/* Copyright (C) 2007-2016 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>

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

 *

 * Implements the "ack" keyword.

 */

#include "suricata-common.h"

#include "decode.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-prefilter-common.h"

#include "detect-engine-build.h"

#include "detect-tcp-ack.h"

#include "util-byte.h"

#include "util-unittest.h"

#include "util-unittest-helper.h"

#include "util-debug.h"

/* prototypes */

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

static int DetectAckMatch(DetectEngineThreadCtx *,

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

#ifdef UNITTESTS

static void DetectAckRegisterTests(void);

#endif

static void DetectAckFree(DetectEngineCtx *, void *);

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

static bool PrefilterTcpAckIsPrefilterable(const Signature *s);

void DetectAckRegister(void)

{

    sigmatch_table[DETECT_ACK].name = "tcp.ack";

    sigmatch_table[DETECT_ACK].alias = "ack";

    sigmatch_table[DETECT_ACK].desc = "check for a specific TCP acknowledgement number";

    sigmatch_table[DETECT_ACK].url = "/rules/header-keywords.html#ack";

    sigmatch_table[DETECT_ACK].Match = DetectAckMatch;

    sigmatch_table[DETECT_ACK].Setup = DetectAckSetup;

    sigmatch_table[DETECT_ACK].Free = DetectAckFree;

    sigmatch_table[DETECT_ACK].SupportsPrefilter = PrefilterTcpAckIsPrefilterable;

    sigmatch_table[DETECT_ACK].SetupPrefilter = PrefilterSetupTcpAck;

#ifdef UNITTESTS

    sigmatch_table[DETECT_ACK].RegisterTests = DetectAckRegisterTests;

#endif

}

/**

 * \internal

 * \brief This function is used to match packets with a given Ack 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 DetectAckData

 *

 * \retval 0 no match

 * \retval 1 match

 */

static int DetectAckMatch(DetectEngineThreadCtx *det_ctx,

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

{

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

    /* This is only needed on TCP packets */

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

        return 0;

    }

    return (data->ack == TCP_GET_ACK(p)) ? 1 : 0;

}

/**

 * \internal

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

 *

 * \param de_ctx pointer to the Detection Engine Context

 * \param s pointer to the Current Signature

 * \param m pointer to the Current SigMatch

 * \param optstr pointer to the user provided options

 *

 * \retval 0 on Success

 * \retval -1 on Failure

 */

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

{

    DetectAckData *data = NULL;

    SigMatch *sm = NULL;

    data = SCMalloc(sizeof(DetectAckData));

    if (unlikely(data == NULL))

        goto error;

    sm = SigMatchAlloc();

    if (sm == NULL)

        goto error;

    sm->type = DETECT_ACK;

    if (StringParseUint32(&data->ack, 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 ack option

 *

 * \param data pointer to ack configuration data

 */

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

{

    DetectAckData *data = (DetectAckData *)ptr;

    SCFree(data);

}

/* prefilter code */

static void

PrefilterPacketAckMatch(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_ACK(p) == ctx->v1.u32[0]))

    {

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

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

    }

}

static void

PrefilterPacketAckSet(PrefilterPacketHeaderValue *v, void *smctx)

{

    const DetectAckData *a = smctx;

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

}

static bool

PrefilterPacketAckCompare(PrefilterPacketHeaderValue v, void *smctx)

{

    const DetectAckData *a = smctx;

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

        return true;

    return false;

}

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

{

    return PrefilterSetupPacketHeader(de_ctx, sgh, DETECT_ACK,

        PrefilterPacketAckSet,

        PrefilterPacketAckCompare,

        PrefilterPacketAckMatch);

}

static bool PrefilterTcpAckIsPrefilterable(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_ACK:

                return true;

        }

    }

    return false;

}

#ifdef UNITTESTS

#include "detect-engine-alert.h"

/**

 * \internal

 * \brief This test tests sameip success and failure.

 */

static int DetectAckSigTest01(void)

{

    Packet *p1 = NULL;

    Packet *p2 = NULL;

    Packet *p3 = NULL;

    ThreadVars th_v;

    DetectEngineThreadCtx *det_ctx;

    int result = 0;

    memset(&th_v, 0, sizeof(th_v));

    /* TCP w/ack=42 */

    p1 = UTHBuildPacket(NULL, 0, IPPROTO_TCP);

    p1->tcph->th_ack = htonl(42);

    /* TCP w/ack=100 */

    p2 = UTHBuildPacket(NULL, 0, IPPROTO_TCP);

    p2->tcph->th_ack = htonl(100);

    /* ICMP */

    p3 = UTHBuildPacket(NULL, 0, IPPROTO_ICMP);

    DetectEngineCtx *de_ctx = DetectEngineCtxInit();

    if (de_ctx == NULL) {

        goto end;

    }

    de_ctx->flags |= DE_QUIET;

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

    if (SigInit(de_ctx,

                "alert tcp any any -> any any "

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

    {

        printf("invalid ack accepted: ");

        goto cleanup_engine;

    }

    if (SigInit(de_ctx,

                "alert tcp any any -> any any "

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

    {

        printf("overflowing ack accepted: ");

        goto cleanup_engine;

    }

    if (SigInit(de_ctx,

                "alert tcp any any -> any any "

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

    {

        printf("negative ack accepted: ");

        goto cleanup_engine;

    }

    de_ctx->sig_list = SigInit(de_ctx,

                               "alert tcp any any -> any any "

                               "(msg:\"Testing ack\";ack:41;sid:1;)");

    if (de_ctx->sig_list == NULL) {

        goto cleanup_engine;

    }

    de_ctx->sig_list->next = SigInit(de_ctx,

                                     "alert tcp any any -> any any "

                                     "(msg:\"Testing ack\";ack:42;sid:2;)");

    if (de_ctx->sig_list->next == NULL) {

        goto cleanup_engine;

    }

    SigGroupBuild(de_ctx);

    DetectEngineThreadCtxInit(&th_v, (void *)de_ctx, (void *)&det_ctx);

    SigMatchSignatures(&th_v, de_ctx, det_ctx, p1);

    if (PacketAlertCheck(p1, 1) != 0) {

        printf("sid 1 alerted, but should not have: ");

        goto cleanup;

    }

    if (PacketAlertCheck(p1, 2) == 0) {

        printf("sid 2 did not alert, but should have: ");

        goto cleanup;

    }

    SigMatchSignatures(&th_v, de_ctx, det_ctx, p2);

    if (PacketAlertCheck(p2, 1) != 0) {

        printf("sid 1 alerted, but should not have: ");

        goto cleanup;

    }

    if (PacketAlertCheck(p2, 2) != 0) {

        printf("sid 2 alerted, but should not have: ");

        goto cleanup;

    }

    SigMatchSignatures(&th_v, de_ctx, det_ctx, p3);

    if (PacketAlertCheck(p3, 1) != 0) {

        printf("sid 1 alerted, but should not have: ");

        goto cleanup;

    }

    if (PacketAlertCheck(p3, 2) != 0) {

        printf("sid 2 alerted, but should not have: ");

        goto cleanup;

    }

    result = 1;

cleanup:

    SigGroupCleanup(de_ctx);

    SigCleanSignatures(de_ctx);

    DetectEngineThreadCtxDeinit(&th_v, (void *)det_ctx);

cleanup_engine:

    DetectEngineCtxFree(de_ctx);

end:

    return result;

}

/**

 * \internal

 * \brief This function registers unit tests for DetectAck

 */

static void DetectAckRegisterTests(void)

{

    UtRegisterTest("DetectAckSigTest01", DetectAckSigTest01);

}

#endif /* UNITTESTS */