux/slab.h> |
14 | #include <linux/random.h> |
15 | #include <linux/scatterlist.h> |
16 | #include <linux/skbuff.h> |
17 | #include <linux/mm.h> |
18 | #include <asm/string.h> |
19 | |
20 | #include <net/lib80211.h> |
21 | |
22 | #include <crypto/arc4.h> |
23 | #include <linux/crc32.h> |
24 | |
25 | MODULE_AUTHOR("Jouni Malinen" ); |
26 | MODULE_DESCRIPTION("lib80211 crypt: WEP" ); |
27 | MODULE_LICENSE("GPL" ); |
28 | |
29 | struct lib80211_wep_data { |
30 | u32 iv; |
31 | #define WEP_KEY_LEN 13 |
32 | u8 key[WEP_KEY_LEN + 1]; |
33 | u8 key_len; |
34 | u8 key_idx; |
35 | struct arc4_ctx tx_ctx; |
36 | struct arc4_ctx rx_ctx; |
37 | }; |
38 | |
39 | static void *lib80211_wep_init(int keyidx) |
40 | { |
41 | struct lib80211_wep_data *priv; |
42 | |
43 | if (fips_enabled) |
44 | return NULL; |
45 | |
46 | priv = kzalloc(size: sizeof(*priv), GFP_ATOMIC); |
47 | if (priv == NULL) |
48 | return NULL; |
49 | priv->key_idx = keyidx; |
50 | |
51 | /* start WEP IV from a random value */ |
52 | get_random_bytes(buf: &priv->iv, len: 4); |
53 | |
54 | return priv; |
55 | } |
56 | |
57 | static void lib80211_wep_deinit(void *priv) |
58 | { |
59 | kfree_sensitive(objp: priv); |
60 | } |
61 | |
62 | /* Add WEP IV/key info to a frame that has at least 4 bytes of headroom */ |
63 | static int lib80211_wep_build_iv(struct sk_buff *skb, int hdr_len, |
64 | u8 *key, int keylen, void *priv) |
65 | { |
66 | struct lib80211_wep_data *wep = priv; |
67 | u32 klen; |
68 | u8 *pos; |
69 | |
70 | if (skb_headroom(skb) < 4 || skb->len < hdr_len) |
71 | return -1; |
72 | |
73 | pos = skb_push(skb, len: 4); |
74 | memmove(pos, pos + 4, hdr_len); |
75 | pos += hdr_len; |
76 | |
77 | klen = 3 + wep->key_len; |
78 | |
79 | wep->iv++; |
80 | |
81 | /* Fluhrer, Mantin, and Shamir have reported weaknesses in the key |
82 | * scheduling algorithm of RC4. At least IVs (KeyByte + 3, 0xff, N) |
83 | * can be used to speedup attacks, so avoid using them. */ |
84 | if ((wep->iv & 0xff00) == 0xff00) { |
85 | u8 B = (wep->iv >> 16) & 0xff; |
86 | if (B >= 3 && B < klen) |
87 | wep->iv += 0x0100; |
88 | } |
89 | |
90 | /* Prepend 24-bit IV to RC4 key and TX frame */ |
91 | *pos++ = (wep->iv >> 16) & 0xff; |
92 | *pos++ = (wep->iv >> 8) & 0xff; |
93 | *pos++ = wep->iv & 0xff; |
94 | *pos++ = wep->key_idx << 6; |
95 | |
96 | return 0; |
97 | } |
98 | |
99 | /* Perform WEP encryption on given skb that has at least 4 bytes of headroom |
100 | * for IV and 4 bytes of tailroom for ICV. Both IV and ICV will be transmitted, |
101 | * so the payload length increases with 8 bytes. |
102 | * |
103 | * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data)) |
104 | */ |
105 | static int lib80211_wep_encrypt(struct sk_buff *skb, int hdr_len, void *priv) |
106 | { |
107 | struct lib80211_wep_data *wep = priv; |
108 | u32 crc, klen, len; |
109 | u8 *pos, *icv; |
110 | u8 key[WEP_KEY_LEN + 3]; |
111 | |
112 | /* other checks are in lib80211_wep_build_iv */ |
113 | if (skb_tailroom(skb) < 4) |
114 | return -1; |
115 | |
116 | /* add the IV to the frame */ |
117 | if (lib80211_wep_build_iv(skb, hdr_len, NULL, keylen: 0, priv)) |
118 | return -1; |
119 | |
120 | /* Copy the IV into the first 3 bytes of the key */ |
121 | skb_copy_from_linear_data_offset(skb, offset: hdr_len, to: key, len: 3); |
122 | |
123 | /* Copy rest of the WEP key (the secret part) */ |
124 | memcpy(key + 3, wep->key, wep->key_len); |
125 | |
126 | len = skb->len - hdr_len - 4; |
127 | pos = skb->data + hdr_len + 4; |
128 | klen = 3 + wep->key_len; |
129 | |
130 | /* Append little-endian CRC32 over only the data and encrypt it to produce ICV */ |
131 | crc = ~crc32_le(crc: ~0, p: pos, len); |
132 | icv = skb_put(skb, len: 4); |
133 | icv[0] = crc; |
134 | icv[1] = crc >> 8; |
135 | icv[2] = crc >> 16; |
136 | icv[3] = crc >> 24; |
137 | |
138 | arc4_setkey(ctx: &wep->tx_ctx, in_key: key, key_len: klen); |
139 | arc4_crypt(ctx: &wep->tx_ctx, out: pos, in: pos, len: len + 4); |
140 | |
141 | return 0; |
142 | } |
143 | |
144 | /* Perform WEP decryption on given buffer. Buffer includes whole WEP part of |
145 | * the frame: IV (4 bytes), encrypted payload (including SNAP header), |
146 | * ICV (4 bytes). len includes both IV and ICV. |
147 | * |
148 | * Returns 0 if frame was decrypted successfully and ICV was correct and -1 on |
149 | * failure. If frame is OK, IV and ICV will be removed. |
150 | */ |
151 | static int lib80211_wep_decrypt(struct sk_buff *skb, int hdr_len, void *priv) |
152 | { |
153 | struct lib80211_wep_data *wep = priv; |
154 | u32 crc, klen, plen; |
155 | u8 key[WEP_KEY_LEN + 3]; |
156 | u8 keyidx, *pos, icv[4]; |
157 | |
158 | if (skb->len < hdr_len + 8) |
159 | return -1; |
160 | |
161 | pos = skb->data + hdr_len; |
162 | key[0] = *pos++; |
163 | key[1] = *pos++; |
164 | key[2] = *pos++; |
165 | keyidx = *pos++ >> 6; |
166 | if (keyidx != wep->key_idx) |
167 | return -1; |
168 | |
169 | klen = 3 + wep->key_len; |
170 | |
171 | /* Copy rest of the WEP key (the secret part) */ |
172 | memcpy(key + 3, wep->key, wep->key_len); |
173 | |
174 | /* Apply RC4 to data and compute CRC32 over decrypted data */ |
175 | plen = skb->len - hdr_len - 8; |
176 | |
177 | arc4_setkey(ctx: &wep->rx_ctx, in_key: key, key_len: klen); |
178 | arc4_crypt(ctx: &wep->rx_ctx, out: pos, in: pos, len: plen + 4); |
179 | |
180 | crc = ~crc32_le(crc: ~0, p: pos, len: plen); |
181 | icv[0] = crc; |
182 | icv[1] = crc >> 8; |
183 | icv[2] = crc >> 16; |
184 | icv[3] = crc >> 24; |
185 | if (memcmp(p: icv, q: pos + plen, size: 4) != 0) { |
186 | /* ICV mismatch - drop frame */ |
187 | return -2; |
188 | } |
189 | |
190 | /* Remove IV and ICV */ |
191 | memmove(skb->data + 4, skb->data, hdr_len); |
192 | skb_pull(skb, len: 4); |
193 | skb_trim(skb, len: skb->len - 4); |
194 | |
195 | return 0; |
196 | } |
197 | |
198 | static int lib80211_wep_set_key(void *key, int len, u8 * seq, void *priv) |
199 | { |
200 | struct lib80211_wep_data *wep = priv; |
201 | |
202 | if (len < 0 || len > WEP_KEY_LEN) |
203 | return -1; |
204 | |
205 | memcpy(wep->key, key, len); |
206 | wep->key_len = len; |
207 | |
208 | return 0; |
209 | } |
210 | |
211 | static int lib80211_wep_get_key(void *key, int len, u8 * seq, void *priv) |
212 | { |
213 | struct lib80211_wep_data *wep = priv; |
214 | |
215 | if (len < wep->key_len) |
216 | return -1; |
217 | |
218 | memcpy(key, wep->key, wep->key_len); |
219 | |
220 | return wep->key_len; |
221 | } |
222 | |
223 | static void lib80211_wep_print_stats(struct seq_file *m, void *priv) |
224 | { |
225 | struct lib80211_wep_data *wep = priv; |
226 | seq_printf(m, fmt: "key[%d] alg=WEP len=%d\n" , wep->key_idx, wep->key_len); |
227 | } |
228 | |
229 | static struct lib80211_crypto_ops lib80211_crypt_wep = { |
230 | .name = "WEP" , |
231 | .init = lib80211_wep_init, |
232 | .deinit = lib80211_wep_deinit, |
233 | .encrypt_mpdu = lib80211_wep_encrypt, |
234 | .decrypt_mpdu = lib80211_wep_decrypt, |
235 | .encrypt_msdu = NULL, |
236 | .decrypt_msdu = NULL, |
237 | .set_key = lib80211_wep_set_key, |
238 | .get_key = lib80211_wep_get_key, |
239 | .print_stats = lib80211_wep_print_stats, |
240 | .extra_mpdu_prefix_len = 4, /* IV */ |
241 | .extra_mpdu_postfix_len = 4, /* ICV */ |
242 | .owner = THIS_MODULE, |
243 | }; |
244 | |
245 | static int __init lib80211_crypto_wep_init(void) |
246 | { |
247 | return lib80211_register_crypto_ops(ops: &lib80211_crypt_wep); |
248 | } |
249 | |
250 | static void __exit lib80211_crypto_wep_exit(void) |
251 | { |
252 | lib80211_unregister_crypto_ops(ops: &lib80211_crypt_wep); |
253 | } |
254 | |
255 | module_init(lib80211_crypto_wep_init); |
256 | module_exit(lib80211_crypto_wep_exit); |
257 | |