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, 0); 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, 0); 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_headroom(skb) < IEEE80211_WEP_IV_LEN)) 102 return NULL; 103 104 hdrlen = ieee80211_hdrlen(hdr->frame_control); 105 newhdr = skb_push(skb, IEEE80211_WEP_IV_LEN); 106 memmove(newhdr, newhdr + IEEE80211_WEP_IV_LEN, hdrlen); 107 108 /* the HW only needs room for the IV, but not the actual IV */ 109 if (info->control.hw_key && 110 (info->control.hw_key->flags & IEEE80211_KEY_FLAG_PUT_IV_SPACE)) 111 return newhdr + hdrlen; 112 113 ieee80211_wep_get_iv(local, keylen, keyidx, newhdr + hdrlen); 114 return newhdr + hdrlen; 115 } 116 117 118 static void ieee80211_wep_remove_iv(struct ieee80211_local *local, 119 struct sk_buff *skb, 120 struct ieee80211_key *key) 121 { 122 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data; 123 unsigned int hdrlen; 124 125 hdrlen = ieee80211_hdrlen(hdr->frame_control); 126 memmove(skb->data + IEEE80211_WEP_IV_LEN, skb->data, hdrlen); 127 skb_pull(skb, IEEE80211_WEP_IV_LEN); 128 } 129 130 131 /* Perform WEP encryption using given key. data buffer must have tailroom 132 * for 4-byte ICV. data_len must not include this ICV. Note: this function 133 * does _not_ add IV. data = RC4(data | CRC32(data)) */ 134 int ieee80211_wep_encrypt_data(struct crypto_cipher *tfm, u8 *rc4key, 135 size_t klen, u8 *data, size_t data_len) 136 { 137 __le32 icv; 138 int i; 139 140 if (IS_ERR(tfm)) 141 return -1; 142 143 icv = cpu_to_le32(~crc32_le(~0, data, data_len)); 144 put_unaligned(icv, (__le32 *)(data + data_len)); 145 146 crypto_cipher_setkey(tfm, rc4key, klen); 147 for (i = 0; i < data_len + IEEE80211_WEP_ICV_LEN; i++) 148 crypto_cipher_encrypt_one(tfm, data + i, data + i); 149 150 return 0; 151 } 152 153 154 /* Perform WEP encryption on given skb. 4 bytes of extra space (IV) in the 155 * beginning of the buffer 4 bytes of extra space (ICV) in the end of the 156 * buffer will be added. Both IV and ICV will be transmitted, so the 157 * payload length increases with 8 bytes. 158 * 159 * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data)) 160 */ 161 int ieee80211_wep_encrypt(struct ieee80211_local *local, 162 struct sk_buff *skb, 163 const u8 *key, int keylen, int keyidx) 164 { 165 u8 *iv; 166 size_t len; 167 u8 rc4key[3 + WLAN_KEY_LEN_WEP104]; 168 169 if (WARN_ON(skb_tailroom(skb) < IEEE80211_WEP_ICV_LEN)) 170 return -1; 171 172 iv = ieee80211_wep_add_iv(local, skb, keylen, keyidx); 173 if (!iv) 174 return -1; 175 176 len = skb->len - (iv + IEEE80211_WEP_IV_LEN - skb->data); 177 178 /* Prepend 24-bit IV to RC4 key */ 179 memcpy(rc4key, iv, 3); 180 181 /* Copy rest of the WEP key (the secret part) */ 182 memcpy(rc4key + 3, key, keylen); 183 184 /* Add room for ICV */ 185 skb_put(skb, IEEE80211_WEP_ICV_LEN); 186 187 return ieee80211_wep_encrypt_data(local->wep_tx_tfm, rc4key, keylen + 3, 188 iv + IEEE80211_WEP_IV_LEN, len); 189 } 190 191 192 /* Perform WEP decryption using given key. data buffer includes encrypted 193 * payload, including 4-byte ICV, but _not_ IV. data_len must not include ICV. 194 * Return 0 on success and -1 on ICV mismatch. */ 195 int ieee80211_wep_decrypt_data(struct crypto_cipher *tfm, u8 *rc4key, 196 size_t klen, u8 *data, size_t data_len) 197 { 198 __le32 crc; 199 int i; 200 201 if (IS_ERR(tfm)) 202 return -1; 203 204 crypto_cipher_setkey(tfm, rc4key, klen); 205 for (i = 0; i < data_len + IEEE80211_WEP_ICV_LEN; i++) 206 crypto_cipher_decrypt_one(tfm, data + i, data + i); 207 208 crc = cpu_to_le32(~crc32_le(~0, data, data_len)); 209 if (memcmp(&crc, data + data_len, IEEE80211_WEP_ICV_LEN) != 0) 210 /* ICV mismatch */ 211 return -1; 212 213 return 0; 214 } 215 216 217 /* Perform WEP decryption on given skb. Buffer includes whole WEP part of 218 * the frame: IV (4 bytes), encrypted payload (including SNAP header), 219 * ICV (4 bytes). skb->len includes both IV and ICV. 220 * 221 * Returns 0 if frame was decrypted successfully and ICV was correct and -1 on 222 * failure. If frame is OK, IV and ICV will be removed, i.e., decrypted payload 223 * is moved to the beginning of the skb and skb length will be reduced. 224 */ 225 static int ieee80211_wep_decrypt(struct ieee80211_local *local, 226 struct sk_buff *skb, 227 struct ieee80211_key *key) 228 { 229 u32 klen; 230 u8 rc4key[3 + WLAN_KEY_LEN_WEP104]; 231 u8 keyidx; 232 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data; 233 unsigned int hdrlen; 234 size_t len; 235 int ret = 0; 236 237 if (!ieee80211_has_protected(hdr->frame_control)) 238 return -1; 239 240 hdrlen = ieee80211_hdrlen(hdr->frame_control); 241 if (skb->len < hdrlen + IEEE80211_WEP_IV_LEN + IEEE80211_WEP_ICV_LEN) 242 return -1; 243 244 len = skb->len - hdrlen - IEEE80211_WEP_IV_LEN - IEEE80211_WEP_ICV_LEN; 245 246 keyidx = skb->data[hdrlen + 3] >> 6; 247 248 if (!key || keyidx != key->conf.keyidx) 249 return -1; 250 251 klen = 3 + key->conf.keylen; 252 253 /* Prepend 24-bit IV to RC4 key */ 254 memcpy(rc4key, skb->data + hdrlen, 3); 255 256 /* Copy rest of the WEP key (the secret part) */ 257 memcpy(rc4key + 3, key->conf.key, key->conf.keylen); 258 259 if (ieee80211_wep_decrypt_data(local->wep_rx_tfm, rc4key, klen, 260 skb->data + hdrlen + 261 IEEE80211_WEP_IV_LEN, len)) 262 ret = -1; 263 264 /* Trim ICV */ 265 skb_trim(skb, skb->len - IEEE80211_WEP_ICV_LEN); 266 267 /* Remove IV */ 268 memmove(skb->data + IEEE80211_WEP_IV_LEN, skb->data, hdrlen); 269 skb_pull(skb, IEEE80211_WEP_IV_LEN); 270 271 return ret; 272 } 273 274 ieee80211_rx_result 275 ieee80211_crypto_wep_decrypt(struct ieee80211_rx_data *rx) 276 { 277 struct sk_buff *skb = rx->skb; 278 struct ieee80211_rx_status *status = IEEE80211_SKB_RXCB(skb); 279 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data; 280 __le16 fc = hdr->frame_control; 281 282 if (!ieee80211_is_data(fc) && !ieee80211_is_auth(fc)) 283 return RX_CONTINUE; 284 285 if (!(status->flag & RX_FLAG_DECRYPTED)) { 286 if (skb_linearize(rx->skb)) 287 return RX_DROP_UNUSABLE; 288 if (ieee80211_wep_decrypt(rx->local, rx->skb, rx->key)) 289 return RX_DROP_UNUSABLE; 290 } else if (!(status->flag & RX_FLAG_IV_STRIPPED)) { 291 if (!pskb_may_pull(rx->skb, ieee80211_hdrlen(fc) + 292 IEEE80211_WEP_IV_LEN)) 293 return RX_DROP_UNUSABLE; 294 ieee80211_wep_remove_iv(rx->local, rx->skb, rx->key); 295 /* remove ICV */ 296 if (!(status->flag & RX_FLAG_ICV_STRIPPED) && 297 pskb_trim(rx->skb, rx->skb->len - IEEE80211_WEP_ICV_LEN)) 298 return RX_DROP_UNUSABLE; 299 } 300 301 return RX_CONTINUE; 302 } 303 304 static int wep_encrypt_skb(struct ieee80211_tx_data *tx, struct sk_buff *skb) 305 { 306 struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb); 307 struct ieee80211_key_conf *hw_key = info->control.hw_key; 308 309 if (!hw_key) { 310 if (ieee80211_wep_encrypt(tx->local, skb, tx->key->conf.key, 311 tx->key->conf.keylen, 312 tx->key->conf.keyidx)) 313 return -1; 314 } else if ((hw_key->flags & IEEE80211_KEY_FLAG_GENERATE_IV) || 315 (hw_key->flags & IEEE80211_KEY_FLAG_PUT_IV_SPACE)) { 316 if (!ieee80211_wep_add_iv(tx->local, skb, 317 tx->key->conf.keylen, 318 tx->key->conf.keyidx)) 319 return -1; 320 } 321 322 return 0; 323 } 324 325 ieee80211_tx_result 326 ieee80211_crypto_wep_encrypt(struct ieee80211_tx_data *tx) 327 { 328 struct sk_buff *skb; 329 330 ieee80211_tx_set_protected(tx); 331 332 skb_queue_walk(&tx->skbs, skb) { 333 if (wep_encrypt_skb(tx, skb) < 0) { 334 I802_DEBUG_INC(tx->local->tx_handlers_drop_wep); 335 return TX_DROP; 336 } 337 } 338 339 return TX_CONTINUE; 340 } 341