detect-http-method.c

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/* Copyright (C) 2007-2019 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 Brian Rectanus <brectanu@gmail.com>
 *
 * Implements the http_method 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-prefilter.h"
#include "detect-content.h"
#include "detect-pcre.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 "app-layer.h"
#include "app-layer-parser.h"
 
#include "app-layer-htp.h"
#include "detect-http-method.h"
#include "stream-tcp.h"
 
static int g_http_method_buffer_id = 0;
static int DetectHttpMethodSetup(DetectEngineCtx *, Signature *, const char *);
static int DetectHttpMethodSetupSticky(DetectEngineCtx *de_ctx, Signature *s, const char *str);
#ifdef UNITTESTS
void DetectHttpMethodRegisterTests(void);
#endif
void DetectHttpMethodFree(void *);
static bool DetectHttpMethodValidateCallback(const Signature *s, const char **sigerror);
static InspectionBuffer *GetData(DetectEngineThreadCtx *det_ctx,
        const DetectEngineTransforms *transforms, Flow *_f,
        const uint8_t _flow_flags, void *txv, const int list_id);
static InspectionBuffer *GetData2(DetectEngineThreadCtx *det_ctx,
        const DetectEngineTransforms *transforms, Flow *_f, const uint8_t _flow_flags, void *txv,
        const int list_id);
 
/**
 * \brief Registration function for keyword: http_method
 */
void DetectHttpMethodRegister(void)
{
    /* http_method content modifier */
    sigmatch_table[DETECT_AL_HTTP_METHOD].name = "http_method";
    sigmatch_table[DETECT_AL_HTTP_METHOD].desc = "content modifier to match only on the HTTP method-buffer";
    sigmatch_table[DETECT_AL_HTTP_METHOD].url = "/rules/http-keywords.html#http-method";
    sigmatch_table[DETECT_AL_HTTP_METHOD].Match = NULL;
    sigmatch_table[DETECT_AL_HTTP_METHOD].Setup = DetectHttpMethodSetup;
#ifdef UNITTESTS
    sigmatch_table[DETECT_AL_HTTP_METHOD].RegisterTests = DetectHttpMethodRegisterTests;
#endif
    sigmatch_table[DETECT_AL_HTTP_METHOD].flags |= SIGMATCH_NOOPT|SIGMATCH_INFO_CONTENT_MODIFIER;
    sigmatch_table[DETECT_AL_HTTP_METHOD].alternative = DETECT_HTTP_METHOD;
 
    /* http.method sticky buffer */
    sigmatch_table[DETECT_HTTP_METHOD].name = "http.method";
    sigmatch_table[DETECT_HTTP_METHOD].desc = "sticky buffer to match specifically and only on the HTTP method buffer";
    sigmatch_table[DETECT_HTTP_METHOD].url = "/rules/http-keywords.html#http-method";
    sigmatch_table[DETECT_HTTP_METHOD].Setup = DetectHttpMethodSetupSticky;
    sigmatch_table[DETECT_HTTP_METHOD].flags |= SIGMATCH_NOOPT|SIGMATCH_INFO_STICKY_BUFFER;
 
    DetectAppLayerInspectEngineRegister("http_method", ALPROTO_HTTP1, SIG_FLAG_TOSERVER,
            HTP_REQUEST_LINE, DetectEngineInspectBufferGeneric, GetData);
 
    DetectAppLayerMpmRegister("http_method", SIG_FLAG_TOSERVER, 4, PrefilterGenericMpmRegister,
            GetData, ALPROTO_HTTP1, HTP_REQUEST_LINE);
 
    DetectAppLayerInspectEngineRegister("http_method", ALPROTO_HTTP2, SIG_FLAG_TOSERVER,
            HTTP2StateDataClient, DetectEngineInspectBufferGeneric, GetData2);
 
    DetectAppLayerMpmRegister("http_method", SIG_FLAG_TOSERVER, 4, PrefilterGenericMpmRegister,
            GetData2, ALPROTO_HTTP2, HTTP2StateDataClient);
 
    DetectBufferTypeSetDescriptionByName("http_method",
            "http request method");
 
    DetectBufferTypeRegisterValidateCallback("http_method",
            DetectHttpMethodValidateCallback);
 
    g_http_method_buffer_id = DetectBufferTypeGetByName("http_method");
 
    SCLogDebug("registering http_method rule option");
}
 
/**
 * \brief This function is used to add the parsed "http_method" option
 *        into the current signature.
 *
 * \param de_ctx Pointer to the Detection Engine Context.
 * \param s      Pointer to the Current Signature.
 * \param str    Pointer to the user provided option string.
 *
 * \retval  0 on Success.
 * \retval -1 on Failure.
 */
static int DetectHttpMethodSetup(DetectEngineCtx *de_ctx, Signature *s, const char *str)
{
    return DetectEngineContentModifierBufferSetup(
            de_ctx, s, str, DETECT_AL_HTTP_METHOD, g_http_method_buffer_id, ALPROTO_HTTP1);
}
 
/**
 * \brief this function setup the http.method 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 DetectHttpMethodSetupSticky(DetectEngineCtx *de_ctx, Signature *s, const char *str)
{
    if (DetectBufferSetActiveList(de_ctx, s, g_http_method_buffer_id) < 0)
        return -1;
 
    if (DetectSignatureSetAppProto(s, ALPROTO_HTTP) < 0)
        return -1;
 
    return 0;
}
 
/**
 *  \retval 1 valid
 *  \retval 0 invalid
 */
static bool DetectHttpMethodValidateCallback(const Signature *s, const char **sigerror)
{
    for (uint32_t x = 0; x < s->init_data->buffer_index; x++) {
        if (s->init_data->buffers[x].id != (uint32_t)g_http_method_buffer_id)
            continue;
        const SigMatch *sm = s->init_data->buffers[x].head;
        for (; sm != NULL; sm = sm->next) {
            if (sm->type != DETECT_CONTENT)
                continue;
            const DetectContentData *cd = (const DetectContentData *)sm->ctx;
            if (cd->content && cd->content_len) {
                if (cd->content[cd->content_len - 1] == 0x20) {
                    *sigerror = "http_method pattern with trailing space";
                    SCLogError("%s", *sigerror);
                    return false;
                } else if (cd->content[0] == 0x20) {
                    *sigerror = "http_method pattern with leading space";
                    SCLogError("%s", *sigerror);
                    return false;
                } else if (cd->content[cd->content_len - 1] == 0x09) {
                    *sigerror = "http_method pattern with trailing tab";
                    SCLogError("%s", *sigerror);
                    return false;
                } else if (cd->content[0] == 0x09) {
                    *sigerror = "http_method pattern with leading tab";
                    SCLogError("%s", *sigerror);
                    return false;
                }
            }
        }
    }
    return true;
}
 
static InspectionBuffer *GetData(DetectEngineThreadCtx *det_ctx,
        const DetectEngineTransforms *transforms, Flow *_f,
        const uint8_t _flow_flags, void *txv, const int list_id)
{
    InspectionBuffer *buffer = InspectionBufferGet(det_ctx, list_id);
    if (buffer->inspect == NULL) {
        htp_tx_t *tx = (htp_tx_t *)txv;
 
        if (tx->request_method == NULL)
            return NULL;
 
        const uint32_t data_len = bstr_len(tx->request_method);
        const uint8_t *data = bstr_ptr(tx->request_method);
 
        InspectionBufferSetup(det_ctx, list_id, buffer, data, data_len);
        InspectionBufferApplyTransforms(buffer, transforms);
    }
 
    return buffer;
}
 
static InspectionBuffer *GetData2(DetectEngineThreadCtx *det_ctx,
        const DetectEngineTransforms *transforms, Flow *_f, const uint8_t _flow_flags, void *txv,
        const int list_id)
{
    InspectionBuffer *buffer = InspectionBufferGet(det_ctx, list_id);
    if (buffer->inspect == NULL) {
        uint32_t b_len = 0;
        const uint8_t *b = NULL;
 
        if (rs_http2_tx_get_method(txv, &b, &b_len) != 1)
            return NULL;
        if (b == NULL || b_len == 0)
            return NULL;
 
        InspectionBufferSetup(det_ctx, list_id, buffer, b, b_len);
        InspectionBufferApplyTransforms(buffer, transforms);
    }
 
    return buffer;
}
 
#ifdef UNITTESTS
#include "tests/detect-http-method.c"
#endif
 
/**
 * @}
 */