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/*
* dnscrypt.c
*
* Copyright (C) 2020 - 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_DNSCRYPT
#include "ndpi_api.h"
#include "ndpi_private.h"
static void ndpi_int_dnscrypt_add_connection(struct ndpi_detection_module_struct *ndpi_struct,
struct ndpi_flow_struct *flow)
{
ndpi_set_detected_protocol(ndpi_struct, flow, NDPI_PROTOCOL_DNSCRYPT, NDPI_PROTOCOL_UNKNOWN, NDPI_CONFIDENCE_DPI);
}
static void ndpi_search_dnscrypt(struct ndpi_detection_module_struct *ndpi_struct,
struct ndpi_flow_struct *flow)
{
struct ndpi_packet_struct *packet = &ndpi_struct->packet;
static char const * const dnscrypt_initial = "2\rdnscrypt";
NDPI_LOG_DBG(ndpi_struct, "search dnscrypt\n");
/* dnscrypt protocol version 1: check magic */
if (packet->payload_packet_len >= 64 &&
strncmp((char*)packet->payload, "r6fnvWj8", strlen("r6fnvWj8")) == 0)
{
ndpi_int_dnscrypt_add_connection(ndpi_struct, flow);
return;
}
/* dnscrypt protocol version 1 and 2: resolver ping */
if (packet->payload_packet_len > 13 + strlen(dnscrypt_initial) &&
strncasecmp((char*)packet->payload + 13, dnscrypt_initial, strlen(dnscrypt_initial)) == 0)
{
ndpi_int_dnscrypt_add_connection(ndpi_struct, flow);
return;
}
if ((flow->packet_direction_counter[packet->packet_direction] >= 1 &&
flow->packet_direction_counter[1 - packet->packet_direction] >= 1) ||
flow->packet_counter >= 8) {
/*
* Wait for at least one packet per direction, up to a max
* Required as we need to wait for the server response which contains the ASCII pattern below.
*/
NDPI_EXCLUDE_PROTO(ndpi_struct, flow);
return;
}
}
void init_dnscrypt_dissector(struct ndpi_detection_module_struct *ndpi_struct, u_int32_t *id)
{
ndpi_set_bitmask_protocol_detection(
"DNScrypt", ndpi_struct, *id,
NDPI_PROTOCOL_DNSCRYPT, ndpi_search_dnscrypt, NDPI_SELECTION_BITMASK_PROTOCOL_V4_V6_TCP_OR_UDP_WITH_PAYLOAD_WITHOUT_RETRANSMISSION,
SAVE_DETECTION_BITMASK_AS_UNKNOWN, ADD_TO_DETECTION_BITMASK);
*id += 1;
}
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