linux/net/netfilter/xt_socket.c
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   1/*
   2 * Transparent proxy support for Linux/iptables
   3 *
   4 * Copyright (C) 2007-2008 BalaBit IT Ltd.
   5 * Author: Krisztian Kovacs
   6 *
   7 * This program is free software; you can redistribute it and/or modify
   8 * it under the terms of the GNU General Public License version 2 as
   9 * published by the Free Software Foundation.
  10 *
  11 */
  12#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  13#include <linux/module.h>
  14#include <linux/skbuff.h>
  15#include <linux/netfilter/x_tables.h>
  16#include <linux/netfilter_ipv4/ip_tables.h>
  17#include <net/tcp.h>
  18#include <net/udp.h>
  19#include <net/icmp.h>
  20#include <net/sock.h>
  21#include <net/inet_sock.h>
  22#include <net/netfilter/nf_tproxy_core.h>
  23#include <net/netfilter/ipv4/nf_defrag_ipv4.h>
  24
  25#if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
  26#define XT_SOCKET_HAVE_IPV6 1
  27#include <linux/netfilter_ipv6/ip6_tables.h>
  28#include <net/netfilter/ipv6/nf_defrag_ipv6.h>
  29#endif
  30
  31#include <linux/netfilter/xt_socket.h>
  32
  33#if IS_ENABLED(CONFIG_NF_CONNTRACK)
  34#define XT_SOCKET_HAVE_CONNTRACK 1
  35#include <net/netfilter/nf_conntrack.h>
  36#endif
  37
  38static void
  39xt_socket_put_sk(struct sock *sk)
  40{
  41        if (sk->sk_state == TCP_TIME_WAIT)
  42                inet_twsk_put(inet_twsk(sk));
  43        else
  44                sock_put(sk);
  45}
  46
  47static int
  48extract_icmp4_fields(const struct sk_buff *skb,
  49                    u8 *protocol,
  50                    __be32 *raddr,
  51                    __be32 *laddr,
  52                    __be16 *rport,
  53                    __be16 *lport)
  54{
  55        unsigned int outside_hdrlen = ip_hdrlen(skb);
  56        struct iphdr *inside_iph, _inside_iph;
  57        struct icmphdr *icmph, _icmph;
  58        __be16 *ports, _ports[2];
  59
  60        icmph = skb_header_pointer(skb, outside_hdrlen,
  61                                   sizeof(_icmph), &_icmph);
  62        if (icmph == NULL)
  63                return 1;
  64
  65        switch (icmph->type) {
  66        case ICMP_DEST_UNREACH:
  67        case ICMP_SOURCE_QUENCH:
  68        case ICMP_REDIRECT:
  69        case ICMP_TIME_EXCEEDED:
  70        case ICMP_PARAMETERPROB:
  71                break;
  72        default:
  73                return 1;
  74        }
  75
  76        inside_iph = skb_header_pointer(skb, outside_hdrlen +
  77                                        sizeof(struct icmphdr),
  78                                        sizeof(_inside_iph), &_inside_iph);
  79        if (inside_iph == NULL)
  80                return 1;
  81
  82        if (inside_iph->protocol != IPPROTO_TCP &&
  83            inside_iph->protocol != IPPROTO_UDP)
  84                return 1;
  85
  86        ports = skb_header_pointer(skb, outside_hdrlen +
  87                                   sizeof(struct icmphdr) +
  88                                   (inside_iph->ihl << 2),
  89                                   sizeof(_ports), &_ports);
  90        if (ports == NULL)
  91                return 1;
  92
  93        /* the inside IP packet is the one quoted from our side, thus
  94         * its saddr is the local address */
  95        *protocol = inside_iph->protocol;
  96        *laddr = inside_iph->saddr;
  97        *lport = ports[0];
  98        *raddr = inside_iph->daddr;
  99        *rport = ports[1];
 100
 101        return 0;
 102}
 103
 104static bool
 105socket_match(const struct sk_buff *skb, struct xt_action_param *par,
 106             const struct xt_socket_mtinfo1 *info)
 107{
 108        const struct iphdr *iph = ip_hdr(skb);
 109        struct udphdr _hdr, *hp = NULL;
 110        struct sock *sk;
 111        __be32 uninitialized_var(daddr), uninitialized_var(saddr);
 112        __be16 uninitialized_var(dport), uninitialized_var(sport);
 113        u8 uninitialized_var(protocol);
 114#ifdef XT_SOCKET_HAVE_CONNTRACK
 115        struct nf_conn const *ct;
 116        enum ip_conntrack_info ctinfo;
 117#endif
 118
 119        if (iph->protocol == IPPROTO_UDP || iph->protocol == IPPROTO_TCP) {
 120                hp = skb_header_pointer(skb, ip_hdrlen(skb),
 121                                        sizeof(_hdr), &_hdr);
 122                if (hp == NULL)
 123                        return false;
 124
 125                protocol = iph->protocol;
 126                saddr = iph->saddr;
 127                sport = hp->source;
 128                daddr = iph->daddr;
 129                dport = hp->dest;
 130
 131        } else if (iph->protocol == IPPROTO_ICMP) {
 132                if (extract_icmp4_fields(skb, &protocol, &saddr, &daddr,
 133                                        &sport, &dport))
 134                        return false;
 135        } else {
 136                return false;
 137        }
 138
 139#ifdef XT_SOCKET_HAVE_CONNTRACK
 140        /* Do the lookup with the original socket address in case this is a
 141         * reply packet of an established SNAT-ted connection. */
 142
 143        ct = nf_ct_get(skb, &ctinfo);
 144        if (ct && !nf_ct_is_untracked(ct) &&
 145            ((iph->protocol != IPPROTO_ICMP &&
 146              ctinfo == IP_CT_ESTABLISHED_REPLY) ||
 147             (iph->protocol == IPPROTO_ICMP &&
 148              ctinfo == IP_CT_RELATED_REPLY)) &&
 149            (ct->status & IPS_SRC_NAT_DONE)) {
 150
 151                daddr = ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip;
 152                dport = (iph->protocol == IPPROTO_TCP) ?
 153                        ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u.tcp.port :
 154                        ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u.udp.port;
 155        }
 156#endif
 157
 158        sk = nf_tproxy_get_sock_v4(dev_net(skb->dev), protocol,
 159                                   saddr, daddr, sport, dport, par->in, NFT_LOOKUP_ANY);
 160        if (sk != NULL) {
 161                bool wildcard;
 162                bool transparent = true;
 163
 164                /* Ignore sockets listening on INADDR_ANY */
 165                wildcard = (sk->sk_state != TCP_TIME_WAIT &&
 166                            inet_sk(sk)->inet_rcv_saddr == 0);
 167
 168                /* Ignore non-transparent sockets,
 169                   if XT_SOCKET_TRANSPARENT is used */
 170                if (info && info->flags & XT_SOCKET_TRANSPARENT)
 171                        transparent = ((sk->sk_state != TCP_TIME_WAIT &&
 172                                        inet_sk(sk)->transparent) ||
 173                                       (sk->sk_state == TCP_TIME_WAIT &&
 174                                        inet_twsk(sk)->tw_transparent));
 175
 176                xt_socket_put_sk(sk);
 177
 178                if (wildcard || !transparent)
 179                        sk = NULL;
 180        }
 181
 182        pr_debug("proto %hhu %pI4:%hu -> %pI4:%hu (orig %pI4:%hu) sock %p\n",
 183                 protocol, &saddr, ntohs(sport),
 184                 &daddr, ntohs(dport),
 185                 &iph->daddr, hp ? ntohs(hp->dest) : 0, sk);
 186
 187        return (sk != NULL);
 188}
 189
 190static bool
 191socket_mt4_v0(const struct sk_buff *skb, struct xt_action_param *par)
 192{
 193        return socket_match(skb, par, NULL);
 194}
 195
 196static bool
 197socket_mt4_v1(const struct sk_buff *skb, struct xt_action_param *par)
 198{
 199        return socket_match(skb, par, par->matchinfo);
 200}
 201
 202#ifdef XT_SOCKET_HAVE_IPV6
 203
 204static int
 205extract_icmp6_fields(const struct sk_buff *skb,
 206                     unsigned int outside_hdrlen,
 207                     int *protocol,
 208                     struct in6_addr **raddr,
 209                     struct in6_addr **laddr,
 210                     __be16 *rport,
 211                     __be16 *lport)
 212{
 213        struct ipv6hdr *inside_iph, _inside_iph;
 214        struct icmp6hdr *icmph, _icmph;
 215        __be16 *ports, _ports[2];
 216        u8 inside_nexthdr;
 217        __be16 inside_fragoff;
 218        int inside_hdrlen;
 219
 220        icmph = skb_header_pointer(skb, outside_hdrlen,
 221                                   sizeof(_icmph), &_icmph);
 222        if (icmph == NULL)
 223                return 1;
 224
 225        if (icmph->icmp6_type & ICMPV6_INFOMSG_MASK)
 226                return 1;
 227
 228        inside_iph = skb_header_pointer(skb, outside_hdrlen + sizeof(_icmph), sizeof(_inside_iph), &_inside_iph);
 229        if (inside_iph == NULL)
 230                return 1;
 231        inside_nexthdr = inside_iph->nexthdr;
 232
 233        inside_hdrlen = ipv6_skip_exthdr(skb, outside_hdrlen + sizeof(_icmph) + sizeof(_inside_iph),
 234                                         &inside_nexthdr, &inside_fragoff);
 235        if (inside_hdrlen < 0)
 236                return 1; /* hjm: Packet has no/incomplete transport layer headers. */
 237
 238        if (inside_nexthdr != IPPROTO_TCP &&
 239            inside_nexthdr != IPPROTO_UDP)
 240                return 1;
 241
 242        ports = skb_header_pointer(skb, inside_hdrlen,
 243                                   sizeof(_ports), &_ports);
 244        if (ports == NULL)
 245                return 1;
 246
 247        /* the inside IP packet is the one quoted from our side, thus
 248         * its saddr is the local address */
 249        *protocol = inside_nexthdr;
 250        *laddr = &inside_iph->saddr;
 251        *lport = ports[0];
 252        *raddr = &inside_iph->daddr;
 253        *rport = ports[1];
 254
 255        return 0;
 256}
 257
 258static bool
 259socket_mt6_v1(const struct sk_buff *skb, struct xt_action_param *par)
 260{
 261        struct ipv6hdr *iph = ipv6_hdr(skb);
 262        struct udphdr _hdr, *hp = NULL;
 263        struct sock *sk;
 264        struct in6_addr *daddr = NULL, *saddr = NULL;
 265        __be16 uninitialized_var(dport), uninitialized_var(sport);
 266        int thoff = 0, uninitialized_var(tproto);
 267        const struct xt_socket_mtinfo1 *info = (struct xt_socket_mtinfo1 *) par->matchinfo;
 268
 269        tproto = ipv6_find_hdr(skb, &thoff, -1, NULL, NULL);
 270        if (tproto < 0) {
 271                pr_debug("unable to find transport header in IPv6 packet, dropping\n");
 272                return NF_DROP;
 273        }
 274
 275        if (tproto == IPPROTO_UDP || tproto == IPPROTO_TCP) {
 276                hp = skb_header_pointer(skb, thoff,
 277                                        sizeof(_hdr), &_hdr);
 278                if (hp == NULL)
 279                        return false;
 280
 281                saddr = &iph->saddr;
 282                sport = hp->source;
 283                daddr = &iph->daddr;
 284                dport = hp->dest;
 285
 286        } else if (tproto == IPPROTO_ICMPV6) {
 287                if (extract_icmp6_fields(skb, thoff, &tproto, &saddr, &daddr,
 288                                         &sport, &dport))
 289                        return false;
 290        } else {
 291                return false;
 292        }
 293
 294        sk = nf_tproxy_get_sock_v6(dev_net(skb->dev), tproto,
 295                                   saddr, daddr, sport, dport, par->in, NFT_LOOKUP_ANY);
 296        if (sk != NULL) {
 297                bool wildcard;
 298                bool transparent = true;
 299
 300                /* Ignore sockets listening on INADDR_ANY */
 301                wildcard = (sk->sk_state != TCP_TIME_WAIT &&
 302                            ipv6_addr_any(&inet6_sk(sk)->rcv_saddr));
 303
 304                /* Ignore non-transparent sockets,
 305                   if XT_SOCKET_TRANSPARENT is used */
 306                if (info && info->flags & XT_SOCKET_TRANSPARENT)
 307                        transparent = ((sk->sk_state != TCP_TIME_WAIT &&
 308                                        inet_sk(sk)->transparent) ||
 309                                       (sk->sk_state == TCP_TIME_WAIT &&
 310                                        inet_twsk(sk)->tw_transparent));
 311
 312                xt_socket_put_sk(sk);
 313
 314                if (wildcard || !transparent)
 315                        sk = NULL;
 316        }
 317
 318        pr_debug("proto %hhd %pI6:%hu -> %pI6:%hu "
 319                 "(orig %pI6:%hu) sock %p\n",
 320                 tproto, saddr, ntohs(sport),
 321                 daddr, ntohs(dport),
 322                 &iph->daddr, hp ? ntohs(hp->dest) : 0, sk);
 323
 324        return (sk != NULL);
 325}
 326#endif
 327
 328static struct xt_match socket_mt_reg[] __read_mostly = {
 329        {
 330                .name           = "socket",
 331                .revision       = 0,
 332                .family         = NFPROTO_IPV4,
 333                .match          = socket_mt4_v0,
 334                .hooks          = (1 << NF_INET_PRE_ROUTING) |
 335                                  (1 << NF_INET_LOCAL_IN),
 336                .me             = THIS_MODULE,
 337        },
 338        {
 339                .name           = "socket",
 340                .revision       = 1,
 341                .family         = NFPROTO_IPV4,
 342                .match          = socket_mt4_v1,
 343                .matchsize      = sizeof(struct xt_socket_mtinfo1),
 344                .hooks          = (1 << NF_INET_PRE_ROUTING) |
 345                                  (1 << NF_INET_LOCAL_IN),
 346                .me             = THIS_MODULE,
 347        },
 348#ifdef XT_SOCKET_HAVE_IPV6
 349        {
 350                .name           = "socket",
 351                .revision       = 1,
 352                .family         = NFPROTO_IPV6,
 353                .match          = socket_mt6_v1,
 354                .matchsize      = sizeof(struct xt_socket_mtinfo1),
 355                .hooks          = (1 << NF_INET_PRE_ROUTING) |
 356                                  (1 << NF_INET_LOCAL_IN),
 357                .me             = THIS_MODULE,
 358        },
 359#endif
 360};
 361
 362static int __init socket_mt_init(void)
 363{
 364        nf_defrag_ipv4_enable();
 365#ifdef XT_SOCKET_HAVE_IPV6
 366        nf_defrag_ipv6_enable();
 367#endif
 368
 369        return xt_register_matches(socket_mt_reg, ARRAY_SIZE(socket_mt_reg));
 370}
 371
 372static void __exit socket_mt_exit(void)
 373{
 374        xt_unregister_matches(socket_mt_reg, ARRAY_SIZE(socket_mt_reg));
 375}
 376
 377module_init(socket_mt_init);
 378module_exit(socket_mt_exit);
 379
 380MODULE_LICENSE("GPL");
 381MODULE_AUTHOR("Krisztian Kovacs, Balazs Scheidler");
 382MODULE_DESCRIPTION("x_tables socket match module");
 383MODULE_ALIAS("ipt_socket");
 384MODULE_ALIAS("ip6t_socket");
 385
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