Guide to the Secure Configuration of Oracle Linux 7
Rules, Groups, and Values defined within the XCCDF Benchmark
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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 -
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 -
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 -
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 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 -
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 sub...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,nfs...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 fil...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, a...Group -
Disable rpcbind Service
The rpcbind utility maps RPC services to the ports on which they listen. RPC processes notify rpcbind when they start, registering the ports they a...Rule Low Severity -
Configure All Systems which Use NFS
The steps in this section are appropriate for all systems which run NFS, whether they operate as clients or as servers.Group -
SSH MaxStartups setting
Configure parameters for maximum concurrent unauthenticated connections to the SSH daemon.Value -
Make Each System a Client or a Server, not Both
If NFS must be used, it should be deployed in the simplest configuration possible to avoid maintainability problems which may lead to unnecessary s...Group -
Configure NFS Services to Use Fixed Ports (NFSv3 and NFSv2)
Firewalling should be done at each host and at the border firewalls to protect the NFS daemons from remote access, since NFS servers should never b...Group -
Configure NFS Clients
The steps in this section are appropriate for systems which operate as NFS clients.Group -
Disable NFS Server Daemons
There is no need to run the NFS server daemons <code>nfs</code> and <code>rpcsvcgssd</code> except on a small number of properly secured systems de...Group -
Mount Remote Filesystems with Restrictive Options
Edit the file <code>/etc/fstab</code>. For each filesystem whose type (column 3) is <code>nfs</code> or <code>nfs4</code>, add the text <code>,node...Group -
Mount Remote Filesystems with Kerberos Security
Add the <code>sec=krb5:krb5i:krb5p</code> option to the fourth column of <code>/etc/fstab</code> for the line which controls mounting of any NFS mo...Rule Medium Severity -
Mount Remote Filesystems with nodev
Add thenodevoption to the fourth column of/etc/fstabfor the line which controls mounting of any NFS mounts.Rule Medium Severity -
Mount Remote Filesystems with noexec
Add thenoexecoption to the fourth column of/etc/fstabfor the line which controls mounting of any NFS mounts.Rule Medium Severity -
Mount Remote Filesystems with nosuid
Add thenosuidoption to the fourth column of/etc/fstabfor 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 -
Remote Authentication Dial-In User Service (RADIUS)
Remote Authentication Dial-In User Service (RADIUS) is a networking protocol, operating on port 1812 that provides centralized Authentication, Auth...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 -
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 unpredictabl...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
Run the following command to determine the current status of the <code>chronyd</code> service: <pre>$ sudo systemctl is-active chronyd</pre> If t...Rule Medium Severity
Node 2
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