Linux distributions
TMA-SLES11-3.2.1
Ensure source routed packets are not accepted
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. Internet routable), and so source routed packets would need to be used.
How it is checked
Audit method: Shell command
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.accept_source_route 0 && chk net.ipv4.conf.default.accept_source_route 0; then echo compliant; fi- Expected output
compliant
How it is fixed
Fix method: Guidance or infrastructure patch
Set the following parameters in /etc/sysctl.conf or a /etc/sysctl.d/* file: net.ipv4.conf.all.accept_source_route = 0 net.ipv4.conf.default.accept_source_route = 0 Run the following commands to set the active kernel parameters: # sysctl -w net.ipv4.conf.all.accept_source_route=0 # sysctl -w net.ipv4.conf.default.accept_source_route=0 # sysctl -w net.ipv4.route.flush=1
Properties
- Operating systems
- sles-11
- Tags
- cis-convertedkernellinuxsysctl
- Reference
- CIS SUSE Linux Enterprise 11 Benchmark v2.1.1 - 3.2.1
Check this host
Run this on a machine you are allowed to audit. The scan is read-only.
tmaegis scan --target linux