detect-snmp-usm.c

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/* Copyright (C) 2022 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.
 */
 
#include "suricata-common.h"
#include "rust.h"
#include "detect-snmp-usm.h"
#include "detect-engine.h"
#include "detect-engine-mpm.h"
#include "detect-engine-prefilter.h"
#include "detect-parse.h"
 
static int g_buffer_id = 0;
 
static int DetectSNMPUsmSetup(DetectEngineCtx *de_ctx, Signature *s, const char *str)
{
    if (DetectBufferSetActiveList(de_ctx, s, g_buffer_id) < 0)
        return -1;
 
    if (DetectSignatureSetAppProto(s, ALPROTO_SNMP) != 0)
        return -1;
 
    return 0;
}
 
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) {
        uint32_t data_len = 0;
        const uint8_t *data = NULL;
 
        rs_snmp_tx_get_usm(txv, &data, &data_len);
        if (data == NULL || data_len == 0) {
            return NULL;
        }
 
        InspectionBufferSetup(det_ctx, list_id, buffer, data, data_len);
        InspectionBufferApplyTransforms(buffer, transforms);
    }
 
    return buffer;
}
 
void DetectSNMPUsmRegister(void)
{
    sigmatch_table[DETECT_AL_SNMP_USM].name = "snmp.usm";
    sigmatch_table[DETECT_AL_SNMP_USM].desc = "SNMP content modifier to match on the SNMP usm";
    sigmatch_table[DETECT_AL_SNMP_USM].Setup = DetectSNMPUsmSetup;
 
    sigmatch_table[DETECT_AL_SNMP_USM].flags |= SIGMATCH_NOOPT | SIGMATCH_INFO_STICKY_BUFFER;
 
    /* register inspect engines */
    DetectAppLayerInspectEngineRegister("snmp.usm", ALPROTO_SNMP, SIG_FLAG_TOSERVER, 0,
            DetectEngineInspectBufferGeneric, GetData);
    DetectAppLayerMpmRegister("snmp.usm", SIG_FLAG_TOSERVER, 2, PrefilterGenericMpmRegister,
            GetData, ALPROTO_SNMP, 0);
    DetectAppLayerInspectEngineRegister("snmp.usm", ALPROTO_SNMP, SIG_FLAG_TOCLIENT, 0,
            DetectEngineInspectBufferGeneric, GetData);
    DetectAppLayerMpmRegister("snmp.usm", SIG_FLAG_TOCLIENT, 2, PrefilterGenericMpmRegister,
            GetData, ALPROTO_SNMP, 0);
 
    DetectBufferTypeSetDescriptionByName("snmp.usm", "SNMP USM");
 
    g_buffer_id = DetectBufferTypeGetByName("snmp.usm");
}