1 /* 2 * Software WEP encryption implementation 3 * Copyright 2002, Jouni Malinen <jkmaline@cc.hut.fi> 4 * Copyright 2003, Instant802 Networks, Inc. 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. 9 */ 10 11 #include <linux/netdevice.h> 12 #include <linux/types.h> 13 #include <linux/random.h> 14 #include <linux/compiler.h> 15 #include <linux/crc32.h> 16 #include <linux/crypto.h> 17 #include <linux/err.h> 18 #include <linux/mm.h> 19 #include <linux/scatterlist.h> 20 #include <linux/slab.h> 21 #include <asm/unaligned.h> 22 23 #include <net/mac80211.h> 24 #include "ieee80211_i.h" 25 #include "wep.h" 26 27 28 int ieee80211_wep_init(struct ieee80211_local *local) 29 { 30 /* start WEP IV from a random value */ 31 get_random_bytes(&local->wep_iv, IEEE80211_WEP_IV_LEN); 32 33 local->wep_tx_tfm = crypto_alloc_cipher("arc4", 0, CRYPTO_ALG_ASYNC); 34 if (IS_ERR(local->wep_tx_tfm)) { 35 local->wep_rx_tfm = ERR_PTR(-EINVAL); 36 return PTR_ERR(local->wep_tx_tfm); 37 } 38 39 local->wep_rx_tfm = crypto_alloc_cipher("arc4", 0, CRYPTO_ALG_ASYNC); 40 if (IS_ERR(local->wep_rx_tfm)) { 41 crypto_free_cipher(local->wep_tx_tfm); 42 local->wep_tx_tfm = ERR_PTR(-EINVAL); 43 return PTR_ERR(local->wep_rx_tfm); 44 } 45 46 return 0; 47 } 48 49 void ieee80211_wep_free(struct ieee80211_local *local) 50 { 51 if (!IS_ERR(local->wep_tx_tfm)) 52 crypto_free_cipher(local->wep_tx_tfm); 53 if (!IS_ERR(local->wep_rx_tfm)) 54 crypto_free_cipher(local->wep_rx_tfm); 55 } 56 57 static inline bool ieee80211_wep_weak_iv(u32 iv, int keylen) 58 { 59 /* 60 * Fluhrer, Mantin, and Shamir have reported weaknesses in the 61 * key scheduling algorithm of RC4. At least IVs (KeyByte + 3, 62 * 0xff, N) can be used to speedup attacks, so avoid using them. 63 */ 64 if ((iv & 0xff00) == 0xff00) { 65 u8 B = (iv >> 16) & 0xff; 66 if (B >= 3 && B < 3 + keylen) 67 return true; 68 } 69 return false; 70 } 71 72 73 static void ieee80211_wep_get_iv(struct ieee80211_local *local, 74 int keylen, int keyidx, u8 *iv) 75 { 76 local->wep_iv++; 77 if (ieee80211_wep_weak_iv(local->wep_iv, keylen)) 78 local->wep_iv += 0x0100; 79 80 if (!iv) 81 return; 82 83 *iv++ = (local->wep_iv >> 16) & 0xff; 84 *iv++ = (local->wep_iv >> 8) & 0xff; 85 *iv++ = local->wep_iv & 0xff; 86 *iv++ = keyidx << 6; 87 } 88 89 90 static u8 *ieee80211_wep_add_iv(struct ieee80211_local *local, 91 struct sk_buff *skb, 92 int keylen, int keyidx) 93 { 94 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data; 95 struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb); 96 unsigned int hdrlen; 97 u8 *newhdr; 98 99 hdr->frame_control |= cpu_to_le16(IEEE80211_FCTL_PROTECTED); 100 101 if (WARN_ON(skb_tailroom(skb) < IEEE80211_WEP_ICV_LEN || 102 skb_headroom(skb) < IEEE80211_WEP_IV_LEN)) 103 return NULL; 104 105 hdrlen = ieee80211_hdrlen(hdr->frame_control); 106 newhdr = skb_push(skb, IEEE80211_WEP_IV_LEN); 107 memmove(newhdr, newhdr + IEEE80211_WEP_IV_LEN, hdrlen); 108 109 /* the HW only needs room for the IV, but not the actual IV */ 110 if (info->control.hw_key && 111 (info->control.hw_key->flags & IEEE80211_KEY_FLAG_PUT_IV_SPACE)) 112 return newhdr + hdrlen; 113 114 ieee80211_wep_get_iv(local, keylen, keyidx, newhdr + hdrlen); 115 return newhdr + hdrlen; 116 } 117 118 119 static void ieee80211_wep_remove_iv(struct ieee80211_local *local, 120 struct sk_buff *skb, 121 struct ieee80211_key *key) 122 { 123 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data; 124 unsigned int hdrlen; 125 126 hdrlen = ieee80211_hdrlen(hdr->frame_control); 127 memmove(skb->data + IEEE80211_WEP_IV_LEN, skb->data, hdrlen); 128 skb_pull(skb, IEEE80211_WEP_IV_LEN); 129 } 130 131 132 /* Perform WEP encryption using given key. data buffer must have tailroom 133 * for 4-byte ICV. data_len must not include this ICV. Note: this function 134 * does _not_ add IV. data = RC4(data | CRC32(data)) */ 135 int ieee80211_wep_encrypt_data(struct crypto_cipher *tfm, u8 *rc4key, 136 size_t klen, u8 *data, size_t data_len) 137 { 138 __le32 icv; 139 int i; 140 141 if (IS_ERR(tfm)) 142 return -1; 143 144 icv = cpu_to_le32(~crc32_le(~0, data, data_len)); 145 put_unaligned(icv, (__le32 *)(data + data_len)); 146 147 crypto_cipher_setkey(tfm, rc4key, klen); 148 for (i = 0; i < data_len + IEEE80211_WEP_ICV_LEN; i++) 149 crypto_cipher_encrypt_one(tfm, data + i, data + i); 150 151 return 0; 152 } 153 154 155 /* Perform WEP encryption on given skb. 4 bytes of extra space (IV) in the 156 * beginning of the buffer 4 bytes of extra space (ICV) in the end of the 157 * buffer will be added. Both IV and ICV will be transmitted, so the 158 * payload length increases with 8 bytes. 159 * 160 * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data)) 161 */ 162 int ieee80211_wep_encrypt(struct ieee80211_local *local, 163 struct sk_buff *skb, 164 const u8 *key, int keylen, int keyidx) 165 { 166 u8 *iv; 167 size_t len; 168 u8 rc4key[3 + WLAN_KEY_LEN_WEP104]; 169 170 iv = ieee80211_wep_add_iv(local, skb, keylen, keyidx); 171 if (!iv) 172 return -1; 173 174 len = skb->len - (iv + IEEE80211_WEP_IV_LEN - skb->data); 175 176 /* Prepend 24-bit IV to RC4 key */ 177 memcpy(rc4key, iv, 3); 178 179 /* Copy rest of the WEP key (the secret part) */ 180 memcpy(rc4key + 3, key, keylen); 181 182 /* Add room for ICV */ 183 skb_put(skb, IEEE80211_WEP_ICV_LEN); 184 185 return ieee80211_wep_encrypt_data(local->wep_tx_tfm, rc4key, keylen + 3, 186 iv + IEEE80211_WEP_IV_LEN, len); 187 } 188 189 190 /* Perform WEP decryption using given key. data buffer includes encrypted 191 * payload, including 4-byte ICV, but _not_ IV. data_len must not include ICV. 192 * Return 0 on success and -1 on ICV mismatch. */ 193 int ieee80211_wep_decrypt_data(struct crypto_cipher *tfm, u8 *rc4key, 194 size_t klen, u8 *data, size_t data_len) 195 { 196 __le32 crc; 197 int i; 198 199 if (IS_ERR(tfm)) 200 return -1; 201 202 crypto_cipher_setkey(tfm, rc4key, klen); 203 for (i = 0; i < data_len + IEEE80211_WEP_ICV_LEN; i++) 204 crypto_cipher_decrypt_one(tfm, data + i, data + i); 205 206 crc = cpu_to_le32(~crc32_le(~0, data, data_len)); 207 if (memcmp(&crc, data + data_len, IEEE80211_WEP_ICV_LEN) != 0) 208 /* ICV mismatch */ 209 return -1; 210 211 return 0; 212 } 213 214 215 /* Perform WEP decryption on given skb. Buffer includes whole WEP part of 216 * the frame: IV (4 bytes), encrypted payload (including SNAP header), 217 * ICV (4 bytes). skb->len includes both IV and ICV. 218 * 219 * Returns 0 if frame was decrypted successfully and ICV was correct and -1 on 220 * failure. If frame is OK, IV and ICV will be removed, i.e., decrypted payload 221 * is moved to the beginning of the skb and skb length will be reduced. 222 */ 223 static int ieee80211_wep_decrypt(struct ieee80211_local *local, 224 struct sk_buff *skb, 225 struct ieee80211_key *key) 226 { 227 u32 klen; 228 u8 rc4key[3 + WLAN_KEY_LEN_WEP104]; 229 u8 keyidx; 230 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data; 231 unsigned int hdrlen; 232 size_t len; 233 int ret = 0; 234 235 if (!ieee80211_has_protected(hdr->frame_control)) 236 return -1; 237 238 hdrlen = ieee80211_hdrlen(hdr->frame_control); 239 if (skb->len < hdrlen + IEEE80211_WEP_IV_LEN + IEEE80211_WEP_ICV_LEN) 240 return -1; 241 242 len = skb->len - hdrlen - IEEE80211_WEP_IV_LEN - IEEE80211_WEP_ICV_LEN; 243 244 keyidx = skb->data[hdrlen + 3] >> 6; 245 246 if (!key || keyidx != key->conf.keyidx) 247 return -1; 248 249 klen = 3 + key->conf.keylen; 250 251 /* Prepend 24-bit IV to RC4 key */ 252 memcpy(rc4key, skb->data + hdrlen, 3); 253 254 /* Copy rest of the WEP key (the secret part) */ 255 memcpy(rc4key + 3, key->conf.key, key->conf.keylen); 256 257 if (ieee80211_wep_decrypt_data(local->wep_rx_tfm, rc4key, klen, 258 skb->data + hdrlen + 259 IEEE80211_WEP_IV_LEN, len)) 260 ret = -1; 261 262 /* Trim ICV */ 263 skb_trim(skb, skb->len - IEEE80211_WEP_ICV_LEN); 264 265 /* Remove IV */ 266 memmove(skb->data + IEEE80211_WEP_IV_LEN, skb->data, hdrlen); 267 skb_pull(skb, IEEE80211_WEP_IV_LEN); 268 269 return ret; 270 } 271 272 ieee80211_rx_result 273 ieee80211_crypto_wep_decrypt(struct ieee80211_rx_data *rx) 274 { 275 struct sk_buff *skb = rx->skb; 276 struct ieee80211_rx_status *status = IEEE80211_SKB_RXCB(skb); 277 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data; 278 __le16 fc = hdr->frame_control; 279 280 if (!ieee80211_is_data(fc) && !ieee80211_is_auth(fc)) 281 return RX_CONTINUE; 282 283 if (!(status->flag & RX_FLAG_DECRYPTED)) { 284 if (skb_linearize(rx->skb)) 285 return RX_DROP_UNUSABLE; 286 if (ieee80211_wep_decrypt(rx->local, rx->skb, rx->key)) 287 return RX_DROP_UNUSABLE; 288 } else if (!(status->flag & RX_FLAG_IV_STRIPPED)) { 289 if (!pskb_may_pull(rx->skb, ieee80211_hdrlen(fc) + 290 IEEE80211_WEP_IV_LEN)) 291 return RX_DROP_UNUSABLE; 292 ieee80211_wep_remove_iv(rx->local, rx->skb, rx->key); 293 /* remove ICV */ 294 if (pskb_trim(rx->skb, rx->skb->len - IEEE80211_WEP_ICV_LEN)) 295 return RX_DROP_UNUSABLE; 296 } 297 298 return RX_CONTINUE; 299 } 300 301 static int wep_encrypt_skb(struct ieee80211_tx_data *tx, struct sk_buff *skb) 302 { 303 struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb); 304 struct ieee80211_key_conf *hw_key = info->control.hw_key; 305 306 if (!hw_key) { 307 if (ieee80211_wep_encrypt(tx->local, skb, tx->key->conf.key, 308 tx->key->conf.keylen, 309 tx->key->conf.keyidx)) 310 return -1; 311 } else if ((hw_key->flags & IEEE80211_KEY_FLAG_GENERATE_IV) || 312 (hw_key->flags & IEEE80211_KEY_FLAG_PUT_IV_SPACE)) { 313 if (!ieee80211_wep_add_iv(tx->local, skb, 314 tx->key->conf.keylen, 315 tx->key->conf.keyidx)) 316 return -1; 317 } 318 319 return 0; 320 } 321 322 ieee80211_tx_result 323 ieee80211_crypto_wep_encrypt(struct ieee80211_tx_data *tx) 324 { 325 struct sk_buff *skb; 326 327 ieee80211_tx_set_protected(tx); 328 329 skb_queue_walk(&tx->skbs, skb) { 330 if (wep_encrypt_skb(tx, skb) < 0) { 331 I802_DEBUG_INC(tx->local->tx_handlers_drop_wep); 332 return TX_DROP; 333 } 334 } 335 336 return TX_CONTINUE; 337 } 338