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net/netfilter/xt_TPROXY.c
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/* * Transparent proxy support for Linux/iptables * |
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* Copyright (c) 2006-2010 BalaBit IT Ltd. |
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* 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. * */ |
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
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#include <linux/module.h> #include <linux/skbuff.h> #include <linux/ip.h> #include <net/checksum.h> #include <net/udp.h> #include <net/inet_sock.h> |
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#include <linux/inetdevice.h> |
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#include <linux/netfilter/x_tables.h> #include <linux/netfilter_ipv4/ip_tables.h> |
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#include <net/netfilter/ipv4/nf_defrag_ipv4.h> |
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#if IS_ENABLED(CONFIG_IP6_NF_IPTABLES) |
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#define XT_TPROXY_HAVE_IPV6 1 |
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#include <net/if_inet6.h> #include <net/addrconf.h> #include <linux/netfilter_ipv6/ip6_tables.h> |
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#include <net/netfilter/ipv6/nf_defrag_ipv6.h> |
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#endif |
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#include <net/netfilter/nf_tproxy_core.h> |
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#include <linux/netfilter/xt_TPROXY.h> |
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static bool tproxy_sk_is_transparent(struct sock *sk) { if (sk->sk_state != TCP_TIME_WAIT) { if (inet_sk(sk)->transparent) return true; sock_put(sk); } else { if (inet_twsk(sk)->tw_transparent) return true; inet_twsk_put(inet_twsk(sk)); } return false; } |
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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; } |
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/** |
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* tproxy_handle_time_wait4() - handle IPv4 TCP TIME_WAIT reopen redirections |
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* @skb: The skb being processed. |
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* @laddr: IPv4 address to redirect to or zero. * @lport: TCP port to redirect to or zero. |
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* @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. * |
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* tproxy_handle_time_wait4() consumes the socket reference passed in. |
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* * 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 * |
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tproxy_handle_time_wait4(struct sk_buff *skb, __be32 laddr, __be16 lport, struct sock *sk) |
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{ const struct iphdr *iph = ip_hdr(skb); |
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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(dev_net(skb->dev), iph->protocol, |
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iph->saddr, laddr ? laddr : iph->daddr, hp->source, lport ? lport : hp->dest, skb->dev, NFT_LOOKUP_LISTENER); if (sk2) { inet_twsk_deschedule(inet_twsk(sk), &tcp_death_row); inet_twsk_put(inet_twsk(sk)); sk = sk2; } } return sk; } |
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static unsigned int |
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tproxy_tg4(struct sk_buff *skb, __be32 laddr, __be16 lport, u_int32_t mark_mask, u_int32_t mark_value) |
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{ const struct iphdr *iph = ip_hdr(skb); |
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struct udphdr _hdr, *hp; struct sock *sk; hp = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(_hdr), &_hdr); if (hp == NULL) return NF_DROP; |
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/* 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 */ |
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sk = nf_tproxy_get_sock_v4(dev_net(skb->dev), iph->protocol, |
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iph->saddr, iph->daddr, hp->source, hp->dest, |
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skb->dev, NFT_LOOKUP_ESTABLISHED); |
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laddr = tproxy_laddr4(skb, laddr, iph->daddr); if (!lport) lport = hp->dest; |
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/* UDP has no TCP_TIME_WAIT state, so we never enter here */ if (sk && sk->sk_state == TCP_TIME_WAIT) |
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/* reopening a TIME_WAIT connection needs special handling */ sk = tproxy_handle_time_wait4(skb, laddr, lport, sk); |
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else if (!sk) |
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/* no, there's no established connection, check if * there's a listener on the redirected addr/port */ |
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sk = nf_tproxy_get_sock_v4(dev_net(skb->dev), iph->protocol, |
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iph->saddr, laddr, hp->source, lport, |
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skb->dev, NFT_LOOKUP_LISTENER); /* NOTE: assign_sock consumes our sk reference */ |
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if (sk && tproxy_sk_is_transparent(sk)) { |
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/* 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 ", iph->protocol, &iph->daddr, ntohs(hp->dest), &laddr, ntohs(lport), skb->mark); |
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nf_tproxy_assign_sock(skb, sk); |
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return NF_ACCEPT; } |
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pr_debug("no socket, dropping: proto %hhu %pI4:%hu -> %pI4:%hu, mark: %x ", iph->protocol, &iph->saddr, ntohs(hp->source), &iph->daddr, ntohs(hp->dest), skb->mark); |
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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(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(skb, tgi->laddr.ip, tgi->lport, tgi->mark_mask, tgi->mark_value); } |
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#ifdef XT_TPROXY_HAVE_IPV6 |
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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(dev_net(skb->dev), 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(inet_twsk(sk), &tcp_death_row); inet_twsk_put(inet_twsk(sk)); sk = sk2; } } return sk; } |
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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; |
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const struct in6_addr *laddr; __be16 lport; |
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int thoff; int tproto; tproto = ipv6_find_hdr(skb, &thoff, -1, NULL); if (tproto < 0) { pr_debug("unable to find transport header in IPv6 packet, dropping "); 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 "); 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(dev_net(skb->dev), tproto, &iph->saddr, &iph->daddr, hp->source, hp->dest, par->in, NFT_LOOKUP_ESTABLISHED); |
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laddr = tproxy_laddr6(skb, &tgi->laddr.in6, &iph->daddr); lport = tgi->lport ? tgi->lport : hp->dest; |
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/* 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(dev_net(skb->dev), tproto, |
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&iph->saddr, laddr, hp->source, lport, |
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par->in, NFT_LOOKUP_LISTENER); |
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/* NOTE: assign_sock consumes our sk reference */ |
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if (sk && tproxy_sk_is_transparent(sk)) { |
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/* 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; |
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pr_debug("redirecting: proto %hhu %pI6:%hu -> %pI6:%hu, mark: %x ", |
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tproto, &iph->saddr, ntohs(hp->source), laddr, ntohs(lport), skb->mark); |
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nf_tproxy_assign_sock(skb, sk); |
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return NF_ACCEPT; } |
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pr_debug("no socket, dropping: proto %hhu %pI6:%hu -> %pI6:%hu, mark: %x ", |
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tproto, &iph->saddr, ntohs(hp->source), &iph->daddr, ntohs(hp->dest), skb->mark); |
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return NF_DROP; } |
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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->flags & IP6T_INV_PROTO)) return 0; pr_info("Can be used only in combination with " "either -p tcp or -p udp "); return -EINVAL; } #endif static int tproxy_tg4_check(const struct xt_tgchk_param *par) |
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{ |
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const struct ipt_ip *i = par->entryinfo; |
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if ((i->proto == IPPROTO_TCP || i->proto == IPPROTO_UDP) && !(i->invflags & IPT_INV_PROTO)) |
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return 0; |
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pr_info("Can be used only in combination with " |
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"either -p tcp or -p udp "); |
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return -EINVAL; |
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} |
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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, }, |
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#ifdef XT_TPROXY_HAVE_IPV6 |
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{ .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 |
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}; static int __init tproxy_tg_init(void) { nf_defrag_ipv4_enable(); |
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#ifdef XT_TPROXY_HAVE_IPV6 |
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nf_defrag_ipv6_enable(); #endif return xt_register_targets(tproxy_tg_reg, ARRAY_SIZE(tproxy_tg_reg)); |
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} static void __exit tproxy_tg_exit(void) { |
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xt_unregister_targets(tproxy_tg_reg, ARRAY_SIZE(tproxy_tg_reg)); |
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} module_init(tproxy_tg_init); module_exit(tproxy_tg_exit); MODULE_LICENSE("GPL"); |
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MODULE_AUTHOR("Balazs Scheidler, Krisztian Kovacs"); |
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MODULE_DESCRIPTION("Netfilter transparent proxy (TPROXY) target module."); MODULE_ALIAS("ipt_TPROXY"); |
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MODULE_ALIAS("ip6t_TPROXY"); |