Title

RHEL 8 must use reverse path filtering on all IPv4 interfaces. (Cat II impact)

Discussion

It is detrimental for operating systems to provide, or install by default, functionality exceeding requirements or mission objectives. These unnecessary capabilities or services are often overlooked and therefore, may remain unsecured. They increase the risk to the platform by providing additional attack vectors. The sysctl --system command will load settings from all system configuration files. All configuration files are sorted by their filename in lexicographical order, regardless of which of the directories they reside in. If multiple files specify the same option, the entry in the file with the lexicographically latest name will take precedence. Files are read from directories in the following list from top to bottom. Once a file of a given filename is loaded, any file of the same name in subsequent directories is ignored. /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf /usr/lib/sysctl.d/*.conf /lib/sysctl.d/*.conf /etc/sysctl.conf

Check Content

Verify RHEL 8 uses reverse path filtering on IPv4 interfaces with the following commands: $ sudo sysctl net.ipv4.conf.default.rp_filter net.ipv4.conf.default.rp_filter = 1 If "net.ipv4.conf.default.rp_filter" is not set to "1" or is missing, this is a finding.

Fix Text

Configure RHEL 8 to use reverse path filtering on IPv4 interfaces by default. Add or edit the following line in a single system configuration file in the "/etc/sysctl.d/" directory: Create a configuration file if it does not already exist: $ sudo vi /etc/sysctl.d/ipv4_rp_filter.conf net.ipv4.conf.default.rp_filter = 1 Load settings from all system configuration files with the following command: $ sudo sysctl --system

Additional Identifiers

Rule ID: SV-230549r1155416_rule

Vulnerability ID: V-230549

Group Title: SRG-OS-000480-GPOS-00227

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