Move the IPSEC related code blocks to their own file to unclutter

and signifincantly improve the readability of ip_input() and
ip_output() again.

The resulting IPSEC hooks in ip_input() and ip_output() may be
used later on for making IPSEC loadable.

This move is mostly mechanical and should preserve current IPSEC
behaviour as-is.  Nothing shall prevent improvements in the way
IPSEC interacts with the IPv4 stack.

Discussed with:	bz, gnn, rwatson; (earlier version)

1 files changed, 579 insertions, 0 deletions

diff --git a/sys/netinet/ip_ipsec.c b/sys/netinet/ip_ipsec.c
new file mode 100644
index 0000000..eee144f
--- /dev/null
+++ b/sys/netinet/ip_ipsec.c
@@ -0,0 +1,579 @@
+/*-
+ * 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.
+ *
+ * $FreeBSD$
+ */
+
+#include "opt_ipsec.h"
+
+#include <sys/param.h>
+#include <sys/systm.h>
+#include <sys/kernel.h>
+#include <sys/mac.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 <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>
+
+#include <machine/in_cksum.h>
+
+#ifdef IPSEC
+#include <netinet6/ipsec.h>
+#include <netkey/key.h>
+#ifdef IPSEC_DEBUG
+#include <netkey/key_debug.h>
+#else
+#define	KEYDEBUG(lev,arg)
+#endif
+#endif /*IPSEC*/
+
+#ifdef FAST_IPSEC
+#include <netipsec/ipsec.h>
+#include <netipsec/xform.h>
+#include <netipsec/key.h>
+#endif /*FAST_IPSEC*/
+
+extern	struct protosw inetsw[];
+
+/*
+ * 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_filtergif(struct mbuf *m)
+{
+#if defined(IPSEC) && !defined(IPSEC_FILTERGIF)
+	/*
+	 * Bypass packet filtering for packets from a tunnel (gif).
+	 */
+	if (ipsec_getnhist(m))
+		return 1;
+#endif
+#if defined(FAST_IPSEC) && !defined(IPSEC_FILTERGIF)
+	/*
+	 * Bypass packet filtering for packets from a tunnel (gif).
+	 */
+	if (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 FAST_IPSEC
+	struct m_tag *mtag;
+	struct tdb_ident *tdbi;
+	struct secpolicy *sp;
+	int s, error;
+#endif /* FAST_IPSEC */
+#ifdef IPSEC
+	/*
+	 * Enforce inbound IPsec SPD.
+	 */
+	if (ipsec4_in_reject(m, NULL)) {
+		ipsecstat.in_polvio++;
+		return 1;
+	}
+#endif /* IPSEC */
+#ifdef FAST_IPSEC
+	mtag = m_tag_find(m, PACKET_TAG_IPSEC_IN_DONE, NULL);
+	s = splnet();
+	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 */
+		splx(s);
+		/*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);
+	splx(s);
+	if (error) {
+		ipstat.ips_cantforward++;
+		return 1;
+	}
+#endif /* FAST_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)
+{
+	struct ip *ip = mtod(m, struct ip *);
+#ifdef FAST_IPSEC
+	struct m_tag *mtag;
+	struct tdb_ident *tdbi;
+	struct secpolicy *sp;
+	int s, error;
+#endif /* FAST_IPSEC */
+#ifdef IPSEC
+	/*
+	 * 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 &&
+	    ipsec4_in_reject(m, NULL)) {
+		ipsecstat.in_polvio++;
+		return 1;
+	}
+#endif
+#ifdef FAST_IPSEC
+	/*
+	 * 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);
+		s = splnet();
+		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;
+		}
+		splx(s);
+		if (error)
+			return 1;
+	}
+#endif /* FAST_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 = 0;
+	/*
+	 * 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;
+#ifdef IPSEC
+	sp = ipsec4_getpolicybyaddr(m,
+				    IPSEC_DIR_OUTBOUND,
+				    IP_FORWARDING,
+				    &ipsecerror);
+#else /* FAST_IPSEC */
+	sp = ipsec_getpolicybyaddr(m,
+				   IPSEC_DIR_OUTBOUND,
+				   IP_FORWARDING,
+				   &ipsecerror);
+#endif
+	if (sp != NULL) {
+		/* count IPsec header size */
+		ipsechdr = ipsec4_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->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;
+			}
+		}
+#ifdef IPSEC
+		key_freesp(sp);
+#else /* FAST_IPSEC */
+		KEY_FREESP(&sp);
+#endif
+	}
+	return mtu;
+}
+
+/*
+ * 
+ * Called from ip_output().
+ * 1 = drop packet, 0 = continue processing packet,
+ * -1 = packet was reinjected and stop processing packet (FAST_IPSEC only)
+ */
+int
+ip_ipsec_output(struct mbuf **m, struct inpcb *inp, int *flags, int *error,
+	     struct route **ro, struct route *iproute, struct sockaddr_in **dst,
+	     struct in_ifaddr **ia, struct ifnet **ifp)
+{
+	struct secpolicy *sp = NULL;
+	struct ip *ip = mtod(*m, struct ip *);
+#ifdef IPSEC
+	struct ipsec_output_state state;
+#endif
+#ifdef FAST_IPSEC
+	struct tdb_ident *tdbi;
+	struct m_tag *mtag;
+	int s;
+#endif /* FAST_IPSEC */
+#ifdef IPSEC
+	/* get SP for this packet */
+	if (inp == NULL)
+		sp = ipsec4_getpolicybyaddr(*m, IPSEC_DIR_OUTBOUND,
+		    *flags, error);
+	else
+		sp = ipsec4_getpolicybypcb(*m, IPSEC_DIR_OUTBOUND, inp, error);
+
+	if (sp == NULL) {
+		ipsecstat.out_inval++;
+		goto bad;
+	}
+
+	/* check policy */
+	switch (sp->policy) {
+	case IPSEC_POLICY_DISCARD:
+		/*
+		 * This packet is just discarded.
+		 */
+		ipsecstat.out_polvio++;
+		goto bad;
+
+	case IPSEC_POLICY_BYPASS:
+	case IPSEC_POLICY_NONE:
+	case IPSEC_POLICY_TCP:
+		/* no need to do IPsec. */
+		goto done;
+	
+	case IPSEC_POLICY_IPSEC:
+		if (sp->req == NULL) {
+			/* acquire a policy */
+			*error = key_spdacquire(sp);
+			goto bad;
+		}
+		break;
+
+	case IPSEC_POLICY_ENTRUST:
+	default:
+		printf("%s: Invalid policy found. %d\n", __func__, sp->policy);
+	}
+
+	bzero(&state, sizeof(state));
+	state.m = *m;
+	if (*flags & IP_ROUTETOIF) {
+		state.ro = iproute;
+		bzero(iproute, sizeof(iproute));
+	} else
+		state.ro = *ro;
+	state.dst = (struct sockaddr *)(*dst);
+
+	ip->ip_sum = 0;
+
+	/*
+	 * XXX
+	 * delayed checksums are not currently compatible with IPsec
+	 */
+	if ((*m)->m_pkthdr.csum_flags & CSUM_DELAY_DATA) {
+		in_delayed_cksum(*m);
+		(*m)->m_pkthdr.csum_flags &= ~CSUM_DELAY_DATA;
+	}
+
+	ip->ip_len = htons(ip->ip_len);
+	ip->ip_off = htons(ip->ip_off);
+
+	*error = ipsec4_output(&state, sp, *flags);
+
+	*m = state.m;
+	if (*flags & IP_ROUTETOIF) {
+		/*
+		 * if we have tunnel mode SA, we may need to ignore
+		 * IP_ROUTETOIF.
+		 */
+		if (state.ro != iproute || state.ro->ro_rt != NULL) {
+			*flags &= ~IP_ROUTETOIF;
+			*ro = state.ro;
+		}
+	} else
+		*ro = state.ro;
+	*dst = (struct sockaddr_in *)state.dst;
+	if (*error != 0) {
+		/* mbuf is already reclaimed in ipsec4_output. */
+		*m = NULL;
+		switch (*error) {
+		case EHOSTUNREACH:
+		case ENETUNREACH:
+		case EMSGSIZE:
+		case ENOBUFS:
+		case ENOMEM:
+			break;
+		default:
+			printf("ip4_output (ipsec): error code %d\n", *error);
+			/*fall through*/
+		case ENOENT:
+			/* don't show these error codes to the user */
+			*error = 0;
+			break;
+		}
+		goto bad;
+	}
+
+	/* be sure to update variables that are affected by ipsec4_output() */
+	if ((*ro)->ro_rt == NULL) {
+		if ((*flags & IP_ROUTETOIF) == 0) {
+			printf("ip_output: "
+				"can't update route after IPsec processing\n");
+			*error = EHOSTUNREACH;	/*XXX*/
+			goto bad;
+		}
+	} else {
+		if (state.encap) {
+			*ia = ifatoia((*ro)->ro_rt->rt_ifa);
+			*ifp = (*ro)->ro_rt->rt_ifp;
+		}
+	}
+
+	/* make it flipped, again. */
+	ip->ip_len = ntohs(ip->ip_len);
+	ip->ip_off = ntohs(ip->ip_off);
+
+done:
+	if (sp != NULL) {
+		KEYDEBUG(KEYDEBUG_IPSEC_STAMP,
+			printf("DP ip_output call free SP:%p\n", sp));
+		key_freesp(sp);
+	}
+	return 0;
+bad:
+	if (sp != NULL) {
+		KEYDEBUG(KEYDEBUG_IPSEC_STAMP,
+			printf("DP ip_output call free SP:%p\n", sp));
+		key_freesp(sp);
+	}
+	return 1;
+#endif /*IPSEC*/
+#ifdef FAST_IPSEC
+	/*
+	 * 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);
+	s = splnet();
+	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;
+				splx(s);
+				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;
+		}
+
+		ip->ip_len = htons(ip->ip_len);
+		ip->ip_off = htons(ip->ip_off);
+
+		/* NB: callee frees mbuf */
+		*error = ipsec4_process_packet(*m, sp->req, *flags, 0);
+		/*
+		 * 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;
+		splx(s);
+		goto reinjected;
+	} else {	/* sp == NULL */
+		splx(s);
+
+		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. */
+		}
+#ifdef notyet
+		/*
+		 * If deferred crypto processing is needed, check that
+		 * the interface supports it.
+		 */ 
+		mtag = m_tag_find(*m, PACKET_TAG_IPSEC_OUT_CRYPTO_NEEDED, NULL);
+		if (mtag != NULL && ((*ifp)->if_capenable & IFCAP_IPSEC) == 0) {
+			/* notify IPsec to do its own crypto */
+			ipsp_skipcrypto_unmark((struct tdb_ident *)(mtag + 1));
+			*error = EHOSTUNREACH;
+			goto bad;
+		}
+#endif
+	}
+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 /* FAST_IPSEC */
+	return 0;
+}
+