nDPI/src/lib/protocols/ssl.c

/*
 * ssl.c
 *
 * Copyright (C) 2009-2011 by ipoque GmbH
 * Copyright (C) 2011-15 - 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_api.h"

// #define CERTIFICATE_DEBUG 1

#ifdef NDPI_PROTOCOL_SSL

#define NDPI_MAX_SSL_REQUEST_SIZE 10000

/* Skype.c */
extern u_int8_t is_skype_flow(struct ndpi_detection_module_struct *ndpi_struct,
			      struct ndpi_flow_struct *flow);

static void ndpi_int_ssl_add_connection(struct ndpi_detection_module_struct *ndpi_struct,
					struct ndpi_flow_struct *flow, u_int32_t protocol)
{
  if((protocol != NDPI_PROTOCOL_SSL)
     && (protocol != NDPI_PROTOCOL_SSL_NO_CERT)) {
    ndpi_int_add_connection(ndpi_struct, flow, protocol, NDPI_CORRELATED_PROTOCOL);
  } else {
    struct ndpi_packet_struct *packet = &flow->packet;

    if((flow->protos.ssl.client_certificate[0] != '\0')
       || (flow->protos.ssl.server_certificate[0] != '\0')
       || (flow->host_server_name[0] != '\0'))
      protocol = NDPI_PROTOCOL_SSL;
    else
      protocol =  NDPI_PROTOCOL_SSL_NO_CERT;

    if(packet->tcp != NULL) {
      switch(protocol) {
      case NDPI_PROTOCOL_SSL:
      case NDPI_PROTOCOL_SSL_NO_CERT:
	{
	  /*
	     In case of SSL there are probably sub-protocols
	     such as IMAPS that can be otherwise detected
	  */
	  u_int16_t sport = ntohs(packet->tcp->source);
	  u_int16_t dport = ntohs(packet->tcp->dest);

	  if((sport == 465) || (dport == 465))      protocol = NDPI_PROTOCOL_MAIL_SMTPS;
	  else if((sport == 993) || (dport == 993)) protocol = NDPI_PROTOCOL_MAIL_IMAPS;
	  else if((sport == 995) || (dport == 995)) protocol = NDPI_PROTOCOL_MAIL_POPS;
	}
	break;
      }

      if((protocol == NDPI_PROTOCOL_SSL_NO_CERT)
	 && is_skype_flow(ndpi_struct, flow)) {
	protocol = NDPI_PROTOCOL_SKYPE;
      }
    }

    ndpi_int_add_connection(ndpi_struct, flow, protocol, NDPI_REAL_PROTOCOL);
  }
}

/* Can't call libc functions from kernel space, define some stub instead */

#define ndpi_isalpha(ch) (((ch) >= 'a' && (ch) <= 'z') || ((ch) >= 'A' && (ch) <= 'Z'))
#define ndpi_isdigit(ch) ((ch) >= '0' && (ch) <= '9')
#define ndpi_isspace(ch) (((ch) >= '\t' && (ch) <= '\r') || ((ch) == ' '))
#define ndpi_isprint(ch) ((ch) >= 0x20 && (ch) <= 0x7e)
#define ndpi_ispunct(ch) (((ch) >= '!' && (ch) <= '/') || \
                     ((ch) >= ':' && (ch) <= '@') || \
                     ((ch) >= '[' && (ch) <= '`') || \
                     ((ch) >= '{' && (ch) <= '~'))

static void stripCertificateTrailer(char *buffer, int buffer_len) {
  int i;

  //  printf("->%s<-\n", buffer);

  for(i=0; i<buffer_len; i++) {
    // printf("%c [%d]\n", buffer[i], buffer[i]);

    if((buffer[i] != '.')
       && (buffer[i] != '-')
       && (buffer[i] != '*')
       && (!ndpi_isalpha(buffer[i]))
       && (!ndpi_isdigit(buffer[i]))) {
      buffer[i] = '\0';
      buffer_len = i;
      break;
    }
  }

  if(i > 0) i--;

  while(i > 0) {
    if(!ndpi_isalpha(buffer[i])) {
      buffer[i] = '\0';
      buffer_len = i;
      i--;
    } else
      break;
  }

  for(i=buffer_len; i>0; i--) {
    if(buffer[i] == '.') break;
    else if(ndpi_isdigit(buffer[i]))
      buffer[i] = '\0', buffer_len = i;
  }
}

/* Code fixes courtesy of Alexsandro Brahm <alex@digistar.com.br> */
int getSSLcertificate(struct ndpi_detection_module_struct *ndpi_struct,
		      struct ndpi_flow_struct *flow,
		      char *buffer, int buffer_len) {
  struct ndpi_packet_struct *packet = &flow->packet;

  /*
    Nothing matched so far: let's decode the certificate with some heuristics
    Patches courtesy of Denys Fedoryshchenko <nuclearcat@nuclearcat.com>
   */
  if(packet->payload[0] == 0x16 /* Handshake */) {
    u_int16_t total_len  = (packet->payload[3] << 8) + packet->payload[4] + 5 /* SSL Header */;
    u_int8_t handshake_protocol = packet->payload[5]; /* handshake protocol a bit misleading, it is message type according TLS specs */

    memset(buffer, 0, buffer_len);

    /* Truncate total len, search at least in incomplete packet */
    if (total_len > packet->payload_packet_len)
	total_len = packet->payload_packet_len;

    /* At least "magic" 3 bytes, null for string end, otherwise no need to waste cpu cycles */
    if(total_len > 4) {
      int i;

      if(handshake_protocol == 0x02 || handshake_protocol == 0xb /* Server Hello and Certificate message types are interesting for us */) {
	u_int num_found = 0;

	flow->l4.tcp.ssl_seen_server_cert = 1;

	/* Check after handshake protocol header (5 bytes) and message header (4 bytes) */
	for(i = 9; i < packet->payload_packet_len-3; i++) {
	  if(((packet->payload[i] == 0x04) && (packet->payload[i+1] == 0x03) && (packet->payload[i+2] == 0x0c))
	     || ((packet->payload[i] == 0x55) && (packet->payload[i+1] == 0x04) && (packet->payload[i+2] == 0x03))) {
	    u_int8_t server_len = packet->payload[i+3];

	    if(packet->payload[i] == 0x55) {
	      num_found++;

	      if(num_found != 2) continue;
	    }

	    if(server_len+i+3 < packet->payload_packet_len) {
	      char *server_name = (char*)&packet->payload[i+4];
	      u_int8_t begin = 0, len, j, num_dots;

	      while(begin < server_len) {
		if(!ndpi_isprint(server_name[begin]))
		  begin++;
		else
		  break;
	      }

	      // len = ndpi_min(server_len-begin, buffer_len-1);
	      len = buffer_len-1;
	      strncpy(buffer, &server_name[begin], len);
	      buffer[len] = '\0';

	      /* We now have to check if this looks like an IP address or host name */
	      for(j=0, num_dots = 0; j<len; j++) {
		if(!ndpi_isprint((buffer[j]))) {
		  num_dots = 0; /* This is not what we look for */
		  break;
		} else if(buffer[j] == '.') {
		  num_dots++;
		  if(num_dots >=2) break;
		}
	      }

	      if(num_dots >= 2) {
		stripCertificateTrailer(buffer, buffer_len);
		snprintf(flow->protos.ssl.server_certificate,
			 sizeof(flow->protos.ssl.server_certificate), "%s", buffer);
		return(1 /* Server Certificate */);
	      }
	    }
	  }
	}
      } else if(handshake_protocol == 0x01 /* Client Hello */) {
	u_int offset, base_offset = 43;
	u_int16_t session_id_len = packet->payload[base_offset];

	if((session_id_len+base_offset+2) <= total_len) {
	  u_int16_t cypher_len =  packet->payload[session_id_len+base_offset+2] + (packet->payload[session_id_len+base_offset+1] << 8);
	  offset = base_offset + session_id_len + cypher_len + 2;

	  flow->l4.tcp.ssl_seen_client_cert = 1;

	  if(offset < total_len) {
	    u_int16_t compression_len;
	    u_int16_t extensions_len;

	    compression_len = packet->payload[offset+1];
	    offset += compression_len + 3;

	    if(offset < total_len) {
	      extensions_len = packet->payload[offset];

	      if((extensions_len+offset) < total_len) {
		u_int16_t extension_offset = 1; /* Move to the first extension */

		while(extension_offset < extensions_len) {
		  u_int16_t extension_id, extension_len;

		  memcpy(&extension_id, &packet->payload[offset+extension_offset], 2);
		  extension_offset += 2;

		  memcpy(&extension_len, &packet->payload[offset+extension_offset], 2);
		  extension_offset += 2;

		  extension_id = ntohs(extension_id), extension_len = ntohs(extension_len);

		  if(extension_id == 0) {
		    u_int begin = 0,len;
		    char *server_name = (char*)&packet->payload[offset+extension_offset];

		    while(begin < extension_len) {
		      if((!ndpi_isprint(server_name[begin]))
			 || ndpi_ispunct(server_name[begin])
			 || ndpi_isspace(server_name[begin]))
			begin++;
		      else
			break;
		    }

		    len = (u_int)ndpi_min(extension_len-begin, buffer_len-1);
		    strncpy(buffer, &server_name[begin], len);
		    buffer[len] = '\0';
		    stripCertificateTrailer(buffer, buffer_len);

		    snprintf(flow->protos.ssl.client_certificate,
			     sizeof(flow->protos.ssl.client_certificate), "%s", buffer);

		    /* We're happy now */
		    return(2 /* Client Certificate */);
		  }

		  extension_offset += extension_len;
		}
	      }
	    }
	  }
	}
      }
    }
  }

  return(0); /* Not found */
}

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

  if(!packet->iph /* IPv4 */) return(-1);

  if((packet->detected_protocol_stack[0] == NDPI_PROTOCOL_UNKNOWN)
     || (packet->detected_protocol_stack[0] == NDPI_PROTOCOL_SSL)) {
    char certificate[64];
    int rc;

    certificate[0] = '\0';
    rc = getSSLcertificate(ndpi_struct, flow, certificate, sizeof(certificate));
    packet->ssl_certificate_num_checks++;

    if(rc > 0) {
      packet->ssl_certificate_detected++;
#ifdef CERTIFICATE_DEBUG
      printf("***** [SSL] %s\n", certificate);
#endif

      if(ndpi_match_string_subprotocol(ndpi_struct, flow, certificate, strlen(certificate)) != NDPI_PROTOCOL_UNKNOWN)
	return(rc); /* Fix courtesy of Gianluca Costa <g.costa@xplico.org> */

#ifdef NDPI_PROTOCOL_TOR
      if(ndpi_is_ssl_tor(ndpi_struct, flow, certificate) != 0)
	return(rc);
#endif
    }

    if(((packet->ssl_certificate_num_checks >= 2)
	&& flow->l4.tcp.seen_syn
	&& flow->l4.tcp.seen_syn_ack
	&& flow->l4.tcp.seen_ack /* We have seen the 3-way handshake */)
       || (flow->protos.ssl.server_certificate[0] != '\0')
       || (flow->protos.ssl.client_certificate[0] != '\0')
       )
      ndpi_int_ssl_add_connection(ndpi_struct, flow, NDPI_PROTOCOL_SSL);
  }

  return(0);
}

static void ssl_mark_and_payload_search_for_other_protocols(struct
							    ndpi_detection_module_struct
							    *ndpi_struct, struct ndpi_flow_struct *flow)
{
#if defined(NDPI_PROTOCOL_MEEBO)|| defined(NDPI_PROTOCOL_TOR) || defined(NDPI_PROTOCOL_VPN_X) || defined(NDPI_PROTOCOL_UNENCRYPED_JABBER) || defined (NDPI_PROTOCOL_OSCAR) || defined (NDPI_PROTOCOL_ITUNES) || defined (NDPI_SERVICE_GMAIL)
  struct ndpi_packet_struct *packet = &flow->packet;
  //      struct ndpi_id_struct         *src=flow->src;
  //      struct ndpi_id_struct         *dst=flow->dst;
  u_int32_t a;
  u_int32_t end;
#if defined(NDPI_PROTOCOL_UNENCRYPED_JABBER)
  if (NDPI_COMPARE_PROTOCOL_TO_BITMASK(ndpi_struct->detection_bitmask, NDPI_PROTOCOL_UNENCRYPED_JABBER) != 0)
    goto check_for_ssl_payload;
#endif
#if defined(NDPI_PROTOCOL_OSCAR)
  if (NDPI_COMPARE_PROTOCOL_TO_BITMASK(ndpi_struct->detection_bitmask, NDPI_PROTOCOL_OSCAR) != 0)
    goto check_for_ssl_payload;
#endif
  goto no_check_for_ssl_payload;

 check_for_ssl_payload:
  end = packet->payload_packet_len - 20;
  for (a = 5; a < end; a++) {
#ifdef NDPI_PROTOCOL_UNENCRYPED_JABBER
    if (packet->payload[a] == 't') {
      if (memcmp(&packet->payload[a], "talk.google.com", 15) == 0) {
	NDPI_LOG(NDPI_PROTOCOL_UNENCRYPED_JABBER, ndpi_struct, NDPI_LOG_DEBUG, "ssl jabber packet match\n");
	if (NDPI_COMPARE_PROTOCOL_TO_BITMASK
	    (ndpi_struct->detection_bitmask, NDPI_PROTOCOL_UNENCRYPED_JABBER) != 0) {
	  ndpi_int_ssl_add_connection(ndpi_struct, flow, NDPI_PROTOCOL_UNENCRYPED_JABBER);
	  return;
	}
      }
    }
#endif
#ifdef NDPI_PROTOCOL_OSCAR
    if (packet->payload[a] == 'A' || packet->payload[a] == 'k' || packet->payload[a] == 'c'
	|| packet->payload[a] == 'h') {
      if (((a + 19) < packet->payload_packet_len && memcmp(&packet->payload[a], "America Online Inc.", 19) == 0)
	  //                        || (end - c > 3 memcmp (&packet->payload[c],"AOL", 3) == 0 )
	  //                        || (end - c > 7 && memcmp (&packet->payload[c], "AOL LLC", 7) == 0)
	  || ((a + 15) < packet->payload_packet_len && memcmp(&packet->payload[a], "kdc.uas.aol.com", 15) == 0)
	  || ((a + 14) < packet->payload_packet_len && memcmp(&packet->payload[a], "corehc@aol.net", 14) == 0)
	  || ((a + 41) < packet->payload_packet_len
	      && memcmp(&packet->payload[a], "http://crl.aol.com/AOLMSPKI/aolServerCert", 41) == 0)
	  || ((a + 28) < packet->payload_packet_len
	      && memcmp(&packet->payload[a], "http://ocsp.web.aol.com/ocsp", 28) == 0)
	  || ((a + 32) < packet->payload_packet_len
	      && memcmp(&packet->payload[a], "http://pki-info.aol.com/AOLMSPKI", 32) == 0)) {
	NDPI_LOG(NDPI_PROTOCOL_OSCAR, ndpi_struct, NDPI_LOG_DEBUG, "OSCAR SERVER SSL DETECTED\n");

	if (flow->dst != NULL && packet->payload_packet_len > 75) {
	  memcpy(flow->dst->oscar_ssl_session_id, &packet->payload[44], 32);
	  flow->dst->oscar_ssl_session_id[32] = '\0';
	  flow->dst->oscar_last_safe_access_time = packet->tick_timestamp;
	}

	ndpi_int_ssl_add_connection(ndpi_struct, flow, NDPI_PROTOCOL_OSCAR);
	return;
      }
    }

    if (packet->payload[a] == 'm' || packet->payload[a] == 's') {
      if ((a + 21) < packet->payload_packet_len &&
	  (memcmp(&packet->payload[a], "my.screenname.aol.com", 21) == 0
	   || memcmp(&packet->payload[a], "sns-static.aolcdn.com", 21) == 0)) {
	NDPI_LOG(NDPI_PROTOCOL_OSCAR, ndpi_struct, NDPI_LOG_DEBUG, "OSCAR SERVER SSL DETECTED\n");
	ndpi_int_ssl_add_connection(ndpi_struct, flow, NDPI_PROTOCOL_OSCAR);
	return;
      }
    }
#endif
  }

 no_check_for_ssl_payload:
#endif
  if(packet->detected_protocol_stack[0] == NDPI_PROTOCOL_UNKNOWN) {
    NDPI_LOG(NDPI_PROTOCOL_SSL, ndpi_struct, NDPI_LOG_DEBUG, "found ssl connection.\n");
    sslDetectProtocolFromCertificate(ndpi_struct, flow);

    if(!packet->ssl_certificate_detected
       && (!(flow->l4.tcp.ssl_seen_client_cert && flow->l4.tcp.ssl_seen_server_cert))) {
      /* SSL without certificate (Skype, Ultrasurf?) */
      ndpi_int_ssl_add_connection(ndpi_struct, flow, NDPI_PROTOCOL_SSL_NO_CERT);
    } else
      ndpi_int_ssl_add_connection(ndpi_struct, flow, NDPI_PROTOCOL_SSL);
  }
}


static u_int8_t ndpi_search_sslv3_direction1(struct ndpi_detection_module_struct *ndpi_struct,
					     struct ndpi_flow_struct *flow) {

  struct ndpi_packet_struct *packet = &flow->packet;
  //
  //      struct ndpi_id_struct         *src=flow->src;
  //      struct ndpi_id_struct         *dst=flow->dst;


  if ((packet->payload_packet_len >= 5)
      && (packet->payload[0] == 0x16)
      && (packet->payload[1] == 0x03)
      && ((packet->payload[2] == 0x00)
	  || (packet->payload[2] == 0x01)
	  || (packet->payload[2] == 0x02)
	  || (packet->payload[2] == 0x03)
	  )) {
    u_int32_t temp;
    NDPI_LOG(NDPI_PROTOCOL_SSL, ndpi_struct, NDPI_LOG_DEBUG, "search sslv3\n");
    // SSLv3 Record
    if (packet->payload_packet_len >= 1300) {
      return 1;
    }
    temp = ntohs(get_u_int16_t(packet->payload, 3)) + 5;
    NDPI_LOG(NDPI_PROTOCOL_SSL, ndpi_struct, NDPI_LOG_DEBUG, "temp = %u.\n", temp);
    if (packet->payload_packet_len == temp
	|| (temp < packet->payload_packet_len && packet->payload_packet_len > 500)) {
      return 1;
    }

    if (packet->payload_packet_len < temp && temp < 5000 && packet->payload_packet_len > 9) {
      /* the server hello may be split into small packets */
      u_int32_t cert_start;

      NDPI_LOG(NDPI_PROTOCOL_SSL, ndpi_struct, NDPI_LOG_DEBUG,
	       "maybe SSLv3 server hello split into smaller packets\n");

      /* lets hope at least the server hello and the start of the certificate block are in the first packet */
      cert_start = ntohs(get_u_int16_t(packet->payload, 7)) + 5 + 4;
      NDPI_LOG(NDPI_PROTOCOL_SSL, ndpi_struct, NDPI_LOG_DEBUG, "suspected start of certificate: %u\n",
	       cert_start);

      if (cert_start < packet->payload_packet_len && packet->payload[cert_start] == 0x0b) {
	NDPI_LOG(NDPI_PROTOCOL_SSL, ndpi_struct, NDPI_LOG_DEBUG,
		 "found 0x0b at suspected start of certificate block\n");
	return 2;
      }
    }

    if ((packet->payload_packet_len > temp && packet->payload_packet_len > 100) && packet->payload_packet_len > 9) {
      /* the server hello may be split into small packets and the certificate has its own SSL Record
       * so temp contains only the length for the first ServerHello block */
      u_int32_t cert_start;

      NDPI_LOG(NDPI_PROTOCOL_SSL, ndpi_struct, NDPI_LOG_DEBUG,
	       "maybe SSLv3 server hello split into smaller packets but with seperate record for the certificate\n");

      /* lets hope at least the server hello record and the start of the certificate record are in the first packet */
      cert_start = ntohs(get_u_int16_t(packet->payload, 7)) + 5 + 5 + 4;
      NDPI_LOG(NDPI_PROTOCOL_SSL, ndpi_struct, NDPI_LOG_DEBUG, "suspected start of certificate: %u\n",
	       cert_start);

      if (cert_start < packet->payload_packet_len && packet->payload[cert_start] == 0x0b) {
	NDPI_LOG(NDPI_PROTOCOL_SSL, ndpi_struct, NDPI_LOG_DEBUG,
		 "found 0x0b at suspected start of certificate block\n");
	return 2;
      }
    }


    if (packet->payload_packet_len >= temp + 5 && (packet->payload[temp] == 0x14 || packet->payload[temp] == 0x16)
	&& packet->payload[temp + 1] == 0x03) {
      u_int32_t temp2 = ntohs(get_u_int16_t(packet->payload, temp + 3)) + 5;
      if (temp + temp2 > NDPI_MAX_SSL_REQUEST_SIZE) {
	return 1;
      }
      temp += temp2;
      NDPI_LOG(NDPI_PROTOCOL_SSL, ndpi_struct, NDPI_LOG_DEBUG, "temp = %u.\n", temp);
      if (packet->payload_packet_len == temp) {
	return 1;
      }
      if (packet->payload_packet_len >= temp + 5 &&
	  packet->payload[temp] == 0x16 && packet->payload[temp + 1] == 0x03) {
	temp2 = ntohs(get_u_int16_t(packet->payload, temp + 3)) + 5;
	if (temp + temp2 > NDPI_MAX_SSL_REQUEST_SIZE) {
	  return 1;
	}
	temp += temp2;
	NDPI_LOG(NDPI_PROTOCOL_SSL, ndpi_struct, NDPI_LOG_DEBUG, "temp = %u.\n", temp);
	if (packet->payload_packet_len == temp) {
	  return 1;
	}
	if (packet->payload_packet_len >= temp + 5 &&
	    packet->payload[temp] == 0x16 && packet->payload[temp + 1] == 0x03) {
	  temp2 = ntohs(get_u_int16_t(packet->payload, temp + 3)) + 5;
	  if (temp + temp2 > NDPI_MAX_SSL_REQUEST_SIZE) {
	    return 1;
	  }
	  temp += temp2;
	  NDPI_LOG(NDPI_PROTOCOL_SSL, ndpi_struct, NDPI_LOG_DEBUG, "temp = %u.\n", temp);
	  if (temp == packet->payload_packet_len) {
	    return 1;
	  }
	}

      }


    }

  }
  return 0;

}

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

  //      struct ndpi_id_struct         *src=flow->src;
  //      struct ndpi_id_struct         *dst=flow->dst;

  u_int8_t ret;

  if (packet->detected_protocol_stack[0] == NDPI_PROTOCOL_SSL) {
    if (flow->l4.tcp.ssl_stage == 3 && packet->payload_packet_len > 20 && flow->packet_counter < 5) {
      /* this should only happen, when we detected SSL with a packet that had parts of the certificate in subsequent packets
       * so go on checking for certificate patterns for a couple more packets
       */
      NDPI_LOG(NDPI_PROTOCOL_SSL, ndpi_struct, NDPI_LOG_DEBUG,
	       "ssl flow but check another packet for patterns\n");
      ssl_mark_and_payload_search_for_other_protocols(ndpi_struct, flow);
      if (packet->detected_protocol_stack[0] == NDPI_PROTOCOL_SSL) {
	/* still ssl so check another packet */
	return;
      } else {
	/* protocol has changed so we are done */
	return;
      }
    }
    return;
  }

  NDPI_LOG(NDPI_PROTOCOL_SSL, ndpi_struct, NDPI_LOG_DEBUG, "search ssl\n");

  {
    /* Check if this is whatsapp first (this proto runs over port 443) */
    if((packet->payload_packet_len > 5)
       && ((packet->payload[0] == 'W')
	   && (packet->payload[1] == 'A')
	   && (packet->payload[4] == 0)
	   && (packet->payload[2] <= 9)
	   && (packet->payload[3] <= 9))) {
      ndpi_int_add_connection(ndpi_struct, flow, NDPI_SERVICE_WHATSAPP, NDPI_REAL_PROTOCOL);
      return;
    } else {
      /* No whatsapp, let's try SSL */
      if(sslDetectProtocolFromCertificate(ndpi_struct, flow) > 0)
	return;
    }
  }

  if (packet->payload_packet_len > 40 && flow->l4.tcp.ssl_stage == 0) {
    NDPI_LOG(NDPI_PROTOCOL_SSL, ndpi_struct, NDPI_LOG_DEBUG, "first ssl packet\n");
    // SSLv2 Record
    if (packet->payload[2] == 0x01 && packet->payload[3] == 0x03
	&& (packet->payload[4] == 0x00 || packet->payload[4] == 0x01 || packet->payload[4] == 0x02)
	&& (packet->payload_packet_len - packet->payload[1] == 2)) {
      NDPI_LOG(NDPI_PROTOCOL_SSL, ndpi_struct, NDPI_LOG_DEBUG, "sslv2 len match\n");
      flow->l4.tcp.ssl_stage = 1 + packet->packet_direction;
      return;
    }

    if (packet->payload[0] == 0x16 && packet->payload[1] == 0x03
	&& (packet->payload[2] == 0x00 || packet->payload[2] == 0x01 || packet->payload[2] == 0x02)
	&& (packet->payload_packet_len - ntohs(get_u_int16_t(packet->payload, 3)) == 5)) {
      // SSLv3 Record
      NDPI_LOG(NDPI_PROTOCOL_SSL, ndpi_struct, NDPI_LOG_DEBUG, "sslv3 len match\n");
      flow->l4.tcp.ssl_stage = 1 + packet->packet_direction;
      return;
    }
  }

  if (packet->payload_packet_len > 40 &&
      flow->l4.tcp.ssl_stage == 1 + packet->packet_direction
      && flow->packet_direction_counter[packet->packet_direction] < 5) {
    return;
  }

  if (packet->payload_packet_len > 40 && flow->l4.tcp.ssl_stage == 2 - packet->packet_direction) {
    NDPI_LOG(NDPI_PROTOCOL_SSL, ndpi_struct, NDPI_LOG_DEBUG, "second ssl packet\n");
    // SSLv2 Record
    if (packet->payload[2] == 0x01 && packet->payload[3] == 0x03
	&& (packet->payload[4] == 0x00 || packet->payload[4] == 0x01 || packet->payload[4] == 0x02)
	&& (packet->payload_packet_len - 2) >= packet->payload[1]) {
      NDPI_LOG(NDPI_PROTOCOL_SSL, ndpi_struct, NDPI_LOG_DEBUG, "sslv2 server len match\n");
      ssl_mark_and_payload_search_for_other_protocols(ndpi_struct, flow);
      return;
    }

    ret = ndpi_search_sslv3_direction1(ndpi_struct, flow);
    if (ret == 1) {
      NDPI_LOG(NDPI_PROTOCOL_SSL, ndpi_struct, NDPI_LOG_DEBUG, "sslv3 server len match\n");
      ssl_mark_and_payload_search_for_other_protocols(ndpi_struct, flow);
      return;
    } else if (ret == 2) {
      NDPI_LOG(NDPI_PROTOCOL_SSL, ndpi_struct, NDPI_LOG_DEBUG,
	       "sslv3 server len match with split packet -> check some more packets for SSL patterns\n");
      ssl_mark_and_payload_search_for_other_protocols(ndpi_struct, flow);
      if (packet->detected_protocol_stack[0] == NDPI_PROTOCOL_SSL) {
	flow->l4.tcp.ssl_stage = 3;
      }
      return;
    }

    if (packet->payload_packet_len > 40 && flow->packet_direction_counter[packet->packet_direction] < 5) {
      NDPI_LOG(NDPI_PROTOCOL_SSL, ndpi_struct, NDPI_LOG_DEBUG, "need next packet\n");
      return;
    }
  }

  NDPI_LOG(NDPI_PROTOCOL_SSL, ndpi_struct, NDPI_LOG_DEBUG, "exclude ssl\n");
  NDPI_ADD_PROTOCOL_TO_BITMASK(flow->excluded_protocol_bitmask, NDPI_PROTOCOL_SSL);
  return;
}
#endif