Ensure SSH LogLevel is appropriate

MediumLevel 1Automatedlinux

Description

INFO level is the basic level that only records login activity of SSH users. In many situations, such as Incident Response, it is important to determine when a particular user was active on a system. The logout record can eliminate those users who disconnected, which helps narrow the field. VERBOSE level specifies that login and logout activity as well as the key fingerprint for any SSH key used for login will be logged. This information is important for SSH key management, especially in legacy environments.

How it is checked

Audit method: Shell command

shell

alt0() { command -v grep >/dev/null 2>&1 || { echo "step1: grep not installed"; return 1; }; command -v sshd >/dev/null 2>&1 || { echo "step1: sshd not installed"; return 1; }; o=$(bash -c 'sshd -T | grep loglevel' 2>&1); printf '%s\n' "$o" | tr -s ' \t' '  ' | sed 's/^ //;s/ $//' | grep -Fxq -- 'LogLevel VERBOSE' || { echo step1: missing 'LogLevel VERBOSE'; return 1; }; }; if alt0; then echo compliant; fi

Expected output: compliant

How it is fixed

Fix method: Guidance or infrastructure patch

Edit the /etc/ssh/sshd_config file to set the parameter as follows: LogLevel VERBOSE or LogLevel INFO Restart sshd : systemctl restart sshd

Properties

Operating systems: alinux-2
Tags: cis-convertedlinux
Reference: CIS Aliyun Linux 2 Benchmark v1.0.0 ARCHIVE - 5.2.5

Check this host

Run this on a machine you are allowed to audit. The scan is read-only.

shell

tmaegis scan --target linux