Chargen Service Detection (TCP)

# SPDX-FileCopyrightText: 2020 Greenbone AG
# Some text descriptions might be excerpted from (a) referenced
# source(s), and are Copyright (C) by the respective right holder(s).
#
# SPDX-License-Identifier: GPL-2.0-only

if(description)
{
  script_oid("1.3.6.1.4.1.25623.1.0.108893");
  script_version("2023-09-12T05:05:19+0000");
  script_cve_id("CVE-1999-0639");
  script_tag(name:"last_modification", value:"2023-09-12 05:05:19 +0000 (Tue, 12 Sep 2023)");
  script_tag(name:"creation_date", value:"2020-08-27 13:32:10 +0000 (Thu, 27 Aug 2020)");
  script_tag(name:"cvss_base_vector", value:"AV:N/AC:L/Au:N/C:N/I:N/A:N");
  script_tag(name:"cvss_base", value:"0.0");
  script_name("Chargen Service Detection (TCP)");
  script_category(ACT_GATHER_INFO);
  script_family("Service detection");
  script_copyright("Copyright (C) 2020 Greenbone AG");
  script_dependencies("find_service1.nasl", "find_service2.nasl");
  script_require_ports("Services/chargen", 19);

  script_tag(name:"summary", value:"TCP based detection of a 'chargen' service.");

  script_tag(name:"insight", value:"chargen service is an unsecured and obsolete protocol and it
  should be disabled. Historically it has been used to perform denial of service attacks. Ping and
  traceroute can be used to provide the same functionality.");

  script_tag(name:"qod_type", value:"remote_banner");

  exit(0);
}

include("host_details.inc");
include("port_service_func.inc");

port = service_get_port( default:19, proto:"chargen" );

# nb: From find_service1.nasl and find_service2.nasl
banner = get_kb_item( "chargen/tcp/" + port + "/banner" );
if( ! banner ) {
  soc = open_sock_tcp( port );
  if( ! soc )
    exit( 0 );

  banner = recv_line( socket:soc, length:1024 );
  close( soc );
}

if( ! banner )
  exit( 0 );

# nb: See also find_service1.nasl and find_service2.nasl
chargen_found = 0;
foreach chargen_pattern( make_list( '!"#$%&\'()*+,-./', "ABCDEFGHIJ", "abcdefg", "0123456789", ":;<=>?@", "KLMNOPQRSTUVWXYZ" ) ) {
  if( chargen_pattern >< banner )
    chargen_found++;
}

if( chargen_found > 2 ) {
  replace_kb_item( name:"chargen/tcp/" + port + "/banner", value:chomp( banner ) );
  set_kb_item( name:"chargen/tcp/detected", value:TRUE );
  set_kb_item( name:"chargen/tcp/" + port + "/detected", value:TRUE );
  service_register( port:port, proto:"chargen", message:"A chargen service seems to be running on this port." );
  log_message( port:port, data:"A chargen service seems to be running on this port." );
}

exit( 0 );