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


Overview

Finding ID Version Rule ID IA Controls Severity
V-38556 RHEL-06-000190 SV-50357r3_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 2015-05-26

Details

Check Text ( C-46114r2_chk )
To determine if the system is configured to audit calls to the "fremovexattr" system call, run the following command:

$ sudo grep -w "fremovexattr" /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-43504r2_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 fremovexattr -F auid>=500 -F auid!=4294967295 \
-k perm_mod
-a always,exit -F arch=b32 -S fremovexattr -F auid=0 -k perm_mod

If the system is 64-bit, then also add the following:

-a always,exit -F arch=b64 -S fremovexattr -F auid>=500 -F auid!=4294967295 \
-k perm_mod
-a always,exit -F arch=b64 -S fremovexattr -F auid=0 -k perm_mod