[NETFILTER]: Add string match

Signed-off-by: Pablo Neira Ayuso <pablo@eurodev.net>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 104 insertions, 0 deletions

diff --git a/net/ipv4/netfilter/Kconfig b/net/ipv4/netfilter/Kconfig
index 3f7e6e49cbdd..f2bea6ecb226 100644
--- a/net/ipv4/netfilter/Kconfig
+++ b/net/ipv4/netfilter/Kconfig
@@ -410,6 +410,18 @@ config IP_NF_MATCH_HASHLIMIT
           destination IP' or `500pps from any given source IP'  with a single
           IPtables rule.
 
+config IP_NF_MATCH_STRING
+        tristate  'string match support'
+        depends on IP_NF_IPTABLES 
+        select TEXTSEARCH
+        select TEXTSEARCH_KMP
+        select TEXTSEARCH_FSM
+        help
+          This option adds a `string' match, which allows you to look for
+          pattern matchings in packets.
+
+          To compile it as a module, choose M here.  If unsure, say N.
+
 # `filter', generic and specific targets
 config IP_NF_FILTER
         tristate "Packet filtering"
diff --git a/net/ipv4/netfilter/Makefile b/net/ipv4/netfilter/Makefile
index 7c8ae858aa43..89cae69ee208 100644
--- a/net/ipv4/netfilter/Makefile
+++ b/net/ipv4/netfilter/Makefile
@@ -65,6 +65,7 @@ obj-$(CONFIG_IP_NF_MATCH_REALM) += ipt_realm.o
 obj-$(CONFIG_IP_NF_MATCH_ADDRTYPE) += ipt_addrtype.o
 obj-$(CONFIG_IP_NF_MATCH_PHYSDEV) += ipt_physdev.o
 obj-$(CONFIG_IP_NF_MATCH_COMMENT) += ipt_comment.o
+obj-$(CONFIG_IP_NF_MATCH_STRING) += ipt_string.o
 
 # targets
 obj-$(CONFIG_IP_NF_TARGET_REJECT) += ipt_REJECT.o
diff --git a/net/ipv4/netfilter/ipt_string.c b/net/ipv4/netfilter/ipt_string.c
new file mode 100644
index 000000000000..b5def204d798
--- /dev/null
+++ b/net/ipv4/netfilter/ipt_string.c
@@ -0,0 +1,91 @@
+/* String matching match for iptables
+ * 
+ * (C) 2005 Pablo Neira Ayuso <pablo@eurodev.net>
+ *
+ * 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/init.h>
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/skbuff.h>
+#include <linux/netfilter_ipv4/ip_tables.h>
+#include <linux/netfilter_ipv4/ipt_string.h>
+#include <linux/textsearch.h>
+
+MODULE_AUTHOR("Pablo Neira Ayuso <pablo@eurodev.net>");
+MODULE_DESCRIPTION("IP tables string match module");
+MODULE_LICENSE("GPL");
+
+static int match(const struct sk_buff *skb,
+                 const struct net_device *in,
+                 const struct net_device *out,
+                 const void *matchinfo,
+                 int offset,
+                 int *hotdrop)
+{
+        struct ts_state state;
+        struct ipt_string_info *conf = (struct ipt_string_info *) matchinfo;
+
+        memset(&state, 0, sizeof(struct ts_state));
+
+        return (skb_find_text((struct sk_buff *)skb, conf->from_offset, 
+                             conf->to_offset, conf->config, &state) 
+                             != UINT_MAX) && !conf->invert;
+}
+
+#define STRING_TEXT_PRIV(m) ((struct ipt_string_info *) m)
+
+static int checkentry(const char *tablename,
+                      const struct ipt_ip *ip,
+                      void *matchinfo,
+                      unsigned int matchsize,
+                      unsigned int hook_mask)
+{
+        struct ipt_string_info *conf = matchinfo;
+        struct ts_config *ts_conf;
+
+        if (matchsize != IPT_ALIGN(sizeof(struct ipt_string_info)))
+                return 0;
+
+        /* Damn, can't handle this case properly with iptables... */
+        if (conf->from_offset > conf->to_offset)
+                return 0;
+
+        ts_conf = textsearch_prepare(conf->algo, conf->pattern, conf->patlen,
+                                     GFP_KERNEL, TS_AUTOLOAD);
+        if (IS_ERR(ts_conf))
+                return 0;
+
+        conf->config = ts_conf;
+
+        return 1;
+}
+
+static void destroy(void *matchinfo, unsigned int matchsize)
+{
+        textsearch_destroy(STRING_TEXT_PRIV(matchinfo)->config);
+}
+
+static struct ipt_match string_match = {
+        .name           = "string",
+        .match          = match,
+        .checkentry     = checkentry,
+        .destroy        = destroy,
+        .me             = 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);