Weak encryption cipher and hardcoded cryptographic keys in Fortinet products

Project Description

Multiple Fortinet products use a weak encryption cipher (“XOR”) and hardcoded cryptographic keys to communicate with the FortiGuard Web Filter, AntiSpam and AntiVirus cloud services. This allows attackers to eavesdrop on user activity and manipulate server responses.

Vendor description

“From the start, the Fortinet vision has been to deliver broad, truly integrated, high-performance security across the IT infrastructure.

We provide top-rated network and content security, as well as secure access products that share intelligence and work together to form a cooperative fabric. Our unique security fabric combines Security Processors, an intuitive operating system, and applied threat intelligence to give you proven security, exceptional performance, and better visibility and control–while providing easier administration.”

Source: https://www.fortinet.com/corporate/about-us/about-us.html

Business recommendation

The vendor provides a patch and users of affected products are urged to immediately upgrade to the latest version available.

Vulnerability overview/description

Fortinet products, including FortiGate and Forticlient regularly send information to Fortinet servers (DNS: guard.fortinet.com) on

• UDP ports 53, 8888 and
• TCP port 80 (HTTP POST /fgdsvc)

This cloud communication is used for the FortiGuard Web Filter feature, FortiGuard AntiSpam feature and FortiGuard AntiVirus feature.

The messages are encrypted using XOR “encryption” with a static key. The protocol messages contain the following types of information:

Serial number of the Fortinet product installation (product type + unique ID)
This information allows an attacker who can passively monitor internet traffic to:

• learn which Fortinet products and product types an organization uses (this is valuable for information gathering, see EquationGroup Fortigate exploits)
• learn which FortiClient installations are part of an organization
• use the FortiClient serial number as a unique identifier to track an individual as
  he/she travels the world

Full HTTP URLs of users web surfing activity (Web Filter feature)

This information allows an attacker who can passively monitor internet traffic to spy on users’ web surfing activity. In cases where SSL inspection is enabled, even the URLs of HTTPS-encrypted communication are sent via this protocol, effectively breaking the confidentiality of SSL/TLS.

Unspecified email data (AntiSpam feature)

We do not have any further information on what kind of information is sent by the AntiSpam feature.

Unspecified AntiVirus data (AntiVirus feature)

We do not have any further information on what kind of information is sent by the AntiVirus feature.

By intercepting and manipulating internet traffic an attacker can manipulate the responses for FortiGuard Web Filter, AntiSpam and AntiVirus features.

Proof of concept

The following Python 3 script decrypts a FortiGuard message (the static XOR key has been removed from this advisory).

```python
from itertools import cycle

def forti_xor(s1):
    xor_key = **removed**
    message = ''.join(chr(c ^ k) for c, k in zip(s1, cycle(xor_key)))
    return message

r1=bytes.fromhex('6968766f606e776c2d2d21262138475c5b5a475b545e475c6b6a776b646e776c6b6a772b646e776c6b6a776b646e776c6b6a776bbadf04036b6a776c616a846f')

print(repr(forti_xor(r1)))
```

In this case the encrypted message contents are:

'\x02\x02\x01\x04\x04\x00\x00\x00FGVMEV0000000000\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00@\x00\x00\x00\x00\x00\x00...'

Another example:

'\x02\x01\x02\x04úI\x03\x00FG100D3G00000000\x00\x00\...x00\x00+https://v10.vortex-win.data.microsoft.com/\x00'

Vulnerable/Tested versions

The following FortiOS versions are affected according to the vendor:

• FortiOS 6.0.7 and below (Update 2019-11-27: According to Fortinet, also v6.0.7 is affected)
• FortiClientWindows 6.0.6 and below
• FortiClientMac 6.2.1 and below

The security advisory of the vendor can be found at: https://fortiguard.com/psirt/FG-IR-18-100

Vendor contact timeline

Solution

The vendor provides updated versions for the affected products:

• FortiOS 6.2.0 (Update 2019-11-27: According to Fortinet, only 6.2.0 includes the patch, not the previously stated v6.0.7)
• FortiClientWindows 6.2.0
• FortiClientMac 6.2.2

The security advisory of the vendor can be found at: https://fortiguard.com/psirt/FG-IR-18-100

Workaround

None.

Advisory URL

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

EOF Stefan Viehböck / @2019

Project Details

• TitleFortiGuard XOR Encryption
• ProductMultiple Fortinet Products (see Vulnerable / tested versions)
• Vulnerable versionMultiple (see Vulnerable / tested versions)
• Fixed versionMultiple (see Solution)
• CVE numberCVE-2018-9195
• ImpactHigh
• Homepagehttps://www.fortinet.com
• Found2018-05-16
• ByStefan Viehböck (Office Vienna) | SEC Consult Vulnerability Lab