eapol.c

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/*
 * Copyright (C) 2021 Michael Brown <mbrown@fensystems.co.uk>.
 *
 * 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., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301, USA.
 *
 * You can also choose to distribute this program under the terms of
 * the Unmodified Binary Distribution Licence (as given in the file
 * COPYING.UBDL), provided that you have satisfied its requirements.
 */

FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );

#include <string.h>
#include <assert.h>
#include <errno.h>
#include <byteswap.h>
#include <ipxe/iobuf.h>
#include <ipxe/if_ether.h>
#include <ipxe/if_arp.h>
#include <ipxe/netdevice.h>
#include <ipxe/vlan.h>
#include <ipxe/retry.h>
#include <ipxe/eap.h>
#include <ipxe/eapol.h>

/** @file
 *
 * Extensible Authentication Protocol over LAN (EAPoL)
 *
 */

struct net_driver eapol_driver __net_driver;

/** EAPoL destination MAC address */
static const uint8_t eapol_mac[ETH_ALEN] = {
        0x01, 0x80, 0xc2, 0x00, 0x00, 0x03
};

/**
 * Process EAPoL packet
 *
 * @v iobuf             I/O buffer
 * @v netdev            Network device
 * @v ll_dest           Link-layer destination address
 * @v ll_source         Link-layer source address
 * @v flags             Packet flags
 * @ret rc              Return status code
 */
static int eapol_rx ( struct io_buffer *iobuf, struct net_device *netdev,
                      const void *ll_dest __unused, const void *ll_source,
                      unsigned int flags __unused ) {
        struct eapol_supplicant *supplicant;
        struct eapol_header *eapol;
        struct eapol_handler *handler;
        size_t remaining;
        size_t len;
        int rc;

        /* Find matching supplicant */
        supplicant = netdev_priv ( netdev, &eapol_driver );

        /* Ignore non-EAPoL devices */
        if ( ! supplicant->eap.netdev ) {
                DBGC ( netdev, "EAPOL %s is not an EAPoL device\n",
                       netdev->name );
                DBGC_HDA ( netdev, 0, iobuf->data, iob_len ( iobuf ) );
                rc = -ENOTTY;
                goto drop;
        }

        /* Sanity checks */
        if ( iob_len ( iobuf ) < sizeof ( *eapol ) ) {
                DBGC ( netdev, "EAPOL %s underlength header:\n",
                       netdev->name );
                DBGC_HDA ( netdev, 0, iobuf->data, iob_len ( iobuf ) );
                rc = -EINVAL;
                goto drop;
        }
        eapol = iobuf->data;
        remaining = ( iob_len ( iobuf ) - sizeof ( *eapol ) );
        len = ntohs ( eapol->len );
        if ( len > remaining ) {
                DBGC ( netdev, "EAPOL %s v%d type %d len %zd underlength "
                       "payload:\n", netdev->name, eapol->version,
                       eapol->type, len );
                DBGC_HDA ( netdev, 0, iobuf->data, iob_len ( iobuf ) );
                rc = -EINVAL;
                goto drop;
        }

        /* Strip any trailing padding */
        iob_unput ( iobuf, ( len - remaining ) );

        /* Handle according to type */
        for_each_table_entry ( handler, EAPOL_HANDLERS ) {
                if ( handler->type == eapol->type ) {
                        return handler->rx ( supplicant, iob_disown ( iobuf ),
                                             ll_source );
                }
        }
        rc = -ENOTSUP;
        DBGC ( netdev, "EAPOL %s v%d type %d unsupported\n",
               netdev->name, eapol->version, eapol->type );
        DBGC_HDA ( netdev, 0, iobuf->data, iob_len ( iobuf ) );

 drop:
        free_iob ( iobuf );
        return rc;
}

/** EAPoL protocol */
struct net_protocol eapol_protocol __net_protocol = {
        .name = "EAPOL",
        .net_proto = htons ( ETH_P_EAPOL ),
        .rx = eapol_rx,
};

/**
 * Process EAPoL-encapsulated EAP packet
 *
 * @v supplicant        EAPoL supplicant
 * @v ll_source         Link-layer source address
 * @ret rc              Return status code
 */
static int eapol_eap_rx ( struct eapol_supplicant *supplicant,
                          struct io_buffer *iobuf,
                          const void *ll_source __unused ) {
        struct net_device *netdev = supplicant->eap.netdev;
        struct eapol_header *eapol;
        int rc;

        /* Sanity check */
        assert ( iob_len ( iobuf ) >= sizeof ( *eapol ) );

        /* Strip EAPoL header */
        eapol = iob_pull ( iobuf, sizeof ( *eapol ) );

        /* Process EAP packet */
        if ( ( rc = eap_rx ( &supplicant->eap, iobuf->data,
                             iob_len ( iobuf ) ) ) != 0 ) {
                DBGC ( netdev, "EAPOL %s v%d EAP failed: %s\n",
                       netdev->name, eapol->version, strerror ( rc ) );
                goto drop;
        }

        /* Update EAPoL-Start transmission timer */
        if ( supplicant->eap.flags & EAP_FL_PASSIVE ) {
                /* Stop sending EAPoL-Start */
                if ( timer_running ( &supplicant->timer ) ) {
                        DBGC ( netdev, "EAPOL %s becoming passive\n",
                               netdev->name );
                }
                stop_timer ( &supplicant->timer );
        } else if ( supplicant->eap.flags & EAP_FL_ONGOING ) {
                /* Delay EAPoL-Start until after next expected packet */
                DBGC ( netdev, "EAPOL %s deferring Start\n", netdev->name );
                start_timer_fixed ( &supplicant->timer, EAP_WAIT_TIMEOUT );
                supplicant->count = 0;
        }

 drop:
        free_iob ( iobuf );
        return rc;
}

/** EAPoL handler for EAP packets */
struct eapol_handler eapol_eap __eapol_handler = {
        .type = EAPOL_TYPE_EAP,
        .rx = eapol_eap_rx,
};

/**
 * Transmit EAPoL packet
 *
 * @v supplicant        EAPoL supplicant
 * @v type              Packet type
 * @v data              Packet body
 * @v len               Length of packet body
 * @ret rc              Return status code
 */
static int eapol_tx ( struct eapol_supplicant *supplicant, unsigned int type,
                      const void *data, size_t len ) {
        struct net_device *netdev = supplicant->eap.netdev;
        struct io_buffer *iobuf;
        struct eapol_header *eapol;
        int rc;

        /* Allocate I/O buffer */
        iobuf = alloc_iob ( MAX_LL_HEADER_LEN + sizeof ( *eapol ) + len );
        if ( ! iobuf )
                return -ENOMEM;
        iob_reserve ( iobuf, MAX_LL_HEADER_LEN );

        /* Construct EAPoL header */
        eapol = iob_put ( iobuf, sizeof ( *eapol ) );
        eapol->version = EAPOL_VERSION_2001;
        eapol->type = type;
        eapol->len = htons ( len );

        /* Append packet body */
        memcpy ( iob_put ( iobuf, len ), data, len );

        /* Transmit packet */
        if ( ( rc = net_tx ( iob_disown ( iobuf ), netdev, &eapol_protocol,
                             &eapol_mac, netdev->ll_addr ) ) != 0 ) {
                DBGC ( netdev, "EAPOL %s could not transmit type %d: %s\n",
                       netdev->name, type, strerror ( rc ) );
                DBGC_HDA ( netdev, 0, data, len );
                return rc;
        }

        return 0;
}

/**
 * Transmit EAPoL-encapsulated EAP packet
 *
 * @v supplicant        EAPoL supplicant
 * @v ll_source         Link-layer source address
 * @ret rc              Return status code
 */
static int eapol_eap_tx ( struct eap_supplicant *eap, const void *data,
                          size_t len ) {
        struct eapol_supplicant *supplicant =
                container_of ( eap, struct eapol_supplicant, eap );

        /* Transmit encapsulated packet */
        return eapol_tx ( supplicant, EAPOL_TYPE_EAP, data, len );
}

/**
 * (Re)transmit EAPoL-Start packet
 *
 * @v timer             EAPoL-Start timer
 * @v expired           Failure indicator
 */
static void eapol_expired ( struct retry_timer *timer, int fail __unused ) {
        struct eapol_supplicant *supplicant =
                container_of ( timer, struct eapol_supplicant, timer );
        struct net_device *netdev = supplicant->eap.netdev;

        /* Stop transmitting after maximum number of attempts */
        if ( supplicant->count++ >= EAPOL_START_COUNT ) {
                DBGC ( netdev, "EAPOL %s giving up\n", netdev->name );
                return;
        }

        /* Schedule next transmission */
        start_timer_fixed ( timer, EAPOL_START_INTERVAL );

        /* Transmit EAPoL-Start, ignoring errors */
        DBGC2 ( netdev, "EAPOL %s transmitting Start\n", netdev->name );
        eapol_tx ( supplicant, EAPOL_TYPE_START, NULL, 0 );
}

/**
 * Create EAPoL supplicant
 *
 * @v netdev            Network device
 * @v priv              Private data
 * @ret rc              Return status code
 */
static int eapol_probe ( struct net_device *netdev, void *priv ) {
        struct eapol_supplicant *supplicant = priv;
        struct ll_protocol *ll_protocol = netdev->ll_protocol;

        /* Ignore non-EAPoL devices */
        if ( ll_protocol->ll_proto != htons ( ARPHRD_ETHER ) )
                return 0;
        if ( vlan_tag ( netdev ) )
                return 0;

        /* Initialise structure */
        supplicant->eap.netdev = netdev;
        supplicant->eap.tx = eapol_eap_tx;
        timer_init ( &supplicant->timer, eapol_expired, &netdev->refcnt );

        return 0;
}

/**
 * Handle EAPoL supplicant state change
 *
 * @v netdev            Network device
 * @v priv              Private data
 */
static void eapol_notify ( struct net_device *netdev, void *priv ) {
        struct eapol_supplicant *supplicant = priv;

        /* Ignore non-EAPoL devices */
        if ( ! supplicant->eap.netdev )
                return;

        /* Terminate and reset EAP when link goes down */
        if ( ! ( netdev_is_open ( netdev ) && netdev_link_ok ( netdev ) ) ) {
                if ( timer_running ( &supplicant->timer ) ) {
                        DBGC ( netdev, "EAPOL %s shutting down\n",
                               netdev->name );
                }
                supplicant->eap.flags = 0;
                stop_timer ( &supplicant->timer );
                return;
        }

        /* Do nothing if EAP is already in progress */
        if ( timer_running ( &supplicant->timer ) )
                return;

        /* Do nothing if EAP has already finished transmitting */
        if ( supplicant->eap.flags & EAP_FL_PASSIVE )
                return;

        /* Otherwise, start sending EAPoL-Start */
        start_timer_nodelay ( &supplicant->timer );
        supplicant->count = 0;
        DBGC ( netdev, "EAPOL %s starting up\n", netdev->name );
}

/** EAPoL driver */
struct net_driver eapol_driver __net_driver = {
        .name = "EAPoL",
        .priv_len = sizeof ( struct eapol_supplicant ),
        .probe = eapol_probe,
        .notify = eapol_notify,
};