Linux: SSH PubkeyAuthentication

# 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("1.3.6.1.4.1.25623.1.0.150222");
  script_version("2026-06-23T06:54:08+0000");
  script_tag(name:"last_modification", value:"2026-06-23 06:54:08 +0000 (Tue, 23 Jun 2026)");
  script_tag(name:"creation_date", value:"2020-05-06 14:53:53 +0000 (Wed, 06 May 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 PubkeyAuthentication");

  script_category(ACT_GATHER_INFO);
  script_copyright("Copyright (C) 2020 Greenbone AG");
  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:"yes;no", id:1);

  script_xref(name:"URL", value:"https://linux.die.net/man/5/sshd_config");
  script_xref(name:"URL",value:"https://www.bsi.bund.de/EN/Themen/Unternehmen-und-Organisationen/Standards-und-Zertifizierung/Technische-Richtlinien/TR-nach-Thema-sortiert/tr02102/tr02102_node.html");
  script_xref(name:"Policy", value:"BSI TR-02102-4: 3.7 Client Authentication");

  script_tag(name:"summary", value:"sshd reads configuration data from /etc/ssh/sshd_config (or the
  file specified with -f on the command line). The file contains keyword-argument pairs, one per
  line. Lines starting with '#' and empty lines are interpreted as comments. Arguments may
  optionally be enclosed in double quotes in order to represent arguments containing spaces.

  - PubkeyAuthentication: Specifies whether public key authentication is allowed. The default is
  'yes'. This option applies to protocol version 2 only.");

  exit(0);
}

include("policy_functions.inc");

cmd = "grep '^PubkeyAuthentication' /etc/ssh/sshd_config";
title = "SSH PubkeyAuthentication";
solution = "Edit /etc/ssh/sshd_config";
test_type = "SSH_Cmd";
default = script_get_preference("Value", id:1);

if(get_kb_item("linux/mount/ERROR")){
  value = "Error";
  compliant = "incomplete";
  comment = "Could not read /etc/ssh/sshd_config";
}else{
  value = get_kb_item("Policy/linux/sshd_config/pubkeyauthentication");
  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);