/*
* Copyright (c) 2009 Joshua Oreman <oremanj@rwcr.net>.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation; either version 2 of the
* License, or any later version.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
FILE_LICENCE ( GPL2_OR_LATER );
#include <gpxe/net80211.h>
#include <gpxe/sec80211.h>
#include <gpxe/crypto.h>
#include <gpxe/arc4.h>
#include <gpxe/crc32.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
/** @file
*
* The WEP wireless encryption method (insecure!)
*
* The data field in a WEP-encrypted packet contains a 3-byte
* initialisation vector, one-byte Key ID field (only the bottom two
* bits are ever used), encrypted data, and a 4-byte encrypted CRC of
* the plaintext data, called the ICV. To decrypt it, the IV is
* prepended to the shared key and the data stream (including ICV) is
* run through the ARC4 stream cipher; if the ICV matches a CRC32
* calculated on the plaintext, the packet is valid.
*
* For efficiency and code-size reasons, this file assumes it is
* running on a little-endian machine.
*/
/** Length of WEP initialisation vector */
#define WEP_IV_LEN 3
/** Length of WEP key ID byte */
#define WEP_KID_LEN 1
/** Length of WEP ICV checksum */
#define WEP_ICV_LEN 4
/** Maximum length of WEP key */
#define WEP_MAX_KEY 16
/** Amount of data placed before the encrypted bytes */
#define WEP_HEADER_LEN 4
/** Amount of data placed after the encrypted bytes */
#define WEP_TRAILER_LEN 4
/** Total WEP overhead bytes */
#define WEP_OVERHEAD 8
/** Context for WEP encryption and decryption */
struct wep_ctx
{
/** Encoded WEP key
*
* The actual key bytes are stored beginning at offset 3, to
* leave room for easily inserting the IV before a particular
* operation.
*/
u8 key[WEP_IV_LEN + WEP_MAX_KEY];
/** Length of WEP key (not including IV bytes) */
int keylen;
/** ARC4 context */
struct arc4_ctx arc4;
};
/**
* Initialize WEP algorithm
*
* @v crypto 802.11 cryptographic algorithm
* @v key WEP key to use
* @v keylen Length of WEP key
* @v rsc Initial receive sequence counter (unused)
* @ret rc Return status code
*
* Standard key lengths are 5 and 13 bytes; 16-byte keys are
* occasionally supported as an extension to the standard.
*/
static int wep_init ( struct net80211_crypto *crypto, const void *key,
int keylen, const void *rsc __unused )
{
struct wep_ctx *ctx = crypto->priv;
ctx->keylen = ( keylen > WEP_MAX_KEY ? WEP_MAX_KEY : keylen );
memcpy ( ctx->key + WEP_IV_LEN, key, ctx->keylen );
return 0;
}
/**
* Encrypt packet using WEP
*
* @v crypto 802.11 cryptographic algorithm
* @v iob I/O buffer of plaintext packet
* @ret eiob Newly allocated I/O buffer for encrypted packet, or NULL
*
* If memory allocation fails, @c NULL is returned.
*/
static struct io_buffer * wep_encrypt ( struct net80211_crypto *crypto,
struct io_buffer *iob )
{
struct wep_ctx *ctx = crypto->priv;
struct io_buffer *eiob;
struct ieee80211_frame *hdr;
const int hdrlen = IEEE80211_TYP_FRAME_HEADER_LEN;
int datalen = iob_len ( iob ) - hdrlen;
int newlen = hdrlen + datalen + WEP_OVERHEAD;
u32 iv, icv;
eiob = alloc_iob ( newlen );
if ( ! eiob )
return NULL;
memcpy ( iob_put ( eiob, hdrlen ), iob->data, hdrlen );
hdr = eiob->data;
hdr->fc |= IEEE80211_FC_PROTECTED;
/* Calculate IV, put it in the header (with key ID byte = 0), and
set it up at the start of the encryption key. */
iv = random() & 0xffffff; /* IV in bottom 3 bytes, top byte = KID = 0 */
memcpy ( iob_put ( eiob, WEP_HEADER_LEN ), &iv, WEP_HEADER_LEN );
memcpy ( ctx->key, &iv, WEP_IV_LEN );
/* Encrypt the data using RC4 */
cipher_setkey ( &arc4_algorithm, &ctx->arc4, ctx->key,
ctx->keylen + WEP_IV_LEN );
cipher_encrypt ( &arc4_algorithm, &ctx->arc4, iob->data + hdrlen,
iob_put ( eiob, datalen ), datalen );
/* Add ICV */
icv = ~crc32_le ( ~0, iob->data + hdrlen, datalen );
cipher_encrypt ( &arc4_algorithm, &ctx->arc4, &icv,
iob_put ( eiob, WEP_ICV_LEN ), WEP_ICV_LEN );
return eiob;
}
/**
* Decrypt packet using WEP
*
* @v crypto 802.11 cryptographic algorithm
* @v eiob I/O buffer of encrypted packet
* @ret iob Newly allocated I/O buffer for plaintext packet, or NULL
*
* If a consistency check for the decryption fails (usually indicating
* an invalid key), @c NULL is returned.
*/
static struct io_buffer * wep_decrypt ( struct net80211_crypto *crypto,
struct io_buffer *eiob )
{
struct wep_ctx *ctx = crypto->priv;
struct io_buffer *iob;
struct ieee80211_frame *hdr;
const int hdrlen = IEEE80211_TYP_FRAME_HEADER_LEN;
int datalen = iob_len ( eiob ) - hdrlen - WEP_OVERHEAD;
int newlen = hdrlen + datalen;
u32 iv, icv, crc;
iob = alloc_iob ( newlen );
if ( ! iob )
return NULL;
memcpy ( iob_put ( iob, hdrlen ), eiob->data, hdrlen );
hdr = iob->data;
hdr->fc &= ~IEEE80211_FC_PROTECTED;
/* Strip off IV and use it to initialize cryptosystem */
memcpy ( &iv, eiob->data + hdrlen, 4 );
iv &= 0xffffff; /* ignore key ID byte */
memcpy ( ctx->key, &iv, WEP_IV_LEN );
/* Decrypt the data using RC4 */
cipher_setkey ( &arc4_algorithm, &ctx->arc4, ctx->key,
ctx->keylen + WEP_IV_LEN );
cipher_decrypt ( &arc4_algorithm, &ctx->arc4, eiob->data + hdrlen +
WEP_HEADER_LEN, iob_put ( iob, datalen ), datalen );
/* Strip off ICV and verify it */
cipher_decrypt ( &arc4_algorithm, &ctx->arc4, eiob->data + hdrlen +
WEP_HEADER_LEN + datalen, &icv, WEP_ICV_LEN );
crc = ~crc32_le ( ~0, iob->data + hdrlen, datalen );
if ( crc != icv ) {
DBGC ( crypto, "WEP %p CRC mismatch: expect %08x, get %08x\n",
crypto, icv, crc );
free_iob ( iob );
return NULL;
}
return iob;
}
/** WEP cryptosystem for 802.11 */
struct net80211_crypto wep_crypto __net80211_crypto = {
.algorithm = NET80211_CRYPT_WEP,
.init = wep_init,
.encrypt = wep_encrypt,
.decrypt = wep_decrypt,
.priv_len = sizeof ( struct wep_ctx ),
};
/**
* Initialize trivial 802.11 security handshaker
*
* @v dev 802.11 device
* @v ctx Security handshaker
*
* This simply fetches a WEP key from netX/key, and if it exists,
* installs WEP cryptography on the 802.11 device. No real handshaking
* is performed.
*/
static int trivial_init ( struct net80211_device *dev )
{
u8 key[WEP_MAX_KEY]; /* support up to 128-bit keys */
int len;
int rc;
if ( dev->associating &&
dev->associating->crypto == NET80211_CRYPT_NONE )
return 0; /* no crypto? OK. */
len = fetch_setting ( netdev_settings ( dev->netdev ),
&net80211_key_setting, key, WEP_MAX_KEY );
if ( len <= 0 ) {
DBGC ( dev, "802.11 %p cannot do WEP without a key\n", dev );
return -EACCES;
}
/* Full 128-bit keys are a nonstandard extension, but they're
utterly trivial to support, so we do. */
if ( len != 5 && len != 13 && len != 16 ) {
DBGC ( dev, "802.11 %p invalid WEP key length %d\n",
dev, len );
return -EINVAL;
}
DBGC ( dev, "802.11 %p installing %d-bit WEP\n", dev, len * 8 );
rc = sec80211_install ( &dev->crypto, NET80211_CRYPT_WEP, key, len,
NULL );
if ( rc < 0 )
return rc;
return 0;
}
/**
* Check for key change on trivial 802.11 security handshaker
*
* @v dev 802.11 device
* @v ctx Security handshaker
*/
static int trivial_change_key ( struct net80211_device *dev )
{
u8 key[WEP_MAX_KEY];
int len;
int change = 0;
/* If going from WEP to clear, or something else to WEP, reassociate. */
if ( ! dev->crypto || ( dev->crypto->init != wep_init ) )
change ^= 1;
len = fetch_setting ( netdev_settings ( dev->netdev ),
&net80211_key_setting, key, WEP_MAX_KEY );
if ( len <= 0 )
change ^= 1;
/* Changing crypto type => return nonzero to reassociate. */
if ( change )
return -EINVAL;
/* Going from no crypto to still no crypto => nothing to do. */
if ( len <= 0 )
return 0;
/* Otherwise, reinitialise WEP with new key. */
return wep_init ( dev->crypto, key, len, NULL );
}
/** Trivial 802.11 security handshaker */
struct net80211_handshaker trivial_handshaker __net80211_handshaker = {
.protocol = NET80211_SECPROT_NONE,
.init = trivial_init,
.change_key = trivial_change_key,
.priv_len = 0,
};