wep.c
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00001 /*
00002  * Software WEP encryption implementation
00003  * Copyright 2002, Jouni Malinen <jkmaline@cc.hut.fi>
00004  * Copyright 2003, Instant802 Networks, Inc.
00005  *
00006  * This program is free software; you can redistribute it and/or modify
00007  * it under the terms of the GNU General Public License version 2 as
00008  * published by the Free Software Foundation.
00009  */
00010 
00011 #include <linux/netdevice.h>
00012 #include <linux/types.h>
00013 #include <linux/random.h>
00014 #include <linux/compiler.h>
00015 #include <linux/crc32.h>
00016 #include <linux/crypto.h>
00017 #include <linux/err.h>
00018 #include <linux/mm.h>
00019 #include <linux/scatterlist.h>
00020 #include <linux/slab.h>
00021 #include <asm/unaligned.h>
00022 
00023 #include <net/mac80211.h>
00024 #include "ieee80211_i.h"
00025 #include "wep.h"
00026 
00027 
00028 int ieee80211_wep_init(struct ieee80211_local *local)
00029 {
00030         /* start WEP IV from a random value */
00031         get_random_bytes(&local->wep_iv, WEP_IV_LEN);
00032 
00033         local->wep_tx_tfm = crypto_alloc_cipher("arc4", 0, CRYPTO_ALG_ASYNC);
00034         if (IS_ERR(local->wep_tx_tfm)) {
00035                 local->wep_rx_tfm = ERR_PTR(-EINVAL);
00036                 return PTR_ERR(local->wep_tx_tfm);
00037         }
00038 
00039         local->wep_rx_tfm = crypto_alloc_cipher("arc4", 0, CRYPTO_ALG_ASYNC);
00040         if (IS_ERR(local->wep_rx_tfm)) {
00041                 crypto_free_cipher(local->wep_tx_tfm);
00042                 local->wep_tx_tfm = ERR_PTR(-EINVAL);
00043                 return PTR_ERR(local->wep_rx_tfm);
00044         }
00045 
00046         return 0;
00047 }
00048 
00049 void ieee80211_wep_free(struct ieee80211_local *local)
00050 {
00051         if (!IS_ERR(local->wep_tx_tfm))
00052                 crypto_free_cipher(local->wep_tx_tfm);
00053         if (!IS_ERR(local->wep_rx_tfm))
00054                 crypto_free_cipher(local->wep_rx_tfm);
00055 }
00056 
00057 static inline bool ieee80211_wep_weak_iv(u32 iv, int keylen)
00058 {
00059         /*
00060          * Fluhrer, Mantin, and Shamir have reported weaknesses in the
00061          * key scheduling algorithm of RC4. At least IVs (KeyByte + 3,
00062          * 0xff, N) can be used to speedup attacks, so avoid using them.
00063          */
00064         if ((iv & 0xff00) == 0xff00) {
00065                 u8 B = (iv >> 16) & 0xff;
00066                 if (B >= 3 && B < 3 + keylen)
00067                         return true;
00068         }
00069         return false;
00070 }
00071 
00072 
00073 static void ieee80211_wep_get_iv(struct ieee80211_local *local,
00074                                  int keylen, int keyidx, u8 *iv)
00075 {
00076         local->wep_iv++;
00077         if (ieee80211_wep_weak_iv(local->wep_iv, keylen))
00078                 local->wep_iv += 0x0100;
00079 
00080         if (!iv)
00081                 return;
00082 
00083         *iv++ = (local->wep_iv >> 16) & 0xff;
00084         *iv++ = (local->wep_iv >> 8) & 0xff;
00085         *iv++ = local->wep_iv & 0xff;
00086         *iv++ = keyidx << 6;
00087 }
00088 
00089 
00090 static u8 *ieee80211_wep_add_iv(struct ieee80211_local *local,
00091                                 struct sk_buff *skb,
00092                                 int keylen, int keyidx)
00093 {
00094         struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
00095         unsigned int hdrlen;
00096         u8 *newhdr;
00097 
00098         hdr->frame_control |= cpu_to_le16(IEEE80211_FCTL_PROTECTED);
00099 
00100         if (WARN_ON(skb_tailroom(skb) < WEP_ICV_LEN ||
00101                     skb_headroom(skb) < WEP_IV_LEN))
00102                 return NULL;
00103 
00104         hdrlen = ieee80211_hdrlen(hdr->frame_control);
00105         newhdr = skb_push(skb, WEP_IV_LEN);
00106         memmove(newhdr, newhdr + WEP_IV_LEN, hdrlen);
00107         ieee80211_wep_get_iv(local, keylen, keyidx, newhdr + hdrlen);
00108         return newhdr + hdrlen;
00109 }
00110 
00111 
00112 static void ieee80211_wep_remove_iv(struct ieee80211_local *local,
00113                                     struct sk_buff *skb,
00114                                     struct ieee80211_key *key)
00115 {
00116         struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
00117         unsigned int hdrlen;
00118 
00119         hdrlen = ieee80211_hdrlen(hdr->frame_control);
00120         memmove(skb->data + WEP_IV_LEN, skb->data, hdrlen);
00121         skb_pull(skb, WEP_IV_LEN);
00122 }
00123 
00124 
00125 /* Perform WEP encryption using given key. data buffer must have tailroom
00126  * for 4-byte ICV. data_len must not include this ICV. Note: this function
00127  * does _not_ add IV. data = RC4(data | CRC32(data)) */
00128 int ieee80211_wep_encrypt_data(struct crypto_cipher *tfm, u8 *rc4key,
00129                                size_t klen, u8 *data, size_t data_len)
00130 {
00131         __le32 icv;
00132         int i;
00133 
00134         if (IS_ERR(tfm))
00135                 return -1;
00136 
00137         icv = cpu_to_le32(~crc32_le(~0, data, data_len));
00138         put_unaligned(icv, (__le32 *)(data + data_len));
00139 
00140         crypto_cipher_setkey(tfm, rc4key, klen);
00141         for (i = 0; i < data_len + WEP_ICV_LEN; i++)
00142                 crypto_cipher_encrypt_one(tfm, data + i, data + i);
00143 
00144         return 0;
00145 }
00146 
00147 
00148 /* Perform WEP encryption on given skb. 4 bytes of extra space (IV) in the
00149  * beginning of the buffer 4 bytes of extra space (ICV) in the end of the
00150  * buffer will be added. Both IV and ICV will be transmitted, so the
00151  * payload length increases with 8 bytes.
00152  *
00153  * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data))
00154  */
00155 int ieee80211_wep_encrypt(struct ieee80211_local *local,
00156                           struct sk_buff *skb,
00157                           const u8 *key, int keylen, int keyidx)
00158 {
00159         u8 *iv;
00160         size_t len;
00161         u8 rc4key[3 + WLAN_KEY_LEN_WEP104];
00162 
00163         iv = ieee80211_wep_add_iv(local, skb, keylen, keyidx);
00164         if (!iv)
00165                 return -1;
00166 
00167         len = skb->len - (iv + WEP_IV_LEN - skb->data);
00168 
00169         /* Prepend 24-bit IV to RC4 key */
00170         memcpy(rc4key, iv, 3);
00171 
00172         /* Copy rest of the WEP key (the secret part) */
00173         memcpy(rc4key + 3, key, keylen);
00174 
00175         /* Add room for ICV */
00176         skb_put(skb, WEP_ICV_LEN);
00177 
00178         return ieee80211_wep_encrypt_data(local->wep_tx_tfm, rc4key, keylen + 3,
00179                                           iv + WEP_IV_LEN, len);
00180 }
00181 
00182 
00183 /* Perform WEP decryption using given key. data buffer includes encrypted
00184  * payload, including 4-byte ICV, but _not_ IV. data_len must not include ICV.
00185  * Return 0 on success and -1 on ICV mismatch. */
00186 int ieee80211_wep_decrypt_data(struct crypto_cipher *tfm, u8 *rc4key,
00187                                size_t klen, u8 *data, size_t data_len)
00188 {
00189         __le32 crc;
00190         int i;
00191 
00192         if (IS_ERR(tfm))
00193                 return -1;
00194 
00195         crypto_cipher_setkey(tfm, rc4key, klen);
00196         for (i = 0; i < data_len + WEP_ICV_LEN; i++)
00197                 crypto_cipher_decrypt_one(tfm, data + i, data + i);
00198 
00199         crc = cpu_to_le32(~crc32_le(~0, data, data_len));
00200         if (memcmp(&crc, data + data_len, WEP_ICV_LEN) != 0)
00201                 /* ICV mismatch */
00202                 return -1;
00203 
00204         return 0;
00205 }
00206 
00207 
00208 /* Perform WEP decryption on given skb. Buffer includes whole WEP part of
00209  * the frame: IV (4 bytes), encrypted payload (including SNAP header),
00210  * ICV (4 bytes). skb->len includes both IV and ICV.
00211  *
00212  * Returns 0 if frame was decrypted successfully and ICV was correct and -1 on
00213  * failure. If frame is OK, IV and ICV will be removed, i.e., decrypted payload
00214  * is moved to the beginning of the skb and skb length will be reduced.
00215  */
00216 static int ieee80211_wep_decrypt(struct ieee80211_local *local,
00217                                  struct sk_buff *skb,
00218                                  struct ieee80211_key *key)
00219 {
00220         u32 klen;
00221         u8 rc4key[3 + WLAN_KEY_LEN_WEP104];
00222         u8 keyidx;
00223         struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
00224         unsigned int hdrlen;
00225         size_t len;
00226         int ret = 0;
00227 
00228         if (!ieee80211_has_protected(hdr->frame_control))
00229                 return -1;
00230 
00231         hdrlen = ieee80211_hdrlen(hdr->frame_control);
00232         if (skb->len < hdrlen + WEP_IV_LEN + WEP_ICV_LEN)
00233                 return -1;
00234 
00235         len = skb->len - hdrlen - WEP_IV_LEN - WEP_ICV_LEN;
00236 
00237         keyidx = skb->data[hdrlen + 3] >> 6;
00238 
00239         if (!key || keyidx != key->conf.keyidx)
00240                 return -1;
00241 
00242         klen = 3 + key->conf.keylen;
00243 
00244         /* Prepend 24-bit IV to RC4 key */
00245         memcpy(rc4key, skb->data + hdrlen, 3);
00246 
00247         /* Copy rest of the WEP key (the secret part) */
00248         memcpy(rc4key + 3, key->conf.key, key->conf.keylen);
00249 
00250         if (ieee80211_wep_decrypt_data(local->wep_rx_tfm, rc4key, klen,
00251                                        skb->data + hdrlen + WEP_IV_LEN,
00252                                        len))
00253                 ret = -1;
00254 
00255         /* Trim ICV */
00256         skb_trim(skb, skb->len - WEP_ICV_LEN);
00257 
00258         /* Remove IV */
00259         memmove(skb->data + WEP_IV_LEN, skb->data, hdrlen);
00260         skb_pull(skb, WEP_IV_LEN);
00261 
00262         return ret;
00263 }
00264 
00265 
00266 bool ieee80211_wep_is_weak_iv(struct sk_buff *skb, struct ieee80211_key *key)
00267 {
00268         struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
00269         unsigned int hdrlen;
00270         u8 *ivpos;
00271         u32 iv;
00272 
00273         if (!ieee80211_has_protected(hdr->frame_control))
00274                 return false;
00275 
00276         hdrlen = ieee80211_hdrlen(hdr->frame_control);
00277         ivpos = skb->data + hdrlen;
00278         iv = (ivpos[0] << 16) | (ivpos[1] << 8) | ivpos[2];
00279 
00280         return ieee80211_wep_weak_iv(iv, key->conf.keylen);
00281 }
00282 
00283 ieee80211_rx_result
00284 ieee80211_crypto_wep_decrypt(struct ieee80211_rx_data *rx)
00285 {
00286         struct sk_buff *skb = rx->skb;
00287         struct ieee80211_rx_status *status = IEEE80211_SKB_RXCB(skb);
00288         struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
00289 
00290         if (!ieee80211_is_data(hdr->frame_control) &&
00291             !ieee80211_is_auth(hdr->frame_control))
00292                 return RX_CONTINUE;
00293 
00294         if (!(status->flag & RX_FLAG_DECRYPTED)) {
00295                 if (ieee80211_wep_decrypt(rx->local, rx->skb, rx->key))
00296                         return RX_DROP_UNUSABLE;
00297         } else if (!(status->flag & RX_FLAG_IV_STRIPPED)) {
00298                 ieee80211_wep_remove_iv(rx->local, rx->skb, rx->key);
00299                 /* remove ICV */
00300                 skb_trim(rx->skb, rx->skb->len - WEP_ICV_LEN);
00301         }
00302 
00303         return RX_CONTINUE;
00304 }
00305 
00306 static int wep_encrypt_skb(struct ieee80211_tx_data *tx, struct sk_buff *skb)
00307 {
00308         struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
00309 
00310         if (!info->control.hw_key) {
00311                 if (ieee80211_wep_encrypt(tx->local, skb, tx->key->conf.key,
00312                                           tx->key->conf.keylen,
00313                                           tx->key->conf.keyidx))
00314                         return -1;
00315         } else if (info->control.hw_key->flags &
00316                         IEEE80211_KEY_FLAG_GENERATE_IV) {
00317                 if (!ieee80211_wep_add_iv(tx->local, skb,
00318                                           tx->key->conf.keylen,
00319                                           tx->key->conf.keyidx))
00320                         return -1;
00321         }
00322 
00323         return 0;
00324 }
00325 
00326 ieee80211_tx_result
00327 ieee80211_crypto_wep_encrypt(struct ieee80211_tx_data *tx)
00328 {
00329         struct sk_buff *skb;
00330 
00331         ieee80211_tx_set_protected(tx);
00332 
00333         skb = tx->skb;
00334         do {
00335                 if (wep_encrypt_skb(tx, skb) < 0) {
00336                         I802_DEBUG_INC(tx->local->tx_handlers_drop_wep);
00337                         return TX_DROP;
00338                 }
00339         } while ((skb = skb->next));
00340 
00341         return TX_CONTINUE;
00342 }


ros_rt_wmp
Author(s): Danilo Tardioli, dantard@unizar.es
autogenerated on Fri Jan 3 2014 12:07:56