Linux: Disabled telnet server

# Copyright (C) 2021 Greenbone Networks GmbH
# 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-or-later
#
# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU General Public License
# as published by the Free Software Foundation; either version 2
# of the License, or (at your option) any later version.
#
# This program 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 General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

if(description)
{
  script_oid("1.3.6.1.4.1.25623.1.0.150514");
  script_version("2022-08-31T10:10:28+0000");
  script_tag(name:"last_modification", value:"2022-08-31 10:10:28 +0000 (Wed, 31 Aug 2022)");
  script_tag(name:"creation_date", value:"2021-01-04 10:57:26 +0000 (Mon, 04 Jan 2021)");
  script_tag(name:"cvss_base", value:"0.0");
  script_tag(name:"cvss_base_vector", value:"AV:L/AC:H/Au:S/C:N/I:N/A:N");
  script_tag(name:"qod", value:"70");

  script_name("Linux: Disabled telnet server");

  script_category(ACT_GATHER_INFO);
  script_copyright("Copyright (C) 2021 Greenbone Networks GmbH");
  script_family("Policy");

  script_dependencies("compliance_tests.nasl", "read_etc_inetd_xinetd_files.nasl");

  script_mandatory_keys("Compliance/Launch");

  script_xref(name:"Policy", value:"CIS Distribution Independent Linux v2.0.0: 2.1.8 Ensure telnet server is not enabled (Scored)");
  script_xref(name:"Policy", value:"CIS Controls Version 7: 9.2 Ensure Only Approved Ports Protocols and Services Are Running");
  script_xref(name:"Policy", value:"CIS Controls Version 7: 4.5 Use Multifactor Authentication For All Administrative Access");

  script_tag(name:"summary", value:"The telnet-server package contains the telnet daemon, which
accepts connections from users from other systems via the telnet protocol.");

  exit(0);
}

include( "policy_functions.inc" );

cmd = "grep -R '^telnet' /etc/inetd.*; grep 'disabled = yes' /etc/xinetd.d/telnet";
title = "Disabled telnet services";
solution = "Comment out or remove any lines starting with telnet from /etc/inetd.conf and /etc/inetd.d/* .
Set disable = yes on all telnet services in /etc/xinetd.conf and /etc/xinetd.d/*.";
test_type = "SSH_Cmd";
default = "Disabled";

if( get_kb_item ( "Policy/linux/inetd/ssh/ERROR" ) || get_kb_item ( "Policy/linux/xinetd/ssh/ERROR" ) ) {
  value = "Error";
  compliant = "incomplete";
  comment = "Can not login to the host";
} else if( get_kb_item( "Policy/linux/inetd/ERROR" ) && get_kb_item( "Policy/linux/xinetd/ERROR" ) ){
  compliant = "yes";
  value = "Disabled";
  comment = "No /etc/inetd.* and /etc/xinetd* files found";
} else {
  # nb: Try /etc/inetd.* files first
  files = get_kb_list( "Policy/linux//etc/inetd*" );
  foreach key( keys( files ) ) {
    if( egrep( string:files[key], pattern:"^\s*telnet" ) ) {
      compliant = "no";
      value = "Enabled";
      comment = "Found in /etc/inetd.* file";
      break;
    }
  }

  if( ! value ) {
    if( file = get_kb_item( "Policy/linux//etc/xinetd.d/telnet/content" ) ) {
      if( file !~ "disable\s*=\s*yes" ) {
        compliant = "no";
        value = "Enabled";
        comment = "Found in /etc/xinetd.d/telnet file";
      }
    }
  }

  # nb: Try /etc/xinetd.conf
  if( ! value ) {
    if( telnet_service = get_kb_item( "Policy/linux/etc/xinetd.conf/telnet" ) ) {
      if( telnet_service !~ "disable\s*=\s*yes" ) {
        compliant = "no";
        value = "Enabled";
        comment = "Found in /etc/xinetd.conf file";
      }
    }
  }

  if( ! value ) {
    compliant = "yes";
    value = "Disabled";
  }
}

policy_reporting( result:value, default:default, compliant:compliant, fixtext:solution,
  type:test_type, test:cmd, info:comment );

policy_set_kbs( type:test_type, cmd:cmd, default:default, solution:solution, title:title,
  value:value, compliant:compliant );

exit( 0 );