net/netfilter/xt_TPROXY.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Transparent proxy support for Linux/iptables
   4  *
   5  * Copyright (c) 2006-2010 BalaBit IT Ltd.
   6  * Author: Balazs Scheidler, Krisztian Kovacs
   7  */
   8 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
   9 #include <linux/module.h>
  10 #include <linux/skbuff.h>
  11 #include <linux/ip.h>
  12 #include <net/checksum.h>
  13 #include <net/udp.h>
  14 #include <net/tcp.h>
  15 #include <net/inet_sock.h>
  16 #include <net/inet_hashtables.h>
  17 #include <linux/inetdevice.h>
  18 #include <linux/netfilter/x_tables.h>
  19 #include <linux/netfilter_ipv4/ip_tables.h>
  20
  21 #include <net/netfilter/ipv4/nf_defrag_ipv4.h>
  22
  23 #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
  24 #define XT_TPROXY_HAVE_IPV6 1
  25 #include <net/if_inet6.h>
  26 #include <net/addrconf.h>
  27 #include <net/inet6_hashtables.h>
  28 #include <linux/netfilter_ipv6/ip6_tables.h>
  29 #include <net/netfilter/ipv6/nf_defrag_ipv6.h>
  30 #endif
  31
  32 #include <net/netfilter/nf_tproxy.h>
  33 #include <linux/netfilter/xt_TPROXY.h>
  34
  35 static unsigned int
  36 tproxy_tg4(struct net *net, struct sk_buff *skb, __be32 laddr, __be16 lport,
  37            u_int32_t mark_mask, u_int32_t mark_value)
  38 {
  39         const struct iphdr *iph = ip_hdr(skb);
  40         struct udphdr _hdr, *hp;
  41         struct sock *sk;
  42
  43         hp = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(_hdr), &_hdr);
  44         if (hp == NULL)
  45                 return NF_DROP;
  46
  47         /* check if there's an ongoing connection on the packet
  48          * addresses, this happens if the redirect already happened
  49          * and the current packet belongs to an already established
  50          * connection */
  51         sk = nf_tproxy_get_sock_v4(net, skb, iph->protocol,
  52                                    iph->saddr, iph->daddr,
  53                                    hp->source, hp->dest,
  54                                    skb->dev, NF_TPROXY_LOOKUP_ESTABLISHED);
  55
  56         laddr = nf_tproxy_laddr4(skb, laddr, iph->daddr);
  57         if (!lport)
  58                 lport = hp->dest;
  59
  60         /* UDP has no TCP_TIME_WAIT state, so we never enter here */
  61         if (sk && sk->sk_state == TCP_TIME_WAIT)
  62                 /* reopening a TIME_WAIT connection needs special handling */
  63                 sk = nf_tproxy_handle_time_wait4(net, skb, laddr, lport, sk);
  64         else if (!sk)
  65                 /* no, there's no established connection, check if
  66                  * there's a listener on the redirected addr/port */
  67                 sk = nf_tproxy_get_sock_v4(net, skb, iph->protocol,
  68                                            iph->saddr, laddr,
  69                                            hp->source, lport,
  70                                            skb->dev, NF_TPROXY_LOOKUP_LISTENER);
  71
  72         /* NOTE: assign_sock consumes our sk reference */
  73         if (sk && nf_tproxy_sk_is_transparent(sk)) {
  74                 /* This should be in a separate target, but we don't do multiple
  75                    targets on the same rule yet */
  76                 skb->mark = (skb->mark & ~mark_mask) ^ mark_value;
  77                 nf_tproxy_assign_sock(skb, sk);
  78                 return NF_ACCEPT;
  79         }
  80
  81         return NF_DROP;
  82 }
  83
  84 static unsigned int
  85 tproxy_tg4_v0(struct sk_buff *skb, const struct xt_action_param *par)
  86 {
  87         const struct xt_tproxy_target_info *tgi = par->targinfo;
  88
  89         return tproxy_tg4(xt_net(par), skb, tgi->laddr, tgi->lport,
  90                           tgi->mark_mask, tgi->mark_value);
  91 }
  92
  93 static unsigned int
  94 tproxy_tg4_v1(struct sk_buff *skb, const struct xt_action_param *par)
  95 {
  96         const struct xt_tproxy_target_info_v1 *tgi = par->targinfo;
  97
  98         return tproxy_tg4(xt_net(par), skb, tgi->laddr.ip, tgi->lport,
  99                           tgi->mark_mask, tgi->mark_value);
 100 }
 101
 102 #ifdef XT_TPROXY_HAVE_IPV6
 103
 104 static unsigned int
 105 tproxy_tg6_v1(struct sk_buff *skb, const struct xt_action_param *par)
 106 {
 107         const struct ipv6hdr *iph = ipv6_hdr(skb);
 108         const struct xt_tproxy_target_info_v1 *tgi = par->targinfo;
 109         struct udphdr _hdr, *hp;
 110         struct sock *sk;
 111         const struct in6_addr *laddr;
 112         __be16 lport;
 113         int thoff = 0;
 114         int tproto;
 115
 116         tproto = ipv6_find_hdr(skb, &thoff, -1, NULL, NULL);
 117         if (tproto < 0)
 118                 return NF_DROP;
 119
 120         hp = skb_header_pointer(skb, thoff, sizeof(_hdr), &_hdr);
 121         if (!hp)
 122                 return NF_DROP;
 123
 124         /* check if there's an ongoing connection on the packet
 125          * addresses, this happens if the redirect already happened
 126          * and the current packet belongs to an already established
 127          * connection */
 128         sk = nf_tproxy_get_sock_v6(xt_net(par), skb, thoff, tproto,
 129                                    &iph->saddr, &iph->daddr,
 130                                    hp->source, hp->dest,
 131                                    xt_in(par), NF_TPROXY_LOOKUP_ESTABLISHED);
 132
 133         laddr = nf_tproxy_laddr6(skb, &tgi->laddr.in6, &iph->daddr);
 134         lport = tgi->lport ? tgi->lport : hp->dest;
 135
 136         /* UDP has no TCP_TIME_WAIT state, so we never enter here */
 137         if (sk && sk->sk_state == TCP_TIME_WAIT) {
 138                 const struct xt_tproxy_target_info_v1 *tgi = par->targinfo;
 139                 /* reopening a TIME_WAIT connection needs special handling */
 140                 sk = nf_tproxy_handle_time_wait6(skb, tproto, thoff,
 141                                               xt_net(par),
 142                                               &tgi->laddr.in6,
 143                                               tgi->lport,
 144                                               sk);
 145         }
 146         else if (!sk)
 147                 /* no there's no established connection, check if
 148                  * there's a listener on the redirected addr/port */
 149                 sk = nf_tproxy_get_sock_v6(xt_net(par), skb, thoff,
 150                                            tproto, &iph->saddr, laddr,
 151                                            hp->source, lport,
 152                                            xt_in(par), NF_TPROXY_LOOKUP_LISTENER);
 153
 154         /* NOTE: assign_sock consumes our sk reference */
 155         if (sk && nf_tproxy_sk_is_transparent(sk)) {
 156                 /* This should be in a separate target, but we don't do multiple
 157                    targets on the same rule yet */
 158                 skb->mark = (skb->mark & ~tgi->mark_mask) ^ tgi->mark_value;
 159                 nf_tproxy_assign_sock(skb, sk);
 160                 return NF_ACCEPT;
 161         }
 162
 163         return NF_DROP;
 164 }
 165
 166 static int tproxy_tg6_check(const struct xt_tgchk_param *par)
 167 {
 168         const struct ip6t_ip6 *i = par->entryinfo;
 169         int err;
 170
 171         err = nf_defrag_ipv6_enable(par->net);
 172         if (err)
 173                 return err;
 174
 175         if ((i->proto == IPPROTO_TCP || i->proto == IPPROTO_UDP) &&
 176             !(i->invflags & IP6T_INV_PROTO))
 177                 return 0;
 178
 179         pr_info_ratelimited("Can be used only with -p tcp or -p udp\n");
 180         return -EINVAL;
 181 }
 182
 183 static void tproxy_tg6_destroy(const struct xt_tgdtor_param *par)
 184 {
 185         nf_defrag_ipv6_disable(par->net);
 186 }
 187 #endif
 188
 189 static int tproxy_tg4_check(const struct xt_tgchk_param *par)
 190 {
 191         const struct ipt_ip *i = par->entryinfo;
 192         int err;
 193
 194         err = nf_defrag_ipv4_enable(par->net);
 195         if (err)
 196                 return err;
 197
 198         if ((i->proto == IPPROTO_TCP || i->proto == IPPROTO_UDP)
 199             && !(i->invflags & IPT_INV_PROTO))
 200                 return 0;
 201
 202         pr_info_ratelimited("Can be used only with -p tcp or -p udp\n");
 203         return -EINVAL;
 204 }
 205
 206 static void tproxy_tg4_destroy(const struct xt_tgdtor_param *par)
 207 {
 208         nf_defrag_ipv4_disable(par->net);
 209 }
 210
 211 static struct xt_target tproxy_tg_reg[] __read_mostly = {
 212         {
 213                 .name           = "TPROXY",
 214                 .family         = NFPROTO_IPV4,
 215                 .table          = "mangle",
 216                 .target         = tproxy_tg4_v0,
 217                 .revision       = 0,
 218                 .targetsize     = sizeof(struct xt_tproxy_target_info),
 219                 .checkentry     = tproxy_tg4_check,
 220                 .destroy        = tproxy_tg4_destroy,
 221                 .hooks          = 1 << NF_INET_PRE_ROUTING,
 222                 .me             = THIS_MODULE,
 223         },
 224         {
 225                 .name           = "TPROXY",
 226                 .family         = NFPROTO_IPV4,
 227                 .table          = "mangle",
 228                 .target         = tproxy_tg4_v1,
 229                 .revision       = 1,
 230                 .targetsize     = sizeof(struct xt_tproxy_target_info_v1),
 231                 .checkentry     = tproxy_tg4_check,
 232                 .destroy        = tproxy_tg4_destroy,
 233                 .hooks          = 1 << NF_INET_PRE_ROUTING,
 234                 .me             = THIS_MODULE,
 235         },
 236 #ifdef XT_TPROXY_HAVE_IPV6
 237         {
 238                 .name           = "TPROXY",
 239                 .family         = NFPROTO_IPV6,
 240                 .table          = "mangle",
 241                 .target         = tproxy_tg6_v1,
 242                 .revision       = 1,
 243                 .targetsize     = sizeof(struct xt_tproxy_target_info_v1),
 244                 .checkentry     = tproxy_tg6_check,
 245                 .destroy        = tproxy_tg6_destroy,
 246                 .hooks          = 1 << NF_INET_PRE_ROUTING,
 247                 .me             = THIS_MODULE,
 248         },
 249 #endif
 250
 251 };
 252
 253 static int __init tproxy_tg_init(void)
 254 {
 255         return xt_register_targets(tproxy_tg_reg, ARRAY_SIZE(tproxy_tg_reg));
 256 }
 257
 258 static void __exit tproxy_tg_exit(void)
 259 {
 260         xt_unregister_targets(tproxy_tg_reg, ARRAY_SIZE(tproxy_tg_reg));
 261 }
 262
 263 module_init(tproxy_tg_init);
 264 module_exit(tproxy_tg_exit);
 265 MODULE_LICENSE("GPL");
 266 MODULE_AUTHOR("Balazs Scheidler, Krisztian Kovacs");
 267 MODULE_DESCRIPTION("Netfilter transparent proxy (TPROXY) target module.");
 268 MODULE_ALIAS("ipt_TPROXY");
 269 MODULE_ALIAS("ip6t_TPROXY");