SSH backdoor discovered in Fortinet FortiOS firewalls
13.1.2016

Another SSH backdoor? Researchers have discovered highly suspicious code in the Fortinet FortiOS firewalls that were shipped with hardcoded logins.
After Juniper, another Enterprise security vendor is in the headlines, this time it is Fortinet for the presence of a SSH ‘backdoor in its firewalls. Less than a month ago, an “unauthorized code” was discovered in the operating system for Juniper NetScreen firewalls. The company admitted the presence of the “unauthorized code” that could allow an attacker to decrypt VPN traffic.
[“unauthorized code”] “could allow a knowledgeable attacker to gain administrative access to NetScreen devices and to decrypt VPN connections.”

Now security experts discovered that Fortinet FortiOS firewalls were shipped with hardcoded SSH logins, this in another embarrassing revelation that raises many questions about surveillance.

According to Ars, the security researcher Ralf-Philipp Weinmann, the same that helped the discovery of the Juniper backdoor, “repeatedly referred to the custom SSH authentication as a “backdoor.” In

“In one specific post, he confirmed he was able to make it work as reported on older versions of Fortinet’s FortiOS.” states Ars.

Fortinet used a secret authentication for FortiOS-based security appliances, but unknown experts were able to make a reverse-engineering of the code discovering the secret passphrase used to access the backdoor.

Clearly the company tried to downgrade the issues, defining the code a “management authentication issue,” instead the term SSH backdoor.

“This issue was resolved and a patch was made available in July 2014 as part of Fortinet¹s commitment to ensuring the quality and integrity of our codebase. This was not a “backdoor” vulnerability issue but rather a management authentication issue. The issue was identified by our Product Security team as part of their regular review and testing efforts. After careful analysis and investigation, we were able to verify this issue was not due to any malicious activity by any party, internal or external. All versions of FortiOS from 5.0.8 and later as well as FortiOS 4.3.17 and later are not impacted by this issue.”

Accessing FortiOS firewalls is very easy considering also that a Python script to exploit the backdoor is available on the Full Disclosure mailing list. Running the script against a vulnerable Forti-OS firewall the attacker will gain administrator-level command-line access to the device.
Fortinet embarrassed for the discovery has promptly removed the weird SSH backdoor discovered in FortiOS firewalls.

Fortinet has tried to explain the disconcerting incident in a security advisory, the company confirmed that the issue affects the FortiOS versions 4.3.0 to 4.3.16 and 5.0.0 to 5.0.7 deployed in FortiOS from between November 2012 and July 2014.

“This issue was resolved and a patch was made available in July 2014 as part of Fortinet’s commitment to ensuring the quality and integrity of our codebase,” a spokeswoman told El Reg. “This was not a ‘backdoor’ vulnerability issue but rather a management authentication issue. The issue was identified by our product security team as part of their regular review and testing efforts. After careful analysis and investigation, we were able to verify this issue was not due to any malicious activity by any party, internal or external.” state Fortinet, refusing to consider the issue a SSH backdoor.

This means that all the FortiOS-based systems that haven’t been updated their system since the above period are affected by the SSH backdoor.

The company suggests the following workarounds to temporary fix the issue for all those devices that for a number of reasons cannot be updated:

Disable admin access via SSH on all interfaces, and use the Web GUI instead, or the console applet of the GUI for CLI access.
If SSH access is mandatory, in 5.0 one can restrict access to SSH to a minimal set of authorized IP addresses, via the Local In policies.
If you are a sysadmin and are using a FortiOS-based device upgrade its firmware.