Successful/unsuccessful uses of postdrop in RHEL 8 must generate an audit record.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-230427	RHEL-08-030311	SV-230427r627750_rule		Medium

Description
Reconstruction of harmful events or forensic analysis is not possible if audit records do not contain enough information. At a minimum, the organization must audit the full-text recording of privileged commands. The organization must maintain audit trails in sufficient detail to reconstruct events to determine the cause and impact of compromise. The "postdrop" command creates a file in the maildrop directory and copies its standard input to the 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. 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

Reconstruction of harmful events or forensic analysis is not possible if audit records do not contain enough information. At a minimum, the organization must audit the full-text recording of privileged commands. The organization must maintain audit trails in sufficient detail to reconstruct events to determine the cause and impact of compromise. The "postdrop" command creates a file in the maildrop directory and copies its standard input to the 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. 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	2021-12-03

Details

Check Text ( C-33096r568027_chk )
Verify that an audit event is generated for any successful/unsuccessful use of "postdrop" by performing the following command to check the file system rules in "/etc/audit/audit.rules": $ sudo grep -w "postdrop" /etc/audit/audit.rules -a always,exit -F path=/usr/sbin/postdrop -F perm=x -F auid>=1000 -F auid!=unset -k privileged-unix-update If the command does not return a line, or the line is commented out, this is a finding.

Check Text ( C-33096r568027_chk )

Verify that an audit event is generated for any successful/unsuccessful use of "postdrop" by performing the following command to check the file system rules in "/etc/audit/audit.rules":

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

-a always,exit -F path=/usr/sbin/postdrop -F perm=x -F auid>=1000 -F auid!=unset -k privileged-unix-update

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

Fix Text (F-33071r568028_fix)
Configure the audit system to generate an audit event for any successful/unsuccessful uses of the "postdrop" by adding or updating the following rule in the "/etc/audit/rules.d/audit.rules" file: -a always,exit -F path=/usr/sbin/postdrop -F perm=x -F auid>=1000 -F auid!=unset -k privileged-unix-update The audit daemon must be restarted for the changes to take effect.