/*
 * stun.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_STUN

#include "ndpi_api.h"

#define MAX_NUM_STUN_PKTS     8

// #define DEBUG_STUN 1

struct stun_packet_header {
  u_int16_t msg_type, msg_len;
  u_int32_t cookie;
  u_int8_t  transaction_id[8];
};

/* ************************************************************ */

static void ndpi_int_stun_add_connection(struct ndpi_detection_module_struct *ndpi_struct,
					 u_int proto, struct ndpi_flow_struct *flow) {
  ndpi_set_detected_protocol(ndpi_struct, flow, proto, NDPI_PROTOCOL_UNKNOWN);
}

typedef enum {
  NDPI_IS_STUN,
  NDPI_IS_NOT_STUN
} ndpi_int_stun_t;

/* ************************************************************ */

static int is_google_ip_address(u_int32_t host) {
  if(
     ((host & 0xFFFF0000 /* 255.255.0.0 */) == 0x4A7D0000 /* 74.125.0.0/16 */)
     || ((host & 0xFFFF0000 /* 255.255.0.0 */) == 0x42660000 /* 66.102.0.0/16 */)
     )
    return(1);
  else
    return(0);
}

/* ************************************************************ */

/*
 WhatsApp
 31.13.86.48
 31.13.92.50
 157.240.20.51
 157.240.21.51
 185.60.216.51

 Messenger
 31.13.86.5
*/

static int is_messenger_ip_address(u_int32_t host) {
  if(host == 0x1F0D5605 /* 31.13.86.5 */)
    return(1);
  else
    return(0);
}

/* ************************************************************ */

static ndpi_int_stun_t ndpi_int_check_stun(struct ndpi_detection_module_struct *ndpi_struct,
					   struct ndpi_flow_struct *flow,
					   const u_int8_t * payload,
					   const u_int16_t payload_length,
					   u_int8_t *is_whatsapp,
					   u_int8_t *is_messenger,
					   u_int8_t *is_duo
					   ) {
  u_int16_t msg_type, msg_len;
  struct stun_packet_header *h = (struct stun_packet_header*)payload;
  u_int8_t can_this_be_whatsapp_voice = 1;

  /* STUN over TCP does not look good */
  if(flow->packet.tcp) return(NDPI_IS_NOT_STUN);

  *is_whatsapp = 0, *is_messenger = 0, *is_duo = 0;

  if(payload_length < sizeof(struct stun_packet_header)) {
    /* This looks like an invlid packet */

    if(flow->protos.stun_ssl.stun.num_udp_pkts > 0) {
      *is_whatsapp = 1;
      return(NDPI_IS_STUN); /* This is WhatsApp Voice */
    } else
      return(NDPI_IS_NOT_STUN);
  }

  if((strncmp((const char*)payload, (const char*)"RSP/", 4) == 0)
     && (strncmp((const char*)&payload[7], (const char*)" STUN_", 6) == 0)) {
    NDPI_LOG_INFO(ndpi_struct, "found stun\n");
    goto udp_stun_found;
  }

  msg_type = ntohs(h->msg_type) /* & 0x3EEF */, msg_len = ntohs(h->msg_len);

  /* https://www.iana.org/assignments/stun-parameters/stun-parameters.xhtml */
  if(msg_type > 0x000C)
    return(NDPI_IS_NOT_STUN);

  if(msg_type == 0x01 /* Binding Request */) {
    flow->protos.stun_ssl.stun.num_binding_requests++;
    if((msg_len == 0) && (flow->guessed_host_protocol_id == NDPI_PROTOCOL_GOOGLE)) {
      flow->guessed_host_protocol_id = NDPI_PROTOCOL_HANGOUT_DUO;
    }
  }

  if((msg_len == 0) && (flow->guessed_host_protocol_id == NDPI_PROTOCOL_UNKNOWN)) {
    NDPI_EXCLUDE_PROTO(ndpi_struct, flow);
    return(NDPI_IS_NOT_STUN);
  }
  
  flow->protos.stun_ssl.stun.num_udp_pkts++;

  /*
    printf("[msg_type: %04X][payload_length: %u][num_binding_request: %u]\n",
           msg_type, payload_length, flow->protos.stun_ssl.stun.num_binding_requests);
  */

  if(((payload[0] == 0x80)
      && (payload_length < 512)
      && ((msg_len+20) <= payload_length)) /* WhatsApp Voice */) {
    *is_whatsapp = 1;
    return(NDPI_IS_STUN); /* This is WhatsApp Voice */
  } else if((payload[0] == 0x90)
	    && (((msg_len+11) == payload_length) /* WhatsApp Video */
		|| (flow->protos.stun_ssl.stun.num_binding_requests >= 4))) {
    *is_whatsapp = 2;
    return(NDPI_IS_STUN); /* This is WhatsApp Video */
  }

  if((payload[0] != 0x80) && ((msg_len+20) > payload_length))
    return(NDPI_IS_NOT_STUN);
  else
    flow->guessed_protocol_id = NDPI_PROTOCOL_STUN;
  
  if(payload_length == (msg_len+20)) {
    if(msg_type <= 0x000b) /* http://www.3cx.com/blog/voip-howto/stun-details/ */ {
      u_int offset = 20;

      // printf("[%02X][%02X][%02X][%02X][payload_length: %u]\n", payload[offset], payload[offset+1], payload[offset+2], payload[offset+3],payload_length);

      /*
	This can either be the standard RTCP or Ms Lync RTCP that
	later will become Ms Lync RTP. In this case we need to
	be careful before deciding about the protocol before dissecting the packet

	MS Lync = Skype
	https://en.wikipedia.org/wiki/Skype_for_Business
      */

      while((offset+2) < payload_length) {
	u_int16_t attribute = ntohs(*((u_int16_t*)&payload[offset]));
	u_int16_t len = ntohs(*((u_int16_t*)&payload[offset+2]));
	u_int16_t x = (len + 4) % 4;

	if(x != 0)
	  len += 4-x;

	switch(attribute) {
	case 0x0008: /* Message Integrity */
	case 0x0020: /* XOR-MAPPED-ADDRESSES */
	case 0x4000:
	case 0x4001:
	case 0x4002:
	  /* These are the only messages apparently whatsapp voice can use */
	  break;

	case 0xC057: /* Messeger */
	  if(msg_type == 0x0001) {
	    if((msg_len == 100) || (msg_len == 104)) {
	      *is_messenger = 1;
	      return(NDPI_IS_STUN);
	    } else if(msg_len == 76) {
	      *is_duo = 1;
	      return(NDPI_IS_STUN);
	    }
	  }
	  break;

	case 0x8054: /* Candidate Identifier */
	  if((len == 4)
	     && ((offset+7) < payload_length)
	     && (payload[offset+5] == 0x00)
	     && (payload[offset+6] == 0x00)
	     && (payload[offset+7] == 0x00)) {
	    /* Either skype for business or "normal" skype with multiparty call */
	    flow->protos.stun_ssl.stun.is_skype = 1;
	    return(NDPI_IS_STUN);
	  }
	  break;

	case 0x8055: /* MS Service Quality (skype?) */
	  break;

	  /* Proprietary fields found on skype calls */
	case 0x24DF:
	case 0x3802:
	case 0x8036:
	case 0x8095:
	case 0x0800:
	  /* printf("====>>>> %04X\n", attribute); */
	  flow->protos.stun_ssl.stun.is_skype = 1;
	  return(NDPI_IS_STUN);
	  break;

	case 0x8070: /* Implementation Version */
	  if((len == 4)
	     && ((offset+7) < payload_length)
	     && (payload[offset+4] == 0x00)
	     && (payload[offset+5] == 0x00)
	     && (payload[offset+6] == 0x00)
	     && ((payload[offset+7] == 0x02) || (payload[offset+7] == 0x03))
	     ) {
	    flow->protos.stun_ssl.stun.is_skype = 1;
	    return(NDPI_IS_STUN);
	  }
	  break;

	case 0xFF03:
	  can_this_be_whatsapp_voice = 0;
	  flow->guessed_host_protocol_id = NDPI_PROTOCOL_HANGOUT_DUO;
	  break;
	  
	default:
	  /* This means this STUN packet cannot be confused with whatsapp voice */
#ifdef DEBUG_STUN
	  printf("==> %04X\n", attribute);
#endif
	  can_this_be_whatsapp_voice = 0;
	  break;
	}

	offset += len + 4;
      }
      goto udp_stun_found;
    } else if(msg_type == 0x0800) {
      *is_whatsapp = 1;
      return(NDPI_IS_STUN); /* This is WhatsApp */
    }
  }

  if((flow->protos.stun_ssl.stun.num_udp_pkts > 0) && (msg_type <= 0x00FF)) {
    *is_whatsapp = 1;
    return(NDPI_IS_STUN); /* This is WhatsApp Voice */
  } else
    return(NDPI_IS_NOT_STUN);

 udp_stun_found:
  if(can_this_be_whatsapp_voice) {
    struct ndpi_packet_struct *packet = &flow->packet;
    
    flow->protos.stun_ssl.stun.num_processed_pkts++;
#ifdef DEBUG_STUN
    printf("==>> NDPI_PROTOCOL_WHATSAPP_VOICE\n");
#endif

    if((ntohs(packet->udp->source) == 3478) || (ntohs(packet->udp->dest) == 3478)) {           
      flow->guessed_host_protocol_id = (is_messenger_ip_address(ntohl(packet->iph->saddr)) || is_messenger_ip_address(ntohl(packet->iph->daddr))) ?
	NDPI_PROTOCOL_MESSENGER : NDPI_PROTOCOL_WHATSAPP_VOICE;
    } else
      flow->guessed_host_protocol_id = (is_google_ip_address(ntohl(packet->iph->saddr)) || is_google_ip_address(ntohl(packet->iph->daddr)))
					? NDPI_PROTOCOL_HANGOUT_DUO : NDPI_PROTOCOL_WHATSAPP_VOICE;
    return((flow->protos.stun_ssl.stun.num_udp_pkts < MAX_NUM_STUN_PKTS) ? NDPI_IS_NOT_STUN : NDPI_IS_STUN);
  } else {
    /*
      We cannot immediately say that this is STUN as there are other protocols
      like GoogleHangout that might be candidates, thus we set the
      guessed protocol to STUN
    */
    return(NDPI_IS_NOT_STUN);
  }
}

void ndpi_search_stun(struct ndpi_detection_module_struct *ndpi_struct, struct ndpi_flow_struct *flow)
{
  struct ndpi_packet_struct *packet = &flow->packet;
  u_int8_t is_whatsapp = 0, is_messenger = 0, is_duo = 0;

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

  if(packet->payload == NULL)
    return;
  else if(packet->iphv6 != NULL) {
    NDPI_EXCLUDE_PROTO(ndpi_struct, flow);
    return;
  }

  if(packet->tcp) {
    /* STUN may be encapsulated in TCP packets */
    if((packet->payload_packet_len >= 22)
       && ((ntohs(get_u_int16_t(packet->payload, 0)) + 2) == packet->payload_packet_len)) {
      /* TODO there could be several STUN packets in a single TCP packet so maybe the detection could be
       * improved by checking only the STUN packet of given length */

      if(ndpi_int_check_stun(ndpi_struct, flow, packet->payload + 2,
			     packet->payload_packet_len - 2,
			     &is_whatsapp, &is_messenger, &is_duo) == NDPI_IS_STUN) {
	if(flow->guessed_protocol_id == 0) flow->guessed_protocol_id = NDPI_PROTOCOL_STUN;

	if(is_messenger) {
	  ndpi_set_detected_protocol(ndpi_struct, flow, NDPI_PROTOCOL_MESSENGER, NDPI_PROTOCOL_STUN);
	  return;
	} else if(is_duo) {
	  ndpi_set_detected_protocol(ndpi_struct, flow, NDPI_PROTOCOL_HANGOUT_DUO, NDPI_PROTOCOL_STUN);
	  return;
	} else if(flow->protos.stun_ssl.stun.is_skype) {
	  NDPI_LOG_INFO(ndpi_struct, "found Skype\n");

	  if((flow->protos.stun_ssl.stun.num_processed_pkts >= 8) || (flow->protos.stun_ssl.stun.num_binding_requests >= 4))
	    ndpi_set_detected_protocol(ndpi_struct, flow, NDPI_PROTOCOL_SKYPE_CALL, NDPI_PROTOCOL_SKYPE);
	} else {
	  NDPI_LOG_INFO(ndpi_struct, "found UDP stun\n"); /* Ummmmm we're in the TCP branch. This code looks bad */
	  ndpi_int_stun_add_connection(ndpi_struct,
				       is_whatsapp ? (is_whatsapp == 1 ? NDPI_PROTOCOL_WHATSAPP_VOICE : NDPI_PROTOCOL_WHATSAPP_VIDEO) : NDPI_PROTOCOL_STUN, flow);
	}

	return;
      }
    }
  }

  /* UDP */
  if(ndpi_int_check_stun(ndpi_struct, flow, packet->payload,
			 packet->payload_packet_len,
			 &is_whatsapp, &is_messenger, &is_duo) == NDPI_IS_STUN) {
    if(flow->guessed_protocol_id == 0) flow->guessed_protocol_id = NDPI_PROTOCOL_STUN;

    if(is_messenger) {
      ndpi_set_detected_protocol(ndpi_struct, flow, NDPI_PROTOCOL_MESSENGER, NDPI_PROTOCOL_STUN);
      return;
    } else if(is_duo) {
      ndpi_set_detected_protocol(ndpi_struct, flow, NDPI_PROTOCOL_HANGOUT_DUO, NDPI_PROTOCOL_STUN);
      return;
    } else if(flow->protos.stun_ssl.stun.is_skype) {
      NDPI_LOG_INFO(ndpi_struct, "Found Skype\n");

      /* flow->protos.stun_ssl.stun.num_binding_requests < 4) ? NDPI_PROTOCOL_SKYPE_CALL_IN : NDPI_PROTOCOL_SKYPE_CALL_OUT */
      if((flow->protos.stun_ssl.stun.num_processed_pkts >= 8) || (flow->protos.stun_ssl.stun.num_binding_requests >= 4))
	ndpi_set_detected_protocol(ndpi_struct, flow, NDPI_PROTOCOL_SKYPE_CALL, NDPI_PROTOCOL_SKYPE);
    } else {
      NDPI_LOG_INFO(ndpi_struct, "found UDP stun\n");
      ndpi_int_stun_add_connection(ndpi_struct,
				   is_whatsapp ? (is_whatsapp == 1 ? NDPI_PROTOCOL_WHATSAPP_VOICE : NDPI_PROTOCOL_WHATSAPP_VIDEO)
				   : NDPI_PROTOCOL_STUN,
				   flow);
    }

    return;
  }

  if(flow->protos.stun_ssl.stun.num_udp_pkts >= MAX_NUM_STUN_PKTS)
    NDPI_EXCLUDE_PROTO(ndpi_struct, flow);

  if(flow->packet_counter > 0) {
    /* This might be a RTP stream: let's make sure we check it */
    NDPI_CLR(&flow->excluded_protocol_bitmask, NDPI_PROTOCOL_RTP);
  }
}


void init_stun_dissector(struct ndpi_detection_module_struct *ndpi_struct, u_int32_t *id,
			 NDPI_PROTOCOL_BITMASK *detection_bitmask) {
  ndpi_set_bitmask_protocol_detection("STUN", ndpi_struct, detection_bitmask, *id,
				      NDPI_PROTOCOL_STUN,
				      ndpi_search_stun,
				      NDPI_SELECTION_BITMASK_PROTOCOL_TCP_OR_UDP_WITH_PAYLOAD,
				      SAVE_DETECTION_BITMASK_AS_UNKNOWN,
				      ADD_TO_DETECTION_BITMASK);

  *id += 1;
}