/*
 * syslog.c
 *
 * Copyright (C) 2009-2011 by ipoque GmbH
 * Copyright (C) 2011-18 - ntop.org
 *
 * This file is part of nDPI, an open source deep packet inspection
 * library based on the OpenDPI and PACE technology by ipoque GmbH
 *
 * 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_SYSLOG

#include "ndpi_api.h"

static void ndpi_int_syslog_add_connection(struct ndpi_detection_module_struct
        *ndpi_struct, struct ndpi_flow_struct *flow)
{
    ndpi_set_detected_protocol(ndpi_struct, flow, NDPI_PROTOCOL_SYSLOG);
}

void ndpi_search_syslog(struct ndpi_detection_module_struct
        *ndpi_struct, struct ndpi_flow_struct *flow)
{
    struct ndpi_packet_struct *packet = &flow->packet;
    u_int8_t i;

    NDPI_LOG_DBG(ndpi_struct, "search syslog\n");

    if (packet->payload_packet_len > 20 && packet->payload_packet_len <= 1024 && packet->payload[0] == '<') {
        NDPI_LOG_DBG2(ndpi_struct, "checked len>20 and <1024 and first symbol=<\n");

        for (i = 1; i <= 3; i++) {
            if (packet->payload[i] < '0' || packet->payload[i] > '9') {
                break;
            }
        }
        NDPI_LOG_DBG2(ndpi_struct,
                "read symbols while the symbol is a number.\n");

        if (packet->payload[i++] != '>') {
            NDPI_LOG_DBG(ndpi_struct, "excluded, there is no > following the number\n");
            NDPI_ADD_PROTOCOL_TO_BITMASK(flow->excluded_protocol_bitmask, NDPI_PROTOCOL_SYSLOG);
            return;
        } else {
            NDPI_LOG_DBG2(ndpi_struct, "a > following the number\n");
        }

        if (packet->payload[i] == 0x20) {
            NDPI_LOG_DBG2(ndpi_struct, "a blank following the >: increment i\n");
            i++;
        } else {
            NDPI_LOG_DBG2(ndpi_struct, "no blank following the >: do nothing\n");
        }

        /* check for "last message repeated" */
        if (i + sizeof("last message") - 1 <= packet->payload_packet_len &&
                memcmp(packet->payload + i, "last message", sizeof("last message") - 1) == 0) {

            NDPI_LOG_INFO(ndpi_struct, "found syslog by 'last message' string\n");

            ndpi_int_syslog_add_connection(ndpi_struct, flow);

            return;
        } else if (i + sizeof("snort: ") - 1 <= packet->payload_packet_len &&
                memcmp(packet->payload + i, "snort: ", sizeof("snort: ") - 1) == 0) {

            /* snort events */

            NDPI_LOG_INFO(ndpi_struct, "found syslog by 'snort: ' string\n");

            ndpi_int_syslog_add_connection(ndpi_struct, flow);

            return;
        }

        if (memcmp(&packet->payload[i], "Jan", 3) != 0
                && memcmp(&packet->payload[i], "Feb", 3) != 0
                && memcmp(&packet->payload[i], "Mar", 3) != 0
                && memcmp(&packet->payload[i], "Apr", 3) != 0
                && memcmp(&packet->payload[i], "May", 3) != 0
                && memcmp(&packet->payload[i], "Jun", 3) != 0
                && memcmp(&packet->payload[i], "Jul", 3) != 0
                && memcmp(&packet->payload[i], "Aug", 3) != 0
                && memcmp(&packet->payload[i], "Sep", 3) != 0
                && memcmp(&packet->payload[i], "Oct", 3) != 0
                && memcmp(&packet->payload[i], "Nov", 3) != 0 && memcmp(&packet->payload[i], "Dec", 3) != 0) {

            NDPI_EXCLUDE_PROTO(ndpi_struct, flow);

            return;

        } else {

            NDPI_LOG_INFO(ndpi_struct, "found syslog\n");

            ndpi_int_syslog_add_connection(ndpi_struct, flow);

            return;
        }
    }
    NDPI_EXCLUDE_PROTO(ndpi_struct, flow);
}


void init_syslog_dissector(struct ndpi_detection_module_struct *ndpi_struct, u_int32_t *id, NDPI_PROTOCOL_BITMASK *detection_bitmask)
{
    ndpi_set_bitmask_protocol_detection("Syslog", ndpi_struct, detection_bitmask, *id,
            NDPI_PROTOCOL_SYSLOG,
            ndpi_search_syslog,
            NDPI_SELECTION_BITMASK_PROTOCOL_V4_V6_TCP_OR_UDP_WITH_PAYLOAD_WITHOUT_RETRANSMISSION,
            SAVE_DETECTION_BITMASK_AS_UNKNOWN,
            ADD_TO_DETECTION_BITMASK);

    *id += 1;
}
