Title

Successful/unsuccessful uses of the fremovexattr system call in TOSS must generate an audit record. (Cat II impact)

Discussion

Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one. Audit records can be generated from various components within the information system (e.g., module or policy filter). "Fremovexattr" is a system call that removes extended attributes. This is used for removal of extended attributes from a file. When a user logs on, the AUID is set to the UID of the account that is being authenticated. Daemons are not user sessions and have the loginuid set to "-1." The AUID representation is an unsigned 32-bit integer, which equals "4294967295." The audit system interprets "-1", "4294967295", and "unset" in the same way.

Check Content

Verify if TOSS is configured to audit the execution of the "fremovexattr" system call, by running the following command: $ sudo grep -w fremovexattr /etc/audit/audit.rules -a always,exit -F arch=b32 -S fremovexattr -F auid>=1000 -F auid!=unset -k perm_mod -a always,exit -F arch=b64 -S fremovexattr -F auid>=1000 -F auid!=unset -k perm_mod -a always,exit -F arch=b32 -S fremovexattr -F auid=0 -k perm_mod -a always,exit -F arch=b64 -S fremovexattr -F auid=0 -k perm_mod If the command does not return all lines, or the lines are commented out, this is a finding.

Fix Text

Configure TOSS to audit the execution of the "fremovexattr" system call by adding or updating the following lines to "/etc/audit/rules.d/audit.rules": -a always,exit -F arch=b32 -S fremovexattr -F auid>=1000 -F auid!=unset -k perm_mod -a always,exit -F arch=b64 -S fremovexattr -F auid>=1000 -F auid!=unset -k perm_mod -a always,exit -F arch=b32 -S fremovexattr -F auid=0 -k perm_mod -a always,exit -F arch=b64 -S fremovexattr -F auid=0 -k perm_mod The audit daemon must be restarted for the changes to take effect.

Additional Identifiers

Rule ID: SV-253036r991577_rule

Vulnerability ID: V-253036

Group Title: SRG-OS-000468-GPOS-00212

Expert Comments

CCIs tied to check.

Controls tied to check. These are derived from the CCIs shown above.