xt_conntrack.c

/*
 *	xt_conntrack - Netfilter module to match connection tracking
 *	information. (Superset of Rusty's minimalistic state match.)
 *
 *	(C) 2001  Marc Boucher (marc@mbsi.ca).
 *	Copyright © CC Computer Consultants GmbH, 2007 - 2008
 *	Jan Engelhardt <jengelh@computergmbh.de>
 *
 *	This program is free software; you can redistribute it and/or modify
 *	it under the terms of the GNU General Public License version 2 as
 *	published by the Free Software Foundation.
 */

#include <linux/module.h>
#include <linux/skbuff.h>
#include <net/ipv6.h>
#include <linux/netfilter/x_tables.h>
#include <linux/netfilter/xt_conntrack.h>
#include <net/netfilter/nf_conntrack.h>

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Marc Boucher <marc@mbsi.ca>");
MODULE_DESCRIPTION("Xtables: connection tracking state match");
MODULE_ALIAS("ipt_conntrack");
MODULE_ALIAS("ip6t_conntrack");

static bool
conntrack_mt_v0(const struct sk_buff *skb, const struct net_device *in,
                const struct net_device *out, const struct xt_match *match,
                const void *matchinfo, int offset, unsigned int protoff,
                bool *hotdrop)
{
	const struct xt_conntrack_info *sinfo = matchinfo;
	const struct nf_conn *ct;
	enum ip_conntrack_info ctinfo;
	unsigned int statebit;

	ct = nf_ct_get(skb, &ctinfo);

#define FWINV(bool, invflg) ((bool) ^ !!(sinfo->invflags & (invflg)))

	if (ct == &nf_conntrack_untracked)
		statebit = XT_CONNTRACK_STATE_UNTRACKED;
	else if (ct)
		statebit = XT_CONNTRACK_STATE_BIT(ctinfo);
	else
		statebit = XT_CONNTRACK_STATE_INVALID;

	if (sinfo->flags & XT_CONNTRACK_STATE) {
		if (ct) {
			if (test_bit(IPS_SRC_NAT_BIT, &ct->status))
				statebit |= XT_CONNTRACK_STATE_SNAT;
			if (test_bit(IPS_DST_NAT_BIT, &ct->status))
				statebit |= XT_CONNTRACK_STATE_DNAT;
		}
		if (FWINV((statebit & sinfo->statemask) == 0,
			  XT_CONNTRACK_STATE))
			return false;
	}

	if (ct == NULL) {
		if (sinfo->flags & ~XT_CONNTRACK_STATE)
			return false;
		return true;
	}

	if (sinfo->flags & XT_CONNTRACK_PROTO &&
	    FWINV(ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.protonum !=
		  sinfo->tuple[IP_CT_DIR_ORIGINAL].dst.protonum,
		  XT_CONNTRACK_PROTO))
		return false;

	if (sinfo->flags & XT_CONNTRACK_ORIGSRC &&
	    FWINV((ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip &
		   sinfo->sipmsk[IP_CT_DIR_ORIGINAL].s_addr) !=
		  sinfo->tuple[IP_CT_DIR_ORIGINAL].src.ip,
		  XT_CONNTRACK_ORIGSRC))
		return false;

	if (sinfo->flags & XT_CONNTRACK_ORIGDST &&
	    FWINV((ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.u3.ip &
		   sinfo->dipmsk[IP_CT_DIR_ORIGINAL].s_addr) !=
		  sinfo->tuple[IP_CT_DIR_ORIGINAL].dst.ip,
		  XT_CONNTRACK_ORIGDST))
		return false;

	if (sinfo->flags & XT_CONNTRACK_REPLSRC &&
	    FWINV((ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.u3.ip &
		   sinfo->sipmsk[IP_CT_DIR_REPLY].s_addr) !=
		  sinfo->tuple[IP_CT_DIR_REPLY].src.ip,
		  XT_CONNTRACK_REPLSRC))
		return false;

	if (sinfo->flags & XT_CONNTRACK_REPLDST &&
	    FWINV((ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3.ip &
		   sinfo->dipmsk[IP_CT_DIR_REPLY].s_addr) !=
		  sinfo->tuple[IP_CT_DIR_REPLY].dst.ip,
		  XT_CONNTRACK_REPLDST))
		return false;

	if (sinfo->flags & XT_CONNTRACK_STATUS &&
	    FWINV((ct->status & sinfo->statusmask) == 0,
		  XT_CONNTRACK_STATUS))
		return false;

	if(sinfo->flags & XT_CONNTRACK_EXPIRES) {
		unsigned long expires = timer_pending(&ct->timeout) ?
					(ct->timeout.expires - jiffies)/HZ : 0;

		if (FWINV(!(expires >= sinfo->expires_min &&
			    expires <= sinfo->expires_max),
			  XT_CONNTRACK_EXPIRES))
			return false;
	}
	return true;
#undef FWINV
}

static bool
conntrack_addrcmp(const union nf_inet_addr *kaddr,
                  const union nf_inet_addr *uaddr,
                  const union nf_inet_addr *umask, unsigned int l3proto)
{
	if (l3proto == AF_INET)
		return (kaddr->ip & umask->ip) == uaddr->ip;
	else if (l3proto == AF_INET6)
		return ipv6_masked_addr_cmp(&kaddr->in6, &umask->in6,
		       &uaddr->in6) == 0;
	else
		return false;
}

static inline bool
conntrack_mt_origsrc(const struct nf_conn *ct,
                     const struct xt_conntrack_mtinfo1 *info,
                     unsigned int family)
{
	return conntrack_addrcmp(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3,
	       &info->origsrc_addr, &info->origsrc_mask, family);
}

static inline bool
conntrack_mt_origdst(const struct nf_conn *ct,
                     const struct xt_conntrack_mtinfo1 *info,
                     unsigned int family)
{
	return conntrack_addrcmp(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.u3,
	       &info->origdst_addr, &info->origdst_mask, family);
}

static inline bool
conntrack_mt_replsrc(const struct nf_conn *ct,
                     const struct xt_conntrack_mtinfo1 *info,
                     unsigned int family)
{
	return conntrack_addrcmp(&ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.u3,
	       &info->replsrc_addr, &info->replsrc_mask, family);
}

static inline bool
conntrack_mt_repldst(const struct nf_conn *ct,
                     const struct xt_conntrack_mtinfo1 *info,
                     unsigned int family)
{
	return conntrack_addrcmp(&ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3,
	       &info->repldst_addr, &info->repldst_mask, family);
}

static bool
conntrack_mt(const struct sk_buff *skb, const struct net_device *in,
             const struct net_device *out, const struct xt_match *match,
             const void *matchinfo, int offset, unsigned int protoff,
             bool *hotdrop)
{
	const struct xt_conntrack_mtinfo1 *info = matchinfo;
	enum ip_conntrack_info ctinfo;
	const struct nf_conn *ct;
	unsigned int statebit;

	ct = nf_ct_get(skb, &ctinfo);

	if (ct == &nf_conntrack_untracked)
		statebit = XT_CONNTRACK_STATE_UNTRACKED;
	else if (ct != NULL)
		statebit = XT_CONNTRACK_STATE_BIT(ctinfo);
	else
		statebit = XT_CONNTRACK_STATE_INVALID;

	if (info->match_flags & XT_CONNTRACK_STATE) {
		if (ct != NULL) {
			if (test_bit(IPS_SRC_NAT_BIT, &ct->status))
				statebit |= XT_CONNTRACK_STATE_SNAT;
			if (test_bit(IPS_DST_NAT_BIT, &ct->status))
				statebit |= XT_CONNTRACK_STATE_DNAT;
		}
		if ((info->state_mask & statebit) ^
		    !(info->invert_flags & XT_CONNTRACK_STATE))
			return false;
	}

	if (ct == NULL)
		return info->match_flags & XT_CONNTRACK_STATE;

	if ((info->match_flags & XT_CONNTRACK_PROTO) &&
	    ((ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.protonum ==
	    info->l4proto) ^ !(info->invert_flags & XT_CONNTRACK_PROTO)))
		return false;

	if (info->match_flags & XT_CONNTRACK_ORIGSRC)
		if (conntrack_mt_origsrc(ct, info, match->family) ^
		    !(info->invert_flags & XT_CONNTRACK_ORIGSRC))
			return false;

	if (info->match_flags & XT_CONNTRACK_ORIGDST)
		if (conntrack_mt_origdst(ct, info, match->family) ^
		    !(info->invert_flags & XT_CONNTRACK_ORIGDST))
			return false;

	if (info->match_flags & XT_CONNTRACK_REPLSRC)
		if (conntrack_mt_replsrc(ct, info, match->family) ^
		    !(info->invert_flags & XT_CONNTRACK_REPLSRC))
			return false;

	if (info->match_flags & XT_CONNTRACK_REPLDST)
		if (conntrack_mt_repldst(ct, info, match->family) ^
		    !(info->invert_flags & XT_CONNTRACK_REPLDST))
			return false;

	if ((info->match_flags & XT_CONNTRACK_STATUS) &&
	    (!!(info->status_mask & ct->status) ^
	    !(info->invert_flags & XT_CONNTRACK_STATUS)))
		return false;

	if (info->match_flags & XT_CONNTRACK_EXPIRES) {
		unsigned long expires = 0;

		if (timer_pending(&ct->timeout))
			expires = (ct->timeout.expires - jiffies) / HZ;
		if ((expires >= info->expires_min &&
		    expires <= info->expires_max) ^
		    !(info->invert_flags & XT_CONNTRACK_EXPIRES))
			return false;
	}
	return true;
}

static bool
conntrack_mt_check(const char *tablename, const void *ip,
                   const struct xt_match *match, void *matchinfo,
                   unsigned int hook_mask)
{
	if (nf_ct_l3proto_try_module_get(match->family) < 0) {
		printk(KERN_WARNING "can't load conntrack support for "
				    "proto=%u\n", match->family);
		return false;
	}
	return true;
}

static void
conntrack_mt_destroy(const struct xt_match *match, void *matchinfo)
{
	nf_ct_l3proto_module_put(match->family);
}

#ifdef CONFIG_COMPAT
struct compat_xt_conntrack_info
{
	compat_uint_t			statemask;
	compat_uint_t			statusmask;
	struct ip_conntrack_old_tuple	tuple[IP_CT_DIR_MAX];
	struct in_addr			sipmsk[IP_CT_DIR_MAX];
	struct in_addr			dipmsk[IP_CT_DIR_MAX];
	compat_ulong_t			expires_min;
	compat_ulong_t			expires_max;
	u_int8_t			flags;
	u_int8_t			invflags;
};

static void conntrack_mt_compat_from_user_v0(void *dst, void *src)
{
	const struct compat_xt_conntrack_info *cm = src;
	struct xt_conntrack_info m = {
		.statemask	= cm->statemask,
		.statusmask	= cm->statusmask,
		.expires_min	= cm->expires_min,
		.expires_max	= cm->expires_max,
		.flags		= cm->flags,
		.invflags	= cm->invflags,
	};
	memcpy(m.tuple, cm->tuple, sizeof(m.tuple));
	memcpy(m.sipmsk, cm->sipmsk, sizeof(m.sipmsk));
	memcpy(m.dipmsk, cm->dipmsk, sizeof(m.dipmsk));
	memcpy(dst, &m, sizeof(m));
}

static int conntrack_mt_compat_to_user_v0(void __user *dst, void *src)
{
	const struct xt_conntrack_info *m = src;
	struct compat_xt_conntrack_info cm = {
		.statemask	= m->statemask,
		.statusmask	= m->statusmask,
		.expires_min	= m->expires_min,
		.expires_max	= m->expires_max,
		.flags		= m->flags,
		.invflags	= m->invflags,
	};
	memcpy(cm.tuple, m->tuple, sizeof(cm.tuple));
	memcpy(cm.sipmsk, m->sipmsk, sizeof(cm.sipmsk));
	memcpy(cm.dipmsk, m->dipmsk, sizeof(cm.dipmsk));
	return copy_to_user(dst, &cm, sizeof(cm)) ? -EFAULT : 0;
}
#endif

static struct xt_match conntrack_mt_reg[] __read_mostly = {
	{
		.name       = "conntrack",
		.revision   = 0,
		.family     = AF_INET,
		.match      = conntrack_mt_v0,
		.checkentry = conntrack_mt_check,
		.destroy    = conntrack_mt_destroy,
		.matchsize  = sizeof(struct xt_conntrack_info),
		.me         = THIS_MODULE,
#ifdef CONFIG_COMPAT
		.compatsize       = sizeof(struct compat_xt_conntrack_info),
		.compat_from_user = conntrack_mt_compat_from_user_v0,
		.compat_to_user   = conntrack_mt_compat_to_user_v0,
#endif
	},
	{
		.name       = "conntrack",
		.revision   = 1,
		.family     = AF_INET,
		.matchsize  = sizeof(struct xt_conntrack_mtinfo1),
		.match      = conntrack_mt,
		.checkentry = conntrack_mt_check,
		.destroy    = conntrack_mt_destroy,
		.me         = THIS_MODULE,
	},
	{
		.name       = "conntrack",
		.revision   = 1,
		.family     = AF_INET6,
		.matchsize  = sizeof(struct xt_conntrack_mtinfo1),
		.match      = conntrack_mt,
		.checkentry = conntrack_mt_check,
		.destroy    = conntrack_mt_destroy,
		.me         = THIS_MODULE,
	},
};

static int __init conntrack_mt_init(void)
{
	return xt_register_matches(conntrack_mt_reg,
	       ARRAY_SIZE(conntrack_mt_reg));
}

static void __exit conntrack_mt_exit(void)
{
	xt_unregister_matches(conntrack_mt_reg, ARRAY_SIZE(conntrack_mt_reg));
}

module_init(conntrack_mt_init);
module_exit(conntrack_mt_exit);