New script

From: Vincent Renardias (vincentat_private)
Date: Wed Mar 12 2003 - 08:15:49 PST

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    Hello,

Here's a script that detects the 'discard' service (not currently done
by find_service.nes or find_service2.nasl).
Opinions ? Is the heuristic used acceptable ?
I've been running it on many different hosts without a single false
positive so far.

Cordialement,

-- 
Vincent Renardias <vincentat_private>


#
# This script was written by Vincent Renardias <vincentat_private>
#
# See the Nessus Scripts License for details
#

if(description)
{
 script_id(95000); # FIXME
 script_version ("$Revision$");
 script_cve_id("CAN-1999-0636");
 name["english"] = "Discard port open";
 name["francais"] = "Port 'discard' ouvert";
 script_name(english:name["english"], francais:name["francais"]);
 
 desc["english"] = "The 'discard' port is open. This port is
not of any use nowadays, and may be a source of problems, 

Risk factor : Low

Solution : comment out 'discard' in /etc/inetd.conf";

 desc["francais"] = "Le port 'discard' est ouvert. Ce port n'est plus
utile de nos jours, et peut s'averer être une source à 
problèmes.

Risk factor: Low.

Solution : Désactivez le service en mettant un diese (#)
devant la ligne 'discard' dans /etc/inetd.conf";

 script_description(english:desc["english"], francais:desc["francais"]);
 
 summary["english"] = "Checks if the 'discard' port is open";
 summary["francais"] = "Vérifie si le port 'discard' est ouvert";
 
 script_summary(english:summary["english"], francais:summary["francais"]);
 
 script_category(ACT_GATHER_INFO);
 
 script_copyright(english:"This script is Copyright (C) 2003 StrongHoldNet",
		francais:"Ce script est Copyright (C) 2003 StrongHoldNet",
		deutsch:"Dieses Skript ist Copyright geschützt. (C) 2003 StrongHoldNet");
		
 family["english"] = "Useless services";
 family["francais"] = "Services inutiles";
 family["deutsch"] = "Nutzlose Dienste";
 
 script_family(english:family["english"], francais:family["francais"], deutsch:family["deutsch"]);
 script_dependencie("find_service.nes");
 script_require_ports(9);
 
 exit(0);
}

#
# The script code starts here
#

include("misc_func.inc");

port = 9; # Discard is not supposed to run on any other port.
if(known_service(port)) { exit(0); }

# We send between 17 and 210 bytes of random data 5 times in a raw
# (waiting 3 seconds between each send).
# If the service is still listening without any output, we assume
# that 9/tcp is running 'discard'.
function check_discard(soc) {
  local_var i, n, res;
  if(!soc) {
   return(0);
  }
  for(i=0; i<4; i++) {
   sleep(3);
   n = send(socket:soc, data:string(crap(length:(rand()%193+17), data:string(rand())),"\r\n\r\n"));
   if (n<0) {
    return(0);
   }
   res = recv(socket:soc, length:1024, timeout:5);
   if(strlen(res) > 0) {
    return(0);
   }
  }
  return(1);
}

if(get_port_state(port))
{
 soc = open_sock_tcp(port);
 if(check_discard(soc)) {
   security_warning(port);
   register_service(port:port,proto:"discard");
   if(soc)
    close(soc);
 }
}

exit(0);

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