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 = skb->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        if (!sk)
 159                sk = nf_tproxy_get_sock_v4(dev_net(skb->dev), protocol,
 160                                           saddr, daddr, sport, dport,
 161                                           par->in, NFT_LOOKUP_ANY);
 162        if (sk) {
 163                bool wildcard;
 164                bool transparent = true;
 165
 166                /* Ignore sockets listening on INADDR_ANY,
 167                 * unless XT_SOCKET_NOWILDCARD is set
 168                 */
 169                wildcard = (!(info->flags & XT_SOCKET_NOWILDCARD) &&
 170                            sk->sk_state != TCP_TIME_WAIT &&
 171                            inet_sk(sk)->inet_rcv_saddr == 0);
 172
 173                /* Ignore non-transparent sockets,
 174                   if XT_SOCKET_TRANSPARENT is used */
 175                if (info->flags & XT_SOCKET_TRANSPARENT)
 176                        transparent = ((sk->sk_state != TCP_TIME_WAIT &&
 177                                        inet_sk(sk)->transparent) ||
 178                                       (sk->sk_state == TCP_TIME_WAIT &&
 179                                        inet_twsk(sk)->tw_transparent));
 180
 181                if (sk != skb->sk)
 182                        xt_socket_put_sk(sk);
 183
 184                if (wildcard || !transparent)
 185                        sk = NULL;
 186        }
 187
 188        pr_debug("proto %hhu %pI4:%hu -> %pI4:%hu (orig %pI4:%hu) sock %p\n",
 189                 protocol, &saddr, ntohs(sport),
 190                 &daddr, ntohs(dport),
 191                 &iph->daddr, hp ? ntohs(hp->dest) : 0, sk);
 192
 193        return (sk != NULL);
 194}
 195
 196static bool
 197socket_mt4_v0(const struct sk_buff *skb, struct xt_action_param *par)
 198{
 199        static struct xt_socket_mtinfo1 xt_info_v0 = {
 200                .flags = 0,
 201        };
 202
 203        return socket_match(skb, par, &xt_info_v0);
 204}
 205
 206static bool
 207socket_mt4_v1_v2(const struct sk_buff *skb, struct xt_action_param *par)
 208{
 209        return socket_match(skb, par, par->matchinfo);
 210}
 211
 212#ifdef XT_SOCKET_HAVE_IPV6
 213
 214static int
 215extract_icmp6_fields(const struct sk_buff *skb,
 216                     unsigned int outside_hdrlen,
 217                     int *protocol,
 218                     struct in6_addr **raddr,
 219                     struct in6_addr **laddr,
 220                     __be16 *rport,
 221                     __be16 *lport)
 222{
 223        struct ipv6hdr *inside_iph, _inside_iph;
 224        struct icmp6hdr *icmph, _icmph;
 225        __be16 *ports, _ports[2];
 226        u8 inside_nexthdr;
 227        __be16 inside_fragoff;
 228        int inside_hdrlen;
 229
 230        icmph = skb_header_pointer(skb, outside_hdrlen,
 231                                   sizeof(_icmph), &_icmph);
 232        if (icmph == NULL)
 233                return 1;
 234
 235        if (icmph->icmp6_type & ICMPV6_INFOMSG_MASK)
 236                return 1;
 237
 238        inside_iph = skb_header_pointer(skb, outside_hdrlen + sizeof(_icmph), sizeof(_inside_iph), &_inside_iph);
 239        if (inside_iph == NULL)
 240                return 1;
 241        inside_nexthdr = inside_iph->nexthdr;
 242
 243        inside_hdrlen = ipv6_skip_exthdr(skb, outside_hdrlen + sizeof(_icmph) + sizeof(_inside_iph),
 244                                         &inside_nexthdr, &inside_fragoff);
 245        if (inside_hdrlen < 0)
 246                return 1; /* hjm: Packet has no/incomplete transport layer headers. */
 247
 248        if (inside_nexthdr != IPPROTO_TCP &&
 249            inside_nexthdr != IPPROTO_UDP)
 250                return 1;
 251
 252        ports = skb_header_pointer(skb, inside_hdrlen,
 253                                   sizeof(_ports), &_ports);
 254        if (ports == NULL)
 255                return 1;
 256
 257        /* the inside IP packet is the one quoted from our side, thus
 258         * its saddr is the local address */
 259        *protocol = inside_nexthdr;
 260        *laddr = &inside_iph->saddr;
 261        *lport = ports[0];
 262        *raddr = &inside_iph->daddr;
 263        *rport = ports[1];
 264
 265        return 0;
 266}
 267
 268static bool
 269socket_mt6_v1_v2(const struct sk_buff *skb, struct xt_action_param *par)
 270{
 271        struct ipv6hdr *iph = ipv6_hdr(skb);
 272        struct udphdr _hdr, *hp = NULL;
 273        struct sock *sk = skb->sk;
 274        struct in6_addr *daddr = NULL, *saddr = NULL;
 275        __be16 uninitialized_var(dport), uninitialized_var(sport);
 276        int thoff = 0, uninitialized_var(tproto);
 277        const struct xt_socket_mtinfo1 *info = (struct xt_socket_mtinfo1 *) par->matchinfo;
 278
 279        tproto = ipv6_find_hdr(skb, &thoff, -1, NULL, NULL);
 280        if (tproto < 0) {
 281                pr_debug("unable to find transport header in IPv6 packet, dropping\n");
 282                return NF_DROP;
 283        }
 284
 285        if (tproto == IPPROTO_UDP || tproto == IPPROTO_TCP) {
 286                hp = skb_header_pointer(skb, thoff,
 287                                        sizeof(_hdr), &_hdr);
 288                if (hp == NULL)
 289                        return false;
 290
 291                saddr = &iph->saddr;
 292                sport = hp->source;
 293                daddr = &iph->daddr;
 294                dport = hp->dest;
 295
 296        } else if (tproto == IPPROTO_ICMPV6) {
 297                if (extract_icmp6_fields(skb, thoff, &tproto, &saddr, &daddr,
 298                                         &sport, &dport))
 299                        return false;
 300        } else {
 301                return false;
 302        }
 303
 304        if (!sk)
 305                sk = nf_tproxy_get_sock_v6(dev_net(skb->dev), tproto,
 306                                           saddr, daddr, sport, dport,
 307                                           par->in, NFT_LOOKUP_ANY);
 308        if (sk) {
 309                bool wildcard;
 310                bool transparent = true;
 311
 312                /* Ignore sockets listening on INADDR_ANY
 313                 * unless XT_SOCKET_NOWILDCARD is set
 314                 */
 315                wildcard = (!(info->flags & XT_SOCKET_NOWILDCARD) &&
 316                            sk->sk_state != TCP_TIME_WAIT &&
 317                            ipv6_addr_any(&inet6_sk(sk)->rcv_saddr));
 318
 319                /* Ignore non-transparent sockets,
 320                   if XT_SOCKET_TRANSPARENT is used */
 321                if (info->flags & XT_SOCKET_TRANSPARENT)
 322                        transparent = ((sk->sk_state != TCP_TIME_WAIT &&
 323                                        inet_sk(sk)->transparent) ||
 324                                       (sk->sk_state == TCP_TIME_WAIT &&
 325                                        inet_twsk(sk)->tw_transparent));
 326
 327                if (sk != skb->sk)
 328                        xt_socket_put_sk(sk);
 329
 330                if (wildcard || !transparent)
 331                        sk = NULL;
 332        }
 333
 334        pr_debug("proto %hhd %pI6:%hu -> %pI6:%hu "
 335                 "(orig %pI6:%hu) sock %p\n",
 336                 tproto, saddr, ntohs(sport),
 337                 daddr, ntohs(dport),
 338                 &iph->daddr, hp ? ntohs(hp->dest) : 0, sk);
 339
 340        return (sk != NULL);
 341}
 342#endif
 343
 344static int socket_mt_v1_check(const struct xt_mtchk_param *par)
 345{
 346        const struct xt_socket_mtinfo1 *info = (struct xt_socket_mtinfo1 *) par->matchinfo;
 347
 348        if (info->flags & ~XT_SOCKET_FLAGS_V1) {
 349                pr_info("unknown flags 0x%x\n", info->flags & ~XT_SOCKET_FLAGS_V1);
 350                return -EINVAL;
 351        }
 352        return 0;
 353}
 354
 355static int socket_mt_v2_check(const struct xt_mtchk_param *par)
 356{
 357        const struct xt_socket_mtinfo2 *info = (struct xt_socket_mtinfo2 *) par->matchinfo;
 358
 359        if (info->flags & ~XT_SOCKET_FLAGS_V2) {
 360                pr_info("unknown flags 0x%x\n", info->flags & ~XT_SOCKET_FLAGS_V2);
 361                return -EINVAL;
 362        }
 363        return 0;
 364}
 365
 366static struct xt_match socket_mt_reg[] __read_mostly = {
 367        {
 368                .name           = "socket",
 369                .revision       = 0,
 370                .family         = NFPROTO_IPV4,
 371                .match          = socket_mt4_v0,
 372                .hooks          = (1 << NF_INET_PRE_ROUTING) |
 373                                  (1 << NF_INET_LOCAL_IN),
 374                .me             = THIS_MODULE,
 375        },
 376        {
 377                .name           = "socket",
 378                .revision       = 1,
 379                .family         = NFPROTO_IPV4,
 380                .match          = socket_mt4_v1_v2,
 381                .checkentry     = socket_mt_v1_check,
 382                .matchsize      = sizeof(struct xt_socket_mtinfo1),
 383                .hooks          = (1 << NF_INET_PRE_ROUTING) |
 384                                  (1 << NF_INET_LOCAL_IN),
 385                .me             = THIS_MODULE,
 386        },
 387#ifdef XT_SOCKET_HAVE_IPV6
 388        {
 389                .name           = "socket",
 390                .revision       = 1,
 391                .family         = NFPROTO_IPV6,
 392                .match          = socket_mt6_v1_v2,
 393                .checkentry     = socket_mt_v1_check,
 394                .matchsize      = sizeof(struct xt_socket_mtinfo1),
 395                .hooks          = (1 << NF_INET_PRE_ROUTING) |
 396                                  (1 << NF_INET_LOCAL_IN),
 397                .me             = THIS_MODULE,
 398        },
 399#endif
 400        {
 401                .name           = "socket",
 402                .revision       = 2,
 403                .family         = NFPROTO_IPV4,
 404                .match          = socket_mt4_v1_v2,
 405                .checkentry     = socket_mt_v2_check,
 406                .matchsize      = sizeof(struct xt_socket_mtinfo1),
 407                .hooks          = (1 << NF_INET_PRE_ROUTING) |
 408                                  (1 << NF_INET_LOCAL_IN),
 409                .me             = THIS_MODULE,
 410        },
 411#ifdef XT_SOCKET_HAVE_IPV6
 412        {
 413                .name           = "socket",
 414                .revision       = 2,
 415                .family         = NFPROTO_IPV6,
 416                .match          = socket_mt6_v1_v2,
 417                .checkentry     = socket_mt_v2_check,
 418                .matchsize      = sizeof(struct xt_socket_mtinfo1),
 419                .hooks          = (1 << NF_INET_PRE_ROUTING) |
 420                                  (1 << NF_INET_LOCAL_IN),
 421                .me             = THIS_MODULE,
 422        },
 423#endif
 424};
 425
 426static int __init socket_mt_init(void)
 427{
 428        nf_defrag_ipv4_enable();
 429#ifdef XT_SOCKET_HAVE_IPV6
 430        nf_defrag_ipv6_enable();
 431#endif
 432
 433        return xt_register_matches(socket_mt_reg, ARRAY_SIZE(socket_mt_reg));
 434}
 435
 436static void __exit socket_mt_exit(void)
 437{
 438        xt_unregister_matches(socket_mt_reg, ARRAY_SIZE(socket_mt_reg));
 439}
 440
 441module_init(socket_mt_init);
 442module_exit(socket_mt_exit);
 443
 444MODULE_LICENSE("GPL");
 445MODULE_AUTHOR("Krisztian Kovacs, Balazs Scheidler");
 446MODULE_DESCRIPTION("x_tables socket match module");
 447MODULE_ALIAS("ipt_socket");
 448MODULE_ALIAS("ip6t_socket");
 449
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