add passive OS fingerprinting (Evgeniy Polyakov)

diff --git a/extensions/.osf-test b/extensions/.osf-test
new file mode 100755 (executable)
index 0000000..bc3ad8f
--- /dev/null
+++ b/extensions/.osf-test
@@ -0,0 +1,3 @@
+#!/bin/sh
+# True if osf is applied.
+[ -f $KERNEL_DIR/include/linux/netfilter_ipv4/ipt_osf.h ] && echo osf

diff --git a/extensions/libipt_osf.c b/extensions/libipt_osf.c
new file mode 100644 (file)
index 0000000..1bef9de
--- /dev/null
+++ b/extensions/libipt_osf.c
@@ -0,0 +1,126 @@
+/*
+ * libipt_osf.c
+ *
+ * Copyright (c) 2003 Evgeniy Polyakov <johnpol@2ka.mipt.ru>
+ *
+ *
+ * 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 program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ */
+
+/*
+ * iptables interface for OS fingerprint matching module.
+ */
+
+#include <stdio.h>
+#include <netdb.h>
+#include <string.h>
+#include <stdlib.h>
+#include <getopt.h>
+#include <ctype.h>
+
+#include <iptables.h>
+#include <linux/netfilter_ipv4/ipt_osf.h>
+
+static void help(void)
+{
+       printf("OS fingerprint match v%s options:\n"
+               "  --genre [!] string          Match a OS genre bypassive fingerprinting.\n"
+               "                              Genres: Linux, FreeBSD, NetBSD, OpenBSD,\n"
+               "                                      Windows\n",
+               IPTABLES_VERSION);
+}
+
+
+static struct option opts[] = {
+       { .name = "genre",     .has_arg = 1, .flag = 0, .val = '1' },
+       { .name = 0 }
+};
+
+
+static void init(struct ipt_entry_match *m, unsigned int *nfcache)
+{
+       *nfcache |= NFC_UNKNOWN;
+}
+
+
+static void parse_string(const unsigned char *s, struct ipt_osf_info *info)
+{
+       if (strlen(s) < MAXGENRELEN) 
+               strcpy(info->genre, s);
+       else 
+               exit_error(PARAMETER_PROBLEM, "Genre string too long `%s' [%d], max=%d", 
+                               s, strlen(s), MAXGENRELEN);
+}
+
+static int parse(int c, char **argv, int invert, unsigned int *flags,
+                       const struct ipt_entry *entry,
+                       unsigned int *nfcache,
+                       struct ipt_entry_match **match)
+{
+       struct ipt_osf_info *info = (struct ipt_osf_info *)(*match)->data;
+
+       if (*flags)
+               exit_error(PARAMETER_PROBLEM, "Can't specify multiple strings");
+
+       check_inverse(optarg, &invert, &optind, 0);
+       parse_string(optarg, info);
+       if (invert)
+               info->invert = 1;
+       info->len=strlen((char *)info->genre);
+       *flags = 1;
+
+       return 1;
+}
+
+static void final_check(unsigned int flags)
+{
+       if (!flags)
+               exit_error(PARAMETER_PROBLEM, "OS fingerprint match: You must specify `--genre'");
+}
+
+static void print(const struct ipt_ip *ip, const struct ipt_entry_match *match, int numeric)
+{
+       const struct ipt_osf_info *info = (const struct ipt_osf_info*) match->data;
+
+       printf("OS fingerprint match %s%s ", (info->invert) ? "!" : "", info->genre);
+}
+
+static void save(const struct ipt_ip *ip, const struct ipt_entry_match *match)
+{
+       const struct ipt_osf_info *info = (const struct ipt_osf_info*) match->data;
+
+       printf("--genre %s%s ", (info->invert) ? "! ": "", info->genre);
+}
+
+
+static struct iptables_match osf_match = {
+    .name          = "osf",
+    .version       = IPTABLES_VERSION,
+    .size          = IPT_ALIGN(sizeof(struct ipt_osf_info)),
+    .userspacesize = IPT_ALIGN(sizeof(struct ipt_osf_info)),
+    .help          = &help,
+    .init          = &init,
+    .parse         = &parse,
+    .final_check   = &final_check,
+    .print         = &print,
+    .save          = &save,
+    .extra_opts    = opts
+};
+
+
+void _init(void)
+{
+       register_match(&osf_match);
+}