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 21 #include <net/mac80211.h> 22 #include "ieee80211_i.h" 23 #include "wep.h" 24 25 26 int ieee80211_wep_init(struct ieee80211_local *local) 27 { 28 /* start WEP IV from a random value */ 29 get_random_bytes(&local->wep_iv, WEP_IV_LEN); 30 31 local->wep_tx_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0, 32 CRYPTO_ALG_ASYNC); 33 if (IS_ERR(local->wep_tx_tfm)) 34 return -ENOMEM; 35 36 local->wep_rx_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0, 37 CRYPTO_ALG_ASYNC); 38 if (IS_ERR(local->wep_rx_tfm)) { 39 crypto_free_blkcipher(local->wep_tx_tfm); 40 return -ENOMEM; 41 } 42 43 return 0; 44 } 45 46 void ieee80211_wep_free(struct ieee80211_local *local) 47 { 48 crypto_free_blkcipher(local->wep_tx_tfm); 49 crypto_free_blkcipher(local->wep_rx_tfm); 50 } 51 52 static inline int ieee80211_wep_weak_iv(u32 iv, int keylen) 53 { 54 /* Fluhrer, Mantin, and Shamir have reported weaknesses in the 55 * key scheduling algorithm of RC4. At least IVs (KeyByte + 3, 56 * 0xff, N) can be used to speedup attacks, so avoid using them. */ 57 if ((iv & 0xff00) == 0xff00) { 58 u8 B = (iv >> 16) & 0xff; 59 if (B >= 3 && B < 3 + keylen) 60 return 1; 61 } 62 return 0; 63 } 64 65 66 static void ieee80211_wep_get_iv(struct ieee80211_local *local, 67 struct ieee80211_key *key, u8 *iv) 68 { 69 local->wep_iv++; 70 if (ieee80211_wep_weak_iv(local->wep_iv, key->conf.keylen)) 71 local->wep_iv += 0x0100; 72 73 if (!iv) 74 return; 75 76 *iv++ = (local->wep_iv >> 16) & 0xff; 77 *iv++ = (local->wep_iv >> 8) & 0xff; 78 *iv++ = local->wep_iv & 0xff; 79 *iv++ = key->conf.keyidx << 6; 80 } 81 82 83 static u8 *ieee80211_wep_add_iv(struct ieee80211_local *local, 84 struct sk_buff *skb, 85 struct ieee80211_key *key) 86 { 87 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data; 88 unsigned int hdrlen; 89 u8 *newhdr; 90 91 hdr->frame_control |= cpu_to_le16(IEEE80211_FCTL_PROTECTED); 92 93 if (WARN_ON(skb_tailroom(skb) < WEP_ICV_LEN || 94 skb_headroom(skb) < WEP_IV_LEN)) 95 return NULL; 96 97 hdrlen = ieee80211_hdrlen(hdr->frame_control); 98 newhdr = skb_push(skb, WEP_IV_LEN); 99 memmove(newhdr, newhdr + WEP_IV_LEN, hdrlen); 100 ieee80211_wep_get_iv(local, key, newhdr + hdrlen); 101 return newhdr + hdrlen; 102 } 103 104 105 static void ieee80211_wep_remove_iv(struct ieee80211_local *local, 106 struct sk_buff *skb, 107 struct ieee80211_key *key) 108 { 109 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data; 110 unsigned int hdrlen; 111 112 hdrlen = ieee80211_hdrlen(hdr->frame_control); 113 memmove(skb->data + WEP_IV_LEN, skb->data, hdrlen); 114 skb_pull(skb, WEP_IV_LEN); 115 } 116 117 118 /* Perform WEP encryption using given key. data buffer must have tailroom 119 * for 4-byte ICV. data_len must not include this ICV. Note: this function 120 * does _not_ add IV. data = RC4(data | CRC32(data)) */ 121 void ieee80211_wep_encrypt_data(struct crypto_blkcipher *tfm, u8 *rc4key, 122 size_t klen, u8 *data, size_t data_len) 123 { 124 struct blkcipher_desc desc = { .tfm = tfm }; 125 struct scatterlist sg; 126 __le32 *icv; 127 128 icv = (__le32 *)(data + data_len); 129 *icv = cpu_to_le32(~crc32_le(~0, data, data_len)); 130 131 crypto_blkcipher_setkey(tfm, rc4key, klen); 132 sg_init_one(&sg, data, data_len + WEP_ICV_LEN); 133 crypto_blkcipher_encrypt(&desc, &sg, &sg, sg.length); 134 } 135 136 137 /* Perform WEP encryption on given skb. 4 bytes of extra space (IV) in the 138 * beginning of the buffer 4 bytes of extra space (ICV) in the end of the 139 * buffer will be added. Both IV and ICV will be transmitted, so the 140 * payload length increases with 8 bytes. 141 * 142 * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data)) 143 */ 144 int ieee80211_wep_encrypt(struct ieee80211_local *local, struct sk_buff *skb, 145 struct ieee80211_key *key) 146 { 147 u32 klen; 148 u8 *rc4key, *iv; 149 size_t len; 150 151 if (!key || key->conf.alg != ALG_WEP) 152 return -1; 153 154 klen = 3 + key->conf.keylen; 155 rc4key = kmalloc(klen, GFP_ATOMIC); 156 if (!rc4key) 157 return -1; 158 159 iv = ieee80211_wep_add_iv(local, skb, key); 160 if (!iv) { 161 kfree(rc4key); 162 return -1; 163 } 164 165 len = skb->len - (iv + WEP_IV_LEN - skb->data); 166 167 /* Prepend 24-bit IV to RC4 key */ 168 memcpy(rc4key, iv, 3); 169 170 /* Copy rest of the WEP key (the secret part) */ 171 memcpy(rc4key + 3, key->conf.key, key->conf.keylen); 172 173 /* Add room for ICV */ 174 skb_put(skb, WEP_ICV_LEN); 175 176 ieee80211_wep_encrypt_data(local->wep_tx_tfm, rc4key, klen, 177 iv + WEP_IV_LEN, len); 178 179 kfree(rc4key); 180 181 return 0; 182 } 183 184 185 /* Perform WEP decryption using given key. data buffer includes encrypted 186 * payload, including 4-byte ICV, but _not_ IV. data_len must not include ICV. 187 * Return 0 on success and -1 on ICV mismatch. */ 188 int ieee80211_wep_decrypt_data(struct crypto_blkcipher *tfm, u8 *rc4key, 189 size_t klen, u8 *data, size_t data_len) 190 { 191 struct blkcipher_desc desc = { .tfm = tfm }; 192 struct scatterlist sg; 193 __le32 crc; 194 195 crypto_blkcipher_setkey(tfm, rc4key, klen); 196 sg_init_one(&sg, data, data_len + WEP_ICV_LEN); 197 crypto_blkcipher_decrypt(&desc, &sg, &sg, sg.length); 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 int ieee80211_wep_decrypt(struct ieee80211_local *local, struct sk_buff *skb, 217 struct ieee80211_key *key) 218 { 219 u32 klen; 220 u8 *rc4key; 221 u8 keyidx; 222 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data; 223 unsigned int hdrlen; 224 size_t len; 225 int ret = 0; 226 227 if (!ieee80211_has_protected(hdr->frame_control)) 228 return -1; 229 230 hdrlen = ieee80211_hdrlen(hdr->frame_control); 231 232 if (skb->len < 8 + hdrlen) 233 return -1; 234 235 len = skb->len - hdrlen - 8; 236 237 keyidx = skb->data[hdrlen + 3] >> 6; 238 239 if (!key || keyidx != key->conf.keyidx || key->conf.alg != ALG_WEP) 240 return -1; 241 242 klen = 3 + key->conf.keylen; 243 244 rc4key = kmalloc(klen, GFP_ATOMIC); 245 if (!rc4key) 246 return -1; 247 248 /* Prepend 24-bit IV to RC4 key */ 249 memcpy(rc4key, skb->data + hdrlen, 3); 250 251 /* Copy rest of the WEP key (the secret part) */ 252 memcpy(rc4key + 3, key->conf.key, key->conf.keylen); 253 254 if (ieee80211_wep_decrypt_data(local->wep_rx_tfm, rc4key, klen, 255 skb->data + hdrlen + WEP_IV_LEN, 256 len)) 257 ret = -1; 258 259 kfree(rc4key); 260 261 /* Trim ICV */ 262 skb_trim(skb, skb->len - WEP_ICV_LEN); 263 264 /* Remove IV */ 265 memmove(skb->data + WEP_IV_LEN, skb->data, hdrlen); 266 skb_pull(skb, WEP_IV_LEN); 267 268 return ret; 269 } 270 271 272 u8 * ieee80211_wep_is_weak_iv(struct sk_buff *skb, struct ieee80211_key *key) 273 { 274 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data; 275 unsigned int hdrlen; 276 u8 *ivpos; 277 u32 iv; 278 279 if (!ieee80211_has_protected(hdr->frame_control)) 280 return NULL; 281 282 hdrlen = ieee80211_hdrlen(hdr->frame_control); 283 ivpos = skb->data + hdrlen; 284 iv = (ivpos[0] << 16) | (ivpos[1] << 8) | ivpos[2]; 285 286 if (ieee80211_wep_weak_iv(iv, key->conf.keylen)) 287 return ivpos; 288 289 return NULL; 290 } 291 292 ieee80211_rx_result 293 ieee80211_crypto_wep_decrypt(struct ieee80211_rx_data *rx) 294 { 295 if ((rx->fc & IEEE80211_FCTL_FTYPE) != IEEE80211_FTYPE_DATA && 296 ((rx->fc & IEEE80211_FCTL_FTYPE) != IEEE80211_FTYPE_MGMT || 297 (rx->fc & IEEE80211_FCTL_STYPE) != IEEE80211_STYPE_AUTH)) 298 return RX_CONTINUE; 299 300 if (!(rx->status->flag & RX_FLAG_DECRYPTED)) { 301 if (ieee80211_wep_decrypt(rx->local, rx->skb, rx->key)) 302 return RX_DROP_UNUSABLE; 303 } else if (!(rx->status->flag & RX_FLAG_IV_STRIPPED)) { 304 ieee80211_wep_remove_iv(rx->local, rx->skb, rx->key); 305 /* remove ICV */ 306 skb_trim(rx->skb, rx->skb->len - 4); 307 } 308 309 return RX_CONTINUE; 310 } 311 312 static int wep_encrypt_skb(struct ieee80211_tx_data *tx, struct sk_buff *skb) 313 { 314 struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb); 315 316 info->control.iv_len = WEP_IV_LEN; 317 info->control.icv_len = WEP_ICV_LEN; 318 319 if (!(tx->key->flags & KEY_FLAG_UPLOADED_TO_HARDWARE)) { 320 if (ieee80211_wep_encrypt(tx->local, skb, tx->key)) 321 return -1; 322 } else { 323 info->control.hw_key = &tx->key->conf; 324 if (tx->key->conf.flags & IEEE80211_KEY_FLAG_GENERATE_IV) { 325 if (!ieee80211_wep_add_iv(tx->local, skb, tx->key)) 326 return -1; 327 } 328 } 329 return 0; 330 } 331 332 ieee80211_tx_result 333 ieee80211_crypto_wep_encrypt(struct ieee80211_tx_data *tx) 334 { 335 ieee80211_tx_set_protected(tx); 336 337 if (wep_encrypt_skb(tx, tx->skb) < 0) { 338 I802_DEBUG_INC(tx->local->tx_handlers_drop_wep); 339 return TX_DROP; 340 } 341 342 if (tx->extra_frag) { 343 int i; 344 for (i = 0; i < tx->num_extra_frag; i++) { 345 if (wep_encrypt_skb(tx, tx->extra_frag[i]) < 0) { 346 I802_DEBUG_INC(tx->local-> 347 tx_handlers_drop_wep); 348 return TX_DROP; 349 } 350 } 351 } 352 353 return TX_CONTINUE; 354 } 355