Add a pseudo interface for packet filtering IPSec connections before or after

encryption. There are two functions, a bpf tap which has a basic header with
the SPI number which our current tcpdump knows how to display, and handoff to
pfil(9) for packet filtering.

Obtained from:	OpenBSD
Based on:	kern/94829
No objections:	arch, net
MFC after:	1 month

2 files changed, 324 insertions, 0 deletions

diff --git a/sys/net/if_enc.c b/sys/net/if_enc.c
new file mode 100644
index 0000000..0aaf4aa
--- /dev/null
+++ b/sys/net/if_enc.c
@@ -0,0 +1,323 @@
+/*-
+ * Copyright (c) 2006 The FreeBSD Project.
+ * 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.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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 <sys/param.h>
+#include <sys/systm.h>
+#include <sys/kernel.h>
+#include <sys/malloc.h>
+#include <sys/mbuf.h>
+#include <sys/module.h>
+#include <machine/bus.h>
+#include <sys/rman.h>
+#include <sys/socket.h>
+#include <sys/sockio.h>
+#include <sys/sysctl.h>
+
+#include <net/if.h>
+#include <net/if_clone.h>
+#include <net/if_types.h>
+#include <net/pfil.h>
+#include <net/route.h>
+#include <net/netisr.h>
+#include <net/bpf.h>
+#include <net/bpfdesc.h>
+
+#include <netinet/in.h>
+#include <netinet/in_systm.h>
+#include <netinet/ip.h>
+#include <netinet/ip_var.h>
+#include <netinet/in_var.h>
+#include "opt_inet6.h"
+
+#ifdef INET6
+#include <netinet/ip6.h>
+#include <netinet6/ip6_var.h>
+#endif
+
+#include <netipsec/ipsec.h>
+
+#define ENCMTU		(1024+512)
+#define ENC_HDRLEN	12
+
+/* XXX this define must have the same value as in OpenBSD */
+#define M_CONF		0x0400	/* payload was encrypted (ESP-transport) */
+#define M_AUTH		0x0800	/* payload was authenticated (AH or ESP auth) */
+#define M_AUTH_AH	0x2000	/* header was authenticated (AH) */
+
+struct enchdr {
+	u_int32_t af;
+	u_int32_t spi;
+	u_int32_t flags;
+};
+
+static struct ifnet	*encif;
+static struct mtx	enc_mtx;
+
+struct enc_softc {
+	struct	ifnet *sc_ifp;
+};
+
+static int	enc_ioctl(struct ifnet *, u_long, caddr_t);
+static int	enc_output(struct ifnet *ifp, struct mbuf *m,
+		    struct sockaddr *dst, struct rtentry *rt);
+static int	enc_clone_create(struct if_clone *, int);
+static void	enc_clone_destroy(struct ifnet *);
+
+IFC_SIMPLE_DECLARE(enc, 1);
+
+static void
+enc_clone_destroy(struct ifnet *ifp)
+{
+
+	KASSERT(encif == ifp, ("%s: unknown ifnet", __func__));
+
+	mtx_lock(&enc_mtx);
+	encif = NULL;
+	mtx_unlock(&enc_mtx);
+
+	bpfdetach(ifp);
+	if_detach(ifp);
+	if_free(ifp);
+
+}
+
+static int
+enc_clone_create(struct if_clone *ifc, int unit)
+{
+	struct ifnet *ifp;
+	struct enc_softc *sc;
+
+	mtx_lock(&enc_mtx);
+	if (encif != NULL)
+		return (EBUSY);
+	mtx_unlock(&enc_mtx);
+
+	sc = malloc(sizeof(*sc), M_DEVBUF, M_WAITOK|M_ZERO);
+	ifp = sc->sc_ifp = if_alloc(IFT_ENC);
+	if (ifp == NULL) {
+		free(sc, M_DEVBUF);
+		return (ENOSPC);
+	}
+
+	if_initname(ifp, ifc->ifc_name, unit);
+	ifp->if_mtu = ENCMTU;
+	ifp->if_ioctl = enc_ioctl;
+	ifp->if_output = enc_output;
+	ifp->if_snd.ifq_maxlen = ifqmaxlen;
+	ifp->if_softc = sc;
+	if_attach(ifp);
+	bpfattach(ifp, DLT_ENC, ENC_HDRLEN);
+
+	mtx_lock(&enc_mtx);
+	encif = ifp;
+	mtx_unlock(&enc_mtx);
+
+	return (0);
+}
+
+static int
+enc_modevent(module_t mod, int type, void *data)
+{
+	switch (type) {
+	case MOD_LOAD:
+		mtx_init(&enc_mtx, "enc mtx", NULL, MTX_DEF);
+		if_clone_attach(&enc_cloner);
+		break;
+	case MOD_UNLOAD:
+		printf("enc module unload - not possible for this module\n");
+		return (EINVAL);
+	default:
+		return (EOPNOTSUPP);
+	}
+	return (0);
+}
+
+static moduledata_t enc_mod = {
+	"enc",
+	enc_modevent,
+	0
+};
+
+DECLARE_MODULE(enc, enc_mod, SI_SUB_PROTO_IFATTACHDOMAIN, SI_ORDER_ANY);
+
+static int
+enc_output(struct ifnet *ifp, struct mbuf *m, struct sockaddr *dst,
+    struct rtentry *rt)
+{
+	m_freem(m);
+	return (0);
+}
+
+/*
+ * Process an ioctl request.
+ */
+/* ARGSUSED */
+static int
+enc_ioctl(struct ifnet *ifp, u_long cmd, caddr_t data)
+{
+	int error = 0;
+
+	switch (cmd) {
+
+	case SIOCSIFFLAGS:
+		if (ifp->if_flags & IFF_UP)
+			ifp->if_drv_flags |= IFF_DRV_RUNNING;
+		else
+			ifp->if_drv_flags &= ~IFF_DRV_RUNNING;
+
+		break;
+
+	default:
+		error = EINVAL;
+	}
+	return (error);
+}
+
+int
+ipsec_filter(struct mbuf **mp, int dir)
+{
+	int error, i;
+	struct ip *ip;
+
+	mtx_lock(&enc_mtx);
+	if (encif == NULL || (encif->if_drv_flags & IFF_DRV_RUNNING) == 0) {
+		mtx_unlock(&enc_mtx);
+		return (0);
+	}
+
+	/* Skip pfil(9) if no filters are loaded */
+	if (!(PFIL_HOOKED(&inet_pfil_hook)
+#ifdef INET6
+	    || PFIL_HOOKED(&inet6_pfil_hook)
+#endif
+	    )) {
+		mtx_unlock(&enc_mtx);
+		return (0);
+	}
+
+	i = min((*mp)->m_pkthdr.len, max_protohdr);
+	if ((*mp)->m_len < i) {
+		*mp = m_pullup(*mp, i);
+		if (*mp == NULL) {
+			printf("%s: m_pullup failed\n", __func__);
+			mtx_unlock(&enc_mtx);
+			return (-1);
+		}
+	}
+
+	error = 0;
+	ip = mtod(*mp, struct ip *);
+	switch (ip->ip_v) {
+		case 4:
+			/*
+			 * before calling the firewall, swap fields the same as
+			 * IP does. here we assume the header is contiguous
+			 */
+			ip->ip_len = ntohs(ip->ip_len);
+			ip->ip_off = ntohs(ip->ip_off);
+
+			error = pfil_run_hooks(&inet_pfil_hook, mp,
+			    encif, dir, NULL);
+
+			if (*mp == NULL || error != 0)
+				break;
+
+			/* restore byte ordering */
+			ip = mtod(*mp, struct ip *);
+			ip->ip_len = htons(ip->ip_len);
+			ip->ip_off = htons(ip->ip_off);
+			break;
+
+#ifdef INET6
+		case 6:
+			error = pfil_run_hooks(&inet6_pfil_hook, mp,
+			    encif, dir, NULL);
+			break;
+#endif
+		default:
+			printf("%s: unknown IP version\n", __func__);
+	}
+
+	mtx_unlock(&enc_mtx);
+	if (*mp == NULL)
+		return (error);
+	if (error != 0)
+		goto bad;
+
+	return (error);
+
+bad:
+	mtx_unlock(&enc_mtx);
+	m_freem(*mp);
+	*mp = NULL;
+	return (error);
+}
+
+void
+ipsec_bpf(struct mbuf *m, struct secasvar *sav, int af)
+{
+	int flags;
+	struct enchdr hdr;
+	struct mbuf m1;
+
+	KASSERT(sav != NULL, ("%s: sav is null", __func__));
+
+	mtx_lock(&enc_mtx);
+	if (encif == NULL || (encif->if_drv_flags & IFF_DRV_RUNNING) == 0) {
+		mtx_unlock(&enc_mtx);
+		return;
+	}
+
+	if (encif->if_bpf) {
+		flags = 0;
+		if (sav->alg_enc != SADB_EALG_NONE)
+			flags |= M_CONF;
+		if (sav->alg_auth != SADB_AALG_NONE)
+			flags |= M_AUTH;
+
+		/*
+		 * We need to prepend the address family as a four byte
+		 * field.  Cons up a dummy header to pacify bpf.  This
+		 * is safe because bpf will only read from the mbuf
+		 * (i.e., it won't try to free it or keep a pointer a
+		 * to it).
+		 */
+		hdr.af = af;
+		hdr.spi = sav->spi;
+		hdr.flags = flags;
+
+		m1.m_flags = 0;
+		m1.m_next = m;
+		m1.m_len = ENC_HDRLEN;
+		m1.m_data = (char *) &hdr;
+
+		bpf_mtap(encif->if_bpf, &m1);
+	}
+	mtx_unlock(&enc_mtx);
+}
diff --git a/sys/net/if_types.h b/sys/net/if_types.h
index 2d25b69..4c37c49 100644
--- a/sys/net/if_types.h
+++ b/sys/net/if_types.h
@@ -246,6 +246,7 @@
 #define	IFT_GIF		0xf0
 #define	IFT_PVC		0xf1
 #define	IFT_FAITH	0xf2
+#define	IFT_ENC		0xf4
 #define	IFT_PFLOG	0xf6
 #define	IFT_PFSYNC	0xf7
 #define	IFT_CARP	0xf8	/* Common Address Redundancy Protocol */