OL6-00-000185 - The audit system must be configured to audit all discretionary access control permission modifications using chown, fchown, fchownat, and lchown - b64 auid>=500

Information

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.

The system call rules are loaded into a matching engine that intercepts each syscall made by all programs on the system. Therefore, it is very important to use syscall rules only when absolutely necessary, since these affect performance. The more rules, the bigger the performance hit. The performance can be helped, however, by combining syscalls into one rule whenever possible.

Solution

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 chown,fchown,fchownat,lchown -F auid>=500 -F auid!=4294967295 -k perm_mod
-a always,exit -F arch=b32 -S chown,fchown,fchownat,lchown -F auid=0 -k perm_mod

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

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

See Also

https://dl.dod.cyber.mil/wp-content/uploads/stigs/zip/U_Oracle_Linux_6_V2R7_STIG.zip

Item Details

Category: AUDIT AND ACCOUNTABILITY

References: 800-53|AU-12c., CAT|III, CCI|CCI-000172, Rule-ID|SV-208894r810468_rule, STIG-ID|OL6-00-000185, STIG-Legacy|SV-65377, STIG-Legacy|V-51167, Vuln-ID|V-208894

Plugin: Unix

Control ID: 175fd683f21d6365eb8536b1866eabe8d4a72c90dd4d4066b8fd6200bb34721e