/*
 * mail_pop.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_MAIL_POP

#include "ndpi_api.h"

#define POP_BIT_AUTH		0x0001
#define POP_BIT_APOP		0x0002
#define POP_BIT_USER		0x0004
#define POP_BIT_PASS		0x0008
#define POP_BIT_CAPA		0x0010
#define POP_BIT_LIST		0x0020
#define POP_BIT_STAT		0x0040
#define POP_BIT_UIDL		0x0080
#define POP_BIT_RETR		0x0100
#define POP_BIT_DELE		0x0200
#define POP_BIT_STLS		0x0400

static void ndpi_int_mail_pop_add_connection(struct ndpi_detection_module_struct
        *ndpi_struct, struct ndpi_flow_struct *flow)
{
    ndpi_set_detected_protocol(ndpi_struct, flow, NDPI_PROTOCOL_MAIL_POP);
}


static int ndpi_int_mail_pop_check_for_client_commands(struct ndpi_detection_module_struct
        *ndpi_struct, struct ndpi_flow_struct *flow)
{
    struct ndpi_packet_struct *packet = &flow->packet;

    if (packet->payload_packet_len > 4) {
        if ((packet->payload[0] == 'A' || packet->payload[0] == 'a')
                && (packet->payload[1] == 'U' || packet->payload[1] == 'u')
                && (packet->payload[2] == 'T' || packet->payload[2] == 't')
                && (packet->payload[3] == 'H' || packet->payload[3] == 'h')) {
            flow->l4.tcp.pop_command_bitmask |= POP_BIT_AUTH;
            return 1;
        } else if ((packet->payload[0] == 'A' || packet->payload[0] == 'a')
                && (packet->payload[1] == 'P' || packet->payload[1] == 'p')
                && (packet->payload[2] == 'O' || packet->payload[2] == 'o')
                && (packet->payload[3] == 'P' || packet->payload[3] == 'p')) {
            flow->l4.tcp.pop_command_bitmask |= POP_BIT_APOP;
            return 1;
        } else if ((packet->payload[0] == 'U' || packet->payload[0] == 'u')
                && (packet->payload[1] == 'S' || packet->payload[1] == 's')
                && (packet->payload[2] == 'E' || packet->payload[2] == 'e')
                && (packet->payload[3] == 'R' || packet->payload[3] == 'r')) {
            flow->l4.tcp.pop_command_bitmask |= POP_BIT_USER;
            return 1;
        } else if ((packet->payload[0] == 'P' || packet->payload[0] == 'p')
                && (packet->payload[1] == 'A' || packet->payload[1] == 'a')
                && (packet->payload[2] == 'S' || packet->payload[2] == 's')
                && (packet->payload[3] == 'S' || packet->payload[3] == 's')) {
            flow->l4.tcp.pop_command_bitmask |= POP_BIT_PASS;
            return 1;
        } else if ((packet->payload[0] == 'C' || packet->payload[0] == 'c')
                && (packet->payload[1] == 'A' || packet->payload[1] == 'a')
                && (packet->payload[2] == 'P' || packet->payload[2] == 'p')
                && (packet->payload[3] == 'A' || packet->payload[3] == 'a')) {
            flow->l4.tcp.pop_command_bitmask |= POP_BIT_CAPA;
            return 1;
        } else if ((packet->payload[0] == 'L' || packet->payload[0] == 'l')
                && (packet->payload[1] == 'I' || packet->payload[1] == 'i')
                && (packet->payload[2] == 'S' || packet->payload[2] == 's')
                && (packet->payload[3] == 'T' || packet->payload[3] == 't')) {
            flow->l4.tcp.pop_command_bitmask |= POP_BIT_LIST;
            return 1;
        } else if ((packet->payload[0] == 'S' || packet->payload[0] == 's')
                && (packet->payload[1] == 'T' || packet->payload[1] == 't')
                && (packet->payload[2] == 'A' || packet->payload[2] == 'a')
                && (packet->payload[3] == 'T' || packet->payload[3] == 't')) {
            flow->l4.tcp.pop_command_bitmask |= POP_BIT_STAT;
            return 1;
        } else if ((packet->payload[0] == 'U' || packet->payload[0] == 'u')
                && (packet->payload[1] == 'I' || packet->payload[1] == 'i')
                && (packet->payload[2] == 'D' || packet->payload[2] == 'd')
                && (packet->payload[3] == 'L' || packet->payload[3] == 'l')) {
            flow->l4.tcp.pop_command_bitmask |= POP_BIT_UIDL;
            return 1;
        } else if ((packet->payload[0] == 'R' || packet->payload[0] == 'r')
                && (packet->payload[1] == 'E' || packet->payload[1] == 'e')
                && (packet->payload[2] == 'T' || packet->payload[2] == 't')
                && (packet->payload[3] == 'R' || packet->payload[3] == 'r')) {
            flow->l4.tcp.pop_command_bitmask |= POP_BIT_RETR;
            return 1;
        } else if ((packet->payload[0] == 'D' || packet->payload[0] == 'd')
                && (packet->payload[1] == 'E' || packet->payload[1] == 'e')
                && (packet->payload[2] == 'L' || packet->payload[2] == 'l')
                && (packet->payload[3] == 'E' || packet->payload[3] == 'e')) {
            flow->l4.tcp.pop_command_bitmask |= POP_BIT_DELE;
            return 1;
        } else if ((packet->payload[0] == 'S' || packet->payload[0] == 's')
                && (packet->payload[1] == 'T' || packet->payload[1] == 't')
                && (packet->payload[2] == 'L' || packet->payload[2] == 'l')
                && (packet->payload[3] == 'S' || packet->payload[3] == 's')) {
            flow->l4.tcp.pop_command_bitmask |= POP_BIT_STLS;
            return 1;
        }
    }
    return 0;
}



void ndpi_search_mail_pop_tcp(struct ndpi_detection_module_struct
        *ndpi_struct, struct ndpi_flow_struct *flow)
{
    struct ndpi_packet_struct *packet = &flow->packet;
    u_int8_t a = 0;
    u_int8_t bit_count = 0;

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



    if ((packet->payload_packet_len > 3
                && (packet->payload[0] == '+' && (packet->payload[1] == 'O' || packet->payload[1] == 'o')
                    && (packet->payload[2] == 'K' || packet->payload[2] == 'k')))
            || (packet->payload_packet_len > 4
                && (packet->payload[0] == '-' && (packet->payload[1] == 'E' || packet->payload[1] == 'e')
                    && (packet->payload[2] == 'R' || packet->payload[2] == 'r')
                    && (packet->payload[3] == 'R' || packet->payload[3] == 'r')))) {
        // +OK or -ERR seen
        flow->l4.tcp.mail_pop_stage += 1;
    } else if (!ndpi_int_mail_pop_check_for_client_commands(ndpi_struct, flow)) {
        goto maybe_split_pop;
    }

    if (packet->payload_packet_len > 2 && ntohs(get_u_int16_t(packet->payload, packet->payload_packet_len - 2)) == 0x0d0a) {

        // count the bits set in the bitmask
        if (flow->l4.tcp.pop_command_bitmask != 0) {
            for (a = 0; a < 16; a++) {
                bit_count += (flow->l4.tcp.pop_command_bitmask >> a) & 0x01;
            }
        }

        NDPI_LOG_DBG2(ndpi_struct,
                "mail_pop +OK/-ERR responses: %u, unique commands: %u\n", flow->l4.tcp.mail_pop_stage, bit_count);

        if ((bit_count + flow->l4.tcp.mail_pop_stage) >= 3) {
            if (flow->l4.tcp.mail_pop_stage > 0) {
                NDPI_LOG_INFO(ndpi_struct, "mail_pop identified\n");
                ndpi_int_mail_pop_add_connection(ndpi_struct, flow);
                return;
            } else {
                return;
            }
        } else {
            return;
        }

    } else {
        // first part of a split packet
        NDPI_LOG_DBG2(ndpi_struct,
                "mail_pop command without line ending -> skip\n");
        return;
    }


maybe_split_pop:

    if (((packet->payload_packet_len > 2 && ntohs(get_u_int16_t(packet->payload, packet->payload_packet_len - 2)) == 0x0d0a)
                || flow->l4.tcp.pop_command_bitmask != 0 || flow->l4.tcp.mail_pop_stage != 0) && flow->packet_counter < 12) {
        // maybe part of a split pop packet
        NDPI_LOG_DBG2(ndpi_struct,
                "maybe part of split mail_pop packet -> skip\n");
        return;
    }

    NDPI_EXCLUDE_PROTO(ndpi_struct, flow);
}


void init_mail_pop_dissector(struct ndpi_detection_module_struct *ndpi_struct, u_int32_t *id, NDPI_PROTOCOL_BITMASK *detection_bitmask)
{
    ndpi_set_bitmask_protocol_detection("MAIL_POP", ndpi_struct, detection_bitmask, *id,
            NDPI_PROTOCOL_MAIL_POP,
            ndpi_search_mail_pop_tcp,
            NDPI_SELECTION_BITMASK_PROTOCOL_V4_V6_TCP_WITH_PAYLOAD_WITHOUT_RETRANSMISSION,
            SAVE_DETECTION_BITMASK_AS_UNKNOWN,
            ADD_TO_DETECTION_BITMASK);

    *id += 1;
}
