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 <asm/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 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->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->keyidx << 6; 80 } 81 82 83 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 u16 fc; 89 int hdrlen; 90 u8 *newhdr; 91 92 fc = le16_to_cpu(hdr->frame_control); 93 fc |= IEEE80211_FCTL_PROTECTED; 94 hdr->frame_control = cpu_to_le16(fc); 95 96 if ((skb_headroom(skb) < WEP_IV_LEN || 97 skb_tailroom(skb) < WEP_ICV_LEN)) { 98 I802_DEBUG_INC(local->tx_expand_skb_head); 99 if (unlikely(pskb_expand_head(skb, WEP_IV_LEN, WEP_ICV_LEN, 100 GFP_ATOMIC))) 101 return NULL; 102 } 103 104 hdrlen = ieee80211_get_hdrlen(fc); 105 newhdr = skb_push(skb, WEP_IV_LEN); 106 memmove(newhdr, newhdr + WEP_IV_LEN, hdrlen); 107 ieee80211_wep_get_iv(local, key, newhdr + hdrlen); 108 return newhdr + hdrlen; 109 } 110 111 112 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 u16 fc; 118 int hdrlen; 119 120 fc = le16_to_cpu(hdr->frame_control); 121 hdrlen = ieee80211_get_hdrlen(fc); 122 memmove(skb->data + WEP_IV_LEN, skb->data, hdrlen); 123 skb_pull(skb, WEP_IV_LEN); 124 } 125 126 127 /* Perform WEP encryption using given key. data buffer must have tailroom 128 * for 4-byte ICV. data_len must not include this ICV. Note: this function 129 * does _not_ add IV. data = RC4(data | CRC32(data)) */ 130 void ieee80211_wep_encrypt_data(struct crypto_blkcipher *tfm, u8 *rc4key, 131 size_t klen, u8 *data, size_t data_len) 132 { 133 struct blkcipher_desc desc = { .tfm = tfm }; 134 struct scatterlist sg; 135 __le32 *icv; 136 137 icv = (__le32 *)(data + data_len); 138 *icv = cpu_to_le32(~crc32_le(~0, data, data_len)); 139 140 crypto_blkcipher_setkey(tfm, rc4key, klen); 141 sg.page = virt_to_page(data); 142 sg.offset = offset_in_page(data); 143 sg.length = data_len + WEP_ICV_LEN; 144 crypto_blkcipher_encrypt(&desc, &sg, &sg, sg.length); 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, struct sk_buff *skb, 156 struct ieee80211_key *key) 157 { 158 u32 klen; 159 u8 *rc4key, *iv; 160 size_t len; 161 162 if (!key || key->alg != ALG_WEP) 163 return -1; 164 165 klen = 3 + key->keylen; 166 rc4key = kmalloc(klen, GFP_ATOMIC); 167 if (!rc4key) 168 return -1; 169 170 iv = ieee80211_wep_add_iv(local, skb, key); 171 if (!iv) { 172 kfree(rc4key); 173 return -1; 174 } 175 176 len = skb->len - (iv + 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->key, key->keylen); 183 184 /* Add room for ICV */ 185 skb_put(skb, WEP_ICV_LEN); 186 187 ieee80211_wep_encrypt_data(local->wep_tx_tfm, rc4key, klen, 188 iv + WEP_IV_LEN, len); 189 190 kfree(rc4key); 191 192 return 0; 193 } 194 195 196 /* Perform WEP decryption using given key. data buffer includes encrypted 197 * payload, including 4-byte ICV, but _not_ IV. data_len must not include ICV. 198 * Return 0 on success and -1 on ICV mismatch. */ 199 int ieee80211_wep_decrypt_data(struct crypto_blkcipher *tfm, u8 *rc4key, 200 size_t klen, u8 *data, size_t data_len) 201 { 202 struct blkcipher_desc desc = { .tfm = tfm }; 203 struct scatterlist sg; 204 __le32 crc; 205 206 crypto_blkcipher_setkey(tfm, rc4key, klen); 207 sg.page = virt_to_page(data); 208 sg.offset = offset_in_page(data); 209 sg.length = data_len + WEP_ICV_LEN; 210 crypto_blkcipher_decrypt(&desc, &sg, &sg, sg.length); 211 212 crc = cpu_to_le32(~crc32_le(~0, data, data_len)); 213 if (memcmp(&crc, data + data_len, WEP_ICV_LEN) != 0) 214 /* ICV mismatch */ 215 return -1; 216 217 return 0; 218 } 219 220 221 /* Perform WEP decryption on given skb. Buffer includes whole WEP part of 222 * the frame: IV (4 bytes), encrypted payload (including SNAP header), 223 * ICV (4 bytes). skb->len includes both IV and ICV. 224 * 225 * Returns 0 if frame was decrypted successfully and ICV was correct and -1 on 226 * failure. If frame is OK, IV and ICV will be removed, i.e., decrypted payload 227 * is moved to the beginning of the skb and skb length will be reduced. 228 */ 229 int ieee80211_wep_decrypt(struct ieee80211_local *local, struct sk_buff *skb, 230 struct ieee80211_key *key) 231 { 232 u32 klen; 233 u8 *rc4key; 234 u8 keyidx; 235 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data; 236 u16 fc; 237 int hdrlen; 238 size_t len; 239 int ret = 0; 240 241 fc = le16_to_cpu(hdr->frame_control); 242 if (!(fc & IEEE80211_FCTL_PROTECTED)) 243 return -1; 244 245 hdrlen = ieee80211_get_hdrlen(fc); 246 247 if (skb->len < 8 + hdrlen) 248 return -1; 249 250 len = skb->len - hdrlen - 8; 251 252 keyidx = skb->data[hdrlen + 3] >> 6; 253 254 if (!key || keyidx != key->keyidx || key->alg != ALG_WEP) 255 return -1; 256 257 klen = 3 + key->keylen; 258 259 rc4key = kmalloc(klen, GFP_ATOMIC); 260 if (!rc4key) 261 return -1; 262 263 /* Prepend 24-bit IV to RC4 key */ 264 memcpy(rc4key, skb->data + hdrlen, 3); 265 266 /* Copy rest of the WEP key (the secret part) */ 267 memcpy(rc4key + 3, key->key, key->keylen); 268 269 if (ieee80211_wep_decrypt_data(local->wep_rx_tfm, rc4key, klen, 270 skb->data + hdrlen + WEP_IV_LEN, 271 len)) { 272 printk(KERN_DEBUG "WEP decrypt failed (ICV)\n"); 273 ret = -1; 274 } 275 276 kfree(rc4key); 277 278 /* Trim ICV */ 279 skb_trim(skb, skb->len - WEP_ICV_LEN); 280 281 /* Remove IV */ 282 memmove(skb->data + WEP_IV_LEN, skb->data, hdrlen); 283 skb_pull(skb, WEP_IV_LEN); 284 285 return ret; 286 } 287 288 289 int ieee80211_wep_get_keyidx(struct sk_buff *skb) 290 { 291 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data; 292 u16 fc; 293 int hdrlen; 294 295 fc = le16_to_cpu(hdr->frame_control); 296 if (!(fc & IEEE80211_FCTL_PROTECTED)) 297 return -1; 298 299 hdrlen = ieee80211_get_hdrlen(fc); 300 301 if (skb->len < 8 + hdrlen) 302 return -1; 303 304 return skb->data[hdrlen + 3] >> 6; 305 } 306 307 308 u8 * ieee80211_wep_is_weak_iv(struct sk_buff *skb, struct ieee80211_key *key) 309 { 310 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data; 311 u16 fc; 312 int hdrlen; 313 u8 *ivpos; 314 u32 iv; 315 316 fc = le16_to_cpu(hdr->frame_control); 317 if (!(fc & IEEE80211_FCTL_PROTECTED)) 318 return NULL; 319 320 hdrlen = ieee80211_get_hdrlen(fc); 321 ivpos = skb->data + hdrlen; 322 iv = (ivpos[0] << 16) | (ivpos[1] << 8) | ivpos[2]; 323 324 if (ieee80211_wep_weak_iv(iv, key->keylen)) 325 return ivpos; 326 327 return NULL; 328 } 329