net/netfilter/xt_socket.c

   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
  38 void
  39 xt_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 EXPORT_SYMBOL(xt_socket_put_sk);
  47
  48 static int
  49 extract_icmp4_fields(const struct sk_buff *skb,
  50                     u8 *protocol,
  51                     __be32 *raddr,
  52                     __be32 *laddr,
  53                     __be16 *rport,
  54                     __be16 *lport)
  55 {
  56         unsigned int outside_hdrlen = ip_hdrlen(skb);
  57         struct iphdr *inside_iph, _inside_iph;
  58         struct icmphdr *icmph, _icmph;
  59         __be16 *ports, _ports[2];
  60
  61         icmph = skb_header_pointer(skb, outside_hdrlen,
  62                                    sizeof(_icmph), &_icmph);
  63         if (icmph == NULL)
  64                 return 1;
  65
  66         switch (icmph->type) {
  67         case ICMP_DEST_UNREACH:
  68         case ICMP_SOURCE_QUENCH:
  69         case ICMP_REDIRECT:
  70         case ICMP_TIME_EXCEEDED:
  71         case ICMP_PARAMETERPROB:
  72                 break;
  73         default:
  74                 return 1;
  75         }
  76
  77         inside_iph = skb_header_pointer(skb, outside_hdrlen +
  78                                         sizeof(struct icmphdr),
  79                                         sizeof(_inside_iph), &_inside_iph);
  80         if (inside_iph == NULL)
  81                 return 1;
  82
  83         if (inside_iph->protocol != IPPROTO_TCP &&
  84             inside_iph->protocol != IPPROTO_UDP)
  85                 return 1;
  86
  87         ports = skb_header_pointer(skb, outside_hdrlen +
  88                                    sizeof(struct icmphdr) +
  89                                    (inside_iph->ihl << 2),
  90                                    sizeof(_ports), &_ports);
  91         if (ports == NULL)
  92                 return 1;
  93
  94         /* the inside IP packet is the one quoted from our side, thus
  95          * its saddr is the local address */
  96         *protocol = inside_iph->protocol;
  97         *laddr = inside_iph->saddr;
  98         *lport = ports[0];
  99         *raddr = inside_iph->daddr;
 100         *rport = ports[1];
 101
 102         return 0;
 103 }
 104
 105 struct sock*
 106 xt_socket_get4_sk(const struct sk_buff *skb, struct xt_action_param *par)
 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 NULL;
 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 NULL;
 135         } else {
 136                 return NULL;
 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
 161         pr_debug("proto %hhu %pI4:%hu -> %pI4:%hu (orig %pI4:%hu) sock %p\n",
 162                  protocol, &saddr, ntohs(sport),
 163                  &daddr, ntohs(dport),
 164                  &iph->daddr, hp ? ntohs(hp->dest) : 0, sk);
 165
 166         return sk;
 167 }
 168 EXPORT_SYMBOL(xt_socket_get4_sk);
 169
 170 static bool
 171 socket_match(const struct sk_buff *skb, struct xt_action_param *par,
 172              const struct xt_socket_mtinfo1 *info)
 173 {
 174         struct sock *sk;
 175
 176         sk = xt_socket_get4_sk(skb, par);
 177         if (sk != NULL) {
 178                 bool wildcard;
 179                 bool transparent = true;
 180
 181                 /* Ignore sockets listening on INADDR_ANY */
 182                 wildcard = (sk->sk_state != TCP_TIME_WAIT &&
 183                             inet_sk(sk)->inet_rcv_saddr == 0);
 184
 185                 /* Ignore non-transparent sockets,
 186                    if XT_SOCKET_TRANSPARENT is used */
 187                 if (info && info->flags & XT_SOCKET_TRANSPARENT)
 188                         transparent = ((sk->sk_state != TCP_TIME_WAIT &&
 189                                         inet_sk(sk)->transparent) ||
 190                                        (sk->sk_state == TCP_TIME_WAIT &&
 191                                         inet_twsk(sk)->tw_transparent));
 192
 193                 xt_socket_put_sk(sk);
 194
 195                 if (wildcard || !transparent)
 196                         sk = NULL;
 197         }
 198
 199         return (sk != NULL);
 200 }
 201
 202 static bool
 203 socket_mt4_v0(const struct sk_buff *skb, struct xt_action_param *par)
 204 {
 205         return socket_match(skb, par, NULL);
 206 }
 207
 208 static bool
 209 socket_mt4_v1(const struct sk_buff *skb, struct xt_action_param *par)
 210 {
 211         return socket_match(skb, par, par->matchinfo);
 212 }
 213
 214 #ifdef XT_SOCKET_HAVE_IPV6
 215
 216 static int
 217 extract_icmp6_fields(const struct sk_buff *skb,
 218                      unsigned int outside_hdrlen,
 219                      int *protocol,
 220                      struct in6_addr **raddr,
 221                      struct in6_addr **laddr,
 222                      __be16 *rport,
 223                      __be16 *lport)
 224 {
 225         struct ipv6hdr *inside_iph, _inside_iph;
 226         struct icmp6hdr *icmph, _icmph;
 227         __be16 *ports, _ports[2];
 228         u8 inside_nexthdr;
 229         __be16 inside_fragoff;
 230         int inside_hdrlen;
 231
 232         icmph = skb_header_pointer(skb, outside_hdrlen,
 233                                    sizeof(_icmph), &_icmph);
 234         if (icmph == NULL)
 235                 return 1;
 236
 237         if (icmph->icmp6_type & ICMPV6_INFOMSG_MASK)
 238                 return 1;
 239
 240         inside_iph = skb_header_pointer(skb, outside_hdrlen + sizeof(_icmph), sizeof(_inside_iph), &_inside_iph);
 241         if (inside_iph == NULL)
 242                 return 1;
 243         inside_nexthdr = inside_iph->nexthdr;
 244
 245         inside_hdrlen = ipv6_skip_exthdr(skb, outside_hdrlen + sizeof(_icmph) + sizeof(_inside_iph),
 246                                          &inside_nexthdr, &inside_fragoff);
 247         if (inside_hdrlen < 0)
 248                 return 1; /* hjm: Packet has no/incomplete transport layer headers. */
 249
 250         if (inside_nexthdr != IPPROTO_TCP &&
 251             inside_nexthdr != IPPROTO_UDP)
 252                 return 1;
 253
 254         ports = skb_header_pointer(skb, inside_hdrlen,
 255                                    sizeof(_ports), &_ports);
 256         if (ports == NULL)
 257                 return 1;
 258
 259         /* the inside IP packet is the one quoted from our side, thus
 260          * its saddr is the local address */
 261         *protocol = inside_nexthdr;
 262         *laddr = &inside_iph->saddr;
 263         *lport = ports[0];
 264         *raddr = &inside_iph->daddr;
 265         *rport = ports[1];
 266
 267         return 0;
 268 }
 269
 270 struct sock*
 271 xt_socket_get6_sk(const struct sk_buff *skb, struct xt_action_param *par)
 272 {
 273         struct ipv6hdr *iph = ipv6_hdr(skb);
 274         struct udphdr _hdr, *hp = NULL;
 275         struct sock *sk;
 276         struct in6_addr *daddr = NULL, *saddr = NULL;
 277         __be16 uninitialized_var(dport), uninitialized_var(sport);
 278         int thoff = 0, uninitialized_var(tproto);
 279
 280         tproto = ipv6_find_hdr(skb, &thoff, -1, NULL, NULL);
 281         if (tproto < 0) {
 282                 pr_debug("unable to find transport header in IPv6 packet, dropping\n");
 283                 return NF_DROP;
 284         }
 285
 286         if (tproto == IPPROTO_UDP || tproto == IPPROTO_TCP) {
 287                 hp = skb_header_pointer(skb, thoff,
 288                                         sizeof(_hdr), &_hdr);
 289                 if (hp == NULL)
 290                         return NULL;
 291
 292                 saddr = &iph->saddr;
 293                 sport = hp->source;
 294                 daddr = &iph->daddr;
 295                 dport = hp->dest;
 296
 297         } else if (tproto == IPPROTO_ICMPV6) {
 298                 if (extract_icmp6_fields(skb, thoff, &tproto, &saddr, &daddr,
 299                                          &sport, &dport))
 300                         return NULL;
 301         } else {
 302                 return NULL;
 303         }
 304
 305         sk = nf_tproxy_get_sock_v6(dev_net(skb->dev), tproto,
 306                                    saddr, daddr, sport, dport, par->in, NFT_LOOKUP_ANY);
 307         pr_debug("proto %hhd %pI6:%hu -> %pI6:%hu "
 308                  "(orig %pI6:%hu) sock %p\n",
 309                  tproto, saddr, ntohs(sport),
 310                  daddr, ntohs(dport),
 311                  &iph->daddr, hp ? ntohs(hp->dest) : 0, sk);
 312         return sk;
 313 }
 314 EXPORT_SYMBOL(xt_socket_get6_sk);
 315
 316 static bool
 317 socket_mt6_v1(const struct sk_buff *skb, struct xt_action_param *par)
 318 {
 319         struct sock *sk;
 320         const struct xt_socket_mtinfo1 *info;
 321
 322         info = (struct xt_socket_mtinfo1 *) par->matchinfo;
 323         sk = xt_socket_get6_sk(skb, par);
 324         if (sk != NULL) {
 325                 bool wildcard;
 326                 bool transparent = true;
 327
 328                 /* Ignore sockets listening on INADDR_ANY */
 329                 wildcard = (sk->sk_state != TCP_TIME_WAIT &&
 330                             ipv6_addr_any(&inet6_sk(sk)->rcv_saddr));
 331
 332                 /* Ignore non-transparent sockets,
 333                    if XT_SOCKET_TRANSPARENT is used */
 334                 if (info && info->flags & XT_SOCKET_TRANSPARENT)
 335                         transparent = ((sk->sk_state != TCP_TIME_WAIT &&
 336                                         inet_sk(sk)->transparent) ||
 337                                        (sk->sk_state == TCP_TIME_WAIT &&
 338                                         inet_twsk(sk)->tw_transparent));
 339
 340                 xt_socket_put_sk(sk);
 341
 342                 if (wildcard || !transparent)
 343                         sk = NULL;
 344         }
 345
 346         return (sk != NULL);
 347 }
 348 #endif
 349
 350 static struct xt_match socket_mt_reg[] __read_mostly = {
 351         {
 352                 .name           = "socket",
 353                 .revision       = 0,
 354                 .family         = NFPROTO_IPV4,
 355                 .match          = socket_mt4_v0,
 356                 .hooks          = (1 << NF_INET_PRE_ROUTING) |
 357                                   (1 << NF_INET_LOCAL_IN),
 358                 .me             = THIS_MODULE,
 359         },
 360         {
 361                 .name           = "socket",
 362                 .revision       = 1,
 363                 .family         = NFPROTO_IPV4,
 364                 .match          = socket_mt4_v1,
 365                 .matchsize      = sizeof(struct xt_socket_mtinfo1),
 366                 .hooks          = (1 << NF_INET_PRE_ROUTING) |
 367                                   (1 << NF_INET_LOCAL_IN),
 368                 .me             = THIS_MODULE,
 369         },
 370 #ifdef XT_SOCKET_HAVE_IPV6
 371         {
 372                 .name           = "socket",
 373                 .revision       = 1,
 374                 .family         = NFPROTO_IPV6,
 375                 .match          = socket_mt6_v1,
 376                 .matchsize      = sizeof(struct xt_socket_mtinfo1),
 377                 .hooks          = (1 << NF_INET_PRE_ROUTING) |
 378                                   (1 << NF_INET_LOCAL_IN),
 379                 .me             = THIS_MODULE,
 380         },
 381 #endif
 382 };
 383
 384 static int __init socket_mt_init(void)
 385 {
 386         nf_defrag_ipv4_enable();
 387 #ifdef XT_SOCKET_HAVE_IPV6
 388         nf_defrag_ipv6_enable();
 389 #endif
 390
 391         return xt_register_matches(socket_mt_reg, ARRAY_SIZE(socket_mt_reg));
 392 }
 393
 394 static void __exit socket_mt_exit(void)
 395 {
 396         xt_unregister_matches(socket_mt_reg, ARRAY_SIZE(socket_mt_reg));
 397 }
 398
 399 module_init(socket_mt_init);
 400 module_exit(socket_mt_exit);
 401
 402 MODULE_LICENSE("GPL");
 403 MODULE_AUTHOR("Krisztian Kovacs, Balazs Scheidler");
 404 MODULE_DESCRIPTION("x_tables socket match module");
 405 MODULE_ALIAS("ipt_socket");
 406 MODULE_ALIAS("ip6t_socket");