Add iptables 'socket' match, which matches packets for which a TCP/UDP
socket lookup succeeds.
Signed-off-by: KOVACS Krisztian <hidden@xxxxxxxxxx>
---
net/netfilter/Kconfig | 15 ++++
net/netfilter/Makefile | 1
net/netfilter/xt_socket.c | 182 +++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 198 insertions(+), 0 deletions(-)
diff --git a/net/netfilter/Kconfig b/net/netfilter/Kconfig
index ff1b0e6..a4b8006 100644
--- a/net/netfilter/Kconfig
+++ b/net/netfilter/Kconfig
@@ -760,6 +760,21 @@ config NETFILTER_XT_MATCH_SCTP
If you want to compile it as a module, say M here and read
<file:Documentation/kbuild/modules.txt>. If unsure, say `N'.
+config NETFILTER_XT_MATCH_SOCKET
+ tristate '"socket" match support (EXPERIMENTAL)'
+ depends on EXPERIMENTAL
+ depends on NETFILTER_TPROXY
+ depends on NETFILTER_XTABLES
+ depends on NETFILTER_ADVANCED
+ select NF_DEFRAG_IPV4
+ help
+ This option adds a `socket' match, which can be used to match
+ packets for which a TCP or UDP socket lookup finds a valid socket.
+ It can be used in combination with the MARK target and policy
+ routing to implement full featured non-locally bound sockets.
+
+ To compile it as a module, choose M here. If unsure, say N.
+
config NETFILTER_XT_MATCH_STATE
tristate '"state" match support'
depends on NETFILTER_XTABLES
diff --git a/net/netfilter/Makefile b/net/netfilter/Makefile
index 1b8cb7f..c386755 100644
--- a/net/netfilter/Makefile
+++ b/net/netfilter/Makefile
@@ -80,6 +80,7 @@ obj-$(CONFIG_NETFILTER_XT_MATCH_QUOTA) += xt_quota.o
obj-$(CONFIG_NETFILTER_XT_MATCH_RATEEST) += xt_rateest.o
obj-$(CONFIG_NETFILTER_XT_MATCH_REALM) += xt_realm.o
obj-$(CONFIG_NETFILTER_XT_MATCH_SCTP) += xt_sctp.o
+obj-$(CONFIG_NETFILTER_XT_MATCH_SOCKET) += xt_socket.o
obj-$(CONFIG_NETFILTER_XT_MATCH_STATE) += xt_state.o
obj-$(CONFIG_NETFILTER_XT_MATCH_STATISTIC) += xt_statistic.o
obj-$(CONFIG_NETFILTER_XT_MATCH_STRING) += xt_string.o
diff --git a/net/netfilter/xt_socket.c b/net/netfilter/xt_socket.c
new file mode 100644
index 0000000..b726c99
--- /dev/null
+++ b/net/netfilter/xt_socket.c
@@ -0,0 +1,182 @@
+/*
+ * Transparent proxy support for Linux/iptables
+ *
+ * Copyright (C) 2007-2008 BalaBit IT Ltd.
+ * Author: 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.
+ *
+ */
+
+#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/nf_tproxy_core.h>
+#include <net/netfilter/ipv4/nf_defrag_ipv4.h>
+
+#if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
+#define XT_SOCKET_HAVE_CONNTRACK 1
+#include <net/netfilter/nf_conntrack.h>
+#endif
+
+static int
+extract_icmp_fields(const struct sk_buff *skb,
+ u8 *protocol,
+ __be32 *raddr,
+ __be32 *laddr,
+ __be16 *rport,
+ __be16 *lport)
+{
+ struct iphdr *outside_iph = ip_hdr(skb);
+ struct iphdr *inside_iph, _inside_iph;
+ struct icmphdr *icmph, _icmph;
+ __be16 *ports, _ports[2];
+
+ icmph = skb_header_pointer(skb, outside_iph->ihl << 2, sizeof(_icmph), &_icmph);
+ if (icmph == NULL)
+ return 1;
+
+ switch (icmph->type) {
+ case ICMP_DEST_UNREACH:
+ case ICMP_SOURCE_QUENCH:
+ case ICMP_REDIRECT:
+ case ICMP_TIME_EXCEEDED:
+ case ICMP_PARAMETERPROB:
+ break;
+ default:
+ return 1;
+ }
+
+ inside_iph = skb_header_pointer(skb, (outside_iph->ihl << 2) + sizeof(struct icmphdr), sizeof(_inside_iph), &_inside_iph);
+ if (inside_iph == NULL)
+ return -EINVAL;
+
+ if (inside_iph->protocol != IPPROTO_TCP &&
+ inside_iph->protocol != IPPROTO_UDP)
+ return 1;
+
+ ports = skb_header_pointer(skb, (outside_iph->ihl << 2) + sizeof(struct icmphdr) + (inside_iph->ihl << 2), sizeof(_ports), &_ports);
+ if (ports == NULL)
+ return 1;
+
+ /* the inside IP packet is the one quoted from our side, thus it saddr is the local address */
+ *protocol = inside_iph->protocol;
+ *laddr = inside_iph->saddr;
+ *lport = ports[0];
+ *raddr = inside_iph->daddr;
+ *rport = ports[1];
+
+ return 0;
+}
+
+
+static bool
+socket_mt(const struct sk_buff *skb,
+ const struct net_device *in,
+ const struct net_device *out,
+ const struct xt_match *match,
+ const void *matchinfo,
+ int offset,
+ unsigned int protoff,
+ bool *hotdrop)
+{
+ const struct iphdr *iph = ip_hdr(skb);
+ struct udphdr _hdr, *hp = NULL;
+ struct sock *sk;
+ __be32 daddr, saddr;
+ __be16 dport, sport;
+ u8 protocol;
+#ifdef XT_SOCKET_HAVE_CONNTRACK
+ struct nf_conn const *ct;
+ enum ip_conntrack_info ctinfo;
+#endif
+
+ if (iph->protocol == IPPROTO_UDP || iph->protocol == IPPROTO_TCP) {
+ hp = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(_hdr), &_hdr);
+ if (hp == NULL)
+ return false;
+
+ protocol = iph->protocol;
+ saddr = iph->saddr;
+ sport = hp->source;
+ daddr = iph->daddr;
+ dport = hp->dest;
+
+ }
+ else if (iph->protocol == IPPROTO_ICMP) {
+ if (extract_icmp_fields(skb, &protocol, &saddr, &daddr, &sport, &dport))
+ return false;
+ }
+ else {
+ return false;
+ }
+
+#ifdef XT_SOCKET_HAVE_CONNTRACK
+ /* Do the lookup with the original socket address in case this is a
+ * reply packet of an established SNAT-ted connection. */
+
+ ct = nf_ct_get(skb, &ctinfo);
+ if (ct && (ct != &nf_conntrack_untracked) &&
+ ((iph->protocol != IPPROTO_ICMP && ctinfo == IP_CT_IS_REPLY + IP_CT_ESTABLISHED) ||
+ (iph->protocol == IPPROTO_ICMP && ctinfo == IP_CT_IS_REPLY + IP_CT_RELATED)) &&
+ (ct->status & IPS_SRC_NAT_DONE)) {
+
+ daddr = ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip;
+ dport = (iph->protocol == IPPROTO_TCP) ?
+ ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u.tcp.port :
+ ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u.udp.port;
+ }
+#endif
+
+ sk = nf_tproxy_get_sock_v4(dev_net(skb->dev), protocol,
+ saddr, daddr, sport, dport, in, false);
+ if (sk != NULL) {
+ bool wildcard = (inet_sk(sk)->rcv_saddr == 0);
+
+ nf_tproxy_put_sock(sk);
+ if (wildcard)
+ sk = NULL;
+ }
+
+ pr_debug("socket match: proto %u %08x:%u -> %08x:%u (orig %08x:%u) sock %p\n",
+ protocol, ntohl(saddr), ntohs(sport),
+ ntohl(daddr), ntohs(dport),
+ ntohl(iph->daddr), hp ? ntohs(hp->dest) : 0, sk);
+
+ return (sk != NULL);
+}
+
+static struct xt_match socket_mt_reg __read_mostly = {
+ .name = "socket",
+ .family = AF_INET,
+ .match = socket_mt,
+ .hooks = 1 << NF_INET_PRE_ROUTING,
+ .me = THIS_MODULE,
+};
+
+static int __init socket_mt_init(void)
+{
+ nf_defrag_ipv4_enable();
+ return xt_register_match(&socket_mt_reg);
+}
+
+static void __exit socket_mt_exit(void)
+{
+ xt_unregister_match(&socket_mt_reg);
+}
+
+module_init(socket_mt_init);
+module_exit(socket_mt_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Krisztian Kovacs");
+MODULE_DESCRIPTION("x_tables socket match module");
+MODULE_ALIAS("ipt_socket");
--
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