Linux: Lockout for failed authentication attempts

# Copyright (C) 2020 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("1.3.6.1.4.1.25623.1.0.150131");
  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: Lockout for failed authentication attempts");

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

  script_add_preference(name:"Value", type:"entry", value:"5", id:1);

  script_xref(name:"URL", value:"https://linux.die.net/man/8/pam_faillock");
  script_xref(name:"URL", value:"https://linux.die.net/man/8/pam_tally2");
  script_xref(name:"Policy", value:"CIS Distribution Independent Linux v2.0.0: 5.3.2 Ensure lockout for failed password attempts is configured (Not Scored)");
  script_xref(name:"Policy", value:"CIS CentOS Linux 8 Benchmark v1.0.0: 5.4.2 Ensure lockout for failed password attempts is configured (Scored)");
  script_xref(name:"Policy", value:"CIS Controls Version 7: 16.7 Establish Process for Revoking Access");

  script_tag(name:"summary", value:"The lockout for failed password attempts can be set in two
modules:

  - pam_tally2: The login counter (tallying) module

  - pam_faillock: Module counting authentication failures during a specified interval

Use the deny=n option to deny access if the number of consecutive authentication failures for this
user during the recent interval exceeds n.");

  exit(0);
}

include("policy_functions.inc");

cmd = "grep -E '^\s*auth\s+required\s+[pam_faillock.so|pam_tally2.so]\s+' /etc/pam.d/common-auth /etc/pam.d/password-auth /etc/pam.d/system-auth";
title = "Lockout for failed authentication attempts";
solution = "Set deny=n option in /etc/pam.d/common-auth, /etc/pam.d/password-auth or /etc/pam.d/system-auth";
test_type = "SSH_Cmd";
default = script_get_preference("Value", id:1);
value = "";

if(get_kb_item("Policy/linux/etc/pam.d/ERROR")){
  value = "Error";
  compliant = "incomplete";
  comment = "No SSH connection to host possible.";
}else{
  files = make_list("/etc/pam.d/common-auth", "/etc/pam.d/password-auth", "/etc/pam.d/system-auth");
  foreach file (files){
    if(get_kb_item("Policy/linux/" + file + "/content/ERROR"))
      continue;

    content = get_kb_item("Policy/linux/" + file + "/content");
    line = egrep(string:content, pattern:"auth\s+required\s+(pam_faillock.so|pam_tally2.so)");
    if(!line)
      continue;

    match = eregmatch(string:line, pattern:"deny=([0-9]*)");
    if(match){
      if(value == "")
        value = match[1];
      else if(match[1] < value)
        value = match[1];
    }
  }

  if(value == ""){
    compliant = "no";
    value = "None";
  }else{
    compliant = policy_setting_max_match(value:value, set_point:default);
  }
}

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);