// SPDX-License-Identifier: GPL-2.0-only
/*
* lib80211 crypt: host-based WEP encryption implementation for lib80211
*
* Copyright (c) 2002-2004, Jouni Malinen <[email protected]>
* Copyright (c) 2008, John W. Linville <[email protected]>
*/
#include <linux/err.h>
#include <linux/fips.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/random.h>
#include <linux/scatterlist.h>
#include <linux/skbuff.h>
#include <linux/mm.h>
#include <asm/string.h>
#include <net/lib80211.h>
#include <crypto/arc4.h>
#include <linux/crc32.h>
MODULE_AUTHOR("Jouni Malinen");
MODULE_DESCRIPTION("lib80211 crypt: WEP");
MODULE_LICENSE("GPL");
struct lib80211_wep_data {
u32 iv;
#define WEP_KEY_LEN 13
u8 key[WEP_KEY_LEN + 1];
u8 key_len;
u8 key_idx;
struct arc4_ctx tx_ctx;
struct arc4_ctx rx_ctx;
};
static void *lib80211_wep_init(int keyidx)
{
struct lib80211_wep_data *priv;
if (fips_enabled)
return NULL;
priv = kzalloc(sizeof(*priv), GFP_ATOMIC);
if (priv == NULL)
return NULL;
priv->key_idx = keyidx;
/* start WEP IV from a random value */
get_random_bytes(&priv->iv, 4);
return priv;
}
static void lib80211_wep_deinit(void *priv)
{
kfree_sensitive(priv);
}
/* Add WEP IV/key info to a frame that has at least 4 bytes of headroom */
static int lib80211_wep_build_iv(struct sk_buff *skb, int hdr_len,
u8 *key, int keylen, void *priv)
{
struct lib80211_wep_data *wep = priv;
u32 klen;
u8 *pos;
if (skb_headroom(skb) < 4 || skb->len < hdr_len)
return -1;
pos = skb_push(skb, 4);
memmove(pos, pos + 4, hdr_len);
pos += hdr_len;
klen = 3 + wep->key_len;
wep->iv++;
/* 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 ((wep->iv & 0xff00) == 0xff00) {
u8 B = (wep->iv >> 16) & 0xff;
if (B >= 3 && B < klen)
wep->iv += 0x0100;
}
/* Prepend 24-bit IV to RC4 key and TX frame */
*pos++ = (wep->iv >> 16) & 0xff;
*pos++ = (wep->iv >> 8) & 0xff;
*pos++ = wep->iv & 0xff;
*pos++ = wep->key_idx << 6;
return 0;
}
/* Perform WEP encryption on given skb that has at least 4 bytes of headroom
* for IV and 4 bytes of tailroom for ICV. 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))
*/
static int lib80211_wep_encrypt(struct sk_buff *skb, int hdr_len, void *priv)
{
struct lib80211_wep_data *wep = priv;
u32 crc, klen, len;
u8 *pos, *icv;
u8 key[WEP_KEY_LEN + 3];
/* other checks are in lib80211_wep_build_iv */
if (skb_tailroom(skb) < 4)
return -1;
/* add the IV to the frame */
if (lib80211_wep_build_iv(skb, hdr_len, NULL, 0, priv))
return -1;
/* Copy the IV into the first 3 bytes of the key */
skb_copy_from_linear_data_offset(skb, hdr_len, key, 3);
/* Copy rest of the WEP key (the secret part) */
memcpy(key + 3, wep->key, wep->key_len);
len = skb->len - hdr_len - 4;
pos = skb->data + hdr_len + 4;
klen = 3 + wep->key_len;
/* Append little-endian CRC32 over only the data and encrypt it to produce ICV */
crc = ~crc32_le(~0, pos, len);
icv = skb_put(skb, 4);
icv[0] = crc;
icv[1] = crc >> 8;
icv[2] = crc >> 16;
icv[3] = crc >> 24;
arc4_setkey(&wep->tx_ctx, key, klen);
arc4_crypt(&wep->tx_ctx, pos, pos, len + 4);
return 0;
}
/* Perform WEP decryption on given buffer. Buffer includes whole WEP part of
* the frame: IV (4 bytes), encrypted payload (including SNAP header),
* ICV (4 bytes). 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.
*/
static int lib80211_wep_decrypt(struct sk_buff *skb, int hdr_len, void *priv)
{
struct lib80211_wep_data *wep = priv;
u32 crc, klen, plen;
u8 key[WEP_KEY_LEN + 3];
u8 keyidx, *pos, icv[4];
if (skb->len < hdr_len + 8)
return -1;
pos = skb->data + hdr_len;
key[0] = *pos++;
key[1] = *pos++;
key[2] = *pos++;
keyidx = *pos++ >> 6;
if (keyidx != wep->key_idx)
return -1;
klen = 3 + wep->key_len;
/* Copy rest of the WEP key (the secret part) */
memcpy(key + 3, wep->key, wep->key_len);
/* Apply RC4 to data and compute CRC32 over decrypted data */
plen = skb->len - hdr_len - 8;
arc4_setkey(&wep->rx_ctx, key, klen);
arc4_crypt(&wep->rx_ctx, pos, pos, plen + 4);
crc = ~crc32_le(~0, pos, plen);
icv[0] = crc;
icv[1] = crc >> 8;
icv[2] = crc >> 16;
icv[3] = crc >> 24;
if (memcmp(icv, pos + plen, 4) != 0) {
/* ICV mismatch - drop frame */
return -2;
}
/* Remove IV and ICV */
memmove(skb->data + 4, skb->data, hdr_len);
skb_pull(skb, 4);
skb_trim(skb, skb->len - 4);
return 0;
}
static int lib80211_wep_set_key(void *key, int len, u8 * seq, void *priv)
{
struct lib80211_wep_data *wep = priv;
if (len < 0 || len > WEP_KEY_LEN)
return -1;
memcpy(wep->key, key, len);
wep->key_len = len;
return 0;
}
static int lib80211_wep_get_key(void *key, int len, u8 * seq, void *priv)
{
struct lib80211_wep_data *wep = priv;
if (len < wep->key_len)
return -1;
memcpy(key, wep->key, wep->key_len);
return wep->key_len;
}
static void lib80211_wep_print_stats(struct seq_file *m, void *priv)
{
struct lib80211_wep_data *wep = priv;
seq_printf(m, "key[%d] alg=WEP len=%d\n", wep->key_idx, wep->key_len);
}
static const struct lib80211_crypto_ops lib80211_crypt_wep = {
.name = "WEP",
.init = lib80211_wep_init,
.deinit = lib80211_wep_deinit,
.encrypt_mpdu = lib80211_wep_encrypt,
.decrypt_mpdu = lib80211_wep_decrypt,
.encrypt_msdu = NULL,
.decrypt_msdu = NULL,
.set_key = lib80211_wep_set_key,
.get_key = lib80211_wep_get_key,
.print_stats = lib80211_wep_print_stats,
.extra_mpdu_prefix_len = 4, /* IV */
.extra_mpdu_postfix_len = 4, /* ICV */
.owner = THIS_MODULE,
};
static int __init lib80211_crypto_wep_init(void)
{
return lib80211_register_crypto_ops(&lib80211_crypt_wep);
}
static void __exit lib80211_crypto_wep_exit(void)
{
lib80211_unregister_crypto_ops(&lib80211_crypt_wep);
}
module_init(lib80211_crypto_wep_init);
module_exit(lib80211_crypto_wep_exit);
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