Configure the Banner Path Correctly

# SPDX-FileCopyrightText: 2025 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

# ------------------------------------------------------------------
# METADATA
# ------------------------------------------------------------------

if(description)
{
  script_oid("1.3.6.1.4.1.25623.1.0.130393");
  script_version("2025-11-21T05:40:28+0000");
  script_tag(name:"last_modification", value:"2025-11-21 05:40:28 +0000 (Fri, 21 Nov 2025)");
  script_tag(name:"creation_date", value:"2025-05-07 11:45:55 +0000 (Wed, 07 May 2025)");
  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("Configure the Banner Path Correctly");

  script_category(ACT_GATHER_INFO);
  script_copyright("Copyright (C) 2025 Greenbone AG");
  script_family("Policy");
  script_dependencies("compliance_tests.nasl", "compliance_os_check.nasl");

  script_mandatory_keys("Compliance/Launch", "policy/ssh/login/euleros_eulerosvirtual_openeuler_hce");

  script_xref(name:"Policy", value:"EulerOS Baseline: openEuler Security Configuration Baseline (v1.0.0): 2. Secure Access: 2.3 Identity Authentication: 2.3.4 Configure the Banner Path Correctly (Requirement)");
  script_xref(name:"Policy", value:"EulerOS Virtual: openEuler Security Configuration Baseline (v1.0.0): 2. Secure Access: 2.3 Identity Authentication: 2.3.4 Configure the Banner Path Correctly (Requirement)");
  script_xref(name:"Policy", value:"HCE Linux (Huawei Cloud EulerOS): openEuler Security Configuration Baseline (v1.0.0): 2. Secure Access: 2.3 Identity Authentication: 2.3.4 Configure the Banner Path Correctly (Requirement)");
  script_xref(name:"Policy", value:"openEuler Baseline: openEuler Security Configuration Baseline (v1.0.0): 2. Secure Access: 2.3 Identity Authentication: 2.3.4 Configure the Banner Path Correctly (Requirement)");

  script_tag(name:"summary", value:"The banner path points to a file which contains the prompt
information displayed on the client before a user logs in to the SSH. The content in the file can
be configured based on the actual service scenario.

If the banner path is not set, no information is displayed by default.");

  exit(0);
}

include("ssh_func.inc");
include("host_details.inc");
include("policy_reporting_module.inc");

title = "Configure the Banner Path Correctly";

solution = "1. Open the /etc/ssh/sshd_config file, configure the file to which the Banner field
points, and restart the sshd service.

# vim /etc/ssh/sshd_config
Banner /etc/issue.net
# systemctl restart sshd

2. Modify the content in the file to which the Banner field points.

# vim /etc/issue.net
Authorized users only. All activities may be monitored and reported.";

check_type = "SSH_Cmd";

action = 'Run the command in the terminal:
# grep -P "^Banner\\b\\s+/[^\\s]+" /etc/ssh/sshd_config';

expected_value = 'The output should not be empty';

# ------------------------------------------------------------------
# CONNECTION CHECK
# ------------------------------------------------------------------

if(!get_kb_item("login/SSH/success") || !sock = ssh_login_or_reuse_connection()){

  report_ssh_error(title: title,
                   solution: solution,
                   action: action,
                   expected_value: expected_value,
                   check_type: check_type);
  exit(0);
}

# ------------------------------------------------------------------
# CHECK : Check banner in ssh config
# ------------------------------------------------------------------

step_cmd = 'grep -P "^Banner\\b\\s+/[^\\s]+" /etc/ssh/sshd_config';
actual_value = ssh_cmd(socket:sock, cmd:step_cmd, return_errors:TRUE, return_linux_errors_only:TRUE);

if(eregmatch(string: actual_value, pattern:"(No such file or directory|Permission denied|Command not found|Segmentation fault|service not found|is not running|syntax error near unexpected token|syntax error: unexpected end of file)", icase: TRUE)){
  compliant = "incomplete";
  comment = "Something went wrong during the audit check. Please try again.";
}else if(actual_value){
  compliant = "yes";
  comment = "Check passed";
}else{
  compliant = "no";
  comment = "Check failed";
}

# ------------------------------------------------------------------
# REPORT
# ------------------------------------------------------------------

target = get_kb_item("policy/ssh/login/os-release");
comment = "Target: " + target + "\n" + comment;

report_audit(action: action,
             actual_value: actual_value,
             expected_value: expected_value,
             is_compliant: compliant,
             solution: solution,
             check_type: check_type,
             title: title,
             comment: comment);

exit(0);