netfilter: fix string extension for case insensitive pattern matching

The flag XT_STRING_FLAG_IGNORECASE indicates case insensitive string
matching. netfilter can find cmd.exe, Cmd.exe, cMd.exe and etc easily.

A new revision 1 was added, in the meantime invert of xt_string_info
was moved into flags as a flag. If revision is 1, The flag
XT_STRING_FLAG_INVERT indicates invert matching.

Signed-off-by: Joonwoo Park <joonwpark81@gmail.com>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 36 insertions, 2 deletions

diff --git a/net/netfilter/xt_string.c b/net/netfilter/xt_string.c
index 72f694d947f4..4903182a062b 100644
--- a/net/netfilter/xt_string.c
+++ b/net/netfilter/xt_string.c
@@ -29,12 +29,16 @@ string_mt(const struct sk_buff *skb, const struct net_device *in,
 {
         const struct xt_string_info *conf = matchinfo;
         struct ts_state state;
+        int invert;
 
         memset(&state, 0, sizeof(struct ts_state));
 
+        invert = (match->revision == 0 ? conf->u.v0.invert :
+                                    conf->u.v1.flags & XT_STRING_FLAG_INVERT);
+
         return (skb_find_text((struct sk_buff *)skb, conf->from_offset,
                              conf->to_offset, conf->config, &state)
-                             != UINT_MAX) ^ conf->invert;
+                             != UINT_MAX) ^ invert;
 }
 
 #define STRING_TEXT_PRIV(m) ((struct xt_string_info *)(m))
@@ -46,6 +50,7 @@ string_mt_check(const char *tablename, const void *ip,
 {
         struct xt_string_info *conf = matchinfo;
         struct ts_config *ts_conf;
+        int flags = TS_AUTOLOAD;
 
         /* Damn, can't handle this case properly with iptables... */
         if (conf->from_offset > conf->to_offset)
@@ -54,8 +59,15 @@ string_mt_check(const char *tablename, const void *ip,
                 return false;
         if (conf->patlen > XT_STRING_MAX_PATTERN_SIZE)
                 return false;
+        if (match->revision == 1) {
+                if (conf->u.v1.flags &
+                    ~(XT_STRING_FLAG_IGNORECASE | XT_STRING_FLAG_INVERT))
+                        return false;
+                if (conf->u.v1.flags & XT_STRING_FLAG_IGNORECASE)
+                        flags |= TS_IGNORECASE;
+        }
         ts_conf = textsearch_prepare(conf->algo, conf->pattern, conf->patlen,
-                                     GFP_KERNEL, TS_AUTOLOAD);
+                                     GFP_KERNEL, flags);
         if (IS_ERR(ts_conf))
                 return false;
 
@@ -72,6 +84,17 @@ static void string_mt_destroy(const struct xt_match *match, void *matchinfo)
 static struct xt_match string_mt_reg[] __read_mostly = {
         {
                 .name           = "string",
+                .revision       = 0,
+                .family         = AF_INET,
+                .checkentry     = string_mt_check,
+                .match          = string_mt,
+                .destroy        = string_mt_destroy,
+                .matchsize      = sizeof(struct xt_string_info),
+                .me             = THIS_MODULE
+        },
+        {
+                .name           = "string",
+                .revision       = 1,
                 .family         = AF_INET,
                 .checkentry     = string_mt_check,
                 .match          = string_mt,
@@ -81,6 +104,17 @@ static struct xt_match string_mt_reg[] __read_mostly = {
         },
         {
                 .name           = "string",
+                .revision       = 0,
+                .family         = AF_INET6,
+                .checkentry     = string_mt_check,
+                .match          = string_mt,
+                .destroy        = string_mt_destroy,
+                .matchsize      = sizeof(struct xt_string_info),
+                .me             = THIS_MODULE
+        },
+        {
+                .name           = "string",
+                .revision       = 1,
                 .family         = AF_INET6,
                 .checkentry     = string_mt_check,
                 .match          = string_mt,