[NETFILTER]: Add SANE connection tracking helper

This is nf_conntrack_sane, a netfilter connection tracking helper module
for the SANE protocol used by the 'saned' daemon to make scanners available
via network. The SANE protocol uses separate control & data connections,
similar to passive FTP. The helper module is needed to recognize the data
connection as RELATED to the control one.

Signed-off-by: Michal Schmidt <mschmidt@redhat.com>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/linux/netfilter/nf_conntrack_sane.h b/include/linux/netfilter/nf_conntrack_sane.h
new file mode 100644 (file)
index 0000000..4767d6e
--- /dev/null
+++ b/include/linux/netfilter/nf_conntrack_sane.h
@@ -0,0 +1,21 @@
+#ifndef _NF_CONNTRACK_SANE_H
+#define _NF_CONNTRACK_SANE_H
+/* SANE tracking. */
+
+#ifdef __KERNEL__
+
+#define SANE_PORT      6566
+
+enum sane_state {
+       SANE_STATE_NORMAL,
+       SANE_STATE_START_REQUESTED,
+};
+
+/* This structure exists only once per master */
+struct nf_ct_sane_master {
+       enum sane_state state;
+};
+
+#endif /* __KERNEL__ */
+
+#endif /* _NF_CONNTRACK_SANE_H */

diff --git a/include/net/netfilter/nf_conntrack.h b/include/net/netfilter/nf_conntrack.h
index bd01b4633ee20138dc6681b2e15dd2e7cabc471c..68ec27490c2075d7fb342bc264b0ae6db2444bc1 100644 (file)
--- a/include/net/netfilter/nf_conntrack.h
+++ b/include/net/netfilter/nf_conntrack.h
@@ -45,6 +45,7 @@ union nf_conntrack_expect_proto {
 #include <linux/netfilter/nf_conntrack_ftp.h>
 #include <linux/netfilter/nf_conntrack_pptp.h>
 #include <linux/netfilter/nf_conntrack_h323.h>
+#include <linux/netfilter/nf_conntrack_sane.h>
 
 /* per conntrack: application helper private data */
 union nf_conntrack_help {
@@ -52,6 +53,7 @@ union nf_conntrack_help {
        struct nf_ct_ftp_master ct_ftp_info;
        struct nf_ct_pptp_master ct_pptp_info;
        struct nf_ct_h323_master ct_h323_info;
+       struct nf_ct_sane_master ct_sane_info;
 };
 
 #include <linux/types.h>

diff --git a/net/netfilter/Kconfig b/net/netfilter/Kconfig
index 80107d4909c5b88fb69c519ea7f4301b93bb63c0..614c92c178355c6a1a610fc6e10f01cd681172e2 100644 (file)
--- a/net/netfilter/Kconfig
+++ b/net/netfilter/Kconfig
@@ -235,6 +235,19 @@ config NF_CONNTRACK_PPTP
 
          To compile it as a module, choose M here.  If unsure, say N.
 
+config NF_CONNTRACK_SANE
+       tristate "SANE protocol support (EXPERIMENTAL)"
+       depends on EXPERIMENTAL && NF_CONNTRACK
+       help
+         SANE is a protocol for remote access to scanners as implemented
+         by the 'saned' daemon. Like FTP, it uses separate control and
+         data connections.
+
+         With this module you can support SANE on a connection tracking
+         firewall.
+
+         To compile it as a module, choose M here.  If unsure, say N.
+
 config NF_CONNTRACK_SIP
        tristate "SIP protocol support (EXPERIMENTAL)"
        depends on EXPERIMENTAL && NF_CONNTRACK

diff --git a/net/netfilter/Makefile b/net/netfilter/Makefile
index 5dc5574f7e99ea79be21c416405aad456622659e..5054b0ff809614d045d2e6b05ca10daced2c9779 100644 (file)
--- a/net/netfilter/Makefile
+++ b/net/netfilter/Makefile
@@ -29,6 +29,7 @@ obj-$(CONFIG_NF_CONNTRACK_H323) += nf_conntrack_h323.o
 obj-$(CONFIG_NF_CONNTRACK_IRC) += nf_conntrack_irc.o
 obj-$(CONFIG_NF_CONNTRACK_NETBIOS_NS) += nf_conntrack_netbios_ns.o
 obj-$(CONFIG_NF_CONNTRACK_PPTP) += nf_conntrack_pptp.o
+obj-$(CONFIG_NF_CONNTRACK_SANE) += nf_conntrack_sane.o
 obj-$(CONFIG_NF_CONNTRACK_SIP) += nf_conntrack_sip.o
 obj-$(CONFIG_NF_CONNTRACK_TFTP) += nf_conntrack_tftp.o
 

diff --git a/net/netfilter/nf_conntrack_sane.c b/net/netfilter/nf_conntrack_sane.c
new file mode 100644 (file)
index 0000000..eb2d1dc
--- /dev/null
+++ b/net/netfilter/nf_conntrack_sane.c
@@ -0,0 +1,242 @@
+/* SANE connection tracking helper
+ * (SANE = Scanner Access Now Easy)
+ * For documentation about the SANE network protocol see
+ * http://www.sane-project.org/html/doc015.html
+ */
+
+/* Copyright (C) 2007 Red Hat, Inc.
+ * Author: Michal Schmidt <mschmidt@redhat.com>
+ * Based on the FTP conntrack helper (net/netfilter/nf_conntrack_ftp.c):
+ *  (C) 1999-2001 Paul `Rusty' Russell
+ *  (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
+ *  (C) 2003,2004 USAGI/WIDE Project <http://www.linux-ipv6.org>
+ *  (C) 2003 Yasuyuki Kozakai @USAGI <yasuyuki.kozakai@toshiba.co.jp>
+ *
+ * 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/moduleparam.h>
+#include <linux/netfilter.h>
+#include <linux/in.h>
+#include <linux/tcp.h>
+#include <net/netfilter/nf_conntrack.h>
+#include <net/netfilter/nf_conntrack_helper.h>
+#include <net/netfilter/nf_conntrack_expect.h>
+#include <linux/netfilter/nf_conntrack_sane.h>
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Michal Schmidt <mschmidt@redhat.com>");
+MODULE_DESCRIPTION("SANE connection tracking helper");
+
+static char *sane_buffer;
+
+static DEFINE_SPINLOCK(nf_sane_lock);
+
+#define MAX_PORTS 8
+static u_int16_t ports[MAX_PORTS];
+static unsigned int ports_c;
+module_param_array(ports, ushort, &ports_c, 0400);
+
+#if 0
+#define DEBUGP printk
+#else
+#define DEBUGP(format, args...)
+#endif
+
+struct sane_request {
+       __be32 RPC_code;
+#define SANE_NET_START      7   /* RPC code */
+
+       __be32 handle;
+};
+
+struct sane_reply_net_start {
+       __be32 status;
+#define SANE_STATUS_SUCCESS 0
+
+       __be16 zero;
+       __be16 port;
+       /* other fields aren't interesting for conntrack */
+};
+
+static int help(struct sk_buff **pskb,
+               unsigned int protoff,
+               struct nf_conn *ct,
+               enum ip_conntrack_info ctinfo)
+{
+       unsigned int dataoff, datalen;
+       struct tcphdr _tcph, *th;
+       char *sb_ptr;
+       int ret = NF_ACCEPT;
+       int dir = CTINFO2DIR(ctinfo);
+       struct nf_ct_sane_master *ct_sane_info;
+       struct nf_conntrack_expect *exp;
+       struct nf_conntrack_tuple *tuple;
+       struct sane_request *req;
+       struct sane_reply_net_start *reply;
+       int family = ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.l3num;
+
+       ct_sane_info = &nfct_help(ct)->help.ct_sane_info;
+       /* Until there's been traffic both ways, don't look in packets. */
+       if (ctinfo != IP_CT_ESTABLISHED &&
+           ctinfo != IP_CT_ESTABLISHED+IP_CT_IS_REPLY)
+               return NF_ACCEPT;
+
+       /* Not a full tcp header? */
+       th = skb_header_pointer(*pskb, protoff, sizeof(_tcph), &_tcph);
+       if (th == NULL)
+               return NF_ACCEPT;
+
+       /* No data? */
+       dataoff = protoff + th->doff * 4;
+       if (dataoff >= (*pskb)->len)
+               return NF_ACCEPT;
+
+       datalen = (*pskb)->len - dataoff;
+
+       spin_lock_bh(&nf_sane_lock);
+       sb_ptr = skb_header_pointer(*pskb, dataoff, datalen, sane_buffer);
+       BUG_ON(sb_ptr == NULL);
+
+       if (dir == IP_CT_DIR_ORIGINAL) {
+               if (datalen != sizeof(struct sane_request))
+                       goto out;
+
+               req = (struct sane_request *)sb_ptr;
+               if (req->RPC_code != htonl(SANE_NET_START)) {
+                       /* Not an interesting command */
+                       ct_sane_info->state = SANE_STATE_NORMAL;
+                       goto out;
+               }
+
+               /* We're interested in the next reply */
+               ct_sane_info->state = SANE_STATE_START_REQUESTED;
+               goto out;
+       }
+
+       /* Is it a reply to an uninteresting command? */
+       if (ct_sane_info->state != SANE_STATE_START_REQUESTED)
+               goto out;
+
+       /* It's a reply to SANE_NET_START. */
+       ct_sane_info->state = SANE_STATE_NORMAL;
+
+       if (datalen < sizeof(struct sane_reply_net_start)) {
+               DEBUGP("nf_ct_sane: NET_START reply too short\n");
+               goto out;
+       }
+
+       reply = (struct sane_reply_net_start *)sb_ptr;
+       if (reply->status != htonl(SANE_STATUS_SUCCESS)) {
+               /* saned refused the command */
+               DEBUGP("nf_ct_sane: unsuccessful SANE_STATUS = %u\n",
+                       ntohl(reply->status));
+               goto out;
+       }
+
+       /* Invalid saned reply? Ignore it. */
+       if (reply->zero != 0)
+               goto out;
+
+       exp = nf_conntrack_expect_alloc(ct);
+       if (exp == NULL) {
+               ret = NF_DROP;
+               goto out;
+       }
+
+       tuple = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple;
+       nf_conntrack_expect_init(exp, family,
+                                &tuple->src.u3, &tuple->dst.u3,
+                                IPPROTO_TCP,
+                                NULL, &reply->port);
+
+       DEBUGP("nf_ct_sane: expect: ");
+       NF_CT_DUMP_TUPLE(&exp->tuple);
+       NF_CT_DUMP_TUPLE(&exp->mask);
+
+       /* Can't expect this?  Best to drop packet now. */
+       if (nf_conntrack_expect_related(exp) != 0)
+               ret = NF_DROP;
+
+       nf_conntrack_expect_put(exp);
+
+out:
+       spin_unlock_bh(&nf_sane_lock);
+       return ret;
+}
+
+static struct nf_conntrack_helper sane[MAX_PORTS][2];
+static char sane_names[MAX_PORTS][2][sizeof("sane-65535")];
+
+/* don't make this __exit, since it's called from __init ! */
+static void nf_conntrack_sane_fini(void)
+{
+       int i, j;
+
+       for (i = 0; i < ports_c; i++) {
+               for (j = 0; j < 2; j++) {
+                       DEBUGP("nf_ct_sane: unregistering helper for pf: %d "
+                              "port: %d\n",
+                               sane[i][j].tuple.src.l3num, ports[i]);
+                       nf_conntrack_helper_unregister(&sane[i][j]);
+               }
+       }
+
+       kfree(sane_buffer);
+}
+
+static int __init nf_conntrack_sane_init(void)
+{
+       int i, j = -1, ret = 0;
+       char *tmpname;
+
+       sane_buffer = kmalloc(65536, GFP_KERNEL);
+       if (!sane_buffer)
+               return -ENOMEM;
+
+       if (ports_c == 0)
+               ports[ports_c++] = SANE_PORT;
+
+       /* FIXME should be configurable whether IPv4 and IPv6 connections
+                are tracked or not - YK */
+       for (i = 0; i < ports_c; i++) {
+               sane[i][0].tuple.src.l3num = PF_INET;
+               sane[i][1].tuple.src.l3num = PF_INET6;
+               for (j = 0; j < 2; j++) {
+                       sane[i][j].tuple.src.u.tcp.port = htons(ports[i]);
+                       sane[i][j].tuple.dst.protonum = IPPROTO_TCP;
+                       sane[i][j].mask.src.u.tcp.port = 0xFFFF;
+                       sane[i][j].mask.dst.protonum = 0xFF;
+                       sane[i][j].max_expected = 1;
+                       sane[i][j].timeout = 5 * 60;    /* 5 Minutes */
+                       sane[i][j].me = THIS_MODULE;
+                       sane[i][j].help = help;
+                       tmpname = &sane_names[i][j][0];
+                       if (ports[i] == SANE_PORT)
+                               sprintf(tmpname, "sane");
+                       else
+                               sprintf(tmpname, "sane-%d", ports[i]);
+                       sane[i][j].name = tmpname;
+
+                       DEBUGP("nf_ct_sane: registering helper for pf: %d "
+                              "port: %d\n",
+                               sane[i][j].tuple.src.l3num, ports[i]);
+                       ret = nf_conntrack_helper_register(&sane[i][j]);
+                       if (ret) {
+                               printk(KERN_ERR "nf_ct_sane: failed to "
+                                      "register helper for pf: %d port: %d\n",
+                                       sane[i][j].tuple.src.l3num, ports[i]);
+                               nf_conntrack_sane_fini();
+                               return ret;
+                       }
+               }
+       }
+
+       return 0;
+}
+
+module_init(nf_conntrack_sane_init);
+module_exit(nf_conntrack_sane_fini);