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- // SPDX-License-Identifier: GPL-2.0-only
- /*
- * Transparent proxy support for Linux/iptables
- *
- * Copyright (C) 2007-2008 BalaBit IT Ltd.
- * Author: Krisztian Kovacs
- */
- #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
- #include <linux/module.h>
- #include <linux/skbuff.h>
- #include <linux/netfilter/x_tables.h>
- #include <linux/netfilter_ipv4/ip_tables.h>
- #include <net/tcp.h>
- #include <net/udp.h>
- #include <net/icmp.h>
- #include <net/sock.h>
- #include <net/inet_sock.h>
- #include <net/netfilter/ipv4/nf_defrag_ipv4.h>
- #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
- #include <linux/netfilter_ipv6/ip6_tables.h>
- #include <net/inet6_hashtables.h>
- #include <net/netfilter/ipv6/nf_defrag_ipv6.h>
- #endif
- #include <net/netfilter/nf_socket.h>
- #include <linux/netfilter/xt_socket.h>
- /* "socket" match based redirection (no specific rule)
- * ===================================================
- *
- * There are connections with dynamic endpoints (e.g. FTP data
- * connection) that the user is unable to add explicit rules
- * for. These are taken care of by a generic "socket" rule. It is
- * assumed that the proxy application is trusted to open such
- * connections without explicit iptables rule (except of course the
- * generic 'socket' rule). In this case the following sockets are
- * matched in preference order:
- *
- * - match: if there's a fully established connection matching the
- * _packet_ tuple
- *
- * - match: if there's a non-zero bound listener (possibly with a
- * non-local address) We don't accept zero-bound listeners, since
- * then local services could intercept traffic going through the
- * box.
- */
- static bool
- socket_match(const struct sk_buff *skb, struct xt_action_param *par,
- const struct xt_socket_mtinfo1 *info)
- {
- struct sk_buff *pskb = (struct sk_buff *)skb;
- struct sock *sk = skb->sk;
- if (sk && !net_eq(xt_net(par), sock_net(sk)))
- sk = NULL;
- if (!sk)
- sk = nf_sk_lookup_slow_v4(xt_net(par), skb, xt_in(par));
- if (sk) {
- bool wildcard;
- bool transparent = true;
- /* Ignore sockets listening on INADDR_ANY,
- * unless XT_SOCKET_NOWILDCARD is set
- */
- wildcard = (!(info->flags & XT_SOCKET_NOWILDCARD) &&
- sk_fullsock(sk) &&
- inet_sk(sk)->inet_rcv_saddr == 0);
- /* Ignore non-transparent sockets,
- * if XT_SOCKET_TRANSPARENT is used
- */
- if (info->flags & XT_SOCKET_TRANSPARENT)
- transparent = inet_sk_transparent(sk);
- if (info->flags & XT_SOCKET_RESTORESKMARK && !wildcard &&
- transparent && sk_fullsock(sk))
- pskb->mark = sk->sk_mark;
- if (sk != skb->sk)
- sock_gen_put(sk);
- if (wildcard || !transparent)
- sk = NULL;
- }
- return sk != NULL;
- }
- static bool
- socket_mt4_v0(const struct sk_buff *skb, struct xt_action_param *par)
- {
- static struct xt_socket_mtinfo1 xt_info_v0 = {
- .flags = 0,
- };
- return socket_match(skb, par, &xt_info_v0);
- }
- static bool
- socket_mt4_v1_v2_v3(const struct sk_buff *skb, struct xt_action_param *par)
- {
- return socket_match(skb, par, par->matchinfo);
- }
- #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
- static bool
- socket_mt6_v1_v2_v3(const struct sk_buff *skb, struct xt_action_param *par)
- {
- const struct xt_socket_mtinfo1 *info = (struct xt_socket_mtinfo1 *) par->matchinfo;
- struct sk_buff *pskb = (struct sk_buff *)skb;
- struct sock *sk = skb->sk;
- if (sk && !net_eq(xt_net(par), sock_net(sk)))
- sk = NULL;
- if (!sk)
- sk = nf_sk_lookup_slow_v6(xt_net(par), skb, xt_in(par));
- if (sk) {
- bool wildcard;
- bool transparent = true;
- /* Ignore sockets listening on INADDR_ANY
- * unless XT_SOCKET_NOWILDCARD is set
- */
- wildcard = (!(info->flags & XT_SOCKET_NOWILDCARD) &&
- sk_fullsock(sk) &&
- ipv6_addr_any(&sk->sk_v6_rcv_saddr));
- /* Ignore non-transparent sockets,
- * if XT_SOCKET_TRANSPARENT is used
- */
- if (info->flags & XT_SOCKET_TRANSPARENT)
- transparent = inet_sk_transparent(sk);
- if (info->flags & XT_SOCKET_RESTORESKMARK && !wildcard &&
- transparent && sk_fullsock(sk))
- pskb->mark = sk->sk_mark;
- if (sk != skb->sk)
- sock_gen_put(sk);
- if (wildcard || !transparent)
- sk = NULL;
- }
- return sk != NULL;
- }
- #endif
- static int socket_mt_enable_defrag(struct net *net, int family)
- {
- switch (family) {
- case NFPROTO_IPV4:
- return nf_defrag_ipv4_enable(net);
- #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
- case NFPROTO_IPV6:
- return nf_defrag_ipv6_enable(net);
- #endif
- }
- WARN_ONCE(1, "Unknown family %d\n", family);
- return 0;
- }
- static int socket_mt_v1_check(const struct xt_mtchk_param *par)
- {
- const struct xt_socket_mtinfo1 *info = (struct xt_socket_mtinfo1 *) par->matchinfo;
- int err;
- err = socket_mt_enable_defrag(par->net, par->family);
- if (err)
- return err;
- if (info->flags & ~XT_SOCKET_FLAGS_V1) {
- pr_info_ratelimited("unknown flags 0x%x\n",
- info->flags & ~XT_SOCKET_FLAGS_V1);
- return -EINVAL;
- }
- return 0;
- }
- static int socket_mt_v2_check(const struct xt_mtchk_param *par)
- {
- const struct xt_socket_mtinfo2 *info = (struct xt_socket_mtinfo2 *) par->matchinfo;
- int err;
- err = socket_mt_enable_defrag(par->net, par->family);
- if (err)
- return err;
- if (info->flags & ~XT_SOCKET_FLAGS_V2) {
- pr_info_ratelimited("unknown flags 0x%x\n",
- info->flags & ~XT_SOCKET_FLAGS_V2);
- return -EINVAL;
- }
- return 0;
- }
- static int socket_mt_v3_check(const struct xt_mtchk_param *par)
- {
- const struct xt_socket_mtinfo3 *info =
- (struct xt_socket_mtinfo3 *)par->matchinfo;
- int err;
- err = socket_mt_enable_defrag(par->net, par->family);
- if (err)
- return err;
- if (info->flags & ~XT_SOCKET_FLAGS_V3) {
- pr_info_ratelimited("unknown flags 0x%x\n",
- info->flags & ~XT_SOCKET_FLAGS_V3);
- return -EINVAL;
- }
- return 0;
- }
- static struct xt_match socket_mt_reg[] __read_mostly = {
- {
- .name = "socket",
- .revision = 0,
- .family = NFPROTO_IPV4,
- .match = socket_mt4_v0,
- .hooks = (1 << NF_INET_PRE_ROUTING) |
- (1 << NF_INET_LOCAL_IN),
- .me = THIS_MODULE,
- },
- {
- .name = "socket",
- .revision = 1,
- .family = NFPROTO_IPV4,
- .match = socket_mt4_v1_v2_v3,
- .checkentry = socket_mt_v1_check,
- .matchsize = sizeof(struct xt_socket_mtinfo1),
- .hooks = (1 << NF_INET_PRE_ROUTING) |
- (1 << NF_INET_LOCAL_IN),
- .me = THIS_MODULE,
- },
- #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
- {
- .name = "socket",
- .revision = 1,
- .family = NFPROTO_IPV6,
- .match = socket_mt6_v1_v2_v3,
- .checkentry = socket_mt_v1_check,
- .matchsize = sizeof(struct xt_socket_mtinfo1),
- .hooks = (1 << NF_INET_PRE_ROUTING) |
- (1 << NF_INET_LOCAL_IN),
- .me = THIS_MODULE,
- },
- #endif
- {
- .name = "socket",
- .revision = 2,
- .family = NFPROTO_IPV4,
- .match = socket_mt4_v1_v2_v3,
- .checkentry = socket_mt_v2_check,
- .matchsize = sizeof(struct xt_socket_mtinfo1),
- .hooks = (1 << NF_INET_PRE_ROUTING) |
- (1 << NF_INET_LOCAL_IN),
- .me = THIS_MODULE,
- },
- #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
- {
- .name = "socket",
- .revision = 2,
- .family = NFPROTO_IPV6,
- .match = socket_mt6_v1_v2_v3,
- .checkentry = socket_mt_v2_check,
- .matchsize = sizeof(struct xt_socket_mtinfo1),
- .hooks = (1 << NF_INET_PRE_ROUTING) |
- (1 << NF_INET_LOCAL_IN),
- .me = THIS_MODULE,
- },
- #endif
- {
- .name = "socket",
- .revision = 3,
- .family = NFPROTO_IPV4,
- .match = socket_mt4_v1_v2_v3,
- .checkentry = socket_mt_v3_check,
- .matchsize = sizeof(struct xt_socket_mtinfo1),
- .hooks = (1 << NF_INET_PRE_ROUTING) |
- (1 << NF_INET_LOCAL_IN),
- .me = THIS_MODULE,
- },
- #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
- {
- .name = "socket",
- .revision = 3,
- .family = NFPROTO_IPV6,
- .match = socket_mt6_v1_v2_v3,
- .checkentry = socket_mt_v3_check,
- .matchsize = sizeof(struct xt_socket_mtinfo1),
- .hooks = (1 << NF_INET_PRE_ROUTING) |
- (1 << NF_INET_LOCAL_IN),
- .me = THIS_MODULE,
- },
- #endif
- };
- static int __init socket_mt_init(void)
- {
- return xt_register_matches(socket_mt_reg, ARRAY_SIZE(socket_mt_reg));
- }
- static void __exit socket_mt_exit(void)
- {
- xt_unregister_matches(socket_mt_reg, ARRAY_SIZE(socket_mt_reg));
- }
- module_init(socket_mt_init);
- module_exit(socket_mt_exit);
- MODULE_LICENSE("GPL");
- MODULE_AUTHOR("Krisztian Kovacs, Balazs Scheidler");
- MODULE_DESCRIPTION("x_tables socket match module");
- MODULE_ALIAS("ipt_socket");
- MODULE_ALIAS("ip6t_socket");
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