FreeBSD : openssh -- command injection when X11Forwarding is enabled (e4644df8-e7da-11e5-829d-c80aa9043978)

2016-03-14T00:00:00
ID FREEBSD_PKG_E4644DF8E7DA11E5829DC80AA9043978.NASL
Type nessus
Reporter Tenable
Modified 2016-10-19T00:00:00

Description

The OpenSSH project reports :

Missing sanitisation of untrusted input allows an authenticated user who is able to request X11 forwarding to inject commands to xauth(1).

Injection of xauth commands grants the ability to read arbitrary files under the authenticated user's privilege, Other xauth commands allow limited information leakage, file overwrite, port probing and generally expose xauth(1), which was not written with a hostile user in mind, as an attack surface.

Mitigation :

Set X11Forwarding=no in sshd_config. This is the default.

For authorized_keys that specify a 'command' restriction, also set the 'restrict' (available in OpenSSH >=7.2) or 'no-x11-forwarding' restrictions.

                                        
                                            #
# (C) Tenable Network Security, Inc.
#
# The descriptive text and package checks in this plugin were  
# extracted from the FreeBSD VuXML database :
#
# Copyright 2003-2016 Jacques Vidrine and contributors
#
# Redistribution and use in source (VuXML) and 'compiled' forms (SGML,
# HTML, PDF, PostScript, RTF and so forth) with or without modification,
# are permitted provided that the following conditions are met:
# 1. Redistributions of source code (VuXML) must retain the above
#    copyright notice, this list of conditions and the following
#    disclaimer as the first lines of this file unmodified.
# 2. Redistributions in compiled form (transformed to other DTDs,
#    published online in any format, converted to PDF, PostScript,
#    RTF and other formats) must reproduce the above copyright
#    notice, this list of conditions and the following disclaimer
#    in the documentation and/or other materials provided with the
#    distribution.
# 
# THIS DOCUMENTATION IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS "AS IS"
# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
# THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
# PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS
# BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
# OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
# OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
# BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
# WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
# OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS DOCUMENTATION,
# EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#

include("compat.inc");

if (description)
{
  script_id(89897);
  script_version("$Revision: 2.5 $");
  script_cvs_date("$Date: 2016/10/19 14:14:42 $");

  script_cve_id("CVE-2016-3115");
  script_xref(name:"FreeBSD", value:"SA-16:14.openssh");

  script_name(english:"FreeBSD : openssh -- command injection when X11Forwarding is enabled (e4644df8-e7da-11e5-829d-c80aa9043978)");
  script_summary(english:"Checks for updated package in pkg_info output");

  script_set_attribute(
    attribute:"synopsis", 
    value:"The remote FreeBSD host is missing a security-related update."
  );
  script_set_attribute(
    attribute:"description", 
    value:
"The OpenSSH project reports :

Missing sanitisation of untrusted input allows an authenticated user
who is able to request X11 forwarding to inject commands to xauth(1).

Injection of xauth commands grants the ability to read arbitrary files
under the authenticated user's privilege, Other xauth commands allow
limited information leakage, file overwrite, port probing and
generally expose xauth(1), which was not written with a hostile user
in mind, as an attack surface.

Mitigation :

Set X11Forwarding=no in sshd_config. This is the default.

For authorized_keys that specify a 'command' restriction, also set the
'restrict' (available in OpenSSH >=7.2) or 'no-x11-forwarding'
restrictions."
  );
  script_set_attribute(
    attribute:"see_also",
    value:"http://www.openssh.com/txt/x11fwd.adv"
  );
  # http://www.freebsd.org/ports/portaudit/e4644df8-e7da-11e5-829d-c80aa9043978.html
  script_set_attribute(
    attribute:"see_also",
    value:"http://www.nessus.org/u?9d9c23ca"
  );
  script_set_attribute(attribute:"solution", value:"Update the affected package.");
  script_set_cvss_base_vector("CVSS2#AV:N/AC:L/Au:S/C:P/I:P/A:N");
  script_set_cvss3_base_vector("CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N");

  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:freebsd:freebsd:openssh-portable");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:freebsd:freebsd");

  script_set_attribute(attribute:"vuln_publication_date", value:"2016/03/11");
  script_set_attribute(attribute:"patch_publication_date", value:"2016/03/11");
  script_set_attribute(attribute:"plugin_publication_date", value:"2016/03/14");
  script_end_attributes();

  script_category(ACT_GATHER_INFO);
  script_copyright(english:"This script is Copyright (C) 2016 Tenable Network Security, Inc.");
  script_family(english:"FreeBSD Local Security Checks");

  script_dependencies("ssh_get_info.nasl");
  script_require_keys("Host/local_checks_enabled", "Host/FreeBSD/release", "Host/FreeBSD/pkg_info");

  exit(0);
}


include("audit.inc");
include("freebsd_package.inc");


if (!get_kb_item("Host/local_checks_enabled")) audit(AUDIT_LOCAL_CHECKS_NOT_ENABLED);
if (!get_kb_item("Host/FreeBSD/release")) audit(AUDIT_OS_NOT, "FreeBSD");
if (!get_kb_item("Host/FreeBSD/pkg_info")) audit(AUDIT_PACKAGE_LIST_MISSING);


flag = 0;

if (pkg_test(save_report:TRUE, pkg:"openssh-portable<7.2.p2,1")) flag++;

if (flag)
{
  if (report_verbosity > 0) security_warning(port:0, extra:pkg_report_get());
  else security_warning(0);
  exit(0);
}
else audit(AUDIT_HOST_NOT, "affected");