Protection Profile for General Purpose Operating Systems


CCE ID Rule Title Description Rationale Variable Setting NIST 800-53 Mapping
Limit the Number of Concurrent Login Sessions Allowed Per User Limiting the number of allowed users and sessions per user can limit risks related to Denial of Service attacks. This addresses concurrent sessions for a single account and does not address concurrent sessions by a single user via multiple accounts. To set the number of concurrent sessions per user add the following line in /etc/security/limits.conf or a file under /etc/security/limits.d/:
* hard maxlogins 
Limiting simultaneous user logins can insulate the system from denial of service problems caused by excessive logins. Automated login processes operating improperly or maliciously may result in an exceptional number of simultaneous login sessions. AC-10
CM-6(a)
CCE-84260-9 Ensure the Default Bash Umask is Set Correctly To ensure the default umask for users of the Bash shell is set properly, add or correct the umask setting in /etc/bashrc to read as follows:
umask 
The umask value influences the permissions assigned to files when they are created. A misconfigured umask value could result in files with excessive permissions that can be read or written to by unauthorized users. AC-6(1)
CM-6(a)
CCE-84261-7 Ensure the Default C Shell Umask is Set Correctly To ensure the default umask for users of the C shell is set properly, add or correct the umask setting in /etc/csh.cshrc to read as follows:
umask 
The umask value influences the permissions assigned to files when they are created. A misconfigured umask value could result in files with excessive permissions that can be read or written to by unauthorized users. AC-6(1)
CM-6(a)
CCE-84262-5 Ensure the Default Umask is Set Correctly in /etc/profile To ensure the default umask controlled by /etc/profile is set properly, add or correct the umask setting in /etc/profile to read as follows:
umask 
The umask value influences the permissions assigned to files when they are created. A misconfigured umask value could result in files with excessive permissions that can be read or written to by unauthorized users. AC-6(1)
CM-6(a)
Configure auditing of unsuccessful file accesses Ensure that unsuccessful attempts to access a file are audited. The following rules configure audit as described above:
## Unsuccessful file access (any other opens) This has to go last.
-a always,exit -F arch=b32 -S open,openat,open_by_handle_at -F exit=-EACCES -F auid>=1000 -F auid!=unset -F key=unsuccessful-access
-a always,exit -F arch=b64 -S open,openat,open_by_handle_at -F exit=-EACCES -F auid>=1000 -F auid!=unset -F key=unsuccessful-access
-a always,exit -F arch=b32 -S open,openat,open_by_handle_at -F exit=-EPERM -F auid>=1000 -F auid!=unset -F key=unsuccessful-access
-a always,exit -F arch=b64 -S open,openat,open_by_handle_at -F exit=-EPERM -F auid>=1000 -F auid!=unset -F key=unsuccessful-access    
Load new Audit rules into kernel by running:
augenrules --load
Note: This rule utilizes a file provided by Audit package to comply with OSPP 4.2.1. You may reuse this rule in different profiles. If you decide to do so, it is recommended that you inspect contents of the file closely and make sure that they are alligned with your needs.
Unsuccessful attempts to access a file might be signs of malicious activity happening within the system. Auditing of such activities helps in their monitoring and investigation. AU-2(a)
Configure auditing of successful file accesses Ensure that successful attempts to access a file are audited. The following rules configure audit as described above:
## Successful file access (any other opens) This has to go last.
## These next two are likely to result in a whole lot of events
-a always,exit -F arch=b32 -S open,openat,open_by_handle_at -F success=1 -F auid>=1000 -F auid!=unset -F key=successful-access
-a always,exit -F arch=b64 -S open,openat,open_by_handle_at -F success=1 -F auid>=1000 -F auid!=unset -F key=successful-access    
The Audit package provides pre-configured rules in /usr/share/audit/sample-rules. The above content can be found in /usr/share/audit/sample-rules/30-ospp-v42-3-access-success.rules. To deploy this configuration, it is recommended to copy it over to the /etc/audit/rules.d/ directory:
cp /usr/share/audit/sample-rules/30-ospp-v42-3-access-success.rules /etc/audit/rules.d/
Load new Audit rules into kernel by running:
augenrules --load
Note: This rule utilizes a file provided by Audit package to comply with OSPP 4.2.1. You may reuse this rule in different profiles. If you decide to do so, it is recommended that you inspect contents of the file closely and make sure that they are alligned with your needs.
Auditing of successful attempts to access a file helps in investigation of activities performed on the system. AU-2(a)
Configure basic parameters of Audit system Perform basic configuration of Audit system. Make sure that any previously defined rules are cleared, the auditing system is configured to handle sudden bursts of events, and in cases of failure, messages are configured to be directed to system log. The following rules configure audit as described above:
## First rule - delete all
-D

## Increase the buffers to survive stress events.
## Make this bigger for busy systems
-b 8192

## This determine how long to wait in burst of events
--backlog_wait_time 60000

## Set failure mode to syslog
-f 1
    
The Audit package provides pre-configured rules in /usr/share/audit/sample-rules. The above content can be found in /usr/share/audit/sample-rules/10-base-config.rules. To deploy this configuration, it is recommended to copy it over to the /etc/audit/rules.d/ directory:
cp /usr/share/audit/sample-rules/10-base-config.rules /etc/audit/rules.d/
Load new Audit rules into kernel by running:
augenrules --load
Without basic configurations, audit may not perform as expected. It may not be able to correctly handle events under stressful conditions, or log events in case of failure. AU-2(a)
Configure auditing of unsuccessful file creations Ensure that unsuccessful attempts to create a file are audited. The following rules configure audit as described above:
## Unsuccessful file creation (open with O_CREAT)
-a always,exit -F arch=b32 -S openat,open_by_handle_at -F a2&0100 -F exit=-EACCES -F auid>=1000 -F auid!=unset -F key=unsuccessful-create
-a always,exit -F arch=b64 -S openat,open_by_handle_at -F a2&0100 -F exit=-EACCES -F auid>=1000 -F auid!=unset -F key=unsuccessful-create
-a always,exit -F arch=b32 -S open -F a1&0100 -F exit=-EACCES -F auid>=1000 -F auid!=unset -F key=unsuccessful-create
-a always,exit -F arch=b64 -S open -F a1&0100 -F exit=-EACCES -F auid>=1000 -F auid!=unset -F key=unsuccessful-create
-a always,exit -F arch=b32 -S creat -F exit=-EACCES -F auid>=1000 -F auid!=unset -F key=unsuccessful-create
-a always,exit -F arch=b64 -S creat -F exit=-EACCES -F auid>=1000 -F auid!=unset -F key=unsuccessful-create
-a always,exit -F arch=b32 -S openat,open_by_handle_at -F a2&0100 -F exit=-EPERM -F auid>=1000 -F auid!=unset -F key=unsuccessful-create
-a always,exit -F arch=b64 -S openat,open_by_handle_at -F a2&0100 -F exit=-EPERM -F auid>=1000 -F auid!=unset -F key=unsuccessful-create
-a always,exit -F arch=b32 -S open -F a1&0100 -F exit=-EPERM -F auid>=1000 -F auid!=unset -F key=unsuccessful-create
-a always,exit -F arch=b64 -S open -F a1&0100 -F exit=-EPERM -F auid>=1000 -F auid!=unset -F key=unsuccessful-create
-a always,exit -F arch=b32 -S creat -F exit=-EPERM -F auid>=1000 -F auid!=unset -F key=unsuccessful-create
-a always,exit -F arch=b64 -S creat -F exit=-EPERM -F auid>=1000 -F auid!=unset -F key=unsuccessful-create    
The Audit package provides pre-configured rules in /usr/share/audit/sample-rules. The above content can be found in /usr/share/audit/sample-rules/30-ospp-v42-1-create-failed.rules. To deploy this configuration, it is recommended to copy it over to the /etc/audit/rules.d/ directory:
cp /usr/share/audit/sample-rules/30-ospp-v42-1-create-failed.rules /etc/audit/rules.d/
Load new Audit rules into kernel by running:
augenrules --load
Note: This rule utilizes a file provided by Audit package to comply with OSPP 4.2.1. You may reuse this rule in different profiles. If you decide to do so, it is recommended that you inspect contents of the file closely and make sure that they are alligned with your needs.
Unsuccessful file creations might be a sign of a malicious action being performed on the system. Keeping log of such events helps in monitoring and investigation of such actions. AU-2(a)
Configure auditing of successful file creations Ensure that successful attempts to create a file are audited. The following rules configure audit as described above:
## Successful file creation (open with O_CREAT)
-a always,exit -F arch=b32 -S openat,open_by_handle_at -F a2&0100 -F success=1 -F auid>=1000 -F auid!=unset -F key=successful-create
-a always,exit -F arch=b64 -S openat,open_by_handle_at -F a2&0100 -F success=1 -F auid>=1000 -F auid!=unset -F key=successful-create
-a always,exit -F arch=b32 -S open -F a1&0100 -F success=1 -F auid>=1000 -F auid!=unset -F key=successful-create
-a always,exit -F arch=b64 -S open -F a1&0100 -F success=1 -F auid>=1000 -F auid!=unset -F key=successful-create
-a always,exit -F arch=b32 -S creat -F success=1 -F auid>=1000 -F auid!=unset -F key=successful-create
-a always,exit -F arch=b64 -S creat -F success=1 -F auid>=1000 -F auid!=unset -F key=successful-create    
The Audit package provides pre-configured rules in /usr/share/audit/sample-rules. The above content can be found in /usr/share/audit/sample-rules/30-ospp-v42-1-create-success.rules. To deploy this configuration, it is recommended to copy it over to the /etc/audit/rules.d/ directory:
cp /usr/share/audit/sample-rules/30-ospp-v42-1-create-success.rules /etc/audit/rules.d/
Load new Audit rules into kernel by running:
augenrules --load
Auditing of successful attempts to create a file helps in investigation of actions which happened on the system. AU-2(a)
Configure auditing of unsuccessful file deletions Ensure that unsuccessful attempts to delete a file are audited. The following rules configure audit as described above:
## Unsuccessful file delete
-a always,exit -F arch=b32 -S unlink,unlinkat,rename,renameat -F exit=-EACCES -F auid>=1000 -F auid!=unset -F key=unsuccessful-delete
-a always,exit -F arch=b64 -S unlink,unlinkat,rename,renameat -F exit=-EACCES -F auid>=1000 -F auid!=unset -F key=unsuccessful-delete
-a always,exit -F arch=b32 -S unlink,unlinkat,rename,renameat -F exit=-EPERM -F auid>=1000 -F auid!=unset -F key=unsuccessful-delete
-a always,exit -F arch=b64 -S unlink,unlinkat,rename,renameat -F exit=-EPERM -F auid>=1000 -F auid!=unset -F key=unsuccessful-delete    
The Audit package provides pre-configured rules in /usr/share/audit/sample-rules. The above content can be found in /usr/share/audit/sample-rules/30-ospp-v42-4-delete-failed.rules. To deploy this configuration, it is recommended to copy it over to the /etc/audit/rules.d/ directory:
cp /usr/share/audit/sample-rules/30-ospp-v42-4-delete-failed.rules /etc/audit/rules.d/
Load new Audit rules into kernel by running:
augenrules --load
Note: This rule utilizes a file provided by Audit package to comply with OSPP 4.2.1. You may reuse this rule in different profiles. If you decide to do so, it is recommended that you inspect contents of the file closely and make sure that they are alligned with your needs.
Unsuccessful attempts to delete a file might be signs of malicious activities. Auditing of such events help in monitoring and investigating of such activities. AU-2(a)
Configure auditing of successful file deletions Ensure that successful attempts to delete a file are audited. The following rules configure audit as described above:
## Successful file delete
-a always,exit -F arch=b32 -S unlink,unlinkat,rename,renameat -F success=1 -F auid>=1000 -F auid!=unset -F key=successful-delete
-a always,exit -F arch=b64 -S unlink,unlinkat,rename,renameat -F success=1 -F auid>=1000 -F auid!=unset -F key=successful-delete    
The Audit package provides pre-configured rules in /usr/share/audit/sample-rules. The above content can be found in /usr/share/audit/sample-rules/30-ospp-v42-4-delete-success.rules. To deploy this configuration, it is recommended to copy it over to the /etc/audit/rules.d/ directory:
cp /usr/share/audit/sample-rules/30-ospp-v42-4-delete-success.rules /etc/audit/rules.d/
Load new Audit rules into kernel by running:
augenrules --load
Note: This rule utilizes a file provided by Audit package to comply with OSPP 4.2.1. You may reuse this rule in different profiles. If you decide to do so, it is recommended that you inspect contents of the file closely and make sure that they are alligned with your needs.
Auditing of successful attempts to delete a file may help in monitoring and investigation of activities performed on the system. AU-2(a)
Configure immutable Audit login UIDs Configure kernel to prevent modification of login UIDs once they are set. Changing login UUIDs while this configuration is enforced requires special capabilities which are not available to unprivileged users. The following rules configure audit as described above:
## Make the loginuid immutable. This prevents tampering with the auid.
--loginuid-immutable
    
The Audit provides pre-configured rules in /usr/share/audit/sample-rules. The above content can be found in /usr/share/audit/sample-rules/11-loginuid.rules. To deploy this configuration, it is recommended to copy it over to the /etc/audit/rules.d/ directory:
cp /usr/share/audit/sample-rules/11-loginuid.rules /etc/audit/rules.d/
Load new Audit rules into kernel by running:
augenrules --load
If modification of login UIDs is not prevented, they can be changed by unprivileged users and make auditing complicated or impossible. AU-2(a)
Configure auditing of unsuccessful file modifications Ensure that unsuccessful attempts to modify a file are audited. The following rules configure audit as described above:
## Unsuccessful file modifications (open for write or truncate)
-a always,exit -F arch=b32 -S openat,open_by_handle_at -F a2&01003 -F exit=-EACCES -F auid>=1000 -F auid!=unset -F key=unsuccessful-modification
-a always,exit -F arch=b64 -S openat,open_by_handle_at -F a2&01003 -F exit=-EACCES -F auid>=1000 -F auid!=unset -F key=unsuccessful-modification
-a always,exit -F arch=b32 -S open -F a1&01003 -F exit=-EACCES -F auid>=1000 -F auid!=unset -F key=unsuccessful-modification
-a always,exit -F arch=b64 -S open -F a1&01003 -F exit=-EACCES -F auid>=1000 -F auid!=unset -F key=unsuccessful-modification
-a always,exit -F arch=b32 -S truncate,ftruncate -F exit=-EACCES -F auid>=1000 -F auid!=unset -F key=unsuccessful-modification
-a always,exit -F arch=b64 -S truncate,ftruncate -F exit=-EACCES -F auid>=1000 -F auid!=unset -F key=unsuccessful-modification
-a always,exit -F arch=b32 -S openat,open_by_handle_at -F a2&01003 -F exit=-EPERM -F auid>=1000 -F auid!=unset -F key=unsuccessful-modification
-a always,exit -F arch=b64 -S openat,open_by_handle_at -F a2&01003 -F exit=-EPERM -F auid>=1000 -F auid!=unset -F key=unsuccessful-modification
-a always,exit -F arch=b32 -S open -F a1&01003 -F exit=-EPERM -F auid>=1000 -F auid!=unset -F key=unsuccessful-modification
-a always,exit -F arch=b64 -S open -F a1&01003 -F exit=-EPERM -F auid>=1000 -F auid!=unset -F key=unsuccessful-modification
-a always,exit -F arch=b32 -S truncate,ftruncate -F exit=-EPERM -F auid>=1000 -F auid!=unset -F key=unsuccessful-modification
-a always,exit -F arch=b64 -S truncate,ftruncate -F exit=-EPERM -F auid>=1000 -F auid!=unset -F key=unsuccessful-modification    
The Audit package provides pre-configured rules in /usr/share/audit/sample-rules. The above content can be found in /usr/share/audit/sample-rules/30-ospp-v42-2-modify-failed.rules. To deploy this configuration, it is recommended to copy it over to the /etc/audit/rules.d/ directory:
cp /usr/share/audit/sample-rules/30-ospp-v42-2-modify-failed.rules /etc/audit/rules.d/
Load new Audit rules into kernel by running:
augenrules --load
Note: This rule utilizes a file provided by Audit package to comply with OSPP 4.2.1. You may reuse this rule in different profiles. If you decide to do so, it is recommended that you inspect contents of the file closely and make sure that they are alligned with your needs.
Unsuccessful file modifications might be a sign of a malicious action being performed on the system. Auditing of such events helps in detection and investigation of such actions. AU-2(a)
Configure auditing of successful file modifications Ensure that successful attempts to modify a file are audited. The following rules configure audit as described above:
## Successful file modifications (open for write or truncate)
-a always,exit -F arch=b32 -S openat,open_by_handle_at -F a2&01003 -F success=1 -F auid>=1000 -F auid!=unset -F key=successful-modification
-a always,exit -F arch=b64 -S openat,open_by_handle_at -F a2&01003 -F success=1 -F auid>=1000 -F auid!=unset -F key=successful-modification
-a always,exit -F arch=b32 -S open -F a1&01003 -F success=1 -F auid>=1000 -F auid!=unset -F key=successful-modification
-a always,exit -F arch=b64 -S open -F a1&01003 -F success=1 -F auid>=1000 -F auid!=unset -F key=successful-modification
-a always,exit -F arch=b32 -S truncate,ftruncate -F success=1 -F auid>=1000 -F auid!=unset -F key=successful-modification
-a always,exit -F arch=b64 -S truncate,ftruncate -F success=1 -F auid>=1000 -F auid!=unset -F key=successful-modification    
The Audit package provides pre-configured rules in /usr/share/audit/sample-rules. The above content can be found in /usr/share/audit/sample-rules/30-ospp-v42-2-modify-success.rules. To deploy this configuration, it is recommended to copy it over to the /etc/audit/rules.d/ directory:
cp /usr/share/audit/sample-rules/30-ospp-v42-2-modify-success.rules /etc/audit/rules.d/
Load new Audit rules into kernel by running:
augenrules --load
Note: This rule utilizes a file provided by Audit package to comply with OSPP 4.2.1. You may reuse this rule in different profiles. If you decide to do so, it is recommended that you inspect contents of the file closely and make sure that they are alligned with your needs.
Auditing of successful attempts to modify a file helps in investigation of actions which happened on the system. AU-2(a)
Configure auditing of loading and unloading of kernel modules Ensure that loading and unloading of kernel modules is audited. The following rules configure audit as described above:
## These rules watch for kernel module insertion. By monitoring
## the syscall, we do not need any watches on programs.
-a always,exit -F arch=b32 -S init_module,finit_module -F key=module-load
-a always,exit -F arch=b64 -S init_module,finit_module -F key=module-load
-a always,exit -F arch=b32 -S delete_module -F key=module-unload
-a always,exit -F arch=b64 -S delete_module -F key=module-unload    
The Audit package provides pre-configured rules in /usr/share/audit/sample-rules. The above content can be found in /usr/share/audit/sample-rules/43-module-load.rules. To deploy this configuration, it is recommended to copy it over to the /etc/audit/rules.d/ directory:
cp /usr/share/audit/sample-rules/43-module-load.rules /etc/audit/rules.d/
Load new Audit rules into kernel by running:
augenrules --load
Loading of a malicious kernel module introduces a risk to the system, as the module has access to sensitive data and perform actions at the operating system kernel level. Having such events audited helps in monitoring and investigating of malicious activities. AU-2(a)
Perform general configuration of Audit for OSPP Configure some basic Audit parameters specific for OSPP profile. In particular, configure Audit to watch for direct modification of files storing system user and group information, and usage of applications with special rights which can change system configuration. Further audited events include access to audit log it self, attempts to Alter Process and Session Initiation Information, and attempts to modify MAC controls. The following rules configure audit as described above:
## The purpose of these rules is to meet the requirements for Operating
## System Protection Profile (OSPP)v4.2. These rules depends on having
## the following rule files copied to /etc/audit/rules.d:
##
## 10-base-config.rules, 11-loginuid.rules,
## 30-ospp-v42-1-create-failed.rules, 30-ospp-v42-1-create-success.rules,
## 30-ospp-v42-2-modify-failed.rules, 30-ospp-v42-2-modify-success.rules,
## 30-ospp-v42-3-access-failed.rules, 30-ospp-v42-3-access-success.rules,
## 30-ospp-v42-4-delete-failed.rules, 30-ospp-v42-4-delete-success.rules,
## 30-ospp-v42-5-perm-change-failed.rules,
## 30-ospp-v42-5-perm-change-success.rules,
## 30-ospp-v42-6-owner-change-failed.rules,
## 30-ospp-v42-6-owner-change-success.rules
##
## original copies may be found in /usr/share/audit/sample-rules/


## User add delete modify. This is covered by pam. However, someone could
## open a file and directly create or modify a user, so we'll watch passwd and
## shadow for writes
-a always,exit -F arch=b32 -S openat,open_by_handle_at -F a2&03 -F path=/etc/passwd -F auid>=1000 -F auid!=unset -F key=user-modify
-a always,exit -F arch=b64 -S openat,open_by_handle_at -F a2&03 -F path=/etc/passwd -F auid>=1000 -F auid!=unset -F key=user-modify
-a always,exit -F arch=b32 -S open -F a1&03 -F path=/etc/passwd -F auid>=1000 -F auid!=unset -F key=user-modify
-a always,exit -F arch=b64 -S open -F a1&03 -F path=/etc/passwd -F auid>=1000 -F auid!=unset -F key=user-modify
-a always,exit -F arch=b32 -S openat,open_by_handle_at -F a2&03 -F path=/etc/shadow -F auid>=1000 -F auid!=unset -F key=user-modify
-a always,exit -F arch=b64 -S openat,open_by_handle_at -F a2&03 -F path=/etc/shadow -F auid>=1000 -F auid!=unset -F key=user-modify
-a always,exit -F arch=b32 -S open -F a1&03 -F path=/etc/shadow -F auid>=1000 -F auid!=unset -F key=user-modify
-a always,exit -F arch=b64 -S open -F a1&03 -F path=/etc/shadow -F auid>=1000 -F auid!=unset -F key=user-modify

## User enable and disable. This is entirely handled by pam.

## Group add delete modify. This is covered by pam. However, someone could
## open a file and directly create or modify a user, so we'll watch group and
## gshadow for writes
-a always,exit -F path=/etc/passwd -F perm=wa -F auid>=1000 -F auid!=unset -F key=user-modify
-a always,exit -F path=/etc/shadow -F perm=wa -F auid>=1000 -F auid!=unset -F key=user-modify
-a always,exit -F path=/etc/group -F perm=wa -F auid>=1000 -F auid!=unset -F key=group-modify
-a always,exit -F path=/etc/gshadow -F perm=wa -F auid>=1000 -F auid!=unset -F key=group-modify


## Use of special rights for config changes. This would be use of setuid
## programs that relate to user accts. This is not all setuid apps because
## requirements are only for ones that affect system configuration.
-a always,exit -F path=/usr/sbin/unix_chkpwd -F perm=x -F auid>=1000 -F auid!=unset -F key=special-config-changes
-a always,exit -F path=/usr/sbin/usernetctl -F perm=x -F auid>=1000 -F auid!=unset -F key=special-config-changes
-a always,exit -F path=/usr/sbin/userhelper -F perm=x -F auid>=1000 -F auid!=unset -F key=special-config-changes
-a always,exit -F path=/usr/sbin/seunshare -F perm=x -F auid>=1000 -F auid!=unset -F key=special-config-changes
-a always,exit -F path=/usr/bin/mount -F perm=x -F auid>=1000 -F auid!=unset -F key=special-config-changes
-a always,exit -F path=/usr/bin/newgrp -F perm=x -F auid>=1000 -F auid!=unset -F key=special-config-changes
-a always,exit -F path=/usr/bin/newuidmap -F perm=x -F auid>=1000 -F auid!=unset -F key=special-config-changes
-a always,exit -F path=/usr/bin/gpasswd -F perm=x -F auid>=1000 -F auid!=unset -F key=special-config-changes
-a always,exit -F path=/usr/bin/newgidmap -F perm=x -F auid>=1000 -F auid!=unset -F key=special-config-changes
-a always,exit -F path=/usr/bin/umount -F perm=x -F auid>=1000 -F auid!=unset -F key=special-config-changes
-a always,exit -F path=/usr/bin/passwd -F perm=x -F auid>=1000 -F auid!=unset -F key=special-config-changes
-a always,exit -F path=/usr/bin/crontab -F perm=x -F auid>=1000 -F auid!=unset -F key=special-config-changes
-a always,exit -F path=/usr/bin/at -F perm=x -F auid>=1000 -F auid!=unset -F key=special-config-changes

## Privilege escalation via su or sudo. This is entirely handled by pam.

## Audit log access
-a always,exit -F dir=/var/log/audit/ -F perm=r -F auid>=1000 -F auid!=unset -F key=access-audit-trail
## Attempts to Alter Process and Session Initiation Information
-a always,exit -F path=/var/run/utmp -F perm=wa -F auid>=1000 -F auid!=unset -F key=session
-a always,exit -F path=/var/log/btmp -F perm=wa -F auid>=1000 -F auid!=unset -F key=session
-a always,exit -F path=/var/log/wtmp -F perm=wa -F auid>=1000 -F auid!=unset -F key=session

## Attempts to modify MAC controls
-a always,exit -F dir=/etc/selinux/ -F perm=wa -F auid>=1000 -F auid!=unset -F key=MAC-policy

## Software updates. This is entirely handled by rpm.

## System start and shutdown. This is entirely handled by systemd

## Kernel Module loading. This is handled in 43-module-load.rules

## Application invocation. The requirements list an optional requirement
## FPT_SRP_EXT.1 Software Restriction Policies. This event is intended to
## state results from that policy. This would be handled entirely by
## that daemon.
    
The Audit package provides pre-configured rules in /usr/share/audit/sample-rules. The above content can be found in /usr/share/audit/sample-rules/30-ospp-v42.rules. To deploy this configuration, it is recommended to copy it over to the /etc/audit/rules.d/ directory:
cp /usr/share/audit/sample-rules/30-ospp-v42.rules /etc/audit/rules.d/
Load new Audit rules into kernel by running:
augenrules --load
Note: This rule utilizes a file provided by Audit package to comply with OSPP 4.2.1. You may reuse this rule in different profiles. If you decide to do so, it is recommended that you inspect contents of the file closely and make sure that they are alligned with your needs.
Auditing of events listed in the description provides data for monitoring and investigation of potentially malicious events e.g. tampering with Audit logs, malicious access to files storing information about system users and groups etc. AU-2(a)
Configure auditing of unsuccessful ownership changes Ensure that unsuccessful attempts to change an ownership of files or directories are audited. The following rules configure audit as described above:
## Unsuccessful ownership change
-a always,exit -F arch=b32 -S lchown,fchown,chown,fchownat -F exit=-EACCES -F auid>=1000 -F auid!=unset -F key=unsuccessful-owner-change
-a always,exit -F arch=b64 -S lchown,fchown,chown,fchownat -F exit=-EACCES -F auid>=1000 -F auid!=unset -F key=unsuccessful-owner-change
-a always,exit -F arch=b32 -S lchown,fchown,chown,fchownat -F exit=-EPERM -F auid>=1000 -F auid!=unset -F key=unsuccessful-owner-change
-a always,exit -F arch=b64 -S lchown,fchown,chown,fchownat -F exit=-EPERM -F auid>=1000 -F auid!=unset -F key=unsuccessful-owner-change    
The Audit package provides pre-configured rules in /usr/share/audit/sample-rules. The above content can be found in /usr/share/audit/sample-rules/30-ospp-v42-6-owner-change-failed.rules. To deploy this configuration, it is recommended to copy it over to the /etc/audit/rules.d/ directory:
cp /usr/share/audit/sample-rules/30-ospp-v42-6-owner-change-failed.rules /etc/audit/rules.d/
Load new Audit rules into kernel by running:
augenrules --load
Note: This rule utilizes a file provided by Audit package to comply with OSPP 4.2.1. You may reuse this rule in different profiles. If you decide to do so, it is recommended that you inspect contents of the file closely and make sure that they are alligned with your needs.
Unsuccessful attempts to change an ownership of files or directories might be signs of a malicious activity. Having such events audited helps in monitoring and investigation of such activities. AU-2(a)
Configure auditing of successful ownership changes Ensure that successful attempts to change an ownership of files or directories are audited. The following rules configure audit as described above:
## Successful ownership change
-a always,exit -F arch=b32 -S lchown,fchown,chown,fchownat -F success=1 -F auid>=1000 -F auid!=unset -F key=successful-owner-change
-a always,exit -F arch=b64 -S lchown,fchown,chown,fchownat -F success=1 -F auid>=1000 -F auid!=unset -F key=successful-owner-change    
The Audit package provides pre-configured rules in /usr/share/audit/sample-rules. The above content can be found in /usr/share/audit/sample-rules/30-ospp-v42-6-owner-change-success.rules. To deploy this configuration, it is recommended to copy it over to the /etc/audit/rules.d/ directory:
cp /usr/share/audit/sample-rules/30-ospp-v42-6-owner-change-success.rules /etc/audit/rules.d/
The file has the following SHA-256 checksum:
7eb41a6aaf6737c2571b6424fae7fa53af4b41a9115b6c5732a5778ccd9900ad
Load new Audit rules into kernel by running:
augenrules --load
Note: This rule utilizes a file provided by Audit package to comply with OSPP 4.2.1. You may reuse this rule in different profiles. If you decide to do so, it is recommended that you inspect contents of the file closely and make sure that they are alligned with your needs.
Auditing of successful ownership changes of files or directories helps in monitoring or investingating of activities performed on the system. AU-2(a)
Configure auditing of unsuccessful permission changes Ensure that unsuccessful attempts to change file or directory permissions are audited. The following rules configure audit as described above:
## Unsuccessful permission change
-a always,exit -F arch=b32 -S chmod,fchmod,fchmodat,setxattr,lsetxattr,fsetxattr,removexattr,lremovexattr,fremovexattr -F exit=-EACCES -F auid>=1000 -F auid!=unset -F key=unsuccessful-perm-change
-a always,exit -F arch=b64 -S chmod,fchmod,fchmodat,setxattr,lsetxattr,fsetxattr,removexattr,lremovexattr,fremovexattr -F exit=-EACCES -F auid>=1000 -F auid!=unset -F key=unsuccessful-perm-change
-a always,exit -F arch=b32 -S chmod,fchmod,fchmodat,setxattr,lsetxattr,fsetxattr,removexattr,lremovexattr,fremovexattr -F exit=-EPERM -F auid>=1000 -F auid!=unset -F key=unsuccessful-perm-change
-a always,exit -F arch=b64 -S chmod,fchmod,fchmodat,setxattr,lsetxattr,fsetxattr,removexattr,lremovexattr,fremovexattr -F exit=-EPERM -F auid>=1000 -F auid!=unset -F key=unsuccessful-perm-change    
The Audit package provides pre-configured rules in /usr/share/audit/sample-rules. The above content can be found in /usr/share/audit/sample-rules/30-ospp-v42-5-perm-change-failed.rules. To deploy this configuration, it is recommended to copy it over to the /etc/audit/rules.d/ directory:
cp /usr/share/audit/sample-rules/30-ospp-v42-5-perm-change-failed.rules /etc/audit/rules.d/
Load new Audit rules into kernel by running:
augenrules --load
Note: This rule utilizes a file provided by Audit package to comply with OSPP 4.2.1. You may reuse this rule in different profiles. If you decide to do so, it is recommended that you inspect contents of the file closely and make sure that they are alligned with your needs.
Unsuccessful attempts to change permissions of files or directories might be signs of malicious activity. Having such events audited helps in monitoring and investigation of such activities. AU-2(a)
Configure auditing of successful permission changes Ensure that successful attempts to modify permissions of iles or directories are audited. The following rules configure audit as described above:
## Successful permission change
-a always,exit -F arch=b32 -S chmod,fchmod,fchmodat,setxattr,lsetxattr,fsetxattr,removexattr,lremovexattr,fremovexattr -F success=1 -F auid>=1000 -F auid!=unset -F key=successful-perm-change
-a always,exit -F arch=b64 -S chmod,fchmod,fchmodat,setxattr,lsetxattr,fsetxattr,removexattr,lremovexattr,fremovexattr -F success=1 -F auid>=1000 -F auid!=unset -F key=successful-perm-change    
The Audit package provides pre-configured rules in /usr/share/audit/sample-rules. The above content can be found in /usr/share/audit/sample-rules/30-ospp-v42-5-perm-change-success.rules. To deploy this configuration, it is recommended to copy it over to the /etc/audit/rules.d/ directory:
cp /usr/share/audit/sample-rules/30-ospp-v42-5-perm-change-success.rules /etc/audit/rules.d/
Load new Audit rules into kernel by running:
augenrules --load
Note: This rule utilizes a file provided by Audit package to comply with OSPP 4.2.1. You may reuse this rule in different profiles. If you decide to do so, it is recommended that you inspect contents of the file closely and make sure that they are alligned with your needs.
Auditing successful file or directory permission changes helps in monitoring and investigating of activities performed on the system. AU-2(a)
CCE-82508-3 Configure auditd flush priority The auditd service can be configured to synchronously write audit event data to disk. Add or correct the following line in /etc/audit/auditd.conf to ensure that audit event data is fully synchronized with the log files on the disk:
flush = 
Audit data should be synchronously written to disk to ensure log integrity. These parameters assure that all audit event data is fully synchronized with the log files on the disk. AU-11
CM-6(a)
CCE-82512-5 Set number of records to cause an explicit flush to audit logs To configure Audit daemon to issue an explicit flush to disk command after writing 50 records, set freq to 50 in /etc/audit/auditd.conf. If option freq isn't set to 50, the flush to disk may happen after higher number of records, increasing the danger of audit loss.
CCE-82509-1 Include Local Events in Audit Logs To configure Audit daemon to include local events in Audit logs, set local_events to yes in /etc/audit/auditd.conf. This is the default setting. If option local_events isn't set to yes only events from network will be aggregated.
CCE-82511-7 Resolve information before writing to audit logs To configure Audit daemon to resolve all uid, gid, syscall, architecture, and socket address information before writing the events to disk, set log_format to ENRICHED in /etc/audit/auditd.conf. If option log_format isn't set to ENRICHED, the audit records will be stored in a format exactly as the kernel sends them.
CCE-82513-3 Set hostname as computer node name in audit logs To configure Audit daemon to use value returned by gethostname syscall as computer node name in the audit events, set name_format to hostname in /etc/audit/auditd.conf. If option name_format is left at its default value of none, audit events from different computers may be hard to distinguish.
CCE-82510-9 Write Audit Logs to the Disk To configure Audit daemon to write Audit logs to the disk, set write_logs to yes in /etc/audit/auditd.conf. This is the default setting. If write_logs isn't set to yes, the Audit logs will not be written to the disk.
CCE-82465-6 Disable chrony daemon from acting as server The port option in /etc/chrony.conf can be set to 0 to make chrony daemon to never open any listening port for server operation and to operate strictly in a client-only mode. Minimizing the exposure of the server functionality of the chrony daemon diminishes the attack surface.
CCE-82466-4 Disable network management of chrony daemon The cmdport option in /etc/chrony.conf can be set to 0 to stop chrony daemon from listening on the UDP port 323 for management connections made by chronyc. Not exposing the management interface of the chrony daemon on the network diminishes the attack space.
Support session locking with tmux The tmux terminal multiplexer is used to implement automatic session locking. It should be started from /etc/bashrc. Unlike bash itself, the tmux terminal multiplexer provides a mechanism to lock sessions after period of inactivity.
CCE-82541-4 Configure System Cryptography Policy To configure the system cryptography policy to use ciphers only from the policy, run the following command:
$ sudo update-crypto-policies --set 
The rule checks if settings for selected crypto policy are configured as expected. Configuration files in the /etc/crypto-policies/back-ends are either symlinks to correct files provided by Crypto-policies package or they are regular files in case crypto policy customizations are applied. Crypto policies may be customized by crypto policy modules, in which case it is delimited from the base policy using a colon.
Centralized cryptographic policies simplify applying secure ciphers across an operating system and the applications that run on that operating system. Use of weak or untested encryption algorithms undermines the purposes of utilizing encryption to protect data. AC-17(a)
AC-17(2)
CM-6(a)
MA-4(6)
SC-13
SC-12(2)
SC-12(3)
CCE-82547-1 Configure Kerberos to use System Crypto Policy Crypto Policies provide a centralized control over crypto algorithms usage of many packages. Kerberos is supported by crypto policy, but it's configuration may be set up to ignore it. To check that Crypto Policies settings for Kerberos are configured correctly, examine that there is a symlink at /etc/krb5.conf.d/crypto-policies targeting /etc/cypto-policies/back-ends/krb5.config. If the symlink exists, kerberos is configured to use the system-wide crypto policy settings. Overriding the system crypto policy makes the behavior of Kerberos violate expectations, and makes system configuration more fragmented. SC-13
SC-12(2)
SC-12(3)
CCE-82546-3 Configure Libreswan to use System Crypto Policy Crypto Policies provide a centralized control over crypto algorithms usage of many packages. Libreswan is supported by system crypto policy, but the Libreswan configuration may be set up to ignore it. To check that Crypto Policies settings are configured correctly, ensure that the /etc/ipsec.conf includes the appropriate configuration file. In /etc/ipsec.conf, make sure that the following line is not commented out or superseded by later includes: include /etc/crypto-policies/back-ends/libreswan.config Overriding the system crypto policy makes the behavior of the Libreswan service violate expectations, and makes system configuration more fragmented. CM-6(a)
MA-4(6)
SC-13
SC-12(2)
SC-12(3)
CCE-82545-5 Configure OpenSSL library to use System Crypto Policy Crypto Policies provide a centralized control over crypto algorithms usage of many packages. OpenSSL is supported by crypto policy, but the OpenSSL configuration may be set up to ignore it. To check that Crypto Policies settings are configured correctly, you have to examine the OpenSSL config file available under /etc/pki/tls/openssl.cnf. This file has the ini format, and it enables crypto policy support if there is a [ crypto_policy ] section that contains the .include /etc/crypto-policies/back-ends/opensslcnf.config directive. Overriding the system crypto policy makes the behavior of the Java runtime violates expectations, and makes system configuration more fragmented. AC-17(a)
AC-17(2)
CM-6(a)
MA-4(6)
SC-13
SC-12(2)
SC-12(3)
Configure SSH to use System Crypto Policy Crypto Policies provide a centralized control over crypto algorithms usage of many packages. SSH is supported by crypto policy, but the SSH configuration may be set up to ignore it. To check that Crypto Policies settings are configured correctly, ensure that the CRYPTO_POLICY variable is either commented or not set at all in the /etc/sysconfig/sshd. Overriding the system crypto policy makes the behavior of the SSH service violate expectations, and makes system configuration more fragmented. AC-17(a)
AC-17(2)
CM-6(a)
MA-4(6)
SC-13
Configure tmux to lock session after inactivity To enable console screen locking in tmux terminal multiplexer after a period of inactivity, the lock-after-time option has to be set to nonzero value in /etc/tmux.conf. Locking the session after a period of inactivity limits the potential exposure if the session is left unattended.
Configure the tmux Lock Command To enable console screen locking in tmux terminal multiplexer, the vlock command must be configured to be used as a locking mechanism. Add the following line to /etc/tmux.conf:
set -g lock-command vlock
. The console can now be locked with the following key combination:
ctrl+b :lock-session
The tmux package allows for a session lock to be implemented and configured. However, the session lock is implemented by an external command. The tmux default configuration does not contain an effective session lock. AC-11(a)
AC-11(b)
CM-6(a)
CCE-82538-0 Log USBGuard daemon audit events using Linux Audit To configure USBGuard daemon to log via Linux Audit (as opposed directly to a file), AuditBackend option in /etc/usbguard/usbguard-daemon.conf needs to be set to LinuxAudit. Using the Linux Audit logging allows for centralized trace of events.
CCE-82529-9 Disable core dump backtraces The ProcessSizeMax option in [Coredump] section of /etc/systemd/coredump.conf specifies the maximum size in bytes of a core which will be processed. Core dumps exceeding this size may be stored, but the backtrace will not be generated. A core dump includes a memory image taken at the time the operating system terminates an application. The memory image could contain sensitive data and is generally useful only for developers or system operators trying to debug problems. Enabling core dumps on production systems is not recommended, however there may be overriding operational requirements to enable advanced debuging. Permitting temporary enablement of core dumps during such situations should be reviewed through local needs and policy.
CCE-82528-1 Disable storing core dump The Storage option in [Coredump] section of /etc/systemd/coredump.conf can be set to none to disable storing core dumps permanently. A core dump includes a memory image taken at the time the operating system terminates an application. The memory image could contain sensitive data and is generally useful only for developers or system operators trying to debug problems. Enabling core dumps on production systems is not recommended, however there may be overriding operational requirements to enable advanced debuging. Permitting temporary enablement of core dumps during such situations should be reviewed through local needs and policy.
CCE-82671-9 Extend Audit Backlog Limit for the Audit Daemon To improve the kernel capacity to queue all log events, even those which occurred prior to the audit daemon, add the argument audit_backlog_limit=8192 to all BLS (Boot Loader Specification) entries ('options' line) for the Linux operating system in /boot/loader/entries/*.conf. audit_backlog_limit sets the queue length for audit events awaiting transfer to the audit daemon. Until the audit daemon is up and running, all log messages are stored in this queue. If the queue is overrun during boot process, the action defined by audit failure flag is taken. CM-6(a)
CCE-82670-1 Enable Auditing for Processes Which Start Prior to the Audit Daemon To ensure all processes can be audited, even those which start prior to the audit daemon, add the argument audit=1 to all BLS (Boot Loader Specification) entries ('options' line) for the Linux operating system in /boot/loader/entries/*.conf. Each process on the system carries an "auditable" flag which indicates whether its activities can be audited. Although auditd takes care of enabling this for all processes which launch after it does, adding the kernel argument ensures it is set for every process during boot. AC-17(1)
AU-14(1)
AU-10
CM-6(a)
IR-5(1)
CCE-82673-5 Enable page allocator poisoning To enable poisoning of free pages, add the argument page_poison=1 to all BLS (Boot Loader Specification) entries ('options' line) for the Linux operating system in /boot/loader/entries/*.conf. Poisoning writes an arbitrary value to freed pages, so any modification or reference to that page after being freed or before being initialized will be detected and prevented. This prevents many types of use-after-free vulnerabilities at little performance cost. Also prevents leak of data and detection of corrupted memory. CM-6(a)
CCE-82497-9 Enable Kernel Page-Table Isolation (KPTI) To enable Kernel page-table isolation, add the argument pti=on to all BLS (Boot Loader Specification) entries ('options' line) for the Linux operating system in /boot/loader/entries/*.conf. Kernel page-table isolation is a kernel feature that mitigates the Meltdown security vulnerability and hardens the kernel against attempts to bypass kernel address space layout randomization (KASLR). SI-16
CCE-82672-7 Enable SLUB/SLAB allocator poisoning To enable poisoning of SLUB/SLAB objects, add the argument slub_debug=P to all BLS (Boot Loader Specification) entries ('options' line) for the Linux operating system in /boot/loader/entries/*.conf. Poisoning writes an arbitrary value to freed objects, so any modification or reference to that object after being freed or before being initialized will be detected and prevented. This prevents many types of use-after-free vulnerabilities at little performance cost. Also prevents leak of data and detection of corrupted memory. CM-6(a)
CCE-82674-3 Disable vsyscalls To disable use of virtual syscalls, add the argument vsyscall=none to all BLS (Boot Loader Specification) entries ('options' line) for the Linux operating system in /boot/loader/entries/*.conf. Virtual Syscalls provide an opportunity of attack for a user who has control of the return instruction pointer. CM-7(a)
CCE-82495-3 Disable Ctrl-Alt-Del Burst Action By default, SystemD will reboot the system if the Ctrl-Alt-Del key sequence is pressed Ctrl-Alt-Delete more than 7 times in 2 seconds.

To configure the system to ignore the CtrlAltDelBurstAction setting, add or modify the following to /etc/systemd/system.conf:
CtrlAltDelBurstAction=none
A locally logged-in user who presses Ctrl-Alt-Del, when at the console, can reboot the system. If accidentally pressed, as could happen in the case of mixed OS environment, this can create the risk of short-term loss of availability of systems due to unintentional reboot. CM-6(a)
AC-6(1)
CM-6(a)
CCE-82493-8 Disable Ctrl-Alt-Del Reboot Activation By default, SystemD will reboot the system if the Ctrl-Alt-Del key sequence is pressed.

To configure the system to ignore the Ctrl-Alt-Del key sequence from the command line instead of rebooting the system, do either of the following:
ln -sf /dev/null /etc/systemd/system/ctrl-alt-del.target
or
systemctl mask ctrl-alt-del.target


Do not simply delete the /usr/lib/systemd/system/ctrl-alt-del.service file, as this file may be restored during future system updates.
A locally logged-in user who presses Ctrl-Alt-Del, when at the console, can reboot the system. If accidentally pressed, as could happen in the case of mixed OS environment, this can create the risk of short-term loss of availability of systems due to unintentional reboot. CM-6(a)
AC-6(1)
Disable Host-Based Authentication SSH's cryptographic host-based authentication is more secure than .rhosts authentication. However, it is not recommended that hosts unilaterally trust one another, even within an organization.

To disable host-based authentication, add or correct the following line in /etc/ssh/sshd_config:
HostbasedAuthentication no
SSH trust relationships mean a compromise on one host can allow an attacker to move trivially to other hosts. AC-3
AC-17(a)
CM-7(a)
CM-7(b)
CM-6(a)
CCE-82526-5 Disable Core Dumps for All Users To disable core dumps for all users, add the following line to /etc/security/limits.conf, or to a file within the /etc/security/limits.d/ directory:
*     hard   core    0
A core dump includes a memory image taken at the time the operating system terminates an application. The memory image could contain sensitive data and is generally useful only for developers trying to debug problems.
CCE-82540-6 Enable FIPS Mode To enable FIPS mode, run the following command:
fips-mode-setup --enable

The fips-mode-setup command will configure the system in FIPS mode by automatically configuring the following:
  • Setting the kernel FIPS mode flag (/proc/sys/crypto/fips_enabled) to 1
  • Creating /etc/system-fips
  • Setting the system crypto policy in /etc/crypto-policies/config to FIPS
  • Loading the Dracut fips module
Furthermore, the system running in FIPS mode should be FIPS certified by NIST.
Use of weak or untested encryption algorithms undermines the purposes of utilizing encryption to protect data. The operating system must implement cryptographic modules adhering to the higher standards approved by the federal government since this provides assurance they have been tested and validated. SC-12(2)
SC-12(3)
IA-7
SC-13
CM-6(a)
SC-12
CCE-82754-3 Ensure Red Hat GPG Key Installed To ensure the system can cryptographically verify base software packages come from Red Hat (and to connect to the Red Hat Network to receive them), the Red Hat GPG key must properly be installed. To install the Red Hat GPG key, run:
$ sudo subscription-manager register
If the system is not connected to the Internet or an RHN Satellite, then install the Red Hat GPG key from trusted media such as the Red Hat installation CD-ROM or DVD. Assuming the disc is mounted in /media/cdrom, use the following command as the root user to import it into the keyring:
$ sudo rpm --import /media/cdrom/RPM-GPG-KEY
Alternatively, the key may be pre-loaded during the RHEL installation. In such cases, the key can be installed by running the following command:
sudo rpm --import /etc/pki/rpm-gpg/RPM-GPG-KEY-redhat-release
Changes to software components can have significant effects on the overall security of the operating system. This requirement ensures the software has not been tampered with and that it has been provided by a trusted vendor. The Red Hat GPG key is necessary to cryptographically verify packages are from Red Hat. CM-5(3)
SI-7
SC-12
SC-12(3)
CM-6(a)
CCE-82551-3 Verify that Interactive Boot is Disabled Red Hat Enterprise Linux CoreOS 4 systems support an "interactive boot" option that can be used to prevent services from being started. On a Red Hat Enterprise Linux CoreOS 4 system, interactive boot can be enabled by providing a 1, yes, true, or on value to the systemd.confirm_spawn kernel argument in /etc/default/grub. Remove any instance of
systemd.confirm_spawn=(1|yes|true|on)
from the kernel arguments in that file to disable interactive boot. It is also required to change the runtime configuration, run:
/sbin/grubby --update-kernel=ALL --remove-args="systemd.confirm_spawn"
Using interactive boot, the console user could disable auditing, firewalls, or other services, weakening system security. SC-2(1)
CM-6(a)
CCE-82552-1 Set the UEFI Boot Loader Password The grub2 boot loader should have a superuser account and password protection enabled to protect boot-time settings.

Since plaintext passwords are a security risk, generate a hash for the password by running the following command:
$ grub2-setpassword
When prompted, enter the password that was selected.

Once the superuser password has been added, update the grub.cfg file by running:
grub2-mkconfig -o /boot/efi/EFI/redhat/grub.cfg
Password protection on the boot loader configuration ensures users with physical access cannot trivially alter important bootloader settings. These include which kernel to use, and whether to enter single-user mode. CM-6(a)
Disable Kerberos by removing host keytab Kerberos is not an approved key distribution method for Common Criteria. To prevent using Kerberos by system daemons, remove the Kerberos keytab files, especially /etc/krb5.keytab. The key derivation function (KDF) in Kerberos is not FIPS compatible.
CCE-82518-2 Disable ATM Support The Asynchronous Transfer Mode (ATM) is a protocol operating on network, data link, and physical layers, based on virtual circuits and virtual paths. To configure the system to prevent the atm kernel module from being loaded, add the following line to a file in the directory /etc/modprobe.d:
install atm /bin/true
Disabling ATM protects the system against exploitation of any flaws in its implementation.
CCE-82515-8 Disable Bluetooth Kernel Module The kernel's module loading system can be configured to prevent loading of the Bluetooth module. Add the following to the appropriate /etc/modprobe.d configuration file to prevent the loading of the Bluetooth module:
install bluetooth /bin/true
If Bluetooth functionality must be disabled, preventing the kernel from loading the kernel module provides an additional safeguard against its activation. AC-18(a)
AC-18(3)
CM-7(a)
CM-7(b)
CM-6(a)
MP-7
CCE-82519-0 Disable CAN Support The Controller Area Network (CAN) is a serial communications protocol which was initially developed for automotive and is now also used in marine, industrial, and medical applications. To configure the system to prevent the can kernel module from being loaded, add the following line to a file in the directory /etc/modprobe.d:
install can /bin/true
Disabling CAN protects the system against exploitation of any flaws in its implementation.
CCE-82514-1 Disable Mounting of cramfs To configure the system to prevent the cramfs kernel module from being loaded, add the following line to a file in the directory /etc/modprobe.d:
install cramfs /bin/true
This effectively prevents usage of this uncommon filesystem. The cramfs filesystem type is a compressed read-only Linux filesystem embedded in small footprint systems. A cramfs image can be used without having to first decompress the image.
Removing support for unneeded filesystem types reduces the local attack surface of the server. CM-7(a)
CM-7(b)
CM-6(a)
CCE-82517-4 Disable IEEE 1394 (FireWire) Support The IEEE 1394 (FireWire) is a serial bus standard for high-speed real-time communication. To configure the system to prevent the firewire-core kernel module from being loaded, add the following line to a file in the directory /etc/modprobe.d:
install firewire-core /bin/true
Disabling FireWire protects the system against exploitation of any flaws in its implementation.
CCE-82516-6 Disable SCTP Support The Stream Control Transmission Protocol (SCTP) is a transport layer protocol, designed to support the idea of message-oriented communication, with several streams of messages within one connection. To configure the system to prevent the sctp kernel module from being loaded, add the following line to a file in the directory /etc/modprobe.d:
install sctp /bin/true
Disabling SCTP protects the system against exploitation of any flaws in its implementation. CM-7(a)
CM-7(b)
CM-6(a)
CCE-82520-8 Disable TIPC Support The Transparent Inter-Process Communication (TIPC) protocol is designed to provide communications between nodes in a cluster. To configure the system to prevent the tipc kernel module from being loaded, add the following line to a file in the directory /etc/modprobe.d:
install tipc /bin/true
Disabling TIPC protects the system against exploitation of any flaws in its implementation. CM-7(a)
CM-7(b)
CM-6(a)
Add nodev Option to /boot The nodev mount option can be used to prevent device files from being created in /boot. Legitimate character and block devices should exist only in the /dev directory on the root partition or within chroot jails built for system services. Add the nodev option to the fourth column of /etc/fstab for the line which controls mounting of /boot. The only legitimate location for device files is the /dev directory located on the root partition. The only exception to this is chroot jails. CM-7(a)
CM-7(b)
CM-6(a)
AC-6
AC-6(1)
MP-7
Add nosuid Option to /boot The nosuid mount option can be used to prevent execution of setuid programs in /boot. The SUID and SGID permissions should not be required on the boot partition. Add the nosuid option to the fourth column of /etc/fstab for the line which controls mounting of /boot. The presence of SUID and SGID executables should be tightly controlled. Users should not be able to execute SUID or SGID binaries from boot partitions. CM-7(a)
CM-7(b)
CM-6(a)
AC-6
AC-6(1)
MP-7
CCE-82867-3 Add nodev Option to /dev/shm The nodev mount option can be used to prevent creation of device files in /dev/shm. Legitimate character and block devices should not exist within temporary directories like /dev/shm. Add the nodev option to the fourth column of /etc/fstab for the line which controls mounting of /dev/shm. The only legitimate location for device files is the /dev directory located on the root partition. The only exception to this is chroot jails. CM-7(a)
CM-7(b)
CM-6(a)
AC-6
AC-6(1)
MP-7
CCE-82868-1 Add noexec Option to /dev/shm The noexec mount option can be used to prevent binaries from being executed out of /dev/shm. It can be dangerous to allow the execution of binaries from world-writable temporary storage directories such as /dev/shm. Add the noexec option to the fourth column of /etc/fstab for the line which controls mounting of /dev/shm. Allowing users to execute binaries from world-writable directories such as /dev/shm can expose the system to potential compromise. CM-7(a)
CM-7(b)
CM-6(a)
AC-6
AC-6(1)
MP-7
CCE-82741-0 Add nosuid Option to /dev/shm The nosuid mount option can be used to prevent execution of setuid programs in /dev/shm. The SUID and SGID permissions should not be required in these world-writable directories. Add the nosuid option to the fourth column of /etc/fstab for the line which controls mounting of /dev/shm. The presence of SUID and SGID executables should be tightly controlled. Users should not be able to execute SUID or SGID binaries from temporary storage partitions. CM-7(a)
CM-7(b)
CM-6(a)
AC-6
AC-6(1)
MP-7
CCE-82740-2 Add nodev Option to /home The nodev mount option can be used to prevent device files from being created in /home. Legitimate character and block devices should exist only in the /dev directory on the root partition or within chroot jails built for system services. Add the nodev option to the fourth column of /etc/fstab for the line which controls mounting of /home. The only legitimate location for device files is the /dev directory located on the root partition. The only exception to this is chroot jails.
Add nosuid Option to /home The nosuid mount option can be used to prevent execution of setuid programs in /home. The SUID and SGID permissions should not be required in these user data directories. Add the nosuid option to the fourth column of /etc/fstab for the line which controls mounting of /home. The presence of SUID and SGID executables should be tightly controlled. Users should not be able to execute SUID or SGID binaries from user home directory partitions. CM-7(a)
CM-7(b)
CM-6(a)
AC-6
AC-6(1)
MP-7
Add nodev Option to Non-Root Local Partitions The nodev mount option prevents files from being interpreted as character or block devices. Legitimate character and block devices should exist only in the /dev directory on the root partition or within chroot jails built for system services. Add the nodev option to the fourth column of /etc/fstab for the line which controls mounting of any non-root local partitions. The nodev mount option prevents files from being interpreted as character or block devices. The only legitimate location for device files is the /dev directory located on the root partition. The only exception to this is chroot jails, for which it is not advised to set nodev on these filesystems. CM-7(a)
CM-7(b)
CM-6(a)
AC-6
AC-6(1)
MP-7
Add nodev Option to /tmp The nodev mount option can be used to prevent device files from being created in /tmp. Legitimate character and block devices should not exist within temporary directories like /tmp. Add the nodev option to the fourth column of /etc/fstab for the line which controls mounting of /tmp. The only legitimate location for device files is the /dev directory located on the root partition. The only exception to this is chroot jails. CM-7(a)
CM-7(b)
CM-6(a)
AC-6
AC-6(1)
MP-7
Add noexec Option to /tmp The noexec mount option can be used to prevent binaries from being executed out of /tmp. Add the noexec option to the fourth column of /etc/fstab for the line which controls mounting of /tmp. Allowing users to execute binaries from world-writable directories such as /tmp should never be necessary in normal operation and can expose the system to potential compromise. CM-7(a)
CM-7(b)
CM-6(a)
AC-6
AC-6(1)
MP-7
Add nosuid Option to /tmp The nosuid mount option can be used to prevent execution of setuid programs in /tmp. The SUID and SGID permissions should not be required in these world-writable directories. Add the nosuid option to the fourth column of /etc/fstab for the line which controls mounting of /tmp. The presence of SUID and SGID executables should be tightly controlled. Users should not be able to execute SUID or SGID binaries from temporary storage partitions. CM-7(a)
CM-7(b)
CM-6(a)
AC-6
AC-6(1)
MP-7
Add nodev Option to /var/log/audit The nodev mount option can be used to prevent device files from being created in /var/log/audit. Legitimate character and block devices should exist only in the /dev directory on the root partition or within chroot jails built for system services. Add the nodev option to the fourth column of /etc/fstab for the line which controls mounting of /var/log/audit. The only legitimate location for device files is the /dev directory located on the root partition. The only exception to this is chroot jails. CM-7(a)
CM-7(b)
CM-6(a)
AC-6
AC-6(1)
MP-7
Add noexec Option to /var/log/audit The noexec mount option can be used to prevent binaries from being executed out of /var/log/audit. Add the noexec option to the fourth column of /etc/fstab for the line which controls mounting of /var/log/audit. Allowing users to execute binaries from directories containing audit log files such as /var/log/audit should never be necessary in normal operation and can expose the system to potential compromise. CM-7(a)
CM-7(b)
CM-6(a)
AC-6
AC-6(1)
MP-7
Add nosuid Option to /var/log/audit The nosuid mount option can be used to prevent execution of setuid programs in /var/log/audit. The SUID and SGID permissions should not be required in directories containing audit log files. Add the nosuid option to the fourth column of /etc/fstab for the line which controls mounting of /var/log/audit. The presence of SUID and SGID executables should be tightly controlled. Users should not be able to execute SUID or SGID binaries from partitions designated for audit log files. CM-7(a)
CM-7(b)
CM-6(a)
AC-6
AC-6(1)
MP-7
Add nodev Option to /var/log The nodev mount option can be used to prevent device files from being created in /var/log. Legitimate character and block devices should exist only in the /dev directory on the root partition or within chroot jails built for system services. Add the nodev option to the fourth column of /etc/fstab for the line which controls mounting of /var/log. The only legitimate location for device files is the /dev directory located on the root partition. The only exception to this is chroot jails. CM-7(a)
CM-7(b)
CM-6(a)
AC-6
AC-6(1)
MP-7
Add noexec Option to /var/log The noexec mount option can be used to prevent binaries from being executed out of /var/log. Add the noexec option to the fourth column of /etc/fstab for the line which controls mounting of /var/log. Allowing users to execute binaries from directories containing log files such as /var/log should never be necessary in normal operation and can expose the system to potential compromise. CM-7(a)
CM-7(b)
CM-6(a)
AC-6
AC-6(1)
MP-7
Add nosuid Option to /var/log The nosuid mount option can be used to prevent execution of setuid programs in /var/log. The SUID and SGID permissions should not be required in directories containing log files. Add the nosuid option to the fourth column of /etc/fstab for the line which controls mounting of /var/log. The presence of SUID and SGID executables should be tightly controlled. Users should not be able to execute SUID or SGID binaries from partitions designated for log files. CM-7(a)
CM-7(b)
CM-6(a)
AC-6
AC-6(1)
MP-7
Add nodev Option to /var The nodev mount option can be used to prevent device files from being created in /var. Legitimate character and block devices should exist only in the /dev directory on the root partition or within chroot jails built for system services. Add the nodev option to the fourth column of /etc/fstab for the line which controls mounting of /var. The only legitimate location for device files is the /dev directory located on the root partition. The only exception to this is chroot jails. CM-7(a)
CM-7(b)
CM-6(a)
AC-6
AC-6(1)
MP-7
CCE-82735-2 Add nodev Option to /var/tmp The nodev mount option can be used to prevent device files from being created in /var/tmp. Legitimate character and block devices should not exist within temporary directories like /var/tmp. Add the nodev option to the fourth column of /etc/fstab for the line which controls mounting of /var/tmp. The only legitimate location for device files is the /dev directory located on the root partition. The only exception to this is chroot jails.
CCE-82866-5 Add noexec Option to /var/tmp The noexec mount option can be used to prevent binaries from being executed out of /var/tmp. Add the noexec option to the fourth column of /etc/fstab for the line which controls mounting of /var/tmp. Allowing users to execute binaries from world-writable directories such as /var/tmp should never be necessary in normal operation and can expose the system to potential compromise.
CCE-82736-0 Add nosuid Option to /var/tmp The nosuid mount option can be used to prevent execution of setuid programs in /var/tmp. The SUID and SGID permissions should not be required in these world-writable directories. Add the nosuid option to the fourth column of /etc/fstab for the line which controls mounting of /var/tmp. The presence of SUID and SGID executables should be tightly controlled. Users should not be able to execute SUID or SGID binaries from temporary storage partitions.
CCE-82553-9 Prevent Login to Accounts With Empty Password If an account is configured for password authentication but does not have an assigned password, it may be possible to log into the account without authentication. Remove any instances of the nullok in /etc/pam.d/system-auth to prevent logins with empty passwords. If an account has an empty password, anyone could log in and run commands with the privileges of that account. Accounts with empty passwords should never be used in operational environments. IA-5(1)(a)
IA-5(c)
CM-6(a)
Prevent user from disabling the screen lock The tmux terminal multiplexer is used to implement autimatic session locking. It should not be listed in /etc/shells. Not listing tmux among permitted shells prevents malicious program running as user from lowering security by disabling the screen lock.
CCE-82669-3 Ensure the audit Subsystem is Installed The audit package should be installed. The auditd service is an access monitoring and accounting daemon, watching system calls to audit any access, in comparison with potential local access control policy such as SELinux policy. AC-7(a)
AU-7(1)
AU-7(2)
AU-14
AU-12(2)
AU-2(a)
CM-6(a)
CCE-82533-1 Install fapolicyd Package The fapolicyd package can be installed with the following command:

fapolicyd (File Access Policy Daemon) implements application whitelisting to decide file access rights. CM-6(a)
SI-4(22)
Uninstall Sendmail Package Sendmail is not the default mail transfer agent and is not installed by default. The sendmail package can be removed with the following command:

The sendmail software was not developed with security in mind and its design prevents it from being effectively contained by SELinux. Postfix should be used instead. CM-7(a)
CM-7(b)
CM-6(a)
Install the tmux Package To enable console screen locking, install the tmux package. The tmux package can be installed with the following command:

Instruct users to begin new terminal sessions with the following command:
$ tmux
The console can now be locked with the following key combination:
ctrl+b :lock-session
A session time-out lock is a temporary action taken when a user stops work and moves away from the immediate physical vicinity of the information system but does not logout because of the temporary nature of the absence. Rather than relying on the user to manually lock their operation system session prior to vacating the vicinity, operating systems need to be able to identify when a user's session has idled and take action to initiate the session lock.

The tmux package allows for a session lock to be implemented and configured.
CM-6(a)
CCE-82524-0 Install usbguard Package The usbguard package can be installed with the following command:

usbguard is a software framework that helps to protect against rogue USB devices by implementing basic whitelisting/blacklisting capabilities based on USB device attributes.
CCE-82739-4 Ensure /home Located On Separate Partition If user home directories will be stored locally, create a separate partition for /home at installation time (or migrate it later using LVM). If /home will be mounted from another system such as an NFS server, then creating a separate partition is not necessary at installation time, and the mountpoint can instead be configured later. Ensuring that /home is mounted on its own partition enables the setting of more restrictive mount options, and also helps ensure that users cannot trivially fill partitions used for log or audit data storage. CM-6(a)
SC-5(2)
Ensure /var Located On Separate Partition The /var directory is used by daemons and other system services to store frequently-changing data. Ensure that /var has its own partition or logical volume at installation time, or migrate it using LVM. Ensuring that /var is mounted on its own partition enables the setting of more restrictive mount options. This helps protect system services such as daemons or other programs which use it. It is not uncommon for the /var directory to contain world-writable directories installed by other software packages. CM-6(a)
SC-5(2)
CCE-82737-8 Ensure /var/log Located On Separate Partition System logs are stored in the /var/log directory. Ensure that it has its own partition or logical volume at installation time, or migrate it using LVM. Placing /var/log in its own partition enables better separation between log files and other files in /var/. CM-6(a)
AU-4
SC-5(2)
CCE-82738-6 Ensure /var/log/audit Located On Separate Partition Audit logs are stored in the /var/log/audit directory. Ensure that it has its own partition or logical volume at installation time, or migrate it later using LVM. Make absolutely certain that it is large enough to store all audit logs that will be created by the auditing daemon. Placing /var/log/audit in its own partition enables better separation between audit files and other files, and helps ensure that auditing cannot be halted due to the partition running out of space. CM-6(a)
AU-4
SC-5(2)
CCE-82550-5 Require Authentication for Single User Mode Single-user mode is intended as a system recovery method, providing a single user root access to the system by providing a boot option at startup. By default, no authentication is performed if single-user mode is selected.

By default, single-user mode is protected by requiring a password and is set in /usr/lib/systemd/system/rescue.service.
This prevents attackers with physical access from trivially bypassing security on the machine and gaining root access. Such accesses are further prevented by configuring the bootloader password. IA-2
AC-3
CM-6(a)
CCE-82532-3 Configure SELinux Policy The SELinux targeted policy is appropriate for general-purpose desktops and servers, as well as systems in many other roles. To configure the system to use this policy, add or correct the following line in /etc/selinux/config:
SELINUXTYPE=
Other policies, such as mls, provide additional security labeling and greater confinement but are not compatible with many general-purpose use cases.
Setting the SELinux policy to targeted or a more specialized policy ensures the system will confine processes that are likely to be targeted for exploitation, such as network or system services.

Note: During the development or debugging of SELinux modules, it is common to temporarily place non-production systems in permissive mode. In such temporary cases, SELinux policies should be developed, and once work is completed, the system should be reconfigured to .
AC-3
AC-3(3)(a)
AU-9
SC-7(21)
CCE-82531-5 Ensure SELinux State is Enforcing The SELinux state should be set to at system boot time. In the file /etc/selinux/config, add or correct the following line to configure the system to boot into enforcing mode:
SELINUX=
Setting the SELinux state to enforcing ensures SELinux is able to confine potentially compromised processes to the security policy, which is designed to prevent them from causing damage to the system or further elevating their privileges. AC-3
AC-3(3)(a)
AU-9
SC-7(21)
CCE-82463-1 Enable auditd Service The auditd service is an essential userspace component of the Linux Auditing System, as it is responsible for writing audit records to disk. The auditd service can be enabled with the following command:
$ sudo systemctl enable auditd.service
Without establishing what type of events occurred, it would be difficult to establish, correlate, and investigate the events leading up to an outage or attack. Ensuring the auditd service is active ensures audit records generated by the kernel are appropriately recorded.

Additionally, a properly configured audit subsystem ensures that actions of individual system users can be uniquely traced to those users so they can be held accountable for their actions.
AC-2(g)
AU-3
AU-10
AU-2(d)
AU-12(c)
AU-14(1)
AC-6(9)
CM-6(a)
CCE-82496-1 Disable debug-shell SystemD Service SystemD's debug-shell service is intended to diagnose SystemD related boot issues with various systemctl commands. Once enabled and following a system reboot, the root shell will be available on tty9 which is access by pressing CTRL-ALT-F9. The debug-shell service should only be used for SystemD related issues and should otherwise be disabled.

By default, the debug-shell SystemD service is already disabled. The debug-shell service can be disabled with the following command:
$ sudo systemctl mask --now debug-shell.service
This prevents attackers with physical access from trivially bypassing security on the machine through valid troubleshooting configurations and gaining root access when the system is rebooted.
CCE-82534-9 Enable the File Access Policy Service The File Access Policy service should be enabled. The fapolicyd service can be enabled with the following command:
$ sudo systemctl enable fapolicyd.service
The fapolicyd service (File Access Policy Daemon) implements application whitelisting to decide file access rights. CM-6(a)
SI-4(22)
Verify iptables Enabled The iptables service can be enabled with the following command:
$ sudo systemctl enable iptables.service
The iptables service provides the system's host-based firewalling capability for IPv4 and ICMP. AC-4
CM-7(b)
CA-3(5)
SC-7(21)
CM-6(a)
CCE-82530-7 Disable acquiring, saving, and processing core dumps The systemd-coredump.socket unit is a socket activation of the systemd-coredump@.service which processes core dumps. By masking the unit, core dump processing is disabled. A core dump includes a memory image taken at the time the operating system terminates an application. The memory image could contain sensitive data and is generally useful only for developers trying to debug problems.
CCE-82537-2 Enable the USBGuard Service The USBGuard service should be enabled. The usbguard service can be enabled with the following command:
$ sudo systemctl enable usbguard.service
The usbguard service must be running in order to enforce the USB device authorization policy for all USB devices.
Configure session renegotiation for SSH client The RekeyLimit parameter specifies how often the session key is renegotiated, both in terms of amount of data that may be transmitted and the time elapsed. To decrease the default limits, put line RekeyLimit to file /etc/ssh/ssh_config.d/02-rekey-limit.conf. Make sure that there is no other RekeyLimit configuration preceding the include directive in the main config file /etc/ssh/ssh_config. Check also other files in /etc/ssh/ssh_config.d directory. Files are processed according to lexicographical order of file names. Make sure that there is no file processed before 02-rekey-limit.conf containing definition of RekeyLimit. By decreasing the limit based on the amount of data and enabling time-based limit, effects of potential attacks against encryption keys are limited.
Disable SSH Access via Empty Passwords To explicitly disallow SSH login from accounts with empty passwords, add or correct the following line in /etc/ssh/sshd_config:
PermitEmptyPasswords no

Any accounts with empty passwords should be disabled immediately, and PAM configuration should prevent users from being able to assign themselves empty passwords.
Configuring this setting for the SSH daemon provides additional assurance that remote login via SSH will require a password, even in the event of misconfiguration elsewhere. AC-17(a)
CM-7(a)
CM-7(b)
CM-6(a)
Disable GSSAPI Authentication Unless needed, SSH should not permit extraneous or unnecessary authentication mechanisms like GSSAPI. To disable GSSAPI authentication, add or correct the following line in the /etc/ssh/sshd_config file:
GSSAPIAuthentication no
GSSAPI authentication is used to provide additional authentication mechanisms to applications. Allowing GSSAPI authentication through SSH exposes the system's GSSAPI to remote hosts, increasing the attack surface of the system. CM-7(a)
CM-7(b)
CM-6(a)
AC-17(a)
Disable Kerberos Authentication Unless needed, SSH should not permit extraneous or unnecessary authentication mechanisms like Kerberos. To disable Kerberos authentication, add or correct the following line in the /etc/ssh/sshd_config file:
KerberosAuthentication no
Kerberos authentication for SSH is often implemented using GSSAPI. If Kerberos is enabled through SSH, the SSH daemon provides a means of access to the system's Kerberos implementation. Vulnerabilities in the system's Kerberos implementations may be subject to exploitation. AC-17(a)
CM-7(a)
CM-7(b)
CM-6(a)
Disable SSH Root Login The root user should never be allowed to login to a system directly over a network. To disable root login via SSH, add or correct the following line in /etc/ssh/sshd_config:
PermitRootLogin no
Even though the communications channel may be encrypted, an additional layer of security is gained by extending the policy of not logging directly on as root. In addition, logging in with a user-specific account provides individual accountability of actions performed on the system and also helps to minimize direct attack attempts on root's password. AC-6(2)
AC-17(a)
IA-2
IA-2(5)
CM-7(a)
CM-7(b)
CM-6(a)
Enable Use of Strict Mode Checking SSHs StrictModes option checks file and ownership permissions in the user's home directory .ssh folder before accepting login. If world- writable permissions are found, logon is rejected. To enable StrictModes in SSH, add or correct the following line in the /etc/ssh/sshd_config file:
StrictModes yes
If other users have access to modify user-specific SSH configuration files, they may be able to log into the system as another user. AC-6
AC-17(a)
CM-6(a)
Enable SSH Warning Banner To enable the warning banner and ensure it is consistent across the system, add or correct the following line in /etc/ssh/sshd_config:
Banner /etc/issue
Another section contains information on how to create an appropriate system-wide warning banner.
The warning message reinforces policy awareness during the logon process and facilitates possible legal action against attackers. Alternatively, systems whose ownership should not be obvious should ensure usage of a banner that does not provide easy attribution. AC-8(a)
AC-8(c)
AC-17(a)
CM-6(a)
Force frequent session key renegotiation The RekeyLimit parameter specifies how often the session key of the is renegotiated, both in terms of amount of data that may be transmitted and the time elapsed. To decrease the default limits, put line RekeyLimit to file /etc/ssh/sshd_config. By decreasing the limit based on the amount of data and enabling time-based limit, effects of potential attacks against encryption keys are limited.
CCE-82549-7 Set SSH Idle Timeout Interval SSH allows administrators to set an idle timeout interval. After this interval has passed, the idle user will be automatically logged out.

To set an idle timeout interval, edit the following line in /etc/ssh/sshd_config as follows:
ClientAliveInterval 


The timeout interval is given in seconds. For example, have a timeout of 10 minutes, set interval to 600.

If a shorter timeout has already been set for the login shell, that value will preempt any SSH setting made in /etc/ssh/sshd_config. Keep in mind that some processes may stop SSH from correctly detecting that the user is idle.
Terminating an idle ssh session within a short time period reduces the window of opportunity for unauthorized personnel to take control of a management session enabled on the console or console port that has been let unattended. CM-6(a)
AC-17(a)
AC-2(5)
AC-12
AC-17(a)
SC-10
CM-6(a)
CCE-82464-9 Set SSH Client Alive Count Max The SSH server sends at most ClientAliveCountMax messages during a SSH session and waits for a response from the SSH client. The option ClientAliveInterval configures timeout after each ClientAliveCountMax message. If the SSH server does not receive a response from the client, then the connection is considered idle and terminated. To ensure the SSH idle timeout occurs precisely when the ClientAliveInterval is set, set the ClientAliveCountMax to value of 0. This ensures a user login will be terminated as soon as the ClientAliveInterval is reached. AC-2(5)
AC-12
AC-17(a)
SC-10
CM-6(a)
CCE-82506-7 Enable Kernel Parameter to Enforce DAC on Hardlinks To set the runtime status of the fs.protected_hardlinks kernel parameter, run the following command:
$ sudo sysctl -w fs.protected_hardlinks=1
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d:
fs.protected_hardlinks = 1
By enabling this kernel parameter, users can no longer create soft or hard links to files which they do not own. Disallowing such hardlinks mitigate vulnerabilities based on insecure file system accessed by privileged programs, avoiding an exploitation vector exploiting unsafe use of open() or creat(). CM-6(a)
AC-6(1)
CCE-82507-5 Enable Kernel Parameter to Enforce DAC on Symlinks To set the runtime status of the fs.protected_symlinks kernel parameter, run the following command:
$ sudo sysctl -w fs.protected_symlinks=1
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d:
fs.protected_symlinks = 1
By enabling this kernel parameter, symbolic links are permitted to be followed only when outside a sticky world-writable directory, or when the UID of the link and follower match, or when the directory owner matches the symlink's owner. Disallowing such symlinks helps mitigate vulnerabilities based on insecure file system accessed by privileged programs, avoiding an exploitation vector exploiting unsafe use of open() or creat(). CM-6(a)
AC-6(1)
CCE-82527-3 Disable storing core dumps To set the runtime status of the kernel.core_pattern kernel parameter, run the following command:
$ sudo sysctl -w kernel.core_pattern=|/bin/false
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d:
kernel.core_pattern = |/bin/false
A core dump includes a memory image taken at the time the operating system terminates an application. The memory image could contain sensitive data and is generally useful only for developers trying to debug problems.
CCE-82499-5 Restrict Access to Kernel Message Buffer To set the runtime status of the kernel.dmesg_restrict kernel parameter, run the following command:
$ sudo sysctl -w kernel.dmesg_restrict=1
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d:
kernel.dmesg_restrict = 1
Unprivileged access to the kernel syslog can expose sensitive kernel address information. SI-11(a)
SI-11(b)
CCE-82500-0 Disable Kernel Image Loading To set the runtime status of the kernel.kexec_load_disabled kernel parameter, run the following command:
$ sudo sysctl -w kernel.kexec_load_disabled=1
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d:
kernel.kexec_load_disabled = 1
Disabling kexec_load allows greater control of the kernel memory. It makes it impossible to load another kernel image after it has been disabled.
CCE-82498-7 Restrict Exposed Kernel Pointer Addresses Access To set the runtime status of the kernel.kptr_restrict kernel parameter, run the following command:
$ sudo sysctl -w kernel.kptr_restrict=1
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d:
kernel.kptr_restrict = 1
Exposing kernel pointers (through procfs or seq_printf()) exposes kernel writeable structures that can contain functions pointers. If a write vulnereability occurs in the kernel allowing a write access to any of this structure, the kernel can be compromise. This option disallow any program withtout the CAP_SYSLOG capability from getting the kernel pointers addresses, replacing them with 0. SC-30
SC-30(2)
SC-30(5)
CM-6(a)
CCE-82502-6 Disallow kernel profiling by unprivileged users To set the runtime status of the kernel.perf_event_paranoid kernel parameter, run the following command:
$ sudo sysctl -w kernel.perf_event_paranoid=2
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d:
kernel.perf_event_paranoid = 2
Kernel profiling can reveal sensitive information about kernel behaviour.
CCE-82504-2 Disable Access to Network bpf() Syscall From Unprivileged Processes To set the runtime status of the kernel.unprivileged_bpf_disabled kernel parameter, run the following command:
$ sudo sysctl -w kernel.unprivileged_bpf_disabled=1
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d:
kernel.unprivileged_bpf_disabled = 1
Loading and accessing the packet filters programs and maps using the bpf() syscall has the potential of revealing sensitive information about the kernel state.
CCE-82501-8 Restrict usage of ptrace to descendant processes To set the runtime status of the kernel.yama.ptrace_scope kernel parameter, run the following command:
$ sudo sysctl -w kernel.yama.ptrace_scope=1
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d:
kernel.yama.ptrace_scope = 1
Unrestricted usage of ptrace allows compromised binaries to run ptrace on another processes of the user. Like this, the attacker can steal sensitive information from the target processes (e.g. SSH sessions, web browser, ...) without any additional assistance from the user (i.e. without resorting to phishing).
CCE-82505-9 Harden the operation of the BPF just-in-time compiler To set the runtime status of the net.core.bpf_jit_harden kernel parameter, run the following command:
$ sudo sysctl -w net.core.bpf_jit_harden=2
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d:
net.core.bpf_jit_harden = 2
When hardened, the extended Berkeley Packet Filter just-in-time compiler will randomize any kernel addresses in the BPF programs and maps, and will not expose the JIT addresses in /proc/kallsyms.
CCE-82469-8 Disable Accepting ICMP Redirects for All IPv4 Interfaces To set the runtime status of the net.ipv4.conf.all.accept_redirects kernel parameter, run the following command:
$ sudo sysctl -w net.ipv4.conf.all.accept_redirects=0
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d:
net.ipv4.conf.all.accept_redirects = 0
ICMP redirect messages are used by routers to inform hosts that a more direct route exists for a particular destination. These messages modify the host's route table and are unauthenticated. An illicit ICMP redirect message could result in a man-in-the-middle attack.
This feature of the IPv4 protocol has few legitimate uses. It should be disabled unless absolutely required."
CM-7(a)
CM-7(b)
CM-6(a)
SC-7(a)
CCE-82478-9 Disable Kernel Parameter for Accepting Source-Routed Packets on all IPv4 Interfaces To set the runtime status of the net.ipv4.conf.all.accept_source_route kernel parameter, run the following command:
$ sudo sysctl -w net.ipv4.conf.all.accept_source_route=0
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d:
net.ipv4.conf.all.accept_source_route = 0
Source-routed packets allow the source of the packet to suggest routers forward the packet along a different path than configured on the router, which can be used to bypass network security measures. This requirement applies only to the forwarding of source-routerd traffic, such as when IPv4 forwarding is enabled and the system is functioning as a router.

Accepting source-routed packets in the IPv4 protocol has few legitimate uses. It should be disabled unless it is absolutely required.
CM-7(a)
CM-7(b)
SC-5
CM-6(a)
SC-7(a)
CCE-82486-2 Enable Kernel Parameter to Log Martian Packets on all IPv4 Interfaces To set the runtime status of the net.ipv4.conf.all.log_martians kernel parameter, run the following command:
$ sudo sysctl -w net.ipv4.conf.all.log_martians=1
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d:
net.ipv4.conf.all.log_martians = 1
The presence of "martian" packets (which have impossible addresses) as well as spoofed packets, source-routed packets, and redirects could be a sign of nefarious network activity. Logging these packets enables this activity to be detected. CM-7(a)
CM-7(b)
SC-5(3)(a)
CCE-82488-8 Enable Kernel Parameter to Use Reverse Path Filtering on all IPv4 Interfaces To set the runtime status of the net.ipv4.conf.all.rp_filter kernel parameter, run the following command:
$ sudo sysctl -w net.ipv4.conf.all.rp_filter=1
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d:
net.ipv4.conf.all.rp_filter = 1
Enabling reverse path filtering drops packets with source addresses that should not have been able to be received on the interface they were received on. It should not be used on systems which are routers for complicated networks, but is helpful for end hosts and routers serving small networks. CM-7(a)
CM-7(b)
CM-6(a)
SC-7(a)
CCE-82482-1 Disable Kernel Parameter for Accepting Secure ICMP Redirects on all IPv4 Interfaces To set the runtime status of the net.ipv4.conf.all.secure_redirects kernel parameter, run the following command:
$ sudo sysctl -w net.ipv4.conf.all.secure_redirects=0
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d:
net.ipv4.conf.all.secure_redirects = 0
Accepting "secure" ICMP redirects (from those gateways listed as default gateways) has few legitimate uses. It should be disabled unless it is absolutely required. CM-7(a)
CM-7(b)
CM-6(a)
SC-7(a)
CCE-82484-7 Disable Kernel Parameter for Sending ICMP Redirects on all IPv4 Interfaces To set the runtime status of the net.ipv4.conf.all.send_redirects kernel parameter, run the following command:
$ sudo sysctl -w net.ipv4.conf.all.send_redirects=0
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d:
net.ipv4.conf.all.send_redirects = 0
ICMP redirect messages are used by routers to inform hosts that a more direct route exists for a particular destination. These messages contain information from the system's route table possibly revealing portions of the network topology.
The ability to send ICMP redirects is only appropriate for systems acting as routers.
CM-7(a)
CM-7(b)
SC-5
CM-6(a)
SC-7(a)
CCE-82470-6 Disable Kernel Parameter for Accepting ICMP Redirects by Default on IPv4 Interfaces To set the runtime status of the net.ipv4.conf.default.accept_redirects kernel parameter, run the following command:
$ sudo sysctl -w net.ipv4.conf.default.accept_redirects=0
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d:
net.ipv4.conf.default.accept_redirects = 0
ICMP redirect messages are used by routers to inform hosts that a more direct route exists for a particular destination. These messages modify the host's route table and are unauthenticated. An illicit ICMP redirect message could result in a man-in-the-middle attack.
This feature of the IPv4 protocol has few legitimate uses. It should be disabled unless absolutely required.
CM-7(a)
CM-7(b)
CM-6(a)
SC-7(a)
CCE-82479-7 Disable Kernel Parameter for Accepting Source-Routed Packets on IPv4 Interfaces by Default To set the runtime status of the net.ipv4.conf.default.accept_source_route kernel parameter, run the following command:
$ sudo sysctl -w net.ipv4.conf.default.accept_source_route=0
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d:
net.ipv4.conf.default.accept_source_route = 0
Source-routed packets allow the source of the packet to suggest routers forward the packet along a different path than configured on the router, which can be used to bypass network security measures.
Accepting source-routed packets in the IPv4 protocol has few legitimate uses. It should be disabled unless it is absolutely required, such as when IPv4 forwarding is enabled and the system is legitimately functioning as a router.
CM-7(a)
CM-7(b)
SC-5
SC-7(a)
CCE-82487-0 Enable Kernel Paremeter to Log Martian Packets on all IPv4 Interfaces by Default To set the runtime status of the net.ipv4.conf.default.log_martians kernel parameter, run the following command:
$ sudo sysctl -w net.ipv4.conf.default.log_martians=1
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d:
net.ipv4.conf.default.log_martians = 1
The presence of "martian" packets (which have impossible addresses) as well as spoofed packets, source-routed packets, and redirects could be a sign of nefarious network activity. Logging these packets enables this activity to be detected. CM-7(a)
CM-7(b)
SC-5(3)(a)
CCE-82489-6 Enable Kernel Parameter to Use Reverse Path Filtering on all IPv4 Interfaces by Default To set the runtime status of the net.ipv4.conf.default.rp_filter kernel parameter, run the following command:
$ sudo sysctl -w net.ipv4.conf.default.rp_filter=1
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d:
net.ipv4.conf.default.rp_filter = 1
Enabling reverse path filtering drops packets with source addresses that should not have been able to be received on the interface they were received on. It should not be used on systems which are routers for complicated networks, but is helpful for end hosts and routers serving small networks. CM-7(a)
CM-7(b)
CM-6(a)
SC-7(a)
CCE-82483-9 Configure Kernel Parameter for Accepting Secure Redirects By Default To set the runtime status of the net.ipv4.conf.default.secure_redirects kernel parameter, run the following command:
$ sudo sysctl -w net.ipv4.conf.default.secure_redirects=0
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d:
net.ipv4.conf.default.secure_redirects = 0
Accepting "secure" ICMP redirects (from those gateways listed as default gateways) has few legitimate uses. It should be disabled unless it is absolutely required. CM-7(a)
CM-7(b)
SC-5
SC-7(a)
CCE-82485-4 Disable Kernel Parameter for Sending ICMP Redirects on all IPv4 Interfaces by Default To set the runtime status of the net.ipv4.conf.default.send_redirects kernel parameter, run the following command:
$ sudo sysctl -w net.ipv4.conf.default.send_redirects=0
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d:
net.ipv4.conf.default.send_redirects = 0
ICMP redirect messages are used by routers to inform hosts that a more direct route exists for a particular destination. These messages contain information from the system's route table possibly revealing portions of the network topology.
The ability to send ICMP redirects is only appropriate for systems acting as routers.
CM-7(a)
CM-7(b)
SC-5
CM-6(a)
SC-7(a)
CCE-82491-2 Enable Kernel Parameter to Ignore ICMP Broadcast Echo Requests on IPv4 Interfaces To set the runtime status of the net.ipv4.icmp_echo_ignore_broadcasts kernel parameter, run the following command:
$ sudo sysctl -w net.ipv4.icmp_echo_ignore_broadcasts=1
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d:
net.ipv4.icmp_echo_ignore_broadcasts = 1
Responding to broadcast (ICMP) echoes facilitates network mapping and provides a vector for amplification attacks.
Ignoring ICMP echo requests (pings) sent to broadcast or multicast addresses makes the system slightly more difficult to enumerate on the network.
CM-7(a)
CM-7(b)
SC-5
CCE-82490-4 Enable Kernel Parameter to Ignore Bogus ICMP Error Responses on IPv4 Interfaces To set the runtime status of the net.ipv4.icmp_ignore_bogus_error_responses kernel parameter, run the following command:
$ sudo sysctl -w net.ipv4.icmp_ignore_bogus_error_responses=1
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d:
net.ipv4.icmp_ignore_bogus_error_responses = 1
Ignoring bogus ICMP error responses reduces log size, although some activity would not be logged. CM-7(a)
CM-7(b)
SC-5
CCE-82492-0 Enable Kernel Parameter to Use TCP Syncookies on IPv4 Interfaces To set the runtime status of the net.ipv4.tcp_syncookies kernel parameter, run the following command:
$ sudo sysctl -w net.ipv4.tcp_syncookies=1
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d:
net.ipv4.tcp_syncookies = 1
A TCP SYN flood attack can cause a denial of service by filling a system's TCP connection table with connections in the SYN_RCVD state. Syncookies can be used to track a connection when a subsequent ACK is received, verifying the initiator is attempting a valid connection and is not a flood source. This feature is activated when a flood condition is detected, and enables the system to continue servicing valid connection requests. CM-7(a)
CM-7(b)
SC-5(1)
SC-5(2)
SC-5(3)(a)
CM-6(a)
CCE-82467-2 Configure Accepting Router Advertisements on All IPv6 Interfaces To set the runtime status of the net.ipv6.conf.all.accept_ra kernel parameter, run the following command:
$ sudo sysctl -w net.ipv6.conf.all.accept_ra=0
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d:
net.ipv6.conf.all.accept_ra = 0
An illicit router advertisement message could result in a man-in-the-middle attack. CM-7(a)
CM-7(b)
CM-6(a)
CCE-82471-4 Disable Accepting ICMP Redirects for All IPv6 Interfaces To set the runtime status of the net.ipv6.conf.all.accept_redirects kernel parameter, run the following command:
$ sudo sysctl -w net.ipv6.conf.all.accept_redirects=0
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d:
net.ipv6.conf.all.accept_redirects = 0
An illicit ICMP redirect message could result in a man-in-the-middle attack. CM-7(a)
CM-7(b)
CM-6(a)
CCE-82480-5 Disable Kernel Parameter for Accepting Source-Routed Packets on all IPv6 Interfaces To set the runtime status of the net.ipv6.conf.all.accept_source_route kernel parameter, run the following command:
$ sudo sysctl -w net.ipv6.conf.all.accept_source_route=0
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d:
net.ipv6.conf.all.accept_source_route = 0
Source-routed packets allow the source of the packet to suggest routers forward the packet along a different path than configured on the router, which can be used to bypass network security measures. This requirement applies only to the forwarding of source-routerd traffic, such as when IPv6 forwarding is enabled and the system is functioning as a router.

Accepting source-routed packets in the IPv6 protocol has few legitimate uses. It should be disabled unless it is absolutely required.
CM-7(a)
CM-7(b)
CM-6(a)
CCE-82468-0 Disable Accepting Router Advertisements on all IPv6 Interfaces by Default To set the runtime status of the net.ipv6.conf.default.accept_ra kernel parameter, run the following command:
$ sudo sysctl -w net.ipv6.conf.default.accept_ra=0
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d:
net.ipv6.conf.default.accept_ra = 0
An illicit router advertisement message could result in a man-in-the-middle attack. CM-7(a)
CM-7(b)
CM-6(a)
CCE-82477-1 Disable Kernel Parameter for Accepting ICMP Redirects by Default on IPv6 Interfaces To set the runtime status of the net.ipv6.conf.default.accept_redirects kernel parameter, run the following command:
$ sudo sysctl -w net.ipv6.conf.default.accept_redirects=0
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d:
net.ipv6.conf.default.accept_redirects = 0
An illicit ICMP redirect message could result in a man-in-the-middle attack. CM-7(a)
CM-7(b)
CM-6(a)
CCE-82481-3 Disable Kernel Parameter for Accepting Source-Routed Packets on IPv6 Interfaces by Default To set the runtime status of the net.ipv6.conf.default.accept_source_route kernel parameter, run the following command:
$ sudo sysctl -w net.ipv6.conf.default.accept_source_route=0
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d:
net.ipv6.conf.default.accept_source_route = 0
Source-routed packets allow the source of the packet to suggest routers forward the packet along a different path than configured on the router, which can be used to bypass network security measures. This requirement applies only to the forwarding of source-routerd traffic, such as when IPv6 forwarding is enabled and the system is functioning as a router. Accepting source-routed packets in the IPv6 protocol has few legitimate uses. It should be disabled unless it is absolutely required. CM-7(a)
CM-7(b)
CM-6(a)
CCE-82503-4 Disable the use of user namespaces To set the runtime status of the user.max_user_namespaces kernel parameter, run the following command:
$ sudo sysctl -w user.max_user_namespaces=0
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d:
user.max_user_namespaces = 0
When containers are deployed on the machine, the value should be set to large non-zero value.
User namespaces are used primarily for Linux containers. The value 0 disallows the use of user namespaces. SC-39
CM-6(a)
CCE-82539-8 Authorize Human Interface Devices and USB hubs in USBGuard daemon To allow authorization of USB devices combining human interface device and hub capabilities by USBGuard daemon, add the line allow with-interface match_all { 03:*:* 09:00:* } to /etc/usbguard/rules.conf. Without allowing Human Interface Devices, it might not be possible to interact with the system. Without allowing hubs, it might not be possible to use any USB devices on the system.
Enable Auditing to Start Prior to the Audit Daemon in zIPL To ensure all processes can be audited, even those which start prior to the audit daemon, check that all boot entries in /boot/loader/entries/*.conf have audit=1 included in its options.
To ensure that new kernels and boot entries continue to enable audit, add audit=1 to /etc/kernel/cmdline.
Each process on the system carries an "auditable" flag which indicates whether its activities can be audited. Although auditd takes care of enabling this for all processes which launch after it does, adding the kernel argument ensures it is set for every process during boot.
Extend Audit Backlog Limit for the Audit Daemon in zIPL To improve the kernel capacity to queue all log events, even those which start prior to the audit daemon, check that all boot entries in /boot/loader/entries/*.conf have audit_backlog_limit=8192 included in its options.
To ensure that new kernels and boot entries continue to extend the audit log events queue, add audit_backlog_limit=8192 to /etc/kernel/cmdline.
audit_backlog_limit sets the queue length for audit events awaiting transfer to the audit daemon. Until the audit daemon is up and running, all log messages are stored in this queue. If the queue is overrun during boot process, the action defined by audit failure flag is taken.
Ensure all zIPL boot entries are BLS compliant Ensure that zIPL boot entries fully adheres to Boot Loader Specification (BLS) by checking that /etc/zipl.conf doesn't contain image = . Red Hat Enterprise Linux CoreOS 4 adheres to Boot Loader Specification (BLS) and is the prefered method of configuration.
Ensure zIPL bootmap is up to date Make sure that /boot/bootmap is up to date.
Every time a boot entry or zIPL configuration is changed /boot/bootmap needs to be updated to reflect the changes.
Run zipl command to generate an updated /boot/bootmap.
The file /boot/bootmap contains all boot data, keeping it up to date is crucial to boot correct kernel and options.
Enable page allocator poisoning in zIPL To enable poisoning of free pages, check that all boot entries in /boot/loader/entries/*.conf have page_poison=1 included in its options.
To ensure that new kernels and boot entries continue to enable page poisoning, add page_poison=1 to /etc/kernel/cmdline.
Poisoning writes an arbitrary value to freed pages, so any modification or reference to that page after being freed or before being initialized will be detected and prevented. This prevents many types of use-after-free vulnerabilities at little performance cost. Also prevents leak of data and detection of corrupted memory.
Enable SLUB/SLAB allocator poisoning in zIPL To enable poisoning of SLUB/SLAB objects, check that all boot entries in /boot/loader/entries/*.conf have slub_debug=P included in its options.
To ensure that new kernels and boot entries continue to enable poisoning of SLUB/SLAB objects, add slub_debug=P to /etc/kernel/cmdline.
Poisoning writes an arbitrary value to freed objects, so any modification or reference to that object after being freed or before being initialized will be detected and prevented. This prevents many types of use-after-free vulnerabilities at little performance cost. Also prevents leak of data and detection of corrupted memory.
Disable vsyscalls in zIPL To disable use of virtual syscalls, check that all boot entries in /boot/loader/entries/*.conf have vsyscall=none included in its options.
To ensure that new kernels and boot entries continue to disable virtual syscalls, add vsyscall=none to /etc/kernel/cmdline.
Virtual Syscalls provide an opportunity of attack for a user who has control of the return instruction pointer.