The system must not forward IPv4 source-routed packets.

From SUSE Linux Enterprise Server v11 for System z Security Technical Implementation Guide

Associated with: CCI-001551

SV-45719r1_rule The system must not forward IPv4 source-routed packets.

Vulnerability discussion

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.

Check content

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

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

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