Guide to the Secure Configuration of Red Hat Enterprise Linux CoreOS 4
Rules, Groups, and Values defined within the XCCDF Benchmark
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Disable storing core dump
TheStorage
option in[Coredump]
sectionof/etc/systemd/coredump.conf
can be set tonone
to disable storing core dumps permanently.Rule Medium Severity -
Disable Core Dumps for All Users
To disable core dumps for all users, add the following line to <code>/etc/security/limits.conf</code>, or to a file within the <code>/etc/security/limits.d/</code> directory: <pre>* hard core...Rule Medium Severity -
Disable Core Dumps for SUID programs
To set the runtime status of the <code>fs.suid_dumpable</code> kernel parameter, run the following command: <pre>$ sudo sysctl -w fs.suid_dumpable=0</pre> To make sure that the setting is persisten...Rule Medium Severity -
Enable ExecShield
ExecShield describes kernel features that provide protection against exploitation of memory corruption errors such as buffer overflows. These features include random placement of the stack and othe...Group -
kernel.kptr_restrict
Configure exposition of kernel pointer addressesValue -
Enable Randomized Layout of Virtual Address Space
To set the runtime status of the <code>kernel.randomize_va_space</code> kernel parameter, run the following command: <pre>$ sudo sysctl -w kernel.randomize_va_space=2</pre> To make sure that the se...Rule Medium Severity -
Enable Execute Disable (XD) or No Execute (NX) Support on x86 Systems
Recent processors in the x86 family support the ability to prevent code execution on a per memory page basis. Generically and on AMD processors, this ability is called No Execute (NX), while on Int...Group -
Enable NX or XD Support in the BIOS
Reboot the system and enter the BIOS or Setup configuration menu. Navigate the BIOS configuration menu and make sure that the option is enabled. The setting may be located under a Security section....Rule Medium Severity -
Memory Poisoning
Memory Poisoning consists of writing a special value to uninitialized or freed memory. Poisoning can be used as a mechanism to prevent leak of information and detection of corrupted memory.Group -
slub_debug - debug options
Defines the debug options to use inslub_debug
kernel command line argument.Value -
Enable page allocator poisoning
To enable poisoning of free pages, add the argument <code>page_poison=1</code> to all BLS (Boot Loader Specification) entries ('options' line) for the Linux operating system in <code>/boot/loader/e...Rule Medium Severity -
Enable SLUB/SLAB allocator poisoning
To enable poisoning of SLUB/SLAB objects, add the argument <code>slub_debug=P</code> to all BLS (Boot Loader Specification) entries ('options' line) for the Linux operating system in <code>/boot/lo...Rule Medium Severity -
SELinux policy
Type of policy in use. Possible values are:
targeted - Only targeted network daemons are protected.
strict - Full SELinux protection.
mls - Multiple levels of securityValue -
SELinux state
enforcing - SELinux security policy is enforced.
permissive - SELinux prints warnings instead of enforcing.
disabled - SELinux is fully disabled.Value -
Uninstall setroubleshoot-plugins Package
The SETroubleshoot plugins are used to analyze SELinux AVC data. The service provides information around configuration errors, unauthorized intrusions, and other potential errors. The <code>setroub...Rule Low Severity -
Uninstall setroubleshoot-server Package
The SETroubleshoot service notifies desktop users of SELinux denials. The service provides information around configuration errors, unauthorized intrusions, and other potential errors. The <code>se...Rule Low Severity -
Ensure SELinux Not Disabled in the kernel arguments
SELinux can be disabled at boot time by disabling it via a kernel argument. Remove any instances of <code>selinux=0</code> from the kernel arguments in that file to prevent SELinux from being disab...Rule Medium Severity -
Ensure SELinux Not Disabled in /etc/default/grub
SELinux can be disabled at boot time by an argument in <code>/etc/default/grub</code>. Remove any instances of <code>selinux=0</code> from the kernel arguments in that file to prevent SELinux from ...Rule Medium Severity -
Ensure No Daemons are Unconfined by SELinux
Daemons for which the SELinux policy does not contain rules will inherit the context of the parent process. Because daemons are launched during startup and descend from the <code>init</code> proces...Rule Medium Severity -
Ensure SELinux is Not Disabled
The SELinux state should be set to <code>enforcing</code> or <code>permissive</code> at system boot time. In the file <code>/etc/selinux/config</code>, add or correct the following line to configur...Rule High Severity -
Configure SELinux Policy
The SELinux <code>targeted</code> 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 ...Rule Medium Severity -
SELinux - Booleans
Enable or Disable runtime customization of SELinux system policies without having to reload or recompile the SELinux policy.Group -
deny_execmem SELinux Boolean
default - Default SELinux boolean setting.
on - SELinux boolean is enabled.
off - SELinux boolean is disabled.Value -
polyinstantiation_enabled SELinux Boolean
default - Default SELinux boolean setting.
on - SELinux boolean is enabled.
off - SELinux boolean is disabled.Value -
secure_mode_insmod SELinux Boolean
default - Default SELinux boolean setting.
on - SELinux boolean is enabled.
off - SELinux boolean is disabled.Value -
selinuxuser_execheap SELinux Boolean
default - Default SELinux boolean setting.
on - SELinux boolean is enabled.
off - SELinux boolean is disabled.Value -
selinuxuser_execstack SELinux Boolean
default - Default SELinux boolean setting.
on - SELinux boolean is enabled.
off - SELinux boolean is disabled.Value -
Disable All NFS Services if Possible
If there is not a reason for the system to operate as either an NFS client or an NFS server, follow all instructions in this section to disable subsystems required by NFS.Group -
Avahi Server
The Avahi daemon implements the DNS Service Discovery and Multicast DNS protocols, which provide service and host discovery on a network. It allows a system to automatically identify resources on t...Group -
Configure Avahi if Necessary
If your system requires the Avahi daemon, its configuration can be restricted to improve security. The Avahi daemon configuration file is <code>/etc/avahi/avahi-daemon.conf</code>. The following se...Group -
Disable Avahi Publishing
To prevent Avahi from publishing its records, edit <code>/etc/avahi/avahi-daemon.conf</code> and ensure the following line appears in the <code>[publish]</code> section: <pre>disable-publishing=yes...Rule Low Severity -
Cron and At Daemons
The cron and at services are used to allow commands to be executed at a later time. The cron service is required by almost all systems to perform necessary maintenance tasks, while at may or may no...Group -
Install the cron service
The Cron service should be installed.Rule Medium Severity -
Deprecated services
Some deprecated software services impact the overall system security due to their behavior (leak of confidentiality in network exchange, usage as uncontrolled communication channel, risk associated...Group -
Uninstall the inet-based telnet server
The inet-based telnet daemon should be uninstalled.Rule High Severity -
Uninstall the nis package
The support for Yellowpages should not be installed unless it is required.Rule Low Severity -
Uninstall the ntpdate package
ntpdate is a historical ntp synchronization client for unixes. It sould be uninstalled.Rule Low Severity -
Uninstall the ssl compliant telnet server
Thetelnet
daemon, even with ssl support, should be uninstalled.Rule High Severity -
Uninstall the telnet server
The telnet daemon should be uninstalled.Rule High Severity -
DHCP
The Dynamic Host Configuration Protocol (DHCP) allows systems to request and obtain an IP address and other configuration parameters from a server. <br> <br> This guide recommends configuring...Group -
Configure DHCP Client if Necessary
If DHCP must be used, then certain configuration changes can minimize the amount of information it receives and applies from the network, and thus the amount of incorrect information a rogue DHCP s...Group -
Application Whitelisting Daemon
Fapolicyd (File Access Policy Daemon) implements application whitelisting to decide file access rights. Applications that are known via a reputation source are allowed access while unknown applicat...Group -
Configure DHCP Server
If the system must act as a DHCP server, the configuration information it serves should be minimized. Also, support for other protocols and DNS-updating schemes should be explicitly disabled unless...Group -
Minimize Served Information
Edit /etc/dhcp/dhcpd.conf. Examine each address range section within the file, and ensure that the following options are not defined unless there is an operational need to provide this information ...Rule Unknown Severity -
Disable DHCP Server
The DHCP server <code>dhcpd</code> is not installed or activated by default. If the software was installed and activated, but the system does not need to act as a DHCP server, it should be disabled...Group -
DNS Server
Most organizations have an operational need to run at least one nameserver. However, there are many common attacks involving DNS server software, and this server software should be disabled on any ...Group -
Disable DNS Server
DNS software should be disabled on any systems which does not need to be a nameserver. Note that the BIND DNS server software is not installed on Red Hat Enterprise Linux CoreOS 4 by default. The r...Group -
fapolicyd Must be Configured to Limit Access to Users Home Folders
fapolicyd needs be configured so that users cannot give access to their home folders to other users.Rule Medium Severity -
FTP Server
FTP is a common method for allowing remote access to files. Like telnet, the FTP protocol is unencrypted, which means that passwords and other data transmitted during the session can be captured an...Group -
Configure vsftpd to Provide FTP Service if Necessary
The primary vsftpd configuration file is/etc/vsftpd.conf
, if that file exists, or/etc/vsftpd/vsftpd.conf
if it does not.Group
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