Debian DLA-3187-1 : dropbear - LTS security update

#%NASL_MIN_LEVEL 80900
#
# (C) Tenable, Inc.
#
# The descriptive text and package checks in this plugin were
# extracted from Debian Security Advisory dla-3187. The text
# itself is copyright (C) Software in the Public Interest, Inc.
#

include('compat.inc');

if (description)
{
  script_id(167353);
  script_version("1.3");
  script_set_attribute(attribute:"plugin_modification_date", value:"2022/11/24");

  script_cve_id("CVE-2021-36369");

  script_name(english:"Debian DLA-3187-1 : dropbear - LTS security update");

  script_set_attribute(attribute:"synopsis", value:
"The remote Debian host is missing a security-related update.");
  script_set_attribute(attribute:"description", value:
"The remote Debian 10 host has packages installed that are affected by a vulnerability as referenced in the dla-3187
advisory.

  - An issue was discovered in Dropbear through 2020.81. Due to a non-RFC-compliant check of the available
    authentication methods in the client-side SSH code, it is possible for an SSH server to change the login
    process in its favor. This attack can bypass additional security measures such as FIDO2 tokens or SSH-
    Askpass. Thus, it allows an attacker to abuse a forwarded agent for logging on to another server
    unnoticed. (CVE-2021-36369)

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version
number.");
  script_set_attribute(attribute:"see_also", value:"https://security-tracker.debian.org/tracker/source-package/dropbear");
  script_set_attribute(attribute:"see_also", value:"https://www.debian.org/lts/security/2022/dla-3187");
  script_set_attribute(attribute:"see_also", value:"https://security-tracker.debian.org/tracker/CVE-2021-36369");
  script_set_attribute(attribute:"see_also", value:"https://packages.debian.org/source/buster/dropbear");
  script_set_attribute(attribute:"solution", value:
"Upgrade the dropbear packages.

For Debian 10 buster, this problem has been fixed in version 2018.76-5+deb10u2.");
  script_set_cvss_base_vector("CVSS2#AV:N/AC:L/Au:N/C:N/I:C/A:N");
  script_set_cvss_temporal_vector("CVSS2#E:U/RL:OF/RC:C");
  script_set_cvss3_base_vector("CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N");
  script_set_cvss3_temporal_vector("CVSS:3.0/E:U/RL:O/RC:C");
  script_set_attribute(attribute:"cvss_score_source", value:"CVE-2021-36369");

  script_set_attribute(attribute:"exploitability_ease", value:"No known exploits are available");
  script_set_attribute(attribute:"exploit_available", value:"false");

  script_set_attribute(attribute:"vuln_publication_date", value:"2022/10/12");
  script_set_attribute(attribute:"patch_publication_date", value:"2022/11/14");
  script_set_attribute(attribute:"plugin_publication_date", value:"2022/11/14");

  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:debian:debian_linux:dropbear");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:debian:debian_linux:dropbear-bin");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:debian:debian_linux:dropbear-initramfs");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:debian:debian_linux:dropbear-run");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:debian:debian_linux:10.0");
  script_end_attributes();

  script_category(ACT_GATHER_INFO);
  script_family(english:"Debian Local Security Checks");

  script_copyright(english:"This script is Copyright (C) 2022 and is owned by Tenable, Inc. or an Affiliate thereof.");

  script_dependencies("ssh_get_info.nasl");
  script_require_keys("Host/local_checks_enabled", "Host/Debian/release", "Host/Debian/dpkg-l");

  exit(0);
}

include('debian_package.inc');

if (!get_kb_item("Host/local_checks_enabled")) audit(AUDIT_LOCAL_CHECKS_NOT_ENABLED);
if (!get_kb_item("Host/Debian/dpkg-l")) audit(AUDIT_PACKAGE_LIST_MISSING);

var debian_release = get_kb_item('Host/Debian/release');
if ( isnull(debian_release) ) audit(AUDIT_OS_NOT, 'Debian');
debian_release = chomp(debian_release);
if (! preg(pattern:"^(10)\.[0-9]+", string:debian_release)) audit(AUDIT_OS_NOT, 'Debian 10.0', 'Debian ' + debian_release);
var cpu = get_kb_item('Host/cpu');
if (isnull(cpu)) audit(AUDIT_UNKNOWN_ARCH);
if ('x86_64' >!< cpu && cpu !~ "^i[3-6]86$" && 'aarch64' >!< cpu) audit(AUDIT_LOCAL_CHECKS_NOT_IMPLEMENTED, 'Debian', cpu);

var pkgs = [
    {'release': '10.0', 'prefix': 'dropbear', 'reference': '2018.76-5+deb10u2'},
    {'release': '10.0', 'prefix': 'dropbear-bin', 'reference': '2018.76-5+deb10u2'},
    {'release': '10.0', 'prefix': 'dropbear-initramfs', 'reference': '2018.76-5+deb10u2'},
    {'release': '10.0', 'prefix': 'dropbear-run', 'reference': '2018.76-5+deb10u2'}
];

var flag = 0;
foreach package_array ( pkgs ) {
  var _release = NULL;
  var prefix = NULL;
  var reference = NULL;
  if (!empty_or_null(package_array['release'])) _release = package_array['release'];
  if (!empty_or_null(package_array['prefix'])) prefix = package_array['prefix'];
  if (!empty_or_null(package_array['reference'])) reference = package_array['reference'];
  if (_release && prefix && reference) {
    if (deb_check(release:_release, prefix:prefix, reference:reference)) flag++;
  }
}

if (flag)
{
  security_report_v4(
    port       : 0,
    severity   : SECURITY_HOLE,
    extra      : deb_report_get()
  );
  exit(0);
}
else
{
  var tested = deb_pkg_tests_get();
  if (tested) audit(AUDIT_PACKAGE_NOT_AFFECTED, tested);
  else audit(AUDIT_PACKAGE_NOT_INSTALLED, 'dropbear / dropbear-bin / dropbear-initramfs / dropbear-run');
}