diff options
Diffstat (limited to 'net/netfilter/xt_socket.c')
-rw-r--r-- | net/netfilter/xt_socket.c | 336 |
1 files changed, 336 insertions, 0 deletions
diff --git a/net/netfilter/xt_socket.c b/net/netfilter/xt_socket.c new file mode 100644 index 000000000..76e01f292 --- /dev/null +++ b/net/netfilter/xt_socket.c @@ -0,0 +1,336 @@ +// 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 = READ_ONCE(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 = READ_ONCE(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 void socket_mt_destroy(const struct xt_mtdtor_param *par) +{ + if (par->family == NFPROTO_IPV4) + nf_defrag_ipv4_disable(par->net); +#if IS_ENABLED(CONFIG_IP6_NF_IPTABLES) + else if (par->family == NFPROTO_IPV6) + nf_defrag_ipv6_disable(par->net); +#endif +} + +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, + .destroy = socket_mt_destroy, + .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), + .destroy = socket_mt_destroy, + .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, + .destroy = socket_mt_destroy, + .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, + .destroy = socket_mt_destroy, + .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, + .destroy = socket_mt_destroy, + .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, + .destroy = socket_mt_destroy, + .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"); |