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, 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 unsigned int hdrlen; 96 u8 *newhdr; 97 98 hdr->frame_control |= cpu_to_le16(IEEE80211_FCTL_PROTECTED); 99 100 if (WARN_ON(skb_tailroom(skb) < WEP_ICV_LEN || 101 skb_headroom(skb) < WEP_IV_LEN)) 102 return NULL; 103 104 hdrlen = ieee80211_hdrlen(hdr->frame_control); 105 newhdr = skb_push(skb, WEP_IV_LEN); 106 memmove(newhdr, newhdr + WEP_IV_LEN, hdrlen); 107 ieee80211_wep_get_iv(local, keylen, keyidx, newhdr + hdrlen); 108 return newhdr + hdrlen; 109 } 110 111 112 static void ieee80211_wep_remove_iv(struct ieee80211_local *local, 113 struct sk_buff *skb, 114 struct ieee80211_key *key) 115 { 116 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data; 117 unsigned int hdrlen; 118 119 hdrlen = ieee80211_hdrlen(hdr->frame_control); 120 memmove(skb->data + WEP_IV_LEN, skb->data, hdrlen); 121 skb_pull(skb, WEP_IV_LEN); 122 } 123 124 125 /* Perform WEP encryption using given key. data buffer must have tailroom 126 * for 4-byte ICV. data_len must not include this ICV. Note: this function 127 * does _not_ add IV. data = RC4(data | CRC32(data)) */ 128 int ieee80211_wep_encrypt_data(struct crypto_cipher *tfm, u8 *rc4key, 129 size_t klen, u8 *data, size_t data_len) 130 { 131 __le32 icv; 132 int i; 133 134 if (IS_ERR(tfm)) 135 return -1; 136 137 icv = cpu_to_le32(~crc32_le(~0, data, data_len)); 138 put_unaligned(icv, (__le32 *)(data + data_len)); 139 140 crypto_cipher_setkey(tfm, rc4key, klen); 141 for (i = 0; i < data_len + WEP_ICV_LEN; i++) 142 crypto_cipher_encrypt_one(tfm, data + i, data + i); 143 144 return 0; 145 } 146 147 148 /* Perform WEP encryption on given skb. 4 bytes of extra space (IV) in the 149 * beginning of the buffer 4 bytes of extra space (ICV) in the end of the 150 * buffer will be added. Both IV and ICV will be transmitted, so the 151 * payload length increases with 8 bytes. 152 * 153 * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data)) 154 */ 155 int ieee80211_wep_encrypt(struct ieee80211_local *local, 156 struct sk_buff *skb, 157 const u8 *key, int keylen, int keyidx) 158 { 159 u8 *iv; 160 size_t len; 161 u8 rc4key[3 + WLAN_KEY_LEN_WEP104]; 162 163 iv = ieee80211_wep_add_iv(local, skb, keylen, keyidx); 164 if (!iv) 165 return -1; 166 167 len = skb->len - (iv + WEP_IV_LEN - skb->data); 168 169 /* Prepend 24-bit IV to RC4 key */ 170 memcpy(rc4key, iv, 3); 171 172 /* Copy rest of the WEP key (the secret part) */ 173 memcpy(rc4key + 3, key, keylen); 174 175 /* Add room for ICV */ 176 skb_put(skb, WEP_ICV_LEN); 177 178 return ieee80211_wep_encrypt_data(local->wep_tx_tfm, rc4key, keylen + 3, 179 iv + WEP_IV_LEN, len); 180 } 181 182 183 /* Perform WEP decryption using given key. data buffer includes encrypted 184 * payload, including 4-byte ICV, but _not_ IV. data_len must not include ICV. 185 * Return 0 on success and -1 on ICV mismatch. */ 186 int ieee80211_wep_decrypt_data(struct crypto_cipher *tfm, u8 *rc4key, 187 size_t klen, u8 *data, size_t data_len) 188 { 189 __le32 crc; 190 int i; 191 192 if (IS_ERR(tfm)) 193 return -1; 194 195 crypto_cipher_setkey(tfm, rc4key, klen); 196 for (i = 0; i < data_len + WEP_ICV_LEN; i++) 197 crypto_cipher_decrypt_one(tfm, data + i, data + i); 198 199 crc = cpu_to_le32(~crc32_le(~0, data, data_len)); 200 if (memcmp(&crc, data + data_len, WEP_ICV_LEN) != 0) 201 /* ICV mismatch */ 202 return -1; 203 204 return 0; 205 } 206 207 208 /* Perform WEP decryption on given skb. Buffer includes whole WEP part of 209 * the frame: IV (4 bytes), encrypted payload (including SNAP header), 210 * ICV (4 bytes). skb->len includes both IV and ICV. 211 * 212 * Returns 0 if frame was decrypted successfully and ICV was correct and -1 on 213 * failure. If frame is OK, IV and ICV will be removed, i.e., decrypted payload 214 * is moved to the beginning of the skb and skb length will be reduced. 215 */ 216 static int ieee80211_wep_decrypt(struct ieee80211_local *local, 217 struct sk_buff *skb, 218 struct ieee80211_key *key) 219 { 220 u32 klen; 221 u8 rc4key[3 + WLAN_KEY_LEN_WEP104]; 222 u8 keyidx; 223 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data; 224 unsigned int hdrlen; 225 size_t len; 226 int ret = 0; 227 228 if (!ieee80211_has_protected(hdr->frame_control)) 229 return -1; 230 231 hdrlen = ieee80211_hdrlen(hdr->frame_control); 232 if (skb->len < hdrlen + WEP_IV_LEN + WEP_ICV_LEN) 233 return -1; 234 235 len = skb->len - hdrlen - WEP_IV_LEN - WEP_ICV_LEN; 236 237 keyidx = skb->data[hdrlen + 3] >> 6; 238 239 if (!key || keyidx != key->conf.keyidx) 240 return -1; 241 242 klen = 3 + key->conf.keylen; 243 244 /* Prepend 24-bit IV to RC4 key */ 245 memcpy(rc4key, skb->data + hdrlen, 3); 246 247 /* Copy rest of the WEP key (the secret part) */ 248 memcpy(rc4key + 3, key->conf.key, key->conf.keylen); 249 250 if (ieee80211_wep_decrypt_data(local->wep_rx_tfm, rc4key, klen, 251 skb->data + hdrlen + WEP_IV_LEN, 252 len)) 253 ret = -1; 254 255 /* Trim ICV */ 256 skb_trim(skb, skb->len - WEP_ICV_LEN); 257 258 /* Remove IV */ 259 memmove(skb->data + WEP_IV_LEN, skb->data, hdrlen); 260 skb_pull(skb, WEP_IV_LEN); 261 262 return ret; 263 } 264 265 266 static bool ieee80211_wep_is_weak_iv(struct sk_buff *skb, 267 struct ieee80211_key *key) 268 { 269 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data; 270 unsigned int hdrlen; 271 u8 *ivpos; 272 u32 iv; 273 274 hdrlen = ieee80211_hdrlen(hdr->frame_control); 275 ivpos = skb->data + hdrlen; 276 iv = (ivpos[0] << 16) | (ivpos[1] << 8) | ivpos[2]; 277 278 return ieee80211_wep_weak_iv(iv, key->conf.keylen); 279 } 280 281 ieee80211_rx_result 282 ieee80211_crypto_wep_decrypt(struct ieee80211_rx_data *rx) 283 { 284 struct sk_buff *skb = rx->skb; 285 struct ieee80211_rx_status *status = IEEE80211_SKB_RXCB(skb); 286 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data; 287 __le16 fc = hdr->frame_control; 288 289 if (!ieee80211_is_data(fc) && !ieee80211_is_auth(fc)) 290 return RX_CONTINUE; 291 292 if (!(status->flag & RX_FLAG_DECRYPTED)) { 293 if (skb_linearize(rx->skb)) 294 return RX_DROP_UNUSABLE; 295 if (rx->sta && ieee80211_wep_is_weak_iv(rx->skb, rx->key)) 296 rx->sta->wep_weak_iv_count++; 297 if (ieee80211_wep_decrypt(rx->local, rx->skb, rx->key)) 298 return RX_DROP_UNUSABLE; 299 } else if (!(status->flag & RX_FLAG_IV_STRIPPED)) { 300 if (!pskb_may_pull(rx->skb, ieee80211_hdrlen(fc) + WEP_IV_LEN)) 301 return RX_DROP_UNUSABLE; 302 if (rx->sta && ieee80211_wep_is_weak_iv(rx->skb, rx->key)) 303 rx->sta->wep_weak_iv_count++; 304 ieee80211_wep_remove_iv(rx->local, rx->skb, rx->key); 305 /* remove ICV */ 306 if (pskb_trim(rx->skb, rx->skb->len - WEP_ICV_LEN)) 307 return RX_DROP_UNUSABLE; 308 } 309 310 return RX_CONTINUE; 311 } 312 313 static int wep_encrypt_skb(struct ieee80211_tx_data *tx, struct sk_buff *skb) 314 { 315 struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb); 316 317 if (!info->control.hw_key) { 318 if (ieee80211_wep_encrypt(tx->local, skb, tx->key->conf.key, 319 tx->key->conf.keylen, 320 tx->key->conf.keyidx)) 321 return -1; 322 } else if (info->control.hw_key->flags & 323 IEEE80211_KEY_FLAG_GENERATE_IV) { 324 if (!ieee80211_wep_add_iv(tx->local, skb, 325 tx->key->conf.keylen, 326 tx->key->conf.keyidx)) 327 return -1; 328 } 329 330 return 0; 331 } 332 333 ieee80211_tx_result 334 ieee80211_crypto_wep_encrypt(struct ieee80211_tx_data *tx) 335 { 336 struct sk_buff *skb; 337 338 ieee80211_tx_set_protected(tx); 339 340 skb_queue_walk(&tx->skbs, skb) { 341 if (wep_encrypt_skb(tx, skb) < 0) { 342 I802_DEBUG_INC(tx->local->tx_handlers_drop_wep); 343 return TX_DROP; 344 } 345 } 346 347 return TX_CONTINUE; 348 } 349