NetBSD Security Advisory 2016-005: bozohttpd CGI handlers potential remote code execution

[NetBSD Security-Officer <security-officer%netbsd.org@localhost>]

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                 NetBSD Security Advisory 2016-005
                 =================================

Topic:          bozohttpd CGI handlers potential remote code execution

Version:        NetBSD-current:         20160415
                NetBSD 7.0:             affected
                NetBSD 6.1 - 6.1.5:     affected
                NetBSD 6.0 - 6.0.6:     affected

Severity:       Potential execution of arbitrary commands as httpd user

Fixed:          NetBSD-current:         April 15, 2016
                NetBSD-7 branch:        April 15, 2016
                NetBSD-6 branch:        April 15, 2016
                NetBSD-6-1 branch:      April 15, 2016
                NetBSD-6-0 branch:      April 15, 2016
                pkgsrc:                 bozohttpd-20160415 corrects this issue

Please note that NetBSD releases prior to 6.0 are no longer supported.
It is recommended that all users upgrade to a supported release.

Abstract
========

Running programs as CGI handlers that were not designed to serve as such
may create a vulnerability since bozohttpd would pass any arguments
to the executed binary.  In the worst case scenario this may lead to
remote code execution.

This vulnerability has been assigned CVE-2015-8212.

Technical Details
=================

bozohttpd supports option -C which can be used to add a CGI handler for a
particular file type. It was designed to support both CGI and non-CGI aware
programs to serve dynamic content. Binaries were executed using arguments
from the remote client. In case of non-CGI programs this can be abused
to exploit features of such programs and change their behaviour, which
in worst case scenario can lead to running attacker-provided code.

It was proven that arbitrary code can be executed in case of PHP-CLI
as CGI handler.


Solutions and Workarounds
=========================

This problem only affects users which use not-CGI aware programs as
CGI handlers (such as sh, CLI version of PHP etc.) directly.
The simplest fix is to install the latest pkgsrc bozohttpd which fixes this
problem (and run it instead of the system one). Support for non-CGI handlers
has been removed as there's no way to securely handle user's requests.

cd /var/tmp
ftp http://nyftp.netbsd.org/pub/NetBSD-daily/<rel>/<build>/<arch>/binary/sets/base.tgz
cd /
tar xzpf /var/tmp/base.tgz ./usr/libexec/httpd

with the following replacements:
<rel>   = the release version you are using
<build> = the source date of the build. 20160416* and later will fit
<arch>  = your system's architecture

The following instructions describe how to upgrade your bozohttpd
binaries by updating your source tree and rebuilding and
installing a new version of bozohttpd.

The following instructions describe how to upgrade your bozohttpd
binary by updating your source tree and rebuilding and installing
a new version of bozohttpd.


* NetBSD-current:

        Systems running NetBSD-current dated from before 2016-04-15
        should be upgraded to NetBSD-current dated 2016-04-16 or later.

        The following files/directories need to be updated from the
        netbsd-current CVS branch (aka HEAD):
                src/libexec/httpd

        To update from CVS, re-build, and re-install bozohttpd:
                # cd src
                # cvs update -d -P libexec/httpd
                # cd libexec/httpd
                # make USETOOLS=no cleandir dependall
                # make USETOOLS=no install

* NetBSD 7.*:

        Systems running NetBSD 7.* sources dated from before
        2016-04-15 should be upgraded from NetBSD 7.* sources dated
        2016-04-16 or later.

        The following files/directories need to be updated from the
        netbsd-7, netbsd-7-0 branches:
                src/libexec/httpd

        To update from CVS, re-build, and re-install bozohttpd:

                # cd src
                # cvs update -r <branch_name> -d -P libexec/httpd
                # cd libexec/httpd
                # make USETOOLS=no cleandir dependall
                # make USETOOLS=no install



* NetBSD 6.*:

        Systems running NetBSD 6.* sources dated from before
        2016-04-15 should be upgraded from NetBSD 6.* sources dated
        2016-04-16 or later.

        The following files/directories need to be updated from the
        netbsd-6, netbsd-6-1 or netbsd-6-0 branches:
                src/libexec/httpd

        To update from CVS, re-build, and re-install bozohttpd:

                # cd src
                # cvs update -r <branch_name> -d -P libexec/httpd
                # cd libexec/httpd
                # make USETOOLS=no cleandir dependall
                # make USETOOLS=no install

Thanks To
=========

Thanks go to Mateusz Kocielski who found this problem and supplied
the fixes.

Revision History
================

        2016-04-21     Initial release

More Information
================

Advisories may be updated as new information becomes available.
The most recent version of this advisory (PGP signed) can be found at 
  http://ftp.NetBSD.org/pub/NetBSD/security/advisories/NetBSD-SA2016-005.txt.asc

Information about NetBSD and NetBSD security can be found at
http://www.NetBSD.org/ and http://www.NetBSD.org/Security/ .

Copyright 2016, The NetBSD Foundation, Inc.  All Rights Reserved.
Redistribution permitted only in full, unmodified form.

$Id: NetBSD-SA2016-005.txt,v 1.1 2016/04/21 16:15:07 christos Exp $

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