net/netfilter/xt_TPROXY.c

   1 /*
   2  * Transparent proxy support for Linux/iptables
   3  *
   4  * Copyright (c) 2006-2010 BalaBit IT Ltd.
   5  * Author: Balazs Scheidler, 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/ip.h>
  16 #include <net/checksum.h>
  17 #include <net/udp.h>
  18 #include <net/tcp.h>
  19 #include <net/inet_sock.h>
  20 #include <net/inet_hashtables.h>
  21 #include <linux/inetdevice.h>
  22 #include <linux/netfilter/x_tables.h>
  23 #include <linux/netfilter_ipv4/ip_tables.h>
  24
  25 #include <net/netfilter/ipv4/nf_defrag_ipv4.h>
  26
  27 #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
  28 #define XT_TPROXY_HAVE_IPV6 1
  29 #include <net/if_inet6.h>
  30 #include <net/addrconf.h>
  31 #include <net/inet6_hashtables.h>
  32 #include <linux/netfilter_ipv6/ip6_tables.h>
  33 #include <net/netfilter/ipv6/nf_defrag_ipv6.h>
  34 #endif
  35
  36 #include <net/netfilter/nf_tproxy.h>
  37 #include <linux/netfilter/xt_TPROXY.h>
  38
  39 static unsigned int
  40 tproxy_tg4(struct net *net, struct sk_buff *skb, __be32 laddr, __be16 lport,
  41            u_int32_t mark_mask, u_int32_t mark_value)
  42 {
  43         const struct iphdr *iph = ip_hdr(skb);
  44         struct udphdr _hdr, *hp;
  45         struct sock *sk;
  46
  47         hp = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(_hdr), &_hdr);
  48         if (hp == NULL)
  49                 return NF_DROP;
  50
  51         /* check if there's an ongoing connection on the packet
  52          * addresses, this happens if the redirect already happened
  53          * and the current packet belongs to an already established
  54          * connection */
  55         sk = nf_tproxy_get_sock_v4(net, skb, iph->protocol,
  56                                    iph->saddr, iph->daddr,
  57                                    hp->source, hp->dest,
  58                                    skb->dev, NF_TPROXY_LOOKUP_ESTABLISHED);
  59
  60         laddr = nf_tproxy_laddr4(skb, laddr, iph->daddr);
  61         if (!lport)
  62                 lport = hp->dest;
  63
  64         /* UDP has no TCP_TIME_WAIT state, so we never enter here */
  65         if (sk && sk->sk_state == TCP_TIME_WAIT)
  66                 /* reopening a TIME_WAIT connection needs special handling */
  67                 sk = nf_tproxy_handle_time_wait4(net, skb, laddr, lport, sk);
  68         else if (!sk)
  69                 /* no, there's no established connection, check if
  70                  * there's a listener on the redirected addr/port */
  71                 sk = nf_tproxy_get_sock_v4(net, skb, iph->protocol,
  72                                            iph->saddr, laddr,
  73                                            hp->source, lport,
  74                                            skb->dev, NF_TPROXY_LOOKUP_LISTENER);
  75
  76         /* NOTE: assign_sock consumes our sk reference */
  77         if (sk && nf_tproxy_sk_is_transparent(sk)) {
  78                 /* This should be in a separate target, but we don't do multiple
  79                    targets on the same rule yet */
  80                 skb->mark = (skb->mark & ~mark_mask) ^ mark_value;
  81
  82                 pr_debug("redirecting: proto %hhu %pI4:%hu -> %pI4:%hu, mark: %x\n",
  83                          iph->protocol, &iph->daddr, ntohs(hp->dest),
  84                          &laddr, ntohs(lport), skb->mark);
  85
  86                 nf_tproxy_assign_sock(skb, sk);
  87                 return NF_ACCEPT;
  88         }
  89
  90         pr_debug("no socket, dropping: proto %hhu %pI4:%hu -> %pI4:%hu, mark: %x\n",
  91                  iph->protocol, &iph->saddr, ntohs(hp->source),
  92                  &iph->daddr, ntohs(hp->dest), skb->mark);
  93         return NF_DROP;
  94 }
  95
  96 static unsigned int
  97 tproxy_tg4_v0(struct sk_buff *skb, const struct xt_action_param *par)
  98 {
  99         const struct xt_tproxy_target_info *tgi = par->targinfo;
 100
 101         return tproxy_tg4(xt_net(par), skb, tgi->laddr, tgi->lport,
 102                           tgi->mark_mask, tgi->mark_value);
 103 }
 104
 105 static unsigned int
 106 tproxy_tg4_v1(struct sk_buff *skb, const struct xt_action_param *par)
 107 {
 108         const struct xt_tproxy_target_info_v1 *tgi = par->targinfo;
 109
 110         return tproxy_tg4(xt_net(par), skb, tgi->laddr.ip, tgi->lport,
 111                           tgi->mark_mask, tgi->mark_value);
 112 }
 113
 114 #ifdef XT_TPROXY_HAVE_IPV6
 115
 116 static unsigned int
 117 tproxy_tg6_v1(struct sk_buff *skb, const struct xt_action_param *par)
 118 {
 119         const struct ipv6hdr *iph = ipv6_hdr(skb);
 120         const struct xt_tproxy_target_info_v1 *tgi = par->targinfo;
 121         struct udphdr _hdr, *hp;
 122         struct sock *sk;
 123         const struct in6_addr *laddr;
 124         __be16 lport;
 125         int thoff = 0;
 126         int tproto;
 127
 128         tproto = ipv6_find_hdr(skb, &thoff, -1, NULL, NULL);
 129         if (tproto < 0) {
 130                 pr_debug("unable to find transport header in IPv6 packet, dropping\n");
 131                 return NF_DROP;
 132         }
 133
 134         hp = skb_header_pointer(skb, thoff, sizeof(_hdr), &_hdr);
 135         if (hp == NULL) {
 136                 pr_debug("unable to grab transport header contents in IPv6 packet, dropping\n");
 137                 return NF_DROP;
 138         }
 139
 140         /* check if there's an ongoing connection on the packet
 141          * addresses, this happens if the redirect already happened
 142          * and the current packet belongs to an already established
 143          * connection */
 144         sk = nf_tproxy_get_sock_v6(xt_net(par), skb, thoff, tproto,
 145                                    &iph->saddr, &iph->daddr,
 146                                    hp->source, hp->dest,
 147                                    xt_in(par), NF_TPROXY_LOOKUP_ESTABLISHED);
 148
 149         laddr = nf_tproxy_laddr6(skb, &tgi->laddr.in6, &iph->daddr);
 150         lport = tgi->lport ? tgi->lport : hp->dest;
 151
 152         /* UDP has no TCP_TIME_WAIT state, so we never enter here */
 153         if (sk && sk->sk_state == TCP_TIME_WAIT) {
 154                 const struct xt_tproxy_target_info_v1 *tgi = par->targinfo;
 155                 /* reopening a TIME_WAIT connection needs special handling */
 156                 sk = nf_tproxy_handle_time_wait6(skb, tproto, thoff,
 157                                               xt_net(par),
 158                                               &tgi->laddr.in6,
 159                                               tgi->lport,
 160                                               sk);
 161         }
 162         else if (!sk)
 163                 /* no there's no established connection, check if
 164                  * there's a listener on the redirected addr/port */
 165                 sk = nf_tproxy_get_sock_v6(xt_net(par), skb, thoff,
 166                                            tproto, &iph->saddr, laddr,
 167                                            hp->source, lport,
 168                                            xt_in(par), NF_TPROXY_LOOKUP_LISTENER);
 169
 170         /* NOTE: assign_sock consumes our sk reference */
 171         if (sk && nf_tproxy_sk_is_transparent(sk)) {
 172                 /* This should be in a separate target, but we don't do multiple
 173                    targets on the same rule yet */
 174                 skb->mark = (skb->mark & ~tgi->mark_mask) ^ tgi->mark_value;
 175
 176                 pr_debug("redirecting: proto %hhu %pI6:%hu -> %pI6:%hu, mark: %x\n",
 177                          tproto, &iph->saddr, ntohs(hp->source),
 178                          laddr, ntohs(lport), skb->mark);
 179
 180                 nf_tproxy_assign_sock(skb, sk);
 181                 return NF_ACCEPT;
 182         }
 183
 184         pr_debug("no socket, dropping: proto %hhu %pI6:%hu -> %pI6:%hu, mark: %x\n",
 185                  tproto, &iph->saddr, ntohs(hp->source),
 186                  &iph->daddr, ntohs(hp->dest), skb->mark);
 187
 188         return NF_DROP;
 189 }
 190
 191 static int tproxy_tg6_check(const struct xt_tgchk_param *par)
 192 {
 193         const struct ip6t_ip6 *i = par->entryinfo;
 194         int err;
 195
 196         err = nf_defrag_ipv6_enable(par->net);
 197         if (err)
 198                 return err;
 199
 200         if ((i->proto == IPPROTO_TCP || i->proto == IPPROTO_UDP) &&
 201             !(i->invflags & IP6T_INV_PROTO))
 202                 return 0;
 203
 204         pr_info_ratelimited("Can be used only with -p tcp or -p udp\n");
 205         return -EINVAL;
 206 }
 207 #endif
 208
 209 static int tproxy_tg4_check(const struct xt_tgchk_param *par)
 210 {
 211         const struct ipt_ip *i = par->entryinfo;
 212         int err;
 213
 214         err = nf_defrag_ipv4_enable(par->net);
 215         if (err)
 216                 return err;
 217
 218         if ((i->proto == IPPROTO_TCP || i->proto == IPPROTO_UDP)
 219             && !(i->invflags & IPT_INV_PROTO))
 220                 return 0;
 221
 222         pr_info_ratelimited("Can be used only with -p tcp or -p udp\n");
 223         return -EINVAL;
 224 }
 225
 226 static struct xt_target tproxy_tg_reg[] __read_mostly = {
 227         {
 228                 .name           = "TPROXY",
 229                 .family         = NFPROTO_IPV4,
 230                 .table          = "mangle",
 231                 .target         = tproxy_tg4_v0,
 232                 .revision       = 0,
 233                 .targetsize     = sizeof(struct xt_tproxy_target_info),
 234                 .checkentry     = tproxy_tg4_check,
 235                 .hooks          = 1 << NF_INET_PRE_ROUTING,
 236                 .me             = THIS_MODULE,
 237         },
 238         {
 239                 .name           = "TPROXY",
 240                 .family         = NFPROTO_IPV4,
 241                 .table          = "mangle",
 242                 .target         = tproxy_tg4_v1,
 243                 .revision       = 1,
 244                 .targetsize     = sizeof(struct xt_tproxy_target_info_v1),
 245                 .checkentry     = tproxy_tg4_check,
 246                 .hooks          = 1 << NF_INET_PRE_ROUTING,
 247                 .me             = THIS_MODULE,
 248         },
 249 #ifdef XT_TPROXY_HAVE_IPV6
 250         {
 251                 .name           = "TPROXY",
 252                 .family         = NFPROTO_IPV6,
 253                 .table          = "mangle",
 254                 .target         = tproxy_tg6_v1,
 255                 .revision       = 1,
 256                 .targetsize     = sizeof(struct xt_tproxy_target_info_v1),
 257                 .checkentry     = tproxy_tg6_check,
 258                 .hooks          = 1 << NF_INET_PRE_ROUTING,
 259                 .me             = THIS_MODULE,
 260         },
 261 #endif
 262
 263 };
 264
 265 static int __init tproxy_tg_init(void)
 266 {
 267         return xt_register_targets(tproxy_tg_reg, ARRAY_SIZE(tproxy_tg_reg));
 268 }
 269
 270 static void __exit tproxy_tg_exit(void)
 271 {
 272         xt_unregister_targets(tproxy_tg_reg, ARRAY_SIZE(tproxy_tg_reg));
 273 }
 274
 275 module_init(tproxy_tg_init);
 276 module_exit(tproxy_tg_exit);
 277 MODULE_LICENSE("GPL");
 278 MODULE_AUTHOR("Balazs Scheidler, Krisztian Kovacs");
 279 MODULE_DESCRIPTION("Netfilter transparent proxy (TPROXY) target module.");
 280 MODULE_ALIAS("ipt_TPROXY");
 281 MODULE_ALIAS("ip6t_TPROXY");