/* Copyright (C) 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 Philippe Antoine <p.antoine@catenacyber.fr>

 *

 */

#include "suricata-common.h"

#include "detect.h"

#include "detect-parse.h"

#include "detect-icmpv6-mtu.h"

#include "detect-engine-uint.h"

/* prototypes */

static int DetectICMPv6mtuMatch (DetectEngineThreadCtx *, Packet *,

        const Signature *, const SigMatchCtx *);

static int DetectICMPv6mtuSetup (DetectEngineCtx *, Signature *, const char *);

void DetectICMPv6mtuFree (DetectEngineCtx *de_ctx, void *);

#ifdef UNITTESTS

void DetectICMPv6mtuRegisterTests (void);

#endif

static int PrefilterSetupIcmpv6mtu(DetectEngineCtx *de_ctx, SigGroupHead *sgh);

static bool PrefilterIcmpv6mtuIsPrefilterable(const Signature *s);

/**

 * \brief Registration function for icmpv6.mtu: keyword

 */

void DetectICMPv6mtuRegister(void)

{

    sigmatch_table[DETECT_ICMPV6MTU].name = "icmpv6.mtu";

    sigmatch_table[DETECT_ICMPV6MTU].desc = "match on ICMPv6 MTU field";

    sigmatch_table[DETECT_ICMPV6MTU].url = "/rules/header-keywords.html#icmpv6mtu";

    sigmatch_table[DETECT_ICMPV6MTU].Match = DetectICMPv6mtuMatch;

    sigmatch_table[DETECT_ICMPV6MTU].Setup = DetectICMPv6mtuSetup;

    sigmatch_table[DETECT_ICMPV6MTU].Free = DetectICMPv6mtuFree;

#ifdef UNITTESTS

    sigmatch_table[DETECT_ICMPV6MTU].RegisterTests = DetectICMPv6mtuRegisterTests;

#endif

    sigmatch_table[DETECT_ICMPV6MTU].SupportsPrefilter = PrefilterIcmpv6mtuIsPrefilterable;

    sigmatch_table[DETECT_ICMPV6MTU].SetupPrefilter = PrefilterSetupIcmpv6mtu;

}

// returns 0 on no mtu, and 1 if mtu

static inline int DetectICMPv6mtuGetValue(Packet *p, uint32_t *picmpv6mtu)

{

    if (!(PacketIsICMPv6(p)))

        return 0;

    const ICMPV6Hdr *icmpv6h = PacketGetICMPv6(p);

    if (ICMPV6_GET_CODE(icmpv6h) != 0)

        return 0;

    if (!(ICMPV6_HAS_MTU(icmpv6h)))

        return 0;

    *picmpv6mtu = ICMPV6_GET_MTU(icmpv6h);

    return 1;

}

/**

 * \brief This function is used to match ICMPV6 MTU rule option on a packet with those passed via icmpv6.mtu:

 *

 * \param det_ctx pointer to the pattern matcher thread

 * \param p pointer to the current packet

 * \param s pointer to the signature unused

 * \param ctx pointer to the signature match context

 *

 * \retval 0 no match

 * \retval 1 match

 */

static int DetectICMPv6mtuMatch (DetectEngineThreadCtx *det_ctx, Packet *p,

        const Signature *s, const SigMatchCtx *ctx)

{

    DEBUG_VALIDATE_BUG_ON(PKT_IS_PSEUDOPKT(p));

    uint32_t picmpv6mtu;

    if (DetectICMPv6mtuGetValue(p, &picmpv6mtu) == 0) {

        return 0;

    }

    const DetectU32Data *du32 = (const DetectU32Data *)ctx;

    return DetectU32Match(picmpv6mtu, du32);

}

/**

 * \brief this function is used to attach the parsed icmpv6.mtu data into the current signature

 *

 * \param de_ctx pointer to the Detection Engine Context

 * \param s pointer to the Current Signature

 * \param icmpv6mtustr pointer to the user provided icmpv6.mtu options

 *

 * \retval 0 on Success

 * \retval -1 on Failure

 */

static int DetectICMPv6mtuSetup (DetectEngineCtx *de_ctx, Signature *s, const char *icmpv6mtustr)

{

    DetectU32Data *icmpv6mtud = DetectU32Parse(icmpv6mtustr);

    if (icmpv6mtud == NULL)

        return -1;

    if (SCSigMatchAppendSMToList(de_ctx, s, DETECT_ICMPV6MTU, (SigMatchCtx *)icmpv6mtud,

                DETECT_SM_LIST_MATCH) == NULL) {

        DetectICMPv6mtuFree(de_ctx, icmpv6mtud);

        return -1;

    }

    s->flags |= SIG_FLAG_REQUIRE_PACKET;

    s->proto.flags |= DETECT_PROTO_IPV6;

    return 0;

}

/**

 * \brief this function will free memory associated with DetectU32Data

 *

 * \param ptr pointer to DetectU32Data

 */

void DetectICMPv6mtuFree(DetectEngineCtx *de_ctx, void *ptr)

{

    SCDetectU32Free(ptr);

}

/* prefilter code */

static void

PrefilterPacketIcmpv6mtuMatch(DetectEngineThreadCtx *det_ctx, Packet *p, const void *pectx)

{

    DEBUG_VALIDATE_BUG_ON(PKT_IS_PSEUDOPKT(p));

    uint32_t picmpv6mtu;

    if (DetectICMPv6mtuGetValue(p, &picmpv6mtu) == 0) {

        return;

    }

    /* during setup Suricata will automatically see if there is another

     * check that can be added: alproto, sport or dport */

    const PrefilterPacketHeaderCtx *ctx = pectx;

    if (!PrefilterPacketHeaderExtraMatch(ctx, p))

        return;

    /* if we match, add all the sigs that use this prefilter. This means

     * that these will be inspected further */

    DetectU32Data du32;

    du32.mode = ctx->v1.u8[0];

    du32.arg1 = ctx->v1.u32[1];

    du32.arg2 = ctx->v1.u32[2];

    if (DetectU32Match(picmpv6mtu, &du32))

    {

        SCLogDebug("packet matches icmpv6.mtu/hl %u", picmpv6mtu);

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

    }

}

static int PrefilterSetupIcmpv6mtu(DetectEngineCtx *de_ctx, SigGroupHead *sgh)

{

    return PrefilterSetupPacketHeader(de_ctx, sgh, DETECT_ICMPV6MTU, SIG_MASK_REQUIRE_REAL_PKT,

            PrefilterPacketU32Set, PrefilterPacketU32Compare, PrefilterPacketIcmpv6mtuMatch);

}

static bool PrefilterIcmpv6mtuIsPrefilterable(const Signature *s)

{

    return PrefilterIsPrefilterableById(s, DETECT_ICMPV6MTU);

}

#ifdef UNITTESTS

#include "tests/detect-icmpv6-mtu.c"

#endif