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/config.h> 13#include <linux/version.h> 14#include <linux/module.h> 15#include <linux/init.h> 16#include <linux/slab.h> 17#include <linux/random.h> 18#include <linux/skbuff.h> 19#include <asm/string.h> 20 21#include "ieee80211.h" 22 23 24#include <linux/crypto.h> 25 26#include <linux/scatterlist.h> 27#include <linux/crc32.h> 28 29MODULE_AUTHOR("Jouni Malinen"); 30MODULE_DESCRIPTION("Host AP crypt: WEP"); 31MODULE_LICENSE("GPL"); 32#ifndef OPENSUSE_SLED 33#define OPENSUSE_SLED 0 34#endif 35 36struct prism2_wep_data { 37 u32 iv; 38#define WEP_KEY_LEN 13 39 u8 key[WEP_KEY_LEN + 1]; 40 u8 key_len; 41 u8 key_idx; 42 struct crypto_blkcipher *tx_tfm; 43 struct crypto_blkcipher *rx_tfm; 44}; 45 46 47static void * prism2_wep_init(int keyidx) 48{ 49 struct prism2_wep_data *priv; 50 51 priv = kzalloc(sizeof(*priv), GFP_ATOMIC); 52 if (priv == NULL) 53 goto fail; 54 priv->key_idx = keyidx; 55 56 priv->tx_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0, CRYPTO_ALG_ASYNC); 57 if (IS_ERR(priv->tx_tfm)) { 58 printk(KERN_DEBUG "ieee80211_crypt_wep: could not allocate " 59 "crypto API arc4\n"); 60 priv->tx_tfm = NULL; 61 goto fail; 62 } 63 priv->rx_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0, CRYPTO_ALG_ASYNC); 64 if (IS_ERR(priv->rx_tfm)) { 65 printk(KERN_DEBUG "ieee80211_crypt_wep: could not allocate " 66 "crypto API arc4\n"); 67 priv->rx_tfm = NULL; 68 goto fail; 69 } 70 71 /* start WEP IV from a random value */ 72 get_random_bytes(&priv->iv, 4); 73 74 return priv; 75 76fail: 77 if (priv) { 78 if (priv->tx_tfm) 79 crypto_free_blkcipher(priv->tx_tfm); 80 if (priv->rx_tfm) 81 crypto_free_blkcipher(priv->rx_tfm); 82 kfree(priv); 83 } 84 return NULL; 85} 86 87 88static void prism2_wep_deinit(void *priv) 89{ 90 struct prism2_wep_data *_priv = priv; 91 if (_priv) { 92 if (_priv->tx_tfm) 93 crypto_free_blkcipher(_priv->tx_tfm); 94 if (_priv->rx_tfm) 95 crypto_free_blkcipher(_priv->rx_tfm); 96 } 97 kfree(priv); 98} 99 100/* Perform WEP encryption on given skb that has at least 4 bytes of headroom 101 * for IV and 4 bytes of tailroom for ICV. Both IV and ICV will be transmitted, 102 * so the payload length increases with 8 bytes. 103 * 104 * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data)) 105 */ 106static int prism2_wep_encrypt(struct sk_buff *skb, int hdr_len, void *priv) 107{ 108 struct prism2_wep_data *wep = priv; 109 u32 klen, len; 110 u8 key[WEP_KEY_LEN + 3]; 111 u8 *pos; 112 cb_desc *tcb_desc = (cb_desc *)(skb->cb + MAX_DEV_ADDR_SIZE); 113 struct blkcipher_desc desc = {.tfm = wep->tx_tfm}; 114 u32 crc; 115 u8 *icv; 116 struct scatterlist sg; 117 if (skb_headroom(skb) < 4 || skb_tailroom(skb) < 4 || 118 skb->len < hdr_len) 119 return -1; 120 121 len = skb->len - hdr_len; 122 pos = skb_push(skb, 4); 123 memmove(pos, pos + 4, hdr_len); 124 pos += hdr_len; 125 126 klen = 3 + wep->key_len; 127 128 wep->iv++; 129 130 /* Fluhrer, Mantin, and Shamir have reported weaknesses in the key 131 * scheduling algorithm of RC4. At least IVs (KeyByte + 3, 0xff, N) 132 * can be used to speedup attacks, so avoid using them. */ 133 if ((wep->iv & 0xff00) == 0xff00) { 134 u8 B = (wep->iv >> 16) & 0xff; 135 if (B >= 3 && B < klen) 136 wep->iv += 0x0100; 137 } 138 139 /* Prepend 24-bit IV to RC4 key and TX frame */ 140 *pos++ = key[0] = (wep->iv >> 16) & 0xff; 141 *pos++ = key[1] = (wep->iv >> 8) & 0xff; 142 *pos++ = key[2] = wep->iv & 0xff; 143 *pos++ = wep->key_idx << 6; 144 145 /* Copy rest of the WEP key (the secret part) */ 146 memcpy(key + 3, wep->key, wep->key_len); 147 148 if (!tcb_desc->bHwSec) 149 { 150 151 /* Append little-endian CRC32 and encrypt it to produce ICV */ 152 crc = ~crc32_le(~0, pos, len); 153 icv = skb_put(skb, 4); 154 icv[0] = crc; 155 icv[1] = crc >> 8; 156 icv[2] = crc >> 16; 157 icv[3] = crc >> 24; 158 159 crypto_blkcipher_setkey(wep->tx_tfm, key, klen); 160 sg_init_one(&sg, pos, len+4); 161 return crypto_blkcipher_encrypt(&desc, &sg, &sg, len + 4); 162 } 163 164 return 0; 165} 166 167 168/* Perform WEP decryption on given buffer. Buffer includes whole WEP part of 169 * the frame: IV (4 bytes), encrypted payload (including SNAP header), 170 * ICV (4 bytes). len includes both IV and ICV. 171 * 172 * Returns 0 if frame was decrypted successfully and ICV was correct and -1 on 173 * failure. If frame is OK, IV and ICV will be removed. 174 */ 175static int prism2_wep_decrypt(struct sk_buff *skb, int hdr_len, void *priv) 176{ 177 struct prism2_wep_data *wep = priv; 178 u32 klen, plen; 179 u8 key[WEP_KEY_LEN + 3]; 180 u8 keyidx, *pos; 181 cb_desc *tcb_desc = (cb_desc *)(skb->cb + MAX_DEV_ADDR_SIZE); 182 struct blkcipher_desc desc = {.tfm = wep->rx_tfm}; 183 u32 crc; 184 u8 icv[4]; 185 struct scatterlist sg; 186 if (skb->len < hdr_len + 8) 187 return -1; 188 189 pos = skb->data + hdr_len; 190 key[0] = *pos++; 191 key[1] = *pos++; 192 key[2] = *pos++; 193 keyidx = *pos++ >> 6; 194 if (keyidx != wep->key_idx) 195 return -1; 196 197 klen = 3 + wep->key_len; 198 199 /* Copy rest of the WEP key (the secret part) */ 200 memcpy(key + 3, wep->key, wep->key_len); 201 202 /* Apply RC4 to data and compute CRC32 over decrypted data */ 203 plen = skb->len - hdr_len - 8; 204 205 if (!tcb_desc->bHwSec) 206 { 207 crypto_blkcipher_setkey(wep->rx_tfm, key, klen); 208 sg_init_one(&sg, pos, plen+4); 209 if (crypto_blkcipher_decrypt(&desc, &sg, &sg, plen + 4)) 210 return -7; 211 crc = ~crc32_le(~0, pos, plen); 212 icv[0] = crc; 213 icv[1] = crc >> 8; 214 icv[2] = crc >> 16; 215 icv[3] = crc >> 24; 216 if (memcmp(icv, pos + plen, 4) != 0) { 217 /* ICV mismatch - drop frame */ 218 return -2; 219 } 220 } 221 /* Remove IV and ICV */ 222 memmove(skb->data + 4, skb->data, hdr_len); 223 skb_pull(skb, 4); 224 skb_trim(skb, skb->len - 4); 225 226 return 0; 227} 228 229 230static int prism2_wep_set_key(void *key, int len, u8 *seq, void *priv) 231{ 232 struct prism2_wep_data *wep = priv; 233 234 if (len < 0 || len > WEP_KEY_LEN) 235 return -1; 236 237 memcpy(wep->key, key, len); 238 wep->key_len = len; 239 240 return 0; 241} 242 243 244static int prism2_wep_get_key(void *key, int len, u8 *seq, void *priv) 245{ 246 struct prism2_wep_data *wep = priv; 247 248 if (len < wep->key_len) 249 return -1; 250 251 memcpy(key, wep->key, wep->key_len); 252 253 return wep->key_len; 254} 255 256 257static char * prism2_wep_print_stats(char *p, void *priv) 258{ 259 struct prism2_wep_data *wep = priv; 260 p += sprintf(p, "key[%d] alg=WEP len=%d\n", 261 wep->key_idx, wep->key_len); 262 return p; 263} 264 265 266static struct ieee80211_crypto_ops ieee80211_crypt_wep = { 267 .name = "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_prefix_len = 4, /* IV */ 278 .extra_postfix_len = 4, /* ICV */ 279 .owner = THIS_MODULE, 280}; 281 282 283int __init ieee80211_crypto_wep_init(void) 284{ 285 return ieee80211_register_crypto_ops(&ieee80211_crypt_wep); 286} 287 288 289void __exit ieee80211_crypto_wep_exit(void) 290{ 291 ieee80211_unregister_crypto_ops(&ieee80211_crypt_wep); 292} 293 294void ieee80211_wep_null(void) 295{ 296 return; 297} 298