Add a reworked IPv4 options match - xt_ipv4options

This revision 1 of ipv4options makes it possible to match the
presence or absence of any of the 32 possible IP options, either all
or any of the options the user specified.

extensions/Kbuild

@@ -19,6 +19,7 @@ obj-${build_fuzzy}       += xt_fuzzy.o
 obj-${build_geoip}       += xt_geoip.o
 obj-${build_ipp2p}       += xt_ipp2p.o
 obj-${build_ipset}       += ipset/
+obj-${build_ipv4options} += xt_ipv4options.o
 obj-${build_length2}     += xt_length2.o
 obj-${build_lscan}       += xt_lscan.o
 obj-${build_quota2}      += xt_quota2.o

extensions/Mbuild

@@ -12,6 +12,7 @@ obj-${build_fuzzy}       += libxt_fuzzy.so
 obj-${build_geoip}       += libxt_geoip.so
 obj-${build_ipp2p}       += libxt_ipp2p.so
 obj-${build_ipset}       += ipset/
+obj-${build_ipv4options} += libxt_ipv4options.so
 obj-${build_length2}     += libxt_length2.so
 obj-${build_lscan}       += libxt_lscan.so
 obj-${build_quota2}      += libxt_quota2.so

extensions/libxt_ipv4options.c

@@ -0,0 +1,177 @@
+/*
+ *	"ipv4options" match extension for iptables
+ *	Coprygith © Jan Engelhardt, 2009
+ *
+ *	This program is free software; you can redistribute it and/or
+ *	modify it under the terms of the GNU General Public License; either
+ *	version 2 of the License, or any later version, as published by the
+ *	Free Software Foundation.
+ */
+#include <getopt.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <string.h>
+#include <xtables.h>
+#include "xt_ipv4options.h"
+
+/*
+ * Overview from http://www.networksorcery.com/enp/protocol/ip.htm
+ * Not providing strings for options that seem to be most distant in the past.
+ */
+static const char *const v4opt_names[32] = {
+	[ 1] = "nop",
+	[ 2] = "security",     /* RFC 1108 */
+	[ 3] = "lsrr",         /* RFC 791 */
+	[ 4] = "timestamp",    /* RFC 781, 791 */
+	[ 7] = "record-route", /* RFC 791 */
+	[ 9] = "ssrr",         /* RFC 791 */
+	[11] = "mtu-probe",    /* RFC 1063 */
+	[12] = "mtu-reply",    /* RFC 1063 */
+	[18] = "traceroute",   /* RFC 1393 */
+	[20] = "router-alert", /* RFC 2113 */
+};
+
+static void ipv4options_mt_help(void)
+{
+	printf(
+"ipv4options match options:\n"
+"--flags [!]symbol[,...]    Match presence/absence (!) of option\n"
+"                           (either by name or number)\n"
+"--any                      Interpret --flags as OR-combined\n\n");
+}
+
+static const struct option ipv4options_mt_opts[] = {
+	{.name = "flags", .has_arg = true,  .val = 'f'},
+	{.name = "any",   .has_arg = false, .val = 'a'},
+	{NULL},
+};
+
+static void ipv4options_parse_flagspec(struct xt_ipv4options_mtinfo1 *info,
+    char *arg)
+{
+	unsigned int i, opt;
+	bool inv;
+	char *p;
+
+	while (true) {
+		p = strchr(arg, ',');
+		if (p != NULL)
+			*p = '\0';
+
+		inv = false;
+		opt = 0;
+		if (*arg == '!') {
+			inv = true;
+			++arg;
+		}
+
+		for (i = 1; i < 32;++i)
+			if (v4opt_names[i] != NULL &&
+			    strcmp(v4opt_names[i], arg) == 0) {
+				opt = i;
+				break;
+			}
+
+		if (opt == 0 &&
+		    !strtonum(arg, NULL, &opt, 0, UINT8_MAX))
+			exit_error(PARAMETER_PROBLEM,
+				"ipv4options: Bad option value \"%s\"", arg);
+
+		if (opt == 0)
+			exit_error(PARAMETER_PROBLEM,
+				"ipv4options: Option value may not be zero");
+
+		info->map |= (1 << opt);
+		if (inv)
+			info->invert |= (1 << opt);
+		if (p == NULL)
+			break;
+		arg = p + 1;
+	}
+}
+
+static int ipv4options_mt_parse(int c, char **argv, int invert,
+    unsigned int *flags, const void *entry, struct xt_entry_match **match)
+{
+	struct xt_ipv4options_mtinfo1 *info = (void *)(*match)->data;
+
+	switch (c) {
+	case 'a': /* --any */
+		param_act(P_NO_INVERT, "ipv4options", "--any", invert);
+		info->flags |= XT_V4OPTS_ANY;
+		return true;
+	case 'f': /* --flags */
+		param_act(P_NO_INVERT, "ipv4options", "--flags", invert);
+		ipv4options_parse_flagspec(info, optarg);
+		return true;
+	}
+
+	return false;
+}
+
+/* no checking of *flags - no IPv4 options is also valid */
+
+static void ipv4options_print_flags(const struct xt_ipv4options_mtinfo1 *info,
+    bool numeric)
+{
+	uint32_t tmp = info->map;
+	unsigned int i;
+
+	for (i = 1; i < 32; ++i)
+		if (tmp & (1 << i)) {
+			if (info->invert & (1 << i))
+				printf("!");
+			if (!numeric && v4opt_names[i] != NULL)
+				printf("%s", v4opt_names[i]);
+			else
+				printf("%u", i);
+			tmp &= ~(1 << i);
+			if (tmp)
+				printf(",");
+		}
+}
+
+static void ipv4options_mt_print(const void *ip,
+    const struct xt_entry_match *match, int numeric)
+{
+	const struct xt_ipv4options_mtinfo1 *info = (void *)match->data;
+
+	printf("ipv4options %s ",
+	       (info->flags & XT_V4OPTS_ANY) ? "any-of" : "all-of");
+	ipv4options_print_flags(info, numeric);
+	printf(" ");
+}
+
+static void ipv4options_mt_save(const void *ip,
+    const struct xt_entry_match *match)
+{
+	const struct xt_ipv4options_mtinfo1 *info = (void *)match->data;
+
+	if (info->map != 0) {
+		printf("--flags ");
+		ipv4options_print_flags(info, true);
+	}
+	if (info->flags & XT_V4OPTS_ANY)
+		printf(" --any");
+	printf(" ");
+}
+
+static struct xtables_match ipv4options_mt_reg = {
+	.version       = XTABLES_VERSION,
+	.name          = "ipv4options",
+	.revision      = 1,
+	.family        = PF_INET,
+	.size          = XT_ALIGN(sizeof(struct xt_ipv4options_mtinfo1)),
+	.userspacesize = XT_ALIGN(sizeof(struct xt_ipv4options_mtinfo1)),
+	.help          = ipv4options_mt_help,
+	.parse         = ipv4options_mt_parse,
+	.print         = ipv4options_mt_print,
+	.save          = ipv4options_mt_save,
+	.extra_opts    = ipv4options_mt_opts,
+};
+
+static __attribute__((constructor)) void ipv4options_mt_ldr(void)
+{
+	xtables_register_match(&ipv4options_mt_reg);
+}

extensions/xt_ipv4options.c

@@ -0,0 +1,72 @@
+/*
+ *	xt_ipv4opts - Netfilter module to match IPv4 options
+ *	Copyright © Jan Engelhardt, 2009
+ *
+ *	This program is free software; you can redistribute it and/or
+ *	modify it under the terms of the GNU General Public License; either
+ *	version 2 of the License, or any later version, as published by the
+ *	Free Software Foundation.
+ */
+#include <linux/ip.h>
+#include <linux/module.h>
+#include <linux/skbuff.h>
+#include <linux/netfilter/x_tables.h>
+#include <net/ip.h>
+#include "xt_ipv4options.h"
+#include "compat_xtables.h"
+
+static uint32_t ipv4options_rd(const uint8_t *data, int len)
+{
+	uint32_t opts = 0;
+
+	while (len >= 2) {
+		opts |= 1 << (data[0] & 0x1F);
+		len  -= data[1];
+		data += data[1];
+	}
+
+	return opts;
+}
+
+static bool ipv4options_mt(const struct sk_buff *skb,
+    const struct xt_match_param *par)
+{
+	const struct xt_ipv4options_mtinfo1 *info = par->matchinfo;
+	const struct iphdr *iph = ip_hdr(skb);
+	uint32_t opts = 0;
+	uint16_t len  = ip_hdrlen(skb) - sizeof(struct iphdr);
+
+	if (len > 0)
+		opts = ipv4options_rd((const void *)iph +
+		       sizeof(struct iphdr), len);
+
+	opts ^= info->invert;
+	opts &= info->map;
+	return (info->flags & XT_V4OPTS_ANY) ? opts : opts == info->map;
+}
+
+static struct xt_match ipv4options_mt_reg __read_mostly = {
+	.name      = "ipv4options",
+	.revision  = 1,
+	.family    = NFPROTO_IPV4,
+	.match     = ipv4options_mt,
+	.matchsize = XT_ALIGN(sizeof(struct xt_ipv4options_mtinfo1)),
+	.me        = THIS_MODULE,
+};
+
+static int __init ipv4options_mt_init(void)
+{
+	return xt_register_match(&ipv4options_mt_reg);
+}
+
+static void __exit ipv4options_mt_exit(void)
+{
+	xt_unregister_match(&ipv4options_mt_reg);
+}
+
+MODULE_DESCRIPTION("Xatblse: IPv4 option match");
+MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("ipt_ipv4options");
+module_init(ipv4options_mt_init);
+module_exit(ipv4options_mt_exit);

extensions/xt_ipv4options.h

@@ -0,0 +1,26 @@
+#ifndef _LINUX_NETFILTER_XT_IPV4OPTIONS_H
+#define _LINUX_NETFILTER_XT_IPV4OPTIONS_H 1
+
+/* IPv4 allows for a 5-bit option number - 32 options */
+
+/**
+ * %XT_V4OPTS_ALL:	all options in @map must be present (respecting @invert)
+ * %XT_V4OPTS_ANY:	any of the option in @map
+ */
+enum xt_ipv4options_flags {
+	XT_V4OPTS_ALL = 1 << 0,
+	XT_V4OPTS_ANY = 1 << 1,
+};
+
+/**
+ * @map:	bitmask of options that should appear
+ * @invert:	inversion map
+ * @flags:	see above
+ */
+struct xt_ipv4options_mtinfo1 {
+	__u32 map;
+	__u32 invert;
+	__u8 flags;
+};
+
+#endif /* _LINUX_NETFILTER_XT_IPV4OPTIONS_H */

mconfig

@@ -14,6 +14,7 @@ build_fuzzy=m
 build_geoip=m
 build_ipp2p=m
 build_ipset=m
+build_ipv4options=m
 build_length2=m
 build_lscan=m
 build_quota2=m