suricata/src/detect-urilen.c

/* 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 Gurvinder Singh <gurvindersighdahiya@gmail.com>
 *
 * Implements the urilen keyword
 */

#include "suricata-common.h"
#include "app-layer.h"
#include "app-layer-protos.h"
#include "app-layer-htp.h"
#include "util-unittest-helper.h"

#include "detect.h"
#include "detect-parse.h"
#include "detect-engine.h"
#include "detect-engine-state.h"
#include "detect-engine-build.h"
#include "detect-content.h"
#include "detect-engine-uint.h"

#include "detect-urilen.h"
#include "util-debug.h"
#include "util-byte.h"
#include "flow-util.h"
#include "stream-tcp.h"


/*prototypes*/
static int DetectUrilenSetup (DetectEngineCtx *, Signature *, const char *);
static void DetectUrilenFree (DetectEngineCtx *, void *);
#ifdef UNITTESTS
static void DetectUrilenRegisterTests (void);
#endif
static int g_http_uri_buffer_id = 0;
static int g_http_raw_uri_buffer_id = 0;

/**
 * \brief Registration function for urilen: keyword
 */

void DetectUrilenRegister(void)
{
    sigmatch_table[DETECT_URILEN].name = "urilen";
    sigmatch_table[DETECT_URILEN].desc = "match on the length of the HTTP uri";
    sigmatch_table[DETECT_URILEN].url = "/rules/http-keywords.html#urilen";
    sigmatch_table[DETECT_URILEN].Match = NULL;
    sigmatch_table[DETECT_URILEN].Setup = DetectUrilenSetup;
    sigmatch_table[DETECT_URILEN].Free = DetectUrilenFree;
#ifdef UNITTESTS
    sigmatch_table[DETECT_URILEN].RegisterTests = DetectUrilenRegisterTests;
#endif
    sigmatch_table[DETECT_URILEN].flags = SIGMATCH_SUPPORT_FIREWALL;

    g_http_uri_buffer_id = DetectBufferTypeRegister("http_uri");
    g_http_raw_uri_buffer_id = DetectBufferTypeRegister("http_raw_uri");
}

/**
 * \brief This function is used to parse urilen options passed via urilen: keyword
 *
 * \param urilenstr Pointer to the user provided urilen options
 *
 * \retval urilend pointer to DetectUrilenData on success
 * \retval NULL on failure
 */

static DetectUrilenData *DetectUrilenParse (const char *urilenstr)
{
    return SCDetectUrilenParse(urilenstr);
}

/**
 * \brief this function is used to parse urilen data into the current signature
 *
 * \param de_ctx pointer to the Detection Engine Context
 * \param s pointer to the Current Signature
 * \param urilenstr pointer to the user provided urilen options
 *
 * \retval 0 on Success
 * \retval -1 on Failure
 */
static int DetectUrilenSetup (DetectEngineCtx *de_ctx, Signature *s, const char *urilenstr)
{
    SCEnter();
    DetectUrilenData *urilend = NULL;

    if (SCDetectSignatureSetAppProto(s, ALPROTO_HTTP) != 0)
        return -1;

    urilend = DetectUrilenParse(urilenstr);
    if (urilend == NULL)
        goto error;

    if (urilend->raw_buffer) {
        if (SCSigMatchAppendSMToList(de_ctx, s, DETECT_URILEN, (SigMatchCtx *)urilend,
                    g_http_raw_uri_buffer_id) == NULL) {
            goto error;
        }
    } else {
        if (SCSigMatchAppendSMToList(de_ctx, s, DETECT_URILEN, (SigMatchCtx *)urilend,
                    g_http_uri_buffer_id) == NULL) {
            goto error;
        }
    }

    SCReturnInt(0);

error:
    DetectUrilenFree(de_ctx, urilend);
    SCReturnInt(-1);
}

/**
 * \brief this function will free memory associated with DetectUrilenData
 *
 * \param ptr pointer to DetectUrilenData
 */
static void DetectUrilenFree(DetectEngineCtx *de_ctx, void *ptr)
{
    if (ptr == NULL)
        return;

    DetectUrilenData *urilend = (DetectUrilenData *)ptr;
    SCDetectUrilenFree(urilend);
}

/** \brief set prefilter dsize pair
 *  \param s signature to get dsize value from
 */
void DetectUrilenApplyToContent(Signature *s, int list)
{
    for (uint32_t x = 0; x < s->init_data->buffer_index; x++) {
        if (s->init_data->buffers[x].id != (uint32_t)list)
            continue;

        uint16_t high = UINT16_MAX;
        bool found = false;

        for (SigMatch *sm = s->init_data->buffers[x].head; sm != NULL; sm = sm->next) {
            if (sm->type != DETECT_URILEN)
                continue;

            DetectUrilenData *dd = (DetectUrilenData *)sm->ctx;

            switch (dd->du16.mode) {
                case DETECT_UINT_LT:
                    if (dd->du16.arg1 < UINT16_MAX) {
                        high = dd->du16.arg1 + 1;
                    }
                    break;
                case DETECT_UINT_LTE:
                    // fallthrough
                case DETECT_UINT_EQ:
                    high = dd->du16.arg1;
                    break;
                case DETECT_UINT_RA:
                    if (dd->du16.arg2 < UINT16_MAX) {
                        high = dd->du16.arg2 + 1;
                    }
                    break;
                case DETECT_UINT_NE:
                    // fallthrough
                case DETECT_UINT_GTE:
                    // fallthrough
                case DETECT_UINT_GT:
                    high = UINT16_MAX;
                    break;
            }
            found = true;
        }

        // skip 65535 to avoid mismatch on uri > 64k
        if (!found || high == UINT16_MAX)
            return;

        SCLogDebug("high %u", high);

        for (SigMatch *sm = s->init_data->buffers[x].head; sm != NULL; sm = sm->next) {
            if (sm->type != DETECT_CONTENT) {
                continue;
            }
            DetectContentData *cd = (DetectContentData *)sm->ctx;
            if (cd == NULL) {
                continue;
            }

            if (cd->depth == 0 || cd->depth > high) {
                cd->depth = high;
                cd->flags |= DETECT_CONTENT_DEPTH;
                SCLogDebug("updated %u, content %u to have depth %u "
                           "because of urilen.",
                        s->id, cd->id, cd->depth);
            }
        }
    }
}

bool DetectUrilenValidateContent(
        const Signature *s, const char **sigerror, const DetectBufferType *dbt)
{
    for (uint32_t x = 0; x < s->init_data->buffer_index; x++) {
        if (s->init_data->buffers[x].id != (uint32_t)dbt->id)
            continue;
        for (const SigMatch *sm = s->init_data->buffers[x].head; sm != NULL; sm = sm->next) {
            if (sm->type != DETECT_CONTENT) {
                continue;
            }
            DetectContentData *cd = (DetectContentData *)sm->ctx;
            if (cd == NULL) {
                continue;
            }

            if (cd->depth && cd->depth < cd->content_len) {
                *sigerror = "depth or urilen smaller than content len";
                SCLogError("depth or urilen %u smaller "
                           "than content len %u",
                        cd->depth, cd->content_len);
                return false;
            }
        }
    }
    return true;
}

#ifdef UNITTESTS

#include "stream.h"
#include "stream-tcp-private.h"
#include "stream-tcp-reassemble.h"
#include "detect-engine-mpm.h"
#include "app-layer-parser.h"
#include "detect-engine-alert.h"

/** \test   Test the Urilen keyword setup */
static int DetectUrilenParseTest01(void)
{
    DetectUrilenData *urilend = DetectUrilenParse("10");
    FAIL_IF_NULL(urilend);
    FAIL_IF(urilend->du16.arg1 != 10);
    FAIL_IF(urilend->du16.mode != DETECT_UINT_EQ);
    FAIL_IF(urilend->raw_buffer);

    DetectUrilenFree(NULL, urilend);
    PASS;
}

/** \test   Test the Urilen keyword setup */
static int DetectUrilenParseTest02(void)
{
    DetectUrilenData *urilend = DetectUrilenParse(" < 10  ");
    FAIL_IF_NULL(urilend);
    FAIL_IF(urilend->du16.arg1 != 10);
    FAIL_IF(urilend->du16.mode != DETECT_UINT_LT);
    FAIL_IF(urilend->raw_buffer);

    DetectUrilenFree(NULL, urilend);
    PASS;
}

/** \test   Test the Urilen keyword setup */
static int DetectUrilenParseTest03(void)
{
    DetectUrilenData *urilend = DetectUrilenParse(" > 10 ");
    FAIL_IF_NULL(urilend);
    FAIL_IF(urilend->du16.arg1 != 10);
    FAIL_IF(urilend->du16.mode != DETECT_UINT_GT);
    FAIL_IF(urilend->raw_buffer);

    DetectUrilenFree(NULL, urilend);
    PASS;
}

/** \test   Test the Urilen keyword setup */
static int DetectUrilenParseTest04(void)
{
    DetectUrilenData *urilend = DetectUrilenParse(" 5 <> 10 ");
    FAIL_IF_NULL(urilend);
    FAIL_IF(urilend->du16.arg1 != 5);
    FAIL_IF(urilend->du16.arg2 != 10);
    FAIL_IF(urilend->du16.mode != DETECT_UINT_RA);
    FAIL_IF(urilend->raw_buffer);

    DetectUrilenFree(NULL, urilend);
    PASS;
}

/** \test   Test the Urilen keyword setup */
static int DetectUrilenParseTest05(void)
{
    DetectUrilenData *urilend = DetectUrilenParse("5<>10,norm");
    FAIL_IF_NULL(urilend);
    FAIL_IF(urilend->du16.arg1 != 5);
    FAIL_IF(urilend->du16.arg2 != 10);
    FAIL_IF(urilend->du16.mode != DETECT_UINT_RA);
    FAIL_IF(urilend->raw_buffer);

    DetectUrilenFree(NULL, urilend);
    PASS;
}

/** \test   Test the Urilen keyword setup */
static int DetectUrilenParseTest06(void)
{
    DetectUrilenData *urilend = DetectUrilenParse("5<>10,raw");
    FAIL_IF_NULL(urilend);
    FAIL_IF(urilend->du16.arg1 != 5);
    FAIL_IF(urilend->du16.arg2 != 10);
    FAIL_IF(urilend->du16.mode != DETECT_UINT_RA);
    FAIL_IF(!urilend->raw_buffer);

    DetectUrilenFree(NULL, urilend);
    PASS;
}

/** \test   Test the Urilen keyword setup */
static int DetectUrilenParseTest07(void)
{
    DetectUrilenData *urilend = DetectUrilenParse(">10, norm ");
    FAIL_IF_NULL(urilend);
    FAIL_IF(urilend->du16.arg1 != 10);
    FAIL_IF(urilend->du16.mode != DETECT_UINT_GT);
    FAIL_IF(urilend->raw_buffer);

    DetectUrilenFree(NULL, urilend);
    PASS;
}

/** \test   Test the Urilen keyword setup */
static int DetectUrilenParseTest08(void)
{
    DetectUrilenData *urilend = DetectUrilenParse("<10, norm ");
    FAIL_IF_NULL(urilend);
    FAIL_IF(urilend->du16.arg1 != 10);
    FAIL_IF(urilend->du16.mode != DETECT_UINT_LT);
    FAIL_IF(urilend->raw_buffer);

    DetectUrilenFree(NULL, urilend);
    PASS;
}

/** \test   Test the Urilen keyword setup */
static int DetectUrilenParseTest09(void)
{
    DetectUrilenData *urilend = DetectUrilenParse(">10, raw ");
    FAIL_IF_NULL(urilend);
    FAIL_IF(urilend->du16.arg1 != 10);
    FAIL_IF(urilend->du16.mode != DETECT_UINT_GT);
    FAIL_IF(!urilend->raw_buffer);

    DetectUrilenFree(NULL, urilend);
    PASS;
}

/** \test   Test the Urilen keyword setup */
static int DetectUrilenParseTest10(void)
{
    DetectUrilenData *urilend = DetectUrilenParse("<10, raw ");
    FAIL_IF_NULL(urilend);
    FAIL_IF(urilend->du16.arg1 != 10);
    FAIL_IF(urilend->du16.mode != DETECT_UINT_LT);
    FAIL_IF(!urilend->raw_buffer);

    DetectUrilenFree(NULL, urilend);
    PASS;
}

/**
 * \brief this function is used to initialize the detection engine context and
 *        setup the signature with passed values.
 *
 */

static int DetectUrilenInitTest(DetectEngineCtx **de_ctx, Signature **sig,
                                DetectUrilenData **urilend, const char *str)
{
    char fullstr[1024];
    int result = 0;

    *de_ctx = NULL;
    *sig = NULL;

    if (snprintf(fullstr, 1024, "alert ip any any -> any any (msg:\"Urilen "
                                "test\"; urilen:%s; sid:1;)", str) >= 1024) {
        goto end;
    }

    *de_ctx = DetectEngineCtxInit();
    if (*de_ctx == NULL) {
        goto end;
    }

    (*de_ctx)->flags |= DE_QUIET;

    (*de_ctx)->sig_list = SigInit(*de_ctx, fullstr);
    if ((*de_ctx)->sig_list == NULL) {
        goto end;
    }

    *sig = (*de_ctx)->sig_list;

    *urilend = DetectUrilenParse(str);

    result = 1;

end:
    return result;
}

/**
 * \test DetectUrilenSetpTest01 is a test for setting up an valid urilen values
 *       with valid "<>" operator and include spaces arround the given values.
 *       In the test the values are setup with initializing the detection engine
 *       context and setting up the signature itself.
 */

static int DetectUrilenSetpTest01(void)
{
    DetectUrilenData *urilend = NULL;
    Signature *sig = NULL;
    DetectEngineCtx *de_ctx = NULL;

    uint8_t res = DetectUrilenInitTest(&de_ctx, &sig, &urilend, "1 <> 3");
    FAIL_IF(res == 0);
    FAIL_IF_NULL(urilend);
    FAIL_IF_NOT(urilend->du16.arg1 == 1);
    FAIL_IF_NOT(urilend->du16.arg2 == 3);
    FAIL_IF_NOT(urilend->du16.mode == DETECT_UINT_RA);

    DetectUrilenFree(NULL, urilend);
    DetectEngineCtxFree(de_ctx);
    PASS;
}

/** \test Check a signature with given urilen */
static int DetectUrilenSigTest01(void)
{
    Flow f;
    uint8_t httpbuf1[] = "POST /suricata HTTP/1.0\r\n"
                         "Host: foo.bar.tld\r\n"
                         "\r\n";
    uint32_t httplen1 = sizeof(httpbuf1) - 1; /* minus the \0 */
    TcpSession ssn;
    ThreadVars th_v;
    DetectEngineThreadCtx *det_ctx = NULL;
    AppLayerParserThreadCtx *alp_tctx = AppLayerParserThreadCtxAlloc();

    memset(&th_v, 0, sizeof(th_v));
    StatsThreadInit(&th_v.stats);
    memset(&f, 0, sizeof(f));
    memset(&ssn, 0, sizeof(ssn));

    Packet *p = UTHBuildPacket(NULL, 0, IPPROTO_TCP);

    FLOW_INITIALIZE(&f);
    f.protoctx = (void *)&ssn;
    f.proto = IPPROTO_TCP;
    f.flags |= FLOW_IPV4;

    p->flow = &f;
    p->flowflags |= FLOW_PKT_TOSERVER;
    p->flowflags |= FLOW_PKT_ESTABLISHED;
    p->flags |= PKT_HAS_FLOW|PKT_STREAM_EST;
    f.alproto = ALPROTO_HTTP1;

    StreamTcpInitConfig(true);

    DetectEngineCtx *de_ctx = DetectEngineCtxInit();
    FAIL_IF_NULL(de_ctx);
    de_ctx->flags |= DE_QUIET;

    Signature *s = DetectEngineAppendSig(de_ctx, "alert tcp any any -> any any "
                                                 "(msg:\"Testing urilen\"; "
                                                 "urilen: <5; sid:1;)");
    FAIL_IF_NULL(s);
    s = DetectEngineAppendSig(de_ctx, "alert tcp any any -> any any "
                                      "(msg:\"Testing http_method\"; "
                                      "urilen: >5; sid:2;)");
    FAIL_IF_NULL(s);

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

    int r = AppLayerParserParse(
            NULL, alp_tctx, &f, ALPROTO_HTTP1, STREAM_TOSERVER, httpbuf1, httplen1);
    FAIL_IF(r != 0);

    HtpState *htp_state = f.alstate;
    FAIL_IF_NULL(htp_state);

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

    FAIL_IF(PacketAlertCheck(p, 1));
    FAIL_IF(!PacketAlertCheck(p, 2));

    UTHFreePackets(&p, 1);
    FLOW_DESTROY(&f);

    AppLayerParserThreadCtxFree(alp_tctx);
    DetectEngineThreadCtxDeinit(&th_v, (void *)det_ctx);
    DetectEngineCtxFree(de_ctx);
    StreamTcpFreeConfig(true);
    StatsThreadCleanup(&th_v.stats);
    PASS;
}

/**
 * \brief this function registers unit tests for DetectUrilen
 */
void DetectUrilenRegisterTests(void)
{
    UtRegisterTest("DetectUrilenParseTest01", DetectUrilenParseTest01);
    UtRegisterTest("DetectUrilenParseTest02", DetectUrilenParseTest02);
    UtRegisterTest("DetectUrilenParseTest03", DetectUrilenParseTest03);
    UtRegisterTest("DetectUrilenParseTest04", DetectUrilenParseTest04);
    UtRegisterTest("DetectUrilenParseTest05", DetectUrilenParseTest05);
    UtRegisterTest("DetectUrilenParseTest06", DetectUrilenParseTest06);
    UtRegisterTest("DetectUrilenParseTest07", DetectUrilenParseTest07);
    UtRegisterTest("DetectUrilenParseTest08", DetectUrilenParseTest08);
    UtRegisterTest("DetectUrilenParseTest09", DetectUrilenParseTest09);
    UtRegisterTest("DetectUrilenParseTest10", DetectUrilenParseTest10);
    UtRegisterTest("DetectUrilenSetpTest01", DetectUrilenSetpTest01);
    UtRegisterTest("DetectUrilenSigTest01", DetectUrilenSigTest01);
}
#endif /* UNITTESTS */