text: /*-
   * Copyright (c) 1982, 1986, 1988, 1993
   *      The Regents of the University of California.  All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   * 1. Redistributions of source code must retain the above copyright
   *    notice, this list of conditions and the following disclaimer.
   * 2. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in the
   *    documentation and/or other materials provided with the distribution.
   * 4. Neither the name of the University nor the names of its contributors
   *    may be used to endorse or promote products derived from this software
   *    without specific prior written permission.
   *
   * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   * SUCH DAMAGE.
   */
  
  #include <sys/cdefs.h>
  __FBSDID("$FreeBSD: soc2013/dpl/head/sys/netinet/ip_ipsec.c 243093 2012-10-22 21:09:03Z glebius $");
  
  #include "opt_ipsec.h"
  #include "opt_sctp.h"
  
  #include <sys/param.h>
  #include <sys/systm.h>
  #include <sys/errno.h>
  #include <sys/kernel.h>
  #include <sys/malloc.h>
  #include <sys/mbuf.h>
  #include <sys/protosw.h>
  #include <sys/socket.h>
  #include <sys/socketvar.h>
  #include <sys/sysctl.h>
  
  #include <net/if.h>
  #include <net/route.h>
  #include <net/vnet.h>
  
  #include <netinet/in.h>
  #include <netinet/in_systm.h>
  #include <netinet/in_var.h>
  #include <netinet/ip.h>
  #include <netinet/in_pcb.h>
  #include <netinet/ip_var.h>
  #include <netinet/ip_options.h>
  #include <netinet/ip_ipsec.h>
  #ifdef SCTP
  #include <netinet/sctp_crc32.h>
  #endif
  
  #include <machine/in_cksum.h>
  
  #ifdef IPSEC
  #include <netipsec/ipsec.h>
  #include <netipsec/xform.h>
  #include <netipsec/key.h>
  #endif /*IPSEC*/
  
  extern	struct protosw inetsw[];
  
  #ifdef IPSEC
  #ifdef IPSEC_FILTERTUNNEL
  static VNET_DEFINE(int, ip4_ipsec_filtertunnel) = 1;
  #else
  static VNET_DEFINE(int, ip4_ipsec_filtertunnel) = 0;
  #endif
  #define	V_ip4_ipsec_filtertunnel VNET(ip4_ipsec_filtertunnel)
  
  SYSCTL_DECL(_net_inet_ipsec);
  SYSCTL_VNET_INT(_net_inet_ipsec, OID_AUTO, filtertunnel,
  	CTLFLAG_RW, &VNET_NAME(ip4_ipsec_filtertunnel), 0,
  	"If set filter packets from an IPsec tunnel.");
  #endif /* IPSEC */
  
  /*
   * Check if we have to jump over firewall processing for this packet.
   * Called from ip_input().
   * 1 = jump over firewall, 0 = packet goes through firewall.
   */
  int
  ip_ipsec_filtertunnel(struct mbuf *m)
  {
  #ifdef IPSEC
  
  	/*
  	 * Bypass packet filtering for packets previously handled by IPsec.
  	 */
  	if (!V_ip4_ipsec_filtertunnel &&
  	    m_tag_find(m, PACKET_TAG_IPSEC_IN_DONE, NULL) != NULL)
  		return 1;
  #endif
  	return 0;
  }
  
  /*
   * Check if this packet has an active SA and needs to be dropped instead
   * of forwarded.
   * Called from ip_input().
   * 1 = drop packet, 0 = forward packet.
   */
  int
  ip_ipsec_fwd(struct mbuf *m)
  {
  #ifdef IPSEC
  	struct m_tag *mtag;
  	struct tdb_ident *tdbi;
  	struct secpolicy *sp;
  	int error;
  
  	mtag = m_tag_find(m, PACKET_TAG_IPSEC_IN_DONE, NULL);
  	if (mtag != NULL) {
  		tdbi = (struct tdb_ident *)(mtag + 1);
  		sp = ipsec_getpolicy(tdbi, IPSEC_DIR_INBOUND);
  	} else {
  		sp = ipsec_getpolicybyaddr(m, IPSEC_DIR_INBOUND,
  					   IP_FORWARDING, &error);   
  	}
  	if (sp == NULL) {	/* NB: can happen if error */
  		/*XXX error stat???*/
  		DPRINTF(("ip_input: no SP for forwarding\n"));	/*XXX*/
  		return 1;
  	}
  
  	/*
  	 * Check security policy against packet attributes.
  	 */
  	error = ipsec_in_reject(sp, m);
  	KEY_FREESP(&sp);
  	if (error) {
  		IPSTAT_INC(ips_cantforward);
  		return 1;
  	}
  #endif /* IPSEC */
  	return 0;
  }
  
  /*
   * Check if protocol type doesn't have a further header and do IPSEC
   * decryption or reject right now.  Protocols with further headers get
   * their IPSEC treatment within the protocol specific processing.
   * Called from ip_input().
   * 1 = drop packet, 0 = continue processing packet.
   */
  int
  ip_ipsec_input(struct mbuf *m)
  {
  #ifdef IPSEC
  	struct ip *ip = mtod(m, struct ip *);
  	struct m_tag *mtag;
  	struct tdb_ident *tdbi;
  	struct secpolicy *sp;
  	int error;
  	/*
  	 * enforce IPsec policy checking if we are seeing last header.
  	 * note that we do not visit this with protocols with pcb layer
  	 * code - like udp/tcp/raw ip.
  	 */
  	if ((inetsw[ip_protox[ip->ip_p]].pr_flags & PR_LASTHDR) != 0) {
  		/*
  		 * Check if the packet has already had IPsec processing
  		 * done.  If so, then just pass it along.  This tag gets
  		 * set during AH, ESP, etc. input handling, before the
  		 * packet is returned to the ip input queue for delivery.
  		 */ 
  		mtag = m_tag_find(m, PACKET_TAG_IPSEC_IN_DONE, NULL);
  		if (mtag != NULL) {
  			tdbi = (struct tdb_ident *)(mtag + 1);
  			sp = ipsec_getpolicy(tdbi, IPSEC_DIR_INBOUND);
  		} else {
  			sp = ipsec_getpolicybyaddr(m, IPSEC_DIR_INBOUND,
  						   IP_FORWARDING, &error);   
  		}
  		if (sp != NULL) {
  			/*
  			 * Check security policy against packet attributes.
  			 */
  			error = ipsec_in_reject(sp, m);
  			KEY_FREESP(&sp);
  		} else {
  			/* XXX error stat??? */
  			error = EINVAL;
  			DPRINTF(("ip_input: no SP, packet discarded\n"));/*XXX*/
  			return 1;
  		}
  		if (error)
  			return 1;
  	}
  #endif /* IPSEC */
  	return 0;
  }
  
  /*
   * Compute the MTU for a forwarded packet that gets IPSEC encapsulated.
   * Called from ip_forward().
   * Returns MTU suggestion for ICMP needfrag reply.
   */
  int
  ip_ipsec_mtu(struct mbuf *m, int mtu)
  {
  	/*
  	 * If the packet is routed over IPsec tunnel, tell the
  	 * originator the tunnel MTU.
  	 *	tunnel MTU = if MTU - sizeof(IP) - ESP/AH hdrsiz
  	 * XXX quickhack!!!
  	 */
  	struct secpolicy *sp = NULL;
  	int ipsecerror;
  	int ipsechdr;
  	struct route *ro;
  	sp = ipsec_getpolicybyaddr(m,
  				   IPSEC_DIR_OUTBOUND,
  				   IP_FORWARDING,
  				   &ipsecerror);
  	if (sp != NULL) {
  		/* count IPsec header size */
  		ipsechdr = ipsec_hdrsiz(m, IPSEC_DIR_OUTBOUND, NULL);
  
  		/*
  		 * find the correct route for outer IPv4
  		 * header, compute tunnel MTU.
  		 */
  		if (sp->req != NULL &&
  		    sp->req->sav != NULL &&
  		    sp->req->sav->sah != NULL) {
  			ro = &sp->req->sav->sah->route_cache.sa_route;
  			if (ro->ro_rt && ro->ro_rt->rt_ifp) {
  				mtu =
  				    ro->ro_rt->rt_rmx.rmx_mtu ?
  				    ro->ro_rt->rt_rmx.rmx_mtu :
  				    ro->ro_rt->rt_ifp->if_mtu;
  				mtu -= ipsechdr;
  			}
  		}
  		KEY_FREESP(&sp);
  	}
  	return mtu;
  }
  
  /*
   * 
   * Called from ip_output().
   * 1 = drop packet, 0 = continue processing packet,
   * -1 = packet was reinjected and stop processing packet
   */
  int
  ip_ipsec_output(struct mbuf **m, struct inpcb *inp, int *flags, int *error)
  {
  #ifdef IPSEC
  	struct secpolicy *sp = NULL;
  	struct tdb_ident *tdbi;
  	struct m_tag *mtag;
  	/*
  	 * Check the security policy (SP) for the packet and, if
  	 * required, do IPsec-related processing.  There are two
  	 * cases here; the first time a packet is sent through
  	 * it will be untagged and handled by ipsec4_checkpolicy.
  	 * If the packet is resubmitted to ip_output (e.g. after
  	 * AH, ESP, etc. processing), there will be a tag to bypass
  	 * the lookup and related policy checking.
  	 */
  	mtag = m_tag_find(*m, PACKET_TAG_IPSEC_PENDING_TDB, NULL);
  	if (mtag != NULL) {
  		tdbi = (struct tdb_ident *)(mtag + 1);
  		sp = ipsec_getpolicy(tdbi, IPSEC_DIR_OUTBOUND);
  		if (sp == NULL)
  			*error = -EINVAL;	/* force silent drop */
  		m_tag_delete(*m, mtag);
  	} else {
  		sp = ipsec4_checkpolicy(*m, IPSEC_DIR_OUTBOUND, *flags,
  					error, inp);
  	}
  	/*
  	 * There are four return cases:
  	 *    sp != NULL	 	    apply IPsec policy
  	 *    sp == NULL, error == 0	    no IPsec handling needed
  	 *    sp == NULL, error == -EINVAL  discard packet w/o error
  	 *    sp == NULL, error != 0	    discard packet, report error
  	 */
  	if (sp != NULL) {
  		/* Loop detection, check if ipsec processing already done */
  		KASSERT(sp->req != NULL, ("ip_output: no ipsec request"));
  		for (mtag = m_tag_first(*m); mtag != NULL;
  		     mtag = m_tag_next(*m, mtag)) {
  			if (mtag->m_tag_cookie != MTAG_ABI_COMPAT)
  				continue;
  			if (mtag->m_tag_id != PACKET_TAG_IPSEC_OUT_DONE &&
  			    mtag->m_tag_id != PACKET_TAG_IPSEC_OUT_CRYPTO_NEEDED)
  				continue;
  			/*
  			 * Check if policy has an SA associated with it.
  			 * This can happen when an SP has yet to acquire
  			 * an SA; e.g. on first reference.  If it occurs,
  			 * then we let ipsec4_process_packet do its thing.
  			 */
  			if (sp->req->sav == NULL)
  				break;
  			tdbi = (struct tdb_ident *)(mtag + 1);
  			if (tdbi->spi == sp->req->sav->spi &&
  			    tdbi->proto == sp->req->sav->sah->saidx.proto &&
  			    bcmp(&tdbi->dst, &sp->req->sav->sah->saidx.dst,
  				 sizeof (union sockaddr_union)) == 0) {
  				/*
  				 * No IPsec processing is needed, free
  				 * reference to SP.
  				 *
  				 * NB: null pointer to avoid free at
  				 *     done: below.
  				 */
  				KEY_FREESP(&sp), sp = NULL;
  				goto done;
  			}
  		}
  
  		/*
  		 * Do delayed checksums now because we send before
  		 * this is done in the normal processing path.
  		 */
  		if ((*m)->m_pkthdr.csum_flags & CSUM_DELAY_DATA) {
  			in_delayed_cksum(*m);
  			(*m)->m_pkthdr.csum_flags &= ~CSUM_DELAY_DATA;
  		}
  #ifdef SCTP
  		if ((*m)->m_pkthdr.csum_flags & CSUM_SCTP) {
  			struct ip *ip = mtod(*m, struct ip *);
  
  			sctp_delayed_cksum(*m, (uint32_t)(ip->ip_hl << 2));
  			(*m)->m_pkthdr.csum_flags &= ~CSUM_SCTP;
  		}
  #endif
  
  		/* NB: callee frees mbuf */
  		*error = ipsec4_process_packet(*m, sp->req, *flags, 0);
  		if (*error == EJUSTRETURN) {
  			/*
  			 * We had a SP with a level of 'use' and no SA. We
  			 * will just continue to process the packet without
  			 * IPsec processing and return without error.
  			 */
  			*error = 0;
  			goto done;
  		}
  		/*
  		 * Preserve KAME behaviour: ENOENT can be returned
  		 * when an SA acquire is in progress.  Don't propagate
  		 * this to user-level; it confuses applications.
  		 *
  		 * XXX this will go away when the SADB is redone.
  		 */
  		if (*error == ENOENT)
  			*error = 0;
  		goto reinjected;
  	} else {	/* sp == NULL */
  
  		if (*error != 0) {
  			/*
  			 * Hack: -EINVAL is used to signal that a packet
  			 * should be silently discarded.  This is typically
  			 * because we asked key management for an SA and
  			 * it was delayed (e.g. kicked up to IKE).
  			 */
  			if (*error == -EINVAL)
  				*error = 0;
  			goto bad;
  		} else {
  			/* No IPsec processing for this packet. */
  		}
  	}
  done:
  	if (sp != NULL)
  		KEY_FREESP(&sp);
  	return 0;
  reinjected:
  	if (sp != NULL)
  		KEY_FREESP(&sp);
  	return -1;
  bad:
  	if (sp != NULL)
  		KEY_FREESP(&sp);
  	return 1;
  #endif /* IPSEC */
  	return 0;
  }
  