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/*
* Software WEP encryption implementation
* Copyright 2002, Jouni Malinen <jkmaline@cc.hut.fi>
* Copyright 2003, Instant802 Networks, Inc.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/netdevice.h>
#include <linux/types.h>
#include <linux/random.h>
#include <linux/compiler.h>
#include <linux/crc32.h>
#include <linux/crypto.h>
#include <linux/err.h>
#include <linux/mm.h>
#include <linux/scatterlist.h>
#include <linux/slab.h>
#include <asm/unaligned.h>
#include <net/mac80211.h>
#include "ieee80211_i.h"
#include "wep.h"
int ieee80211_wep_init(struct ieee80211_local *local)
{
/* start WEP IV from a random value */
get_random_bytes(&local->wep_iv, WEP_IV_LEN);
local->wep_tx_tfm = crypto_alloc_cipher("arc4", 0, CRYPTO_ALG_ASYNC);
if (IS_ERR(local->wep_tx_tfm)) {
local->wep_rx_tfm = ERR_PTR(-EINVAL);
return PTR_ERR(local->wep_tx_tfm);
}
local->wep_rx_tfm = crypto_alloc_cipher("arc4", 0, CRYPTO_ALG_ASYNC);
if (IS_ERR(local->wep_rx_tfm)) {
crypto_free_cipher(local->wep_tx_tfm);
local->wep_tx_tfm = ERR_PTR(-EINVAL);
return PTR_ERR(local->wep_rx_tfm);
}
return 0;
}
void ieee80211_wep_free(struct ieee80211_local *local)
{
if (!IS_ERR(local->wep_tx_tfm))
crypto_free_cipher(local->wep_tx_tfm);
if (!IS_ERR(local->wep_rx_tfm))
crypto_free_cipher(local->wep_rx_tfm);
}
static inline bool ieee80211_wep_weak_iv(u32 iv, int keylen)
{
/*
* Fluhrer, Mantin, and Shamir have reported weaknesses in the
* key scheduling algorithm of RC4. At least IVs (KeyByte + 3,
* 0xff, N) can be used to speedup attacks, so avoid using them.
*/
if ((iv & 0xff00) == 0xff00) {
u8 B = (iv >> 16) & 0xff;
if (B >= 3 && B < 3 + keylen)
return true;
}
return false;
}
static void ieee80211_wep_get_iv(struct ieee80211_local *local,
int keylen, int keyidx, u8 *iv)
{
local->wep_iv++;
if (ieee80211_wep_weak_iv(local->wep_iv, keylen))
local->wep_iv += 0x0100;
if (!iv)
return;
*iv++ = (local->wep_iv >> 16) & 0xff;
*iv++ = (local->wep_iv >> 8) & 0xff;
*iv++ = local->wep_iv & 0xff;
*iv++ = keyidx << 6;
}
static u8 *ieee80211_wep_add_iv(struct ieee80211_local *local,
struct sk_buff *skb,
int keylen, int keyidx)
{
struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
unsigned int hdrlen;
u8 *newhdr;
hdr->frame_control |= cpu_to_le16(IEEE80211_FCTL_PROTECTED);
if (WARN_ON(skb_tailroom(skb) < WEP_ICV_LEN ||
skb_headroom(skb) < WEP_IV_LEN))
return NULL;
hdrlen = ieee80211_hdrlen(hdr->frame_control);
newhdr = skb_push(skb, WEP_IV_LEN);
memmove(newhdr, newhdr + WEP_IV_LEN, hdrlen);
ieee80211_wep_get_iv(local, keylen, keyidx, newhdr + hdrlen);
return newhdr + hdrlen;
}
static void ieee80211_wep_remove_iv(struct ieee80211_local *local,
struct sk_buff *skb,
struct ieee80211_key *key)
{
struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
unsigned int hdrlen;
hdrlen = ieee80211_hdrlen(hdr->frame_control);
memmove(skb->data + WEP_IV_LEN, skb->data, hdrlen);
skb_pull(skb, WEP_IV_LEN);
}
/* Perform WEP encryption using given key. data buffer must have tailroom
* for 4-byte ICV. data_len must not include this ICV. Note: this function
* does _not_ add IV. data = RC4(data | CRC32(data)) */
int ieee80211_wep_encrypt_data(struct crypto_cipher *tfm, u8 *rc4key,
size_t klen, u8 *data, size_t data_len)
{
__le32 icv;
int i;
if (IS_ERR(tfm))
return -1;
icv = cpu_to_le32(~crc32_le(~0, data, data_len));
put_unaligned(icv, (__le32 *)(data + data_len));
crypto_cipher_setkey(tfm, rc4key, klen);
for (i = 0; i < data_len + WEP_ICV_LEN; i++)
crypto_cipher_encrypt_one(tfm, data + i, data + i);
return 0;
}
/* Perform WEP encryption on given skb. 4 bytes of extra space (IV) in the
* beginning of the buffer 4 bytes of extra space (ICV) in the end of the
* buffer will be added. Both IV and ICV will be transmitted, so the
* payload length increases with 8 bytes.
*
* WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data))
*/
int ieee80211_wep_encrypt(struct ieee80211_local *local,
struct sk_buff *skb,
const u8 *key, int keylen, int keyidx)
{
u8 *iv;
size_t len;
u8 rc4key[3 + WLAN_KEY_LEN_WEP104];
iv = ieee80211_wep_add_iv(local, skb, keylen, keyidx);
if (!iv)
return -1;
len = skb->len - (iv + WEP_IV_LEN - skb->data);
/* Prepend 24-bit IV to RC4 key */
memcpy(rc4key, iv, 3);
/* Copy rest of the WEP key (the secret part) */
memcpy(rc4key + 3, key, keylen);
/* Add room for ICV */
skb_put(skb, WEP_ICV_LEN);
return ieee80211_wep_encrypt_data(local->wep_tx_tfm, rc4key, keylen + 3,
iv + WEP_IV_LEN, len);
}
/* Perform WEP decryption using given key. data buffer includes encrypted
* payload, including 4-byte ICV, but _not_ IV. data_len must not include ICV.
* Return 0 on success and -1 on ICV mismatch. */
int ieee80211_wep_decrypt_data(struct crypto_cipher *tfm, u8 *rc4key,
size_t klen, u8 *data, size_t data_len)
{
__le32 crc;
int i;
if (IS_ERR(tfm))
return -1;
crypto_cipher_setkey(tfm, rc4key, klen);
for (i = 0; i < data_len + WEP_ICV_LEN; i++)
crypto_cipher_decrypt_one(tfm, data + i, data + i);
crc = cpu_to_le32(~crc32_le(~0, data, data_len));
if (memcmp(&crc, data + data_len, WEP_ICV_LEN) != 0)
/* ICV mismatch */
return -1;
return 0;
}
/* Perform WEP decryption on given skb. Buffer includes whole WEP part of
* the frame: IV (4 bytes), encrypted payload (including SNAP header),
* ICV (4 bytes). skb->len includes both IV and ICV.
*
* Returns 0 if frame was decrypted successfully and ICV was correct and -1 on
* failure. If frame is OK, IV and ICV will be removed, i.e., decrypted payload
* is moved to the beginning of the skb and skb length will be reduced.
*/
static int ieee80211_wep_decrypt(struct ieee80211_local *local,
struct sk_buff *skb,
struct ieee80211_key *key)
{
u32 klen;
u8 rc4key[3 + WLAN_KEY_LEN_WEP104];
u8 keyidx;
struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
unsigned int hdrlen;
size_t len;
int ret = 0;
if (!ieee80211_has_protected(hdr->frame_control))
return -1;
hdrlen = ieee80211_hdrlen(hdr->frame_control);
if (skb->len < hdrlen + WEP_IV_LEN + WEP_ICV_LEN)
return -1;
len = skb->len - hdrlen - WEP_IV_LEN - WEP_ICV_LEN;
keyidx = skb->data[hdrlen + 3] >> 6;
if (!key || keyidx != key->conf.keyidx)
return -1;
klen = 3 + key->conf.keylen;
/* Prepend 24-bit IV to RC4 key */
memcpy(rc4key, skb->data + hdrlen, 3);
/* Copy rest of the WEP key (the secret part) */
memcpy(rc4key + 3, key->conf.key, key->conf.keylen);
if (ieee80211_wep_decrypt_data(local->wep_rx_tfm, rc4key, klen,
skb->data + hdrlen + WEP_IV_LEN,
len))
ret = -1;
/* Trim ICV */
skb_trim(skb, skb->len - WEP_ICV_LEN);
/* Remove IV */
memmove(skb->data + WEP_IV_LEN, skb->data, hdrlen);
skb_pull(skb, WEP_IV_LEN);
return ret;
}
bool ieee80211_wep_is_weak_iv(struct sk_buff *skb, struct ieee80211_key *key)
{
struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
unsigned int hdrlen;
u8 *ivpos;
u32 iv;
if (!ieee80211_has_protected(hdr->frame_control))
return false;
hdrlen = ieee80211_hdrlen(hdr->frame_control);
ivpos = skb->data + hdrlen;
iv = (ivpos[0] << 16) | (ivpos[1] << 8) | ivpos[2];
return ieee80211_wep_weak_iv(iv, key->conf.keylen);
}
ieee80211_rx_result
ieee80211_crypto_wep_decrypt(struct ieee80211_rx_data *rx)
{
struct sk_buff *skb = rx->skb;
struct ieee80211_rx_status *status = IEEE80211_SKB_RXCB(skb);
struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
if (!ieee80211_is_data(hdr->frame_control) &&
!ieee80211_is_auth(hdr->frame_control))
return RX_CONTINUE;
if (!(status->flag & RX_FLAG_DECRYPTED)) {
if (ieee80211_wep_decrypt(rx->local, rx->skb, rx->key))
return RX_DROP_UNUSABLE;
} else if (!(status->flag & RX_FLAG_IV_STRIPPED)) {
ieee80211_wep_remove_iv(rx->local, rx->skb, rx->key);
/* remove ICV */
skb_trim(rx->skb, rx->skb->len - WEP_ICV_LEN);
}
return RX_CONTINUE;
}
static int wep_encrypt_skb(struct ieee80211_tx_data *tx, struct sk_buff *skb)
{
struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
if (!info->control.hw_key) {
if (ieee80211_wep_encrypt(tx->local, skb, tx->key->conf.key,
tx->key->conf.keylen,
tx->key->conf.keyidx))
return -1;
} else if (info->control.hw_key->flags &
IEEE80211_KEY_FLAG_GENERATE_IV) {
if (!ieee80211_wep_add_iv(tx->local, skb,
tx->key->conf.keylen,
tx->key->conf.keyidx))
return -1;
}
return 0;
}
ieee80211_tx_result
ieee80211_crypto_wep_encrypt(struct ieee80211_tx_data *tx)
{
struct sk_buff *skb;
ieee80211_tx_set_protected(tx);
skb = tx->skb;
do {
if (wep_encrypt_skb(tx, skb) < 0) {
I802_DEBUG_INC(tx->local->tx_handlers_drop_wep);
return TX_DROP;
}
} while ((skb = skb->next));
return TX_CONTINUE;
}
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