1 /* 2 * Host AP crypt: host-based WEP encryption implementation for Host AP driver 3 * 4 * Copyright (c) 2002-2004, Jouni Malinen <jkmaline@cc.hut.fi> 5 * 6 * This program is free software; you can redistribute it and/or modify 7 * it under the terms of the GNU General Public License version 2 as 8 * published by the Free Software Foundation. See README and COPYING for 9 * more details. 10 */ 11 12 #include <crypto/skcipher.h> 13 #include <linux/module.h> 14 #include <linux/init.h> 15 #include <linux/slab.h> 16 #include <linux/random.h> 17 #include <linux/skbuff.h> 18 #include <linux/string.h> 19 #include "rtllib.h" 20 21 #include <linux/scatterlist.h> 22 #include <linux/crc32.h> 23 24 struct prism2_wep_data { 25 u32 iv; 26 #define WEP_KEY_LEN 13 27 u8 key[WEP_KEY_LEN + 1]; 28 u8 key_len; 29 u8 key_idx; 30 struct crypto_skcipher *tx_tfm; 31 struct crypto_skcipher *rx_tfm; 32 }; 33 34 35 static void *prism2_wep_init(int keyidx) 36 { 37 struct prism2_wep_data *priv; 38 39 priv = kzalloc(sizeof(*priv), GFP_ATOMIC); 40 if (priv == NULL) 41 goto fail; 42 priv->key_idx = keyidx; 43 44 priv->tx_tfm = crypto_alloc_skcipher("ecb(arc4)", 0, CRYPTO_ALG_ASYNC); 45 if (IS_ERR(priv->tx_tfm)) { 46 pr_debug("rtllib_crypt_wep: could not allocate crypto API arc4\n"); 47 priv->tx_tfm = NULL; 48 goto fail; 49 } 50 priv->rx_tfm = crypto_alloc_skcipher("ecb(arc4)", 0, CRYPTO_ALG_ASYNC); 51 if (IS_ERR(priv->rx_tfm)) { 52 pr_debug("rtllib_crypt_wep: could not allocate crypto API arc4\n"); 53 priv->rx_tfm = NULL; 54 goto fail; 55 } 56 57 /* start WEP IV from a random value */ 58 get_random_bytes(&priv->iv, 4); 59 60 return priv; 61 62 fail: 63 if (priv) { 64 crypto_free_skcipher(priv->tx_tfm); 65 crypto_free_skcipher(priv->rx_tfm); 66 kfree(priv); 67 } 68 return NULL; 69 } 70 71 72 static void prism2_wep_deinit(void *priv) 73 { 74 struct prism2_wep_data *_priv = priv; 75 76 if (_priv) { 77 crypto_free_skcipher(_priv->tx_tfm); 78 crypto_free_skcipher(_priv->rx_tfm); 79 } 80 kfree(priv); 81 } 82 83 /* Perform WEP encryption on given skb that has at least 4 bytes of headroom 84 * for IV and 4 bytes of tailroom for ICV. Both IV and ICV will be transmitted, 85 * so the payload length increases with 8 bytes. 86 * 87 * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data)) 88 */ 89 static int prism2_wep_encrypt(struct sk_buff *skb, int hdr_len, void *priv) 90 { 91 struct prism2_wep_data *wep = priv; 92 u32 klen, len; 93 u8 key[WEP_KEY_LEN + 3]; 94 u8 *pos; 95 struct cb_desc *tcb_desc = (struct cb_desc *)(skb->cb + 96 MAX_DEV_ADDR_SIZE); 97 u32 crc; 98 u8 *icv; 99 struct scatterlist sg; 100 int err; 101 102 if (skb_headroom(skb) < 4 || skb_tailroom(skb) < 4 || 103 skb->len < hdr_len){ 104 pr_err("Error!!! headroom=%d tailroom=%d skblen=%d hdr_len=%d\n", 105 skb_headroom(skb), skb_tailroom(skb), skb->len, hdr_len); 106 return -1; 107 } 108 len = skb->len - hdr_len; 109 pos = skb_push(skb, 4); 110 memmove(pos, pos + 4, hdr_len); 111 pos += hdr_len; 112 113 klen = 3 + wep->key_len; 114 115 wep->iv++; 116 117 /* Fluhrer, Mantin, and Shamir have reported weaknesses in the key 118 * scheduling algorithm of RC4. At least IVs (KeyByte + 3, 0xff, N) 119 * can be used to speedup attacks, so avoid using them. 120 */ 121 if ((wep->iv & 0xff00) == 0xff00) { 122 u8 B = (wep->iv >> 16) & 0xff; 123 124 if (B >= 3 && B < klen) 125 wep->iv += 0x0100; 126 } 127 128 /* Prepend 24-bit IV to RC4 key and TX frame */ 129 *pos++ = key[0] = (wep->iv >> 16) & 0xff; 130 *pos++ = key[1] = (wep->iv >> 8) & 0xff; 131 *pos++ = key[2] = wep->iv & 0xff; 132 *pos++ = wep->key_idx << 6; 133 134 /* Copy rest of the WEP key (the secret part) */ 135 memcpy(key + 3, wep->key, wep->key_len); 136 137 if (!tcb_desc->bHwSec) { 138 SKCIPHER_REQUEST_ON_STACK(req, wep->tx_tfm); 139 140 /* Append little-endian CRC32 and encrypt it to produce ICV */ 141 crc = ~crc32_le(~0, pos, len); 142 icv = skb_put(skb, 4); 143 icv[0] = crc; 144 icv[1] = crc >> 8; 145 icv[2] = crc >> 16; 146 icv[3] = crc >> 24; 147 148 sg_init_one(&sg, pos, len+4); 149 crypto_skcipher_setkey(wep->tx_tfm, key, klen); 150 skcipher_request_set_tfm(req, wep->tx_tfm); 151 skcipher_request_set_callback(req, 0, NULL, NULL); 152 skcipher_request_set_crypt(req, &sg, &sg, len + 4, NULL); 153 err = crypto_skcipher_encrypt(req); 154 skcipher_request_zero(req); 155 return err; 156 } 157 158 return 0; 159 } 160 161 162 /* Perform WEP decryption on given struct buffer. Buffer includes whole WEP 163 * part of the frame: IV (4 bytes), encrypted payload (including SNAP header), 164 * ICV (4 bytes). len includes both IV and ICV. 165 * 166 * Returns 0 if frame was decrypted successfully and ICV was correct and -1 on 167 * failure. If frame is OK, IV and ICV will be removed. 168 */ 169 static int prism2_wep_decrypt(struct sk_buff *skb, int hdr_len, void *priv) 170 { 171 struct prism2_wep_data *wep = priv; 172 u32 klen, plen; 173 u8 key[WEP_KEY_LEN + 3]; 174 u8 keyidx, *pos; 175 struct cb_desc *tcb_desc = (struct cb_desc *)(skb->cb + 176 MAX_DEV_ADDR_SIZE); 177 u32 crc; 178 u8 icv[4]; 179 struct scatterlist sg; 180 int err; 181 182 if (skb->len < hdr_len + 8) 183 return -1; 184 185 pos = skb->data + hdr_len; 186 key[0] = *pos++; 187 key[1] = *pos++; 188 key[2] = *pos++; 189 keyidx = *pos++ >> 6; 190 if (keyidx != wep->key_idx) 191 return -1; 192 193 klen = 3 + wep->key_len; 194 195 /* Copy rest of the WEP key (the secret part) */ 196 memcpy(key + 3, wep->key, wep->key_len); 197 198 /* Apply RC4 to data and compute CRC32 over decrypted data */ 199 plen = skb->len - hdr_len - 8; 200 201 if (!tcb_desc->bHwSec) { 202 SKCIPHER_REQUEST_ON_STACK(req, wep->rx_tfm); 203 204 sg_init_one(&sg, pos, plen+4); 205 crypto_skcipher_setkey(wep->rx_tfm, key, klen); 206 skcipher_request_set_tfm(req, wep->rx_tfm); 207 skcipher_request_set_callback(req, 0, NULL, NULL); 208 skcipher_request_set_crypt(req, &sg, &sg, plen + 4, NULL); 209 err = crypto_skcipher_decrypt(req); 210 skcipher_request_zero(req); 211 if (err) 212 return -7; 213 crc = ~crc32_le(~0, pos, plen); 214 icv[0] = crc; 215 icv[1] = crc >> 8; 216 icv[2] = crc >> 16; 217 icv[3] = crc >> 24; 218 if (memcmp(icv, pos + plen, 4) != 0) { 219 /* ICV mismatch - drop frame */ 220 return -2; 221 } 222 } 223 /* Remove IV and ICV */ 224 memmove(skb->data + 4, skb->data, hdr_len); 225 skb_pull(skb, 4); 226 skb_trim(skb, skb->len - 4); 227 228 return 0; 229 } 230 231 232 static int prism2_wep_set_key(void *key, int len, u8 *seq, void *priv) 233 { 234 struct prism2_wep_data *wep = priv; 235 236 if (len < 0 || len > WEP_KEY_LEN) 237 return -1; 238 239 memcpy(wep->key, key, len); 240 wep->key_len = len; 241 242 return 0; 243 } 244 245 246 static int prism2_wep_get_key(void *key, int len, u8 *seq, void *priv) 247 { 248 struct prism2_wep_data *wep = priv; 249 250 if (len < wep->key_len) 251 return -1; 252 253 memcpy(key, wep->key, wep->key_len); 254 255 return wep->key_len; 256 } 257 258 259 static void prism2_wep_print_stats(struct seq_file *m, void *priv) 260 { 261 struct prism2_wep_data *wep = priv; 262 263 seq_printf(m, "key[%d] alg=WEP len=%d\n", wep->key_idx, wep->key_len); 264 } 265 266 static struct lib80211_crypto_ops rtllib_crypt_wep = { 267 .name = "R-WEP", 268 .init = prism2_wep_init, 269 .deinit = prism2_wep_deinit, 270 .encrypt_mpdu = prism2_wep_encrypt, 271 .decrypt_mpdu = prism2_wep_decrypt, 272 .encrypt_msdu = NULL, 273 .decrypt_msdu = NULL, 274 .set_key = prism2_wep_set_key, 275 .get_key = prism2_wep_get_key, 276 .print_stats = prism2_wep_print_stats, 277 .extra_mpdu_prefix_len = 4, /* IV */ 278 .extra_mpdu_postfix_len = 4, /* ICV */ 279 .owner = THIS_MODULE, 280 }; 281 282 283 static int __init rtllib_crypto_wep_init(void) 284 { 285 return lib80211_register_crypto_ops(&rtllib_crypt_wep); 286 } 287 288 289 static void __exit rtllib_crypto_wep_exit(void) 290 { 291 lib80211_unregister_crypto_ops(&rtllib_crypt_wep); 292 } 293 294 module_init(rtllib_crypto_wep_init); 295 module_exit(rtllib_crypto_wep_exit); 296 297 MODULE_LICENSE("GPL"); 298