2.4.9-ipt_string.patch

2.4.9-ipt_string.patch

[Kim Yong Il]

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This is "iptables --string" patch


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diff -urN linux-2.4.9.orig/Documentation/Configure.help linux-2.4.9/Documentation/Configure.help
--- linux-2.4.9.orig/Documentation/Configure.help	Mon Aug 13 02:51:41 2001
+++ linux-2.4.9/Documentation/Configure.help	Fri Aug 17 12:28:25 2001
@@ -1939,6 +1939,14 @@
   If you want to compile it as a module, say M here and read
   Documentation/modules.txt.  If unsure, say `N'.
 
+String match support (EXPERIMENTAL)
+CONFIG_IP_NF_MATCH_STRING
+  String matching alows you to match packets which contain a
+  specified string of characters.
+
+  If you want to compile it as a module, say M here and read
+  Documentation/modules.txt.  If unsure, say `N'.
+
 Unclean match support (EXPERIMENTAL)
 CONFIG_IP_NF_MATCH_UNCLEAN
   Unclean packet matching matches any strange or invalid packets, by
diff -urN linux-2.4.9.orig/include/linux/netfilter_ipv4/ipt_string.h linux-2.4.9/include/linux/netfilter_ipv4/ipt_string.h
--- linux-2.4.9.orig/include/linux/netfilter_ipv4/ipt_string.h	Thu Jan  1 09:00:00 1970
+++ linux-2.4.9/include/linux/netfilter_ipv4/ipt_string.h	Sat Aug 11 13:18:32 2001
@@ -0,0 +1,21 @@
+#ifndef _IPT_STRING_H
+#define _IPT_STRING_H
+
+/* *** PERFORMANCE TWEAK ***
+ * Packet size and search string threshold,
+ * above which sublinear searches is used. */
+#define IPT_STRING_HAYSTACK_THRESH	100
+#define IPT_STRING_NEEDLE_THRESH	20
+
+#define BM_MAX_NLEN 256
+#define BM_MAX_HLEN 1024
+
+typedef char *(*proc_ipt_search) (char *, char *, int, int);
+
+struct ipt_string_info {
+    char string[BM_MAX_NLEN];
+    u_int16_t invert;
+    u_int16_t len;
+};
+
+#endif /* _IPT_STRING_H */
diff -urN linux-2.4.9.orig/net/ipv4/netfilter/Config.in linux-2.4.9/net/ipv4/netfilter/Config.in
--- linux-2.4.9.orig/net/ipv4/netfilter/Config.in	Wed Mar  7 15:44:16 2001
+++ linux-2.4.9/net/ipv4/netfilter/Config.in	Fri Aug 17 12:29:11 2001
@@ -26,6 +26,7 @@
   fi
   if [ "$CONFIG_EXPERIMENTAL" = "y" ]; then
     dep_tristate '  Unclean match support (EXPERIMENTAL)' CONFIG_IP_NF_MATCH_UNCLEAN $CONFIG_IP_NF_IPTABLES
+    dep_tristate '  String match support (EXPERIMENTAL)' CONFIG_IP_NF_MATCH_STRING $CONFIG_IP_NF_IPTABLES
     dep_tristate '  Owner match support (EXPERIMENTAL)' CONFIG_IP_NF_MATCH_OWNER $CONFIG_IP_NF_IPTABLES
   fi
 # The targets
diff -urN linux-2.4.9.orig/net/ipv4/netfilter/Makefile linux-2.4.9/net/ipv4/netfilter/Makefile
--- linux-2.4.9.orig/net/ipv4/netfilter/Makefile	Thu Apr 26 07:00:28 2001
+++ linux-2.4.9/net/ipv4/netfilter/Makefile	Fri Aug 17 12:28:53 2001
@@ -54,6 +54,7 @@
 obj-$(CONFIG_IP_NF_MATCH_TOS) += ipt_tos.o
 obj-$(CONFIG_IP_NF_MATCH_STATE) += ipt_state.o
 obj-$(CONFIG_IP_NF_MATCH_UNCLEAN) += ipt_unclean.o
+obj-$(CONFIG_IP_NF_MATCH_STRING) += ipt_string.o
 obj-$(CONFIG_IP_NF_MATCH_TCPMSS) += ipt_tcpmss.o
 
 # targets
diff -urN linux-2.4.9.orig/net/ipv4/netfilter/ipt_string.c linux-2.4.9/net/ipv4/netfilter/ipt_string.c
--- linux-2.4.9.orig/net/ipv4/netfilter/ipt_string.c	Thu Jan  1 09:00:00 1970
+++ linux-2.4.9/net/ipv4/netfilter/ipt_string.c	Sat Aug 11 13:18:32 2001
@@ -0,0 +1,156 @@
+/* Kernel module to match a string into a packet.
+ *
+ * Copyright (C) 2000 Emmanuel Roger  <winfield@freegates.be>
+ * 
+ * ChangeLog
+ *	02.05.2001: Gianni Tedesco <gianni@ecsc.co.uk>
+ *		Fixed kernel panic, due to overrunning boyer moore string
+ *		tables. Also slightly tweaked heuristic for deciding what
+ * 		search algo to use.
+ * 	27.01.2001: Gianni Tedesco <gianni@ecsc.co.uk>
+ * 		Implemented Boyer Moore Sublinear search algorithm
+ * 		alongside the existing linear search based on memcmp().
+ * 		Also a quick check to decide which method to use on a per
+ * 		packet basis.
+ */
+
+#include <linux/module.h>
+#include <linux/skbuff.h>
+#include <linux/file.h>
+#include <net/sock.h>
+
+#include <linux/netfilter_ipv4/ip_tables.h>
+#include <linux/netfilter_ipv4/ipt_string.h>
+
+int skip[BM_MAX_HLEN];
+int shift[BM_MAX_HLEN];
+
+/* Boyer Moore Sublinear string search - VERY FAST */
+char *search_sublinear (char *needle, char *haystack, int needle_len, int haystack_len) 
+{
+	int M1, right_end, sk, sh;  
+	int ended, j, len[BM_MAX_HLEN];
+	int i;
+
+	/* Setup skip/shift tables */
+	M1 = right_end = needle_len-1;
+	for (i = 0; i < BM_MAX_HLEN; i++) skip[i] = needle_len;  
+	for (i = 0; needle[i]; i++) skip[needle[i]] = M1 - i;  
+
+	for (i = 1; i < needle_len; i++) {   
+		for (j = 0; j < needle_len && needle[M1 - j] == needle[M1 - i - j]; j++);  
+		len[i] = j;  
+	}  
+
+	shift[0] = 1;  
+	for (i = 1; i < needle_len; i++) shift[i] = needle_len;  
+	for (i = M1; i > 0; i--) shift[len[i]] = i;  
+	ended = 0;  
+	
+	for (i = 0; i < needle_len; i++) {  
+		if (len[i] == M1 - i) ended = i;  
+		if (ended) shift[i] = ended;  
+	}  
+
+	/* Do the search*/  
+	while (right_end < haystack_len)
+	{
+		for (i = 0; i < needle_len && haystack[right_end - i] == needle[M1 - i]; i++);  
+		if (i == needle_len) {
+			return haystack+(right_end - M1);
+		}
+		
+		sk = skip[haystack[right_end - i]];  
+		sh = shift[i];
+		right_end = max(int, right_end - i + sk, right_end + sh);  
+	}
+
+	return NULL;
+}  
+
+/* Linear string search based on memcmp() */
+char *search_linear (char *needle, char *haystack, int needle_len, int haystack_len) 
+{
+	char *k = haystack + (haystack_len-needle_len);
+	char *t = haystack;
+	
+	while ( t++ < k ) {
+		if ( memcmp(t, needle, needle_len) == 0 ) return t;
+	}
+
+	return NULL;
+}
+
+
+static int
+match(const struct sk_buff *skb,
+      const struct net_device *in,
+      const struct net_device *out,
+      const void *matchinfo,
+      int offset,
+      const void *hdr,
+      u_int16_t datalen,
+      int *hotdrop)
+{
+	const struct ipt_string_info *info = matchinfo;
+	struct iphdr *ip = skb->nh.iph;
+	int hlen, nlen;
+	char *needle, *haystack;
+	proc_ipt_search search=search_linear;
+
+	if ( !ip ) return 0;
+
+	/* get lenghts, and validate them */
+	nlen=info->len;
+	hlen=ntohs(ip->tot_len)-(ip->ihl*4);
+	if ( nlen > hlen ) return 0;
+
+	needle=(char *)&info->string;
+	haystack=(char *)ip+(ip->ihl*4);
+
+	/* The sublinear search comes in to its own
+	 * on the larger packets */
+	if ( (hlen>IPT_STRING_HAYSTACK_THRESH) &&
+	  	(nlen>IPT_STRING_NEEDLE_THRESH) ) {
+		if ( hlen < BM_MAX_HLEN ) {
+			search=search_sublinear;
+		}else{
+			if (net_ratelimit())
+				printk(KERN_INFO "ipt_string: Packet too big "
+					"to attempt sublinear string search "
+					"(%d bytes)\n", hlen );
+		}
+	}
+	
+    return ((search(needle, haystack, nlen, hlen)!=NULL) ^ info->invert);
+}
+
+static int
+checkentry(const char *tablename,
+           const struct ipt_ip *ip,
+           void *matchinfo,
+           unsigned int matchsize,
+           unsigned int hook_mask)
+{
+
+       if (matchsize != IPT_ALIGN(sizeof(struct ipt_string_info)))
+               return 0;
+
+       return 1;
+}
+
+static struct ipt_match string_match
+= { { NULL, NULL }, "string", &match, &checkentry, NULL, THIS_MODULE };
+
+static int __init init(void)
+{
+       return ipt_register_match(&string_match);
+}
+
+static void __exit fini(void)
+{
+       ipt_unregister_match(&string_match);
+}
+
+module_init(init);
+module_exit(fini);

Re: 2.4.9-ipt_string.patch

[Dan Hollis]

On Thu, 20 Sep 2001, Kim Yong Il wrote:
> This is "iptables --string" patch

excellent! this puts us one step closer to cisco-NBAR.

-Dan

-- 
[-] Omae no subete no kichi wa ore no mono da. [-]