detect-dns-name.c

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/* Copyright (C) 2025 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 rrnames:
 * - dns.queries.rrname
 * - dns.answers.rrname
 * - dns.authorities.name
 * - dns.additionals.name
 */
 
#include "detect.h"
#include "detect-parse.h"
#include "detect-engine.h"
#include "detect-engine-content-inspection.h"
#include "detect-engine-helper.h"
#include "detect-dns-name.h"
#include "rust.h"
 
enum DnsSection {
    DNS_QUERY = 0,
    DNS_ANSWER,
    DNS_AUTHORITY,
    DNS_ADDITIONAL,
};
 
static int query_buffer_id = 0;
static int answer_buffer_id = 0;
static int authority_buffer_id = 0;
static int additional_buffer_id = 0;
 
static int DetectSetup(DetectEngineCtx *de_ctx, Signature *s, const char *str, int id)
{
    if (DetectBufferSetActiveList(de_ctx, s, id) < 0) {
        return -1;
    }
    if (DetectSignatureSetAppProto(s, ALPROTO_DNS) < 0) {
        return -1;
    }
 
    return 0;
}
 
static int SetupQueryBuffer(DetectEngineCtx *de_ctx, Signature *s, const char *str)
{
    return DetectSetup(de_ctx, s, str, query_buffer_id);
}
 
static int SetupAnswerBuffer(DetectEngineCtx *de_ctx, Signature *s, const char *str)
{
    return DetectSetup(de_ctx, s, str, answer_buffer_id);
}
 
static int SetupAdditionalsBuffer(DetectEngineCtx *de_ctx, Signature *s, const char *str)
{
    return DetectSetup(de_ctx, s, str, additional_buffer_id);
}
 
static int SetupAuthoritiesBuffer(DetectEngineCtx *de_ctx, Signature *s, const char *str)
{
    return DetectSetup(de_ctx, s, str, authority_buffer_id);
}
 
static InspectionBuffer *GetBuffer(DetectEngineThreadCtx *det_ctx,
        const DetectEngineTransforms *transforms, Flow *f, uint8_t flags, void *txv, int list_id,
        uint32_t index, enum DnsSection what)
{
    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;
 
    bool ok = false;
    switch (what) {
        case DNS_QUERY:
            ok = SCDnsTxGetQueryName(txv, to_client, index, &data, &data_len);
            break;
        case DNS_ANSWER:
            ok = SCDnsTxGetAnswerName(txv, to_client, index, &data, &data_len);
            break;
        case DNS_AUTHORITY:
            ok = SCDnsTxGetAuthorityName(txv, index, &data, &data_len);
            break;
        case DNS_ADDITIONAL:
            ok = SCDnsTxGetAdditionalName(txv, index, &data, &data_len);
            break;
        default:
            DEBUG_VALIDATE_BUG_ON("unhandled dns rrname type");
            InspectionBufferSetupMultiEmpty(buffer);
            return NULL;
    }
 
    if (ok) {
        InspectionBufferSetupMulti(buffer, transforms, data, data_len);
        buffer->flags = DETECT_CI_FLAGS_SINGLE;
        return buffer;
    }
 
    InspectionBufferSetupMultiEmpty(buffer);
    return NULL;
}
 
static InspectionBuffer *GetQueryBuffer(DetectEngineThreadCtx *det_ctx,
        const DetectEngineTransforms *transforms, Flow *f, uint8_t flags, void *txv, int list_id,
        uint32_t index)
{
    return GetBuffer(det_ctx, transforms, f, flags, txv, list_id, index, DNS_QUERY);
}
 
static InspectionBuffer *GetAnswerBuffer(DetectEngineThreadCtx *det_ctx,
        const DetectEngineTransforms *transforms, Flow *f, uint8_t flags, void *txv, int list_id,
        uint32_t index)
{
    return GetBuffer(det_ctx, transforms, f, flags, txv, list_id, index, DNS_ANSWER);
}
 
static InspectionBuffer *GetAuthorityBuffer(DetectEngineThreadCtx *det_ctx,
        const DetectEngineTransforms *transforms, Flow *f, uint8_t flags, void *txv, int list_id,
        uint32_t index)
{
    return GetBuffer(det_ctx, transforms, f, flags, txv, list_id, index, DNS_AUTHORITY);
}
 
static InspectionBuffer *GetAdditionalBuffer(DetectEngineThreadCtx *det_ctx,
        const DetectEngineTransforms *transforms, Flow *f, uint8_t flags, void *txv, int list_id,
        uint32_t index)
{
    return GetBuffer(det_ctx, transforms, f, flags, txv, list_id, index, DNS_ADDITIONAL);
}
 
static int Register(const char *keyword, const char *desc, const char *doc,
        int (*Setup)(DetectEngineCtx *, Signature *, const char *),
        InspectionMultiBufferGetDataPtr GetBufferFn)
{
    int keyword_id = SCDetectHelperNewKeywordId();
    sigmatch_table[keyword_id].name = keyword;
    sigmatch_table[keyword_id].desc = desc;
    sigmatch_table[keyword_id].url = doc;
    sigmatch_table[keyword_id].Setup = Setup;
    sigmatch_table[keyword_id].flags |= SIGMATCH_NOOPT;
    sigmatch_table[keyword_id].flags |= SIGMATCH_INFO_STICKY_BUFFER;
 
    DetectAppLayerMultiRegister(keyword, ALPROTO_DNS, SIG_FLAG_TOSERVER, 0, GetBufferFn, 2, 1);
    DetectAppLayerMultiRegister(keyword, ALPROTO_DNS, SIG_FLAG_TOCLIENT, 0, GetBufferFn, 2, 1);
 
    DetectBufferTypeSetDescriptionByName(keyword, keyword);
    DetectBufferTypeSupportsMultiInstance(keyword);
 
    return DetectBufferTypeGetByName(keyword);
}
 
void DetectDnsNameRegister(void)
{
    query_buffer_id = Register("dns.queries.rrname", "DNS query rrname sticky buffer",
            "/rules/dns-keywords.html#dns.queries.rrname", SetupQueryBuffer, GetQueryBuffer);
    answer_buffer_id = Register("dns.answers.rrname", "DNS answer rrname sticky buffer",
            "/rules/dns-keywords.html#dns.answers.rrname", SetupAnswerBuffer, GetAnswerBuffer);
    additional_buffer_id =
            Register("dns.additionals.rrname", "DNS additionals rrname sticky buffer",
                    "/rules/dns-keywords.html#dns-additionals-rrname", SetupAdditionalsBuffer,
                    GetAdditionalBuffer);
    authority_buffer_id = Register("dns.authorities.rrname", "DNS authorities rrname sticky buffer",
            "/rules/dns-keywords.html#dns-authorities-rrname", SetupAuthoritiesBuffer,
            GetAuthorityBuffer);
}