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 <asm/unaligned.h> 21 22 #include <net/mac80211.h> 23 #include "ieee80211_i.h" 24 #include "wep.h" 25 26 27 int ieee80211_wep_init(struct ieee80211_local *local) 28 { 29 /* start WEP IV from a random value */ 30 get_random_bytes(&local->wep_iv, WEP_IV_LEN); 31 32 local->wep_tx_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0, 33 CRYPTO_ALG_ASYNC); 34 if (IS_ERR(local->wep_tx_tfm)) 35 return PTR_ERR(local->wep_tx_tfm); 36 37 local->wep_rx_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0, 38 CRYPTO_ALG_ASYNC); 39 if (IS_ERR(local->wep_rx_tfm)) { 40 crypto_free_blkcipher(local->wep_tx_tfm); 41 return PTR_ERR(local->wep_rx_tfm); 42 } 43 44 return 0; 45 } 46 47 void ieee80211_wep_free(struct ieee80211_local *local) 48 { 49 crypto_free_blkcipher(local->wep_tx_tfm); 50 crypto_free_blkcipher(local->wep_rx_tfm); 51 } 52 53 static inline bool ieee80211_wep_weak_iv(u32 iv, int keylen) 54 { 55 /* 56 * Fluhrer, Mantin, and Shamir have reported weaknesses in the 57 * key scheduling algorithm of RC4. At least IVs (KeyByte + 3, 58 * 0xff, N) can be used to speedup attacks, so avoid using them. 59 */ 60 if ((iv & 0xff00) == 0xff00) { 61 u8 B = (iv >> 16) & 0xff; 62 if (B >= 3 && B < 3 + keylen) 63 return true; 64 } 65 return false; 66 } 67 68 69 static void ieee80211_wep_get_iv(struct ieee80211_local *local, 70 int keylen, int keyidx, u8 *iv) 71 { 72 local->wep_iv++; 73 if (ieee80211_wep_weak_iv(local->wep_iv, keylen)) 74 local->wep_iv += 0x0100; 75 76 if (!iv) 77 return; 78 79 *iv++ = (local->wep_iv >> 16) & 0xff; 80 *iv++ = (local->wep_iv >> 8) & 0xff; 81 *iv++ = local->wep_iv & 0xff; 82 *iv++ = keyidx << 6; 83 } 84 85 86 static u8 *ieee80211_wep_add_iv(struct ieee80211_local *local, 87 struct sk_buff *skb, 88 int keylen, int keyidx) 89 { 90 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data; 91 unsigned int hdrlen; 92 u8 *newhdr; 93 94 hdr->frame_control |= cpu_to_le16(IEEE80211_FCTL_PROTECTED); 95 96 if (WARN_ON(skb_tailroom(skb) < WEP_ICV_LEN || 97 skb_headroom(skb) < WEP_IV_LEN)) 98 return NULL; 99 100 hdrlen = ieee80211_hdrlen(hdr->frame_control); 101 newhdr = skb_push(skb, WEP_IV_LEN); 102 memmove(newhdr, newhdr + WEP_IV_LEN, hdrlen); 103 ieee80211_wep_get_iv(local, keylen, keyidx, newhdr + hdrlen); 104 return newhdr + hdrlen; 105 } 106 107 108 static void ieee80211_wep_remove_iv(struct ieee80211_local *local, 109 struct sk_buff *skb, 110 struct ieee80211_key *key) 111 { 112 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data; 113 unsigned int hdrlen; 114 115 hdrlen = ieee80211_hdrlen(hdr->frame_control); 116 memmove(skb->data + WEP_IV_LEN, skb->data, hdrlen); 117 skb_pull(skb, WEP_IV_LEN); 118 } 119 120 121 /* Perform WEP encryption using given key. data buffer must have tailroom 122 * for 4-byte ICV. data_len must not include this ICV. Note: this function 123 * does _not_ add IV. data = RC4(data | CRC32(data)) */ 124 void ieee80211_wep_encrypt_data(struct crypto_blkcipher *tfm, u8 *rc4key, 125 size_t klen, u8 *data, size_t data_len) 126 { 127 struct blkcipher_desc desc = { .tfm = tfm }; 128 struct scatterlist sg; 129 __le32 icv; 130 131 icv = cpu_to_le32(~crc32_le(~0, data, data_len)); 132 put_unaligned(icv, (__le32 *)(data + data_len)); 133 134 crypto_blkcipher_setkey(tfm, rc4key, klen); 135 sg_init_one(&sg, data, data_len + WEP_ICV_LEN); 136 crypto_blkcipher_encrypt(&desc, &sg, &sg, sg.length); 137 } 138 139 140 /* Perform WEP encryption on given skb. 4 bytes of extra space (IV) in the 141 * beginning of the buffer 4 bytes of extra space (ICV) in the end of the 142 * buffer will be added. Both IV and ICV will be transmitted, so the 143 * payload length increases with 8 bytes. 144 * 145 * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data)) 146 */ 147 int ieee80211_wep_encrypt(struct ieee80211_local *local, 148 struct sk_buff *skb, 149 const u8 *key, int keylen, int keyidx) 150 { 151 u8 *iv; 152 size_t len; 153 u8 rc4key[3 + WLAN_KEY_LEN_WEP104]; 154 155 iv = ieee80211_wep_add_iv(local, skb, keylen, keyidx); 156 if (!iv) 157 return -1; 158 159 len = skb->len - (iv + WEP_IV_LEN - skb->data); 160 161 /* Prepend 24-bit IV to RC4 key */ 162 memcpy(rc4key, iv, 3); 163 164 /* Copy rest of the WEP key (the secret part) */ 165 memcpy(rc4key + 3, key, keylen); 166 167 /* Add room for ICV */ 168 skb_put(skb, WEP_ICV_LEN); 169 170 ieee80211_wep_encrypt_data(local->wep_tx_tfm, rc4key, keylen + 3, 171 iv + WEP_IV_LEN, len); 172 173 return 0; 174 } 175 176 177 /* Perform WEP decryption using given key. data buffer includes encrypted 178 * payload, including 4-byte ICV, but _not_ IV. data_len must not include ICV. 179 * Return 0 on success and -1 on ICV mismatch. */ 180 int ieee80211_wep_decrypt_data(struct crypto_blkcipher *tfm, u8 *rc4key, 181 size_t klen, u8 *data, size_t data_len) 182 { 183 struct blkcipher_desc desc = { .tfm = tfm }; 184 struct scatterlist sg; 185 __le32 crc; 186 187 crypto_blkcipher_setkey(tfm, rc4key, klen); 188 sg_init_one(&sg, data, data_len + WEP_ICV_LEN); 189 crypto_blkcipher_decrypt(&desc, &sg, &sg, sg.length); 190 191 crc = cpu_to_le32(~crc32_le(~0, data, data_len)); 192 if (memcmp(&crc, data + data_len, WEP_ICV_LEN) != 0) 193 /* ICV mismatch */ 194 return -1; 195 196 return 0; 197 } 198 199 200 /* Perform WEP decryption on given skb. Buffer includes whole WEP part of 201 * the frame: IV (4 bytes), encrypted payload (including SNAP header), 202 * ICV (4 bytes). skb->len includes both IV and ICV. 203 * 204 * Returns 0 if frame was decrypted successfully and ICV was correct and -1 on 205 * failure. If frame is OK, IV and ICV will be removed, i.e., decrypted payload 206 * is moved to the beginning of the skb and skb length will be reduced. 207 */ 208 static int ieee80211_wep_decrypt(struct ieee80211_local *local, 209 struct sk_buff *skb, 210 struct ieee80211_key *key) 211 { 212 u32 klen; 213 u8 *rc4key; 214 u8 keyidx; 215 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data; 216 unsigned int hdrlen; 217 size_t len; 218 int ret = 0; 219 220 if (!ieee80211_has_protected(hdr->frame_control)) 221 return -1; 222 223 hdrlen = ieee80211_hdrlen(hdr->frame_control); 224 if (skb->len < hdrlen + WEP_IV_LEN + WEP_ICV_LEN) 225 return -1; 226 227 len = skb->len - hdrlen - WEP_IV_LEN - WEP_ICV_LEN; 228 229 keyidx = skb->data[hdrlen + 3] >> 6; 230 231 if (!key || keyidx != key->conf.keyidx || key->conf.alg != ALG_WEP) 232 return -1; 233 234 klen = 3 + key->conf.keylen; 235 236 rc4key = kmalloc(klen, GFP_ATOMIC); 237 if (!rc4key) 238 return -1; 239 240 /* Prepend 24-bit IV to RC4 key */ 241 memcpy(rc4key, skb->data + hdrlen, 3); 242 243 /* Copy rest of the WEP key (the secret part) */ 244 memcpy(rc4key + 3, key->conf.key, key->conf.keylen); 245 246 if (ieee80211_wep_decrypt_data(local->wep_rx_tfm, rc4key, klen, 247 skb->data + hdrlen + WEP_IV_LEN, 248 len)) 249 ret = -1; 250 251 kfree(rc4key); 252 253 /* Trim ICV */ 254 skb_trim(skb, skb->len - WEP_ICV_LEN); 255 256 /* Remove IV */ 257 memmove(skb->data + WEP_IV_LEN, skb->data, hdrlen); 258 skb_pull(skb, WEP_IV_LEN); 259 260 return ret; 261 } 262 263 264 bool ieee80211_wep_is_weak_iv(struct sk_buff *skb, struct ieee80211_key *key) 265 { 266 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data; 267 unsigned int hdrlen; 268 u8 *ivpos; 269 u32 iv; 270 271 if (!ieee80211_has_protected(hdr->frame_control)) 272 return false; 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; 287 288 if (!ieee80211_is_data(hdr->frame_control) && 289 !ieee80211_is_auth(hdr->frame_control)) 290 return RX_CONTINUE; 291 292 if (!(status->flag & RX_FLAG_DECRYPTED)) { 293 if (ieee80211_wep_decrypt(rx->local, rx->skb, rx->key)) 294 return RX_DROP_UNUSABLE; 295 } else if (!(status->flag & RX_FLAG_IV_STRIPPED)) { 296 ieee80211_wep_remove_iv(rx->local, rx->skb, rx->key); 297 /* remove ICV */ 298 skb_trim(rx->skb, rx->skb->len - WEP_ICV_LEN); 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); 307 308 if (!(tx->key->flags & KEY_FLAG_UPLOADED_TO_HARDWARE)) { 309 if (ieee80211_wep_encrypt(tx->local, skb, tx->key->conf.key, 310 tx->key->conf.keylen, 311 tx->key->conf.keyidx)) 312 return -1; 313 } else { 314 info->control.hw_key = &tx->key->conf; 315 if (tx->key->conf.flags & 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