Guide to the Secure Configuration of Red Hat Enterprise Linux 7
Rules, Groups, and Values defined within the XCCDF Benchmark
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Configure Dovecot if Necessary
If the system will operate as an IMAP or POP3 server, the dovecot software should be configured securely by following the recommendations below.Group -
Enable SSL Support
SSL should be used to encrypt network traffic between the Dovecot server and its clients. Users must authenticate to the Dovecot server in order ...Group -
Uninstall Sendmail Package
Sendmail is not the default mail transfer agent and is not installed by default. The <code>sendmail</code> package can be removed with the followin...Rule Medium Severity -
Configure Dovecot to Use the SSL Certificate file
This option tells Dovecot where to find the mail server's SSL Certificate. <br><br> Edit <code>/etc/dovecot/conf.d/10-ssl.conf</code> and add or co...Rule Unknown Severity -
Configure Dovecot to Use the SSL Key file
This option tells Dovecot where to find the mail server's SSL Key. <br><br> Edit <code>/etc/dovecot/conf.d/10-ssl.conf</code> and add or correct th...Rule Unknown Severity -
Disable Plaintext Authentication
To prevent Dovecot from attempting plaintext authentication of clients, edit <code>/etc/dovecot/conf.d/10-auth.conf</code> and add\or correct the f...Rule Unknown Severity -
Enable the SSL flag in /etc/dovecot.conf
To allow clients to make encrypted connections the <code>ssl</code> flag in Dovecot's configuration file needs to be set to <code>yes</code>. <br><...Rule Unknown Severity -
Support Only the Necessary Protocols
Dovecot supports the IMAP and POP3 protocols, as well as SSL-protected versions of those protocols. Configure the Dovecot server to support only ...Group -
Disable Cyrus IMAP
If the system does not need to operate as an IMAP or POP3 server, the Cyrus IMAP software should be removed.Group -
Disable Dovecot
If the system does not need to operate as an IMAP or POP3 server, the dovecot software should be disabled and removed.Group -
Uninstall dovecot Package
Thedovecotpackage can be removed with the following command:$ sudo yum erase dovecot
Rule Unknown Severity -
Disable Dovecot Service
Thedovecotservice can be disabled with the following command:$ sudo systemctl mask --now dovecot.service
Rule Unknown Severity -
Kerberos
The Kerberos protocol is used for authentication across non-secure network. Authentication can happen between various types of principals -- users,...Group -
Remove the Kerberos Server Package
The <code>krb5-server</code> package should be removed if not in use. Is this system the Kerberos server? If not, remove the package. The <code>krb...Rule Medium Severity -
Disable Kerberos by removing host keytab
Kerberos is not an approved key distribution method for Common Criteria. To prevent using Kerberos by system daemons, remove the Kerberos keytab fi...Rule Medium Severity -
LDAP
LDAP is a popular directory service, that is, a standardized way of looking up information from a central database. Red Hat Enterprise Linux 7 incl...Group -
Configure OpenLDAP Clients
This section provides information on which security settings are important to configure in OpenLDAP clients by manually editing the appropriate con...Group -
Ensure LDAP client is not installed
The Lightweight Directory Access Protocol (LDAP) is a service that provides a method for looking up information from a central database. The <code>...Rule Low Severity -
Enable the LDAP Client For Use in Authconfig
To determine if LDAP is being used for authentication, use the following command: <pre>$ sudo grep -i useldapauth /etc/sysconfig/authconfig</pre> <...Rule Medium Severity -
Configure LDAP Client to Use TLS For All Transactions
This check verifies cryptography has been implemented to protect the integrity of remote LDAP authentication sessions. <br><br> To determine if LDA...Rule Medium Severity -
Configure Certificate Directives for LDAP Use of TLS
Ensure a copy of a trusted CA certificate has been placed in the file <code>/etc/pki/tls/CA/cacert.pem</code>. Configure LDAP to enforce TLS use an...Rule Medium Severity -
Configure OpenLDAP Server
This section details some security-relevant settings for an OpenLDAP server. Installation and configuration of OpenLDAP on Red Hat Enterprise Linu...Group -
Uninstall openldap-servers Package
The openldap-servers package is not installed by default on a Red Hat Enterprise Linux 7 system. It is needed only by the OpenLDAP server, not by t...Rule Low Severity -
Install and Protect LDAP Certificate Files
Create the PKI directory for LDAP certificates if it does not already exist: <pre>$ sudo mkdir /etc/pki/tls/ldap $ sudo chown root:root /etc/pki/tl...Group -
Mail Server Software
Mail servers are used to send and receive email over the network. Mail is a very common service, and Mail Transfer Agents (MTAs) are obvious target...Group -
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 de...Rule Unknown Severity -
Ensure Mail Transfer Agent is not Listening on any non-loopback Address
Mail Transfer Agents (MTA), such as sendmail and Postfix, are used to listen for incoming mail and transfer the messages to the appropriate user or...Rule Medium 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.cfValue -
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....Rule Medium Severity -
Configure System to Forward All Mail From Postmaster to The Root Account
Verify the administrators are notified in the event of an audit processing failure. Check that the "/etc/aliases" file has a defined value for "roo...Rule Medium Severity -
Configure System to Forward All Mail through a specific host
Set up a relay host that will act as a gateway for all outbound email. Edit the file <code>/etc/postfix/main.cf</code> to ensure that only the foll...Rule Medium Severity -
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 =...Rule Medium Severity -
Configure Operating System to Protect Mail Server
The guidance in this section is appropriate for any host which is operating as a site MTA, whether the mail server runs using Sendmail, Postfix, or...Group -
Configure SSL Certificates for Use with SMTP AUTH
If SMTP AUTH is to be used, the use of SSL to protect credentials in transit is strongly recommended. There are also configurations for which it ma...Group -
Ensure Security of Postfix SSL Certificate
Create the PKI directory for mail certificates, if it does not already exist: <pre>$ sudo mkdir /etc/pki/tls/mail $ sudo chown root:root /etc/pki/t...Group -
Configure Postfix if Necessary
Postfix stores its configuration files in the directory /etc/postfix by default. The primary configuration file is/etc/postfix/main.cf.Group -
Configure SMTP Greeting Banner
Edit <code>/etc/postfix/main.cf</code>, and add or correct the following line, substituting some other wording for the banner information if you pr...Rule Low Severity -
Configure Postfix Resource Usage to Limit Denial of Service Attacks
Edit <code>/etc/postfix/main.cf</code>. Edit the following lines to configure the amount of system resources Postfix can consume: <pre>default_proc...Group -
Control Mail Relaying
Postfix's mail relay controls are implemented with the help of the smtpd recipient restrictions option, which controls the restrictions placed on t...Group -
Prevent Unrestricted Mail Relaying
Modify the <pre>/etc/postfix/main.cf</pre> file to restrict client connections to the local network with the following command: <pre>$ sudo postcon...Rule Medium Severity -
Enact SMTP Recipient Restrictions
To configure Postfix to restrict addresses to which it will send mail, see: <a href="http://www.postfix.org/SMTPD_ACCESS_README.html#danger">h...Group -
Enact SMTP Relay Restrictions
To configure Postfix to restrict addresses to which it will send mail, see: <a href="http://www.postfix.org/SMTPD_ACCESS_README.html#danger">h...Group -
Use TLS for SMTP AUTH
Postfix provides options to use TLS for certificate-based authentication and encrypted sessions. An encrypted session protects the information that...Group -
Configure Trusted Networks and Hosts
Edit <code>/etc/postfix/main.cf</code>, and configure the contents of the <code>mynetworks</code> variable in one of the following ways: <ul> <li>I...Group -
Require SMTP AUTH Before Relaying from Untrusted Clients
SMTP authentication allows remote clients to relay mail safely by requiring them to authenticate before submitting mail. Postfix's SMTP AUTH uses a...Group -
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 circ...Group -
Uninstall nfs-utils Package
Thenfs-utilspackage can be removed with the following command:$ sudo yum erase nfs-utils
Rule Low Severity
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