suricata/src/detect-http-start.c

/* Copyright (C) 2007-2017 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 Victor Julien <victor@inliniac.net>
 *
 * Implements http_start
 */

#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 "detect-http-header-common.h"

#include "flow.h"
#include "flow-var.h"
#include "flow-util.h"

#include "util-debug.h"
#include "util-unittest.h"
#include "util-unittest-helper.h"
#include "util-spm.h"
#include "util-print.h"

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

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

#include "util-print.h"

#define KEYWORD_NAME "http_start"
#define KEYWORD_DOC "http-keywords#http-start"
#define BUFFER_NAME "http_start"
#define BUFFER_DESC "http start: request/response line + headers"
static int g_buffer_id = 0;
static int g_keyword_thread_id = 0;

#define BUFFER_TX_STEP      4
#define BUFFER_SIZE_STEP    2048
static HttpHeaderThreadDataConfig g_td_config = { BUFFER_TX_STEP, BUFFER_SIZE_STEP };

static uint8_t *GetBufferForTX(htp_tx_t *tx, uint64_t tx_id,
        DetectEngineCtx *de_ctx, DetectEngineThreadCtx *det_ctx,
        Flow *f, HtpState *htp_state, 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;
    }

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

    size_t line_size = bstr_len(line) + 2;
    if (line_size + buf->len > buf->size) {
        if (HttpHeaderExpandBuffer(hdr_td, buf, line_size) != 0) {
            return NULL;
        }
    }
    memcpy(buf->buffer + buf->len, bstr_ptr(line), bstr_size(line));
    buf->len += bstr_size(line);
    buf->buffer[buf->len++] = '\r';
    buf->buffer[buf->len++] = '\n';

    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 0
        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;
            }
        }
#endif
        size_t size = size1 + size2 + 4;
        if (i + 1 == no_of_headers)
            size += 2;
        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 (i + 1 == no_of_headers) {
            buf->buffer[buf->len++] = '\r';
            buf->buffer[buf->len++] = '\n';
        }
    }

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

/** \brief HTTP Start 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 PrefilterTxHttpRequestStart(DetectEngineThreadCtx *det_ctx,
        const void *pectx,
        Packet *p, Flow *f, void *txv,
        const uint64_t idx, const uint8_t flags)
{
    SCEnter();

    const MpmCtx *mpm_ctx = (MpmCtx *)pectx;
    htp_tx_t *tx = (htp_tx_t *)txv;

    HtpState *htp_state = f->alstate;
    uint32_t buffer_len = 0;
    const uint8_t *buffer = GetBufferForTX(tx, idx,
            NULL, det_ctx, f, htp_state,
            flags, &buffer_len);

    if (buffer_len >= mpm_ctx->minlen) {
        (void)mpm_table[mpm_ctx->mpm_type].Search(mpm_ctx,
                &det_ctx->mtcu, &det_ctx->pmq, buffer, buffer_len);
    }
}

static int PrefilterTxHttpRequestStartRegister(SigGroupHead *sgh, MpmCtx *mpm_ctx)
{
    SCEnter();

    int r = PrefilterAppendTxEngine(sgh, PrefilterTxHttpRequestStart,
        ALPROTO_HTTP, HTP_REQUEST_HEADERS,
        mpm_ctx, NULL, KEYWORD_NAME " (request)");
    return r;
}

/** \brief HTTP Start 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 PrefilterTxHttpResponseStart(DetectEngineThreadCtx *det_ctx,
        const void *pectx,
        Packet *p, Flow *f, void *txv,
        const uint64_t idx, const uint8_t flags)
{
    SCEnter();

    const MpmCtx *mpm_ctx = (MpmCtx *)pectx;
    htp_tx_t *tx = (htp_tx_t *)txv;

    HtpState *htp_state = f->alstate;
    uint32_t buffer_len = 0;
    const uint8_t *buffer = GetBufferForTX(tx, idx, NULL, det_ctx,
            f, htp_state, flags, &buffer_len);

    if (buffer_len >= mpm_ctx->minlen) {
        (void)mpm_table[mpm_ctx->mpm_type].Search(mpm_ctx,
                &det_ctx->mtcu, &det_ctx->pmq, buffer, buffer_len);
    }
}

static int PrefilterTxHttpResponseStartRegister(SigGroupHead *sgh, MpmCtx *mpm_ctx)
{
    SCEnter();

    int r = PrefilterAppendTxEngine(sgh, PrefilterTxHttpResponseStart,
        ALPROTO_HTTP, HTP_RESPONSE_HEADERS,
        mpm_ctx, NULL, KEYWORD_NAME " (response)");
    return r;
}

static int InspectEngineHttpStart(ThreadVars *tv,
        DetectEngineCtx *de_ctx, DetectEngineThreadCtx *det_ctx,
        const Signature *s, const SigMatchData *smd,
        Flow *f, uint8_t flags, void *alstate, void *tx, uint64_t tx_id)
{
    HtpState *htp_state = (HtpState *)alstate;
    uint32_t buffer_len = 0;
    uint8_t *buffer = GetBufferForTX(tx, tx_id,
            de_ctx, det_ctx, f, htp_state,
            flags, &buffer_len);
    if (buffer_len == 0)
        goto end;

    det_ctx->buffer_offset = 0;
    det_ctx->discontinue_matching = 0;
    det_ctx->inspection_recursion_counter = 0;
    int r = DetectEngineContentInspection(de_ctx, det_ctx, s, smd,
                                          f,
                                          buffer, buffer_len,
                                          0,
                                          DETECT_ENGINE_CONTENT_INSPECTION_MODE_STATE, NULL);
    if (r == 1)
        return DETECT_ENGINE_INSPECT_SIG_MATCH;

 end:
    if (flags & STREAM_TOSERVER) {
        if (AppLayerParserGetStateProgress(IPPROTO_TCP, ALPROTO_HTTP, tx, flags) > HTP_REQUEST_HEADERS)
            return DETECT_ENGINE_INSPECT_SIG_CANT_MATCH;
    } else {
        if (AppLayerParserGetStateProgress(IPPROTO_TCP, ALPROTO_HTTP, tx, flags) > HTP_RESPONSE_HEADERS)
            return DETECT_ENGINE_INSPECT_SIG_CANT_MATCH;
    }
    return DETECT_ENGINE_INSPECT_SIG_NO_MATCH;
}

static int DetectHttpStartSetup(DetectEngineCtx *de_ctx, Signature *s, char *arg)
{
    s->init_data->list = g_buffer_id;
    return 0;
}

static void DetectHttpStartSetupCallback(Signature *s)
{
    SCLogDebug("callback invoked by %u", s->id);
    s->mask |= SIG_MASK_REQUIRE_HTTP_STATE;
}

/**
 * \brief Registers the keyword handlers for the "http_header" keyword.
 */
void DetectHttpStartRegister(void)
{
    sigmatch_table[DETECT_AL_HTTP_START].name = KEYWORD_NAME;
    sigmatch_table[DETECT_AL_HTTP_START].desc = BUFFER_NAME " sticky buffer";
    sigmatch_table[DETECT_AL_HTTP_START].url = DOC_URL DOC_VERSION "/rules/" KEYWORD_DOC;
    sigmatch_table[DETECT_AL_HTTP_START].Setup = DetectHttpStartSetup;

    sigmatch_table[DETECT_AL_HTTP_START].flags |= SIGMATCH_NOOPT ;

    DetectAppLayerMpmRegister(BUFFER_NAME, SIG_FLAG_TOSERVER, 2,
            PrefilterTxHttpRequestStartRegister);
    DetectAppLayerMpmRegister(BUFFER_NAME, SIG_FLAG_TOCLIENT, 2,
            PrefilterTxHttpResponseStartRegister);

    DetectAppLayerInspectEngineRegister(BUFFER_NAME,
            ALPROTO_HTTP, SIG_FLAG_TOSERVER,
            InspectEngineHttpStart);
    DetectAppLayerInspectEngineRegister(BUFFER_NAME,
            ALPROTO_HTTP, SIG_FLAG_TOCLIENT,
            InspectEngineHttpStart);

    DetectBufferTypeSetDescriptionByName(BUFFER_NAME,
            BUFFER_DESC);

    DetectBufferTypeRegisterSetupCallback(BUFFER_NAME,
            DetectHttpStartSetupCallback);

    g_buffer_id = DetectBufferTypeGetByName(BUFFER_NAME);

    g_keyword_thread_id = DetectRegisterThreadCtxGlobalFuncs(KEYWORD_NAME,
            HttpHeaderThreadDataInit, &g_td_config, HttpHeaderThreadDataFree);

    SCLogDebug("keyword %s registered. Thread id %d. "
            "Buffer %s registered. Buffer id %d",
            KEYWORD_NAME, g_keyword_thread_id,
            BUFFER_NAME, g_buffer_id);
}