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Guide to the Secure Configuration of Alibaba Cloud Linux 3

Rules, Groups, and Values defined within the XCCDF Benchmark

  • Vendor Approved Time Servers

    The list of vendor-approved time servers
    Value
    Show

  • 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 set of servers and having all systems synchronize th...
    Rule Medium Severity
    Show

  • Install the ntp service

    The ntpd service should be installed.
    Rule High Severity
    Show

  • 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 source that is highly accurate. More information o...
    Rule Medium Severity
    Show

  • 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 use a source that is highly accurate. More informati...
    Rule Medium Severity
    Show

  • Ensure Chrony is only configured with the server directive

    Check that Chrony only has time sources configured with the server directive.
    Rule Medium Severity
    Show

  • Obsolete Services

    This section discusses a number of network-visible services which have historically caused problems for system security, and for which disabling or severely limiting the service has been the best a...
    Group
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  • Ensure rsyncd service is disabled

    The rsyncd service can be disabled with the following command: 
    $ sudo systemctl mask --now rsyncd.service
    Rule Medium Severity
    Show

  • 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 controls and perform some logging. It has been large...
    Group
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  • Uninstall xinetd Package

    The xinetd package can be removed with the following command: 
    $ sudo yum erase xinetd
    Rule Low Severity
    Show

  • NIS

    The Network Information Service (NIS), also known as 'Yellow Pages' (YP), and its successor NIS+ have been made obsolete by Kerberos, LDAP, and other modern centralized authentication services. NIS...
    Group
    Show

  • Remove NIS Client

    The Network Information Service (NIS), formerly known as Yellow Pages, is a client-server directory service protocol used to distribute system configuration files. The NIS client (<code>ypbind</cod...
    Rule Unknown Severity
    Show

  • Telnet

    The telnet protocol does not provide confidentiality or integrity for information transmitted on the network. This includes authentication information such as passwords. Organizations which use tel...
    Group
    Show

  • Remove telnet Clients

    The telnet client allows users to start connections to other systems via the telnet protocol.
    Rule Low Severity
    Show

  • SSH Server

    The SSH protocol is recommended for remote login and remote file transfer. SSH provides confidentiality and integrity for data exchanged between two systems, as well as server authentication, throu...
    Group
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  • SSH session Idle time

    Specify duration of allowed idle time.
    Value
    Show

  • SSH Max authentication attempts

    Specify the maximum number of authentication attempts per connection.
    Value
    Show

  • SSH Max Sessions Count

    Specify the maximum number of open sessions permitted.
    Value
    Show

  • SSH Max Keep Alive Count

    Specify the maximum number of idle message counts before session is terminated.
    Value
    Show

  • Install the OpenSSH Server Package

    The openssh-server package should be installed. The openssh-server package can be installed with the following command: 
    $ sudo yum install openssh-server
    Rule Medium Severity
    Show

  • Remove the OpenSSH Server Package

    The openssh-server package should be removed. The openssh-server package can be removed with the following command: 
    $ sudo yum erase openssh-server
    Rule Medium Severity
    Show

  • Disable SSH Server If Possible

    The SSH server service, sshd, is commonly needed. However, if it can be disabled, do so. This is unusual, as SSH is a common method for encrypted and authenticated remote access.
    Rule High Severity
    Show

  • Verify Group Ownership on SSH Server Private *_key Key Files

    SSH server private keys, files that match the /etc/ssh/*_key glob, must be group-owned by root group.
    Rule Medium Severity
    Show

  • Verify Group Ownership on SSH Server Public *.pub Key Files

    SSH server public keys, files that match the /etc/ssh/*.pub glob, must be group-owned by root group.
    Rule Medium Severity
    Show

  • Verify Ownership on SSH Server Private *_key Key Files

    SSH server private keys, files that match the /etc/ssh/*_key glob, must be owned by root user.
    Rule Medium Severity
    Show

  • Verify Ownership on SSH Server Public *.pub Key Files

    SSH server public keys, files that match the /etc/ssh/*.pub glob, must be owned by root user.
    Rule Medium Severity
    Show

  • Verify Permissions on SSH Server Private *_key Key Files

    SSH server private keys - files that match the <code>/etc/ssh/*_key</code> glob, have to have restricted permissions. If those files are owned by the <code>root</code> user and the <code>root</code...
    Rule Medium Severity
    Show

  • Verify Permissions on SSH Server Public *.pub Key Files

    To properly set the permissions of /etc/ssh/*.pub, run the command: 
    $ sudo chmod 0644 /etc/ssh/*.pub
    Rule Medium Severity
    Show

  • Remove SSH Server iptables Firewall exception (Unusual)

    By default, inbound connections to SSH's port are allowed. If the SSH server is not being used, this exception should be removed from the firewall configuration. <br> <br> Edit the files <co...
    Rule Unknown Severity
    Show

  • Configure OpenSSH Server if Necessary

    If the system needs to act as an SSH server, then certain changes should be made to the OpenSSH daemon configuration file <code>/etc/ssh/sshd_config</code>. The following recommendations can be app...
    Group
    Show

  • SSH RekeyLimit - size

    Specify the size component of the rekey limit.
    Value
    Show

  • SSH RekeyLimit - size

    Specify the size component of the rekey limit.
    Value
    Show

  • SSH Compression Setting

    Specify the compression setting for SSH connections.
    Value
    Show

  • SSH Privilege Separation Setting

    Specify whether and how sshd separates privileges when handling incoming network connections.
    Value
    Show

  • SSH LoginGraceTime setting

    Configure parameters for how long the servers stays connected before the user has successfully logged in
    Value
    Show

  • SSH MaxStartups setting

    Configure parameters for maximum concurrent unauthenticated connections to the SSH daemon.
    Value
    Show

  • Set SSH Client Alive Count Max to zero

    The SSH server sends at most <code>ClientAliveCountMax</code> messages during a SSH session and waits for a response from the SSH client. The option <code>ClientAliveInterval</code> configures time...
    Rule Medium Severity
    Show

  • Set SSH Client Alive Count Max

    The SSH server sends at most <code>ClientAliveCountMax</code> messages during a SSH session and waits for a response from the SSH client. The option <code>ClientAliveInterval</code> configures time...
    Rule Medium Severity
    Show

  • Disable Host-Based Authentication

    SSH's cryptographic host-based authentication is more secure than <code>.rhosts</code> authentication. However, it is not recommended that hosts unilaterally trust one another, even within an organ...
    Rule Medium Severity
    Show

  • Allow Only SSH Protocol 2

    Only SSH protocol version 2 connections should be permitted. The default setting in <code>/etc/ssh/sshd_config</code> is correct, and can be verified by ensuring that the following line appears: <p...
    Rule High Severity
    Show

  • Disable Compression Or Set Compression to delayed

    Compression is useful for slow network connections over long distances but can cause performance issues on local LANs. If use of compression is required, it should be enabled only after a user has ...
    Rule Medium Severity
    Show

  • Disable GSSAPI Authentication

    Unless needed, SSH should not permit extraneous or unnecessary authentication mechanisms like GSSAPI. <br> The default SSH configuration disallows authentications based on GSSAPI. The appropriate c...
    Rule Medium Severity
    Show

  • Disable Kerberos Authentication

    Unless needed, SSH should not permit extraneous or unnecessary authentication mechanisms like Kerberos. <br> The default SSH configuration disallows authentication validation through Kerberos. The ...
    Rule Medium Severity
    Show

  • Disable PubkeyAuthentication Authentication

    Unless needed, SSH should not permit extraneous or unnecessary authentication mechanisms. To disable PubkeyAuthentication authentication, add or correct the following line in <code>/etc/ssh/sshd_...
    Rule Medium Severity
    Show

  • Disable SSH Support for Rhosts RSA Authentication

    SSH can allow authentication through the obsolete rsh command through the use of the authenticating user's SSH keys. This should be disabled. <br> <br> To ensure this behavior is disabled, ...
    Rule Medium Severity
    Show

  • 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 <code>/etc/ssh/sshd_config</code>: <pre>Pe...
    Rule Medium Severity
    Show

  • Disable SSH root Login with a Password (Insecure)

    To disable password-based root logins over SSH, add or correct the following line in /etc/ssh/sshd_config: 
    PermitRootLogin prohibit-password
    Rule Medium Severity
    Show

  • Disable SSH TCP Forwarding

    The <code>AllowTcpForwarding</code> parameter specifies whether TCP forwarding is permitted. To disable TCP forwarding, add or correct the following line in <code>/etc/ssh/sshd_config</code>: <p...
    Rule Medium Severity
    Show

  • Disable SSH Support for User Known Hosts

    SSH can allow system users to connect to systems if a cache of the remote systems public keys is available. This should be disabled. <br> <br> To ensure this behavior is disabled, add or c...
    Rule Medium Severity
    Show

  • Do Not Allow SSH Environment Options

    Ensure that users are not able to override environment variables of the SSH daemon. <br> The default SSH configuration disables environment processing. The appropriate configuration is used if no v...
    Rule Medium Severity
    Show

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