Guide to the Secure Configuration of Red Hat Enterprise Linux 9
Rules, Groups, and Values defined within the XCCDF Benchmark
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Mount Remote Filesystems with nosuid
Add thenosuid
option to the fourth column of/etc/fstab
for the line which controls mounting of any NFS mounts.Rule Medium Severity -
Configure NFS Servers
The steps in this section are appropriate for systems which operate as NFS servers.Group -
Ensure All-Squashing Disabled On All Exports
The <code>all_squash</code> maps all uids and gids to an anonymous user. This should be disabled by removing any instances of the <code>all_squash<...Rule Low Severity -
Use Kerberos Security on All Exports
Using Kerberos on all exported mounts prevents a malicious client or user from impersonating a system user. To cryptography authenticate users to t...Rule Medium Severity -
Configure the Exports File Restrictively
Linux's NFS implementation uses the file <code>/etc/exports</code> to control what filesystems and directories may be accessed via NFS. (See the <c...Group -
Export Filesystems Read-Only if Possible
If a filesystem is being exported so that users can view the files in a convenient fashion, but there is no need for users to edit those files, exp...Group -
Use Access Lists to Enforce Authorization Restrictions
When configuring NFS exports, ensure that each export line in <code>/etc/exports</code> contains a list of hosts which are allowed to access that e...Group -
Vendor Approved Time pools
The list of vendor-approved pool serversValue -
Vendor Approved Time Servers
The list of vendor-approved time serversValue -
Maximum NTP or Chrony Poll
The maximum NTP or Chrony poll interval number in seconds specified as a power of two.Value -
The Chrony package is installed
System time should be synchronized between all systems in an environment. This is typically done by establishing an authoritative time server or se...Rule Medium Severity -
Install the ntp service
The ntpd service should be installed.Rule High Severity -
The Chronyd service is enabled
chrony is a daemon which implements the Network Time Protocol (NTP) is designed to synchronize system clocks across a variety of systems and use a ...Rule Medium Severity -
Enable the NTP Daemon
Thentp
service can be enabled with the following command:$ sudo systemctl enable ntp.service
Rule High Severity -
Enable the NTP Daemon
Thentpd
service can be enabled with the following command:$ sudo systemctl enable ntpd.service
Rule Medium Severity -
Disable chrony daemon from acting as server
The <code>port</code> option in <code>/etc/chrony.conf</code> can be set to <code>0</code> to make chrony daemon to never open any listening port f...Rule Low Severity -
Disable network management of chrony daemon
The <code>cmdport</code> option in <code>/etc/chrony.conf</code> can be set to <code>0</code> to stop chrony daemon from listening on the UDP port ...Rule Low Severity -
Uninstall xinetd Package
Thexinetd
package can be removed with the following command:$ sudo dnf erase xinetd
Rule Low Severity -
Configure Time Service Maxpoll Interval
The <code>maxpoll</code> should be configured to <xccdf-1.2:sub idref="xccdf_org.ssgproject.content_value_var_time_service_set_maxpoll" use="legacy...Rule Medium Severity -
Ensure that chronyd is running under chrony user account
chrony is a daemon which implements the Network Time Protocol (NTP). It is designed to synchronize system clocks across a variety of systems and us...Rule Medium Severity -
Ensure Chrony is only configured with the server directive
Check that Chrony only has time sources configured with theserver
directive.Rule Medium Severity -
A remote time server for Chrony is configured
<code>Chrony</code> is a daemon which implements the Network Time Protocol (NTP). It is designed to synchronize system clocks across a variety of s...Rule Medium Severity -
Specify Additional Remote NTP Servers
Additional NTP servers can be specified for time synchronization in the file <code>/etc/ntp.conf</code>. To do so, add additional lines of the fol...Rule Unknown Severity -
Specify a Remote NTP Server
To specify a remote NTP server for time synchronization, edit the file <code>/etc/ntp.conf</code>. Add or correct the following lines, substituting...Rule Medium Severity -
Obsolete Services
This section discusses a number of network-visible services which have historically caused problems for system security, and for which disabling or...Group -
Uninstall rsync Package
The rsyncd service can be used to synchronize files between systems over network links. The <code>rsync-daemon</code> package can be removed with t...Rule Medium Severity -
Ensure rsyncd service is disabled
Thersyncd
service can be disabled with the following command:$ sudo systemctl mask --now rsyncd.service
Rule Medium Severity -
Xinetd
The <code>xinetd</code> service acts as a dedicated listener for some network services (mostly, obsolete ones) and can be used to provide access co...Group -
Disable xinetd Service
Thexinetd
service can be disabled with the following command:$ sudo systemctl mask --now xinetd.service
Rule Medium Severity -
NIS
The Network Information Service (NIS), also known as 'Yellow Pages' (YP), and its successor NIS+ have been made obsolete by Kerberos, LDAP, and oth...Group -
Remove NIS Client
The Network Information Service (NIS), formerly known as Yellow Pages, is a client-server directory service protocol used to distribute system conf...Rule Unknown Severity -
Uninstall ypserv Package
Theypserv
package can be removed with the following command:$ sudo dnf erase ypserv
Rule High Severity -
Disable ypserv Service
The <code>ypserv</code> service, which allows the system to act as a client in a NIS or NIS+ domain, should be disabled. The <code>ypserv</code> s...Rule Medium Severity -
Rlogin, Rsh, and Rexec
The Berkeley r-commands are legacy services which allow cleartext remote access and have an insecure trust model.Group -
Uninstall rsh-server Package
Thersh-server
package can be removed with the following command:$ sudo dnf erase rsh-server
Rule High Severity -
Uninstall rsh Package
Thersh
package contains the client commands for the rsh servicesRule Unknown Severity -
Disable rlogin Service
The <code>rlogin</code> service, which is available with the <code>rsh-server</code> package and runs as a service through xinetd or separately as ...Rule High Severity -
Remove Host-Based Authentication Files
The <code>shosts.equiv</code> file lists remote hosts and users that are trusted by the local system. To remove these files, run the following comm...Rule High Severity -
Remove Rsh Trust Files
The files <code>/etc/hosts.equiv</code> and <code>~/.rhosts</code> (in each user's home directory) list remote hosts and users that are trusted by ...Rule High Severity -
Uninstall talk-server Package
Thetalk-server
package can be removed with the following command:$ sudo dnf erase talk-server
Rule Medium Severity -
Remove User Host-Based Authentication Files
The <code>~/.shosts</code> (in each user's home directory) files list remote hosts and users that are trusted by the local system. To remove these ...Rule High Severity -
Uninstall talk Package
The <code>talk</code> package contains the client program for the Internet talk protocol, which allows the user to chat with other users on differe...Rule Medium Severity -
Telnet
The telnet protocol does not provide confidentiality or integrity for information transmitted on the network. This includes authentication informat...Group -
Uninstall telnet-server Package
Thetelnet-server
package can be removed with the following command:$ sudo dnf erase telnet-server
Rule High Severity -
Remove telnet Clients
The telnet client allows users to start connections to other systems via the telnet protocol.Rule Low Severity -
Disable telnet Service
Make sure that the activation of the <code>telnet</code> service on system boot is disabled. The <code>telnet</code> socket can be disabled with t...Rule High Severity -
TFTP Server
TFTP is a lightweight version of the FTP protocol which has traditionally been used to configure networking equipment. However, TFTP provides littl...Group -
TFTP server secure directory
Specify the directory which is used by TFTP server as a root directory when running in secure mode.Value -
Uninstall tftp-server Package
Thetftp-server
package can be removed with the following command:$ sudo dnf erase tftp-server
Rule High Severity -
Remove tftp Daemon
Trivial File Transfer Protocol (TFTP) is a simple file transfer protocol, typically used to automatically transfer configuration or boot files betw...Rule Low Severity
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