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Guide to the Secure Configuration of Alibaba Cloud Linux 2

Rules, Groups, and Values defined within the XCCDF Benchmark

  • Verify User Who Owns /etc/cron.allow file

    If <code>/etc/cron.allow</code> exists, it must be owned by <code>root</code>. To properly set the owner of <code>/etc/cron.allow</code>, run the command: <pre>$ sudo chown root /etc/cron.allow </...
    Rule Medium Severity
  • Verify Permissions on /etc/at.allow file

    If <code>/etc/at.allow</code> exists, it must have permissions <code>0640</code> or more restrictive. To properly set the permissions of <code>/etc/at.allow</code>, run the command: <pre>$ sudo c...
    Rule Medium Severity
  • Verify Permissions on /etc/cron.allow file

    If <code>/etc/cron.allow</code> exists, it must have permissions <code>0640</code> or more restrictive. To properly set the permissions of <code>/etc/cron.allow</code>, run the command: <pre>$ su...
    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 ntpdate package

    ntpdate is a historical ntp synchronization client for unixes. It sould be uninstalled.
    Rule Low Severity
  • Uninstall the ssl compliant telnet server

    The telnet daemon, even with ssl support, should be uninstalled.
    Rule High Severity
  • Uninstall the telnet server

    The telnet daemon should be uninstalled.
    Rule High Severity
  • 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
  • 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
  • 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 Alibaba Cloud Linux 2 by default. The remainder of ...
    Group
  • Uninstall bind Package

    The named service is provided by the bind package. The bind package can be removed with the following command:
    $ sudo yum erase bind
    Rule Low Severity
  • 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
  • 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
  • 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
  • Restrict the Set of Users Allowed to Access FTP

    This section describes how to disable non-anonymous (password-based) FTP logins, or, if it is not possible to do this entirely due to legacy applications, how to restrict insecure FTP login to only...
    Group
  • Limit Users Allowed FTP Access if Necessary

    If there is a mission-critical reason for users to access their accounts via the insecure FTP protocol, limit the set of users who are allowed this access. Edit the vsftpd configuration file. Add o...
    Rule Unknown Severity
  • LDAP

    LDAP is a popular directory service, that is, a standardized way of looking up information from a central database. Alibaba Cloud Linux 2 includes software that enables a system to act as both an L...
    Group
  • Configure OpenLDAP Clients

    This section provides information on which security settings are important to configure in OpenLDAP clients by manually editing the appropriate configuration files. Alibaba Cloud Linux 2 provides ...
    Group
  • Disable Postfix Network Listening

    Edit the file <code>/etc/postfix/main.cf</code> to ensure that only the following <code>inet_interfaces</code> line appears: <pre>inet_interfaces = <xccdf-1.2:sub idref="xccdf_org.ssgproject.conten...
    Rule Medium 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 the IP or hostname of a remote NTP server for <em...
    Rule Medium Severity
  • The Postfix package is installed

    A mail server is required for sending emails. The postfix package can be installed with the following command:
    $ sudo yum install postfix
    Rule Medium Severity
  • Enable Postfix Service

    The Postfix mail transfer agent is used for local mail delivery within the system. The default configuration only listens for connections to the default SMTP port (port 25) on the loopback interfac...
    Rule Unknown Severity
  • Configure SMTP For Mail Clients

    This section discusses settings for Postfix in a submission-only e-mail configuration.
    Group
  • Postfix Network Interfaces

    The setting for inet_interfaces in /etc/postfix/main.cf
    Value
  • Postfix relayhost

    Specify the host all outbound email should be routed into.
    Value
  • Postfix Root Mail Alias

    Specify an email address (string) for a root mail alias.
    Value
  • Configure System to Forward All Mail For The Root Account

    Make sure that mails delivered to root user are forwarded to a monitored email address. Make sure that the address <xccdf-1.2:sub idref="xccdf_org.ssgproject.content_value_var_postfix_root_mail_ali...
    Rule Medium Severity
  • NFS and RPC

    The Network File System is a popular distributed filesystem for the Unix environment, and is very widely deployed. This section discusses the circumstances under which it is possible to disable NF...
    Group
  • 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
  • Disable netfs if Possible

    To determine if any network filesystems handled by netfs are currently mounted on the system execute the following command: <pre>$ mount -t nfs,nfs4,smbfs,cifs,ncpfs</pre> If the command did not re...
    Group
  • Disable Network File Systems (netfs)

    The netfs script manages the boot-time mounting of several types of networked filesystems, of which NFS and Samba are the most common. If these filesystem types are not in use, the script can be di...
    Rule Unknown Severity
  • Disable Services Used Only by NFS

    If NFS is not needed, disable the NFS client daemons nfslock, rpcgssd, and rpcidmapd. <br> <br> All of these daemons run with elevated privileges, and many listen for network connections. I...
    Group
  • 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</code> option from the file <code>/etc/exports</co...
    Rule Low Severity
  • Network Time Protocol

    The Network Time Protocol is used to manage the system clock over a network. Computer clocks are not very accurate, so time will drift unpredictably on unmanaged systems. Central time protocols can...
    Group
  • Vendor Approved Time Servers

    The list of vendor-approved time servers
    Value
  • 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 source that is highly accurate. More information o...
    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 use a source that is highly accurate. More informati...
    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 systems and use a source that is highly accurate. M...
    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
  • 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
  • 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
  • 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 Package

    The rsh package contains the client commands for the rsh services
    Rule Unknown Severity
  • Chat/Messaging Services

    The talk software makes it possible for users to send and receive messages across systems through a terminal session.
    Group

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