[NETFILTER]: Add NetBIOS name service helper

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 151 insertions, 0 deletions

diff --git a/net/ipv4/netfilter/Kconfig b/net/ipv4/netfilter/Kconfig
index e046f5521814..fd2eb5d4c7fe 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 a7bd38f50522..1ba0db746817 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 000000000000..2b5cf9c51309
--- /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);