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
tproxy_tg4(struct net * net,struct sk_buff * skb,__be32 laddr,__be16 lport,u_int32_t mark_mask,u_int32_t mark_value)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
tproxy_tg4_v0(struct sk_buff * skb,const struct xt_action_param * par)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
tproxy_tg4_v1(struct sk_buff * skb,const struct xt_action_param * par)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
tproxy_tg6_v1(struct sk_buff * skb,const struct xt_action_param * par)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
tproxy_tg6_check(const struct xt_tgchk_param * par)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
tproxy_tg6_destroy(const struct xt_tgdtor_param * par)183 static void tproxy_tg6_destroy(const struct xt_tgdtor_param *par)
184 {
185 nf_defrag_ipv6_disable(par->net);
186 }
187 #endif
188
tproxy_tg4_check(const struct xt_tgchk_param * par)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
tproxy_tg4_destroy(const struct xt_tgdtor_param * par)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
tproxy_tg_init(void)253 static int __init tproxy_tg_init(void)
254 {
255 return xt_register_targets(tproxy_tg_reg, ARRAY_SIZE(tproxy_tg_reg));
256 }
257
tproxy_tg_exit(void)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");
270