FreeBSD : xen-kernel -- x86: Mishandling of instruction pointer truncation during emulation (49211361-ba4d-11e6-ae1b-002590263bf5)

2016-12-05T00:00:00
ID FREEBSD_PKG_49211361BA4D11E6AE1B002590263BF5.NASL
Type nessus
Reporter Tenable
Modified 2016-12-05T00:00:00

Description

The Xen Project reports :

When emulating HVM instructions, Xen uses a small i-cache for fetches from guest memory. The code that handles cache misses does not check if the address from which it fetched lies within the cache before blindly writing to it. As such it is possible for the guest to overwrite hypervisor memory.

It is currently believed that the only way to trigger this bug is to use the way that Xen currently incorrectly wraps CS:IP in 16 bit modes. The included patch prevents such wrapping.

A malicious HVM guest administrator can escalate their privilege to that of the host.

                                        
                                            #
# (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.
#

if (NASL_LEVEL < 3000) exit(0);

include("compat.inc");

if (description)
{
  script_id(95501);
  script_version("$Revision: 3.1 $");
  script_cvs_date("$Date: 2016/12/05 14:32:01 $");

  script_cve_id("CVE-2016-7093");

  script_name(english:"FreeBSD : xen-kernel -- x86: Mishandling of instruction pointer truncation during emulation (49211361-ba4d-11e6-ae1b-002590263bf5)");
  script_summary(english:"Checks for updated packages in pkg_info output");

  script_set_attribute(
    attribute:"synopsis", 
    value:
"The remote FreeBSD host is missing one or more security-related
updates."
  );
  script_set_attribute(
    attribute:"description", 
    value:
"The Xen Project reports :

When emulating HVM instructions, Xen uses a small i-cache for fetches
from guest memory. The code that handles cache misses does not check
if the address from which it fetched lies within the cache before
blindly writing to it. As such it is possible for the guest to
overwrite hypervisor memory.

It is currently believed that the only way to trigger this bug is to
use the way that Xen currently incorrectly wraps CS:IP in 16 bit
modes. The included patch prevents such wrapping.

A malicious HVM guest administrator can escalate their privilege to
that of the host."
  );
  script_set_attribute(
    attribute:"see_also",
    value:"https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=214936"
  );
  script_set_attribute(
    attribute:"see_also",
    value:"https://xenbits.xen.org/xsa/advisory-186.html"
  );
  # http://www.freebsd.org/ports/portaudit/49211361-ba4d-11e6-ae1b-002590263bf5.html
  script_set_attribute(
    attribute:"see_also",
    value:"http://www.nessus.org/u?1c121fdb"
  );
  script_set_attribute(attribute:"solution", value:"Update the affected packages.");
  script_set_cvss_base_vector("CVSS2#AV:L/AC:L/Au:N/C:C/I:C/A:C");
  script_set_cvss3_base_vector("CVSS:3.0/AV:L/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H");

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

  script_set_attribute(attribute:"vuln_publication_date", value:"2016/09/08");
  script_set_attribute(attribute:"patch_publication_date", value:"2016/12/04");
  script_set_attribute(attribute:"plugin_publication_date", value:"2016/12/05");
  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:"xen-kernel=4.5.3")) flag++;
if (pkg_test(save_report:TRUE, pkg:"xen-kernel=4.6.3")) flag++;
if (pkg_test(save_report:TRUE, pkg:"xen-kernel>=4.7.0<4.7.1")) flag++;

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