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V-261315

CAT II (Medium)

SLEM 5 must prevent Internet Protocol version 4 (IPv4) Internet Control Message Protocol (ICMP) redirect messages from being accepted.

Rule ID

SV-261315r996415_rule

STIG

SUSE Linux Enterprise Micro (SLEM) 5 Security Technical Implementation Guide

Version

V1R4

CCIs

CCI-000366

Discussion

ICMP redirect messages are used by routers to inform hosts that a more direct route exists for a particular destination. These messages modify the host's route table and are unauthenticated. An illicit ICMP redirect message could result in a man-in-the-middle attack.

Check Content

Verify SLEM 5 does not accept IPv4 ICMP redirect messages with the following command:

     > sudo sysctl net.ipv4.conf.all.accept_redirects
     net.ipv4.conf.all.accept_redirects = 0

If the network parameter "ipv4.conf.all.accept_redirects" is not equal to "0", or nothing is returned, this is a finding.

Fix Text

Configure SLEM 5 to not accept IPv4 ICMP redirect messages by running the following command as an administrator:

     > sudo sysctl -w net.ipv4.conf.all.accept_redirects=0

If "0" is not the system's default value, add or update the following line in "/etc/sysctl.d/99-stig.conf":

     > sudo sh -c 'echo "net.ipv4.conf.all.accept_redirects=0" >> /etc/sysctl.d/99-stig.conf'

     > sudo sysctl --system