Linux: Remediate SSL Weak Cipher Suites

Description

The remote host supports the use of SSL ciphers that offer weak encryption.

Note: This is considerably easier to exploit if the attacker is on the same physical network.

Output

Here is the list of weak SSL ciphers supported by the remote server :

Low Strength Ciphers (<= 64-bit key)

DES-CBC-SHA Kx=RSA Au=RSA Enc=DES-CBC(56) Mac=SHA1

The fields above are :

{OpenSSL ciphername}
Kx={key exchange}
Au={authentication}
Enc={symmetric encryption method}
Mac={message authentication code}
{export flag}

Source: Tenable.IO

Solution

Reconfigure the affected application, if possible to avoid the use of weak ciphers.

Edit the following file:

sudo vim /etc/httpd/conf.d/ssl.conf

… with this content:

SSLProtocol -all -SSLv2 -SSLv3 -TLSv1 +TLSv1.1 +TLSv1.2

SSLCipherSuite "EECDH+ECDSA+AESGCM EECDH+aRSA+AESGCM EECDH+ECDSA+SHA384 EECDH+ECDSA+SHA256 EECDH+aRSA+SHA384 EECDH+aRSA+SHA256 !EECDH+aRSA+RC4 EECDH EDH+aRSA !RC4 !aNULL !eNULL !LOW !3DES !MD5 !EXP !PSK !SRP !DSS !EDH-RSA-DES-CBC3-SHA !ECDHE-RSA-DES-CBC3-SHA !DES-CBC3-SHA !ECDHE-RSA-RC4-SHA !RC4-MD5 !RC4-SHA"

For Windows, follow this script: https://blog.kimconnect.com/powershell-windows-2016-pristine-image