/*
* 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 <asm/scatterlist.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_blkcipher("ecb(arc4)", 0,
CRYPTO_ALG_ASYNC);
if (IS_ERR(local->wep_tx_tfm))
return -ENOMEM;
local->wep_rx_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0,
CRYPTO_ALG_ASYNC);
if (IS_ERR(local->wep_rx_tfm)) {
crypto_free_blkcipher(local->wep_tx_tfm);
return -ENOMEM;
}
return 0;
}
void ieee80211_wep_free(struct ieee80211_local *local)
{
crypto_free_blkcipher(local->wep_tx_tfm);
crypto_free_blkcipher(local->wep_rx_tfm);
}
static inline int 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 1;
}
return 0;
}
void ieee80211_wep_get_iv(struct ieee80211_local *local,
struct ieee80211_key *key, u8 *iv)
{
local->wep_iv++;
if (ieee80211_wep_weak_iv(local->wep_iv, key->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++ = key->keyidx << 6;
}
u8 * ieee80211_wep_add_iv(struct ieee80211_local *local,
struct sk_buff *skb,
struct ieee80211_key *key)
{
struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
u16 fc;
int hdrlen;
u8 *newhdr;
fc = le16_to_cpu(hdr->frame_control);
fc |= IEEE80211_FCTL_PROTECTED;
hdr->frame_control = cpu_to_le16(fc);
if ((skb_headroom(skb) < WEP_IV_LEN ||
skb_tailroom(skb) < WEP_ICV_LEN)) {
I802_DEBUG_INC(local->tx_expand_skb_head);
if (unlikely(pskb_expand_head(skb, WEP_IV_LEN, WEP_ICV_LEN,
GFP_ATOMIC)))
return NULL;
}
hdrlen = ieee80211_get_hdrlen(fc);
newhdr = skb_push(skb, WEP_IV_LEN);
memmove(newhdr, newhdr + WEP_IV_LEN, hdrlen);
ieee80211_wep_get_iv(local, key, newhdr + hdrlen);
return newhdr + hdrlen;
}
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;
u16 fc;
int hdrlen;
fc = le16_to_cpu(hdr->frame_control);
hdrlen = ieee80211_get_hdrlen(fc);
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)) */
void ieee80211_wep_encrypt_data(struct crypto_blkcipher *tfm, u8 *rc4key,
size_t klen, u8 *data, size_t data_len)
{
struct blkcipher_desc desc = { .tfm = tfm };
struct scatterlist sg;
__le32 *icv;
icv = (__le32 *)(data + data_len);
*icv = cpu_to_le32(~crc32_le(~0, data, data_len));
crypto_blkcipher_setkey(tfm, rc4key, klen);
sg.page = virt_to_page(data);
sg.offset = offset_in_page(data);
sg.length = data_len + WEP_ICV_LEN;
crypto_blkcipher_encrypt(&desc, &sg, &sg, sg.length);
}
/* 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,
struct ieee80211_key *key)
{
u32 klen;
u8 *rc4key, *iv;
size_t len;
if (!key || key->alg != ALG_WEP)
return -1;
klen = 3 + key->keylen;
rc4key = kmalloc(klen, GFP_ATOMIC);
if (!rc4key)
return -1;
iv = ieee80211_wep_add_iv(local, skb, key);
if (!iv) {
kfree(rc4key);
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->key, key->keylen);
/* Add room for ICV */
skb_put(skb, WEP_ICV_LEN);
ieee80211_wep_encrypt_data(local->wep_tx_tfm, rc4key, klen,
iv + WEP_IV_LEN, len);
kfree(rc4key);
return 0;
}
/* 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_blkcipher *tfm, u8 *rc4key,
size_t klen, u8 *data, size_t data_len)
{
struct blkcipher_desc desc = { .tfm = tfm };
struct scatterlist sg;
__le32 crc;
crypto_blkcipher_setkey(tfm, rc4key, klen);
sg.page = virt_to_page(data);
sg.offset = offset_in_page(data);
sg.length = data_len + WEP_ICV_LEN;
crypto_blkcipher_decrypt(&desc, &sg, &sg, sg.length);
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.
*/
int ieee80211_wep_decrypt(struct ieee80211_local *local, struct sk_buff *skb,
struct ieee80211_key *key)
{
u32 klen;
u8 *rc4key;
u8 keyidx;
struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
u16 fc;
int hdrlen;
size_t len;
int ret = 0;
fc = le16_to_cpu(hdr->frame_control);
if (!(fc & IEEE80211_FCTL_PROTECTED))
return -1;
hdrlen = ieee80211_get_hdrlen(fc);
if (skb->len < 8 + hdrlen)
return -1;
len = skb->len - hdrlen - 8;
keyidx = skb->data[hdrlen + 3] >> 6;
if (!key || keyidx != key->keyidx || key->alg != ALG_WEP)
return -1;
klen = 3 + key->keylen;
rc4key = kmalloc(klen, GFP_ATOMIC);
if (!rc4key)
return -1;
/* 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->key, key->keylen);
if (ieee80211_wep_decrypt_data(local->wep_rx_tfm, rc4key, klen,
skb->data + hdrlen + WEP_IV_LEN,
len)) {
printk(KERN_DEBUG "WEP decrypt failed (ICV)\n");
ret = -1;
}
kfree(rc4key);
/* 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;
}
int ieee80211_wep_get_keyidx(struct sk_buff *skb)
{
struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
u16 fc;
int hdrlen;
fc = le16_to_cpu(hdr->frame_control);
if (!(fc & IEEE80211_FCTL_PROTECTED))
return -1;
hdrlen = ieee80211_get_hdrlen(fc);
if (skb->len < 8 + hdrlen)
return -1;
return skb->data[hdrlen + 3] >> 6;
}
u8 * ieee80211_wep_is_weak_iv(struct sk_buff *skb, struct ieee80211_key *key)
{
struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
u16 fc;
int hdrlen;
u8 *ivpos;
u32 iv;
fc = le16_to_cpu(hdr->frame_control);
if (!(fc & IEEE80211_FCTL_PROTECTED))
return NULL;
hdrlen = ieee80211_get_hdrlen(fc);
ivpos = skb->data + hdrlen;
iv = (ivpos[0] << 16) | (ivpos[1] << 8) | ivpos[2];
if (ieee80211_wep_weak_iv(iv, key->keylen))
return ivpos;
return NULL;
}
