Ensure sshd MACs are configured

中レベル 1自動linux

説明

This variable limits the types of MAC algorithms that SSH can use during communication. Notes: • Some organizations may have stricter requirements for approved MACs. • Ensure that MACs used are in compliance with site policy. • The only "strong" MACs currently FIPS 140 approved are: o HMAC-SHA1 o HMAC-SHA2-256 o HMAC-SHA2-384 o HMAC-SHA2-512

チェック方法

監査方法: シェルコマンド

shell

alt0() { o=$(bash -c '#!/usr/bin/env bash
{
   a_weak=(hmac-md5 hmac-md5-96 hmac-ripemd160 hmac-sha1-96 umac- 64@openssh.com hmac-md5-etm@openssh.com hmac-md5-96-etm@openssh.com hmac- ripemd160-etm@openssh.com hmac-sha1-96-etm@openssh.com umac-64- etm@openssh.com)
   l_offered="$(sshd -T | awk '"'"'$1=="macs"{print $2}'"'"' | tr '"'"','"'"' '"'"'\n'"'"')"
   for l_alg in "${a_weak[@]}"; do
      grep -Fxq -- "$l_alg" <<< "$l_offered" && printf '"'"'%s\n'"'"' "$l_alg"
   done
}' 2>&1); [ -z "$o" ] || { echo "step1: $o" | head -c 300; return 1; }; }; if alt0; then echo compliant; fi

期待される出力: compliant

修正方法

修正方法: ガイダンスまたは IaC パッチ

The MAC algorithms available to the SSH server are governed by the system-wide crypto policy. Disable the weak MACs by configuring the system-wide crypto policy as described in the "Configure system wide crypto policy" section. - IF - CVE-2023-48795 (Terrapin) has not been reviewed and addressed, the Encrypt- then-MAC (EtM) MACs should also be disabled through the system-wide crypto policy. Once the crypto policy has been updated, reload the SSH daemon: # systemctl reload-or-restart sshd

プロパティ

オペレーティングシステム: rocky-9
タグ: cis-convertedlinux
参照: CIS Rocky Linux 9 Benchmark v3.0.0 - 5.1.7

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監査が許可されているマシンで実行してください。スキャンは読み取り専用です。

shell

tmaegis scan --target linux