// SPDX-License-Identifier: GPL-2.0-only
/* 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 <coreteam@netfilter.org>
 */
#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 <coreteam@netfilter.org>");
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);

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

                        switch (minfo->flags) {
                        case XT_MULTIPORT_SOURCE:
                                if (src == s)
                                        return true ^ minfo->invert;
                                break;
                        case XT_MULTIPORT_DESTINATION:
                                if (dst == s)
                                        return true ^ minfo->invert;
                                break;
                        case XT_MULTIPORT_EITHER:
                                if (src == s || dst == s)
                                        return true ^ minfo->invert;
                                break;
                        default:
                                break;
                        }
                }
        }

        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);