diff options
Diffstat (limited to 'net/netfilter/xt_TPROXY.c')
| -rw-r--r-- | net/netfilter/xt_TPROXY.c | 432 |
1 files changed, 432 insertions, 0 deletions
diff --git a/net/netfilter/xt_TPROXY.c b/net/netfilter/xt_TPROXY.c new file mode 100644 index 00000000..dcfd57eb --- /dev/null +++ b/net/netfilter/xt_TPROXY.c @@ -0,0 +1,432 @@ +/* + * 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 <linux/module.h> +#include <linux/skbuff.h> +#include <linux/ip.h> +#include <net/checksum.h> +#include <net/udp.h> +#include <net/inet_sock.h> +#include <linux/inetdevice.h> +#include <linux/netfilter/x_tables.h> +#include <linux/netfilter_ipv4/ip_tables.h> + +#include <net/netfilter/ipv4/nf_defrag_ipv4.h> + +#if defined(CONFIG_IP6_NF_IPTABLES) || defined(CONFIG_IP6_NF_IPTABLES_MODULE) +#define XT_TPROXY_HAVE_IPV6 1 +#include <net/if_inet6.h> +#include <net/addrconf.h> +#include <linux/netfilter_ipv6/ip6_tables.h> +#include <net/netfilter/ipv6/nf_defrag_ipv6.h> +#endif + +#include <net/netfilter/nf_tproxy_core.h> +#include <linux/netfilter/xt_TPROXY.h> + +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; +} + +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; +} + +/** + * 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 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(dev_net(skb->dev), iph->protocol, + 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; +} + +static unsigned int +tproxy_tg4(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(dev_net(skb->dev), 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(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(dev_net(skb->dev), 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(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); +} + +#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(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; +} + +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; + int tproto; + + tproto = ipv6_find_hdr(skb, &thoff, -1, 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(dev_net(skb->dev), 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(dev_net(skb->dev), 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->flags & 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"); |