Linux: SSH Protocol

# 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("1.3.6.1.4.1.25623.1.0.150066");
  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:"2020-01-14 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 Protocol");

  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:"entry", value:"2", 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: 3.2 SSH Versions");
  script_xref(name:"Policy", value:"CIS Distribution Independent Linux v2.0.0: 5.2.4 Ensure SSH Protocol is set to 2 (Scored)");
  script_xref(name:"Policy", value:"CIS Controls Version 7: 4.5 Use Multifactor Authentication For All Administrative Access");
  script_xref(name:"Policy", value:"CIS Controls Version 7: 14.4 Encrypt All Sensitive Information in Transit");

  script_tag(name:"summary", value:"Older versions of SSH support two different and incompatible
  protocols: SSH1 and SSH2. SSH1 was the original protocol and was subject to security issues.
  SSH2 is more advanced and secure.

  SSH v1 suffers from insecurities that do not affect SSH v2.");

  exit(0);
}

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

cmd = "grep '^Protocol' /etc/ssh/sshd_config";
title = "SSH Protocol";
solution = "Edit /etc/ssh/sshd_config";
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/protocol");
  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);