/* * Transparent proxy support for Linux/iptables * * Copyright (c) 2006-2010 BalaBit IT Ltd. * Author: Balazs Scheidler, Krisztian Kovacs * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License version 2 as * published by the Free Software Foundation. * */ #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt #include #include #include #include #include #include #include #include #include #include #include #include #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES) #define XT_TPROXY_HAVE_IPV6 1 #include #include #include #include #include #endif #include enum nf_tproxy_lookup_t { NFT_LOOKUP_LISTENER, NFT_LOOKUP_ESTABLISHED, }; static bool tproxy_sk_is_transparent(struct sock *sk) { switch (sk->sk_state) { case TCP_TIME_WAIT: if (inet_twsk(sk)->tw_transparent) return true; break; case TCP_NEW_SYN_RECV: if (inet_rsk(inet_reqsk(sk))->no_srccheck) return true; break; default: if (inet_sk(sk)->transparent) return true; } sock_gen_put(sk); return false; } static inline __be32 tproxy_laddr4(struct sk_buff *skb, __be32 user_laddr, __be32 daddr) { struct in_device *indev; __be32 laddr; if (user_laddr) return user_laddr; laddr = 0; rcu_read_lock(); indev = __in_dev_get_rcu(skb->dev); for_primary_ifa(indev) { laddr = ifa->ifa_local; break; } endfor_ifa(indev); rcu_read_unlock(); return laddr ? laddr : daddr; } /* * This is used when the user wants to intercept a connection matching * an explicit iptables rule. In this case the sockets are assumed * matching in preference order: * * - match: if there's a fully established connection matching the * _packet_ tuple, it is returned, assuming the redirection * already took place and we process a packet belonging to an * established connection * * - match: if there's a listening socket matching the redirection * (e.g. on-port & on-ip of the connection), it is returned, * regardless if it was bound to 0.0.0.0 or an explicit * address. The reasoning is that if there's an explicit rule, it * does not really matter if the listener is bound to an interface * or to 0. The user already stated that he wants redirection * (since he added the rule). * * Please note that there's an overlap between what a TPROXY target * and a socket match will match. Normally if you have both rules the * "socket" match will be the first one, effectively all packets * belonging to established connections going through that one. */ static inline struct sock * nf_tproxy_get_sock_v4(struct net *net, const u8 protocol, const __be32 saddr, const __be32 daddr, const __be16 sport, const __be16 dport, const struct net_device *in, const enum nf_tproxy_lookup_t lookup_type) { struct sock *sk; switch (protocol) { case IPPROTO_TCP: switch (lookup_type) { case NFT_LOOKUP_LISTENER: sk = inet_lookup_listener(net, &tcp_hashinfo, saddr, sport, daddr, dport, in->ifindex); /* NOTE: we return listeners even if bound to * 0.0.0.0, those are filtered out in * xt_socket, since xt_TPROXY needs 0 bound * listeners too */ break; case NFT_LOOKUP_ESTABLISHED: sk = inet_lookup_established(net, &tcp_hashinfo, saddr, sport, daddr, dport, in->ifindex); break; default: BUG(); } break; case IPPROTO_UDP: sk = udp4_lib_lookup(net, saddr, sport, daddr, dport, in->ifindex); if (sk) { int connected = (sk->sk_state == TCP_ESTABLISHED); int wildcard = (inet_sk(sk)->inet_rcv_saddr == 0); /* NOTE: we return listeners even if bound to * 0.0.0.0, those are filtered out in * xt_socket, since xt_TPROXY needs 0 bound * listeners too */ if ((lookup_type == NFT_LOOKUP_ESTABLISHED && (!connected || wildcard)) || (lookup_type == NFT_LOOKUP_LISTENER && connected)) { sock_put(sk); sk = NULL; } } break; default: WARN_ON(1); sk = NULL; } pr_debug("tproxy socket lookup: proto %u %08x:%u -> %08x:%u, lookup type: %d, sock %p\n", protocol, ntohl(saddr), ntohs(sport), ntohl(daddr), ntohs(dport), lookup_type, sk); return sk; } #ifdef XT_TPROXY_HAVE_IPV6 static inline struct sock * nf_tproxy_get_sock_v6(struct net *net, const u8 protocol, const struct in6_addr *saddr, const struct in6_addr *daddr, const __be16 sport, const __be16 dport, const struct net_device *in, const enum nf_tproxy_lookup_t lookup_type) { struct sock *sk; switch (protocol) { case IPPROTO_TCP: switch (lookup_type) { case NFT_LOOKUP_LISTENER: sk = inet6_lookup_listener(net, &tcp_hashinfo, saddr, sport, daddr, ntohs(dport), in->ifindex); /* NOTE: we return listeners even if bound to * 0.0.0.0, those are filtered out in * xt_socket, since xt_TPROXY needs 0 bound * listeners too */ break; case NFT_LOOKUP_ESTABLISHED: sk = __inet6_lookup_established(net, &tcp_hashinfo, saddr, sport, daddr, ntohs(dport), in->ifindex); break; default: BUG(); } break; case IPPROTO_UDP: sk = udp6_lib_lookup(net, saddr, sport, daddr, dport, in->ifindex); if (sk) { int connected = (sk->sk_state == TCP_ESTABLISHED); int wildcard = ipv6_addr_any(&sk->sk_v6_rcv_saddr); /* NOTE: we return listeners even if bound to * 0.0.0.0, those are filtered out in * xt_socket, since xt_TPROXY needs 0 bound * listeners too */ if ((lookup_type == NFT_LOOKUP_ESTABLISHED && (!connected || wildcard)) || (lookup_type == NFT_LOOKUP_LISTENER && connected)) { sock_put(sk); sk = NULL; } } break; default: WARN_ON(1); sk = NULL; } pr_debug("tproxy socket lookup: proto %u %pI6:%u -> %pI6:%u, lookup type: %d, sock %p\n", protocol, saddr, ntohs(sport), daddr, ntohs(dport), lookup_type, sk); return sk; } #endif /** * tproxy_handle_time_wait4 - handle IPv4 TCP TIME_WAIT reopen redirections * @skb: The skb being processed. * @laddr: IPv4 address to redirect to or zero. * @lport: TCP port to redirect to or zero. * @sk: The TIME_WAIT TCP socket found by the lookup. * * We have to handle SYN packets arriving to TIME_WAIT sockets * differently: instead of reopening the connection we should rather * redirect the new connection to the proxy if there's a listener * socket present. * * tproxy_handle_time_wait4() consumes the socket reference passed in. * * Returns the listener socket if there's one, the TIME_WAIT socket if * no such listener is found, or NULL if the TCP header is incomplete. */ static struct sock * tproxy_handle_time_wait4(struct net *net, struct sk_buff *skb, __be32 laddr, __be16 lport, struct sock *sk) { const struct iphdr *iph = ip_hdr(skb); struct tcphdr _hdr, *hp; hp = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(_hdr), &_hdr); if (hp == NULL) { inet_twsk_put(inet_twsk(sk)); return NULL; } if (hp->syn && !hp->rst && !hp->ack && !hp->fin) { /* SYN to a TIME_WAIT socket, we'd rather redirect it * to a listener socket if there's one */ struct sock *sk2; sk2 = nf_tproxy_get_sock_v4(net, iph->protocol, iph->saddr, laddr ? laddr : iph->daddr, hp->source, lport ? lport : hp->dest, skb->dev, NFT_LOOKUP_LISTENER); if (sk2) { inet_twsk_deschedule_put(inet_twsk(sk)); sk = sk2; } } return sk; } /* assign a socket to the skb -- consumes sk */ static void nf_tproxy_assign_sock(struct sk_buff *skb, struct sock *sk) { skb_orphan(skb); skb->sk = sk; skb->destructor = sock_edemux; } 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) { const struct iphdr *iph = ip_hdr(skb); struct udphdr _hdr, *hp; struct sock *sk; hp = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(_hdr), &_hdr); if (hp == NULL) return NF_DROP; /* check if there's an ongoing connection on the packet * addresses, this happens if the redirect already happened * and the current packet belongs to an already established * connection */ sk = nf_tproxy_get_sock_v4(net, iph->protocol, iph->saddr, iph->daddr, hp->source, hp->dest, skb->dev, NFT_LOOKUP_ESTABLISHED); laddr = tproxy_laddr4(skb, laddr, iph->daddr); if (!lport) lport = hp->dest; /* UDP has no TCP_TIME_WAIT state, so we never enter here */ if (sk && sk->sk_state == TCP_TIME_WAIT) /* reopening a TIME_WAIT connection needs special handling */ sk = tproxy_handle_time_wait4(net, skb, laddr, lport, sk); else if (!sk) /* no, there's no established connection, check if * there's a listener on the redirected addr/port */ sk = nf_tproxy_get_sock_v4(net, iph->protocol, iph->saddr, laddr, hp->source, lport, skb->dev, NFT_LOOKUP_LISTENER); /* NOTE: assign_sock consumes our sk reference */ if (sk && tproxy_sk_is_transparent(sk)) { /* This should be in a separate target, but we don't do multiple targets on the same rule yet */ skb->mark = (skb->mark & ~mark_mask) ^ mark_value; pr_debug("redirecting: proto %hhu %pI4:%hu -> %pI4:%hu, mark: %x\n", iph->protocol, &iph->daddr, ntohs(hp->dest), &laddr, ntohs(lport), skb->mark); nf_tproxy_assign_sock(skb, sk); return NF_ACCEPT; } pr_debug("no socket, dropping: proto %hhu %pI4:%hu -> %pI4:%hu, mark: %x\n", iph->protocol, &iph->saddr, ntohs(hp->source), &iph->daddr, ntohs(hp->dest), skb->mark); return NF_DROP; } static unsigned int tproxy_tg4_v0(struct sk_buff *skb, const struct xt_action_param *par) { const struct xt_tproxy_target_info *tgi = par->targinfo; return tproxy_tg4(par->net, skb, tgi->laddr, tgi->lport, tgi->mark_mask, tgi->mark_value); } static unsigned int tproxy_tg4_v1(struct sk_buff *skb, const struct xt_action_param *par) { const struct xt_tproxy_target_info_v1 *tgi = par->targinfo; return tproxy_tg4(par->net, skb, tgi->laddr.ip, tgi->lport, tgi->mark_mask, tgi->mark_value); } #ifdef XT_TPROXY_HAVE_IPV6 static inline const struct in6_addr * tproxy_laddr6(struct sk_buff *skb, const struct in6_addr *user_laddr, const struct in6_addr *daddr) { struct inet6_dev *indev; struct inet6_ifaddr *ifa; struct in6_addr *laddr; if (!ipv6_addr_any(user_laddr)) return user_laddr; laddr = NULL; rcu_read_lock(); indev = __in6_dev_get(skb->dev); if (indev) list_for_each_entry(ifa, &indev->addr_list, if_list) { if (ifa->flags & (IFA_F_TENTATIVE | IFA_F_DEPRECATED)) continue; laddr = &ifa->addr; break; } rcu_read_unlock(); return laddr ? laddr : daddr; } /** * tproxy_handle_time_wait6 - handle IPv6 TCP TIME_WAIT reopen redirections * @skb: The skb being processed. * @tproto: Transport protocol. * @thoff: Transport protocol header offset. * @par: Iptables target parameters. * @sk: The TIME_WAIT TCP socket found by the lookup. * * We have to handle SYN packets arriving to TIME_WAIT sockets * differently: instead of reopening the connection we should rather * redirect the new connection to the proxy if there's a listener * socket present. * * tproxy_handle_time_wait6() consumes the socket reference passed in. * * Returns the listener socket if there's one, the TIME_WAIT socket if * no such listener is found, or NULL if the TCP header is incomplete. */ static struct sock * tproxy_handle_time_wait6(struct sk_buff *skb, int tproto, int thoff, const struct xt_action_param *par, struct sock *sk) { const struct ipv6hdr *iph = ipv6_hdr(skb); struct tcphdr _hdr, *hp; const struct xt_tproxy_target_info_v1 *tgi = par->targinfo; hp = skb_header_pointer(skb, thoff, sizeof(_hdr), &_hdr); if (hp == NULL) { inet_twsk_put(inet_twsk(sk)); return NULL; } if (hp->syn && !hp->rst && !hp->ack && !hp->fin) { /* SYN to a TIME_WAIT socket, we'd rather redirect it * to a listener socket if there's one */ struct sock *sk2; sk2 = nf_tproxy_get_sock_v6(par->net, tproto, &iph->saddr, tproxy_laddr6(skb, &tgi->laddr.in6, &iph->daddr), hp->source, tgi->lport ? tgi->lport : hp->dest, skb->dev, NFT_LOOKUP_LISTENER); if (sk2) { inet_twsk_deschedule_put(inet_twsk(sk)); sk = sk2; } } return sk; } static unsigned int tproxy_tg6_v1(struct sk_buff *skb, const struct xt_action_param *par) { const struct ipv6hdr *iph = ipv6_hdr(skb); const struct xt_tproxy_target_info_v1 *tgi = par->targinfo; struct udphdr _hdr, *hp; struct sock *sk; const struct in6_addr *laddr; __be16 lport; int thoff = 0; int tproto; tproto = ipv6_find_hdr(skb, &thoff, -1, NULL, NULL); if (tproto < 0) { pr_debug("unable to find transport header in IPv6 packet, dropping\n"); return NF_DROP; } hp = skb_header_pointer(skb, thoff, sizeof(_hdr), &_hdr); if (hp == NULL) { pr_debug("unable to grab transport header contents in IPv6 packet, dropping\n"); return NF_DROP; } /* check if there's an ongoing connection on the packet * addresses, this happens if the redirect already happened * and the current packet belongs to an already established * connection */ sk = nf_tproxy_get_sock_v6(par->net, tproto, &iph->saddr, &iph->daddr, hp->source, hp->dest, par->in, NFT_LOOKUP_ESTABLISHED); laddr = tproxy_laddr6(skb, &tgi->laddr.in6, &iph->daddr); lport = tgi->lport ? tgi->lport : hp->dest; /* UDP has no TCP_TIME_WAIT state, so we never enter here */ if (sk && sk->sk_state == TCP_TIME_WAIT) /* reopening a TIME_WAIT connection needs special handling */ sk = tproxy_handle_time_wait6(skb, tproto, thoff, par, sk); else if (!sk) /* no there's no established connection, check if * there's a listener on the redirected addr/port */ sk = nf_tproxy_get_sock_v6(par->net, tproto, &iph->saddr, laddr, hp->source, lport, par->in, NFT_LOOKUP_LISTENER); /* NOTE: assign_sock consumes our sk reference */ if (sk && tproxy_sk_is_transparent(sk)) { /* This should be in a separate target, but we don't do multiple targets on the same rule yet */ skb->mark = (skb->mark & ~tgi->mark_mask) ^ tgi->mark_value; pr_debug("redirecting: proto %hhu %pI6:%hu -> %pI6:%hu, mark: %x\n", tproto, &iph->saddr, ntohs(hp->source), laddr, ntohs(lport), skb->mark); nf_tproxy_assign_sock(skb, sk); return NF_ACCEPT; } pr_debug("no socket, dropping: proto %hhu %pI6:%hu -> %pI6:%hu, mark: %x\n", tproto, &iph->saddr, ntohs(hp->source), &iph->daddr, ntohs(hp->dest), skb->mark); return NF_DROP; } static int tproxy_tg6_check(const struct xt_tgchk_param *par) { const struct ip6t_ip6 *i = par->entryinfo; if ((i->proto == IPPROTO_TCP || i->proto == IPPROTO_UDP) && !(i->invflags & IP6T_INV_PROTO)) return 0; pr_info("Can be used only in combination with " "either -p tcp or -p udp\n"); return -EINVAL; } #endif static int tproxy_tg4_check(const struct xt_tgchk_param *par) { const struct ipt_ip *i = par->entryinfo; if ((i->proto == IPPROTO_TCP || i->proto == IPPROTO_UDP) && !(i->invflags & IPT_INV_PROTO)) return 0; pr_info("Can be used only in combination with " "either -p tcp or -p udp\n"); return -EINVAL; } static struct xt_target tproxy_tg_reg[] __read_mostly = { { .name = "TPROXY", .family = NFPROTO_IPV4, .table = "mangle", .target = tproxy_tg4_v0, .revision = 0, .targetsize = sizeof(struct xt_tproxy_target_info), .checkentry = tproxy_tg4_check, .hooks = 1 << NF_INET_PRE_ROUTING, .me = THIS_MODULE, }, { .name = "TPROXY", .family = NFPROTO_IPV4, .table = "mangle", .target = tproxy_tg4_v1, .revision = 1, .targetsize = sizeof(struct xt_tproxy_target_info_v1), .checkentry = tproxy_tg4_check, .hooks = 1 << NF_INET_PRE_ROUTING, .me = THIS_MODULE, }, #ifdef XT_TPROXY_HAVE_IPV6 { .name = "TPROXY", .family = NFPROTO_IPV6, .table = "mangle", .target = tproxy_tg6_v1, .revision = 1, .targetsize = sizeof(struct xt_tproxy_target_info_v1), .checkentry = tproxy_tg6_check, .hooks = 1 << NF_INET_PRE_ROUTING, .me = THIS_MODULE, }, #endif }; static int __init tproxy_tg_init(void) { nf_defrag_ipv4_enable(); #ifdef XT_TPROXY_HAVE_IPV6 nf_defrag_ipv6_enable(); #endif return xt_register_targets(tproxy_tg_reg, ARRAY_SIZE(tproxy_tg_reg)); } static void __exit tproxy_tg_exit(void) { xt_unregister_targets(tproxy_tg_reg, ARRAY_SIZE(tproxy_tg_reg)); } module_init(tproxy_tg_init); module_exit(tproxy_tg_exit); MODULE_LICENSE("GPL"); MODULE_AUTHOR("Balazs Scheidler, Krisztian Kovacs"); MODULE_DESCRIPTION("Netfilter transparent proxy (TPROXY) target module."); MODULE_ALIAS("ipt_TPROXY"); MODULE_ALIAS("ip6t_TPROXY");