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_blkcipher("ecb(arc4)", 0, 34 CRYPTO_ALG_ASYNC); 35 if (IS_ERR(local->wep_tx_tfm)) 36 return PTR_ERR(local->wep_tx_tfm); 37 38 local->wep_rx_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0, 39 CRYPTO_ALG_ASYNC); 40 if (IS_ERR(local->wep_rx_tfm)) { 41 crypto_free_blkcipher(local->wep_tx_tfm); 42 return PTR_ERR(local->wep_rx_tfm); 43 } 44 45 return 0; 46 } 47 48 void ieee80211_wep_free(struct ieee80211_local *local) 49 { 50 crypto_free_blkcipher(local->wep_tx_tfm); 51 crypto_free_blkcipher(local->wep_rx_tfm); 52 } 53 54 static inline bool ieee80211_wep_weak_iv(u32 iv, int keylen) 55 { 56 /* 57 * Fluhrer, Mantin, and Shamir have reported weaknesses in the 58 * key scheduling algorithm of RC4. At least IVs (KeyByte + 3, 59 * 0xff, N) can be used to speedup attacks, so avoid using them. 60 */ 61 if ((iv & 0xff00) == 0xff00) { 62 u8 B = (iv >> 16) & 0xff; 63 if (B >= 3 && B < 3 + keylen) 64 return true; 65 } 66 return false; 67 } 68 69 70 static void ieee80211_wep_get_iv(struct ieee80211_local *local, 71 int keylen, int keyidx, u8 *iv) 72 { 73 local->wep_iv++; 74 if (ieee80211_wep_weak_iv(local->wep_iv, keylen)) 75 local->wep_iv += 0x0100; 76 77 if (!iv) 78 return; 79 80 *iv++ = (local->wep_iv >> 16) & 0xff; 81 *iv++ = (local->wep_iv >> 8) & 0xff; 82 *iv++ = local->wep_iv & 0xff; 83 *iv++ = keyidx << 6; 84 } 85 86 87 static u8 *ieee80211_wep_add_iv(struct ieee80211_local *local, 88 struct sk_buff *skb, 89 int keylen, int keyidx) 90 { 91 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data; 92 unsigned int hdrlen; 93 u8 *newhdr; 94 95 hdr->frame_control |= cpu_to_le16(IEEE80211_FCTL_PROTECTED); 96 97 if (WARN_ON(skb_tailroom(skb) < WEP_ICV_LEN || 98 skb_headroom(skb) < WEP_IV_LEN)) 99 return NULL; 100 101 hdrlen = ieee80211_hdrlen(hdr->frame_control); 102 newhdr = skb_push(skb, WEP_IV_LEN); 103 memmove(newhdr, newhdr + WEP_IV_LEN, hdrlen); 104 ieee80211_wep_get_iv(local, keylen, keyidx, newhdr + hdrlen); 105 return newhdr + hdrlen; 106 } 107 108 109 static void ieee80211_wep_remove_iv(struct ieee80211_local *local, 110 struct sk_buff *skb, 111 struct ieee80211_key *key) 112 { 113 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data; 114 unsigned int hdrlen; 115 116 hdrlen = ieee80211_hdrlen(hdr->frame_control); 117 memmove(skb->data + WEP_IV_LEN, skb->data, hdrlen); 118 skb_pull(skb, WEP_IV_LEN); 119 } 120 121 122 /* Perform WEP encryption using given key. data buffer must have tailroom 123 * for 4-byte ICV. data_len must not include this ICV. Note: this function 124 * does _not_ add IV. data = RC4(data | CRC32(data)) */ 125 void ieee80211_wep_encrypt_data(struct crypto_blkcipher *tfm, u8 *rc4key, 126 size_t klen, u8 *data, size_t data_len) 127 { 128 struct blkcipher_desc desc = { .tfm = tfm }; 129 struct scatterlist sg; 130 __le32 icv; 131 132 icv = cpu_to_le32(~crc32_le(~0, data, data_len)); 133 put_unaligned(icv, (__le32 *)(data + data_len)); 134 135 crypto_blkcipher_setkey(tfm, rc4key, klen); 136 sg_init_one(&sg, data, data_len + WEP_ICV_LEN); 137 crypto_blkcipher_encrypt(&desc, &sg, &sg, sg.length); 138 } 139 140 141 /* Perform WEP encryption on given skb. 4 bytes of extra space (IV) in the 142 * beginning of the buffer 4 bytes of extra space (ICV) in the end of the 143 * buffer will be added. Both IV and ICV will be transmitted, so the 144 * payload length increases with 8 bytes. 145 * 146 * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data)) 147 */ 148 int ieee80211_wep_encrypt(struct ieee80211_local *local, 149 struct sk_buff *skb, 150 const u8 *key, int keylen, int keyidx) 151 { 152 u8 *iv; 153 size_t len; 154 u8 rc4key[3 + WLAN_KEY_LEN_WEP104]; 155 156 iv = ieee80211_wep_add_iv(local, skb, keylen, keyidx); 157 if (!iv) 158 return -1; 159 160 len = skb->len - (iv + WEP_IV_LEN - skb->data); 161 162 /* Prepend 24-bit IV to RC4 key */ 163 memcpy(rc4key, iv, 3); 164 165 /* Copy rest of the WEP key (the secret part) */ 166 memcpy(rc4key + 3, key, keylen); 167 168 /* Add room for ICV */ 169 skb_put(skb, WEP_ICV_LEN); 170 171 ieee80211_wep_encrypt_data(local->wep_tx_tfm, rc4key, keylen + 3, 172 iv + WEP_IV_LEN, len); 173 174 return 0; 175 } 176 177 178 /* Perform WEP decryption using given key. data buffer includes encrypted 179 * payload, including 4-byte ICV, but _not_ IV. data_len must not include ICV. 180 * Return 0 on success and -1 on ICV mismatch. */ 181 int ieee80211_wep_decrypt_data(struct crypto_blkcipher *tfm, u8 *rc4key, 182 size_t klen, u8 *data, size_t data_len) 183 { 184 struct blkcipher_desc desc = { .tfm = tfm }; 185 struct scatterlist sg; 186 __le32 crc; 187 188 crypto_blkcipher_setkey(tfm, rc4key, klen); 189 sg_init_one(&sg, data, data_len + WEP_ICV_LEN); 190 crypto_blkcipher_decrypt(&desc, &sg, &sg, sg.length); 191 192 crc = cpu_to_le32(~crc32_le(~0, data, data_len)); 193 if (memcmp(&crc, data + data_len, WEP_ICV_LEN) != 0) 194 /* ICV mismatch */ 195 return -1; 196 197 return 0; 198 } 199 200 201 /* Perform WEP decryption on given skb. Buffer includes whole WEP part of 202 * the frame: IV (4 bytes), encrypted payload (including SNAP header), 203 * ICV (4 bytes). skb->len includes both IV and ICV. 204 * 205 * Returns 0 if frame was decrypted successfully and ICV was correct and -1 on 206 * failure. If frame is OK, IV and ICV will be removed, i.e., decrypted payload 207 * is moved to the beginning of the skb and skb length will be reduced. 208 */ 209 static int ieee80211_wep_decrypt(struct ieee80211_local *local, 210 struct sk_buff *skb, 211 struct ieee80211_key *key) 212 { 213 u32 klen; 214 u8 *rc4key; 215 u8 keyidx; 216 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data; 217 unsigned int hdrlen; 218 size_t len; 219 int ret = 0; 220 221 if (!ieee80211_has_protected(hdr->frame_control)) 222 return -1; 223 224 hdrlen = ieee80211_hdrlen(hdr->frame_control); 225 if (skb->len < hdrlen + WEP_IV_LEN + WEP_ICV_LEN) 226 return -1; 227 228 len = skb->len - hdrlen - WEP_IV_LEN - WEP_ICV_LEN; 229 230 keyidx = skb->data[hdrlen + 3] >> 6; 231 232 if (!key || keyidx != key->conf.keyidx || key->conf.alg != ALG_WEP) 233 return -1; 234 235 klen = 3 + key->conf.keylen; 236 237 rc4key = kmalloc(klen, GFP_ATOMIC); 238 if (!rc4key) 239 return -1; 240 241 /* Prepend 24-bit IV to RC4 key */ 242 memcpy(rc4key, skb->data + hdrlen, 3); 243 244 /* Copy rest of the WEP key (the secret part) */ 245 memcpy(rc4key + 3, key->conf.key, key->conf.keylen); 246 247 if (ieee80211_wep_decrypt_data(local->wep_rx_tfm, rc4key, klen, 248 skb->data + hdrlen + WEP_IV_LEN, 249 len)) 250 ret = -1; 251 252 kfree(rc4key); 253 254 /* Trim ICV */ 255 skb_trim(skb, skb->len - WEP_ICV_LEN); 256 257 /* Remove IV */ 258 memmove(skb->data + WEP_IV_LEN, skb->data, hdrlen); 259 skb_pull(skb, WEP_IV_LEN); 260 261 return ret; 262 } 263 264 265 bool ieee80211_wep_is_weak_iv(struct sk_buff *skb, struct ieee80211_key *key) 266 { 267 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data; 268 unsigned int hdrlen; 269 u8 *ivpos; 270 u32 iv; 271 272 if (!ieee80211_has_protected(hdr->frame_control)) 273 return false; 274 275 hdrlen = ieee80211_hdrlen(hdr->frame_control); 276 ivpos = skb->data + hdrlen; 277 iv = (ivpos[0] << 16) | (ivpos[1] << 8) | ivpos[2]; 278 279 return ieee80211_wep_weak_iv(iv, key->conf.keylen); 280 } 281 282 ieee80211_rx_result 283 ieee80211_crypto_wep_decrypt(struct ieee80211_rx_data *rx) 284 { 285 struct sk_buff *skb = rx->skb; 286 struct ieee80211_rx_status *status = IEEE80211_SKB_RXCB(skb); 287 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data; 288 289 if (!ieee80211_is_data(hdr->frame_control) && 290 !ieee80211_is_auth(hdr->frame_control)) 291 return RX_CONTINUE; 292 293 if (!(status->flag & RX_FLAG_DECRYPTED)) { 294 if (ieee80211_wep_decrypt(rx->local, rx->skb, rx->key)) 295 return RX_DROP_UNUSABLE; 296 } else if (!(status->flag & RX_FLAG_IV_STRIPPED)) { 297 ieee80211_wep_remove_iv(rx->local, rx->skb, rx->key); 298 /* remove ICV */ 299 skb_trim(rx->skb, rx->skb->len - WEP_ICV_LEN); 300 } 301 302 return RX_CONTINUE; 303 } 304 305 static int wep_encrypt_skb(struct ieee80211_tx_data *tx, struct sk_buff *skb) 306 { 307 struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb); 308 309 if (!info->control.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 (info->control.hw_key->flags & 315 IEEE80211_KEY_FLAG_GENERATE_IV) { 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 = tx->skb; 333 do { 334 if (wep_encrypt_skb(tx, skb) < 0) { 335 I802_DEBUG_INC(tx->local->tx_handlers_drop_wep); 336 return TX_DROP; 337 } 338 } while ((skb = skb->next)); 339 340 return TX_CONTINUE; 341 } 342