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Guide to the Secure Configuration of Red Hat Enterprise Linux 9

Rules, Groups, and Values defined within the XCCDF Benchmark

  • Mount Remote Filesystems with nosuid

    Add the nosuid 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 servers
    Value
  • Vendor Approved Time Servers

    The list of vendor-approved time servers
    Value
  • 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

    The ntp service can be enabled with the following command:
    $ sudo systemctl enable ntp.service
    Rule High Severity
  • Enable the NTP Daemon

    The ntpd 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

    The xinetd 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 the server 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

    The rsyncd 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

    The xinetd 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

    The ypserv 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

    The rsh-server package can be removed with the following command:
    $ sudo dnf erase rsh-server
    Rule High Severity
  • Uninstall rsh Package

    The rsh package contains the client commands for the rsh services
    Rule 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

    The talk-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

    The telnet-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

    The tftp-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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