/*	$OpenBSD: ip_ahmd5.c,v 1.9 1997/06/25 07:53:23 provos Exp $	*/

/*
 * The author of this code is John Ioannidis, ji@tla.org,
 * 	(except when noted otherwise).
 *
 * This code was written for BSD/OS in Athens, Greece, in November 1995.
 *
 * Ported to OpenBSD and NetBSD, with additional transforms, in December 1996,
 * by Angelos D. Keromytis, kermit@forthnet.gr.
 *
 * Copyright (C) 1995, 1996, 1997 by John Ioannidis and 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.
 *
 * THIS SOFTWARE IS BEING PROVIDED "AS IS", WITHOUT ANY EXPRESS OR
 * IMPLIED WARRANTY. IN PARTICULAR, NEITHER AUTHOR MAKES ANY
 * REPRESENTATION OR WARRANTY OF ANY KIND CONCERNING THE
 * MERCHANTABILITY OF THIS SOFTWARE OR ITS FITNESS FOR ANY PARTICULAR
 * PURPOSE.
 */

/*
 * Authentication Header Processing
 * Per RFC1828 (Metzger & Simpson, 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 <netinet/ip_icmp.h>

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

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

/*
 * ahmd5_attach() is called from the transformation initialization code.
 * It just returns.
 */

int
ahmd5_attach()
{
    return 0;
}

/*
 * ahmd5_init() is called when an SPI is being set up. It interprets the
 * encap_msghdr present in m, and sets up the transformation data.
 */

int
ahmd5_init(struct tdb *tdbp, struct xformsw *xsp, struct mbuf *m)
{
    struct ahmd5_xdata *xd;
    struct encap_msghdr *em;
	
    tdbp->tdb_xform = xsp;

    MALLOC(tdbp->tdb_xdata, caddr_t, sizeof (struct ahmd5_xdata),
	   M_XDATA, M_WAITOK);
    if (tdbp->tdb_xdata == NULL)
      return ENOBUFS;
    bzero(tdbp->tdb_xdata, sizeof (struct ahmd5_xdata));
    xd = (struct ahmd5_xdata *)tdbp->tdb_xdata;

    em = mtod(m, struct encap_msghdr *);
    if (em->em_msglen - EMT_SETSPI_FLEN > sizeof (struct ahmd5_xdata))
    {
	free((caddr_t)tdbp->tdb_xdata, M_XDATA);
	tdbp->tdb_xdata = NULL;
	return EINVAL;
    }
    m_copydata(m, EMT_SETSPI_FLEN, em->em_msglen - EMT_SETSPI_FLEN,
	       (caddr_t)xd);
    bzero(ipseczeroes, IPSEC_ZEROES_SIZE);	/* paranoid */
    return 0;
}

/*
 * Free memory
 */

int
ahmd5_zeroize(struct tdb *tdbp)
{
    FREE(tdbp->tdb_xdata, M_XDATA);
    return 0;
}

/*
 * ahmd5_input() gets called to verify that an input packet
 * passes authentication.
 */

extern struct ifnet loif;

struct mbuf *
ahmd5_input(struct mbuf *m, struct tdb *tdb)
{
    struct ahmd5_xdata *xd;
    struct ip *ip, ipo;
    struct ah *ah;
    struct ahmd5 aho;
    struct ifnet *rcvif;
    int ohlen, len, count, off;
    struct mbuf *m0;
    MD5_CTX ctx; 
    u_int8_t optval;
	
    xd = (struct ahmd5_xdata *)tdb->tdb_xdata;
    ohlen = sizeof (struct ip) + AH_FLENGTH + xd->amx_alen;

    rcvif = m->m_pkthdr.rcvif;
    if (rcvif == NULL)
    {
#ifdef ENCDEBUG
	if (encdebug)
	  printf("ahmd5_input: receive interface is NULL!!!\n");
#endif
	rcvif = &loif;
    }
	
    if (m->m_len < ohlen)
    {
	if ((m = m_pullup(m, ohlen)) == NULL)
	{
	    ahstat.ahs_hdrops++;
	    return NULL;
	}
    }

    ip = mtod(m, struct ip *);

    if ((ip->ip_hl << 2) > sizeof(struct ip))
    {
	if ((m = m_pullup(m, ohlen - sizeof (struct ip) +
			  (ip->ip_hl << 2))) == NULL)
	{
	    ahstat.ahs_hdrops++;
	    return NULL;
	}
	
	ip = mtod(m, struct ip *);
	ah = (struct ah *)((u_int8_t *)ip + (ip->ip_hl << 2));
    }
    else
      ah = (struct ah *)(ip + 1);

    ipo = *ip;
    ipo.ip_tos = 0;
    ipo.ip_len += sizeof (struct ip);	/* adjusted in ip_intr() */
    HTONS(ipo.ip_len);
    HTONS(ipo.ip_id);
    ipo.ip_off = htons(ipo.ip_off & IP_DF);	/* XXX -- and the C bit? */
    ipo.ip_ttl = 0;
    ipo.ip_sum = 0;

    MD5Init(&ctx);
    MD5Update(&ctx, (unsigned char *)xd->amx_key, xd->amx_klen);
    MD5Final(NULL, &ctx);		/* non-std usage of MD5Final! */
    MD5Update(&ctx, (unsigned char *)&ipo, sizeof (struct ip));

    /* Options */
    if ((ip->ip_hl << 2 > sizeof(struct ip)))
      for (off = sizeof(struct ip); off < (ip->ip_hl << 2);)
      {
	  optval = ((u_int8_t *)ip)[off];
	  switch (optval)
	  {
	      case IPOPT_EOL:
		  MD5Update(&ctx, ipseczeroes, 1);
		  off = ip->ip_hl << 2;
		  break;

	      case IPOPT_NOP:
		  MD5Update(&ctx, ipseczeroes, 1);
		  off++;
		  break;

	      case IPOPT_SECURITY:
	      case 133:
	      case 134:
		  optval = ((u_int8_t *)ip)[off + 1];
		  MD5Update(&ctx, (u_int8_t *)ip + off, optval);
		  off += optval;
		  break;

	      default:
		  optval = ((u_int8_t *)ip)[off + 1];
		  MD5Update(&ctx, ipseczeroes, optval);
		  off += optval;
		  break;
	  }
      }
    
    
    MD5Update(&ctx, (unsigned char *)ah, AH_FLENGTH);
    MD5Update(&ctx, ipseczeroes, xd->amx_alen);

    /*
     * Code shamelessly stolen from m_copydata
     */
    off = ohlen;
    len = m->m_pkthdr.len - off;
    m0 = m;
	
    while (off > 0)
    {
	if (m0 == 0)
	  panic("ahmd5_input: m_copydata (off)");
	if (off < m0->m_len)
	  break;
	off -= m0->m_len;
	m0 = m0->m_next;
    }

    while (len > 0)
    {
	if (m0 == 0)
	  panic("ahmd5_input: m_copydata (copy)");
	count = min(m0->m_len - off, len);
	MD5Update(&ctx, mtod(m0, unsigned char *) + off, count);
	len -= count;
	off = 0;
	m0 = m0->m_next;
    }


    MD5Update(&ctx, (unsigned char *)xd->amx_key, xd->amx_klen);
    MD5Final((unsigned char *)(&(aho.ah_data[0])), &ctx);
	
    if (bcmp(aho.ah_data, ah->ah_data, xd->amx_alen))
    {
#ifdef ENCDEBUG
	if (encdebug)
	  printf("ahmd5_input: bad auth\n"); /* XXX */
#endif
	ahstat.ahs_badauth++;
	m_freem(m);
	return NULL;
    }
	
    ipo = *ip;
    ipo.ip_p = ah->ah_nh;

    m->m_len -= (ohlen - sizeof(struct ip));
    m->m_data += (ohlen - sizeof(struct ip));
    m->m_pkthdr.len -= (ohlen - sizeof(struct ip));
    m->m_pkthdr.rcvif = rcvif;	/* this should not be necessary */

    ip = mtod(m, struct ip *);
    *ip = ipo;
    ip->ip_len = htons(ip->ip_len - ohlen + 2 * sizeof (struct ip));
    HTONS(ip->ip_id);
    HTONS(ip->ip_off);
    ip->ip_sum = 0;
    ip->ip_sum = in_cksum(m, sizeof (struct ip));

    /* Update the counters */
    tdb->tdb_cur_packets++;
    tdb->tdb_cur_bytes += ntohs(ip->ip_len) - (ip->ip_hl << 2);

    return m;
}


#define AHXPORT 

int
ahmd5_output(struct mbuf *m, struct sockaddr_encap *gw, struct tdb *tdb, struct mbuf **mp)
{
    struct ahmd5_xdata *xd;
    struct ip *ip, ipo;
    struct ah *ah, aho;
    register int len, off, count;
    register struct mbuf *m0;
	
    MD5_CTX ctx;
	
    int ilen, ohlen;
	
    ahstat.ahs_output++;
    m = m_pullup(m, sizeof (struct ip));
    if (m == NULL)
      return ENOBUFS;
	
    ip = mtod(m, struct ip *);
	
    xd = (struct ahmd5_xdata *)tdb->tdb_xdata;

    ilen = ntohs(ip->ip_len);

#ifdef AHXPORT
    ohlen = AH_FLENGTH + xd->amx_alen;
#else
    ohlen = sizeof (struct ip) + AH_FLENGTH + xd->amx_alen;
#endif
	
    ipo.ip_v = IPVERSION;
    ipo.ip_hl = 5;
    ipo.ip_tos = 0;
    ipo.ip_len = htons(ohlen + ilen);
    ipo.ip_id = ip->ip_id;
    ipo.ip_off = htons(ntohs(ip->ip_off) & IP_DF);
    ipo.ip_ttl = 0;
    ipo.ip_p = IPPROTO_AH;
    ipo.ip_sum = 0;
#ifdef AHXPORT
    ipo.ip_src = ip->ip_src;
    ipo.ip_dst = ip->ip_dst;
    aho.ah_nh = ip->ip_p;
#else
    ipo.ip_src = gw->sen_ipsp_src;
    ipo.ip_dst = gw->sen_ipsp_dst;
    aho.ah_nh = IPPROTO_IP4;
#endif
    aho.ah_hl = xd->amx_alen >> 2;
    aho.ah_rv = 0;
    aho.ah_spi = tdb->tdb_spi;

    MD5Init(&ctx);

    MD5Update(&ctx, (unsigned char *)xd->amx_key, xd->amx_klen);
    MD5Final(NULL, &ctx);
    MD5Update(&ctx, (unsigned char *)&ipo, sizeof (struct ip));
    MD5Update(&ctx, (unsigned char *)&aho, AH_FLENGTH);
    MD5Update(&ctx, ipseczeroes, xd->amx_alen);

#ifdef AHXPORT
    off = sizeof (struct ip);
#else	
    off = 0;
#endif

    /*
     * Code shamelessly stolen from m_copydata
     */
    len = m->m_pkthdr.len - off;
	
    m0 = m;

    while (len > 0)
    {
	if (m0 == 0)
	  panic("ahmd5_output: m_copydata");
	count = min(m0->m_len - off, len);
	MD5Update(&ctx, mtod(m0, unsigned char *) + off, count);
	len -= count;
	off = 0;
	m0 = m0->m_next;
    }

    MD5Update(&ctx, (unsigned char *)xd->amx_key, xd->amx_klen);

    ipo.ip_tos = ip->ip_tos;
    ipo.ip_id = ip->ip_id;
    ipo.ip_off = ip->ip_off;
    ipo.ip_ttl = ip->ip_ttl;
/*	ipo.ip_len = ntohs(ipo.ip_len); */
	
    M_PREPEND(m, ohlen, M_DONTWAIT);
    if (m == NULL)
      return ENOBUFS;

    m = m_pullup(m, ohlen + sizeof (struct ip));
    if (m == NULL)
      return ENOBUFS;
	
    ip = mtod(m, struct ip *);
    ah = (struct ah *)(ip + 1);
    *ip = ipo;
    ah->ah_nh = aho.ah_nh;
    ah->ah_hl = aho.ah_hl;
    ah->ah_rv = aho.ah_rv;
    ah->ah_spi = aho.ah_spi;


    MD5Final(&(ah->ah_data[0]), &ctx);

    *mp = m;

    /* Update the counters */
    tdb->tdb_cur_packets++;
    tdb->tdb_cur_bytes += ip->ip_len - (ip->ip_hl << 2) - AH_FLENGTH -
		          xd->amx_alen;

    return 0;
}