Ensure sshd PermitUserEnvironment is disabled

MediumLevel 1Automatedaix

Description

The PermitUserEnvironment option allows users to present environment options to the SSH daemon. Permitting users the ability to set environment variables through the SSH daemon could potentially allow users to bypass security controls (e.g. setting an execution path that has SSH executing trojan'd programs) Audit: evaluates the effective configuration from `sshd -T` (Match blocks must be reviewed separately).

How it is checked

Audit method: Shell command

shell

command -v sshd >/dev/null 2>&1 || exit 1; out=$(sshd -T 2>/dev/null) || exit 1; r=compliant; for p in '^permituserenvironment[[:blank:]]+no$'; do printf '%s\n' "$out" | grep -Eiq -- "$p" || r="not matched: $p"; done; echo "$r"

Expected output: compliant

How it is fixed

Fix method: Guidance or infrastructure patch

Edit the /etc/ssh/sshd_config file to set the parameter: PermitUserEnvironment no Re-cycle the sshd daemon to pick up the configuration changes: stopsrc -s sshd startsrc -s sshd

Properties

Operating systems: Any
Tags: aixssh
Reference: CIS IBM AIX 7 Benchmark v1.2.0 - 4.6.3.16 Ensure sshd PermitUserEnvironment is disabled

Check this host

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

shell

tmaegis scan --target aix