/* Copyright (C) 2007-2021 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 Pablo Rincon Crespo <pablo.rincon.crespo@gmail.com>

 *

 * Implements the id 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-common.h"

#include "detect-id.h"

#include "flow.h"

#include "flow-var.h"

#include "util-debug.h"

#include "util-byte.h"

#include "util-unittest.h"

#include "util-unittest-helper.h"

/**

 * \brief Regex for parsing "id" option, matching number or "number"

 */

#define PARSE_REGEX  "^\\s*([0-9]{1,5}|\"[0-9]{1,5}\")\\s*$"

static DetectParseRegex parse_regex;

static int DetectIdMatch (DetectEngineThreadCtx *, Packet *,

        const Signature *, const SigMatchCtx *);

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

#ifdef UNITTESTS

static void DetectIdRegisterTests(void);

#endif

void DetectIdFree(DetectEngineCtx *, void *);

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

static bool PrefilterIdIsPrefilterable(const Signature *s);

/**

 * \brief Registration function for keyword: id

 */

void DetectIdRegister (void)

{

    sigmatch_table[DETECT_ID].name = "id";

    sigmatch_table[DETECT_ID].desc = "match on a specific IP ID value";

    sigmatch_table[DETECT_ID].url = "/rules/header-keywords.html#id";

    sigmatch_table[DETECT_ID].Match = DetectIdMatch;

    sigmatch_table[DETECT_ID].Setup = DetectIdSetup;

    sigmatch_table[DETECT_ID].Free  = DetectIdFree;

#ifdef UNITTESTS

    sigmatch_table[DETECT_ID].RegisterTests = DetectIdRegisterTests;

#endif

    sigmatch_table[DETECT_ID].SupportsPrefilter = PrefilterIdIsPrefilterable;

    sigmatch_table[DETECT_ID].SetupPrefilter = PrefilterSetupId;

    DetectSetupParseRegexes(PARSE_REGEX, &parse_regex);

}

/**

 * \brief This function is used to match the specified id on a packet

 *

 * \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 DetectIdData

 *

 * \retval 0 no match

 * \retval 1 match

 */

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

                          const Signature *s, const SigMatchCtx *ctx)

{

    const DetectIdData *id_d = (const DetectIdData *)ctx;

    /**

     * To match a ipv4 packet with a "id" rule

     */

    if (!PKT_IS_IPV4(p) || PKT_IS_PSEUDOPKT(p)) {

        return 0;

    }

    if (id_d->id == IPV4_GET_IPID(p)) {

        SCLogDebug("IPV4 Proto and matched with ip_id: %u.\n",

                    id_d->id);

        return 1;

    }

    return 0;

}

/**

 * \brief This function is used to parse IPV4 ip_id passed via keyword: "id"

 *

 * \param idstr Pointer to the user provided id option

 *

 * \retval id_d pointer to DetectIdData on success

 * \retval NULL on failure

 */

static DetectIdData *DetectIdParse (const char *idstr)

{

    uint16_t temp;

    DetectIdData *id_d = NULL;

    int res = 0;

    size_t pcre2len;

    pcre2_match_data *match = NULL;

    int ret = DetectParsePcreExec(&parse_regex, &match, idstr, 0, 0);

    if (ret < 1 || ret > 3) {

        SCLogError("invalid id option '%s'. The id option "

                   "value must be in the range %u - %u",

                idstr, DETECT_IPID_MIN, DETECT_IPID_MAX);

        goto error;

    }

    char copy_str[128] = "";

    char *tmp_str;

    pcre2len = sizeof(copy_str);

    res = pcre2_substring_copy_bynumber(match, 1, (PCRE2_UCHAR8 *)copy_str, &pcre2len);

    if (res < 0) {

        SCLogError("pcre2_substring_copy_bynumber failed");

        goto error;

    }

    tmp_str = copy_str;

    /* Let's see if we need to scape "'s */

    if (tmp_str[0] == '"')

    {

        tmp_str[strlen(tmp_str) - 1] = '\0';

        tmp_str += 1;

    }

    /* ok, fill the id data */

    if (StringParseUint16(&temp, 10, 0, (const char *)tmp_str) <= 0) {

        SCLogError("invalid id option '%s'", tmp_str);

        goto error;

    }

    /* We have a correct id option */

    id_d = SCMalloc(sizeof(DetectIdData));

    if (unlikely(id_d == NULL))

        goto error;

    id_d->id = temp;

    SCLogDebug("detect-id: will look for ip_id: %u\n", id_d->id);

    pcre2_match_data_free(match);

    return id_d;

error:

    if (match) {

        pcre2_match_data_free(match);

    }

    return NULL;

}

/**

 * \brief this function is used to add the parsed "id" option

 * \brief into the current signature

 *

 * \param de_ctx pointer to the Detection Engine Context

 * \param s pointer to the Current Signature

 * \param idstr pointer to the user provided "id" option

 *

 * \retval 0 on Success

 * \retval -1 on Failure

 */

int DetectIdSetup (DetectEngineCtx *de_ctx, Signature *s, const char *idstr)

{

    DetectIdData *id_d = NULL;

    SigMatch *sm = NULL;

    id_d = DetectIdParse(idstr);

    if (id_d == NULL)

        return -1;

    /* Okay so far so good, lets get this into a SigMatch

     * and put it in the Signature. */

    sm = SigMatchAlloc();

    if (sm == NULL) {

        DetectIdFree(de_ctx, id_d);

        return -1;

    }

    sm->type = DETECT_ID;

    sm->ctx = (SigMatchCtx *)id_d;

    SigMatchAppendSMToList(s, sm, DETECT_SM_LIST_MATCH);

    s->flags |= SIG_FLAG_REQUIRE_PACKET;

    return 0;

}

/**

 * \brief this function will free memory associated with DetectIdData

 *

 * \param id_d pointer to DetectIdData

 */

void DetectIdFree(DetectEngineCtx *de_ctx, void *ptr)

{

    DetectIdData *id_d = (DetectIdData *)ptr;

    SCFree(id_d);

}

/* prefilter code */

static void

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

{

    const PrefilterPacketHeaderCtx *ctx = pectx;

    if (!PKT_IS_IPV4(p) || PKT_IS_PSEUDOPKT(p)) {

        return;

    }

    if (!PrefilterPacketHeaderExtraMatch(ctx, p))

        return;

    if (IPV4_GET_IPID(p) == ctx->v1.u16[0])

    {

        SCLogDebug("packet matches IP id %u", ctx->v1.u16[0]);

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

    }

}

static void

PrefilterPacketIdSet(PrefilterPacketHeaderValue *v, void *smctx)

{

    const DetectIdData *a = smctx;

    v->u16[0] = a->id;

}

static bool

PrefilterPacketIdCompare(PrefilterPacketHeaderValue v, void *smctx)

{

    const DetectIdData *a = smctx;

    if (v.u16[0] == a->id)

        return true;

    return false;

}

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

{

    return PrefilterSetupPacketHeader(de_ctx, sgh, DETECT_ID,

        PrefilterPacketIdSet,

        PrefilterPacketIdCompare,

        PrefilterPacketIdMatch);

}

static bool PrefilterIdIsPrefilterable(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_ID:

                return true;

        }

    }

    return false;

}

#ifdef UNITTESTS /* UNITTESTS */

/**

 * \test DetectIdTestParse01 is a test to make sure that we parse the "id"

 *       option correctly when given valid id option

 */

static int DetectIdTestParse01 (void)

{

    DetectIdData *id_d = DetectIdParse(" 35402 ");

    FAIL_IF_NULL(id_d);

    FAIL_IF_NOT(id_d->id == 35402);

    DetectIdFree(NULL, id_d);

    PASS;

}

/**

 * \test DetectIdTestParse02 is a test to make sure that we parse the "id"

 *       option correctly when given an invalid id option

 *       it should return id_d = NULL

 */

static int DetectIdTestParse02 (void)

{

    DetectIdData *id_d = DetectIdParse("65537");

    FAIL_IF_NOT_NULL(id_d);

    PASS;

}

/**

 * \test DetectIdTestParse03 is a test to make sure that we parse the "id"

 *       option correctly when given an invalid id option

 *       it should return id_d = NULL

 */

static int DetectIdTestParse03 (void)

{

    DetectIdData *id_d = DetectIdParse("12what?");

    FAIL_IF_NOT_NULL(id_d);

    PASS;

}

/**

 * \test DetectIdTestParse04 is a test to make sure that we parse the "id"

 *       option correctly when given valid id option but wrapped with "'s

 */

static int DetectIdTestParse04 (void)

{

    /* yep, look if we trim blank spaces correctly and ignore "'s */

    DetectIdData *id_d = DetectIdParse(" \"35402\" ");

    FAIL_IF_NULL(id_d);

    FAIL_IF_NOT(id_d->id == 35402);

    DetectIdFree(NULL, id_d);

    PASS;

}

/**

 * \test DetectIdTestSig01

 * \brief Test to check "id" keyword with constructed packets

 */

static int DetectIdTestMatch01(void)

{

    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_UDP);

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

    FAIL_IF_NULL(p[0]);

    FAIL_IF_NULL(p[1]);

    FAIL_IF_NULL(p[2]);

    /* TCP IP id = 1234 */

    p[0]->ip4h->ip_id = htons(1234);

    /* UDP IP id = 5678 */

    p[1]->ip4h->ip_id = htons(5678);

    /* UDP IP id = 91011 */

    p[2]->ip4h->ip_id = htons(5101);

    const char *sigs[3];

    sigs[0]= "alert ip any any -> any any (msg:\"Testing id 1\"; id:1234; sid:1;)";

    sigs[1]= "alert ip any any -> any any (msg:\"Testing id 2\"; id:5678; sid:2;)";

    sigs[2]= "alert ip any any -> any any (msg:\"Testing id 3\"; id:5101; sid:3;)";

    uint32_t sid[3] = {1, 2, 3};

    uint32_t results[3][3] = {

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

                              {1, 0, 0},

                              /* packet 1 should not match */

                              {0, 1, 0},

                              /* packet 2 should not match */

                              {0, 0, 1} };

    FAIL_IF_NOT(UTHGenericTest(p, 3, sigs, sid, (uint32_t *)results, 3));

    UTHFreePackets(p, 3);

    PASS;

}

/**

 * \brief this function registers unit tests for DetectId

 */

void DetectIdRegisterTests(void)

{

    UtRegisterTest("DetectIdTestParse01", DetectIdTestParse01);

    UtRegisterTest("DetectIdTestParse02", DetectIdTestParse02);

    UtRegisterTest("DetectIdTestParse03", DetectIdTestParse03);

    UtRegisterTest("DetectIdTestParse04", DetectIdTestParse04);

    UtRegisterTest("DetectIdTestMatch01", DetectIdTestMatch01);

}

#endif /* UNITTESTS */