[NETFILTER]: x_tables: unify IPv4/IPv6 esp match

This unifies ipt_esp and ip6t_esp to xt_esp. Please note that now
a user program needs to specify IPPROTO_ESP as protocol to use esp match
with IPv6. This means that ip6tables requires '-p esp' like iptables.

Signed-off-by: Yasuyuki Kozakai <yasuyuki.kozakai@toshiba.co.jp>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 146 insertions, 0 deletions

diff --git a/net/netfilter/Kconfig b/net/netfilter/Kconfig
index 332acb3..5fe5189 100644
--- a/net/netfilter/Kconfig
+++ b/net/netfilter/Kconfig
@@ -231,6 +231,15 @@ config NETFILTER_XT_MATCH_DCCP
 	  If you want to compile it as a module, say M here and read
 	  <file:Documentation/modules.txt>.  If unsure, say `N'.
 
+config NETFILTER_XT_MATCH_ESP
+	tristate '"ESP" match support'
+	depends on NETFILTER_XTABLES
+	help
+	  This match extension allows you to match a range of SPIs
+	  inside ESP header of IPSec packets.
+
+	  To compile it as a module, choose M here.  If unsure, say N.
+
 config NETFILTER_XT_MATCH_HELPER
 	tristate '"helper" match support'
 	depends on NETFILTER_XTABLES
diff --git a/net/netfilter/Makefile b/net/netfilter/Makefile
index 9558727..8f02486 100644
--- a/net/netfilter/Makefile
+++ b/net/netfilter/Makefile
@@ -35,6 +35,7 @@ obj-$(CONFIG_NETFILTER_XT_MATCH_CONNBYTES) += xt_connbytes.o
 obj-$(CONFIG_NETFILTER_XT_MATCH_CONNMARK) += xt_connmark.o
 obj-$(CONFIG_NETFILTER_XT_MATCH_CONNTRACK) += xt_conntrack.o
 obj-$(CONFIG_NETFILTER_XT_MATCH_DCCP) += xt_dccp.o
+obj-$(CONFIG_NETFILTER_XT_MATCH_ESP) += xt_esp.o
 obj-$(CONFIG_NETFILTER_XT_MATCH_HELPER) += xt_helper.o
 obj-$(CONFIG_NETFILTER_XT_MATCH_LENGTH) += xt_length.o
 obj-$(CONFIG_NETFILTER_XT_MATCH_LIMIT) += xt_limit.o
diff --git a/net/netfilter/xt_esp.c b/net/netfilter/xt_esp.c
new file mode 100644
index 0000000..9dad628
--- /dev/null
+++ b/net/netfilter/xt_esp.c
@@ -0,0 +1,136 @@
+/* Kernel module to match ESP parameters. */
+
+/* (C) 1999-2000 Yon Uriarte <yon@astaro.de>
+ *
+ * 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/in.h>
+#include <linux/ip.h>
+
+#include <linux/netfilter/xt_esp.h>
+#include <linux/netfilter/x_tables.h>
+
+#include <linux/netfilter_ipv4/ip_tables.h>
+#include <linux/netfilter_ipv6/ip6_tables.h>
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Yon Uriarte <yon@astaro.de>");
+MODULE_DESCRIPTION("x_tables ESP SPI match module");
+MODULE_ALIAS("ipt_esp");
+MODULE_ALIAS("ip6t_esp");
+
+#if 0
+#define duprintf(format, args...) printk(format , ## args)
+#else
+#define duprintf(format, args...)
+#endif
+
+/* Returns 1 if the spi is matched by the range, 0 otherwise */
+static inline int
+spi_match(u_int32_t min, u_int32_t max, u_int32_t spi, int invert)
+{
+	int r = 0;
+	duprintf("esp spi_match:%c 0x%x <= 0x%x <= 0x%x", invert ? '!' : ' ',
+		 min, spi, max);
+	r = (spi >= min && spi <= max) ^ invert;
+	duprintf(" result %s\n", r ? "PASS" : "FAILED");
+	return r;
+}
+
+static int
+match(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,
+      int *hotdrop)
+{
+	struct ip_esp_hdr _esp, *eh;
+	const struct xt_esp *espinfo = matchinfo;
+
+	/* Must not be a fragment. */
+	if (offset)
+		return 0;
+
+	eh = skb_header_pointer(skb, protoff, sizeof(_esp), &_esp);
+	if (eh == NULL) {
+		/* We've been asked to examine this packet, and we
+		 * can't.  Hence, no choice but to drop.
+		 */
+		duprintf("Dropping evil ESP tinygram.\n");
+		*hotdrop = 1;
+		return 0;
+	}
+
+	return spi_match(espinfo->spis[0], espinfo->spis[1], ntohl(eh->spi),
+			 !!(espinfo->invflags & XT_ESP_INV_SPI));
+}
+
+/* Called when user tries to insert an entry of this type. */
+static int
+checkentry(const char *tablename,
+	   const void *ip_void,
+	   const struct xt_match *match,
+	   void *matchinfo,
+	   unsigned int matchinfosize,
+	   unsigned int hook_mask)
+{
+	const struct xt_esp *espinfo = matchinfo;
+
+	if (espinfo->invflags & ~XT_ESP_INV_MASK) {
+		duprintf("xt_esp: unknown flags %X\n", espinfo->invflags);
+		return 0;
+	}
+
+	return 1;
+}
+
+static struct xt_match esp_match = {
+	.name		= "esp",
+	.family		= AF_INET,
+	.proto		= IPPROTO_ESP,
+	.match		= &match,
+	.matchsize	= sizeof(struct xt_esp),
+	.checkentry	= &checkentry,
+	.me		= THIS_MODULE,
+};
+
+static struct xt_match esp6_match = {
+	.name		= "esp",
+	.family		= AF_INET6,
+	.proto		= IPPROTO_ESP,
+	.match		= &match,
+	.matchsize	= sizeof(struct xt_esp),
+	.checkentry	= &checkentry,
+	.me		= THIS_MODULE,
+};
+
+static int __init xt_esp_init(void)
+{
+	int ret;
+	ret = xt_register_match(&esp_match);
+	if (ret)
+		return ret;
+
+	ret = xt_register_match(&esp6_match);
+	if (ret)
+		xt_unregister_match(&esp_match);
+
+	return ret;
+}
+
+static void __exit xt_esp_cleanup(void)
+{
+	xt_unregister_match(&esp_match);
+	xt_unregister_match(&esp6_match);
+}
+
+module_init(xt_esp_init);
+module_exit(xt_esp_cleanup);