The Ubuntu operating system must generate audit records for successful/unsuccessful uses of the chmod, fchmod, and fchmodat system calls.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-238268	UBTU-20-010152	SV-238268r808480_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 system call rules are loaded into a matching engine that intercepts each syscall that all programs on the system makes. Therefore, it is very important to only use syscall rules when absolutely necessary since these affect performance. The more rules, the bigger the performance hit. The performance is helped, though, by combining syscalls into one rule whenever possible. Satisfies: SRG-OS-000064-GPOS-00033, SRG-OS-000462-GPOS-00206

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 system call rules are loaded into a matching engine that intercepts each syscall that all programs on the system makes. Therefore, it is very important to only use syscall rules when absolutely necessary since these affect performance. The more rules, the bigger the performance hit. The performance is helped, though, by combining syscalls into one rule whenever possible. Satisfies: SRG-OS-000064-GPOS-00033, SRG-OS-000462-GPOS-00206

STIG	Date
Canonical Ubuntu 20.04 LTS Security Technical Implementation Guide	2023-09-08

Details

Check Text ( C-41478r808478_chk )
Verify the Ubuntu operating system generates an audit record upon successful/unsuccessful attempts to use the "chmod", "fchmod", and "fchmodat" system calls. Check the configured audit rules with the following commands: $ sudo auditctl -l \| grep chmod -a always,exit -F arch=b32 -S chmod,fchmod,fchmodat -F auid>=1000 -F auid!=-1 -k perm_chng -a always,exit -F arch=b64 -S chmod,fchmod,fchmodat -F auid>=1000 -F auid!=-1 -k perm_chng If the command does not return audit rules for the "chmod", "fchmod" and "fchmodat" syscalls or the lines are commented out, this is a finding. Notes: For 32-bit architectures, only the 32-bit specific output lines from the commands are required. The "-k" allows for specifying an arbitrary identifier, and the string after it does not need to match the example output above.

Check Text ( C-41478r808478_chk )

Verify the Ubuntu operating system generates an audit record upon successful/unsuccessful attempts to use the "chmod", "fchmod", and "fchmodat" system calls.

Check the configured audit rules with the following commands:

$ sudo auditctl -l | grep chmod

-a always,exit -F arch=b32 -S chmod,fchmod,fchmodat -F auid>=1000 -F auid!=-1 -k perm_chng
-a always,exit -F arch=b64 -S chmod,fchmod,fchmodat -F auid>=1000 -F auid!=-1 -k perm_chng

If the command does not return audit rules for the "chmod", "fchmod" and "fchmodat" syscalls or the lines are commented out, this is a finding.

Notes:
For 32-bit architectures, only the 32-bit specific output lines from the commands are required.
The "-k" allows for specifying an arbitrary identifier, and the string after it does not need to match the example output above.

Fix Text (F-41437r808479_fix)
Configure the audit system to generate an audit event for any successful/unsuccessful use of the "chmod", "fchmod", and "fchmodat" system calls. Add or update the following rules in the "/etc/audit/rules.d/stig.rules": -a always,exit -F arch=b32 -S chmod,fchmod,fchmodat -F auid>=1000 -F auid!=4294967295 -k perm_chng -a always,exit -F arch=b64 -S chmod,fchmod,fchmodat -F auid>=1000 -F auid!=4294967295 -k perm_chng Notes: For 32-bit architectures, only the 32-bit specific entries are required. To reload the rules file, issue the following command: $ sudo augenrules --load

Fix Text (F-41437r808479_fix)

Configure the audit system to generate an audit event for any successful/unsuccessful use of the "chmod", "fchmod", and "fchmodat" system calls.

Add or update the following rules in the "/etc/audit/rules.d/stig.rules":

-a always,exit -F arch=b32 -S chmod,fchmod,fchmodat -F auid>=1000 -F auid!=4294967295 -k perm_chng
-a always,exit -F arch=b64 -S chmod,fchmod,fchmodat -F auid>=1000 -F auid!=4294967295 -k perm_chng

Notes: For 32-bit architectures, only the 32-bit specific entries are required.

To reload the rules file, issue the following command:

$ sudo augenrules --load