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The system must not forward IPv4 source-routed packets.


Overview

Finding ID Version Rule ID IA Controls Severity
V-12002 GEN003600 SV-45719r1_rule Medium
Description
Source-routed packets allow the source of the packet to suggest routers forward the packet along a different path than configured on the router, which can be used to bypass network security measures. This requirement applies only to the forwarding of source-routed traffic, such as when IPv4 forwarding is enabled and the system is functioning as a router.
STIG Date
SUSE Linux Enterprise Server v11 for System z Security Technical Implementation Guide 2018-09-19

Details

Check Text ( C-43085r1_chk )
Verify the system does not accept source-routed IPv4 packets.

Procedure:
# grep [01] /proc/sys/net/ipv4/conf/*/accept_source_route|egrep "default|all"

If all of the returned lines do not end with 0, this is a finding.

Note: The same setting is used by Linux for both the local acceptance and forwarding of source-routed IPv4 packets.
Fix Text (F-39117r1_fix)
Configure the system to not accept source-routed IPv4 packets.
Edit /etc/sysctl.conf and add a setting for "net.ipv4.conf.all.accept_source_route=0" and "net.ipv4.conf.default.accept_source_route=0".

Reload the sysctls.
Procedure:
# sysctl -p