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/*
* snmp.c
*
* Copyright (C) 2011-22 - ntop.org
*
* nDPI is free software: you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* nDPI 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 Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with nDPI. If not, see <http://www.gnu.org/licenses/>.
*
*/
#include "ndpi_protocol_ids.h"
#define NDPI_CURRENT_PROTO NDPI_PROTOCOL_SNMP
#include "ndpi_api.h"
static void ndpi_search_snmp(struct ndpi_detection_module_struct *ndpi_struct,
struct ndpi_flow_struct *flow);
/* *************************************************************** */
static void ndpi_int_snmp_add_connection(struct ndpi_detection_module_struct
*ndpi_struct, struct ndpi_flow_struct *flow) {
ndpi_set_detected_protocol(ndpi_struct, flow, NDPI_PROTOCOL_SNMP,
NDPI_PROTOCOL_UNKNOWN, NDPI_CONFIDENCE_DPI);
}
/* *************************************************************** */
static int ndpi_search_snmp_again(struct ndpi_detection_module_struct *ndpi_struct,
struct ndpi_flow_struct *flow) {
ndpi_search_snmp(ndpi_struct, flow);
#ifdef SNMP_DEBUG
printf("=> %s()\n", __FUNCTION__);
#endif
return((flow->extra_packets_func == NULL) /* We're good now */ ? 0 : 1);
}
/* *************************************************************** */
void ndpi_search_snmp(struct ndpi_detection_module_struct *ndpi_struct,
struct ndpi_flow_struct *flow) {
struct ndpi_packet_struct *packet = &ndpi_struct->packet;
u_int16_t snmp_port = htons(161), trap_port = htons(162);
u_int8_t version;
if((packet->payload_packet_len <= 32)
||(packet->payload[0] != 0x30)
|| (((version = packet->payload[4]) != 0 /* SNMPv1 */)
&& ((version = packet->payload[4]) != 1 /* SNMPv2c */)
&& ((version = packet->payload[4]) != 3 /* SNMPv3 */))
|| ((packet->udp->source != snmp_port)
&& (packet->udp->dest != snmp_port)
&& (packet->udp->dest != trap_port))
/* version */
|| ((packet->payload[1] + 2) != packet->payload_packet_len)) {
NDPI_EXCLUDE_PROTO(ndpi_struct, flow);
} else {
if((version == 0) || (version == 1)) {
u_int8_t community_len = packet->payload[6];
u_int8_t snmp_primitive_offset = 7 + community_len;
if(snmp_primitive_offset < packet->payload_packet_len) {
u_int8_t snmp_primitive = packet->payload[snmp_primitive_offset] & 0xF;
if(snmp_primitive == 2 /* Get Response */) {
u_int8_t error_status_offset = 17 + community_len;
if(error_status_offset < packet->payload_packet_len) {
u_int8_t error_status = packet->payload[error_status_offset];
#ifdef SNMP_DEBUG
printf("-> %u [offset: %u][primitive: %u]\n",
error_status, error_status_offset, snmp_primitive);
#endif
flow->extra_packets_func = NULL; /* We're good now */
if(error_status != 0)
ndpi_set_risk(ndpi_struct, flow, NDPI_ERROR_CODE_DETECTED);
}
}
}
}
ndpi_int_snmp_add_connection(ndpi_struct, flow);
if(flow->extra_packets_func == NULL) {
/* This is necessary to inform the core to call this dissector again */
flow->check_extra_packets = 1;
flow->max_extra_packets_to_check = 8;
flow->extra_packets_func = ndpi_search_snmp_again;
}
return;
}
}
/* *************************************************************** */
void init_snmp_dissector(struct ndpi_detection_module_struct *ndpi_struct,
u_int32_t *id, NDPI_PROTOCOL_BITMASK *detection_bitmask) {
ndpi_set_bitmask_protocol_detection("SNMP", ndpi_struct, detection_bitmask, *id,
NDPI_PROTOCOL_SNMP,
ndpi_search_snmp,
NDPI_SELECTION_BITMASK_PROTOCOL_V4_V6_UDP_WITH_PAYLOAD,
SAVE_DETECTION_BITMASK_AS_UNKNOWN,
ADD_TO_DETECTION_BITMASK);
*id += 1;
}
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