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21042e41 | 1 | // SPDX-License-Identifier: GPL-2.0-only |
b453872c | 2 | /* |
274bfb8d | 3 | * lib80211 crypt: host-based WEP encryption implementation for lib80211 |
b453872c | 4 | * |
85d32e7b | 5 | * Copyright (c) 2002-2004, Jouni Malinen <j@w1.fi> |
274bfb8d | 6 | * Copyright (c) 2008, John W. Linville <linville@tuxdriver.com> |
b453872c JG |
7 | */ |
8 | ||
f12cc209 | 9 | #include <linux/err.h> |
af1f3d32 | 10 | #include <linux/fips.h> |
b453872c JG |
11 | #include <linux/module.h> |
12 | #include <linux/init.h> | |
13 | #include <linux/slab.h> | |
14 | #include <linux/random.h> | |
11763609 | 15 | #include <linux/scatterlist.h> |
b453872c | 16 | #include <linux/skbuff.h> |
d7fe0f24 | 17 | #include <linux/mm.h> |
b453872c JG |
18 | #include <asm/string.h> |
19 | ||
274bfb8d | 20 | #include <net/lib80211.h> |
b453872c | 21 | |
af1f3d32 | 22 | #include <crypto/arc4.h> |
b453872c JG |
23 | #include <linux/crc32.h> |
24 | ||
25 | MODULE_AUTHOR("Jouni Malinen"); | |
274bfb8d | 26 | MODULE_DESCRIPTION("lib80211 crypt: WEP"); |
b453872c JG |
27 | MODULE_LICENSE("GPL"); |
28 | ||
274bfb8d | 29 | struct lib80211_wep_data { |
b453872c JG |
30 | u32 iv; |
31 | #define WEP_KEY_LEN 13 | |
32 | u8 key[WEP_KEY_LEN + 1]; | |
33 | u8 key_len; | |
34 | u8 key_idx; | |
af1f3d32 AB |
35 | struct arc4_ctx tx_ctx; |
36 | struct arc4_ctx rx_ctx; | |
b453872c JG |
37 | }; |
38 | ||
274bfb8d | 39 | static void *lib80211_wep_init(int keyidx) |
b453872c | 40 | { |
274bfb8d | 41 | struct lib80211_wep_data *priv; |
b453872c | 42 | |
af1f3d32 AB |
43 | if (fips_enabled) |
44 | return NULL; | |
45 | ||
0da974f4 | 46 | priv = kzalloc(sizeof(*priv), GFP_ATOMIC); |
b453872c | 47 | if (priv == NULL) |
af1f3d32 | 48 | return NULL; |
b453872c JG |
49 | priv->key_idx = keyidx; |
50 | ||
b453872c JG |
51 | /* start WEP IV from a random value */ |
52 | get_random_bytes(&priv->iv, 4); | |
53 | ||
54 | return priv; | |
b453872c JG |
55 | } |
56 | ||
274bfb8d | 57 | static void lib80211_wep_deinit(void *priv) |
b453872c | 58 | { |
453431a5 | 59 | kfree_sensitive(priv); |
b453872c JG |
60 | } |
61 | ||
a4bf26f3 | 62 | /* Add WEP IV/key info to a frame that has at least 4 bytes of headroom */ |
274bfb8d | 63 | static int lib80211_wep_build_iv(struct sk_buff *skb, int hdr_len, |
9184d934 | 64 | u8 *key, int keylen, void *priv) |
b453872c | 65 | { |
274bfb8d | 66 | struct lib80211_wep_data *wep = priv; |
6572e91d | 67 | u32 klen; |
a4bf26f3 | 68 | u8 *pos; |
64265651 | 69 | |
a4bf26f3 | 70 | if (skb_headroom(skb) < 4 || skb->len < hdr_len) |
b453872c JG |
71 | return -1; |
72 | ||
b453872c JG |
73 | pos = skb_push(skb, 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 */ | |
a4bf26f3 JB |
91 | *pos++ = (wep->iv >> 16) & 0xff; |
92 | *pos++ = (wep->iv >> 8) & 0xff; | |
93 | *pos++ = wep->iv & 0xff; | |
b453872c JG |
94 | *pos++ = wep->key_idx << 6; |
95 | ||
a4bf26f3 JB |
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 | */ | |
274bfb8d | 105 | static int lib80211_wep_encrypt(struct sk_buff *skb, int hdr_len, void *priv) |
a4bf26f3 | 106 | { |
274bfb8d | 107 | struct lib80211_wep_data *wep = priv; |
a4bf26f3 JB |
108 | u32 crc, klen, len; |
109 | u8 *pos, *icv; | |
a4bf26f3 JB |
110 | u8 key[WEP_KEY_LEN + 3]; |
111 | ||
274bfb8d | 112 | /* other checks are in lib80211_wep_build_iv */ |
a4bf26f3 JB |
113 | if (skb_tailroom(skb) < 4) |
114 | return -1; | |
64265651 | 115 | |
a4bf26f3 | 116 | /* add the IV to the frame */ |
274bfb8d | 117 | if (lib80211_wep_build_iv(skb, hdr_len, NULL, 0, priv)) |
a4bf26f3 | 118 | return -1; |
64265651 | 119 | |
a4bf26f3 | 120 | /* Copy the IV into the first 3 bytes of the key */ |
d626f62b | 121 | skb_copy_from_linear_data_offset(skb, hdr_len, key, 3); |
a4bf26f3 | 122 | |
b453872c JG |
123 | /* Copy rest of the WEP key (the secret part) */ |
124 | memcpy(key + 3, wep->key, wep->key_len); | |
64265651 | 125 | |
a4bf26f3 JB |
126 | len = skb->len - hdr_len - 4; |
127 | pos = skb->data + hdr_len + 4; | |
128 | klen = 3 + wep->key_len; | |
b453872c | 129 | |
a4bf26f3 | 130 | /* Append little-endian CRC32 over only the data and encrypt it to produce ICV */ |
b453872c JG |
131 | crc = ~crc32_le(~0, pos, len); |
132 | icv = skb_put(skb, 4); | |
133 | icv[0] = crc; | |
134 | icv[1] = crc >> 8; | |
135 | icv[2] = crc >> 16; | |
136 | icv[3] = crc >> 24; | |
137 | ||
af1f3d32 AB |
138 | arc4_setkey(&wep->tx_ctx, key, klen); |
139 | arc4_crypt(&wep->tx_ctx, pos, pos, len + 4); | |
b802a5d6 JB |
140 | |
141 | return 0; | |
b453872c JG |
142 | } |
143 | ||
b453872c JG |
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 | */ | |
274bfb8d | 151 | static int lib80211_wep_decrypt(struct sk_buff *skb, int hdr_len, void *priv) |
b453872c | 152 | { |
274bfb8d | 153 | struct lib80211_wep_data *wep = priv; |
b453872c JG |
154 | u32 crc, klen, plen; |
155 | u8 key[WEP_KEY_LEN + 3]; | |
156 | u8 keyidx, *pos, icv[4]; | |
b453872c JG |
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 | ||
af1f3d32 AB |
177 | arc4_setkey(&wep->rx_ctx, key, klen); |
178 | arc4_crypt(&wep->rx_ctx, pos, pos, plen + 4); | |
b453872c JG |
179 | |
180 | crc = ~crc32_le(~0, pos, plen); | |
181 | icv[0] = crc; | |
182 | icv[1] = crc >> 8; | |
183 | icv[2] = crc >> 16; | |
184 | icv[3] = crc >> 24; | |
185 | if (memcmp(icv, pos + plen, 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, 4); | |
193 | skb_trim(skb, skb->len - 4); | |
194 | ||
195 | return 0; | |
196 | } | |
197 | ||
274bfb8d | 198 | static int lib80211_wep_set_key(void *key, int len, u8 * seq, void *priv) |
b453872c | 199 | { |
274bfb8d | 200 | struct lib80211_wep_data *wep = priv; |
b453872c JG |
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 | ||
274bfb8d | 211 | static int lib80211_wep_get_key(void *key, int len, u8 * seq, void *priv) |
b453872c | 212 | { |
274bfb8d | 213 | struct lib80211_wep_data *wep = priv; |
b453872c JG |
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 | ||
6bbefe86 | 223 | static void lib80211_wep_print_stats(struct seq_file *m, void *priv) |
b453872c | 224 | { |
274bfb8d | 225 | struct lib80211_wep_data *wep = priv; |
6bbefe86 | 226 | seq_printf(m, "key[%d] alg=WEP len=%d\n", wep->key_idx, wep->key_len); |
b453872c JG |
227 | } |
228 | ||
274bfb8d | 229 | static struct lib80211_crypto_ops lib80211_crypt_wep = { |
74079fdc | 230 | .name = "WEP", |
274bfb8d JL |
231 | .init = lib80211_wep_init, |
232 | .deinit = lib80211_wep_deinit, | |
274bfb8d JL |
233 | .encrypt_mpdu = lib80211_wep_encrypt, |
234 | .decrypt_mpdu = lib80211_wep_decrypt, | |
74079fdc JK |
235 | .encrypt_msdu = NULL, |
236 | .decrypt_msdu = NULL, | |
274bfb8d JL |
237 | .set_key = lib80211_wep_set_key, |
238 | .get_key = lib80211_wep_get_key, | |
239 | .print_stats = lib80211_wep_print_stats, | |
1264fc04 JK |
240 | .extra_mpdu_prefix_len = 4, /* IV */ |
241 | .extra_mpdu_postfix_len = 4, /* ICV */ | |
74079fdc | 242 | .owner = THIS_MODULE, |
b453872c JG |
243 | }; |
244 | ||
274bfb8d | 245 | static int __init lib80211_crypto_wep_init(void) |
b453872c | 246 | { |
274bfb8d | 247 | return lib80211_register_crypto_ops(&lib80211_crypt_wep); |
b453872c JG |
248 | } |
249 | ||
274bfb8d | 250 | static void __exit lib80211_crypto_wep_exit(void) |
b453872c | 251 | { |
274bfb8d | 252 | lib80211_unregister_crypto_ops(&lib80211_crypt_wep); |
b453872c JG |
253 | } |
254 | ||
274bfb8d JL |
255 | module_init(lib80211_crypto_wep_init); |
256 | module_exit(lib80211_crypto_wep_exit); |