Ensure net.ipv4.conf.default.rp_filter is configured

中レベル 1自動linux

説明

net.ipv4.conf.default.rp_filter controls reverse path filtering for IPv4 traffic on newly added network interfaces. Reverse path filtering is a security mechanism in Linux that helps prevent IP spoofing and other network attacks. When enabled, it checks if the source IP address of an incoming packet is reachable through the same network interface it was received on. If the packet's source address is not reachable through the interface it arrived on, the packet is dropped. More information about the kernel parameter configuration files, their location, and load preference is available in the "C

チェック方法

監査方法: シェルコマンド

shell

chk() { p=$1; allowed=" $2 "; case $p in net.ipv6.*) [ -d /proc/sys/net/ipv6 ] || return 0;; esac; v=$(sysctl -n "$p" 2>/dev/null) || { echo "$p: not available"; return 1; }; case "$allowed" in *" $v "*) ;; *) echo "$p is $v (running)"; return 1;; esac; sd=$(readlink -e /lib/systemd/systemd-sysctl || readlink -e /usr/lib/systemd/systemd-sysctl); f=$("$sd" --cat-config 2>/dev/null | grep -Po "^\h*${p//./\.}\h*=\h*\K\H+" | tail -n1); [ -n "$f" ] || { echo "$p is not set in any sysctl configuration file"; return 1; }; case "$allowed" in *" $f "*) ;; *) echo "$p is $f in configuration"; return 1;; esac; }; if chk net.ipv4.conf.default.rp_filter 1; 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

1. Review all files being used by systemd sysctl and comment out or remove all net.ipv4.conf.default.rp_filter lines that are not net.ipv4.conf.default.rp_filter=1. Example script: #!/usr/bin/env bash { l_option="net.ipv4.conf.default.rp_filter" l_value="1" l_grep="${l_option//./(\\.|\\/)}" a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Psio -- '^\h*#\h*\/[^#…

プロパティ

オペレーティングシステム: almalinux-9
タグ: cis-convertedkernellinuxsysctl
参照: CIS AlmaLinux OS 9 Benchmark v3.0.0 - 3.3.1.13

このホストをチェック

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