detect-dns-answer-name.c

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/* Copyright (C) 2023 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
 *
 * Detect keyword for DNS answer name: dns.answer.name
 */
 
#include "detect.h"
#include "detect-parse.h"
#include "detect-engine.h"
#include "detect-engine-prefilter.h"
#include "detect-engine-content-inspection.h"
#include "detect-dns-answer-name.h"
#include "util-profiling.h"
#include "rust.h"
 
static int detect_buffer_id = 0;
 
static int DetectSetup(DetectEngineCtx *de_ctx, Signature *s, const char *str)
{
    if (DetectBufferSetActiveList(de_ctx, s, detect_buffer_id) < 0) {
        return -1;
    }
    if (DetectSignatureSetAppProto(s, ALPROTO_DNS) < 0) {
        return -1;
    }
 
    return 0;
}
 
static InspectionBuffer *GetBuffer(DetectEngineThreadCtx *det_ctx,
        const DetectEngineTransforms *transforms, Flow *f, uint8_t flags, void *txv, int list_id,
        uint32_t index)
{
    InspectionBuffer *buffer = InspectionBufferMultipleForListGet(det_ctx, list_id, index);
    if (buffer == NULL) {
        return NULL;
    }
    if (buffer->initialized) {
        return buffer;
    }
 
    bool to_client = (flags & STREAM_TOSERVER) == 0;
    const uint8_t *data = NULL;
    uint32_t data_len = 0;
 
    if (!SCDnsTxGetAnswerName(txv, to_client, index, &data, &data_len)) {
        InspectionBufferSetupMultiEmpty(buffer);
        return NULL;
    }
    InspectionBufferSetupMulti(buffer, transforms, data, data_len);
    buffer->flags = DETECT_CI_FLAGS_SINGLE;
    return buffer;
}
 
void DetectDnsAnswerNameRegister(void)
{
    static const char *keyword = "dns.answer.name";
    sigmatch_table[DETECT_AL_DNS_ANSWER_NAME].name = keyword;
    sigmatch_table[DETECT_AL_DNS_ANSWER_NAME].desc = "DNS answer name sticky buffer";
    sigmatch_table[DETECT_AL_DNS_ANSWER_NAME].url = "/rules/dns-keywords.html#dns-answer-name";
    sigmatch_table[DETECT_AL_DNS_ANSWER_NAME].Setup = DetectSetup;
    sigmatch_table[DETECT_AL_DNS_ANSWER_NAME].flags |= SIGMATCH_NOOPT;
    sigmatch_table[DETECT_AL_DNS_ANSWER_NAME].flags |= SIGMATCH_INFO_STICKY_BUFFER;
 
    /* Register in the TO_SERVER direction, even though this is not
       normal, it could be provided as part of a request. */
    DetectAppLayerMultiRegister(keyword, ALPROTO_DNS, SIG_FLAG_TOSERVER, 0, GetBuffer, 2, 1);
    /* Register in the TO_CLIENT direction. */
    DetectAppLayerMultiRegister(keyword, ALPROTO_DNS, SIG_FLAG_TOCLIENT, 0, GetBuffer, 2, 1);
 
    DetectBufferTypeSetDescriptionByName(keyword, "dns answer name");
    DetectBufferTypeSupportsMultiInstance(keyword);
 
    detect_buffer_id = DetectBufferTypeGetByName(keyword);
}