Successful/unsuccessful uses of the unlink command in RHEL 8 must generate an audit record.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-230442	RHEL-08-030364	SV-230442r627750_rule		Medium

Description
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). The "unlink" command deletes a name from the filesystem. If that name was the last link to a file and no processes have the file open, the file is deleted and the space it was using is made available for reuse. 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. Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215

Description

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). The "unlink" command deletes a name from the filesystem. If that name was the last link to a file and no processes have the file open, the file is deleted and the space it was using is made available for reuse. 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. Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215

STIG	Date
Red Hat Enterprise Linux 8 Security Technical Implementation Guide	2021-06-14

Details

Check Text ( C-33111r568072_chk )
Verify RHEL 8 generates an audit record when successful/unsuccessful attempts to use the "unlink" command by performing the following command to check the file system rules in "/etc/audit/audit.rules": $ sudo grep -w "unlink" /etc/audit/audit.rules -a always,exit -F arch=b32 -S unlink -F auid>=1000 -F auid!=unset -k delete -a always,exit -F arch=b64 -S unlink -F auid>=1000 -F auid!=unset -k delete If the command does not return a line, or the line is commented out, this is a finding.

Check Text ( C-33111r568072_chk )

Verify RHEL 8 generates an audit record when successful/unsuccessful attempts to use the "unlink" command by performing the following command to check the file system rules in "/etc/audit/audit.rules":

$ sudo grep -w "unlink" /etc/audit/audit.rules

-a always,exit -F arch=b32 -S unlink -F auid>=1000 -F auid!=unset -k delete
-a always,exit -F arch=b64 -S unlink -F auid>=1000 -F auid!=unset -k delete

If the command does not return a line, or the line is commented out, this is a finding.

Fix Text (F-33086r568073_fix)
Configure the audit system to generate an audit event for any successful/unsuccessful use of the "unlink" command by adding or updating the following rules in the "/etc/audit/rules.d/audit.rules" file: -a always,exit -F arch=b32 -S unlink -F auid>=1000 -F auid!=unset -k delete -a always,exit -F arch=b64 -S unlink -F auid>=1000 -F auid!=unset -k delete The audit daemon must be restarted for the changes to take effect.

Fix Text (F-33086r568073_fix)

Configure the audit system to generate an audit event for any successful/unsuccessful use of the "unlink" command by adding or updating the following rules in the "/etc/audit/rules.d/audit.rules" file:

-a always,exit -F arch=b32 -S unlink -F auid>=1000 -F auid!=unset -k delete
-a always,exit -F arch=b64 -S unlink -F auid>=1000 -F auid!=unset -k delete

The audit daemon must be restarted for the changes to take effect.