diff options
Diffstat (limited to 'net/netfilter/xt_socket.c')
| -rw-r--r-- | net/netfilter/xt_socket.c | 185 |
1 files changed, 185 insertions, 0 deletions
diff --git a/net/netfilter/xt_socket.c b/net/netfilter/xt_socket.c new file mode 100644 index 0000000..1acc089 --- /dev/null +++ b/net/netfilter/xt_socket.c @@ -0,0 +1,185 @@ +/* + * 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) +{ + unsigned int outside_hdrlen = ip_hdrlen(skb); + struct iphdr *inside_iph, _inside_iph; + struct icmphdr *icmph, _icmph; + __be16 *ports, _ports[2]; + + icmph = skb_header_pointer(skb, outside_hdrlen, + 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_hdrlen + + sizeof(struct icmphdr), + sizeof(_inside_iph), &_inside_iph); + if (inside_iph == NULL) + return 1; + + if (inside_iph->protocol != IPPROTO_TCP && + inside_iph->protocol != IPPROTO_UDP) + return 1; + + ports = skb_header_pointer(skb, outside_hdrlen + + 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 + * its 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 xt_match_param *par) +{ + 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, par->in, false); + if (sk != NULL) { + bool wildcard = (sk->sk_state != TCP_TIME_WAIT && 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, Balazs Scheidler"); +MODULE_DESCRIPTION("x_tables socket match module"); +MODULE_ALIAS("ipt_socket"); |
