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