/*
 * mail_smtp.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_SMTP

#include "ndpi_api.h"


#define SMTP_BIT_220		0x01
#define SMTP_BIT_250		0x02
#define SMTP_BIT_235		0x04
#define SMTP_BIT_334		0x08
#define SMTP_BIT_354		0x10
#define SMTP_BIT_HELO_EHLO	0x20
#define SMTP_BIT_MAIL		0x40
#define SMTP_BIT_RCPT		0x80
#define SMTP_BIT_AUTH		0x100
#define SMTP_BIT_STARTTLS	0x200
#define SMTP_BIT_DATA		0x400
#define SMTP_BIT_NOOP		0x800
#define SMTP_BIT_RSET		0x1000
#define SMTP_BIT_TlRM		0x2000

static void ndpi_int_mail_smtp_add_connection(struct ndpi_detection_module_struct
					      *ndpi_struct, struct ndpi_flow_struct *flow)
{
  ndpi_set_detected_protocol(ndpi_struct, flow, NDPI_PROTOCOL_MAIL_SMTP, NDPI_PROTOCOL_UNKNOWN);
}

void ndpi_search_mail_smtp_tcp(struct ndpi_detection_module_struct
			       *ndpi_struct, struct ndpi_flow_struct *flow)
{
  struct ndpi_packet_struct *packet = &flow->packet;
	
  NDPI_LOG_DBG(ndpi_struct, "search mail_smtp\n");

  if (packet->payload_packet_len > 2 && ntohs(get_u_int16_t(packet->payload, packet->payload_packet_len - 2)) == 0x0d0a) {
    u_int8_t a;
    u_int8_t bit_count = 0;

    NDPI_PARSE_PACKET_LINE_INFO(ndpi_struct, flow,packet);
    for (a = 0; a < packet->parsed_lines; a++) {

      // expected server responses
      if (packet->line[a].len >= 3) {
	if (memcmp(packet->line[a].ptr, "220", 3) == 0) {
	  flow->l4.tcp.smtp_command_bitmask |= SMTP_BIT_220;
	} else if (memcmp(packet->line[a].ptr, "250", 3) == 0) {
	  flow->l4.tcp.smtp_command_bitmask |= SMTP_BIT_250;
	} else if (memcmp(packet->line[a].ptr, "235", 3) == 0) {
	  flow->l4.tcp.smtp_command_bitmask |= SMTP_BIT_235;
	} else if (memcmp(packet->line[a].ptr, "334", 3) == 0) {
	  flow->l4.tcp.smtp_command_bitmask |= SMTP_BIT_334;
	} else if (memcmp(packet->line[a].ptr, "354", 3) == 0) {
	  flow->l4.tcp.smtp_command_bitmask |= SMTP_BIT_354;
	}
      }
      // expected client requests
      if (packet->line[a].len >= 5) {
	if ((((packet->line[a].ptr[0] == 'H' || packet->line[a].ptr[0] == 'h')
	      && (packet->line[a].ptr[1] == 'E' || packet->line[a].ptr[1] == 'e'))
	     || ((packet->line[a].ptr[0] == 'E' || packet->line[a].ptr[0] == 'e')
		 && (packet->line[a].ptr[1] == 'H' || packet->line[a].ptr[1] == 'h')))
	    && (packet->line[a].ptr[2] == 'L' || packet->line[a].ptr[2] == 'l')
	    && (packet->line[a].ptr[3] == 'O' || packet->line[a].ptr[3] == 'o')
	    && packet->line[a].ptr[4] == ' ') {
	  flow->l4.tcp.smtp_command_bitmask |= SMTP_BIT_HELO_EHLO;
	} else if ((packet->line[a].ptr[0] == 'M' || packet->line[a].ptr[0] == 'm')
		   && (packet->line[a].ptr[1] == 'A' || packet->line[a].ptr[1] == 'a')
		   && (packet->line[a].ptr[2] == 'I' || packet->line[a].ptr[2] == 'i')
		   && (packet->line[a].ptr[3] == 'L' || packet->line[a].ptr[3] == 'l')
		   && packet->line[a].ptr[4] == ' ') {
	  flow->l4.tcp.smtp_command_bitmask |= SMTP_BIT_MAIL;
	} else if ((packet->line[a].ptr[0] == 'R' || packet->line[a].ptr[0] == 'r')
		   && (packet->line[a].ptr[1] == 'C' || packet->line[a].ptr[1] == 'c')
		   && (packet->line[a].ptr[2] == 'P' || packet->line[a].ptr[2] == 'p')
		   && (packet->line[a].ptr[3] == 'T' || packet->line[a].ptr[3] == 't')
		   && packet->line[a].ptr[4] == ' ') {
	  flow->l4.tcp.smtp_command_bitmask |= SMTP_BIT_RCPT;
	} else if ((packet->line[a].ptr[0] == 'A' || packet->line[a].ptr[0] == 'a')
		   && (packet->line[a].ptr[1] == 'U' || packet->line[a].ptr[1] == 'u')
		   && (packet->line[a].ptr[2] == 'T' || packet->line[a].ptr[2] == 't')
		   && (packet->line[a].ptr[3] == 'H' || packet->line[a].ptr[3] == 'h')
		   && packet->line[a].ptr[4] == ' ') {
	  flow->l4.tcp.smtp_command_bitmask |= SMTP_BIT_AUTH;
	}
      }

      if (packet->line[a].len >= 8) {
	if ((packet->line[a].ptr[0] == 'S' || packet->line[a].ptr[0] == 's')
	    && (packet->line[a].ptr[1] == 'T' || packet->line[a].ptr[1] == 't')
	    && (packet->line[a].ptr[2] == 'A' || packet->line[a].ptr[2] == 'a')
	    && (packet->line[a].ptr[3] == 'R' || packet->line[a].ptr[3] == 'r')
	    && (packet->line[a].ptr[4] == 'T' || packet->line[a].ptr[4] == 't')
	    && (packet->line[a].ptr[5] == 'T' || packet->line[a].ptr[5] == 't')
	    && (packet->line[a].ptr[6] == 'L' || packet->line[a].ptr[6] == 'l')
	    && (packet->line[a].ptr[7] == 'S' || packet->line[a].ptr[7] == 's')) {
	  flow->l4.tcp.smtp_command_bitmask |= SMTP_BIT_STARTTLS;
	}
      }

      if (packet->line[a].len >= 4) {
	if ((packet->line[a].ptr[0] == 'D' || packet->line[a].ptr[0] == 'd')
	    && (packet->line[a].ptr[1] == 'A' || packet->line[a].ptr[1] == 'a')
	    && (packet->line[a].ptr[2] == 'T' || packet->line[a].ptr[2] == 't')
	    && (packet->line[a].ptr[3] == 'A' || packet->line[a].ptr[3] == 'a')) {
	  flow->l4.tcp.smtp_command_bitmask |= SMTP_BIT_DATA;
	} else if ((packet->line[a].ptr[0] == 'N' || packet->line[a].ptr[0] == 'n')
		   && (packet->line[a].ptr[1] == 'O' || packet->line[a].ptr[1] == 'o')
		   && (packet->line[a].ptr[2] == 'O' || packet->line[a].ptr[2] == 'o')
		   && (packet->line[a].ptr[3] == 'P' || packet->line[a].ptr[3] == 'p')) {
	  flow->l4.tcp.smtp_command_bitmask |= SMTP_BIT_NOOP;
	} else if ((packet->line[a].ptr[0] == 'R' || packet->line[a].ptr[0] == 'r')
		   && (packet->line[a].ptr[1] == 'S' || packet->line[a].ptr[1] == 's')
		   && (packet->line[a].ptr[2] == 'E' || packet->line[a].ptr[2] == 'e')
		   && (packet->line[a].ptr[3] == 'T' || packet->line[a].ptr[3] == 't')) {
	  flow->l4.tcp.smtp_command_bitmask |= SMTP_BIT_RSET;
	}
      }

    }

    // now count the bits set in the bitmask
    if (flow->l4.tcp.smtp_command_bitmask != 0) {
      for (a = 0; a < 16; a++) {
	bit_count += (flow->l4.tcp.smtp_command_bitmask >> a) & 0x01;
      }
    }
    NDPI_LOG_DBG2(ndpi_struct, "seen smtp commands and responses: %u\n",
	     bit_count);

    if (bit_count >= 3) {
      NDPI_LOG_INFO(ndpi_struct, "mail smtp identified\n");
      ndpi_int_mail_smtp_add_connection(ndpi_struct, flow);
      return;
    }
    if (bit_count >= 1 && flow->packet_counter < 12) {
      return;
    }
  }
  /* when the first or second packets are split into two packets, those packets are ignored. */
  if (flow->packet_counter <= 4 &&
      packet->payload_packet_len >= 4 &&
      (ntohs(get_u_int16_t(packet->payload, packet->payload_packet_len - 2)) == 0x0d0a
       || memcmp(packet->payload, "220", 3) == 0 || memcmp(packet->payload, "EHLO", 4) == 0)) {
    NDPI_LOG_DBG2(ndpi_struct, "maybe SMTP, need next packet\n");
    return;
  }

  NDPI_EXCLUDE_PROTO(ndpi_struct, flow);

}

void init_mail_smtp_dissector(struct ndpi_detection_module_struct *ndpi_struct, u_int32_t *id, NDPI_PROTOCOL_BITMASK *detection_bitmask)
{
  ndpi_set_bitmask_protocol_detection("MAIL_SMTP", ndpi_struct, detection_bitmask, *id,
				      NDPI_PROTOCOL_MAIL_SMTP,
				      ndpi_search_mail_smtp_tcp,
				      NDPI_SELECTION_BITMASK_PROTOCOL_V4_V6_TCP_WITH_PAYLOAD_WITHOUT_RETRANSMISSION,
				      SAVE_DETECTION_BITMASK_AS_UNKNOWN,
				      ADD_TO_DETECTION_BITMASK);  

  *id += 1;
}

