/* 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 Jeff Lucovsky <jeff@lucovsky.org>

 *

 * Implements the dotprefix transformation

 */

#include "suricata-common.h"

#include "detect.h"

#include "detect-engine.h"

#include "detect-engine-prefilter.h"

#include "detect-parse.h"

#include "detect-transform-dotprefix.h"

#include "detect-engine-build.h"

#include "util-unittest.h"

#include "util-print.h"

#include "util-memrchr.h"

#include "util-memcpy.h"

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

#ifdef UNITTESTS

static void DetectTransformDotPrefixRegisterTests(void);

#endif

static void TransformDotPrefix(InspectionBuffer *buffer, void *options);

void DetectTransformDotPrefixRegister(void)

{

    sigmatch_table[DETECT_TRANSFORM_DOTPREFIX].name = "dotprefix";

    sigmatch_table[DETECT_TRANSFORM_DOTPREFIX].desc =

        "modify buffer to extract the dotprefix";

    sigmatch_table[DETECT_TRANSFORM_DOTPREFIX].url =

        "/rules/transforms.html#dotprefix";

    sigmatch_table[DETECT_TRANSFORM_DOTPREFIX].Transform = TransformDotPrefix;

    sigmatch_table[DETECT_TRANSFORM_DOTPREFIX].Setup = DetectTransformDotPrefixSetup;

#ifdef UNITTESTS

    sigmatch_table[DETECT_TRANSFORM_DOTPREFIX].RegisterTests =

        DetectTransformDotPrefixRegisterTests;

#endif

    sigmatch_table[DETECT_TRANSFORM_DOTPREFIX].flags |= SIGMATCH_NOOPT;

}

/**

 *  \internal

 *  \brief Extract the dotprefix, if any, the last pattern match, either content or uricontent

 *  \param det_ctx detection engine ctx

 *  \param s signature

 *  \param nullstr should be null

 *  \retval 0 ok

 *  \retval -1 failure

 */

static int DetectTransformDotPrefixSetup (DetectEngineCtx *de_ctx, Signature *s, const char *nullstr)

{

    SCEnter();

    int r = DetectSignatureAddTransform(s, DETECT_TRANSFORM_DOTPREFIX, NULL);

    SCReturnInt(r);

}

/**

 * \brief Return the dotprefix, if any, in the last pattern match.

 *

 * Input values are modified by prefixing with a ".".

 *

 * Rule: "alert dns any any -> any any (dns_query; dotprefix; content:".google.com"; sid:1;)"

 * 1. hello.google.com --> match

 * 2. hey.agoogle.com --> no match

 * 3. agoogle.com --> no match

 * 4. something.google.com.au --> match

 * 5. google.com --> match

 *

 * To match on the dotprefix only:

 * Rule: "alert dns any any -> any any (dns_query; dotprefix; content:".google.com"; endswith; sid:1;)"

 *

 * 1. hello.google.com --> match

 * 2. hey.agoogle.com --> no match

 * 3. agoogle.com --> no match

 * 4. something.google.com.au --> no match

 * 5. google.com --> match

 *

 * To match on a TLD:

 * Rule: "alert dns any any -> any any (dns_query; dotprefix; content:".co.uk"; endswith; sid:1;)"

 *

 * 1. hello.google.com --> no match

 * 2. hey.agoogle.com --> no match

 * 3. agoogle.com --> no match

 * 4. something.google.co.uk --> match

 * 5. google.com --> no match

 */

static void TransformDotPrefix(InspectionBuffer *buffer, void *options)

{

    const size_t input_len = buffer->inspect_len;

    if (input_len) {

        // For the leading '.'

        uint8_t *output = InspectionBufferCheckAndExpand(buffer, input_len + 1);

        if (output == NULL) {

            return;

        }

        memmove(&output[1], buffer->inspect, input_len);

        output[0] = '.';

        InspectionBufferTruncate(buffer, input_len + 1);

    }

}

#ifdef UNITTESTS

static int DetectTransformDotPrefixTest01(void)

{

    const uint8_t *input = (const uint8_t *)"example.com";

    uint32_t input_len = strlen((char *)input);

    const char *result = ".example.com";

    uint32_t result_len = strlen((char *)result);

    InspectionBuffer buffer;

    InspectionBufferInit(&buffer, input_len);

    InspectionBufferSetup(NULL, -1, &buffer, input, input_len);

    PrintRawDataFp(stdout, buffer.inspect, buffer.inspect_len);

    TransformDotPrefix(&buffer, NULL);

    PrintRawDataFp(stdout, buffer.inspect, buffer.inspect_len);

    FAIL_IF_NOT(buffer.inspect_len == result_len);

    FAIL_IF_NOT(strncmp(result, (const char *)buffer.inspect, result_len) == 0);

    InspectionBufferFree(&buffer);

    PASS;

}

static int DetectTransformDotPrefixTest02(void)

{

    const uint8_t *input = (const uint8_t *)"hello.example.com";

    uint32_t input_len = strlen((char *)input);

    const char *result = ".hello.example.com";

    uint32_t result_len = strlen((char *)result);

    InspectionBuffer buffer;

    InspectionBufferInit(&buffer, input_len);

    InspectionBufferSetup(NULL, -1, &buffer, input, input_len);

    PrintRawDataFp(stdout, buffer.inspect, buffer.inspect_len);

    TransformDotPrefix(&buffer, NULL);

    PrintRawDataFp(stdout, buffer.inspect, buffer.inspect_len);

    FAIL_IF_NOT(buffer.inspect_len == result_len);

    FAIL_IF_NOT(strncmp(result, (const char *)buffer.inspect, result_len) == 0);

    InspectionBufferFree(&buffer);

    PASS;

}

static int DetectTransformDotPrefixTest03(void)

{

    const char rule[] = "alert dns any any -> any any (dns.query; dotprefix; content:\".google.com\"; sid:1;)";

    ThreadVars th_v;

    DetectEngineThreadCtx *det_ctx = NULL;

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

    DetectEngineCtx *de_ctx = DetectEngineCtxInit();

    FAIL_IF_NULL(de_ctx);

    Signature *s = DetectEngineAppendSig(de_ctx, rule);

    FAIL_IF_NULL(s);

    SigGroupBuild(de_ctx);

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

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

    DetectEngineCtxFree(de_ctx);

    PASS;

}

static void DetectTransformDotPrefixRegisterTests(void)

{

    UtRegisterTest("DetectTransformDotPrefixTest01", DetectTransformDotPrefixTest01);

    UtRegisterTest("DetectTransformDotPrefixTest02", DetectTransformDotPrefixTest02);

    UtRegisterTest("DetectTransformDotPrefixTest03", DetectTransformDotPrefixTest03);

}

#endif