SEC Consult Vulnerability Lab Security Advisory < 20181130-0 >
=======================================================================
              title: Multiple Vulnerabilities
            product: Siglent Technologies SDS 1202X-E Digital Oscilloscope
 vulnerable version: V5.1.3.13
      fixed version: -
         CVE number: -
             impact: High
           homepage: http://siglenteu.com/
                     https://www.siglent.eu/
                     https://www.siglentamerica.com/
              found: 2018-08-06
                 by: T. Weber (Office Vienna)
                     SEC Consult Vulnerability Lab

                     An integrated part of SEC Consult
                     Europe | Asia | North America

                     https://www.sec-consult.com

=======================================================================

Vendor description:
-------------------
"SIGLENT is an international high-tech company, concentrating on R&D, sales,
production and services of measurement products. As an ISO9001:2000
International Quality Management System and ISO 14001:2004 Environmental
Management System Certified company, SIGLENT is also a member of the China
Electronic Instrument Industry Association and Guangdong Instrument
Representative Association.
[...]
SIGLENT focuses on the electronic test & measurement instrument industry and
sees research & development as a core competency, while keeping a strong
competitive edge through technology innovation and strict quality control. Try
a Siglent product. Then compare the performance and the features to any other
model, any other brand. Then compare the price. We believe there is no better
value anyplace."

Source: http://www.siglenteu.com/about.aspx


Business recommendation:
------------------------
The identified backdoor accounts are accessible through Telnet, hence a compromise
of the device via a local network attack is possible.

Any malicious modification of measurement values may have serious impact on the
product or service which is created or offered by using this oscilloscope.
Therefore, all procedures which are executed with this device are untrustworthy.

SEC Consult recommends not to use this product within a network of a production
environment until a thorough security review has been performed by security
professionals and all identified issues have been resolved.

The vendor was unresponsive and did not provide a patch.


Vulnerability overview/description:
-----------------------------------
1) Hardcoded Backdoor Accounts
Two backdoor accounts are present on the system. A Telnet service is listening
on port 23 which enables an attacker to connect as root to the oscilloscope via
LAN.

The password hashes are hardcoded and are difficult to change for the end user
because the "shadow" file is stored on a cramfs (intentionally write-only)
file system.


2) Missing Authentication / Design Issue
The software "EasyScopeX" can be used from any computer in the network to
configure and interact with the oscilloscope. This is possible without prior
authentication which enables everyone to change settings on the oscilloscope.


3) Unencrypted Communication
The software "EasyScopeX" communicates via unencrypted TCP packets with the
client computer / oscilloscope.


4) Outdated and Vulnerable Software Components
Multiple software components embedded in the firmware are outdated and found
to be vulnerable to various publicly known security issues.


Proof of concept:
-----------------
1) Hardcoded Backdoor Accounts
The following password hashes were dumped from "/etc/shadow" by connecting to
the UART interface on the PCB:

root
siglent
(The password hashes have been removed from this advisory)


2) Missing Authentication / Design Issue
It is sufficient to install the "EasyScopeX" software and control the oscilloscope
without any authentication.


3) Unencrypted Communication
The software "EasyScopeX" communicates in plaintext via various ports by using
the portmapper. The default ports are "5024" and "5025".


4) Outdated and Vulnerable Software Components
Using the IoT Inspector software we found the following outdated and vulnerable
components:
* BusyBox 1.20.1
* GNU glibc 2.13
* Linux Kernel 3.19.0


Vulnerable / tested versions:
-----------------------------
The following device / firmware version has been tested:
* Siglent SDS1202X-E (V5.1.3.13)

It is assumed that other firmware versions are affected as well.


Vendor contact timeline:
------------------------
2018-08-22: Contacting German VDE CERT for coordination support
2018-09-04: Asking for a status update from the vendor
2018-09-05: VDE CERT: no response from vendor yet
2018-09-12: US sales person from Siglent has answered, VDE CERT
            is sending advisory to be forwarded to engineering
2018-10-10: Asking for a status update (affected versions, etc)
2018-10-10: VDE CERT: asking vendor for update, vendor reply:
            "I forwarded it to our VP of Engineering for
            consideration. The R&D offices are located in China,
            so I do not have any further visibility or information."
2018-10-12: VDE CERT: if there are no news until end of October,
            we will release security advisory beginning of November
2018-11-23: VDE CERT: no news from the vendor, planning release
2018-11-30: Public release of security advisory


Solution:
---------
The vendor was unresponsive and did not provide a patch. See workaround section
to reduce the attack surface.


Workaround:
-----------
* Don't use the LAN interface or if needed use only in trusted networks
* Connect to the UART interface and place a script which closes port 23 on the
  device during bootup if Telnet is not used.


Advisory URL:
-------------
https://www.sec-consult.com/en/vulnerability-lab/advisories/index.html


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EOF T. Weber / @2018