Ensure Reverse Path Filtering is enabled

中级别 1自动化cos

说明

Setting net.ipv4.conf.all.rp_filter and net.ipv4.conf.default.rp_filter to 1 forces the Linux kernel to utilize reverse path filtering on a received packet to determine if the packet was valid. Essentially, with reverse path filtering, if the return packet does not go out the same interface that the corresponding source packet came from, the packet is dropped (and logged if log_martians is set). Setting these flags is a good way to deter attackers from sending your system bogus packets that cannot be responded to. One instance where this feature breaks down is if asymmetrical routing is employed. This would occur when using dynamic routing protocols (bgp, ospf, etc) on your system. If you are using asymmetrical routing on your system, you will not be able to enable this feature without breaking the routing.

检查方式

审计方法: Shell 命令

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.rp_filter 1 && chk net.ipv4.conf.default.rp_filter 1; then echo compliant; fi

预期输出: compliant

修复方式

修复方法: 操作指南或基础设施补丁

Set the following parameters in /etc/sysctl.conf or a /etc/sysctl.d/* file: net.ipv4.conf.all.rp_filter = 1 net.ipv4.conf.default.rp_filter = 1 Run the following commands to set the active kernel parameters: # sysctl -w net.ipv4.conf.all.rp_filter=1 # sysctl -w net.ipv4.conf.default.rp_filter=1 # 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.

属性

操作系统: 任意
标签: container-optimized-oscos
参考: CIS Google Container-Optimized OS Benchmark v1.2.0 - 3.2.7 Ensure Reverse Path Filtering is enabled

检查本机

请在您有权审计的机器上运行此命令。扫描为只读操作。

shell

tmaegis scan --target cos