Tuesday, December 6, 2016

Backdoor in Sony IPELA Engine IP Cameras

SEC Consult has found a backdoor in Sony IPELA Engine IP Cameras, mainly used professionally by enterprises and authorities. This backdoor allows an attacker to run arbitrary code on the affected IP cameras. An attacker can use cameras to take a foothold in a network and launch further attacks, disrupt camera functionality, send manipulated images/video, add cameras into a Mirai-like botnet or to just simply spy on you. This vulnerability affects 80 different Sony camera models. Sony was informed by SEC Consult about the vulnerability and has since released updated firmware for the affected models.

Further information about the backdoor, disclosure timeline, affected devices and updated firmware can be found in our advisory. This blog post has some highlights from the vulnerability analysis.

This advisory is the result of research that started by uploading a recent firmware update file from a Sony camera into our cloud based firmware analysis system IoT Inspector.

After a few minutes the analysis results were available. One result immediately caught our attention:

Excerpt from IoT Inspector results

So here we have two password hashes, one is for the user admin and was cracked immediately. The password is admin. This is no surprise as the default login credentials are admin:admin.

The second password hash is much more interesting, it’s for the user root and it was found in two different files: /etc/init.d/SXX_directory and /usr/local/lib/libg5_usermanage.so.0.0.0

We can use the file system browser of IoT Inspector to have a look at the SXX_directory.

Excerpt from IoT Inspector filesystem browser

It looks like this startup script (called by /sbin/init/rcS during boot) is responsible for creating and populating the file /tmp/etc/passwd (/etc/passwd is a symlink to this file). A line for the user including a password hash is added, the shell is /bin/sh. Not good!

So, what can we do if we can crack the hash? At this point we can assume that it's very likely we can login using UART pins on the PCB. This of course requires us to have physical access and to disassemble the device.

The other locations where we could possibly use the password are Telnet and SSH, but both services are not available on the device … or are they? A quick string search in the firmware's filesystem for “telnet” shows that a CGI binary called prima-factory.cgi contains this string a few times. IDA Pro to the rescue! It seems this CGI has the power to do something with Telnet:

The code in g5::cgifactory::factorySetTelnet() (in decompiled form below) is pretty straight forward. Based on input, the inetd daemon is killed or started:

The inetd daemon gets its configuration from /etc/inetd.conf and inetd.conf is set up to launch Telnet

So how can we reach this CGI functionality? The answer lies in the lighttpd binary. Lighttpd is an open source web server that was modified by Sony. Some custom code for HTTP request handling and authentication was added. Below is an excerpt from a data structure that maps the URI /command/prima-factory.cgi to the CGI in the file system. The authentication function is HandleFactory.

HandleFactory decodes the HTTP Basic Authentication header and compares it to the username/password primana:primana.

Now we have all ingredients to craft an attack that looks like this:

  1. Send HTTP requests to /command/prima-factory.cgi containing the “secret” request values cPoq2fi4cFk and zKw2hEr9 and use primana:primana for HTTP authentication. This starts the Telnet service on the device.
  2. Login using the cracked root credentials via Telnet. Note: We have not cracked the root password, but it's only a matter of time until someone will.

The user primana has access to other functionality intended for device testing or factory calibration(?). There is another user named debug with the password popeyeConnection that has access to other CGI functionality we didn't analyze further.

We believe that this backdoor was introduced by Sony developers on purpose (maybe as a way to debug the device during development or factory functional testing) and not an "unauthorized third party" like in other cases (e.g. the Juniper ScreenOS Backdoor, CVE-2015-7755).

We have asked Sony some questions regarding the nature of the backdoor, intended purpose, when it was introduced and how it was fixed, but they did not answer.

For further information regarding affected devices and patched firmware, see our advisoryIoT Inspector now comes with a plugin that detects this vulnerability.