Category Archives: Red Hat

Securing email to Gmail

I’ve been working on securing my postfix configuration to enforce certificate validation and encryption on some known, higher-volume, or more sensitive connections between SMTP servers (port 25).

On many of the connections I’ve setup for secure transport there have been no problems (assuming proper TLS certificates are used).  Unfortunately Gmail™ has been a problem.  Sometimes it verifies and validates the certificate and other times it doesn’t… for days.

After conferring with Google Security I believe I’ve come up with a solution.  In my tls_policy file I’ve added the following:       secure ciphers=high protocols=TLSv1.2

So far this is working but I’ll continue to test.

If you run your own SMTP server and wish to maintain a secure connection with Gmail this is an easy way to enforce encryption as well as validate the certificate.  Of course this doesn’t protect the message while it’s being stored on the server or workstation (or on Google’s internal network).  To protect messages at rest (on a server) one should use GPG or S/MIME.  Using both TLS over the network between servers and GPG or S/MIME is beneficial to provide protection of the messages going over the Internet.


This configuration is applicable with the OpenSSL version shipped with CentOS 6/RHEL 6.  Implementing this on CentOS 7/RHEL7 or another flavor of Linux may require a different/better configuration.
The policy has been updated for CentOS 7/RHEL 7 which supports TLSv1.2 on Postfix.  Other services can also be setup similarly:    secure ciphers=high protocols=TLSv1.2    secure ciphers=high protocols=TLSv1.2    secure ciphers=high protocols=TLSv1.2    secure ciphers=high protocols=TLSv1.2

Starting work at Red Hat

I’m excited.  Earlier this week I accepted a position at Red Hat working on a very cool project that has the ability to affect many open source, and not so open source, projects in a very positive way.  The opportunity that I was presented was too good to turn away.  The best part is, aside from never having to touch a Windows box again, that I get to continue my work and studies in security and bring this project to the world in an open source way.

There is a lot of work that needs to be done and I hope to spread the wealth of information and goodness to the masses in a few short months.  I won’t say much about the project now but I will be writing about my work after I start in early January.  Stay tuned.