Vulnerability Discussion

The changing of file permissions could indicate that a user is attempting to gain access to information that would otherwise be disallowed. Auditing DAC modifications can facilitate the identification of patterns of abuse among both authorized and unauthorized users.

Satisfies: SRG-OS-000037-GPOS-00015, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215

Check

Verify that OL 9 generates an audit record for all uses of the umount system call with the following commands:

$ sudo grep "umount" /etc/audit/audit.*

$ sudo grep umount /etc/audit/audit.rules

If the system is configured to audit this activity, it will return a line like the following:

-a always,exit -F arch=b32 -S umount -F auid>=1000 -F auid!=unset -k privileged-umount

If the command does not return a line or the line is commented out, this is a finding.

Fix

Configure the audit system to generate an audit event for any successful/unsuccessful use of the umount system call by adding or updating the following rules in "/etc/audit/audit.rules" and adding the following rules to "/etc/audit/rules.d/perm_mod.rules" or updating the existing rules in files in the "/etc/audit/rules.d/" directory:

-a always,exit -F arch=b32 -S umount -F auid>=1000 -F auid!=unset -k perm_mod -a always,exit -F arch=b64 -S umount -F auid>=1000 -F auid!=unset -k perm_mod

The audit daemon must be restarted for the changes to take effect.

Restart auditd:
$ sudo service auditd restart