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/module.h> 9 #include <linux/init.h> 10 #include <linux/slab.h> 11 #include <linux/random.h> 12 #include <linux/skbuff.h> 13 #include <linux/string.h> 14 15 #include "ieee80211.h" 16 17 #include <crypto/skcipher.h> 18 #include <linux/scatterlist.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 crypto_sync_skcipher *tx_tfm; 32 struct crypto_sync_skcipher *rx_tfm; 33 }; 34 35 36 static void *prism2_wep_init(int keyidx) 37 { 38 struct prism2_wep_data *priv; 39 40 priv = kzalloc(sizeof(*priv), GFP_KERNEL); 41 if (!priv) 42 return NULL; 43 priv->key_idx = keyidx; 44 45 priv->tx_tfm = crypto_alloc_sync_skcipher("ecb(arc4)", 0, 0); 46 if (IS_ERR(priv->tx_tfm)) 47 goto free_priv; 48 priv->rx_tfm = crypto_alloc_sync_skcipher("ecb(arc4)", 0, 0); 49 if (IS_ERR(priv->rx_tfm)) 50 goto free_tx; 51 52 /* start WEP IV from a random value */ 53 get_random_bytes(&priv->iv, 4); 54 55 return priv; 56 free_tx: 57 crypto_free_sync_skcipher(priv->tx_tfm); 58 free_priv: 59 kfree(priv); 60 return NULL; 61 } 62 63 64 static void prism2_wep_deinit(void *priv) 65 { 66 struct prism2_wep_data *_priv = priv; 67 68 if (_priv) { 69 crypto_free_sync_skcipher(_priv->tx_tfm); 70 crypto_free_sync_skcipher(_priv->rx_tfm); 71 } 72 kfree(priv); 73 } 74 75 /* Perform WEP encryption on given skb that has at least 4 bytes of headroom 76 * for IV and 4 bytes of tailroom for ICV. Both IV and ICV will be transmitted, 77 * so the payload length increases with 8 bytes. 78 * 79 * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data)) 80 */ 81 static int prism2_wep_encrypt(struct sk_buff *skb, int hdr_len, void *priv) 82 { 83 struct prism2_wep_data *wep = priv; 84 u32 klen, len; 85 u8 key[WEP_KEY_LEN + 3]; 86 u8 *pos; 87 struct cb_desc *tcb_desc = (struct cb_desc *)(skb->cb + MAX_DEV_ADDR_SIZE); 88 u32 crc; 89 u8 *icv; 90 struct scatterlist sg; 91 int err; 92 93 if (skb_headroom(skb) < 4 || skb_tailroom(skb) < 4 || 94 skb->len < hdr_len) 95 return -1; 96 97 len = skb->len - hdr_len; 98 pos = skb_push(skb, 4); 99 memmove(pos, pos + 4, hdr_len); 100 pos += hdr_len; 101 102 klen = 3 + wep->key_len; 103 104 wep->iv++; 105 106 /* Fluhrer, Mantin, and Shamir have reported weaknesses in the key 107 * scheduling algorithm of RC4. At least IVs (KeyByte + 3, 0xff, N) 108 * can be used to speedup attacks, so avoid using them. 109 */ 110 if ((wep->iv & 0xff00) == 0xff00) { 111 u8 B = (wep->iv >> 16) & 0xff; 112 113 if (B >= 3 && B < klen) 114 wep->iv += 0x0100; 115 } 116 117 /* Prepend 24-bit IV to RC4 key and TX frame */ 118 *pos++ = key[0] = (wep->iv >> 16) & 0xff; 119 *pos++ = key[1] = (wep->iv >> 8) & 0xff; 120 *pos++ = key[2] = wep->iv & 0xff; 121 *pos++ = wep->key_idx << 6; 122 123 /* Copy rest of the WEP key (the secret part) */ 124 memcpy(key + 3, wep->key, wep->key_len); 125 126 if (!tcb_desc->bHwSec) { 127 SYNC_SKCIPHER_REQUEST_ON_STACK(req, wep->tx_tfm); 128 129 /* Append little-endian CRC32 and encrypt it to produce ICV */ 130 crc = ~crc32_le(~0, pos, len); 131 icv = skb_put(skb, 4); 132 icv[0] = crc; 133 icv[1] = crc >> 8; 134 icv[2] = crc >> 16; 135 icv[3] = crc >> 24; 136 137 crypto_sync_skcipher_setkey(wep->tx_tfm, key, klen); 138 sg_init_one(&sg, pos, len+4); 139 140 skcipher_request_set_sync_tfm(req, wep->tx_tfm); 141 skcipher_request_set_callback(req, 0, NULL, NULL); 142 skcipher_request_set_crypt(req, &sg, &sg, len + 4, NULL); 143 144 err = crypto_skcipher_encrypt(req); 145 skcipher_request_zero(req); 146 return err; 147 } 148 149 return 0; 150 } 151 152 153 /* Perform WEP decryption on given buffer. Buffer includes whole WEP part of 154 * the frame: IV (4 bytes), encrypted payload (including SNAP header), 155 * ICV (4 bytes). len includes both IV and ICV. 156 * 157 * Returns 0 if frame was decrypted successfully and ICV was correct and -1 on 158 * failure. If frame is OK, IV and ICV will be removed. 159 */ 160 static int prism2_wep_decrypt(struct sk_buff *skb, int hdr_len, void *priv) 161 { 162 struct prism2_wep_data *wep = priv; 163 u32 klen, plen; 164 u8 key[WEP_KEY_LEN + 3]; 165 u8 keyidx, *pos; 166 struct cb_desc *tcb_desc = (struct cb_desc *)(skb->cb + MAX_DEV_ADDR_SIZE); 167 u32 crc; 168 u8 icv[4]; 169 struct scatterlist sg; 170 int err; 171 172 if (skb->len < hdr_len + 8) 173 return -1; 174 175 pos = skb->data + hdr_len; 176 key[0] = *pos++; 177 key[1] = *pos++; 178 key[2] = *pos++; 179 keyidx = *pos++ >> 6; 180 if (keyidx != wep->key_idx) 181 return -1; 182 183 klen = 3 + wep->key_len; 184 185 /* Copy rest of the WEP key (the secret part) */ 186 memcpy(key + 3, wep->key, wep->key_len); 187 188 /* Apply RC4 to data and compute CRC32 over decrypted data */ 189 plen = skb->len - hdr_len - 8; 190 191 if (!tcb_desc->bHwSec) { 192 SYNC_SKCIPHER_REQUEST_ON_STACK(req, wep->rx_tfm); 193 194 crypto_sync_skcipher_setkey(wep->rx_tfm, key, klen); 195 sg_init_one(&sg, pos, plen+4); 196 197 skcipher_request_set_sync_tfm(req, wep->rx_tfm); 198 skcipher_request_set_callback(req, 0, NULL, NULL); 199 skcipher_request_set_crypt(req, &sg, &sg, plen + 4, NULL); 200 201 err = crypto_skcipher_decrypt(req); 202 skcipher_request_zero(req); 203 if (err) 204 return -7; 205 206 crc = ~crc32_le(~0, pos, plen); 207 icv[0] = crc; 208 icv[1] = crc >> 8; 209 icv[2] = crc >> 16; 210 icv[3] = crc >> 24; 211 if (memcmp(icv, pos + plen, 4) != 0) { 212 /* ICV mismatch - drop frame */ 213 return -2; 214 } 215 } 216 /* Remove IV and ICV */ 217 memmove(skb->data + 4, skb->data, hdr_len); 218 skb_pull(skb, 4); 219 skb_trim(skb, skb->len - 4); 220 221 return 0; 222 } 223 224 225 static int prism2_wep_set_key(void *key, int len, u8 *seq, void *priv) 226 { 227 struct prism2_wep_data *wep = priv; 228 229 if (len < 0 || len > WEP_KEY_LEN) 230 return -1; 231 232 memcpy(wep->key, key, len); 233 wep->key_len = len; 234 235 return 0; 236 } 237 238 239 static int prism2_wep_get_key(void *key, int len, u8 *seq, void *priv) 240 { 241 struct prism2_wep_data *wep = priv; 242 243 if (len < wep->key_len) 244 return -1; 245 246 memcpy(key, wep->key, wep->key_len); 247 248 return wep->key_len; 249 } 250 251 252 static char *prism2_wep_print_stats(char *p, void *priv) 253 { 254 struct prism2_wep_data *wep = priv; 255 256 p += sprintf(p, "key[%d] alg=WEP len=%d\n", 257 wep->key_idx, wep->key_len); 258 return p; 259 } 260 261 262 static struct ieee80211_crypto_ops ieee80211_crypt_wep = { 263 .name = "WEP", 264 .init = prism2_wep_init, 265 .deinit = prism2_wep_deinit, 266 .encrypt_mpdu = prism2_wep_encrypt, 267 .decrypt_mpdu = prism2_wep_decrypt, 268 .encrypt_msdu = NULL, 269 .decrypt_msdu = NULL, 270 .set_key = prism2_wep_set_key, 271 .get_key = prism2_wep_get_key, 272 .print_stats = prism2_wep_print_stats, 273 .extra_prefix_len = 4, /* IV */ 274 .extra_postfix_len = 4, /* ICV */ 275 .owner = THIS_MODULE, 276 }; 277 278 int __init ieee80211_crypto_wep_init(void) 279 { 280 return ieee80211_register_crypto_ops(&ieee80211_crypt_wep); 281 } 282 283 void __exit ieee80211_crypto_wep_exit(void) 284 { 285 ieee80211_unregister_crypto_ops(&ieee80211_crypt_wep); 286 } 287 288