Vulnerability Discussion

Without the capability to generate audit records, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

If auditing is enabled late in the startup process, the actions of some startup processes may not be audited. Some audit systems also maintain state information only available if auditing is enabled before a given process is created.

Audit records can be generated from various components within the information system (e.g., module or policy filter).

Allocating an audit_backlog_limit of sufficient size is critical in maintaining a stable boot process. With an insufficient limit allocated, the system is susceptible to boot failures and crashes.

Check

Verify RHEL 8 allocates a sufficient audit_backlog_limit to capture processes that start prior to the audit daemon with the following commands:

$ sudo grub2-editenv list | grep audit

kernelopts=root=/dev/mapper/rhel-root ro crashkernel=auto resume=/dev/mapper/rhel-swap rd.lvm.lv=rhel/root rd.lvm.lv=rhel/swap rhgb quiet fips=1 audit=1 audit_backlog_limit=8192 boot=UUID=8d171156-cd61-421c-ba41-1c021ac29e82

If the "audit_backlog_limit" entry does not equal "8192" or greater, is missing, or the line is commented out, this is a finding.

Check the audit_backlog_limit is set to persist in kernel updates:

$ sudo grep audit /etc/default/grub

GRUB_CMDLINE_LINUX="audit_backlog_limit=8192"

If "audit_backlog_limit" is not set to "8192" or greater, is missing or commented out, this is a finding.

Fix

Configure RHEL 8 to allocate sufficient audit_backlog_limit to capture processes that start prior to the audit daemon with the following command:

$ sudo grubby --update-kernel=ALL --args="audit_backlog_limit=8192"

Add or modify the following line in "/etc/default/grub" to ensure the configuration survives kernel updates:

GRUB_CMDLINE_LINUX="audit_backlog_limit=8192"