suricata/src/detect-depth.c

/* Copyright (C) 2007-2010 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 depth keyword
 */

#include "suricata-common.h"

#include "decode.h"

#include "detect.h"
#include "detect-parse.h"
#include "detect-content.h"
#include "detect-uricontent.h"

#include "flow-var.h"

#include "util-debug.h"

static int DetectDepthSetup (DetectEngineCtx *, Signature *, char *);

void DetectDepthRegister (void) {
    sigmatch_table[DETECT_DEPTH].name = "depth";
    sigmatch_table[DETECT_DEPTH].Match = NULL;
    sigmatch_table[DETECT_DEPTH].Setup = DetectDepthSetup;
    sigmatch_table[DETECT_DEPTH].Free  = NULL;
    sigmatch_table[DETECT_DEPTH].RegisterTests = NULL;

    sigmatch_table[DETECT_DEPTH].flags |= SIGMATCH_PAYLOAD;
}

static int DetectDepthSetup (DetectEngineCtx *de_ctx, Signature *s, char *depthstr)
{
    char *str = depthstr;
    char dubbed = 0;

    /* strip "'s */
    if (depthstr[0] == '\"' && depthstr[strlen(depthstr)-1] == '\"') {
        str = SCStrdup(depthstr+1);
        str[strlen(depthstr)-2] = '\0';
        dubbed = 1;
    }

    /** Search for the first previous DetectContent or uricontent
     * SigMatch (it can be the same as this one) */
    SigMatch *pm = SigMatchGetLastPattern(s);
    if (pm == NULL) {
        SCLogError(SC_ERR_DEPTH_MISSING_CONTENT, "depth needs a preceeding "
                "content or uricontent option");
        if (dubbed) SCFree(str);
        return -1;
    }

    switch (pm->type) {
        case DETECT_URICONTENT:
        {
            DetectUricontentData *ud = (DetectUricontentData *)pm->ctx;
            if (ud == NULL) {
                SCLogError(SC_ERR_INVALID_ARGUMENT, "invalid argument");
                if (dubbed) SCFree(str);
                return -1;
            }
            ud->depth = (uint32_t)atoi(str);
            if (ud->uricontent_len + ud->offset > ud->depth) {
                uint32_t depth = (ud->depth > ud->uricontent_len) ?
                    ud->depth : ud->uricontent_len;
                ud->depth = ud->offset + depth;

                SCLogDebug("depth increased to %"PRIu32" to match pattern len "
                        "and offset", ud->depth);
            }
        }
        break;

        case DETECT_CONTENT:
        {
            DetectContentData *cd = (DetectContentData *)pm->ctx;
            if (cd == NULL) {
                SCLogError(SC_ERR_INVALID_ARGUMENT, "invalid argument");
                if (dubbed) SCFree(str);
                return -1;
            }
            cd->depth = (uint32_t)atoi(str);
            if (cd->content_len + cd->offset > cd->depth) {
                uint32_t depth = (cd->depth > cd->content_len) ?
                    cd->depth : cd->content_len;
                cd->depth = cd->offset + depth;

                SCLogDebug("depth increased to %"PRIu32" to match pattern len "
                        "and offset", cd->depth);
            }
        }
        break;

        default:
            SCLogError(SC_ERR_DEPTH_MISSING_CONTENT, "depth needs a preceeding "
                    "content (or uricontent) option");
            if (dubbed) SCFree(str);
                return -1;
        break;
    }

    if (dubbed) SCFree(str);
    return 0;
}