diff options
| -rw-r--r-- | net/ipv4/netfilter/Kconfig | 19 | ||||
| -rw-r--r-- | net/ipv4/netfilter/Makefile | 1 | ||||
| -rw-r--r-- | net/ipv4/netfilter/ip_conntrack_netbios_ns.c | 131 |
3 files changed, 151 insertions, 0 deletions
diff --git a/net/ipv4/netfilter/Kconfig b/net/ipv4/netfilter/Kconfig index e046f55..fd2eb5d 100644 --- a/net/ipv4/netfilter/Kconfig +++ b/net/ipv4/netfilter/Kconfig @@ -85,6 +85,25 @@ config IP_NF_IRC To compile it as a module, choose M here. If unsure, say Y. +config IP_NF_NETBIOS_NS + tristate "NetBIOS name service protocol support (EXPERIMENTAL)" + depends on IP_NF_CONNTRACK && EXPERIMENTAL + help + NetBIOS name service requests are sent as broadcast messages from an + unprivileged port and responded to with unicast messages to the + same port. This make them hard to firewall properly because connection + tracking doesn't deal with broadcasts. This helper tracks locally + originating NetBIOS name service requests and the corresponding + responses. It relies on correct IP address configuration, specifically + netmask and broadcast address. When properly configured, the output + of "ip address show" should look similar to this: + + $ ip -4 address show eth0 + 4: eth0: <BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast qlen 1000 + inet 172.16.2.252/24 brd 172.16.2.255 scope global eth0 + + To compile it as a module, choose M here. If unsure, say N. + config IP_NF_TFTP tristate "TFTP protocol support" depends on IP_NF_CONNTRACK diff --git a/net/ipv4/netfilter/Makefile b/net/ipv4/netfilter/Makefile index a7bd38f..1ba0db7 100644 --- a/net/ipv4/netfilter/Makefile +++ b/net/ipv4/netfilter/Makefile @@ -21,6 +21,7 @@ obj-$(CONFIG_IP_NF_AMANDA) += ip_conntrack_amanda.o obj-$(CONFIG_IP_NF_TFTP) += ip_conntrack_tftp.o obj-$(CONFIG_IP_NF_FTP) += ip_conntrack_ftp.o obj-$(CONFIG_IP_NF_IRC) += ip_conntrack_irc.o +obj-$(CONFIG_IP_NF_NETBIOS_NS) += ip_conntrack_netbios_ns.o # NAT helpers obj-$(CONFIG_IP_NF_NAT_AMANDA) += ip_nat_amanda.o diff --git a/net/ipv4/netfilter/ip_conntrack_netbios_ns.c b/net/ipv4/netfilter/ip_conntrack_netbios_ns.c new file mode 100644 index 0000000..2b5cf9c --- /dev/null +++ b/net/ipv4/netfilter/ip_conntrack_netbios_ns.c @@ -0,0 +1,131 @@ +/* + * NetBIOS name service broadcast connection tracking helper + * + * (c) 2005 Patrick McHardy <kaber@trash.net> + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License + * as published by the Free Software Foundation; either version + * 2 of the License, or (at your option) any later version. + */ +/* + * This helper tracks locally originating NetBIOS name service + * requests by issuing permanent expectations (valid until + * timing out) matching all reply connections from the + * destination network. The only NetBIOS specific thing is + * actually the port number. + */ +#include <linux/kernel.h> +#include <linux/module.h> +#include <linux/init.h> +#include <linux/skbuff.h> +#include <linux/netdevice.h> +#include <linux/inetdevice.h> +#include <linux/in.h> +#include <linux/ip.h> +#include <linux/udp.h> +#include <net/route.h> + +#include <linux/netfilter.h> +#include <linux/netfilter_ipv4.h> +#include <linux/netfilter_ipv4/ip_conntrack.h> +#include <linux/netfilter_ipv4/ip_conntrack_helper.h> + +MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>"); +MODULE_DESCRIPTION("NetBIOS name service broadcast connection tracking helper"); +MODULE_LICENSE("GPL"); + +static unsigned int timeout = 3; +module_param(timeout, int, 0600); +MODULE_PARM_DESC(timeout, "timeout for master connection/replies in seconds"); + +static int help(struct sk_buff **pskb, + struct ip_conntrack *ct, enum ip_conntrack_info ctinfo) +{ + struct ip_conntrack_expect *exp; + struct iphdr *iph = (*pskb)->nh.iph; + struct udphdr _uh, *uh; + struct rtable *rt = (struct rtable *)(*pskb)->dst; + struct in_device *in_dev; + u_int32_t mask = 0; + + /* we're only interested in locally generated packets */ + if ((*pskb)->sk == NULL) + goto out; + if (rt == NULL || !(rt->rt_flags & RTCF_BROADCAST)) + goto out; + if (CTINFO2DIR(ctinfo) != IP_CT_DIR_ORIGINAL) + goto out; + + rcu_read_lock(); + in_dev = __in_dev_get(rt->u.dst.dev); + if (in_dev != NULL) { + for_primary_ifa(in_dev) { + if (ifa->ifa_broadcast == iph->daddr) { + mask = ifa->ifa_mask; + break; + } + } endfor_ifa(in_dev); + } + rcu_read_unlock(); + + if (mask == 0) + goto out; + + uh = skb_header_pointer(*pskb, iph->ihl * 4, sizeof(_uh), &_uh); + BUG_ON(uh == NULL); + + exp = ip_conntrack_expect_alloc(ct); + if (exp == NULL) + goto out; + memset(&exp->tuple, 0, sizeof(exp->tuple)); + exp->tuple.src.ip = iph->daddr & mask; + exp->tuple.dst.ip = iph->saddr; + exp->tuple.dst.u.udp.port = uh->source; + exp->tuple.dst.protonum = IPPROTO_UDP; + + memset(&exp->mask, 0, sizeof(exp->mask)); + exp->mask.src.ip = mask; + exp->mask.dst.ip = 0xFFFFFFFF; + exp->mask.dst.u.udp.port = 0xFFFF; + exp->mask.dst.protonum = 0xFF; + + exp->expectfn = NULL; + exp->flags = IP_CT_EXPECT_PERMANENT; + + ip_conntrack_expect_related(exp); + ip_conntrack_expect_put(exp); + + ip_ct_refresh_acct(ct, ctinfo, NULL, timeout * HZ); +out: + return NF_ACCEPT; +} + +static struct ip_conntrack_helper helper = { + .name = "netbios-ns", + .tuple = { + .src.u.udp.port = __constant_htons(137), + .dst.protonum = IPPROTO_UDP, + }, + .mask = { + .src.u.udp.port = 0xFFFF, + .dst.protonum = 0xFF, + }, + .max_expected = 1, + .me = THIS_MODULE, + .help = help, +}; + +static int __init init(void) +{ + helper.timeout = timeout; + return ip_conntrack_helper_register(&helper); +} + +static void __exit fini(void) +{ + ip_conntrack_helper_unregister(&helper); +} + +module_init(init); +module_exit(fini); |