/*	$OpenBSD: ipsec_output.c,v 1.2 2000/09/19 08:38:59 angelos Exp $ */

/*
 * The author of this code is Angelos D. Keromytis (angelos@cis.upenn.edu)
 *
 * Copyright (c) 2000 Angelos D. Keromytis.
 *
 * 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.
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/socket.h>
#include <sys/errno.h>
#include <sys/kernel.h>

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

#ifdef INET
#include <netinet/in.h>
#include <netinet/in_systm.h>
#include <netinet/ip.h>
#include <netinet/in_pcb.h>
#include <netinet/ip_var.h>
#endif /* INET */

#ifdef INET6
#ifndef INET
#include <netinet/in.h>
#endif
#include <netinet6/in6_var.h>
#endif /* INET6 */

#include <netinet/ip_ipsp.h>
#include <netinet/ip_ah.h>
#include <netinet/ip_esp.h>

#ifdef ENCDEBUG
#define DPRINTF(x)	if (encdebug) printf x
#else
#define DPRINTF(x)
#endif

#ifndef offsetof
#define offsetof(s, e) ((int)&((s *)0)->e)
#endif

/*
 * Loop over a tdb chain, taking into consideration protocol tunneling. The
 * fourth argument is set if the first encapsulation header is already in
 * place.
 */
int
ipsp_process_packet(struct mbuf *m, struct tdb *tdb, int af, int tunalready)
{
    int i, off, error;
    struct mbuf *mp;

#ifdef INET
    struct ip *ip;
#endif /* INET */
#ifdef INET6
    struct ip6_hdr *ip6;
#endif /* INET6 */

    /* Check that the transform is allowed by the administrator */
    if ((tdb->tdb_sproto == IPPROTO_ESP && !esp_enable) ||
	(tdb->tdb_sproto == IPPROTO_AH && !ah_enable))
    {
	DPRINTF(("ipsp_process_packet(): IPSec outbound packet dropped due to policy (check your sysctls)\n"));
	m_freem(m);
	return EHOSTUNREACH;
    }

    /* Sanity check */
    if (!tdb->tdb_xform)
    {
	DPRINTF(("ipsp_process_packet(): uninitialized TDB\n"));
	m_freem(m);
	return EHOSTUNREACH;
    }

    /* Check if the SPI is invalid */
    if (tdb->tdb_flags & TDBF_INVALID)
    {
	DPRINTF(("ipsp_process_packet(): attempt to use invalid SA %s/%08x/%u\n", ipsp_address(tdb->tdb_dst), ntohl(tdb->tdb_spi), tdb->tdb_sproto));
	m_freem(m);
	return ENXIO;
    }

    /* Check that the network protocol is supported */
    switch (tdb->tdb_dst.sa.sa_family)
    {
#ifdef INET
	case AF_INET:
	    break;
#endif /* INET */

#ifdef INET6
	case AF_INET6:
	    break;
#endif /* INET6 */

	default:
	    DPRINTF(("ipsp_process_packet(): attempt to use SA %s/%08x/%u for protocol family %d\n", ipsp_address(tdb->tdb_dst), ntohl(tdb->tdb_spi), tdb->tdb_sproto, tdb->tdb_dst.sa.sa_family));
	    m_freem(m);
	    return ENXIO;
    }

    /* Register first use if applicable, setup relevant expiration timer */
    if (tdb->tdb_first_use == 0)
    {
	tdb->tdb_first_use = time.tv_sec;
	tdb_expiration(tdb, TDBEXP_TIMEOUT);
    }

    /*
     * Check for tunneling if we don't have the first header in place.
     * When doing Ethernet-over-IP, we are handed an already-encapsulated
     * frame, so we don't need to re-encapsulate.
     */
    if (tunalready == 0)
    {
	/*
	 * If the target protocol family is different, we know we'll be
	 * doing tunneling.
	 */
	if (af == tdb->tdb_dst.sa.sa_family)
	{
#ifdef INET
	    if (af == AF_INET)
	      i = sizeof(struct ip);
#endif /* INET */

#ifdef INET6
	    if (af == AF_INET6)
	      i = sizeof(struct ip6_hdr);
#endif /* INET6 */

	    /* Bring the network header in the first mbuf */
	    if (m->m_len < i)
	    {
		if ((m = m_pullup(m, i)) == 0)
		  return ENOBUFS;
	    }

#ifdef INET
	    ip = mtod(m, struct ip *);
#endif /* INET */

#ifdef INET6
	    ip6 = mtod(m, struct ip6_hdr *);
#endif /* INET6 */
	}

	/* Do the appropriate encapsulation, if necessary */
	if ((tdb->tdb_dst.sa.sa_family != af) || /* PF mismatch */
	    (tdb->tdb_flags & TDBF_TUNNELING) || /* Tunneling requested */
	    (tdb->tdb_xform->xf_type == XF_IP4) || /* ditto */
#ifdef INET
	    ((tdb->tdb_dst.sa.sa_family == AF_INET) &&
	     (tdb->tdb_dst.sin.sin_addr.s_addr != INADDR_ANY) &&
	     (tdb->tdb_dst.sin.sin_addr.s_addr != ip->ip_dst.s_addr)) ||
#endif /* INET */
#ifdef INET6
	    ((tdb->tdb_dst.sa.sa_family == AF_INET6) &&
	     (!IN6_IS_ADDR_UNSPECIFIED(&tdb->tdb_dst.sin6.sin6_addr)) &&
	     (!IN6_ARE_ADDR_EQUAL(&tdb->tdb_dst.sin6.sin6_addr,
				  &ip6->ip6_dst))) ||
#endif /* INET6 */
	    0)
	{
#ifdef INET
	    /* Fix IPv4 header checksum and length */
	    if (af == AF_INET)
	    {
		if ((m = m_pullup(m, sizeof(struct ip))) == 0)
		  return ENOBUFS;

		ip = mtod(m, struct ip *);
		ip->ip_len = htons(m->m_pkthdr.len);
                ip->ip_sum = 0;
		ip->ip_sum = in_cksum(m, ip->ip_hl << 2);
	    }
#endif /* INET */

#ifdef INET6
	    /* Fix IPv6 header payload length */
	    if (af == AF_INET6)
	    {
		if ((m = m_pullup(m, sizeof(struct ip6_hdr))) == 0)
		    return ENOBUFS;

		if (m->m_pkthdr.len - sizeof(*ip6) > IPV6_MAXPACKET) {
		    /* no jumbogram support */
		    m_freem(m);
		    return ENXIO;	/*?*/
		}
		ip6 = mtod(m, struct ip6_hdr *);
		ip6->ip6_plen = htons(m->m_pkthdr.len - sizeof(*ip6));
	    }
#endif /* INET6 */

	    /* Encapsulate -- the last two arguments are unused */
	    error = ipip_output(m, tdb, &mp, 0, 0);
	    if ((mp == NULL) && (!error))
	      error = EFAULT;
	    if (error)
	    {
		if (mp)
		{
		    m_freem(mp);
		    mp = NULL;
		}

		return error;
	    }

	    m = mp;
	    mp = NULL;
	}

	/* We may be done with this TDB */
	if (tdb->tdb_xform->xf_type == XF_IP4)
	  return ipsp_process_done(m, tdb);
    }
    else
    {
	/*
	 * If this is just an IP-IP TDB and we're told there's already an
	 * encapsulation header, move on.
	 */
	if (tdb->tdb_xform->xf_type == XF_IP4)
	  return ipsp_process_done(m, tdb);
    }

    /* Extract some information off the headers */
    switch (tdb->tdb_dst.sa.sa_family)
    {
#ifdef INET
	case AF_INET:
	    ip = mtod(m, struct ip *);
	    i = ip->ip_hl << 2;
	    off = offsetof(struct ip, ip_p);
	    break;
#endif /* INET */

#ifdef INET6
	case AF_INET6:
	    ip6 = mtod(m, struct ip6_hdr *);
	    i = sizeof(struct ip6_hdr);
	    off = offsetof(struct ip6_hdr, ip6_nxt);
	    break;
#endif /* INET6 */
    }

    /* Invoke the IPsec transform */
    return (*(tdb->tdb_xform->xf_output))(m, tdb, NULL, i, off);
}

/*
 * Called by the IPsec output transform callbacks, to transmit the packet
 * or do further processing, as necessary.
 */
int
ipsp_process_done(struct mbuf *m, struct tdb *tdb)
{
#ifdef INET
    struct ip *ip;
#endif /* INET */

#ifdef INET6
    struct ip6_hdr *ip6;
#endif /* INET6 */

    switch (tdb->tdb_dst.sa.sa_family)
    {
#ifdef INET
	case AF_INET:
	    /* Fix the header length, for AH processing */
	    if (tdb->tdb_dst.sa.sa_family == AF_INET)
	    {
		ip = mtod(m, struct ip *);
		ip->ip_len = htons(m->m_pkthdr.len);
	    }
	    break;
#endif /* INET */

#ifdef INET6
	case AF_INET6:
	    /* Fix the header length, for AH processing */
	    if (tdb->tdb_dst.sa.sa_family == AF_INET6)
	    {
		if (m->m_pkthdr.len < sizeof(*ip6)) {
		    m_freem(m);
		    return ENXIO;
		}
		if (m->m_pkthdr.len - sizeof(*ip6) > IPV6_MAXPACKET) {
		    /* no jumbogram support */
		    m_freem(m);
		    return ENXIO;	/*?*/
		}

		ip6 = mtod(m, struct ip6_hdr *);
		ip6->ip6_plen = htons(m->m_pkthdr.len - sizeof(*ip6));
	    }
	    break;
#endif /* INET6 */

	default:
	    m_freem(m);
	    DPRINTF(("ipsp_process_done(): unknown protocol family (%d)\n",
		     tdb->tdb_dst.sa.sa_family));
	    return ENXIO;
    }

    /* If there's another (bundled) TDB to apply, do so */
    if (tdb->tdb_onext)
      return ipsp_process_packet(m, tdb->tdb_onext,
				 tdb->tdb_onext->tdb_dst.sa.sa_family, 0);

    /*
     * We're done with IPsec processing, transmit the packet using the
     * appropriate network protocol (IP or IPv6). SPD lookup will be
     * performed again there.
     */
    switch (tdb->tdb_dst.sa.sa_family)
    {
#ifdef INET
	case AF_INET:
	    NTOHS(ip->ip_len);
	    NTOHS(ip->ip_off);

	    return ip_output(m, NULL, NULL, IP_ENCAPSULATED | IP_RAWOUTPUT,
			     NULL, NULL);
#endif /* INET */

#ifdef INET6
	case AF_INET6:
	    /*
	     * We don't need massage, IPv6 header fields are always in
	     * net endian
	     */
	    return ip6_output(m, NULL, NULL, IPV6_ENCAPSULATED, NULL, NULL);
#endif /* INET6 */
    }

    /* Not reached */
    return EINVAL;
}