OpenSSH Denial of Service And User Enumeration Vulnerabilities - Linux

# SPDX-FileCopyrightText: 2016 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

CPE = "cpe:/a:openbsd:openssh";

if(description)
{
  script_oid("1.3.6.1.4.1.25623.1.0.809154");
  script_version("2024-02-15T05:05:40+0000");
  script_cve_id("CVE-2016-6515", "CVE-2016-6210");
  script_tag(name:"cvss_base", value:"7.8");
  script_tag(name:"cvss_base_vector", value:"AV:N/AC:L/Au:N/C:N/I:N/A:C");
  script_tag(name:"last_modification", value:"2024-02-15 05:05:40 +0000 (Thu, 15 Feb 2024)");
  script_tag(name:"severity_vector", value:"CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H");
  script_tag(name:"severity_origin", value:"NVD");
  script_tag(name:"severity_date", value:"2018-09-11 10:29:00 +0000 (Tue, 11 Sep 2018)");
  script_tag(name:"creation_date", value:"2016-08-25 18:35:09 +0530 (Thu, 25 Aug 2016)");
  script_name("OpenSSH Denial of Service And User Enumeration Vulnerabilities - Linux");
  script_copyright("Copyright (C) 2016 Greenbone AG");
  script_category(ACT_GATHER_INFO);
  script_family("Denial of Service");
  script_dependencies("gb_openssh_consolidation.nasl", "os_detection.nasl");
  script_mandatory_keys("openssh/detected", "Host/runs_unixoide");

  script_xref(name:"URL", value:"http://www.openssh.com/txt/release-7.3");
  script_xref(name:"URL", value:"http://www.securityfocus.com/bid/92212");
  script_xref(name:"URL", value:"http://seclists.org/fulldisclosure/2016/Jul/51");
  script_xref(name:"URL", value:"https://security-tracker.debian.org/tracker/CVE-2016-6210");
  script_xref(name:"URL", value:"http://openwall.com/lists/oss-security/2016/08/01/2");

  script_tag(name:"summary", value:"openssh is prone to denial of service and user enumeration vulnerabilities.");

  script_tag(name:"vuldetect", value:"Checks if a vulnerable version is present on the target host.");

  script_tag(name:"insight", value:"Multiple flaws exist due to:

  - The auth_password function in 'auth-passwd.c' script does not limit password
    lengths for password authentication.

  - The sshd in OpenSSH, when SHA256 or SHA512 are used for user password hashing
    uses BLOWFISH hashing on a static password when the username does not exist
    and it takes much longer to calculate SHA256/SHA512 hash than BLOWFISH hash.");

  script_tag(name:"impact", value:"Successfully exploiting this issue allows
  remote attackers to cause a denial of service (crypt CPU consumption) and
  to enumerate users by leveraging the timing difference between responses
  when a large password is provided.");

  script_tag(name:"affected", value:"OpenSSH versions before 7.3 on Linux");

  script_tag(name:"solution", value:"Upgrade to OpenSSH version 7.3 or later.");

  script_tag(name:"solution_type", value:"VendorFix");
  script_tag(name:"qod_type", value:"remote_banner_unreliable");

  exit(0);
}

include("version_func.inc");
include("host_details.inc");

if(isnull(port = get_app_port(cpe:CPE)))
  exit(0);

if(!infos = get_app_version_and_location(cpe:CPE, port:port, exit_no_version:TRUE))
  exit(0);

vers = infos["version"];
path = infos["location"];

if(version_is_less(version:vers, test_version:"7.3")) {
  report = report_fixed_ver(installed_version:vers, fixed_version:"7.3", install_path:path);
  security_message(port:port, data:report);
  exit(0);
}

exit(99);