/* 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 Brian Rectanus <brectanu@gmail.com>

 *

 * Implements the seq keyword.

 */

#include "suricata-common.h"

#include "decode.h"

#include "detect.h"

#include "detect-parse.h"

#include "detect-engine.h"

#include "detect-engine-prefilter.h"

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

#include "detect-engine-build.h"

#include "detect-tcp-seq.h"

#include "util-byte.h"

#include "util-unittest.h"

#include "util-unittest-helper.h"

#include "util-debug.h"

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

static int DetectSeqMatch(DetectEngineThreadCtx *,

                          Packet *, const Signature *, const SigMatchCtx *);

#ifdef UNITTESTS

static void DetectSeqRegisterTests(void);

#endif

static void DetectSeqFree(DetectEngineCtx *, void *);

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

static bool PrefilterTcpSeqIsPrefilterable(const Signature *s);

void DetectSeqRegister(void)

{

    sigmatch_table[DETECT_SEQ].name = "tcp.seq";

    sigmatch_table[DETECT_SEQ].alias = "seq";

    sigmatch_table[DETECT_SEQ].desc = "check for a specific TCP sequence number";

    sigmatch_table[DETECT_SEQ].url = "/rules/header-keywords.html#seq";

    sigmatch_table[DETECT_SEQ].Match = DetectSeqMatch;

    sigmatch_table[DETECT_SEQ].Setup = DetectSeqSetup;

    sigmatch_table[DETECT_SEQ].Free = DetectSeqFree;

#ifdef UNITTESTS

    sigmatch_table[DETECT_SEQ].RegisterTests = DetectSeqRegisterTests;

#endif

    sigmatch_table[DETECT_SEQ].SupportsPrefilter = PrefilterTcpSeqIsPrefilterable;

    sigmatch_table[DETECT_SEQ].SetupPrefilter = PrefilterSetupTcpSeq;

}

/**

 * \internal

 * \brief This function is used to match packets with a given Seq number

 *

 * \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 DetectSeqData

 *

 * \retval 0 no match

 * \retval 1 match

 */

static int DetectSeqMatch(DetectEngineThreadCtx *det_ctx,

                          Packet *p, const Signature *s, const SigMatchCtx *ctx)

{

    const DetectSeqData *data = (const DetectSeqData *)ctx;

    /* This is only needed on TCP packets */

    if (!(PKT_IS_TCP(p)) || PKT_IS_PSEUDOPKT(p)) {

        return 0;

    }

    return (data->seq == TCP_GET_SEQ(p)) ? 1 : 0;

}

/**

 * \internal

 * \brief this function is used to add the seq option into the signature

 *

 * \param de_ctx pointer to the Detection Engine Context

 * \param s pointer to the Current Signature

 * \param optstr pointer to the user provided options

 *

 * \retval 0 on Success

 * \retval -1 on Failure

 */

static int DetectSeqSetup (DetectEngineCtx *de_ctx, Signature *s, const char *optstr)

{

    DetectSeqData *data = NULL;

    SigMatch *sm = NULL;

    data = SCMalloc(sizeof(DetectSeqData));

    if (unlikely(data == NULL))

        goto error;

    sm = SigMatchAlloc();

    if (sm == NULL)

        goto error;

    sm->type = DETECT_SEQ;

    if (StringParseUint32(&data->seq, 10, 0, optstr) < 0) {

        goto error;

    }

    sm->ctx = (SigMatchCtx*)data;

    SigMatchAppendSMToList(s, sm, DETECT_SM_LIST_MATCH);

    s->flags |= SIG_FLAG_REQUIRE_PACKET;

    return 0;

error:

    if (data)

        SCFree(data);

    if (sm)

        SigMatchFree(de_ctx, sm);

    return -1;

}

/**

 * \internal

 * \brief this function will free memory associated with seq option

 *

 * \param data pointer to seq configuration data

 */

static void DetectSeqFree(DetectEngineCtx *de_ctx, void *ptr)

{

    DetectSeqData *data = (DetectSeqData *)ptr;

    SCFree(data);

}

/* prefilter code */

static void

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

{

    const PrefilterPacketHeaderCtx *ctx = pectx;

    if (!PrefilterPacketHeaderExtraMatch(ctx, p))

        return;

    if ((p->proto) == IPPROTO_TCP && !(PKT_IS_PSEUDOPKT(p)) &&

        (p->tcph != NULL) && (TCP_GET_SEQ(p) == ctx->v1.u32[0]))

    {

        SCLogDebug("packet matches TCP seq %u", ctx->v1.u32[0]);

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

    }

}

static void

PrefilterPacketSeqSet(PrefilterPacketHeaderValue *v, void *smctx)

{

    const DetectSeqData *a = smctx;

    v->u32[0] = a->seq;

}

static bool

PrefilterPacketSeqCompare(PrefilterPacketHeaderValue v, void *smctx)

{

    const DetectSeqData *a = smctx;

    if (v.u32[0] == a->seq)

        return true;

    return false;

}

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

{

    return PrefilterSetupPacketHeader(de_ctx, sgh, DETECT_SEQ,

        PrefilterPacketSeqSet,

        PrefilterPacketSeqCompare,

        PrefilterPacketSeqMatch);

}

static bool PrefilterTcpSeqIsPrefilterable(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_SEQ:

                return true;

        }

    }

    return false;

}

#ifdef UNITTESTS

/**

 * \test DetectSeqSigTest01 tests parses

 */

static int DetectSeqSigTest01(void)

{

    int result = 0;

    DetectEngineCtx *de_ctx = DetectEngineCtxInit();

    if (de_ctx == NULL)

        goto end;

    /* These three are crammed in here as there is no Parse */

    if (SigInit(de_ctx,

                "alert tcp any any -> any any "

                "(msg:\"Testing seq\";seq:foo;sid:1;)") != NULL)

    {

        printf("invalid seq accepted: ");

        goto cleanup;

    }

    if (SigInit(de_ctx,

                "alert tcp any any -> any any "

                "(msg:\"Testing seq\";seq:9999999999;sid:1;)") != NULL)

    {

        printf("overflowing seq accepted: ");

        goto cleanup;

    }

    if (SigInit(de_ctx,

                "alert tcp any any -> any any "

                "(msg:\"Testing seq\";seq:-100;sid:1;)") != NULL)

    {

        printf("negative seq accepted: ");

        goto cleanup;

    }

    result = 1;

cleanup:

    if (de_ctx) {

        SigGroupCleanup(de_ctx);

        SigCleanSignatures(de_ctx);

        DetectEngineCtxFree(de_ctx);

    }

end:

    return result;

}

/**

 * \test DetectSeqSigTest02 tests seq keyword

 */

static int DetectSeqSigTest02(void)

{

    int result = 0;

    uint8_t *buf = (uint8_t *)"Hi all!";

    uint16_t buflen = strlen((char *)buf);

    Packet *p[3];

    p[0] = UTHBuildPacket((uint8_t *)buf, buflen, IPPROTO_TCP);

    p[1] = UTHBuildPacket((uint8_t *)buf, buflen, IPPROTO_TCP);

    p[2] = UTHBuildPacket((uint8_t *)buf, buflen, IPPROTO_ICMP);

    if (p[0] == NULL || p[1] == NULL ||p[2] == NULL)

        goto end;

    /* TCP w/seq=42 */

    p[0]->tcph->th_seq = htonl(42);

    /* TCP w/seq=100 */

    p[1]->tcph->th_seq = htonl(100);

    const char *sigs[2];

    sigs[0]= "alert tcp any any -> any any (msg:\"Testing seq\"; seq:41; sid:1;)";

    sigs[1]= "alert tcp any any -> any any (msg:\"Testing seq\"; seq:42; sid:2;)";

    uint32_t sid[2] = {1, 2};

    uint32_t results[3][2] = {

                              /* packet 0 match sid 1 but should not match sid 2 */

                              {0, 1},

                              /* packet 1 should not match */

                              {0, 0},

                              /* packet 2 should not match */

                              {0, 0} };

    result = UTHGenericTest(p, 3, sigs, sid, (uint32_t *) results, 2);

    UTHFreePackets(p, 3);

end:

    return result;

}

/**

 * \internal

 * \brief This function registers unit tests for DetectSeq

 */

static void DetectSeqRegisterTests(void)

{

    UtRegisterTest("DetectSeqSigTest01", DetectSeqSigTest01);

    UtRegisterTest("DetectSeqSigTest02", DetectSeqSigTest02);

}

#endif /* UNITTESTS */