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/* Copyright (C) 2007-2016 Open Information Security Foundation
*
* You can copy, redistribute or modify this Program under the terms of
* the GNU General Public License version 2 as published by the Free
* Software Foundation.
*
* 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
* version 2 along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
* 02110-1301, USA.
*/
/**
* \file
*
* \author Victor Julien <victor@inliniac.net>
*
* Implements the prefilter keyword
*/
#include "suricata-common.h"
#include "decode.h"
#include "detect.h"
#include "detect-parse.h"
#include "detect-content.h"
#include "detect-prefilter.h"
#include "util-debug.h"
static int DetectPrefilterSetup (DetectEngineCtx *, Signature *, const char *);
void DetectPrefilterRegister(void)
{
sigmatch_table[DETECT_PREFILTER].name = "prefilter";
sigmatch_table[DETECT_PREFILTER].desc = "force a condition to be used as prefilter";
sigmatch_table[DETECT_PREFILTER].url = "/rules/prefilter-keywords.html#prefilter";
sigmatch_table[DETECT_PREFILTER].Setup = DetectPrefilterSetup;
sigmatch_table[DETECT_PREFILTER].flags |= SIGMATCH_NOOPT;
}
/**
* \internal
* \brief Apply the prefilter keyword to the last match
* \param det_ctx detection engine ctx
* \param s signature
* \param nullstr should be null
* \retval 0 ok
* \retval -1 failure
*/
static int DetectPrefilterSetup (DetectEngineCtx *de_ctx, Signature *s, const char *nullstr)
{
SCEnter();
if (nullstr != NULL) {
SCLogError("prefilter has value");
SCReturnInt(-1);
}
if (s->flags & SIG_FLAG_PREFILTER) {
SCLogError("prefilter already set");
SCReturnInt(-1);
}
SigMatch *sm = DetectGetLastSM(s);
if (sm == NULL) {
SCLogError("prefilter needs preceding match");
SCReturnInt(-1);
}
/* if the sig match is content, prefilter should act like
* 'fast_pattern' w/o options. */
if (sm->type == DETECT_CONTENT) {
DetectContentData *cd = (DetectContentData *)sm->ctx;
if ((cd->flags & DETECT_CONTENT_NEGATED) &&
((cd->flags & DETECT_CONTENT_DISTANCE) ||
(cd->flags & DETECT_CONTENT_WITHIN) ||
(cd->flags & DETECT_CONTENT_OFFSET) ||
(cd->flags & DETECT_CONTENT_DEPTH)))
{
SCLogError("prefilter; cannot be "
"used with negated content, along with relative modifiers");
SCReturnInt(-1);
}
cd->flags |= DETECT_CONTENT_FAST_PATTERN;
} else {
if (sigmatch_table[sm->type].SupportsPrefilter == NULL) {
SCLogError("prefilter is not supported for %s", sigmatch_table[sm->type].name);
SCReturnInt(-1);
}
s->flags |= SIG_FLAG_PREFILTER;
/* make sure setup function runs for this type. */
de_ctx->sm_types_prefilter[sm->type] = true;
}
s->init_data->prefilter_sm = sm;
SCReturnInt(0);
}
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