cat /dev/DiBona/brain: What About E-mail Security?

Ever used driftnet? I go to a lot of conferences, and one thing I find
myself doing while speaking is checking how engaged the audience is by
sniffing the 802.11b traffic in the room. Whether this is a measure of how
absorbing I am or, to put it delicately, how self-absorbed the conference
attendee is, is an open question. That said, it always is surprising to me
how little encrypted traffic is flowing on the very open Internet.

Does anyone use Telnet anymore? I hope not. We have better tools now; SSH
and SCP are the way most sane people hop around systems on which they might have
accounts. In addition, the days of unreliable and patent-encumbered SSH
are gone, and we now have the luxury of using OpenSSH for shelling around.

For Web browsing, no one in his or her right mind would transmit important
information over an insecure link. Secure sites for bank, shopping and
other applications are the norm, with poorly secured sites being
exceptions.

One mode of communicating over the Internet, however, is done shockingly,
overwhelmingly in the clear. I'm talking about e-mail. It doesn't have
to be this way, though. With all the excitement about SPF and other mail
authentication methods, it struck me that people haven't done even the
base work to secure their communications--myself included. If one can
eavesdrop on communications, one can spoof those communications. In my
mind, authentication schemes are going to be of dubious value without an
attendant amount of effort spent securing the line as well.

Hence this article. TLS is a great way to do the basics of securing your
e-mail against this very basic kind of snooping. You can use the same
certificates you use to secure your Web site. Many people find using
unsigned certificates works okay too, although it offers no guarantees
for security or reliability regarding the exchange of mail.

TLS is an acronym for Transport Layer Security, and it simply encrypts
your mail server to mail server traffic with other TLS-enabled sites. I
recently implemented this for a client site and thought it really was
in my interest to implement it for my personal e-mail, as well. So I decided
to implement it on DiBona.com.

I made a quick trip to
FreeSSL.com to pick up a certificate. Thirty-nice dollars
and an automated phone call later, I had it. I highly recommend FreeSSL.
Clear instructions on how to create the certificate on any competently setup
Linux box, straightforward processes and a smart phone system make for a
great way to get a solid certificate without any worries. FreeSSL has terrific
phone support as well, in the event you make a mistake or need a little bit
more hand holding, as I did for a chained certificate some months ago.

I ran this article by Uriah Welcome and Marc Merlin. Marc reminded me that
you don't have to get a signed certificate, as most mail systems are
configured to not care so much about the chain of trust. If you think
about it, when your chain of trust ends at network solutions, it's not so
trustworthy, but let's not go there. Uriah wanted me to make sure that
people don't forget to protect the certificate files properly, don't chmod
666 then and so on.

Setting up TLS with your mail server can be difficult, depending on your
setup. An exim installation is too simple for words. Once you have
generated the key, you simply need to add the following three lines to
the top of you exim.conf file:

tls_certificate = /pathtocert/dibona.crt
tls_privatekey = /pathtokey /dibona.key
tls_advertise_hosts = *

Please note that I used the exim-exiscan rpm.

For Sendmail users, here is an oldish
Linux
Journal article on the topic;
I haven't installed it yet for Sendmail, so I can't vouch.
Same with
this
postfix install. I expect users reading this install have better links than these, so check the
comments for more on those servers.

A cool tool to use to test if you have set up TLS correctly has been
provided by
the Kernel.org
people. To see what a good configuration looks like, see
here.

Note the 250 Starttls line. That means I'm ostensibly ready to trade
encrypted e-mail with other hosts. Life isn't perfect yet--I need to
implement SPF--but I feel much more secure in my e-mail.

Chris DiBona is the Co-Founder of
Damage Studios, a San
Francisco-based game company working on the next generation massively multiplayer
on-line game, Rekonstruction. He was formerly an editor for
Slashdot.org and was the
co-editor of Open Sources: Voices From the Open Source
Software Revolution.