Ensure source routed packets are not accepted

LowLevel 2Automatedbottlerocket

Description

In networking, source routing allows a sender to partially or fully specify the route packets take through a network. In contrast, non-source routed packets travel a path determined by routers in the network. In some cases, systems may not be routable or reachable from some locations (e.g. private addresses vs. The audit reads the running values from /proc/sys (IPv6 keys only when IPv6 is enabled). Run tmaegis on the host through the admin container root shell (sudo sheltie).

How it is checked

Audit method: Shell command

shell

bad=0
chk() { f=/proc/sys/$(printf %s "$1" | tr . /); v=$(cat "$f" 2>/dev/null) || { echo "$1: not readable"; bad=1; return; }; [ "$v" = "$2" ] || { echo "$1 = $v (expected $2)"; bad=1; }; }
chk net.ipv4.conf.all.accept_source_route 0
chk net.ipv4.conf.default.accept_source_route 0
[ -d /proc/sys/net/ipv6 ] && chk net.ipv6.conf.all.accept_source_route 0
[ -d /proc/sys/net/ipv6 ] && chk net.ipv6.conf.default.accept_source_route 0
[ "$bad" -eq 0 ] && echo compliant

Expected output: compliant

How it is fixed

Fix method: Guidance or infrastructure patch

Run the following command to set the active kernel parameters and persist the settings: # apiclient apply <<EOF [settings.kernel.sysctl] "net.ipv4.conf.all.accept_source_route" = "0" "net.ipv4.conf.default.accept_source_route" = "0" "net.ipv6.conf.all.accept_source_route" = "0" "net.ipv6.conf.default.accept_source_route" = "0" EOF Run the following command to flush the routing caches: # sysctl -w net.ipv4.route.flush=1 # sysctl -w net.ipv6.route.flush=1

Properties

Operating systems: Any
Tags: bottlerocketnetwork
Reference: CIS Bottlerocket Benchmark v1.0.0 - 3.2.1 Ensure source routed packets are not accepted

Check this host

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

shell

tmaegis scan --target bottlerocket --level 2