The OL 8 SSH server must be configured to use strong entropy.
Overview
| Finding ID | Version | Rule ID | IA Controls | Severity |
| V-248563 | OL08-00-010292 | SV-248563r991593_rule | CCI-000366 | low |
| Description | ||||
| The most important characteristic of a random number generator is its randomness, namely its ability to deliver random numbers that are impossible to predict. Entropy in computer security is associated with the unpredictability of a source of randomness. The random source with high entropy tends to achieve a uniform distribution of random values. Random number generators are one of the most important building blocks of cryptosystems. The SSH implementation in OL 8 uses the OPENSSL library, which does not use high-entropy sources by default. By using the SSH_USE_STRONG_RNG environment variable, the OPENSSL random generator is reseeded from "/dev/random". This setting is not recommended on computers without the hardware random generator because insufficient entropy causes the connection to be blocked until enough entropy is available. | ||||
| STIG | Date | |||
| Oracle Linux 8 Security Technical Implementation Guide | 2025-05-13 | |||
Details
Check Text (C-248563r991593_chk)
Verify the operating system SSH server uses strong entropy with the following command:
$ sudo grep -i ssh_use_strong_rng /etc/sysconfig/sshd
SSH_USE_STRONG_RNG=32
If the "SSH_USE_STRONG_RNG" line does not equal "32" or is commented out or missing, this is a finding.
Fix Text (F-51951r779254_fix)
Configure the operating system SSH server to use strong entropy.
Add or modify the following line in the "/etc/sysconfig/sshd" file.
SSH_USE_STRONG_RNG=32
The SSH service must be restarted for changes to take effect.