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TOMOYO Linux Cross Reference
Linux/net/netfilter/xt_TPROXY.c

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  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 
 78                 pr_debug("redirecting: proto %hhu %pI4:%hu -> %pI4:%hu, mark: %x\n",
 79                          iph->protocol, &iph->daddr, ntohs(hp->dest),
 80                          &laddr, ntohs(lport), skb->mark);
 81 
 82                 nf_tproxy_assign_sock(skb, sk);
 83                 return NF_ACCEPT;
 84         }
 85 
 86         pr_debug("no socket, dropping: proto %hhu %pI4:%hu -> %pI4:%hu, mark: %x\n",
 87                  iph->protocol, &iph->saddr, ntohs(hp->source),
 88                  &iph->daddr, ntohs(hp->dest), skb->mark);
 89         return NF_DROP;
 90 }
 91 
 92 static unsigned int
 93 tproxy_tg4_v0(struct sk_buff *skb, const struct xt_action_param *par)
 94 {
 95         const struct xt_tproxy_target_info *tgi = par->targinfo;
 96 
 97         return tproxy_tg4(xt_net(par), skb, tgi->laddr, tgi->lport,
 98                           tgi->mark_mask, tgi->mark_value);
 99 }
100 
101 static unsigned int
102 tproxy_tg4_v1(struct sk_buff *skb, const struct xt_action_param *par)
103 {
104         const struct xt_tproxy_target_info_v1 *tgi = par->targinfo;
105 
106         return tproxy_tg4(xt_net(par), skb, tgi->laddr.ip, tgi->lport,
107                           tgi->mark_mask, tgi->mark_value);
108 }
109 
110 #ifdef XT_TPROXY_HAVE_IPV6
111 
112 static unsigned int
113 tproxy_tg6_v1(struct sk_buff *skb, const struct xt_action_param *par)
114 {
115         const struct ipv6hdr *iph = ipv6_hdr(skb);
116         const struct xt_tproxy_target_info_v1 *tgi = par->targinfo;
117         struct udphdr _hdr, *hp;
118         struct sock *sk;
119         const struct in6_addr *laddr;
120         __be16 lport;
121         int thoff = 0;
122         int tproto;
123 
124         tproto = ipv6_find_hdr(skb, &thoff, -1, NULL, NULL);
125         if (tproto < 0) {
126                 pr_debug("unable to find transport header in IPv6 packet, dropping\n");
127                 return NF_DROP;
128         }
129 
130         hp = skb_header_pointer(skb, thoff, sizeof(_hdr), &_hdr);
131         if (hp == NULL) {
132                 pr_debug("unable to grab transport header contents in IPv6 packet, dropping\n");
133                 return NF_DROP;
134         }
135 
136         /* check if there's an ongoing connection on the packet
137          * addresses, this happens if the redirect already happened
138          * and the current packet belongs to an already established
139          * connection */
140         sk = nf_tproxy_get_sock_v6(xt_net(par), skb, thoff, tproto,
141                                    &iph->saddr, &iph->daddr,
142                                    hp->source, hp->dest,
143                                    xt_in(par), NF_TPROXY_LOOKUP_ESTABLISHED);
144 
145         laddr = nf_tproxy_laddr6(skb, &tgi->laddr.in6, &iph->daddr);
146         lport = tgi->lport ? tgi->lport : hp->dest;
147 
148         /* UDP has no TCP_TIME_WAIT state, so we never enter here */
149         if (sk && sk->sk_state == TCP_TIME_WAIT) {
150                 const struct xt_tproxy_target_info_v1 *tgi = par->targinfo;
151                 /* reopening a TIME_WAIT connection needs special handling */
152                 sk = nf_tproxy_handle_time_wait6(skb, tproto, thoff,
153                                               xt_net(par),
154                                               &tgi->laddr.in6,
155                                               tgi->lport,
156                                               sk);
157         }
158         else if (!sk)
159                 /* no there's no established connection, check if
160                  * there's a listener on the redirected addr/port */
161                 sk = nf_tproxy_get_sock_v6(xt_net(par), skb, thoff,
162                                            tproto, &iph->saddr, laddr,
163                                            hp->source, lport,
164                                            xt_in(par), NF_TPROXY_LOOKUP_LISTENER);
165 
166         /* NOTE: assign_sock consumes our sk reference */
167         if (sk && nf_tproxy_sk_is_transparent(sk)) {
168                 /* This should be in a separate target, but we don't do multiple
169                    targets on the same rule yet */
170                 skb->mark = (skb->mark & ~tgi->mark_mask) ^ tgi->mark_value;
171 
172                 pr_debug("redirecting: proto %hhu %pI6:%hu -> %pI6:%hu, mark: %x\n",
173                          tproto, &iph->saddr, ntohs(hp->source),
174                          laddr, ntohs(lport), skb->mark);
175 
176                 nf_tproxy_assign_sock(skb, sk);
177                 return NF_ACCEPT;
178         }
179 
180         pr_debug("no socket, dropping: proto %hhu %pI6:%hu -> %pI6:%hu, mark: %x\n",
181                  tproto, &iph->saddr, ntohs(hp->source),
182                  &iph->daddr, ntohs(hp->dest), skb->mark);
183 
184         return NF_DROP;
185 }
186 
187 static int tproxy_tg6_check(const struct xt_tgchk_param *par)
188 {
189         const struct ip6t_ip6 *i = par->entryinfo;
190         int err;
191 
192         err = nf_defrag_ipv6_enable(par->net);
193         if (err)
194                 return err;
195 
196         if ((i->proto == IPPROTO_TCP || i->proto == IPPROTO_UDP) &&
197             !(i->invflags & IP6T_INV_PROTO))
198                 return 0;
199 
200         pr_info_ratelimited("Can be used only with -p tcp or -p udp\n");
201         return -EINVAL;
202 }
203 #endif
204 
205 static int tproxy_tg4_check(const struct xt_tgchk_param *par)
206 {
207         const struct ipt_ip *i = par->entryinfo;
208         int err;
209 
210         err = nf_defrag_ipv4_enable(par->net);
211         if (err)
212                 return err;
213 
214         if ((i->proto == IPPROTO_TCP || i->proto == IPPROTO_UDP)
215             && !(i->invflags & IPT_INV_PROTO))
216                 return 0;
217 
218         pr_info_ratelimited("Can be used only with -p tcp or -p udp\n");
219         return -EINVAL;
220 }
221 
222 static struct xt_target tproxy_tg_reg[] __read_mostly = {
223         {
224                 .name           = "TPROXY",
225                 .family         = NFPROTO_IPV4,
226                 .table          = "mangle",
227                 .target         = tproxy_tg4_v0,
228                 .revision       = 0,
229                 .targetsize     = sizeof(struct xt_tproxy_target_info),
230                 .checkentry     = tproxy_tg4_check,
231                 .hooks          = 1 << NF_INET_PRE_ROUTING,
232                 .me             = THIS_MODULE,
233         },
234         {
235                 .name           = "TPROXY",
236                 .family         = NFPROTO_IPV4,
237                 .table          = "mangle",
238                 .target         = tproxy_tg4_v1,
239                 .revision       = 1,
240                 .targetsize     = sizeof(struct xt_tproxy_target_info_v1),
241                 .checkentry     = tproxy_tg4_check,
242                 .hooks          = 1 << NF_INET_PRE_ROUTING,
243                 .me             = THIS_MODULE,
244         },
245 #ifdef XT_TPROXY_HAVE_IPV6
246         {
247                 .name           = "TPROXY",
248                 .family         = NFPROTO_IPV6,
249                 .table          = "mangle",
250                 .target         = tproxy_tg6_v1,
251                 .revision       = 1,
252                 .targetsize     = sizeof(struct xt_tproxy_target_info_v1),
253                 .checkentry     = tproxy_tg6_check,
254                 .hooks          = 1 << NF_INET_PRE_ROUTING,
255                 .me             = THIS_MODULE,
256         },
257 #endif
258 
259 };
260 
261 static int __init tproxy_tg_init(void)
262 {
263         return xt_register_targets(tproxy_tg_reg, ARRAY_SIZE(tproxy_tg_reg));
264 }
265 
266 static void __exit tproxy_tg_exit(void)
267 {
268         xt_unregister_targets(tproxy_tg_reg, ARRAY_SIZE(tproxy_tg_reg));
269 }
270 
271 module_init(tproxy_tg_init);
272 module_exit(tproxy_tg_exit);
273 MODULE_LICENSE("GPL");
274 MODULE_AUTHOR("Balazs Scheidler, Krisztian Kovacs");
275 MODULE_DESCRIPTION("Netfilter transparent proxy (TPROXY) target module.");
276 MODULE_ALIAS("ipt_TPROXY");
277 MODULE_ALIAS("ip6t_TPROXY");
278 

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