detect-http-header.c

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/* Copyright (C) 2007-2018 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.
 */

/**
 * \ingroup httplayer
 *
 * @{
 */


/**
 * \file
 *
 * \author Pablo Rincon <pablo.rincon.crespo@gmail.com>
 *
 * Implements support for http_header keyword.
 */

#include "suricata-common.h"
#include "threads.h"
#include "decode.h"

#include "detect.h"
#include "detect-parse.h"
#include "detect-engine.h"
#include "detect-engine-mpm.h"
#include "detect-engine-state.h"
#include "detect-engine-prefilter.h"
#include "detect-engine-content-inspection.h"
#include "detect-content.h"
#include "detect-pcre.h"

#include "util-debug.h"
#include "util-print.h"
#include "util-memcmp.h"

#include "app-layer.h"
#include "app-layer-parser.h"

#include "app-layer-htp.h"
#include "detect-http-header.h"
#include "detect-http-header-common.h"

static int DetectHttpHeaderSetup(DetectEngineCtx *, Signature *, const char *);
#ifdef UNITTESTS
static void DetectHttpHeaderRegisterTests(void);
#endif
static int g_http_header_buffer_id = 0;
static int g_keyword_thread_id = 0;

#define BUFFER_TX_STEP      4
#define BUFFER_SIZE_STEP    1024
static HttpHeaderThreadDataConfig g_td_config = { BUFFER_TX_STEP, BUFFER_SIZE_STEP };

static uint8_t *GetBufferForTX(htp_tx_t *tx, uint64_t tx_id,
        DetectEngineThreadCtx *det_ctx,
        Flow *f, uint8_t flags, uint32_t *buffer_len)
{
    *buffer_len = 0;

    HttpHeaderThreadData *hdr_td = NULL;
    HttpHeaderBuffer *buf = HttpHeaderGetBufferSpaceForTXID(det_ctx, f, flags,
            tx_id, g_keyword_thread_id, &hdr_td);
    if (unlikely(buf == NULL)) {
        return NULL;
    } else if (buf->len > 0) {
        /* already filled buf, reuse */
        *buffer_len = buf->len;
        return buf->buffer;
    }

    htp_table_t *headers;
    if (flags & STREAM_TOSERVER) {
        if (AppLayerParserGetStateProgress(IPPROTO_TCP, ALPROTO_HTTP, tx, flags) <= HTP_REQUEST_HEADERS)
            return NULL;
        headers = tx->request_headers;
    } else {
        if (AppLayerParserGetStateProgress(IPPROTO_TCP, ALPROTO_HTTP, tx, flags) <= HTP_RESPONSE_HEADERS)
            return NULL;
        headers = tx->response_headers;
    }
    if (headers == NULL)
        return NULL;

    size_t i = 0;
    size_t no_of_headers = htp_table_size(headers);
    for (; i < no_of_headers; i++) {
        htp_header_t *h = htp_table_get_index(headers, i, NULL);
        size_t size1 = bstr_size(h->name);
        size_t size2 = bstr_size(h->value);

        if (flags & STREAM_TOSERVER) {
            if (size1 == 6 &&
                SCMemcmpLowercase("cookie", bstr_ptr(h->name), 6) == 0) {
                continue;
            }
        } else {
            if (size1 == 10 &&
                SCMemcmpLowercase("set-cookie", bstr_ptr(h->name), 10) == 0) {
                continue;
            }
        }

        size_t size = size1 + size2 + 4;
#if 0
        if (i + 1 == no_of_headers)
            size += 2;
#endif
        if (size + buf->len > buf->size) {
            if (HttpHeaderExpandBuffer(hdr_td, buf, size) != 0) {
                return NULL;
            }
        }

        memcpy(buf->buffer + buf->len, bstr_ptr(h->name), bstr_size(h->name));
        buf->len += bstr_size(h->name);
        buf->buffer[buf->len++] = ':';
        buf->buffer[buf->len++] = ' ';
        memcpy(buf->buffer + buf->len, bstr_ptr(h->value), bstr_size(h->value));
        buf->len += bstr_size(h->value);
        buf->buffer[buf->len++] = '\r';
        buf->buffer[buf->len++] = '\n';
#if 0 // looks like this breaks existing rules
        if (i + 1 == no_of_headers) {
            buf->buffer[buf->len++] = '\r';
            buf->buffer[buf->len++] = '\n';
        }
#endif
    }

    *buffer_len = buf->len;
    return buf->buffer;
}

/** \internal
 *  \brief custom inspect function to utilize the cached headers
 */
static int DetectEngineInspectBufferHttpHeader(
        DetectEngineCtx *de_ctx, DetectEngineThreadCtx *det_ctx,
        const DetectEngineAppInspectionEngine *engine,
        const Signature *s,
        Flow *f, uint8_t flags, void *alstate, void *txv, uint64_t tx_id)
{
    SCEnter();

    const int list_id = engine->sm_list;
    InspectionBuffer *buffer = InspectionBufferGet(det_ctx, list_id);
    if (buffer->inspect == NULL) {
        SCLogDebug("setting up inspect buffer %d", list_id);

        /* if prefilter didn't already run, we need to consider transformations */
        const DetectEngineTransforms *transforms = NULL;
        if (!engine->mpm) {
            transforms = engine->v2.transforms;
        }

        uint32_t rawdata_len = 0;
        uint8_t *rawdata = GetBufferForTX(txv, tx_id, det_ctx,
                f, flags, &rawdata_len);
        if (rawdata_len == 0) {
            SCLogDebug("no data");
            goto end;
        }
        /* setup buffer and apply transforms */
        InspectionBufferSetup(buffer, rawdata, rawdata_len);
        InspectionBufferApplyTransforms(buffer, transforms);
    }

    const uint32_t data_len = buffer->inspect_len;
    const uint8_t *data = buffer->inspect;
    const uint64_t offset = buffer->inspect_offset;

    det_ctx->discontinue_matching = 0;
    det_ctx->buffer_offset = 0;
    det_ctx->inspection_recursion_counter = 0;

    /* Inspect all the uricontents fetched on each
     * transaction at the app layer */
    int r = DetectEngineContentInspection(de_ctx, det_ctx, s, engine->smd,
            NULL, f, (uint8_t *)data, data_len, offset,
            DETECT_CI_FLAGS_SINGLE, DETECT_ENGINE_CONTENT_INSPECTION_MODE_STATE);
    SCLogDebug("r = %d", r);
    if (r == 1) {
        return DETECT_ENGINE_INSPECT_SIG_MATCH;
    }
end:
    if (flags & STREAM_TOSERVER) {
        if (AppLayerParserGetStateProgress(IPPROTO_TCP, ALPROTO_HTTP, txv, flags) > HTP_REQUEST_HEADERS)
            return DETECT_ENGINE_INSPECT_SIG_CANT_MATCH;
    } else {
        if (AppLayerParserGetStateProgress(IPPROTO_TCP, ALPROTO_HTTP, txv, flags) > HTP_RESPONSE_HEADERS)
            return DETECT_ENGINE_INSPECT_SIG_CANT_MATCH;
    }
    return DETECT_ENGINE_INSPECT_SIG_NO_MATCH;
}

typedef struct PrefilterMpmHttpHeaderCtx {
    int list_id;
    const MpmCtx *mpm_ctx;
    const DetectEngineTransforms *transforms;
} PrefilterMpmHttpHeaderCtx;

/** \brief Generic Mpm prefilter callback
 *
 *  \param det_ctx detection engine thread ctx
 *  \param p packet to inspect
 *  \param f flow to inspect
 *  \param txv tx to inspect
 *  \param pectx inspection context
 */
static void PrefilterMpmHttpHeader(DetectEngineThreadCtx *det_ctx,
        const void *pectx,
        Packet *p, Flow *f, void *txv,
        const uint64_t idx, const uint8_t flags)
{
    SCEnter();

    const PrefilterMpmHttpHeaderCtx *ctx = pectx;
    const MpmCtx *mpm_ctx = ctx->mpm_ctx;
    SCLogDebug("running on list %d", ctx->list_id);

    const int list_id = ctx->list_id;
    InspectionBuffer *buffer = InspectionBufferGet(det_ctx, list_id);
    if (buffer->inspect == NULL) {
        uint32_t rawdata_len = 0;
        uint8_t *rawdata = GetBufferForTX(txv, idx, det_ctx,
                f, flags, &rawdata_len);
        if (rawdata_len == 0)
            return;

        /* setup buffer and apply transforms */
        InspectionBufferSetup(buffer, rawdata, rawdata_len);
        InspectionBufferApplyTransforms(buffer, ctx->transforms);
    }

    const uint32_t data_len = buffer->inspect_len;
    const uint8_t *data = buffer->inspect;

    SCLogDebug("mpm'ing buffer:");
    //PrintRawDataFp(stdout, data, data_len);

    if (data != NULL && data_len >= mpm_ctx->minlen) {
        (void)mpm_table[mpm_ctx->mpm_type].Search(mpm_ctx,
                &det_ctx->mtcu, &det_ctx->pmq, data, data_len);
    }
}

static void PrefilterMpmHttpTrailer(DetectEngineThreadCtx *det_ctx,
        const void *pectx,
        Packet *p, Flow *f, void *txv,
        const uint64_t idx, const uint8_t flags)
{
    SCEnter();

    htp_tx_t *tx = txv;
    const HtpTxUserData *htud = (const HtpTxUserData *)htp_tx_get_user_data(tx);
    /* if the request wasn't flagged as having a trailer, we skip */
    if (htud && (
            ((flags & STREAM_TOSERVER) && !htud->request_has_trailers) ||
            ((flags & STREAM_TOCLIENT) && !htud->response_has_trailers))) {
        SCReturn;
    }
    PrefilterMpmHttpHeader(det_ctx, pectx, p, f, txv, idx, flags);
    SCReturn;
}

static void PrefilterMpmHttpHeaderFree(void *ptr)
{
    SCFree(ptr);
}

static int PrefilterMpmHttpHeaderRequestRegister(DetectEngineCtx *de_ctx,
        SigGroupHead *sgh, MpmCtx *mpm_ctx,
        const DetectBufferMpmRegistery *mpm_reg, int list_id)
{
    SCEnter();

    /* header */
    PrefilterMpmHttpHeaderCtx *pectx = SCCalloc(1, sizeof(*pectx));
    if (pectx == NULL)
        return -1;
    pectx->list_id = list_id;
    pectx->mpm_ctx = mpm_ctx;
    pectx->transforms = &mpm_reg->transforms;

    int r = PrefilterAppendTxEngine(de_ctx, sgh, PrefilterMpmHttpHeader,
            mpm_reg->app_v2.alproto, HTP_REQUEST_HEADERS,
            pectx, PrefilterMpmHttpHeaderFree, mpm_reg->pname);
    if (r != 0) {
        SCFree(pectx);
        return r;
    }

    /* trailer */
    pectx = SCCalloc(1, sizeof(*pectx));
    if (pectx == NULL)
        return -1;
    pectx->list_id = list_id;
    pectx->mpm_ctx = mpm_ctx;
    pectx->transforms = &mpm_reg->transforms;

    r = PrefilterAppendTxEngine(de_ctx, sgh, PrefilterMpmHttpTrailer,
            mpm_reg->app_v2.alproto, HTP_REQUEST_TRAILER,
            pectx, PrefilterMpmHttpHeaderFree, mpm_reg->pname);
    if (r != 0) {
        SCFree(pectx);
    }
    return r;
}

static int PrefilterMpmHttpHeaderResponseRegister(DetectEngineCtx *de_ctx,
        SigGroupHead *sgh, MpmCtx *mpm_ctx,
        const DetectBufferMpmRegistery *mpm_reg, int list_id)
{
    SCEnter();

    /* header */
    PrefilterMpmHttpHeaderCtx *pectx = SCCalloc(1, sizeof(*pectx));
    if (pectx == NULL)
        return -1;
    pectx->list_id = list_id;
    pectx->mpm_ctx = mpm_ctx;
    pectx->transforms = &mpm_reg->transforms;

    int r = PrefilterAppendTxEngine(de_ctx, sgh, PrefilterMpmHttpHeader,
            mpm_reg->app_v2.alproto, HTP_RESPONSE_HEADERS,
            pectx, PrefilterMpmHttpHeaderFree, mpm_reg->pname);
    if (r != 0) {
        SCFree(pectx);
        return r;
    }

    /* trailer */
    pectx = SCCalloc(1, sizeof(*pectx));
    if (pectx == NULL)
        return -1;
    pectx->list_id = list_id;
    pectx->mpm_ctx = mpm_ctx;
    pectx->transforms = &mpm_reg->transforms;

    r = PrefilterAppendTxEngine(de_ctx, sgh, PrefilterMpmHttpTrailer,
            mpm_reg->app_v2.alproto, HTP_RESPONSE_TRAILER,
            pectx, PrefilterMpmHttpHeaderFree, mpm_reg->pname);
    if (r != 0) {
        SCFree(pectx);
    }
    return r;
}

/**
 * \brief The setup function for the http_header keyword for a signature.
 *
 * \param de_ctx Pointer to the detection engine context.
 * \param s      Pointer to signature for the current Signature being parsed
 *               from the rules.
 * \param m      Pointer to the head of the SigMatchs for the current rule
 *               being parsed.
 * \param arg    Pointer to the string holding the keyword value.
 *
 * \retval  0 On success.
 * \retval -1 On failure.
 */
static int DetectHttpHeaderSetup(DetectEngineCtx *de_ctx, Signature *s, const char *arg)
{
    return DetectEngineContentModifierBufferSetup(de_ctx, s, arg,
                                                  DETECT_AL_HTTP_HEADER,
                                                  g_http_header_buffer_id,
                                                  ALPROTO_HTTP);
}

/**
 * \brief this function setup the http.header keyword used in the rule
 *
 * \param de_ctx   Pointer to the Detection Engine Context
 * \param s        Pointer to the Signature to which the current keyword belongs
 * \param str      Should hold an empty string always
 *
 * \retval 0       On success
 */
static int DetectHttpHeaderSetupSticky(DetectEngineCtx *de_ctx, Signature *s, const char *str)
{
    if (DetectBufferSetActiveList(s, g_http_header_buffer_id) < 0)
        return -1;
    if (DetectSignatureSetAppProto(s, ALPROTO_HTTP) < 0)
        return -1;
    return 0;
}

/**
 * \brief Registers the keyword handlers for the "http_header" keyword.
 */
void DetectHttpHeaderRegister(void)
{
    /* http_header content modifier */
    sigmatch_table[DETECT_AL_HTTP_HEADER].name = "http_header";
    sigmatch_table[DETECT_AL_HTTP_HEADER].desc = "content modifier to match only on the HTTP header-buffer";
    sigmatch_table[DETECT_AL_HTTP_HEADER].url = DOC_URL DOC_VERSION "/rules/http-keywords.html#http-header-and-http-raw-header";
    sigmatch_table[DETECT_AL_HTTP_HEADER].Setup = DetectHttpHeaderSetup;
#ifdef UNITTESTS
    sigmatch_table[DETECT_AL_HTTP_HEADER].RegisterTests = DetectHttpHeaderRegisterTests;
#endif
    sigmatch_table[DETECT_AL_HTTP_HEADER].flags |= SIGMATCH_NOOPT ;
    sigmatch_table[DETECT_AL_HTTP_HEADER].flags |= SIGMATCH_INFO_CONTENT_MODIFIER;
    sigmatch_table[DETECT_AL_HTTP_HEADER].alternative = DETECT_HTTP_HEADER;

    /* http.header sticky buffer */
    sigmatch_table[DETECT_HTTP_HEADER].name = "http.header";
    sigmatch_table[DETECT_HTTP_HEADER].desc = "sticky buffer to match on the normalized HTTP header-buffer";
    sigmatch_table[DETECT_HTTP_HEADER].url = DOC_URL DOC_VERSION "/rules/http-keywords.html#http-header";
    sigmatch_table[DETECT_HTTP_HEADER].Setup = DetectHttpHeaderSetupSticky;
    sigmatch_table[DETECT_HTTP_HEADER].flags |= SIGMATCH_NOOPT;
    sigmatch_table[DETECT_HTTP_HEADER].flags |= SIGMATCH_INFO_STICKY_BUFFER;

    DetectAppLayerInspectEngineRegister2("http_header", ALPROTO_HTTP,
            SIG_FLAG_TOSERVER, HTP_REQUEST_HEADERS,
            DetectEngineInspectBufferHttpHeader, NULL);
    DetectAppLayerMpmRegister2("http_header", SIG_FLAG_TOSERVER, 2,
            PrefilterMpmHttpHeaderRequestRegister, NULL, ALPROTO_HTTP,
            0); /* not used, registered twice: HEADERS/TRAILER */

    DetectAppLayerInspectEngineRegister2("http_header", ALPROTO_HTTP,
            SIG_FLAG_TOCLIENT, HTP_RESPONSE_HEADERS,
            DetectEngineInspectBufferHttpHeader, NULL);
    DetectAppLayerMpmRegister2("http_header", SIG_FLAG_TOCLIENT, 2,
            PrefilterMpmHttpHeaderResponseRegister, NULL, ALPROTO_HTTP,
            0); /* not used, registered twice: HEADERS/TRAILER */

    DetectBufferTypeSetDescriptionByName("http_header",
            "http headers");

    g_http_header_buffer_id = DetectBufferTypeGetByName("http_header");

    g_keyword_thread_id = DetectRegisterThreadCtxGlobalFuncs("http_header",
            HttpHeaderThreadDataInit, &g_td_config, HttpHeaderThreadDataFree);
}

/************************************Unittests*********************************/

#ifdef UNITTESTS
#include "tests/detect-http-header.c"
#endif

/**
 * @}
 */