/*	$OpenBSD: ip_esp.c,v 1.15 1998/05/24 22:40:12 provos Exp $	*/

/*
 * The authors of this code are John Ioannidis (ji@tla.org),
 * Angelos D. Keromytis (kermit@csd.uch.gr) and 
 * Niels Provos (provos@physnet.uni-hamburg.de).
 *
 * This code was written by John Ioannidis for BSD/OS in Athens, Greece, 
 * in November 1995.
 *
 * Ported to OpenBSD and NetBSD, with additional transforms, in December 1996,
 * by Angelos D. Keromytis.
 *
 * Additional transforms and features in 1997 and 1998 by Angelos D. Keromytis
 * and Niels Provos.
 *
 * Copyright (C) 1995, 1996, 1997, 1998 by John Ioannidis, Angelos D. Keromytis
 * and Niels Provos.
 *	
 * Permission to use, copy, and modify this software without fee
 * is hereby granted, provided that this entire notice is included in
 * all copies of any software which is or includes a copy or
 * modification of this software. 
 * You may use this code under the GNU public license if you so wish. Please
 * contribute changes back to the authors under this freer than GPL license
 * so that we may further the use of strong encryption without limitations to
 * all.
 *
 * THIS SOFTWARE IS BEING PROVIDED "AS IS", WITHOUT ANY EXPRESS OR
 * IMPLIED WARRANTY. IN PARTICULAR, NONE OF THE AUTHORS MAKES ANY
 * REPRESENTATION OR WARRANTY OF ANY KIND CONCERNING THE
 * MERCHANTABILITY OF THIS SOFTWARE OR ITS FITNESS FOR ANY PARTICULAR
 * PURPOSE.
 */

/*
 * Encapsulation Security Payload Processing
 * Per RFC1827 (Atkinson, 1995)
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/domain.h>
#include <sys/protosw.h>
#include <sys/socket.h>
#include <sys/errno.h>
#include <sys/time.h>
#include <sys/kernel.h>
#include <machine/cpu.h>

#include <net/if.h>
#include <net/route.h>
#include <net/netisr.h>

#include <netinet/in.h>
#include <netinet/in_systm.h>
#include <netinet/ip.h>
#include <netinet/in_pcb.h>
#include <netinet/in_var.h>
#include <netinet/ip_var.h>

#include <sys/socketvar.h>
#include <net/raw_cb.h>
#include <net/encap.h>

#include <netinet/ip_icmp.h>
#include <netinet/ip_ipsp.h>
#include <netinet/ip_esp.h>
#include <sys/syslog.h>

void	esp_input __P((struct mbuf *, int));

/*
 * esp_input gets called when we receive an packet with an ESP.
 */

void
esp_input(register struct mbuf *m, int iphlen)
{
    struct ifqueue *ifq = NULL;
    struct expiration *exp;
    struct ip *ipo, ipn;
    struct tdb *tdbp;
    u_int32_t spi;
    int s;
	
    espstat.esps_input++;

    /*
     * Make sure that at least the SPI is in the same mbuf
     */

    ipo = mtod(m, struct ip *);
    if (m->m_len < iphlen + sizeof(u_int32_t))
    {
	if ((m = m_pullup(m, iphlen + sizeof(u_int32_t))) == 0)
	{
#ifdef ENCDEBUG
            if (encdebug)
              printf("esp_input(): (possibly too short) packet from %x to %x dropped\n", ipo->ip_src, ipo->ip_dst);
#endif /* ENCDEBUG */
	    espstat.esps_hdrops++;
	    return;
	}

	ipo = mtod(m, struct ip *);
    }

    spi = *((u_int32_t *) ((caddr_t) ipo + iphlen));

    /*
     * Find tunnel control block and (indirectly) call the appropriate
     * kernel crypto routine. The resulting mbuf chain is a valid
     * IP packet ready to go through input processing.
     */

    tdbp = gettdb(spi, ipo->ip_dst, IPPROTO_ESP);
    if (tdbp == NULL)
    {
	if (encdebug)
	  log(LOG_ERR, "esp_input(): could not find SA for ESP packet from %x to %x, spi %08x\n", ipo->ip_src, ipo->ip_dst, ntohl(spi));
	m_freem(m);
	espstat.esps_notdb++;
	return;
    }
	
    if (tdbp->tdb_flags & TDBF_INVALID)
    {
	if (encdebug)
          log(LOG_ALERT, "esp_input(): attempted to use invalid ESP SA %08x, packet %x->%x\n", ntohl(spi), ipo->ip_src, ipo->ip_dst);
	m_freem(m);
	espstat.esps_invalid++;
	return;
    }

    if (tdbp->tdb_xform == NULL)
    {
	if (encdebug)
          log(LOG_ALERT, "esp_input(): attempted to use uninitialized ESP SA %08x, packet from %x to %x\n", ntohl(spi), ipo->ip_src, ipo->ip_dst);
	m_freem(m);
	espstat.esps_noxform++;
	return;
    }

    m->m_pkthdr.rcvif = &enc_softc;

    /* Register first use, setup expiration timer */
    if (tdbp->tdb_first_use == 0)
    {
	tdbp->tdb_first_use = time.tv_sec;

	if (tdbp->tdb_flags & TDBF_FIRSTUSE)
	{
	    exp = get_expiration();
	    if (exp == (struct expiration *) NULL)
	    {
		if (encdebug)
		  log(LOG_WARNING,
		      "esp_input(): out of memory for expiration timer\n");
		espstat.esps_hdrops++;
		m_freem(m);
		return;
	    }

	    exp->exp_dst.s_addr = tdbp->tdb_dst.s_addr;
	    exp->exp_spi = tdbp->tdb_spi;
	    exp->exp_sproto = tdbp->tdb_sproto;
	    exp->exp_timeout = tdbp->tdb_first_use + tdbp->tdb_exp_first_use;

	    put_expiration(exp);
	}

	if ((tdbp->tdb_flags & TDBF_SOFT_FIRSTUSE) &&
	    (tdbp->tdb_soft_first_use <= tdbp->tdb_exp_first_use))
	{
	    exp = get_expiration();
	    if (exp == (struct expiration *) NULL)
	    {
		if (encdebug)
		  log(LOG_WARNING,
		      "esp_input(): out of memory for expiration timer\n");
		espstat.esps_hdrops++;
		m_freem(m);
		return;
	    }

	    exp->exp_dst.s_addr = tdbp->tdb_dst.s_addr;
	    exp->exp_spi = tdbp->tdb_spi;
	    exp->exp_sproto = tdbp->tdb_sproto;
	    exp->exp_timeout = tdbp->tdb_first_use + tdbp->tdb_soft_first_use;

	    put_expiration(exp);
	}
    }
    
    ipn = *ipo;

    m = (*(tdbp->tdb_xform->xf_input))(m, tdbp);

    if (m == NULL)
    {
	if (encdebug)
	  log(LOG_ALERT, "esp_input(): processing failed for ESP packet from %x to %x, spi %08x\n", ipn.ip_src, ipn.ip_dst, ntohl(spi));
	espstat.esps_badkcr++;
	return;
    }

    ipo = mtod(m, struct ip *);
    if (ipo->ip_p == IPPROTO_IPIP)	/* IP-in-IP encapsulation */
    {
	/* ipn will now contain the inner IP header */
	m_copydata(m, ipo->ip_hl << 2, sizeof(struct ip), (caddr_t) &ipn);
	
	/* Encapsulating SPI */
	if (tdbp->tdb_osrc.s_addr && tdbp->tdb_odst.s_addr)
	{
	    if (tdbp->tdb_flags & TDBF_UNIQUE)
		if ((ipn.ip_src.s_addr != ipo->ip_src.s_addr) ||
		    (ipn.ip_dst.s_addr != ipo->ip_dst.s_addr))
		{
		    if (encdebug)
			log(LOG_ALERT, "esp_input(): ESP-tunnel with different internal addresses %x/%x, SA %08x/%x\n", ipo->ip_src, ipo->ip_dst, tdbp->tdb_spi, tdbp->tdb_dst);
		    m_freem(m);
		    espstat.esps_hdrops++;
		    return;
		}

	    /* 
	     * XXX Here we should be checking that the inner IP addresses
	     * XXX are acceptable/authorized.
	     */
	}
	else				/* So we're paranoid */
	{
	    if (encdebug)
		log(LOG_ALERT, "esp_input(): ESP-tunnel used when expecting ESP-transport, SA %08x/%x\n", tdbp->tdb_spi, tdbp->tdb_dst);
	    m_freem(m);
	    espstat.esps_hdrops++;
	    return;
	}
    }

    /* 
     * Check that the source address is an expected one, if we know what
     * it's supposed to be. This avoids source address spoofing.
     */
    if (tdbp->tdb_src.s_addr != INADDR_ANY)
	if (ipo->ip_src.s_addr != tdbp->tdb_src.s_addr)
	{
	    if (encdebug)
		log(LOG_ALERT, "esp_input(): source address %x doesn't correspond to expected source %x, SA %08x/%x\n", ipo->ip_src, tdbp->tdb_src, tdbp->tdb_dst, tdbp->tdb_spi);
	    m_free(m);
	    espstat.esps_hdrops++;
	    return;
	}

    /*
     * Interface pointer is already in first mbuf; chop off the 
     * `outer' header and reschedule.
     */

    ifq = &ipintrq;

    s = splimp();			/* isn't it already? */
    if (IF_QFULL(ifq))
    {
	IF_DROP(ifq);
	m_freem(m);
	espstat.esps_qfull++;
	splx(s);
#ifdef ENCDEBUG
        if (encdebug)
          printf("esp_input(): dropped packet because of full IP queue\n");
#endif /* ENCDEBUG */
	return;
    }

    IF_ENQUEUE(ifq, m);
    schednetisr(NETISR_IP);
    splx(s);
    return;
}