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>

diff --git a/include/linux/netfilter/xt_string.h b/include/linux/netfilter/xt_string.h
index bb21dd1..8a6ba7b 100644 (file)
--- a/include/linux/netfilter/xt_string.h
+++ b/include/linux/netfilter/xt_string.h
@@ -4,6 +4,11 @@
 #define XT_STRING_MAX_PATTERN_SIZE 128
 #define XT_STRING_MAX_ALGO_NAME_SIZE 16
 
+enum {
+       XT_STRING_FLAG_INVERT           = 0x01,
+       XT_STRING_FLAG_IGNORECASE       = 0x02
+};
+
 struct xt_string_info
 {
        u_int16_t from_offset;
@@ -11,7 +16,15 @@ struct xt_string_info
        char      algo[XT_STRING_MAX_ALGO_NAME_SIZE];
        char      pattern[XT_STRING_MAX_PATTERN_SIZE];
        u_int8_t  patlen;
-       u_int8_t  invert;
+       union {
+               struct {
+                       u_int8_t  invert;
+               } v0;
+
+               struct {
+                       u_int8_t  flags;
+               } v1;
+       } u;
 
        /* Used internally by the kernel */
        struct ts_config __attribute__((aligned(8))) *config;

diff --git a/net/netfilter/xt_string.c b/net/netfilter/xt_string.c
index 72f694d..4903182 100644 (file)
--- 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,