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 static 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
  47 static int
  48 extract_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
 104 static bool
 105 socket_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 daddr, saddr;
 112         __be16 dport, sport;
 113         u8 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
 190 static bool
 191 socket_mt4_v0(const struct sk_buff *skb, struct xt_action_param *par)
 192 {
 193         return socket_match(skb, par, NULL);
 194 }
 195
 196 static bool
 197 socket_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
 204 static int
 205 extract_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
 258 static bool
 259 socket_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, *saddr;
 265         __be16 dport, sport;
 266         int thoff, tproto;
 267         const struct xt_socket_mtinfo1 *info = (struct xt_socket_mtinfo1 *) par->matchinfo;
 268
 269         tproto = ipv6_find_hdr(skb, &thoff, -1, 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
 328 static 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
 362 static 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
 372 static void __exit socket_mt_exit(void)
 373 {
 374         xt_unregister_matches(socket_mt_reg, ARRAY_SIZE(socket_mt_reg));
 375 }
 376
 377 module_init(socket_mt_init);
 378 module_exit(socket_mt_exit);
 379
 380 MODULE_LICENSE("GPL");
 381 MODULE_AUTHOR("Krisztian Kovacs, Balazs Scheidler");
 382 MODULE_DESCRIPTION("x_tables socket match module");
 383 MODULE_ALIAS("ipt_socket");
 384 MODULE_ALIAS("ip6t_socket");