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


Finding ID Version Rule ID IA Controls Severity
V-38554 RHEL-06-000189 SV-50355r3_rule Low
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.
Red Hat Enterprise Linux 6 Security Technical Implementation Guide 2015-05-26


Check Text ( C-46112r2_chk )
To determine if the system is configured to audit calls to the "fchownat" system call, run the following command:

$ sudo grep -w "fchownat" /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-43502r2_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 fchownat -F auid>=500 -F auid!=4294967295 \
-k perm_mod
-a always,exit -F arch=b32 -S fchownat -F auid=0 -k perm_mod

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

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