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Chapter 23. Postfix
Postfix is an open-source Mail Transport Agent (MTA), which supports protocols like LDAP, SMTP AUTH (SASL), and TLS.[22]
In Red Hat Enterprise Linux, the postfix package provides Postfix. Enter the following command to see if the postfix package is installed:
~]$ rpm -q postfix package postfix is not installed
~]$ rpm -q postfix
package postfix is not installed
If it is not installed, use the
yum utility root to install it:
~]# yum install postfix
~]# yum install postfix23.1. Postfix and SELinux
When Postfix is enabled, it runs confined by default. Confined processes run in their own domains, and are separated from other confined processes. If a confined process is compromised by an attacker, depending on SELinux policy configuration, an attacker's access to resources and the possible damage they can do is limited. The following example demonstrates the Postfix and related processes running in their own domain. This example assumes the postfix package is installed and that the Postfix service has been started:
- Run the
getenforcecommand to confirm SELinux is running in enforcing mode:~]$ getenforce Enforcing
Copy to clipboardCopied~]$ getenforce EnforcingThe command returnsEnforcingwhen SELinux is running in enforcing mode. - Enter the following command as the root user to start
postfix:~]# systemctl start postfix.service
Copy to clipboardCopied~]# systemctl start postfix.serviceConfirm that the service is running. The output should include the information below (only the time stamp will differ):~]# systemctl status postfix.service postfix.service - Postfix Mail Transport Agent Loaded: loaded (/usr/lib/systemd/system/postfix.service; disabled) Active: active (running) since Mon 2013-08-05 11:38:48 CEST; 3h 25min ago
Copy to clipboardCopied~]# systemctl status postfix.service postfix.service - Postfix Mail Transport Agent Loaded: loaded (/usr/lib/systemd/system/postfix.service; disabled) Active: active (running) since Mon 2013-08-05 11:38:48 CEST; 3h 25min ago - Run following command to view the
postfixprocesses:~]$ ps -eZ | grep postfix system_u:system_r:postfix_master_t:s0 1651 ? 00:00:00 master system_u:system_r:postfix_pickup_t:s0 1662 ? 00:00:00 pickup system_u:system_r:postfix_qmgr_t:s0 1663 ? 00:00:00 qmgr
Copy to clipboardCopied~]$ ps -eZ | grep postfix system_u:system_r:postfix_master_t:s0 1651 ? 00:00:00 master system_u:system_r:postfix_pickup_t:s0 1662 ? 00:00:00 pickup system_u:system_r:postfix_qmgr_t:s0 1663 ? 00:00:00 qmgrIn the output above, the SELinux context associated with the Postfixmasterprocess issystem_u:system_r:postfix_master_t:s0. The second last part of the context,postfix_master_t, is the type for this process. A type defines a domain for processes and a type for files. In this case, themasterprocess is running in thepostfix_master_tdomain.
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