Ensure packet redirect sending is disabled

보통레벨 1자동cos

설명

ICMP Redirects are used to send routing information to other hosts. As a host itself does not act as a router (in a host only configuration), there is no need to send redirects. An attacker could use a compromised host to send invalid ICMP redirects to other router devices in an attempt to corrupt routing and have users access a system set up by the attacker as opposed to a valid system.

점검 방법

감사 방식: 셸 명령

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.all.send_redirects 0 && chk net.ipv4.conf.default.send_redirects 0; then echo compliant; fi

예상 출력: compliant

조치 방법

조치 방식: 가이드 또는 인프라 패치

Set the following parameters in /etc/sysctl.conf or a /etc/sysctl.d/* file: net.ipv4.conf.all.send_redirects = 0 net.ipv4.conf.default.send_redirects = 0 Run the following commands to set the active kernel parameters: # sysctl -w net.ipv4.conf.all.send_redirects=0 # sysctl -w net.ipv4.conf.default.send_redirects=0 # sysctl -w net.ipv4.route.flush=1 /etc is stateless on Container-Optimized OS. Therefore, /etc cannot be used to make these changes persistent across reboots. The steps mentioned above needs to be performed after every boot.

속성

운영 체제: 모두
태그: container-optimized-oscos
참고 자료: CIS Google Container-Optimized OS Benchmark v1.2.0 - 3.1.1 Ensure packet redirect sending is disabled

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shell

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