xt_multiport.c

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/* Kernel module to match one of a list of TCP/UDP(-Lite)/SCTP/DCCP ports:
   ports are in the same place so we can treat them as equal. */

/* (C) 1999-2001 Paul `Rusty' Russell
 * (C) 2002-2004 Netfilter Core Team <[email protected]>
 *
 * 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.
 */
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/module.h>
#include <linux/types.h>
#include <linux/udp.h>
#include <linux/skbuff.h>
#include <linux/in.h>

#include <linux/netfilter/xt_multiport.h>
#include <linux/netfilter/x_tables.h>
#include <linux/netfilter_ipv4/ip_tables.h>
#include <linux/netfilter_ipv6/ip6_tables.h>

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Netfilter Core Team <[email protected]>");
MODULE_DESCRIPTION("Xtables: multiple port matching for TCP, UDP, UDP-Lite, SCTP and DCCP");
MODULE_ALIAS("ipt_multiport");
MODULE_ALIAS("ip6t_multiport");

/* Returns 1 if the port is matched by the test, 0 otherwise. */
static inline bool
ports_match_v1(const struct xt_multiport_v1 *minfo,
           u_int16_t src, u_int16_t dst)
{
    unsigned int i;
    u_int16_t s, e;

    for (i = 0; i < minfo->count; i++) {
        s = minfo->ports[i];

        if (minfo->pflags[i]) {
            /* range port matching */
            e = minfo->ports[++i];
            pr_debug("src or dst matches with %d-%d?\n", s, e);

            if (minfo->flags == XT_MULTIPORT_SOURCE
                && src >= s && src <= e)
                return true ^ minfo->invert;
            if (minfo->flags == XT_MULTIPORT_DESTINATION
                && dst >= s && dst <= e)
                return true ^ minfo->invert;
            if (minfo->flags == XT_MULTIPORT_EITHER
                && ((dst >= s && dst <= e)
                || (src >= s && src <= e)))
                return true ^ minfo->invert;
        } else {
            /* exact port matching */
            pr_debug("src or dst matches with %d?\n", s);

            if (minfo->flags == XT_MULTIPORT_SOURCE
                && src == s)
                return true ^ minfo->invert;
            if (minfo->flags == XT_MULTIPORT_DESTINATION
                && dst == s)
                return true ^ minfo->invert;
            if (minfo->flags == XT_MULTIPORT_EITHER
                && (src == s || dst == s))
                return true ^ minfo->invert;
        }
    }

    return minfo->invert;
}

static bool
multiport_mt(const struct sk_buff *skb, struct xt_action_param *par)
{
    const __be16 *pptr;
    __be16 _ports[2];
    const struct xt_multiport_v1 *multiinfo = par->matchinfo;

    if (par->fragoff != 0)
        return false;

    pptr = skb_header_pointer(skb, par->thoff, sizeof(_ports), _ports);
    if (pptr == NULL) {
        /* We've been asked to examine this packet, and we
         * can't.  Hence, no choice but to drop.
         */
        pr_debug("Dropping evil offset=0 tinygram.\n");
        par->hotdrop = true;
        return false;
    }

    return ports_match_v1(multiinfo, ntohs(pptr[0]), ntohs(pptr[1]));
}

static inline bool
check(u_int16_t proto,
      u_int8_t ip_invflags,
      u_int8_t match_flags,
      u_int8_t count)
{
    /* Must specify supported protocol, no unknown flags or bad count */
    return (proto == IPPROTO_TCP || proto == IPPROTO_UDP
        || proto == IPPROTO_UDPLITE
        || proto == IPPROTO_SCTP || proto == IPPROTO_DCCP)
        && !(ip_invflags & XT_INV_PROTO)
        && (match_flags == XT_MULTIPORT_SOURCE
            || match_flags == XT_MULTIPORT_DESTINATION
            || match_flags == XT_MULTIPORT_EITHER)
        && count <= XT_MULTI_PORTS;
}

static int multiport_mt_check(const struct xt_mtchk_param *par)
{
    const struct ipt_ip *ip = par->entryinfo;
    const struct xt_multiport_v1 *multiinfo = par->matchinfo;

    return check(ip->proto, ip->invflags, multiinfo->flags,
             multiinfo->count) ? 0 : -EINVAL;
}

static int multiport_mt6_check(const struct xt_mtchk_param *par)
{
    const struct ip6t_ip6 *ip = par->entryinfo;
    const struct xt_multiport_v1 *multiinfo = par->matchinfo;

    return check(ip->proto, ip->invflags, multiinfo->flags,
             multiinfo->count) ? 0 : -EINVAL;
}

static struct xt_match multiport_mt_reg[] __read_mostly = {
    {
        .name       = "multiport",
        .family     = NFPROTO_IPV4,
        .revision   = 1,
        .checkentry = multiport_mt_check,
        .match      = multiport_mt,
        .matchsize  = sizeof(struct xt_multiport_v1),
        .me     = THIS_MODULE,
    },
    {
        .name       = "multiport",
        .family     = NFPROTO_IPV6,
        .revision   = 1,
        .checkentry = multiport_mt6_check,
        .match      = multiport_mt,
        .matchsize  = sizeof(struct xt_multiport_v1),
        .me     = THIS_MODULE,
    },
};

static int __init multiport_mt_init(void)
{
    return xt_register_matches(multiport_mt_reg,
           ARRAY_SIZE(multiport_mt_reg));
}

static void __exit multiport_mt_exit(void)
{
    xt_unregister_matches(multiport_mt_reg, ARRAY_SIZE(multiport_mt_reg));
}

module_init(multiport_mt_init);
module_exit(multiport_mt_exit);