/* Copyright (C) 2007-2019 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>

 *

 */

#include "suricata-common.h"

#include "detect.h"

#include "detect-parse.h"

#include "detect-engine.h"

#include "detect-engine-mpm.h"

#include "detect-engine-prefilter.h"

#include "detect-engine-content-inspection.h"

#include "detect-fast-pattern.h"

#include "detect-tcphdr.h"

/* prototypes */

static int DetectTcphdrSetup (DetectEngineCtx *, Signature *, const char *);

#ifdef UNITTESTS

void DetectTcphdrRegisterTests (void);

#endif

static int g_tcphdr_buffer_id = 0;

static InspectionBuffer *GetData(DetectEngineThreadCtx *det_ctx,

        const DetectEngineTransforms *transforms, Packet *p, const int list_id);

/**

 * \brief Registration function for tcp.hdr: keyword

 */

void DetectTcphdrRegister(void)

{

    sigmatch_table[DETECT_TCPHDR].name = "tcp.hdr";

    sigmatch_table[DETECT_TCPHDR].desc = "sticky buffer to match on the TCP header";

    sigmatch_table[DETECT_TCPHDR].url = "/rules/header-keywords.html#tcphdr";

    sigmatch_table[DETECT_TCPHDR].Setup = DetectTcphdrSetup;

    sigmatch_table[DETECT_TCPHDR].flags |= SIGMATCH_NOOPT | SIGMATCH_INFO_STICKY_BUFFER;

#ifdef UNITTESTS

    sigmatch_table[DETECT_TCPHDR].RegisterTests = DetectTcphdrRegisterTests;

#endif

    g_tcphdr_buffer_id = DetectBufferTypeRegister("tcp.hdr");

    BUG_ON(g_tcphdr_buffer_id < 0);

    DetectBufferTypeSupportsPacket("tcp.hdr");

    DetectPktMpmRegister("tcp.hdr", 2, PrefilterGenericMpmPktRegister, GetData);

    DetectPktInspectEngineRegister("tcp.hdr", GetData,

            DetectEngineInspectPktBufferGeneric);

    return;

}

/**

 * \brief setup tcp.hdr sticky buffer

 *

 * \param de_ctx pointer to the Detection Engine Context

 * \param s pointer to the Current Signature

 * \param _unused unused

 *

 * \retval 0 on Success

 * \retval -1 on Failure

 */

static int DetectTcphdrSetup (DetectEngineCtx *de_ctx, Signature *s, const char *_unused)

{

    if (!(DetectProtoContainsProto(&s->proto, IPPROTO_TCP)))

        return -1;

    s->flags |= SIG_FLAG_REQUIRE_PACKET;

    if (DetectBufferSetActiveList(de_ctx, s, g_tcphdr_buffer_id) < 0)

        return -1;

    return 0;

}

static InspectionBuffer *GetData(DetectEngineThreadCtx *det_ctx,

        const DetectEngineTransforms *transforms, Packet *p, const int list_id)

{

    SCEnter();

    InspectionBuffer *buffer = InspectionBufferGet(det_ctx, list_id);

    if (buffer->inspect == NULL) {

        if (p->tcph == NULL) {

            // may happen when DecodeTCPPacket fails

            // for instance with invalid header length

            return NULL;

        }

        uint32_t hlen = TCP_GET_HLEN(p);

        if (((uint8_t *)p->tcph + (ptrdiff_t)hlen) >

                ((uint8_t *)GET_PKT_DATA(p) + (ptrdiff_t)GET_PKT_LEN(p)))

        {

            SCLogDebug("data out of range: %p > %p",

                    ((uint8_t *)p->tcph + (ptrdiff_t)hlen),

                    ((uint8_t *)GET_PKT_DATA(p) + (ptrdiff_t)GET_PKT_LEN(p)));

            return NULL;

        }

        const uint32_t data_len = hlen;

        const uint8_t *data = (const uint8_t *)p->tcph;

        InspectionBufferSetup(det_ctx, list_id, buffer, data, data_len);

        InspectionBufferApplyTransforms(buffer, transforms);

    }

    return buffer;

}

#ifdef UNITTESTS

#include "tests/detect-tcphdr.c"

#endif