The audit system must be configured to audit all discretionary access control permission modifications using fchmodat.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-38550	RHEL-06-000187	SV-50351r3_rule		Low

Description
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.

STIG	Date
Red Hat Enterprise Linux 6 Security Technical Implementation Guide	2016-12-16

Details

Check Text ( C-46108r2_chk )
To determine if the system is configured to audit calls to the "fchmodat" system call, run the following command: $ sudo grep -w "fchmodat" /etc/audit/audit.rules If the system is configured to audit this activity, it will return several lines. If no line is returned, this is a finding.

Fix Text (F-43498r2_fix)

At a minimum, the audit system should collect file permission changes for all users and root. Add the following to "/etc/audit/audit.rules": -a always,exit -F arch=b32 -S fchmodat -F auid>=500 -F auid!=4294967295 \ -k perm_mod -a always,exit -F arch=b32 -S fchmodat -F auid=0 -k perm_mod If the system is 64-bit, then also add the following: -a always,exit -F arch=b64 -S fchmodat -F auid>=500 -F auid!=4294967295 \ -k perm_mod -a always,exit -F arch=b64 -S fchmodat -F auid=0 -k perm_mod