/* 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 Pablo Rincon Crespo <pablo.rincon.crespo@gmail.com>

 *

 * Implements the window keyword.

 */

#include "suricata-common.h"

#include "decode.h"

#include "detect.h"

#include "detect-parse.h"

#include "detect-tcp-window.h"

#include "flow.h"

#include "flow-var.h"

#include "util-debug.h"

#include "util-unittest.h"

#include "util-unittest-helper.h"

#include "util-byte.h"

/**

 * \brief Regex for parsing our window option

 */

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

static DetectParseRegex parse_regex;

static int DetectWindowMatch(DetectEngineThreadCtx *, Packet *,

        const Signature *, const SigMatchCtx *);

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

#ifdef UNITTESTS

static void DetectWindowRegisterTests(void);

#endif

void DetectWindowFree(DetectEngineCtx *, void *);

/**

 * \brief Registration function for window: keyword

 */

void DetectWindowRegister (void)

{

    sigmatch_table[DETECT_WINDOW].name = "tcp.window";

    sigmatch_table[DETECT_WINDOW].alias = "window";

    sigmatch_table[DETECT_WINDOW].desc = "check for a specific TCP window size";

    sigmatch_table[DETECT_WINDOW].url = "/rules/header-keywords.html#window";

    sigmatch_table[DETECT_WINDOW].Match = DetectWindowMatch;

    sigmatch_table[DETECT_WINDOW].Setup = DetectWindowSetup;

    sigmatch_table[DETECT_WINDOW].Free  = DetectWindowFree;

#ifdef UNITTESTS

    sigmatch_table[DETECT_WINDOW].RegisterTests = DetectWindowRegisterTests;

#endif

    DetectSetupParseRegexes(PARSE_REGEX, &parse_regex);

}

/**

 * \brief This function is used to match the window size 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 DetectWindowData

 *

 * \retval 0 no match

 * \retval 1 match

 */

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

        const Signature *s, const SigMatchCtx *ctx)

{

    const DetectWindowData *wd = (const DetectWindowData *)ctx;

    if ( !(PKT_IS_TCP(p)) || wd == NULL || PKT_IS_PSEUDOPKT(p)) {

        return 0;

    }

    if ( (!wd->negated && wd->size == TCP_GET_WINDOW(p)) || (wd->negated && wd->size != TCP_GET_WINDOW(p))) {

        return 1;

    }

    return 0;

}

/**

 * \brief This function is used to parse window options passed via window: keyword

 *

 * \param de_ctx Pointer to the detection engine context

 * \param windowstr Pointer to the user provided window options (negation! and size)

 *

 * \retval wd pointer to DetectWindowData on success

 * \retval NULL on failure

 */

static DetectWindowData *DetectWindowParse(DetectEngineCtx *de_ctx, const char *windowstr)

{

    DetectWindowData *wd = NULL;

    int res = 0;

    size_t pcre2len;

    pcre2_match_data *match = NULL;

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

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

        SCLogError("pcre_exec parse error, ret %" PRId32 ", string %s", ret, windowstr);

        goto error;

    }

    wd = SCMalloc(sizeof(DetectWindowData));

    if (unlikely(wd == NULL))

        goto error;

    if (ret > 1) {

        char copy_str[128] = "";

        pcre2len = sizeof(copy_str);

        res = SC_Pcre2SubstringCopy(match, 1, (PCRE2_UCHAR8 *)copy_str, &pcre2len);

        if (res < 0) {

            SCLogError("pcre2_substring_copy_bynumber failed");

            goto error;

        }

        /* Detect if it's negated */

        if (copy_str[0] == '!')

            wd->negated = 1;

        else

            wd->negated = 0;

        if (ret > 2) {

            pcre2len = sizeof(copy_str);

            res = pcre2_substring_copy_bynumber(match, 2, (PCRE2_UCHAR8 *)copy_str, &pcre2len);

            if (res < 0) {

                SCLogError("pcre2_substring_copy_bynumber failed");

                goto error;

            }

            /* Get the window size if it's a valid value (in packets, we

             * should alert if this doesn't happen from decode) */

            if (StringParseUint16(&wd->size, 10, 0, copy_str) < 0) {

                goto error;

            }

        }

    }

    pcre2_match_data_free(match);

    return wd;

error:

    if (match) {

        pcre2_match_data_free(match);

    }

    if (wd != NULL)

        DetectWindowFree(de_ctx, wd);

    return NULL;

}

/**

 * \brief this function is used to add the parsed window sizedata into the current signature

 *

 * \param de_ctx pointer to the Detection Engine Context

 * \param s pointer to the Current Signature

 * \param windowstr pointer to the user provided window options

 *

 * \retval 0 on Success

 * \retval -1 on Failure

 */

static int DetectWindowSetup (DetectEngineCtx *de_ctx, Signature *s, const char *windowstr)

{

    DetectWindowData *wd = NULL;

    SigMatch *sm = NULL;

    wd = DetectWindowParse(de_ctx, windowstr);

    if (wd == NULL) goto error;

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

     * and put it in the Signature. */

    sm = SigMatchAlloc();

    if (sm == NULL)

        goto error;

    sm->type = DETECT_WINDOW;

    sm->ctx = (SigMatchCtx *)wd;

    SigMatchAppendSMToList(s, sm, DETECT_SM_LIST_MATCH);

    s->flags |= SIG_FLAG_REQUIRE_PACKET;

    return 0;

error:

    if (wd != NULL) DetectWindowFree(de_ctx, wd);

    if (sm != NULL) SCFree(sm);

    return -1;

}

/**

 * \brief this function will free memory associated with DetectWindowData

 *

 * \param wd pointer to DetectWindowData

 */

void DetectWindowFree(DetectEngineCtx *de_ctx, void *ptr)

{

    DetectWindowData *wd = (DetectWindowData *)ptr;

    SCFree(wd);

}

#ifdef UNITTESTS /* UNITTESTS */

/**

 * \test DetectWindowTestParse01 is a test to make sure that we set the size correctly

 *  when given valid window opt

 */

static int DetectWindowTestParse01 (void)

{

    DetectWindowData *wd = NULL;

    wd = DetectWindowParse(NULL, "35402");

    FAIL_IF_NULL(wd);

    FAIL_IF_NOT(wd->size == 35402);

    DetectWindowFree(NULL, wd);

    PASS;

}

/**

 * \test DetectWindowTestParse02 is a test for setting the window opt negated

 */

static int DetectWindowTestParse02 (void)

{

    DetectWindowData *wd = NULL;

    wd = DetectWindowParse(NULL, "!35402");

    FAIL_IF_NULL(wd);

    FAIL_IF_NOT(wd->negated == 1);

    FAIL_IF_NOT(wd->size == 35402);

    DetectWindowFree(NULL, wd);

    PASS;

}

/**

 * \test DetectWindowTestParse03 is a test to check for an empty value

 */

static int DetectWindowTestParse03 (void)

{

    DetectWindowData *wd = NULL;

    wd = DetectWindowParse(NULL, "");

    FAIL_IF_NOT_NULL(wd);

    DetectWindowFree(NULL, wd);

    PASS;

}

/**

 * \test DetectWindowTestParse03 is a test to check for a big value

 */

static int DetectWindowTestParse04 (void)

{

    DetectWindowData *wd = NULL;

    wd = DetectWindowParse(NULL, "1235402");

    FAIL_IF_NOT_NULL(wd);

    DetectWindowFree(NULL, wd);

    PASS;

}

/**

 * \test DetectWindowTestPacket01 is a test to check window with constructed packets

 */

static int DetectWindowTestPacket01 (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_TCP);

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

    FAIL_IF(p[0] == NULL || p[1] == NULL || p[2] == NULL);

    /* TCP wwindow = 40 */

    p[0]->tcph->th_win = htons(40);

    /* TCP window = 41 */

    p[1]->tcph->th_win = htons(41);

    const char *sigs[2];

    sigs[0]= "alert tcp any any -> any any (msg:\"Testing window 1\"; window:40; sid:1;)";

    sigs[1]= "alert tcp any any -> any any (msg:\"Testing window 2\"; window:41; sid:2;)";

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

    uint32_t results[3][2] = {

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

                              {1, 0},

                              /* packet 1 should not match */

                              {0, 1},

                              /* packet 2 should not match */

                              {0, 0} };

    FAIL_IF(UTHGenericTest(p, 3, sigs, sid, (uint32_t *)results, 2) == 0);

    UTHFreePackets(p, 3);

    PASS;

}

/**

 * \brief this function registers unit tests for DetectWindow

 */

void DetectWindowRegisterTests(void)

{

    UtRegisterTest("DetectWindowTestParse01", DetectWindowTestParse01);

    UtRegisterTest("DetectWindowTestParse02", DetectWindowTestParse02);

    UtRegisterTest("DetectWindowTestParse03", DetectWindowTestParse03);

    UtRegisterTest("DetectWindowTestParse04", DetectWindowTestParse04);

    UtRegisterTest("DetectWindowTestPacket01", DetectWindowTestPacket01);

}

#endif /* UNITTESTS */