FreeBSD : gnupg -- remotely controllable function pointer (4db1669c-8589-11db-ac4f-02e081235dab)

2006-12-11T00:00:00
ID FREEBSD_PKG_4DB1669C858911DBAC4F02E081235DAB.NASL
Type nessus
Reporter This script is Copyright (C) 2006-2019 and is owned by Tenable, Inc. or an Affiliate thereof.
Modified 2019-11-02T00:00:00

Description

Werner Koch reports :

GnuPG uses data structures called filters to process OpenPGP messages. These filters are used in a similar way as a pipelines in the shell. For communication between these filters context structures are used. These are usually allocated on the stack and passed to the filter functions. At most places the OpenPGP data stream fed into these filters is closed before the context structure gets deallocated. While decrypting encrypted packets, this may not happen in all cases and the filter may use a void contest structure filled with garbage. An attacker may control this garbage. The filter context includes another context used by the low-level decryption to access the decryption algorithm. This is done using a function pointer. By carefully crafting an OpenPGP message, an attacker may control this function pointer and call an arbitrary function of the process. Obviously an exploit needs to prepared for a specific version, compiler, libc, etc to be successful - but it is definitely doable.

Fixing this is obvious: We need to allocate the context on the heap and use a reference count to keep it valid as long as either the controlling code or the filter code needs it.

We have checked all other usages of such a stack based filter contexts but fortunately found no other vulnerable places. This allows to release a relatively small patch. However, for reasons of code cleanness and easier audits we will soon start to change all these stack based filter contexts to heap based ones.

                                        
                                            #%NASL_MIN_LEVEL 80502
#
# (C) Tenable Network Security, Inc.
#
# The descriptive text and package checks in this plugin were  
# extracted from the FreeBSD VuXML database :
#
# Copyright 2003-2018 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(23794);
  script_version("1.13");
  script_cvs_date("Date: 2019/08/02 13:32:38");

  script_cve_id("CVE-2006-6235");
  script_xref(name:"Secunia", value:"23245");

  script_name(english:"FreeBSD : gnupg -- remotely controllable function pointer (4db1669c-8589-11db-ac4f-02e081235dab)");
  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:
"Werner Koch reports :

GnuPG uses data structures called filters to process OpenPGP messages.
These filters are used in a similar way as a pipelines in the shell.
For communication between these filters context structures are used.
These are usually allocated on the stack and passed to the filter
functions. At most places the OpenPGP data stream fed into these
filters is closed before the context structure gets deallocated. While
decrypting encrypted packets, this may not happen in all cases and the
filter may use a void contest structure filled with garbage. An
attacker may control this garbage. The filter context includes another
context used by the low-level decryption to access the decryption
algorithm. This is done using a function pointer. By carefully
crafting an OpenPGP message, an attacker may control this function
pointer and call an arbitrary function of the process. Obviously an
exploit needs to prepared for a specific version, compiler, libc, etc
to be successful - but it is definitely doable.

Fixing this is obvious: We need to allocate the context on the heap
and use a reference count to keep it valid as long as either the
controlling code or the filter code needs it.

We have checked all other usages of such a stack based filter contexts
but fortunately found no other vulnerable places. This allows to
release a relatively small patch. However, for reasons of code
cleanness and easier audits we will soon start to change all these
stack based filter contexts to heap based ones."
  );
  # http://lists.gnupg.org/pipermail/gnupg-announce/2006q4/000246.html
  script_set_attribute(
    attribute:"see_also",
    value:"https://lists.gnupg.org/pipermail/gnupg-announce/2006q4/000246.html"
  );
  # https://vuxml.freebsd.org/freebsd/4db1669c-8589-11db-ac4f-02e081235dab.html
  script_set_attribute(
    attribute:"see_also",
    value:"http://www.nessus.org/u?aa061560"
  );
  script_set_attribute(attribute:"solution", value:"Update the affected package.");
  script_set_cvss_base_vector("CVSS2#AV:N/AC:L/Au:N/C:C/I:C/A:C");

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

  script_set_attribute(attribute:"vuln_publication_date", value:"2006/12/04");
  script_set_attribute(attribute:"patch_publication_date", value:"2006/12/07");
  script_set_attribute(attribute:"plugin_publication_date", value:"2006/12/11");
  script_end_attributes();

  script_category(ACT_GATHER_INFO);
  script_copyright(english:"This script is Copyright (C) 2006-2019 and is owned by Tenable, Inc. or an Affiliate thereof.");
  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:"gnupg<1.4.6")) 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");