Linux: SSH PermitEmptyPasswords

# Copyright (C) 2020 Greenbone Networks GmbH
#
# 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("1.3.6.1.4.1.25623.1.0.150073");
  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:"2020-01-14 14:14:36 +0100 (Tue, 14 Jan 2020)");
  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:"97");

  script_name("Linux: SSH PermitEmptyPasswords");

  script_category(ACT_GATHER_INFO);
  script_copyright("Copyright (C) 2020 Greenbone Networks GmbH");
  script_family("Policy");
  script_dependencies("compliance_tests.nasl", "read_sshd_config.nasl");
  script_mandatory_keys("Compliance/Launch");

  script_add_preference(name:"Value", type:"radio", value:"no;yes", id:1);

  script_xref(name:"URL", value:"https://linux.die.net/man/5/sshd_config");
  script_xref(name:"Policy", value:"CIS Distribution Independent Linux v2.0.0: 5.2.11 Ensure SSH PermitEmptyPasswords is disabled (Scored)");
  script_xref(name:"Policy", value:"CIS CentOS Linux 8 Benchmark v1.0.0: 5.2.11 Ensure SSH PermitEmptyPasswords is disabled (Scored)");
  script_xref(name:"Policy", value:"CIS Controls Version 7: 16.3 Require Multi-factor Authentication");

  script_tag(name:"summary", value:"The PermitEmptyPasswordsparameter specifies if the SSH server allows login
  to accounts with empty password strings. Disallowing remote shell access to accounts that have an
  empty password reduces the probability of unauthorized access to the system");

  exit(0);
}

include("ssh_func.inc");
include("policy_functions.inc");

cmd = "grep '^PermitEmptyPasswords' /etc/ssh/sshd_config";
title = "SSH PermitEmptyPasswords";
solution = "Edit the /etc/ssh/sshd_config file to set the parameter as follows:
PermitEmptyPasswords no";
test_type = "SSH_Cmd";
default = script_get_preference("Value", id:1);

if(get_kb_item("Policy/linux/sshd_config/ERROR")){
  value = "Error";
  compliant = "incomplete";
  comment = "Could not read /etc/ssh/sshd_config";
}else{
  value = get_kb_item("Policy/linux/sshd_config/permitemptypasswords");
  compliant = policy_setting_exact_match(value:value, set_point:default);
  comment = "";
}

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);