/* Copyright (C) 2007-2020 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 Gurvinder Singh <gurvindersighdahiya@gmail.com>

 * \author Victor Julien <victor@inliniac.net>

 *

 * Implements the ttl keyword including prefilter support.

 */

#include "suricata-common.h"

#include "stream-tcp.h"

#include "detect.h"

#include "detect-parse.h"

#include "detect-engine-prefilter-common.h"

#include "detect-engine-uint.h"

#include "detect-ttl.h"

#include "util-debug.h"

#include "util-byte.h"

/* prototypes */

static int DetectTtlMatch (DetectEngineThreadCtx *, Packet *,

        const Signature *, const SigMatchCtx *);

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

void DetectTtlFree (DetectEngineCtx *, void *);

#ifdef UNITTESTS

void DetectTtlRegisterTests (void);

#endif

static int PrefilterSetupTtl(DetectEngineCtx *de_ctx, SigGroupHead *sgh);

static bool PrefilterTtlIsPrefilterable(const Signature *s);

/**

 * \brief Registration function for ttl: keyword

 */

void DetectTtlRegister(void)

{

    sigmatch_table[DETECT_TTL].name = "ttl";

    sigmatch_table[DETECT_TTL].desc = "check for a specific IP time-to-live value";

    sigmatch_table[DETECT_TTL].url = "/rules/header-keywords.html#ttl";

    sigmatch_table[DETECT_TTL].Match = DetectTtlMatch;

    sigmatch_table[DETECT_TTL].Setup = DetectTtlSetup;

    sigmatch_table[DETECT_TTL].Free = DetectTtlFree;

#ifdef UNITTESTS

    sigmatch_table[DETECT_TTL].RegisterTests = DetectTtlRegisterTests;

#endif

    sigmatch_table[DETECT_TTL].SupportsPrefilter = PrefilterTtlIsPrefilterable;

    sigmatch_table[DETECT_TTL].SetupPrefilter = PrefilterSetupTtl;

    return;

}

/**

 * \brief This function is used to match TTL rule option on a packet with

 *        those passed via ttl

 *

 * \param t pointer to thread vars

 * \param det_ctx pointer to the pattern matcher thread

 * \param p pointer to the current packet

 * \param m pointer to the sigmatch that we will cast into DetectU8Data

 *

 * \retval 0 no match

 * \retval 1 match

 */

static int DetectTtlMatch (DetectEngineThreadCtx *det_ctx, Packet *p,

        const Signature *s, const SigMatchCtx *ctx)

{

    if (PKT_IS_PSEUDOPKT(p))

        return 0;

    uint8_t pttl;

    if (PKT_IS_IPV4(p)) {

        pttl = IPV4_GET_IPTTL(p);

    } else if (PKT_IS_IPV6(p)) {

        pttl = IPV6_GET_HLIM(p);

    } else {

        SCLogDebug("Packet is not IPv4 or IPv6");

        return 0;

    }

    const DetectU8Data *ttld = (const DetectU8Data *)ctx;

    return DetectU8Match(pttl, ttld);

}

/**

 * \brief this function is used to attld the parsed ttl data into the current signature

 *

 * \param de_ctx pointer to the Detection Engine Context

 * \param s pointer to the Current Signature

 * \param ttlstr pointer to the user provided ttl options

 *

 * \retval 0 on Success

 * \retval -1 on Failure

 */

static int DetectTtlSetup (DetectEngineCtx *de_ctx, Signature *s, const char *ttlstr)

{

    DetectU8Data *ttld = DetectU8Parse(ttlstr);

    if (ttld == NULL)

        return -1;

    SigMatch *sm = SigMatchAlloc();

    if (sm == NULL) {

        DetectTtlFree(de_ctx, ttld);

        return -1;

    }

    sm->type = DETECT_TTL;

    sm->ctx = (SigMatchCtx *)ttld;

    SigMatchAppendSMToList(s, sm, DETECT_SM_LIST_MATCH);

    s->flags |= SIG_FLAG_REQUIRE_PACKET;

    return 0;

}

/**

 * \brief this function will free memory associated with DetectU8Data

 *

 * \param ptr pointer to DetectU8Data

 */

void DetectTtlFree(DetectEngineCtx *de_ctx, void *ptr)

{

    rs_detect_u8_free(ptr);

}

/* prefilter code */

static void

PrefilterPacketTtlMatch(DetectEngineThreadCtx *det_ctx, Packet *p, const void *pectx)

{

    if (PKT_IS_PSEUDOPKT(p)) {

        SCReturn;

    }

    uint8_t pttl;

    if (PKT_IS_IPV4(p)) {

        pttl = IPV4_GET_IPTTL(p);

    } else if (PKT_IS_IPV6(p)) {

        pttl = IPV6_GET_HLIM(p);

    } else {

        SCLogDebug("Packet is not IPv4 or IPv6");

        return;

    }

    const PrefilterPacketHeaderCtx *ctx = pectx;

    if (!PrefilterPacketHeaderExtraMatch(ctx, p))

        return;

    DetectU8Data du8;

    du8.mode = ctx->v1.u8[0];

    du8.arg1 = ctx->v1.u8[1];

    du8.arg2 = ctx->v1.u8[2];

    if (DetectU8Match(pttl, &du8)) {

        SCLogDebug("packet matches ttl/hl %u", pttl);

        PrefilterAddSids(&det_ctx->pmq, ctx->sigs_array, ctx->sigs_cnt);

    }

}

static int PrefilterSetupTtl(DetectEngineCtx *de_ctx, SigGroupHead *sgh)

{

    return PrefilterSetupPacketHeader(de_ctx, sgh, DETECT_TTL, PrefilterPacketU8Set,

            PrefilterPacketU8Compare, PrefilterPacketTtlMatch);

}

static bool PrefilterTtlIsPrefilterable(const Signature *s)

{

    const SigMatch *sm;

    for (sm = s->init_data->smlists[DETECT_SM_LIST_MATCH] ; sm != NULL; sm = sm->next) {

        switch (sm->type) {

            case DETECT_TTL:

                return true;

        }

    }

    return false;

}

#ifdef UNITTESTS

#include "tests/detect-ttl.c"

#endif