Ubuntu 16.10 / 17.04 : lightdm vulnerability (USN-3285-1)

#
# (C) Tenable Network Security, Inc.
#
# The descriptive text and package checks in this plugin were
# extracted from Ubuntu Security Notice USN-3285-1. The text 
# itself is copyright (C) Canonical, Inc. See 
# <http://www.ubuntu.com/usn/>. Ubuntu(R) is a registered 
# trademark of Canonical, Inc.
#

include("compat.inc");

if (description)
{
  script_id(100156);
  script_version("3.10");
  script_set_attribute(attribute:"plugin_modification_date", value:"2023/01/12");

  script_cve_id("CVE-2017-8900");
  script_xref(name:"USN", value:"3285-1");

  script_name(english:"Ubuntu 16.10 / 17.04 : lightdm vulnerability (USN-3285-1)");
  script_summary(english:"Checks dpkg output for updated package.");

  script_set_attribute(
    attribute:"synopsis",
    value:"The remote Ubuntu host is missing a security-related patch."
  );
  script_set_attribute(
    attribute:"description",
    value:
"Tyler Hicks discovered that LightDM did not confine the user session
for guest users. An attacker with physical access could use this issue
to access files and other resources that they should not be able to
access. In the default installation, this includes files in the home
directories of other users on the system. This update fixes the issue
by disabling the guest session. It may be re-enabled in a future
update. Please see the bug referenced below for instructions on how to
manually re-enable the guest session.

Note that Tenable Network Security has extracted the preceding
description block directly from the Ubuntu security advisory. Tenable
has attempted to automatically clean and format it as much as possible
without introducing additional issues."
  );
  script_set_attribute(
    attribute:"see_also",
    value:"https://usn.ubuntu.com/3285-1/"
  );
  script_set_attribute(
    attribute:"solution",
    value:"Update the affected lightdm package."
  );
  script_set_cvss_base_vector("CVSS2#AV:L/AC:L/Au:N/C:P/I:N/A:N");
  script_set_cvss_temporal_vector("CVSS2#E:U/RL:OF/RC:C");
  script_set_cvss3_base_vector("CVSS:3.0/AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N");
  script_set_cvss3_temporal_vector("CVSS:3.0/E:U/RL:O/RC:C");
  script_set_attribute(attribute:"exploitability_ease", value:"No known exploits are available");
  script_set_attribute(attribute:"exploit_available", value:"false");

  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:lightdm");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:canonical:ubuntu_linux:16.10");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:canonical:ubuntu_linux:17.04");

  script_set_attribute(attribute:"vuln_publication_date", value:"2017/05/12");
  script_set_attribute(attribute:"patch_publication_date", value:"2017/05/11");
  script_set_attribute(attribute:"plugin_publication_date", value:"2017/05/12");
  script_set_attribute(attribute:"generated_plugin", value:"current");
  script_end_attributes();

  script_category(ACT_GATHER_INFO);
  script_copyright(english:"Ubuntu Security Notice (C) 2017-2023 Canonical, Inc. / NASL script (C) 2017-2023 and is owned by Tenable, Inc. or an Affiliate thereof.");
  script_family(english:"Ubuntu Local Security Checks");

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

  exit(0);
}


include("audit.inc");
include("ubuntu.inc");
include("misc_func.inc");

if ( ! get_kb_item("Host/local_checks_enabled") ) audit(AUDIT_LOCAL_CHECKS_NOT_ENABLED);
release = get_kb_item("Host/Ubuntu/release");
if ( isnull(release) ) audit(AUDIT_OS_NOT, "Ubuntu");
var release = chomp(release);
if (! preg(pattern:"^(16\.10|17\.04)$", string:release)) audit(AUDIT_OS_NOT, "Ubuntu 16.10 / 17.04", "Ubuntu " + release);
if ( ! get_kb_item("Host/Debian/dpkg-l") ) audit(AUDIT_PACKAGE_LIST_MISSING);

var cpu = get_kb_item("Host/cpu");
if (isnull(cpu)) audit(AUDIT_UNKNOWN_ARCH);
if ('x86_64' >!< cpu && cpu !~ "^i[3-6]86$" && 's390' >!< cpu && 'aarch64' >!< cpu) audit(AUDIT_LOCAL_CHECKS_NOT_IMPLEMENTED, 'Ubuntu', cpu);

var flag = 0;

if (ubuntu_check(osver:"16.10", pkgname:"lightdm", pkgver:"1.19.5-0ubuntu1.2")) flag++;
if (ubuntu_check(osver:"17.04", pkgname:"lightdm", pkgver:"1.22.0-0ubuntu2.1")) flag++;

if (flag)
{
  security_report_v4(
    port       : 0,
    severity   : SECURITY_NOTE,
    extra      : ubuntu_report_get()
  );
  exit(0);
}
else
{
  var tested = ubuntu_pkg_tests_get();
  if (tested) audit(AUDIT_PACKAGE_NOT_AFFECTED, tested);
  else audit(AUDIT_PACKAGE_NOT_INSTALLED, "lightdm");
}